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Novatel OEM Series Command and Log Reference User Manual
GPSCard™
Command Descriptions Manual
GPSCard™ Command Descriptions Manual Rev 3
1
GPSCard™
Command Descriptions Manual
Publication Number:
OM-20000008
Revision Level:
3
99/02/02
This manual reflects Software Version 3.36
This manual is a companion to the GPSCard Installation and Operating Manual.
Proprietary Notice
Information in this document is subject to change without notice and does not represent a commitment on the part of
NovAtel Inc. The software described in this document is furnished under a license agreement or non-disclosure
agreement. The software may be used or copied only in accordance with the terms of the agreement. It is against the law
to copy the software on any medium except as specifically allowed in the license or non-disclosure agreement.
No part of this manual may be reproduced or transmitted in any form or by any means, electronic or mechanical,
including photocopying and recording, for any purpose without the express written permission of a duly authorized
representative of NovAtel Inc.
The information contained within this manual is believed to be true and correct at the time of publication.
© 1999 NovAtel Inc. All rights reserved
Unpublished rights reserved under International copyright laws.
Printed in Canada on recycled paper.
2
GPSCard™ Command Descriptions Manual Rev 3
Table of Contents
TABLE OF CONTENTS
SOFTWARE LICENSE
10
SOFTWARE SUPPORT
11
FOREWORD
12
1
14
GPS SYSTEM OVERVIEW
GPS System Design..................................................................................................................................................14
The Space Segment ..................................................................................................................................................15
The Control Segment................................................................................................................................................15
The User Segment ....................................................................................................................................................15
2
COMMAND DESCRIPTIONS
17
General .....................................................................................................................................................................17
ACCEPT ..................................................................................................................................B and (R)...............20
ASSIGN ..............................................................................................................................................B...............21
UNASSIGN ..................................................................................................................................B...............22
UNASSIGNALL...........................................................................................................................B...............22
CLOCKADJUST ...............................................................................................................................Pf...............23
COMn
.................................................................................................................................................B...............23
COMn_DTR
.......................................................................................................................................B...............24
COMn_RTS ........................................................................................................................................B...............25
CRESET ..............................................................................................................................................B...............25
CSMOOTH .........................................................................................................................................B...............26
DATUM ..............................................................................................................................................B...............26
USERDATUM..............................................................................................................................B...............27
DGPSTIMEOUT
................................................................................................................................R...............27
DYNAMICS .......................................................................................................................................B...............28
ECUTOFF ...........................................................................................................................................B...............28
EXTERNALCLOCK ..........................................................................................................................B...............29
FIX HEIGHT ......................................................................................................................................B...............30
FIX POSITION ................................................................................................................... B (R) (RT20)...............30
FIX VELOCITY .................................................................................................................................B...............32
UNFIX ..........................................................................................................................................B...............32
FREQUENCY_OUT
...................................................................................................................Pf 51...............32
FRESET ...................................................................................................................................... O XII...............33
HELP
..................................................................................................................................................B...............34
LOCKOUT
.........................................................................................................................................B...............35
UNLOCKOUT..............................................................................................................................B...............36
GPSCard™ Command Descriptions Manual Rev 3
3
Table of Contents
UNLOCKOUTALL ......................................................................................................................B ...............36
LOG
....................................................................................................................................................B ...............36
UNLOG.........................................................................................................................................B ...............37
UNLOGALL .................................................................................................................................B ...............37
MAGVAR ...........................................................................................................................................B ...............37
MESSAGES ........................................................................................................................................B ...............39
POSAVE ................................................................................................................................................B ...............39
RESET
................................................................................................................................................O ...............40
................................................................................................................................. RT20 ...............40
RESETRT20
RTCM16T ...........................................................................................................................................R ...............40
RTCMRULE .......................................................................................................................................R ...............40
RTKMODE ................................................................................................................................... RT20 ...............40
SAVECONFIG
........................................................................................................................... O XII ...............42
SEND ..................................................................................................................................................B ...............42
SENDHEX ..........................................................................................................................................B ...............43
SETCHAN .......................................................................................................................................XII ...............43
SETDGPSID .......................................................................................................................................R ...............44
SETHEALTH ......................................................................................................................................B ...............44
RESETHEALTH...........................................................................................................................B ...............45
RESETHEALTHALL...................................................................................................................B ...............45
SETNAV .............................................................................................................................................B ...............45
UNDULATION
VERSION
3
..................................................................................................................................B ...............46
...........................................................................................................................................B ...............47
SPECIAL DATA INPUT COMMANDS ($xxxx)
48
Almanac Data...........................................................................................................................................................48
Protocols:..................................................................................................................................................................49
$ALMA.........................................................................................................................................B ...............49
$IONA...........................................................................................................................................B ...............49
$UTCA..........................................................................................................................................B ...............50
Differential Corrections Data ...................................................................................................................................50
Protocols:..................................................................................................................................................................50
$DCSA... .......................................................................................................................................R ...............50
$RTCA... (RTCAA) ......................................................................................................................R ...............50
$RTCM... (RTCMA).....................................................................................................................R ...............51
4
OUTPUT LOGGING
52
General .....................................................................................................................................................................52
5
NOVATEL FORMAT DATA LOGS
54
General .....................................................................................................................................................................54
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GPSCard™ Command Descriptions Manual Rev 3
Table of Contents
ASCII Log Structure ................................................................................................................................................54
Binary Log Structure ................................................................................................................................................54
GPS Time vs Local Receiver Time ..........................................................................................................................56
Log Descriptions ......................................................................................................................................................56
ALMA/B
Decoded Almanac ............................................................................................................B...............56
CDSA/B Communication and Differential Decode Status ...........................................................B (R)...............59
CLKA/B
Receiver Clock Offset Data ..............................................................................................B...............61
COM1A/B
Data Pass-Through COM1 port .....................................................................................B...............63
COM2A/B
Data Pass-Through COM2 port .....................................................................................B...............63
CONSOLEA/B
Channel Tracking Status
DCSA/B
Pseudorange Differential Corrections ............................................................................... R...............66
DOPA/B
Dilution of Precision .........................................................................................................B...............68
FRMA/B
Framed Raw Navigation Data .............................................................................................B...............70
FRWA/B
GGAB
...................................................................................................B...............63
Framed Raw Navigation Words ..........................................................................................B...............70
Global Position System Fix Data (Binary Format)
.........................................................B (R)...............72
MKPA/B
Mark Position ...................................................................................................................B...............72
MKTA/B
Time of Mark Input
NAVA/B
Waypoint Navigation Data ...............................................................................................B...............75
.........................................................................................................B...............74
P20A/B
Computed Position – Best Available ..................................................................B (R) (RT20)...............78
PAVA/B
Position Averaging Status ....................................................................................................B...............80
POSA/B
Computed Position ...............................................................................................................B...............82
PRTKA/B
Computed Position
RALA/B
RCCA
................................................................................................. (RTK)...............83
Computed Cartesian Coordinate Position ....................................................................B (R)...............85
PXYA/B
Raw Almanac ....................................................................................................................B...............87
Receiver Configuration .........................................................................................................B...............88
RCSA/B
Receiver Status ..................................................................................................................B...............88
REPA/B
Raw Ephemeris
RGEA/B/C/D
RT20A/B
6
Data Pass-Through Console port ............................................................................ B...............63
CTSA/B
.................................................................................................................B...............93
Channel Range Measurements .................................................................................51...............93
Computed Position – Time Matched
......................................................................... RT20...............98
RTCAA/B
Real Time Differential Corrections (Aviation)
RTCMA/B
Real Time Differential Corrections (Maritime) .............................................................R.............100
..............................................................R.............100
........................................................................... RTK.............100
RTKA/B
Computed Position - Time Matched
SATA/B
Satellite Specific Data ..................................................................................................B (R).............102
SPHA/B
Speed and Direction Over Ground
....................................................................................B.............104
..........................................B (R).............105
SVDA/B
SV Position in ECEF XYZ Coordinates with Corrections
TM1A/B
Time of 1PPS
VERA/B
Receiver Hardware and Software Version Numbers ...........................................................B.............110
VLHA/B
Velocity, Latency, and Direction over Ground
...................................................................................................................B.............109
SPECIAL PASS-THROUGH LOGS
GPSCard™ Command Descriptions Manual Rev 3
...........................................................B (R).............110
113
5
Table of Contents
Command Syntax ...................................................................................................................................................114
ASCII Log Structure...............................................................................................................................................115
Binary Log Structure ..............................................................................................................................................117
RTK........................................................................................................................................................................117
7
NMEA FORMAT DATA LOGS
118
General ...................................................................................................................................................................118
8
GPALM
Almanac Data ...................................................................................................................B .............119
GPGGA
Global Position System Fix Data ..................................................................................B (R) .............120
GPGLL
Geographic Position – Lat/Lon ...........................................................................................B .............121
GPGRS
GPS Range Residuals for Each Satellite .............................................................................B .............121
GPGSA
GPS DOP and Active Satellites ..........................................................................................B .............122
GPGST
Pseudorange Measurement Noise Statistics ........................................................................ B .............123
GPGSV
GPS Satellites in View .......................................................................................................B .............124
GPRMB
Navigation Information
GPRMC
GPS Specific Information ..................................................................................................B .............126
GPVTG
Track Made Good And Ground Speed
.....................................................................................................B .............125
..............................................................................B .............127
GPZDA
UTC Time and Date ...........................................................................................................B .............127
GPZTG
UTC & Time to Destination Waypoint
RTCM STANDARD COMMANDS AND LOGS
..............................................................................B .............128
129
RTCM General Message Format............................................................................................................................129
GPSCard Commands..............................................................................................................................................130
RTCMRULE .................................................................................................................................R .............130
RTCM16T .....................................................................................................................................R .............130
GPSCard Logs........................................................................................................................................................131
RTCM ...........................................................................................................................................R .............131
RTCMA ........................................................................................................................................R .............131
RTCMB.........................................................................................................................................R .............132
RTCM3 .........................................................................................................................................R .............132
RTCM16 .......................................................................................................................................R .............133
RTCM16T .....................................................................................................................................R .............133
RTCM59 ........................................................................................................................... RT20 (51) .............134
RTCM Receive Only Data .....................................................................................................................................134
RTCM Type 2 ...............................................................................................................................R .............134
RTCM Type 9 ...............................................................................................................................R .............134
9
RTCA STANDARD LOGS
135
GPSCard Logs........................................................................................................................................................135
RTCA ............................................................................................................................................R .............135
RTCAA .........................................................................................................................................R .............136
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GPSCard™ Command Descriptions Manual Rev 3
Table of Contents
RTCAB .........................................................................................................................................R.............136
10
PSEUDORANGE DIFFERENTIAL POSITIONING
137
GPS System Errors.................................................................................................................................................137
Dual Station Differential Positioning .....................................................................................................................138
The Reference Station ...................................................................................................................................139
The Remote Station.......................................................................................................................................140
The GPSCard and Differential Positioning ............................................................................................................141
Operating the GPSCard in Differential Modes.......................................................................................................141
Establish A Data Link ...................................................................................................................................142
Initialization – Reference Station ..................................................................................................................142
Options For Logging Differential Corrections ..............................................................................................143
Initialization – Remote Station......................................................................................................................145
11
RT-20 CARRIER PHASE MEASUREMENT SYSTEM
148
Introduction ............................................................................................................................................................148
RT-20 Overview.....................................................................................................................................................148
RT-20 Features Summary ......................................................................................................................................148
The RT-20 System .................................................................................................................................................149
Operating in RT-20 Mode ......................................................................................................................................149
Establish A Data Link ...................................................................................................................................149
Initialization – Reference Station ..................................................................................................................150
Initialization – Remote Station......................................................................................................................151
RT-20 Performance ................................................................................................................................................153
Steady State...................................................................................................................................................153
Performance Degradation..............................................................................................................................153
Notes on the use of rt-20 ........................................................................................................................................155
Performance Summary – Tables and Figures .........................................................................................................156
12
MULTIPATH ELIMINATION TECHNOLOGY
158
Multipath ................................................................................................................................................................158
Why Does Multipath Occur?.........................................................................................................................158
Consequences of Multipath Reception ..........................................................................................................159
Some Hardware Solutions For Multipath Reduction.....................................................................................160
NovAtel’s Internal Receiver Solutions For Multipath Reduction..................................................................162
Narrow Correlator Technology .....................................................................................................................163
MET Technology ..........................................................................................................................................164
MEDLL Technology .....................................................................................................................................164
GPSCard™ Command Descriptions Manual Rev 3
7
Table of Contents
Summary ................................................................................................................................................................165
INDEX
191
APPENDICES
A
Geodetic Datums .........................................................................................................................166
B
GPS Glossary of Terms ...............................................................................................................169
C
GPS Glossary of Acronyms.........................................................................................................175
D
Standards and References............................................................................................................178
E
Conversions .................................................................................................................................179
F
Command and Log Summary Charts...........................................................................................181
G
Summary of Status Tables...........................................................................................................187
TABLES
Table 2-1 GPSCard Command Summary ................................................................................................................. 18
Table 2-2 Typical Values of Clock Filters ................................................................................................................ 29
Table 4-1 GPSCard Log Summary............................................................................................................................ 53
Table 5-1 GPSCard Channel Tracking States.....................................................................................................65, 187
Table 5-2 GPSCard Solution Status ...................................................................................................................65, 187
Table 5-3 Position Type .....................................................................................................................................66, 187
Table 5-4 RTK Status for Position Type 3 (RT-20) ...........................................................................................66, 188
Table 5-5 GPSCard Receiver Self-test Status Codes..........................................................................................90, 188
Table 5-6 GPSCard Tracking Status ..................................................................................................................95, 189
Table 5-7 GPSCard Range Reject Codes .........................................................................................................103, 189
Table 5-8 GPSCard Velocity Status .................................................................................................................112, 190
Table 10-1 Summary of GPSCard Differential Corrections Formats...................................................................... 141
Table 10-2 GPSCard Pseudorange Differential Initialization Summary ................................................................. 146
Table 10-3 Latency-Induced Extrapolation Error..................................................................................................... 147
Table 11-1 RT-20 System Initialization Summary.................................................................................................. 152
Table 11-2 RT-20 Performance Specifications ....................................................................................................... 155
Table 11-3 RT-20 Convergence Summary.............................................................................................................. 156
Table A-1 Reference Ellipsoid Constants................................................................................................................ 166
Table A-2 Transformation Parameters (Local Geodetic to WGS-84) ..................................................................... 166
Table F-1 GPSCard Command Summary ............................................................................................................... 181
Table F-2 GPSCard Log Summary ......................................................................................................................... 182
Table F-3 Command/Log Relationships.................................................................................................................. 183
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GPSCard™ Command Descriptions Manual Rev 3
Table of Contents
FIGURES
Figure 1-1 NAVSTAR Satellite Orbit Arrangement ..................................................................................................14
Figure 1-2 GPS User Segment ................................................................................................... ................................16
Figure 2-1 Factory Default Settings ...........................................................................................................................19
Figure 2-2 HELP Command Screen Display ........................................................................................ .....................34
Figure 2-3 Appended Command Screen Display .................................................................................... ...................35
Figure 2-4 Illustration of Magnetic Variation & Correction ......................................................................................38
Figure 2-5 Using SEND Command................................................................................................. ...........................43
Figure 2-6 Illustration of SETNAV Parameters .........................................................................................................46
Figure 5-1 Example of Navigation Parameters ................................................................................... .......................77
Figure 5-2 Illustration of GPSCard Height Measurements.........................................................................................79
Figure 5-3 The WGS-84 ECEF Coordinate System.................................................................................. ...............108
Figure 6-1 Illustration of Pass-Through ...................................................................................................................113
Figure 6-2 Pass-Through Log Data .............................................................................................. ............................114
Figure 10-1 Typical Differential Configuration .......................................................................................................139
Figure 11-1 Illustration of RT-20 Steady State Performance ...................................................................................153
Figure 11-2 RT-20 Re-initialization Process............................................................................................................154
Figure 11-3 CEP Accuracy Over Cumulative Tracking Time..................................................................................156
Figure 11-4 CEP Accuracy Degradation with Increasing Baseline ..........................................................................157
Figure 11-5 Typical Example of Static Resolution Performance .............................................................................157
Figure 12-1 Illustration of GPS Signal Multipath ....................................................................................................158
Figure 12-2 Illustration of GPS Signal Multipath vs. Increased Antenna Height.....................................................160
Figure 12-3 Illustration of Quadrifilar vs. Microstrip Patch Antennae.....................................................................161
Figure 12-4 Example of GPSAntenna on a Flat Plate vs. Choke Ring Ground Plane ..............................................162
Figure 12-5 Comparison of Multipath Error Envelopes ...........................................................................................163
GPSCard™ Command Descriptions Manual Rev 3
9
Software License
SOFTWARE LICENSE
BY OPENING THE SEALED DISK PACKAGE, YOU ARE AGREEING TO BE BOUND BY THE TERMS OF THIS AGREEMENT. IF YOU
DO NOT AGREE TO THE TERMS OF THIS AGREEMENT, PROMPTLY RETURN THE UNOPENED DISK PACKAGE AND THE
ACCOMPANYING ITEMS TO NOVATEL INC.
1.
License: NovAtel Inc. (“NovAtel”) grants you a non-exclusive license (not a sale) to use one copy of the enclosed NovAtel software on a
single computer, and only with the product whose model number and serial number appear on the envelope.
2.
Copyright: NovAtel owns all copyright, trade secret, patent and other proprietary rights in the software and the software is protected by
national copyright laws, international treaty provisions and all other applicable national laws. You must treat the software l ike any other copyrighted
material except that you may either (a) make one copy of the software solely for backup or archival purposes, or (b) transfer t he software to a single
hard disk provided you keep the original solely for backup or archival purposes. You may not copy the product manual or writte n materials
accompanying the software.
3.
Restrictions: You may not: (1) copy (other than as provided for in paragraph 2), distribute, rent, lease or sublicense all o r any portion of the
software; (2) modify or prepare derivative works of the software; (3) use the software in connection with computer-based services business or
publicly display visual output of the software; (4) transmit the software over a network, by telephone or electronically using any means; or (5)
reverse engineer, decompile or disassemble the software. You agree to keep confidential and use your best efforts to prevent and protect the contents
of the software from unauthorized disclosure or use.
4.
Term and Termination: This Agreement is effective until terminated. You may terminate it at any time by destroying the software,
including all computer programs and documentation, and erasing any copies residing on computer equipment. If you do so, you should inform
NovAtel in writing immediately. This Agreement also will terminate if you do not comply with any of its terms or conditions. Upon such
termination you are obligated to destroy the software and erase all copies residing on computer equipment. NovAtel reserves the right to terminate
this Agreement for reason of misuse or abuse of this software.
5.
Warranty: For 90 days from the date of shipment, NovAtel warrants that the media (for example, diskette) on which the software is
contained will be free from defects in materials and workmanship. This warranty does not cover damage caused by improper use or neglect.
NovAtel does not warrant the contents of the software or that it will be error free. The software is furnished "AS IS" and without warranty as to the
performance or results you may obtain by using the software. The entire risk as to the results and performance of the software is assumed by you.
6.
For software UPDATES and UPGRADES, and regular customer support, contact the NovAtel GPS Hotline at 1-800-NOVATEL (Canada
and the U.S.A. only), or directly for International customers 1-403-295-4900, Fax 403-295-4901, e-mail to gps@novatel.ca, visit our world wide
web site at http://www.novatel.ca, or write to:
NovAtel Inc.
Customer Service
th
1120-68 Avenue NE
Calgary, Alberta, Canada
T2E 8S5
7.
Disclaimer of Warranty and Limitation of Liability:
a.
THE WARRANTIES IN THIS AGREEMENT REPLACE ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
ANY WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. NOVATEL DISCLAIMS AND
EXCLUDES ALL OTHER WARRANTIES. IN NO EVENT WILL NOVATEL'S LIABILITY OF ANY KIND INCLUDE ANY
SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, EVEN IF NOVATEL HAS
KNOWLEDGE OF THE POTENTIAL LOSS OR DAMAGE.
b.
NovAtel will not be liable for any loss or damage caused by delay in furnishing the software or any other performance under this
Agreement.
c.
NovAtel's entire liability and your exclusive remedies for our liability of any kind (including liability for negligence) for the software
covered by this Agreement and all other performance or nonperformance by NovAtel under or related to this Agreement are limited to
the remedies specified by this Agreement.
This Agreement is governed by the laws of the Province of Alberta, Canada. Each of the parties hereto irrevocably attorns to the
jurisdiction of the courts of the Province of Alberta.
10
GPSCard™ Command Descriptions Manual Rev 3
Software Support
SOFTWARE SUPPORT
SOFTWARE UPDATES AND UPGRADES
Software UPDATES are software revisions to an existing release which improves (but does not increase) basic
functionality of the receiver.
Software UPGRADES are software releases which increase basic functionality of the receiver from one model to a
higher-level model type.
Software UPDATES and UPGRADES are accomplished:
•
Via NovAtel Bulletin Board System (BBS) for 12 channel receivers.
•
By return to the factory only for 10 channel receivers.
•
Authorization coding supplied by NovAtel GPS Customer Service group.
Software UPDATES
Are supplied free of charge during the one-year warranty coverage following initial purchase. An updated manual is also
supplied free of charge.
Outside warranty:
•
are supplied free of charge for 12 channel receivers via the BBS. A nominal charge is applied for each copy of the
updated manual that is requested.
•
are supplied at a nominal charge for 10 channel receivers updated at the factory only. An updated manual is included
with the update.
Software UPGRADES
When available, UPGRADES may be purchased at a price, which is the difference between the two model types on the
current NovAtel GPS Price List, plus a nominal service charge.
UPGRADES are available via the BBS (12 channel receivers) or by return to the factory (10 channel receivers).
CUSTOMER SERVICE
For software UPDATES and UPGRADES, and regular customer support, contact the NovAtel GPS Hotline at
1-800-NOVATEL (Canada and the U.S.A. only), or directly for International customers 1-403-295-4900, Fax 403-2954901, e-mail to gps@novatel.ca, visit our world wide web site at http://www.novatel.ca, or write to:
NovAtel Inc.
Customer Service
1120-68th Avenue NE
Calgary, Alberta, Canada
T2E 8S5
GPSCard™ Command Descriptions Manual Rev 3
11
Foreword
FOREWORD
Purpose
The GPSCard™ Command Descriptions Manual is intended to be used as a companion manual to the GPSCard
Installation and Operating Manual. Once you have completed the initial installation and basic operating introductions,
this text will be your primary GPSCard command and logging reference source.
This manual has been written to be independent of the GPSCard model type and is therefore comprehensive including all
features of the top-of-the-line 12 channel models. Please bear in mind that if you do not own a top-of-the-line GPSCard,
some of the features described in this manual may not be available with your particular model of GPSCard.
Scope
The GPSCard Command Descriptions Manual describes each command and log that the GPSCard is capable of accepting
or outputting. Sufficient detail is provided so that a systems developer or OEM user can understand the purpose, syntax,
and structure of each command or log and be able to effectively communicate with the GPSCard, thus enabling the
developer to effectively use and write custom interfacing software for specific needs and applications. The manual is
organized into chapters that allow easy access to appropriate information about the GPSCard.
This manual does not address any of the GPSCard hardware attributes or installation information. Please consult the
companion to this volume, GPSCard Installation and Operating Manual, for hardware or system technical specification
information. Furthermore, should you encounter any functional, operational, or interfacing difficulties with the GPSCard,
consult the GPSCard Installation and Operating Manual for NovAtel warranty and customer support information.
Prerequisites
As this reference manual is focused on the GPSCard commands and logging protocol, it is necessary to ensure that the
GPSCard has been properly installed and powered up according to the instructions outlined in the Installation and
Operating Manual before proceeding.
To use the GPSCard effectively, you should be familiar with the Global Positioning System (GPS) as it applies to
positioning, navigation, and surveying applications. For your reference, Chapter 1 of this manual provides a brief
overview of the Global Positioning System.
As this manual covers the full performance capabilities of GPSCard 12 channel cards, your particular model of GPSCard
may not have some of the top-of-the-line features described in this text. Feature-tagging symbols have been created to
help clarify which commands and logs are basic features versus those that are optional features.
B
11
51
O
XII
R
Pf
RT20
12
Basic features available with all models of GPSCards (10 & 12 channel and Standard & Performance)
Features available with x11(R) or xx11(R) models
Features available with x51(R) or xx51(R) models
Features common only to OEM Series of GPSCards
Features available only with 12 channel GPSCards
Real time differential capability available only with xxxR and xxxxR model option
Features available only with Performance Series of GPSCards
Features available only with GPSCards equipped with the RT-20 option
GPSCard™ Command Descriptions Manual Rev 3
Foreword
WHAT’S NEW IN THIS EDITION
NEW COMMANDS
FRESET
Clears all data which is stored in non volatile memory
POSAVE
Implements position averaging for reference station
RTKMODE
Set-up the RTK mode
MODIFIED COMMANDS
UNLOGALL
Now includes option to disable all logs on a specified port only
NEW LOGS
FRM
Framed Raw Navigation Data
PAV
Positioning Averaging Status
PRTK
Computed Position
RTK
Computed Position – Time Matched
VER
Receiver Hardware and Software Version Numbers
FRW
Framed Raw Navigation Words
MODIFIED LOGS
RGEA/B/C
Now includes D messages -- Channel Range Measurements
GPSCard™ Command Descriptions Manual Rev 3
13
1 – GPS System Overview
1
GPS SYSTEM OVERVIEW
The Global Positioning System (GPS) is a satellite navigation system capable of providing a highly accurate, continuous
global navigation service independent of other positioning aids. GPS provides 24-hour, all-weather, worldwide coverage
with position, velocity and timing information.
The system uses the NAVSTAR (NAVigation Satellite Timing And Ranging) satellites, which consists of 24 operational
satellites to provide a GPS receiver with a six-to-twelve satellite coverage at all times. A minimum of four satellites in
view allows the GPSCard to compute its current latitude, longitude, and altitude with reference to mean sea level and the
GPS system time.
Figure 1-1 NAVSTAR Satellite Orbit Arrangement
GPS SYSTEM DESIGN
The GPS system design consists of three parts:
•
•
•
The Space segment
The Control segment
The User segment
All these parts operate together to provide accurate three-dimensional positioning, timing and velocity data to users
worldwide.
14
GPSCard™ Command Descriptions Manual Rev 3
1 – GPS System Overview
THE SPACE SEGMENT
The space segment is composed of the NAVSTAR GPS satellites. The final constellation of the system consists of 24
satellites in six 55° orbital planes, with four satellites in each plane. The orbit period of each satellite is approximately 12
hours at an altitude of 10,898 nautical miles. This provides a GPS receiver with six to twelve satellites in view from any
point on earth, at any particular time.
The GPS satellite signal identifies the satellite and provides the positioning, timing, ranging data, satellite status and the
corrected ephemerides (orbit parameters) of the satellite to the users. The satellites can be identified either by the Space
Vehicle Number (SVN) or the Pseudorandom Code Number (PRN). The NovAtel GPSCard uses the PRN.
The GPS satellites transmit on two L-band frequencies; one centered at 1575.42 MHz (L1) and the other at 1227.60 MHz
(L2). The C/A code (Coarse/Acquisition) and the P code (Precision), which are encrypted for military and other
authorized users, modulate the L1 carrier. The L2 carrier is modulated only with the P code.
THE CONTROL SEGMENT
The control segment consists of a master control station, five reference stations and three data up-loading stations.
Colorado Springs is the master control station and one of the five reference stations. Hawaii is another one of the
reference stations, and Ascension, Diego Garcia and Kwajalein are combined reference and up-loading stations.
The reference stations track and monitor the satellites via their broadcast signals. The broadcast signals contain the
ephemeris data of the satellites, the ranging signals, the clock data and the almanac data. These signals are passed to the
master control station where the ephemerides are re-computed. The resulting ephemerides corrections and timing
corrections are transmitted back to the satellites via the data up-loading stations.
THE USER SEGMENT
The user segment, such as the NovAtel GPSCard receiver, consists of equipment that tracks and receives the satellite
signals. The user equipment must be capable of simultaneously processing the signals from a minimum of four satellites
to obtain accurate position, velocity and timing measurements. A user can also use the data provided by the satellite
signals to accomplish specific application requirements. Please refer to Figure 1-2, page 16, for a graphical
representation of the user segment.
GPSCard™ Command Descriptions Manual Rev 3
15
1 – GPS System Overview
Figure 1-2 GPS User Segment
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2 – Command Descriptions
2
COMMAND DESCRIPTIONS
GENERAL
This chapter describes all commands accepted by the GPSCard with the exception of the "Special Data Input
Commands". They are listed in alphabetical order. For descriptions of output logs using the LOG command, refer to
Chapter 4, page 52. A command/log functional relationship chart is located in Appendix F, page 183.
The GPSCard is capable of responding to over 30 different input commands. You will find that once you become
familiar with these commands, the GPSCard offers a wide range in operational flexibility. All commands are accepted
through the Console, COM1 and COM2 serial ports. Not all commands or command options are available on all models.
Refer to Table 2-1, page 18, for a complete command listing.
There are five basic categories that the GPSCard commands and logs fall into:
•
•
•
•
•
NOTE:
General Status and Control
Position and Navigation
Input/Output Control
Satellite/Channel Control
Position Filter Control
You will find the HELP command a useful tool for inquiring about the various commands available.
The following rules apply when entering commands from a terminal keyboard:
•
The commands are not case sensitive.
e.g. HELP or help
e.g. FIX POSITION or fix position
•
All commands and required entries can be separated by a space or a comma.
e.g. datum,tokyo
e.g. datum tokyo
e.g. fix,position,51.3455323,-117.289534,1002
e.g. fix position 51.3455323 -117.289534 1002
e.g. com1,9600,n,8,1,n,off
e.g. com1 9600 n 8 1 n off
e.g. log,com1,posa,onchanged
e.g. log com1 posa onchanged
e.g. accept,com2,rtcm
e.g. accept com2 rtcm
•
At the end of a command or command string, press the Return key.
•
Most command entries do not provide a response to the entered command. Exceptions to this statement are
the VERSION and HELP commands. Otherwise, successful entry of a command is verified by receipt of the
COM port prompt (i.e., COM1>, COM2>, or Console>).
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2 – Command Descriptions
Table 2-1 GPSCard Command Summary
Command
Description
Syntax
$ALMA
$DCSA
$IONA
$RTCA
$RTCM
$UTCA
ACCEPT
Injects almanac
Injects NovAtel format differential corrections
Injects ionospheric refraction corrections
Injects RTCA format DGPS corrections in ASCII (Type 1)
Injects RTCM format differential corrections in ASCII (Type 1)
Injects UTC information
Port input control (set command interpreter)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
ASSIGN
Assign a PRN to a channel #
assign channel,prn,doppler, search window
Un-assign a channel
unassign channel
unassignall
UNASSIGN
accept port,option
UNASSIGNALL
CLOCKADJUST
Un-assign all channels
Adjust 1PPS continuously
COMn
Initialize Serial Port (1 or 2)
comn bps,parity,databits,stopbits,
handshake,echo
COMn_DTR
Programmable DTR lead/tail time
comn_dtr control,active,lead,tail
COMn_RTS
Programmable RTS lead/tail time
CRESET
CSMOOTH
Configuration reset to factory default
Sets carrier smoothing
comn_rts control,active,lead,tail
creset
DATUM
Choose a DATUM name type
datum option
User defined DATUM
userdatum semi-major,flattening,dx,dy,dz,
rx,ry,rz, scale
dgpstimeout value value
DYNAMICS
Sets maximum age of differential data to be accepted and ephemeris
delay
Set receiver dynamics
ECUTOFF
Set elevation cutoff angle
ecutoff angle
EXTERNALCLOCK
Sets default parameters of an optional external oscillator
externalclock option
FIX HEIGHT
Sets height for 2D navigation
fix height height
FIX POSITION
Set antenna coordinates for reference station
fix position lat,lon,height [station id] [health]
FIX VELOCITY
Accepts INS xyz (ECEF) input to aid in high velocity reacquisition of SVs
UNFIX
FREQUENCY_OUT
FRESET
fix velocity vx,vy,vz
unfix
HELP or ?
Remove all receiver FIX constraints
Variable frequency output (programmable)
Clears all data which is stored in non volatile memory, and performs
hardware reset
On-line command help
LOCKOUT
Lock out satellite
lockout prn
Restore satellite
unlockout prn
unlockoutall
USERDATUM
DGPSTIMEOUT
UNLOCKOUT
UNLOCKOUTALL
LOG
UNLOG
Restore all satellites
Choose data logging type
Kill a data log
UNLOGALL
MAGVAR
Kill all data logs
Set magnetic variation correction
MESSAGES
POSAVE
Disable error reporting from command interpreter
Implements position averaging for reference station
RESET
Performs a hardware reset (OEM only)
18
clockadjust switch
csmooth value
dynamics option
frequency_out n,k
freset
help option
or
? option
log port,datatype,trigger,[period,offset]
unlog port,data type
unlogall
magvar value
messages port,option
posave maxtime, maxhorstd, maxverstd
reset
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2 – Command Descriptions
Command
Description
Syntax
RESETRT20
RTCM16T
Performs a manual restart of RT20 mode
Enter an ASCII text message to be sent out in the RTCM data stream
resetrt20
RTCMRULE
Set variations of the RTCM bit rule
Set up the RTK mode
rtcmrule rule
rrtkmode argument, data range
Save current configuration in flash memory (OEM only)
Send an ASCII message to any of the communications ports
saveconfig
SENDHEX
Sends non-printable characters in hexadecimal pairs
sendhex port data
SETCHAN
Sets maximum number of channels for tracking
setchan option
SETDGPSID
Enter in a reference station ID
setdgpsid option
SETHEALTH
Override PRN health
sethealth prn,health
Reset PRN health
resethealth prn
resethealthall
RTKMODE
SAVECONFIG
SEND
RESETHEALTH
RESETHEALTHALL
SETNAV
Reset all PRN health
Set a destination waypoint
UNDULATION
Choose undulation
VERSION
Current software level
rtcm16t ascii message
send port ascii-message
setnav from lat,from lon,to lat, to lon,track
offset, from port,to port
undulation separation
version
NOTES:
1.
Commands are not case sensitive (e.g. help or HELP)
2.
All commands and required entries can be separated by a space or a comma
(command,variable or command variable).
3.
A command or command string must be followed by pressing the Return key (CR, LF).
4.
Also refer to the Command/Log Functional Relationship chart, page 183, in Appendix F.
When the GPSCard is first powered up, or after a CRESET or FRESET command, all commands will revert to the
factory default settings. The saveconfig command can be used to modify the power-on defaults. Use the RCCA log to
monitor command and log settings.
Figure 2-1 Factory Default Settings
console>log console rcca [Return]
$RCCA,COM1,9600,N,8,1,N,OFF*06
$RCCA,COM2,9600,N,8,1,N,OFF*05
$RCCA,COM1_DTR,HIGH*70
$RCCA,COM2_DTR,HIGH*73
$RCCA,COM1_RTS,HIGH*67
$RCCA,COM2_RTS,HIGH*64
$RCCA,UNDULATION,TABLE*56
$RCCA,DATUM,WGS84*15
$RCCA,USERDATUM,6378137.000,298.257223563,0.000,0.000,0.000,0.000,0.000,0.000,
0.000*6A
$RCCA,SETNAV,DISABLE*5C
$RCCA,MAGVAR,0.000*33
$RCCA,DYNAMICS,HIGH*1B
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2 – Command Descriptions
$RCCA,UNASSIGNALL*64
$RCCA,ACCEPT,COM1,COMMANDS*5B
$RCCA,ACCEPT,COM2,COMMANDS*58
$RCCA,UNLOCKOUTALL*20
$RCCA,RESETHEALTHALL*37
$RCCA,UNFIX*73
$RCCA,RTCMRULE,6CR*32
$RCCA,RTCM16T,*48
$RCCA,CSMOOTH,20.00*7E
$RCCA,ECUTOFF,0.00*45
$RCCA,FREQUENCY_OUT,DISABLE*12
$RCCA,CLOCKADJUST,ENABLE*47
$RCCA,MESSAGES,ALL,ON*23
$RCCA,SETCHAN,12*34
$RCCA,DGPSTIMEOUT,60,120*4E
$RCCA,SETDGPSID,ALL*18
$RCCA,UNLOGALL*21
B and (R)
ACCEPT
The ACCEPT command controls the processing of input data and is primarily used to set the GPSCard’s COM port
command interpreter for acceptance of various data formats. Each port can be controlled to allow ASCII command
processing (default), binary differential data processing, or the command interpreter can be turned off.
Syntax:
ACCEPT
Syntax
ACCEPT
port
Basic option
“R” option
RT-20 option
port
option
Range Value
COM1 or COM2
NONE
COMMANDS
NONE
COMMANDS
RTCA
RTCM
NONE
COMMANDS
RTCA
RTCM
RT20
Description
Command
Specifies the COM port to be controlled
Turn off Command Interpreter
Command Interpreter attempts to interpret all incoming data.
Turn off Command Interpreter.
Command Interpreter attempts to interpret all ASCII data Will also interpret
ASCII format differential corrections (DCSA, RTCAA, RTCMA) as received.
Interprets RTCA or RTCAB data only (Type 1)
Interprets RTCM data only (Types 1,2,9, and 16)
Same as “R” option
Same as “R” option
Same as “R” option
Same as “R” option
Interprets RTCM data only (RTCM types 1,2,3,9,16, and 59N)
Default
commands
Example:
accept com1,rtcm
The command interpreter can process NovAtel-format binary logs (which have a proprietary header) or ASCII logs
without receiving an ACCEPT command. Therefore, the ACCEPT command is needed only for the RTCA, RTCM,
and RT20 logs. When using accept RTCM or accept RT20, the interpretation of the RTCM data will follow the rules
defined by the RTCMRULE command (refer to the RTCMRULE command, page 40).
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2 – Command Descriptions
In the default processing mode (ACCEPT port COMMANDS), input ASCII data received by the specified port will be
interpreted and processed as a valid GPSCard command. If the input data cannot be interpreted as a valid GPSCard
command, an error message will be echoed from that port (if the command MESSAGES is “ON”). When valid data is
accepted and interpreted by the port, it will be processed and acknowledged by echoing the COM port prompt (with the
exception of VERSION and HELP commands, which reply with data before the prompt). As well, the accept
COMMANDS mode will directly accept, interpret, and process GPSCard differential corrections data formatted in ASCII
(DCSA, RTCMA, RTCAA), without any other initialization required. (“R” option required)
In the binary differential data processing modes, (RTCA, RTCM, and RT20), only the applicable data types specified will
be interpreted and processed by the specified COM port; no other data will be interpreted. It is important to note that
only one out of two COM ports can be specified to accept binary differential correction data. Both ports cannot be set to
accept differential data at the same time.
When ACCEPT port NONE is set, the specified port will be disabled from interpreting any input data. Therefore, the
specified port will decode no commands or differential corrections. However, data can still be logged out from the port,
and data can be input to the port for formatting into Pass-Through logs. If the GPSCard operator wants to time-tag nonGPS messages as a Pass-Through log, it is recommended that the port accepting the Pass-Through data be set to
“NONE”. This will prevent the accepting GPSCard COM port from echoing error messages in response to receipt of
unrecognized data. If you do not wish to disable the command interpreter, and do want to disable message error
reporting, refer to the MESSAGES command, page 39.
The ACCEPT command will not affect a COM port’s ability to accept Pass-Through data. Refer to Chapter 6, page 113,
for more information on using Pass-Through logs.
The GPSCard user can monitor the differential data link as well as the data decoding process by utilizing the CDSA/B
logs. Refer to the CDSA/B log, page 59, for more information on data link monitoring.
NOTE: To accept DCSB, RTCA, RTCM requires the “R” option. To accept RT20 requires the “RT-20” option.
ASSIGN
B
This command may be used to aid in the initial acquisition of a satellite by allowing you to override the automatic
satellite/channel assignment and reacquisition processes with manual instructions. The command specifies that the
indicated tracking channel search for a specified satellite at a specified Doppler frequency within a specified Doppler
window. The instruction will remain in effect for the specified channel and PRN, even if the assigned satellite
subsequently sets. If the satellite Doppler offset of the assigned channel exceeds that specified by the Search-Window
parameter of the ASSIGN command, the satellite may never be acquired or re-acquired. To cancel the effects of
ASSIGN, you must issue the UNASSIGN or UNASSIGNALL command, or reboot the GPSCard.
When using this command, NovAtel recommends that you monitor the channel tracking status (CTSA/B) of the assigned
channel and then use the UNASSIGN or UNASSIGNALL commands to cancel the command once the channel has
reached channel state 4, the Phase Lock Loop (PLL) state. Refer to Table 5-1, page 65, in the CTSA/B ASCII Log
Structure for an explanation of the various channel states.
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2 – Command Descriptions
Syntax:
channel
ASSIGN
Syntax
ASSIGN
channel
Range Value
0 - 11
prn
doppler
1 - 32
-100,000 to
100,000 Hz
search-window
0 - 10,000
prn
doppler
search-window
Description
Command
Desired channel number from 0 to 11 inclusive (channel 0 represents first
channel, channel 11 represents twelfth channel)
A satellite PRN integer number from 1 to 32 inclusive
Current Doppler offset of the satellite
Note: Satellite motion, receiver antenna motion and receiver clock
frequency error must be included in the calculation for Doppler frequency.
Error or uncertainty in the Doppler estimate above in Hz
Note: Any positive value from 0 to 10000 will be accepted. Example: 500
implies ± 500 Hz.
Default
unassignall
Example
assign
0
29
0
2000
Example 1:
assign 0,29,0,2000
In example 1, the first channel will try to acquire satellite PRN 29 in a range from -2000 Hz to 2000 Hz until the satellite
signal has been detected.
Example 2:
assign 11,28,-250,0
The twelfth channel will try to acquire satellite PRN 28 at -250 Hz only.
B
UNASSIGN
This command cancels a previously issued ASSIGN command and the channel reverts to automatic control. If a channel
has reached state 4 (PLL), the satellite being tracked will not be dropped when the UNASSIGN command is issued,
unless it is below the elevation cutoff angle, and there are healthy satellites above the ecutoff that are not already assigned
to other channels.
Syntax:
UNASSIGN
Syntax
UNASSIGN
channel
channel
Range Value
0 - 11
Description
Command
Reset channel to automatic search and acquisition mode
Default
unassignall
Example:
unassign 11
UNASSIGNALL
B
This command cancels all previously issued ASSIGN commands for all channels. Tracking and control for each channel
reverts to automatic mode. If any of the channels have reached state 4 (PLL), the satellites being tracked will not be
dropped when the UNASSIGNALL command is issued, unless they are below the elevation cutoff angle, and there are
healthy satellites above the ecutoff that are not already assigned to other channels.
Syntax:
UNASSIGNALL
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2 – Command Descriptions
Pf
CLOCKADJUST
All oscillators have some inherent drift characterization. This command enables the software to model out these longterm drift characteristics of the clock. The correction is applied to the 1PPS strobe as well. The clock adjustment is
performed digitally. As a result, the 1PPS Strobe will have a 49ns jitter on it due to the receiver’s attempts to keep it as
close as possible to GPS time. If this jitter is unacceptable to the application, the user must disable this option before the
clock model is initialized, i.e., in the first 30 seconds of operation after power-up.
CLOCKADJUST must also be disabled if the user wishes to measure the drift rate of the oscillator using the CLKA/B
data logs.
NOTE: Do not disable clockadjust after 30 seconds from power-up as unpredictable clock drifts may result. Please note
that, when disabled, the range measurement bias errors will continue to accumulate with clock drift.
Syntax:
CLOCKADJUST
Syntax
CLOCKADJUST
switch
switch
Range Value
enable or disable
Description
Command
Allows or disallows adjustment to the internal clock
Default
enable
Example:
clockadjust disable
B
COMn
This command permits you to configure the GPSCard COM port’s asynchronous drivers.
Syntax:
COMn
Syntax
COMn
BPS
parity
databits
stopbits
handshake
echo
bps
parity databits
stopbits
Value
n = 1 or 2
300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600 or 115,200
N (none), O (odd) or E (even)
7 or 8
1 or 2
N (none), XON (Xon/Xoff) or CTS (CTS/RTS)
ON or OFF
handshake echo
Description
Specify COM port
Specify bit rate
Specify parity
Specify number of data bits
Specify number of stop bits
Specify handshaking
Specify echo
Default
9600
N
8
1
N
OFF
Example
com2
19200
E
7
1
N
ON
Examples:
com2 19200,e,7,1,n,on
com1 1200,e,8,1,n,on
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2 – Command Descriptions
B
COMn_DTR
This command enables versatile control of the DTR handshake line for use with output data logging in conjunction with
external devices such as a radio transmitter. The default state for the COM1 or COM2 DTR line is always high.
Syntax:
COMn_DTR
Syntax
COMn_DTR
control
(active, lead, and
tail fields are
TOGGLE options
only)
active
lead
tail
COMn_DTR
control
active lead
tail
Option
n = 1 or 2
high
low
toggle
Description
Selects COM1 or COM2 port
control is always high
control is always low
control toggles between high and low
Default
high
Example
com1_dtr
toggle
high
low
variable
variable
data available during high
data available during low
lead time before data transmission (milliseconds)
tail time after data transmission (milliseconds)
n/a
high
n/a
n/a
300
150
Control State
high
low
toggle
Active
N/A
N/A
high/low
Lead
N/A
N/A
0 - 999
Tail
N/A
N/A
0 - 999
Example:
com1_dtr toggle,high,300,150
DATA
XXXXXXXXXXXXXXXXXXXXXX
OUTPUT DATA
DTR
300ms
150ms
lead
tail
control
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2 – Command Descriptions
B
COMn_RTS
This command enables versatile control of the RTS handshake line for use with output data logging in conjunction with
external devices such as a radio transmitter. The default state for the COM1 or COM2 RTS line is always high.
COMn_RTS will not influence the COMn command handshake control of incoming commands.
Syntax:
COMn_RTS
Syntax
COMn_RTS
control
(active, lead, and
tail fields are
TOGGLE options
only)
active
lead
tail
COMn_RTS
control
active
lead
tail
Option
n = 1 or 2
high
low
toggle
Description
Selects COM1 or COM2 port
control is always high
control is always low
control toggles between high and low
Default
high
Example
com1_rts
toggle
high
low
variable
variable
data available during high
data available during low
lead time before data transmission (milliseconds)
tail time after data transmission (milliseconds)
n/a
high
n/a
n/a
200
100
Control State
high
low
toggle
Active
N/A
N/A
high/low
Lead
N/A
N/A
0 - 999
Tail
N/A
N/A
0 - 999
Example:
com1_rts toggle,high,200,100
DATA
XXXXXXXXXXXXXXXXXXXXXX
OUTPUT DATA
RTS
200ms
100ms
lead
tail
control
B
CRESET
This command completely resets the GPSCard user configurable settings to a factory default state. All data logging is
disabled and all the ports are restored to the default power up status. Refer to Command Default Settings, page 19.
Syntax:
CRESET
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2 – Command Descriptions
B
CSMOOTH
This command sets the amount of carrier smoothing to be performed on the pseudorange measurements carrier. An input
value of 100 corresponds to approximately 100 seconds of smoothing. Upon issuing the command, the locktime for all
tracking satellites is reset to zero. From this point each pseudorange smoothing filter is restarted. The user must wait for
at least the length of smoothing time for the new smoothing constant to take full effect. 20 seconds is the default
smoothing constant used in the GPSCard. The optimum setting for this command is dependent on the user’s application
and thus cannot be specified.
Syntax:
value
CSMOOTH
Syntax
CSMOOTH
value
Range Value
20 to 1000
Description
Command
Value in seconds
Default
20
Example:
csmooth 500
NOTE: The CSMOOTH command should only be used by advanced users of GPS. It may not be suitable for every
GPS application. When using CSMOOTH in a differential mode, the same setting should be used at both the reference
and remote station.
B
DATUM
This command permits you to select the geodetic datum for operation of the receiver. If not set, the value is defaulted to
WGS-84. See Table A-2, page 166, in Appendix A, for a complete listing of all available predefined datums. Refer to the
USERDATUM command, page 27, for user definable datums. The datum you select will cause all position solutions to
be based on that datum (except PXYA/B, which is always based on WGS-84).
Syntax:
DATUM
Syntax
DATUM
option
Datum Option
any one of 62 predefined
datums
USER
Description
For a complete list of all 62 predefined datums, see Table A-2, page 166, in
Appendix A.
User defined datum with parameters specified by the USERDATUM command
(Default WGS-84)
Default
WGS84
Example:
datum tokyo
Sets the system datum to Tokyo
Note that the actual datum name must be entered in this command as listed in the NAME column of Table A-2, page 166.
Also note that references to datum in the following logs use the GPSCard Datum ID #: MKPA/B, P20A/B, POSA/B and
RT20A/B.
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B
USERDATUM
This command permits entry of customized ellipsoidal datum parameters. Use this command in conjunction with the
DATUM command. The default setting is WGS-84.
Syntax:
USERDATUM semi-major
Syntax
USERDATUM
semi-major
Range Value
min.
6300000.0
max.
6400000.0
min.
290.0
max.
305.0
min.
- 2000.0
max.
2000.0
flattening
dx,dy,dz
rx,ry,rz
min.
max.
min.
max.
scale
-10
10
-10
10
flattening
dx
dy
dz
rx
ry
rz
scale
Description
Command
Datum Semi-major Axis (a) in metres
Default
6378137.000
Example
userdatum
6378206.4
Reciprocal Flattening, 1/f = a/(a-b)
298.257223563
294.9786982
Datum offsets from WGS-84 in metres:
These will be the translation values between your datum and WGS-84
(internal reference)
Datum Rotation Angle about X, Y and Z axis (sec of arc):
These values will be the rotation between your datum and WGS-84
Scale value is the difference in ppm between your datum and WGS-84
0.000,0.000,0.000
-12,147,192
0.000,0.000,0.000
0,0,0
0.000
0
Example:
userdatum 6378206.4,294.9786982,-12,147,192,0,0,0,0
R
DGPSTIMEOUT
This command has a two-fold function:
(1)
to set the maximum age of differential data that will be accepted when operating as a remote station.
Differential data received that is older than the specified time will be ignored. When entering DGPS delay, you
can ignore the ephemeris delay field.
(2)
to set the ephemeris delay when operating as a reference station. The ephemeris delay sets a time value by
which the reference station will continue to use the old ephemeris data. A delay of 120 to 300 seconds will
typically ensure that the remote stations have collected updated ephemeris. After the delay period is passed, the
reference station will begin using new ephemeris data. To enter an ephemeris delay value, you must first enter a
numeric placeholder in the DGPS delay field (e.g., 2). When operating as a reference station, DGPS delay will
be ignored.
Syntax:
DGPSTIMEOUT
Command
DGPSTIMEOUT
dgps delay
ephem delay
Option
min.
max.
min.
max.
2
1000
0
600
dgps delay
ephem delay
Description
Command
Maximum age in seconds
Default
Minimum time delay in seconds
120
Example 1 (remote):
dgpstimeout 15
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60
Example 2 (base):
dgpstimeout 2,300
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2 – Command Descriptions
NOTES: The RTCA Standard for SCAT-I stipulates that the maximum age of differential correction messages cannot be
greater than 22 seconds. Therefore, for RTCA logs, the recommended dgps delay setting is 22.
The RTCA Standard also stipulates that a reference station shall wait five minutes after receiving a new ephemeris before
transmitting differential corrections. This time interval ensures that the remote stations will have received the new
ephemeris, and will compute differential positioning based upon the same ephemeris. Therefore, for RTCA logs, the
recommended ephemeris delay is 300 seconds.
B
DYNAMICS
This command sets the carrier tracking bandwidth of the receiver.
Syntax:
DYNAMICS
Command
DYNAMICS
option
Option
stationary
low
medium
high
Description
2.5 Hz bandwidth, where jerk < 0.001 g/s
5 Hz bandwidth, where jerk < 0.1 g/s
10 Hz bandwidth, where jerk < 1.0 g/s
15 Hz bandwidth, where jerk < 4.5 g/s
Default
high
Example:
dynamics medium
CAUTION: The user is cautioned against using any setting except high on GPSCard models using the standard tcxo
oscillator. If a lower setting is used, frequent loss of phase lock may occur regardless of the user’s dynamics. This
command is intended to support use of external high-stability reference oscillators.
B
ECUTOFF
This command sets the elevation cut-off angle for usable satellites. Satellites that are below this angle will be eliminated
from the internal position and clock offset solution computations only. It does not affect the satellite tracking system or
data logging. All satellites in view will still be tracked, their data logged, and this data may be used in post processing.
If there are more satellites in view than there are channels available, the channels which are tracking satellites below the
elevation cut-off will be reassigned to any healthy satellites above the ecutoff which are not already assigned to a channel.
Syntax:
ECUTOFF
Syntax
ECUTOFF
angle
angle
Range Value
0 to 90 degrees
Description
Command
Value in degrees (above the horizon)
Default
0
Example:
ecutoff 5.5
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2 – Command Descriptions
NOTE: When ecutoff is set to zero (0), the receiver will track all svs in view including some within a few degrees below
the horizon.
B
EXTERNALCLOCK
This command allows the user to set a GPSCard (GPSTN and GPSTNM models only) to operate with an alternate
oscillator. An unsteered oscillator can be approximated by a three-state clock model, with two states representing the
range bias and range bias rate, and a third state assumed to be a Gauss-Markov process representing the range bias error
generated from satellite clock dither. The third state is included because the Kalman filter assumes an (unmodelled)
white input error. The significant correlated errors produced by SV clock dither are obviously not white and the Markov
process is an attempt to handle this kind of short-term variation.
The user has control over 3 process noise elements of the linear portion of the clock model. These are the h0, h-1, and h-2
elements of the power law spectral density model used to describe the noise characteristics of oscillators:
Sy ( f ) =
where
h−2 h−1
+
+ h0 + h1 f + h2 f 2
f2
f
f is the sampling frequency and Sy ( f ) is the clock’s power spectrum. Typically only h0, h-1, and h-2 affect the
clock Allan variance and the clock model process noise elements. Typical values are shown in Table 2-2 Typical Values
of Clock Filters.
Syntax:
EXTERNALCLOCK
Command
EXTERNALCLOCK
Option
DISABLE
OCXO
RUBIDIUM
CESIUM
USER,h0,h-1,h-2
option
Description
Revert to TCXO
Set defaults for ovenized crystal oscillator
Set defaults for rubidium oscillator
Set defaults for cesium oscillator
Define custom values for process noise elements
Default
see Table 2-2, page29
Example:
externalclock,user,1.0e-20,1.0e-24,1.0e-28
Table 2-2 Typical Values of Clock Filters
Timing Standard
Specified TCXO
Crystal
Ovenized Crystal (OCXO)
Rubidium
Cesium
User minimum
User maximum
h0
1.0e-21
2.0e-19
2.51e-26
1.0e-23
8.0e-21
1.0e-31
1.0e-18
GPSCard™ Command Descriptions Manual Rev 3
h-1
1.0e-20
7.0e-21
2.51e-24
1.0e-22
2.59e-21
1.0e-31
1.0e-18
h-2
1.0e-20
2e-20
2.51e-23
1.3e-26
7.0e-32
1.0e-31
1.0e-18
29
2 – Command Descriptions
B
FIX HEIGHT
This command configures the GPSCard in 2D mode with its height constrained to a given value. The command would be
used mainly in marine applications where height in relation to mean sea level may be considered to be approximately
constant. The height entered using this command is always referenced to the geoid (mean sea level) and uses units of
metres. The FIX HEIGHT command will override any previous FIX HEIGHT or FIX POSITION command and
disables the output of differential corrections. The receiver is capable of receiving and applying differential corrections
from a reference station while FIX HEIGHT is in effect. Use the UNFIX command to disable the current FIX command.
No special solution status is reported in the POSA/B or PRTKA/B logs for a 2 dimensional solution. This mode is detected by the
standard deviation of the height being 0.001m.
Syntax:
FIX HEIGHT
Syntax
FIX HEIGHT
height
height
Range Value
-1,000.0 to 20,000,000.0
Description
Command
Height in metres above mean sea level
Default
unfix
Example:
fix height 4.567
REMEMBER: Any error in the height estimate will cause an error in the position computed of the same order of
magnitude or higher. For example, if the user fixed height to zero and the antenna was installed on a 20 m mast, the
position can be expected to be in error by 10 to 60 m, depending on the geometry of the satellites. This command should
only be used when absolutely necessary, i.e., when only three satellites are visible.
When FIX HEIGHT has been properly set, the GPSCard will provide position solutions while tracking only three
satellites. If FIX HEIGHT is set to UNFIX, the GPSCard must be tracking four good satellites before position solutions
will be produced.
FIX POSITION
B (R) (RT20)
Invoking this command will result in the GPSCard position being held fixed. A computation will be done to solve local
clock offset, pseudorange, and pseudorange differential corrections (with R or RT20 option). This mode of operation can
be used for time transfer applications where the position is fixed and accurate GPS time output is required (refer to the
logs CLKA/B, page 61, and TM1A/B, page 109, for time data).
As well, this command must be properly initialized before the GPSCard can operate as a GPS pseudorange reference
station. Once initialized, the receiver will compute pseudorange differential corrections for each satellite being tracked.
The computed differential corrections can then be output to remote stations by utilizing any of the following GPSCard
differential corrections data log formats: RTCM, RTCMA, RTCMB, RTCA, RTCAA, RTCAB, DCSA, or DCSB. The
reference station servicing RT-20 remote receivers must log RTCM3 and RTCM59(N) pseudorange and carrier phase
observation data in order for the RT-20 remote receiver to compute double difference carrier phase solutions.
The values entered into the FIX POSITION command should reflect the precise position of the reference station antenna’s
phase centre. Any errors in the FIX POSITION coordinates will directly bias the pseudorange corrections that are
calculated by the reference receiver.
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2 – Command Descriptions
The GPSCard performs all internal computations based on WGS-84 and the datum command is defaulted as such. The
datum in which you choose to operate (by changing the DATUM command) will internally be converted to and from
WGS-84. Therefore, all differential corrections are based on WGS-84, regardless of your operating datum.
The GPSCard will begin logging differential data while tracking as few as three healthy satellites. Refer to Chapter 10,
page 137, for further discussions on differential positioning.
The FIX POSITION command will override any previous FIX HEIGHT or FIX POSITION command settings. Use the
UNFIX command to disable the FIX POSITION setting.
Syntax:
FIX POSITION
Syntax
FIX POSITION
lat
lat
lon
height
Range Value
0 to ± 90.0
(up to 7 decimal places allowed, depending on
accuracy required)
lon
0 to ± 360.0
(up to 7 decimal places allowed, depending on
accuracy required)
height
-1,000 to 20,000,000
station id
0 to 1023 (10 bits) for RTCM or DCSA/B output
“xxxx” for RTCA output where “xxxx” are four
alphanumeric characters, entered between double
quotes
RTCM reference
station health
0 – 7 where 0 – 5 Specified by user
6
Reference station transmission not
monitored
7
Reference station not working
station id
RTCM stn health
Description
Command
Latitude (in degrees/decimal degrees) of
fixed reference station antenna in current
datum. A negative sign implies South
latitude.
Longitude (in degrees) of fixed reference
station antenna in current datum. A
negative sign implies West longitude.
Height (in metres) above the geoid of
reference station in current datum.
Specify a Reference Station identification
number (optional entry) (See SETDGPSID,
page 44
Default
unfix
Specify RTCM reference station health
(optional) (This field will only be reported in
RTCM message header – word 2.)
6
Example
fix position
51.3455323
-114.289534
1201.123
1002
0
Example:
fix position 51.3455323,-114.289534,1201.123,1002,0
The above example configures the receiver as a reference station with fixed coordinates of:
Latitude
Longitude
Height above sea level
Station ID
RTCM health
N 51° 20' 43.9163" (WGS-84 or local datum)
W 114° 17' 22.3224"
1201.123 m
1002
0
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2 – Command Descriptions
B
FIX VELOCITY
This command supports INS (Inertial Navigation System) integration. It accepts ECEF XYZ velocity values in units of
m/s. This information is only used by the tracking loops of the receiver to aid in reacquisition of satellites after loss of
lock; otherwise it is ignored. It is not used in the position solution and velocity calculations. This command is only
useful for very high dynamics where expected velocity changes during the signal blockage of more than 100 m/s can
occur. Refer to Figure 5-3, page 108, for ECEF definitions. The UNFIX command is used to clear the effects of the FIX
VELOCITY command. The FIX VELOCITY command will override any previous FIX HEIGHT or FIX POSITION
command. Use the UNFIX command to disable the current FIX command.
Syntax:
FIX VELOCITY
Syntax
FIX VELOCITY
vx
vy
vz
vx
Range Value
± 999.99
± 999.99
± 999.99
vy
vz
Description
Command
X = Antenna Velocity (ECEF) in the X direction [m/s].
Y = Antenna Velocity (ECEF) in the Y direction [m/s].
Z = Antenna Velocity (ECEF) in the Z direction [m/s].
Default
unfix
Example
fix velocity
315
212
150
Example:
fix velocity 315,212,150
B
UNFIX
This command removes all position constraints invoked with any of the FIX commands (FIX POSITION, FIX HEIGHT,
or FIX VELOCITY).
Syntax:
UNFIX
Pf 51
FREQUENCY_OUT
This command allows you to specify the frequency of the output pulse at the VARF pin of the I/O strobe connector. The
frequency in Hz is calculated according to the formula below. The time between pulses may have up to 49 ns jitter
variation from the true frequency pulse.
20473000
[ 20473000 - (n+1) ]
FREQUENCY_OUT =
(k+1)
Syntax:
k
n
frequency_out
OR
frequency_out
Syntax
FREQUENCY_OUT
n
k
32
disable
Range Value
1 to 65535
1 to 65535
Description
Command
Variable integer
Variable integer
Default
disable
Example
frequency_out
1
65535
GPSCard™ Command Descriptions Manual Rev 3
2 – Command Descriptions
Example 1:
frequency_out 1,65535
n=1, k=65535 results in an output pulse frequency of 156.196594 Hz
Example 2:
frequency_out 65535,1
n=65535, k=1 results in an output pulse frequency of 10,236,343.8034 Hz
As a reference, some n and k selections and their corresponding frequency outputs are listed in the following table:
n
1
65535
20472
1569
346
74
58
1
1
65535
k
Frequency_Out (Hz)
65535
65535
20471
2045
345
201
57
9
1
1
156.1966
312.3884
1 000.0000
9 999.9804
59 000.0000
100 000.1320
347 000.0000
1 023 650.0000
5 118 250.0000
10 236 343.8034
(Minimum)
(Maximum)
If the 49 ns jitter is not suitable for your application, the following formula may be used to eliminate the jitter.
FREQUENCY_OUT =
where:
20473000
(k+1)
N is constrained to 0, and K = 1 to 65535
NOTE: Frequency resolution of this method is not as fine as original formula but provides jitter-free pulses.
O XII
FRESET
This command clears all data that is stored in non-volatile memory. Such data includes the almanac, satellite channel
configuration, and any user-specific configurations. It is only available on 12-channel OEM cards with the
SAVECONFIG option. The GPSCard is forced to reset and will start up with factory defaults.
See also the commands CRESET, page 25, and RESET, page 40.
Syntax:
FRESET
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2 – Command Descriptions
B
HELP
This command provides you with on-line help. The command, with no options, gives a complete list of the valid system
commands. For detailed help on any command, append the optional command name to the HELP command.
Syntax:
HELP
option
OR:
? option
Syntax
HELP (or ?)
option
Range Value
Refer to Figure 2-2, page 34
Description
Entering HELP without an option will list all valid command options.
Can be any valid system command. Information about the command entered will be displayed.
Example:
help dynamics
Figure 2-2 shows the screen display of the HELP command and Figure 2-3 shows a specific example of the RTKMODE
command appended to the HELP command.
Figure 2-2 HELP Command Screen Display
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2 – Command Descriptions
Figure 2-3 Appended Command Screen Display
B
LOCKOUT
This command will prevent the GPSCard from using a satellite by de-weighting its range in the solution computations.
Note that the LOCKOUT command does not prevent the GPSCard from tracking an undesirable satellite. This command
must be repeated for each satellite to be locked out.
Syntax:
LOCKOUT
Syntax
LOCKOUT
prn
prn
Range Value
1 - 32
Description
Command
A single satellite PRN integer number to be locked out
Default
unlockoutall
Example:
lockout 8
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2 – Command Descriptions
B
UNLOCKOUT
This command allows a satellite that has been previously locked out (LOCKOUT command) to be reinstated in the
solution computation. If more than one satellite is to be reinstated, this command must be reissued for each satellite
reinstatement.
Syntax:
UNLOCKOUT prn
Syntax
UNLOCKOUT
prn
Range Value
1 - 32
Description
Command
A single satellite PRN to be reinstated
Default
unlockoutall
Example:
unlockout 8
B
UNLOCKOUTALL
This command allows all satellites that have been previously locked out (LOCKOUT command) to be reinstated in the
solution computation.
Syntax:
UNLOCKOUTALL
B
LOG
Many different types of data can be logged using several different methods of triggering the log events. Every log
element can be directed to either the console, COM1 or COM2 ports. If a selected log element is to be directed to all the
ports, then separate LOG commands are required to control them. The ONTIME trigger option requires the addition of
the period parameter and optionally allows input of the offset parameter. See Chapter 5, page 54, for further information
and a complete list of ASCII and Binary data log structures.
Syntax:
LOG port
datatype
trigger
[period] [offset]
Example:
log com1,posa,ontime,60,1
The previous example will cause the POSA log to be logged to COM port 1, recurring every 60 seconds, and offset by 1
second. To send a log only one time, the trigger option can be ignored.
Example:
log com1 posa
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2 – Command Descriptions
B
UNLOG
This command permits you to remove a specific log request from the system.
Syntax:
UNLOG
Syntax
UNLOG
port
log name
port
log name
Range Value
COM1, COM2 or console
any valid log
Description
Command
COMn port from which log originated
The name of the log to be disabled
Default
unlogall
Example:
unlog com1,posa
B
UNLOGALL
If [port] is specified (COM1 or COM2) this command disables all logs on the specified port only. All other ports are
unaffected. If [port] is not specified, this command disables all logs on all ports.
Syntax:
UNLOGALL [port]
B
MAGVAR
The GPSCard computes directions referenced to True North. Use this command (magnetic variation correction) if you
intend to navigate in agreement with magnetic compass bearings. The correction value entered here will cause the
"bearing" field of the NAVA/B and GPVTG logs to report bearing in degrees magnetic. The magnetic variation
correction is also reported in the GPRMC log.
Syntax:
MAGVAR correction
Syntax
MAGVAR
correction
Range Value
± 0 - 180
Description
Command
The magnetic variation correction for the area of navigation in units of degrees.
Magnetic bearing = true bearing + magnetic variation correction. See Figure 2-4,
page 38.
Default
0.000
Example:
magvar +15.0
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37
2 – Command Descriptions
Figure 2-4 Illustration of Magnetic Variation & Correction
True
North
Local
Magnetic
North
15 W
(-15 )
b
+15
c
0
315
50
a
45
90
270
135
225
a = True bearing
b = Local magnetic variation
c = Local magnetic variation correction
(inverse of magnetic variation)
180
a + c = Magnetic bearing
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2 – Command Descriptions
B
MESSAGES
The MESSAGES command is used to disable the port prompt and error message reporting from a specified port. This
feature can be useful if the port is connected to a modem or other device that responds with data the GPSCard does not
recognize. Refer to Chapter 6, page 113, for further information on using this command with Special Pass-Through Logs.
Syntax:
MESSAGES
Syntax
MESSAGES
port
option
option
port
Range Value
COM1, COM2, console, or all
ON or OFF
Description
Command
Specifies the port being controlled
Enable or disable port prompt and error message reporting
Default
MESSAGES
ON
Example:
messages com1,off
B
POSAVE
This command implements position averaging for reference stations. Position averaging will continue for a specified
number of hours or until the averaged position is within specified accuracy limits. Averaging will stop when the time
limit or the horizontal standard deviation limit or the vertical standard deviation limit is achieved. When averaging is
complete, the fix position command will automatically be invoked.
If the maximum time is set to 1 hour or larger, positions will be averaged every 10 minutes and the standard deviations
reported in the PAVA/B log should be correct. If the maximum time is set to less than 1 hour, positions will be averaged
once per minute and the standard deviations reported in the log will likely not be accurate; also, the optional horizontal
and vertical standard deviation limits cannot be used.
One could initiate differential logging, then issue the posave command followed by the SAVECONFIG command. This
will cause the GPSCard to average positions after every power-on or reset, then invoke the fix position command to
enable it to send differential corrections.
Syntax:
POSAVE
Command
POSAVE
maxtime
mashorstd
maxverstd
maxtime
Range Values
0.025 - 100
0.1 - 100
0.1 - 100
maxhorstd
maxverstd
Description
Command
Maximum amount of time that positions are to be averaged (hours). 1.5 minutes to 100 hours
Option: desired horizontal standard deviation (m)
Option: desired vertical standard deviation (m)
Example:
posave 2,3,4
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2 – Command Descriptions
O
RESET
This command performs a hardware reset. It is only available on OEM Series GPSCards. Following a RESET
command, the GPSCard will initiate a cold-start bootup. Therefore, the receiver configuration will revert to the factory
default or last SAVECONFIG settings.
Syntax:
RESET
RT20
RESETRT20
This command performs a manual restart of RT20 mode. Convergence begins at the 1 m level and converges down to the
< 20 cm level in three to five minutes.
Syntax:
RESETRT20
R
RTCM16T
This is a NovAtel command relating to the RTCM Standard – Type 16 Special Message. It enables the user to enter an
ASCII message that can be sent out in RTCM Type 16 format. Once created, the RTCM16T message can be viewed in
the RCCA command settings list. The text message can also be logged using the RTCM16 or RTCM16T log option.
This command will limit the input message length to a maximum of 90 ASCII characters.
Refer to Chapter 8, page 129, for related topics.
R
RTCMRULE
This command allows the user flexibility in the usage of the RTCM Standard “bit rule”.
Refer to Chapter 8, page 130, for further information.
RT20
RTKMODE
This command sets up the RTK (RT-20) mode. Invoking this command allows you to set different parameters and control
the operation of the RTK system. The RTKMODE command is actually a family of commands; a description of the
various arguments and options is as follows. Some arguments require data input, while others do not.
Certain arguments can be used only at the reference station and others only at the remote station. The structure of the
syntax is shown on the next page, followed by a detailed description of each argument.
Syntax - Reference Station
For RTCA-format messaging only:
RTKMODE
sv_entries
4 to 20
RTKMODE
elev_mask
0 to 90
Command
RTKMODE
Argument
Data Range
Default
sv_entries
elev_mask
4 to 20
0 to 90
12
2
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2 – Command Descriptions
For RTCM-format messaging only:
RTKMODE
rtcmver
2.1 or 2.2
Command
RTKMODE
Argument
Data Range
Default
rtcmver
2.1 or 2.2
2.2
Syntax - Remote Station (for RTCA, RTCM or CMR-format messaging):
RTKMODE
enable
RTKMODE
disable
RTKMODE
auto
RTKMODE
static
RTKMODE
kinematic
Command
RTKMODE
Argument
Default Argument
enable or disable
auto, static or kinematic
enable
auto
Data Range
Below is additional information for each argument:
Station
Remote
Command
rtkmode
Argument
enable (default)
disable
RTKMODE ENABLE, when issued at the remote station, turns on its ability to receive and process RTCA or
RTCM messages.
RTKMODE DISABLE exits the RTK positioning mode.
Station
Remote
Command
rtkmode
Argument
auto (default)
static
kinematic
RTKMODE AUTO configures the RTK system to automatically detect motion. It is the default mode. It will
reliably detect motion of 2.5 cm/sec or greater. If you are undergoing motion slower than this that covers
more than 2 cm, you should use the manual mode selection commands (static and kinematic).
RTKMODE STATIC forces the RTK software to treat the remote station as though it were stationary,
regardless of the output of the motion detector.
Note: For reliable performance the antenna should not move more than 1 - 2 cm when in static mode.
RTKMODE KINEMATIC forces the RTK software to treat the remote station as though it was in motion,
regardless of the output of the motion detector. If the remote station is undergoing very slow steady motion
(< 2.5 cm/sec for more than 5 seconds), you should declare KINEMATIC mode to prevent inaccurate results
and possible resets.
Example:
rtkmode auto
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2 – Command Descriptions
O XII
SAVECONFIG
This command saves the current configuration and up to 10 active logging commands in flash (non-volatile) memory. It
is only available on 12-channel OEM cards with the SAVECONFIG option. The last saved configuration becomes the
new power-on default overriding the factory default.
Between 9 and 18 SAVECONFIG commands can be issued before a reset is necessary. If a SAVECONFIG is not
possible, the error message “Flash full – RESET or use FORCE option” will be given. If at this point the user enters
“SAVECONFIG FORCE”, the configuration will be saved and the card will be reset. If the flash memory is not full, the
FORCE option has no effect. SAVECONFIG FORCE will simply cause a normal save and no reset will occur.
A CRESET command may be entered to restore the factory default settings, which will become the new saved
configuration if the user enters another SAVECONFIG command. The RCCA log can be used to monitor the current
configuration.
Syntax:
SAVECONFIG
or
SAVECONFIG
FORCE
B
SEND
This command is used to send ASCII printable data from the console, COM1, COM2 or disk file to a specified
communications port. For instance, if you were using a PC Series GPSCard and wanted to control a modem connected to
COM1, you could issue all the dial and modem control commands from the console port (keyboard or disk file) using this
command. This is a one-time command, therefore the data message must be preceded by the SEND command followed
by the Enter key (<CR><LF>) each time you wish to send data. (Remember to use the MESSAGES command to disable
error reporting whenever two GPSCards are connected together via the COM ports.)
Syntax:
SEND
Syntax
SEND
to-port
data
to-port
data
Range Value
COM1, COM2, console
up to 100 characters
Description
Command
Port option
ASCII data
Scenario:
Assume that you are operating PC Series GPSCards as reference and remote stations. It could also be
assumed that the reference station is unattended but operational and you wish to control it from the remote station. From
the remote station, you could establish the data link and command the reference station GPSCard to send differential
corrections.
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GPSCard™ Command Descriptions Manual Rev 3
2 – Command Descriptions
Figure 2-5 Using SEND Command
B
SENDHEX
This command is like the SEND command but is used to send non-printable characters expressed as hexadecimal pairs.
Syntax:
SENDHEX
Syntax
SENDHEX
to-port
data
to-port
data
Range Value
COM1, COM 2, console
even number of ASCII characters from set of 0-9, A-F
spaces allowed between pairs of characters
carriage return & line feed provided by entering 0D0A at end of string
maximum number of characters limited to about 1400 characters by command interpreter buffer
(2800 ASCII characters pairs)
SETCHAN
Description
Command
Port option
ASCII data
XII
This command sets the maximum number of channels for tracking. For example, setting the number of tracking channels
to 10 on a 12-channel GPSCard will disable the last two channels (11 and 12) and will assign the highest SVs to the first
10 channels. Satellites that are lower to the horizon could be bumped. The value set will change the number of channels
reported in the CTSA/B logs.
Use this command if you wish your 12 channel GPSCard range data logs (RGEA/B) to be backwards compatible with
earlier versions of GPSCard 10 channel logs (RNGA/B).
Example:
SETCHAN 10
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2 – Command Descriptions
R
SETDGPSID
This command is used to enter a station ID. Once set, the receiver will only accept differential corrections from a station
whose ID matches the set station ID. It is typically used when a station has data links containing RTCM or RTCA
messages from several stations. By entering a specific station ID, the operator can select which station to listen to.
Having set a station ID, incoming DCSA, DCSB, RTCM, RTCMA, RTCA, RTCAA, and RTCAB messages will be
received from only that station. When a valid station ID is entered, an improved data synchronization algorithm will be
used. It is recommended to always set the station ID. This command can also be used to set the station ID for a
GPSCard reference station. See FIX POSITION, page 30, 4th parameter (station ID).
Syntax:
SETDGPSID
station ID #
SETDGPSID
all
or
Syntax
SETDGPSID
station ID #
Range Value
0 – 1023
or
“xxxx”
or
all
Description
Command
- Reference station ID number for DCSA/B or RTCM
Default
all
- Reference station name for RTCA where “xxxx” are four alphanumeric characters, entered
between double quotes
- Accepts differential corrections from any station
Example 1:
SETDGPSID 1023
Example 2:
SETDGPSID “abcd”
B
SETHEALTH
This command permits you the flexibility to override the broadcast health of a satellite. Under certain conditions and
applications, it may be desirable to track and use information from a GPS satellite even though its health has been set bad
by the GPS control segment. To SETHEALTH for more than one satellite, the command must be re-issued for each
satellite.
IMPORTANT: There is usually a reason when the GPS Control Segment sets a satellite to bad health condition. If you
decide to ignore the health warnings and use the satellite information, unpredictable errors may occur.
Syntax:
SETHEALTH prn
Syntax
SETHEALTH
prn
health
health
Range Value
1 - 32
good or bad
Description
Command
A satellite PRN integer number
Desired health
Default
resethealthall
Example:
sethealth 4,good
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2 – Command Descriptions
B
RESETHEALTH
This command cancels the SETHEALTH command and restores the health of a satellite to the broadcast value contained
in the almanac and ephemeris data.
Syntax:
prn
RESETHEALTH
Syntax
RESETHEALTH
prn
Range Value
1 - 32
Description
Command
The PRN integer number of the satellite to be restored.
Example:
resethealth 4
B
RESETHEALTHALL
This command resets the health of all satellites to the broadcast values contained in the almanac and ephemeris data.
Syntax:
RESETHEALTHALL
B
SETNAV
This command permits entry of one set of navigation waypoints (see Figure 2-6, page 46). The origin (FROM) and
destination (TO) waypoint coordinates entered are considered on the ellipsoidal surface of the current datum (default
WGS-84). Once SETNAV has been set, you can monitor the navigation calculations and progress by observing the
NAVA/B, GPRMB, and GPZTG log messages.
Track offset is the perpendicular distance from the great circle line drawn between the FROM lat-lon and TO lat-lon
waypoints. It establishes the desired navigation path, or track, that runs parallel to the great circle line, which now
becomes the offset track, and is set by entering the track offset value in metres. A negative track offset value indicates
that the offset track is to the left of the great circle line track. A positive track offset value (no sign required) indicates the
offset track is to the right of the great circle line track (looking from origin to destination). Refer to Figure 2-6, page 46,
for clarification.
Syntax:
SETNAV from-lat
from-lon
to-lat to-lon
track offset from-port to-port
or
SETNAV disable
Syntax
SETNAV
from-lat
Range Value
0.0 to ± 90.0
from-lon
0.0 to ± 360.0
to-lat
to-lon
track offset
0.0 to ± 90.0
0.0 to ± 360.0
± 1000
from-port
to-port
1 to 5 characters
1 to 5 characters
Description
Command
Origin latitude in units of degrees/decimal degrees. A negative sign implies South
latitude. No sign implies North latitude.
Origin longitude in units of degrees/decimal degrees. A negative sign implies West
longitude. No sign implies East longitude.
Destination latitude in units of degrees/decimal degrees
Destination longitude in units of degrees/decimal degrees
Waypoint great circle line offset (in metres); establishes offset track; positive
indicates right of great circle line; negative indicates left of great circle line
Optional ASCII station name
Optional ASCII station name
GPSCard™ Command Descriptions Manual Rev 3
Default
disable
Example
setnav
51.1516
-114.16263
51.16263
-114.1516
-125.23
from
to
45
2 – Command Descriptions
Example:
setnav 51.1516,-114.16263,51.16263,-114.1516,-125.23,from,to
Figure 2-6 Illustration of SETNAV Parameters
1st Waypoint Track
2nd Waypoint Track
A = FROM lat-lon (1)
B = TO lat-lon (1)
AD = Track Offset from A to D (perpendicular to AB)
AB = Great circle line drawn between A lat-lon and B lat-lon
DE = Offset track determined by track offset AD and parallel to AB
B = FROM lat-lon (2)
C = TO lat-lon (2)
BF = Track Offset from B to F (perpendicular to BC)
BC = Great circle line drawn between B lat-lon and C lat-lon
EF = Course to steer to get on track FG
FG = Offset track determined by track offset BF and parallel to BC
B
UNDULATION
This command permits you to either enter a specific geoidal undulation value or use the internal table of geoidal
undulations. The separation values only refer to the separation between the WGS-84 ellipsoid and the geoid, regardless
of the datum chosen.
Syntax:
UNDULATION
Syntax
UNDULATION
separation
Range Value
table
or
enter a value
separation
Description
Command
Selects the internal table of undulations and ignores any previously entered value. The
internal table utilizes OSU - 89B 18 x ~1.38.
A numeric entry that overrides the internal table with a value in metres.
Default
table
Example 1:
undulation table
Example 2:
undulation -5.6
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GPSCard™ Command Descriptions Manual Rev 3
2 – Command Descriptions
B
VERSION
Use this command to determine the current software version of the GPSCard. The response to the VERSION command
is logged to the port from which the command originated.
Syntax:
VERSION
Command
VERSION
Response Syntax
Card type
Model #S/N
HW Rev
SW Rev
Date
Example:
version
OEM-2 RT20 SGN98190073 HW 1 SW 3.352D6/1.02 Nov 11/98
console>
GPSCard™ Command Descriptions Manual Rev 3
47
3 – Special Input Data Commands
3
SPECIAL DATA INPUT COMMANDS ($xxxx)
This chapter focuses on the usage of Special NovAtel Data Input Commands ($xxxx). These commands are actually reinjection of NovAtel ASCII logs back into the GPSCard. The data structure must follow that defined in Chapter 4.0,
Output Logging. Therefore, each Special Command leads with the NovAtel ASCII log header “$xxxx” (e.g., $DCSA),
followed by valid data fields, and terminates with the “*xx” checksum field.
The injection of special command data can take place via COM1, COM2, or console (PC Series GPSCards). Remember,
the source of these special data commands is a valid NovAtel ASCII data log.
The special data commands fall into two categories: Differential Corrections and Almanac Data.
ALMANAC DATA
The GPSCard’s standard features include almanac data collection. Following a cold-start boot-up or system reset, the
GPSCard will begin a sky search. Once a valid satellite is acquired, the GPSCard will begin almanac downloading and
decoding. This process will take at least 12.5 minutes following the cold-start (assuming there are no problems with
satellite visibility or the antenna system). It is noted that Ionospheric Correction Data and UTC data are also collected at
the same time as almanac data and will also be available following the 12.5 minutes collection period mentioned above.
12 channel OEM cards with the SAVECONFIG option will automatically save almanacs in their Flash memory. They
will also automatically load the last saved almanac following a cold start or a reset. The card will save an almanac and
ionospheric and UTC data received from a satellite if there is no current data in flash, or if the GPS week number of the
received data is newer than the week number of the data in flash. The save will not occur until between 12.5 and 25
minutes have elapsed since the last reset. To check if almanac data is saved in the flash of the OEM card, check the
“almanac data saved” bit in the receiver status word. Refer to the RCSA/B logs, page 88, for details.
The PC Series GPSCard does not have Flash memory, and so the new almanac data that has been collected will reside in
the GPSCard RAM as long as system power is maintained or until a system restart is initiated. In the case of a restart, the
almanac collection process must be repeated once again.
The GPSCard is capable of logging almanac data utilizing the NovAtel-format ASCII log command option ALMA.
Once logged, the data records will precede the header with the $ character (e.g., $ALMA).
There are no specific NovAtel log option commands to independently specify output of ionospheric or UTC parameters.
These parameters will always output following the $ALMA log (identifiable by the headers $IONA and $UTCA
respectively). Refer to Chapter 4, page 52, for more information on the ALMA output log command option.
The GPSCard has the capability to accept injection of previously logged NovAtel-format ASCII almanac data ($ALMA,
$IONA, and $UTCA). The GPSCard will interpret this log data as special data input commands. This provides the user
with the advantage of being able to inject recent almanac data following a cold-start or RESET without having to wait the
12.5 minutes described in above paragraphs. As well, this provides you with faster and more accurate first-fix data
because of the advantage of a full almanac being resident immediately following the injection of the special data input
commands described above. This is especially beneficial when the receiver is cold-starting in an environment with poor
reception and frequent satellite visibility obstruction.
There are various ways by which this can be accomplished.
48
GPSCard™ Command Descriptions Manual Rev 3
3 – Special Input Data Commands
•
By connecting the COM1 or COM2 port from one GPSCard (base) directly to the COM1 or COM2 port of another
GPSCard (remote). The reference card is assumed to be tracking satellites for some time and can be commanded by
the ALMA log command option to output almanac records to the remote card. The remote card can be assumed to
be just powered-up or RESET and will recognize the $ALMA, $IONA, and $UTCA data as special input
commands and update its almanac tables with this new data.
REMEMBER: When connecting two GPSCard com ports together, the messages command option should be set to
“off” to prevent inter-card “chatter”.
•
If the GPSCard is a PC Series type, it can log current almanac data to its host PC disk utilizing the log console
command to direct the almanac data to a file called almanac.dat. At a later time following a system restart, the
GPSCard can have this almanac.dat file (containing $ALMA, $IONA, and $UTCA records) downloaded as a
special input command for immediate use. This is accomplished utilizing the GPSLOAD MAIN.BTL
/aalmanac.dat boot-up option. Refer to the “GPSCard PC Series Installation and Operating Manual” for further
information on GPSLOAD, MAIN.BTL, and GPSCON.
•
If the GPSCard is an OEM Series type, it can log current almanac data to a PC connected to its COM1 or COM2
port. Assuming the PC is correctly configured using terminal emulator communications software, then the PC can
redirect the GPSCard almanac log to its disk storage device. At a later time following a system restart, the
GPSCard can have this almanac.dat file (containing $ALMA, $IONA, and $UTCA records) immediately
downloaded as a special input command for immediate use. Refer to the “GPSCard OEM Series Installation and
Operating Manual” for more information about interfacing with the OEM card with a PC. [Note: this procedure
will generally not be required with OEM cards as all 12 channel cards now have an almanac save feature built in
using flash memory.]
PROTOCOLS:
$ALMA...
B
Use this special data input command to quickly update the GPSCard almanac tables following a system restart. It is
generated from a GPSCard ALMA log and is accepted by any GPSCard as the following format:
$ALMA,1,3.55148E-003,552960,744,-7.8174E-009,6.10457691E-002,-1.1820041E+000,
1.90436112E+000,-1.8119E-005,-3.6379E-012,1.45854758E-004,2.65602532E+007,
9.55600E-001,1,0,0*0C
...
(one record for each valid satellite)
...
$ALMA,31,4.90379E-003,552960,744,-7.9660E-009,-3.1044479E+000,6.13853346E-001,
1.92552900E+000,6.67572E-006,3.63797E-012,1.45861764E-004,2.65594027E+007,
9.61670E-001,1,0,0*3F
$IONA...
B
Use this special data input command to quickly update the GPSCard ionospheric correction tables following a system
restart (always appended to $ALMA records unless intentionally stripped). This data will ensure that the initial position
solutions computed by the GPSCard are as accurate as possible. It is generated from a GPSCard ALMA log and is
accepted by any GPSCard as the following format:
$IONA,1.0244548320770265E-008,1.4901161193847656E-008,-5.960464477539061E-008,
-1.192092895507812E-007,8.8064000000000017E+004,3.2768000000000010E+004, 1.966080000000001E+005,-1.966080000000001E+005*02
GPSCard™ Command Descriptions Manual Rev 3
49
3 – Special Input Data Commands
$UTCA...
B
Use this special data input command to quickly update the GPSCard Universal Time Coordinated (UTC) parameters
following a system restart (always appended to $ALMA records unless intentionally stripped). The UTC data is required
before the GPSCard can accurately compute UTC time. If not input with $UTCA, it may take up to 12.5 minutes after a
reset for the GPSCard to receive current UTCA data. In order to comply with NMEA standards, the GPSCard will null
NMEA log data fields until valid UTC parameters are collected or injected by the $UTCA input command. This
command is generated from a GPSCard ALMA log and is accepted by any GPSCard as the following format:
$UTCA,-1.769512891769409E-008,-1.776356839400250E-015,552960,744,755,9,10,5*03
DIFFERENTIAL CORRECTIONS DATA
NovAtel GPSCards with differential capability (xxxxR models) can utilize the special data input commands $DCSA,
$RTCA and $RTCM. A GPSCard operating as a remote station to accept NOVATEL ASCII format differential
corrections utilizes these special data input commands. The data is generated by a GPSCard operating as a reference
station with intent to be received by remote stations. To correctly interpret these commands, the remote GPSCard must
have its ACCEPT command option set to “COMMANDS” (default). Refer to Chapter 10, page 137, for further
information on differential positioning.
PROTOCOLS:
$DCSA...
R
Use this special data input command to directly input NovAtel DCSA differential correction data, ASCII format. The
data can be accepted using the host PC console (PC Series cards), COM1, or COM2. The differential corrections will be
accepted and applied upon receipt of this special data input command.
The data is generated from a GPSCard DCSA log and is accepted by a GPSCard remote station without any special
initialization. The DCSA data format is as follows:
$DCSA,744,488906.00,1,7,19,165,267.718,-0.195,22,123,-592.682,-0.361,29,223,
-91.016,0.065,4,138,-188.193,-0.025,28,154,64.760,-0.465,18,141,-270.081,
0.020,14,77,730.942,-0.135*13
$RTCA... (RTCAA)
R
Use this special data input command to directly input NovAtel RTCAA differential correction data, ASCII format. The
data can be accepted using the host PC console (PC Series cards), COM1, or COM2. The differential corrections will be
accepted and applied upon receipt of this special data input command.
The data is generated from a GPSCard RTCAA log and is accepted by a GPSCard remote station as in the following
format:
$RTCA,990000000447520607BE7C92FA0B82423E9FE507DF5F3FC9FD071AFC7FA0D207D090808C
0E045BACC055E9075271FFB0200413F43FF810049C9DFF8FFD074FCF3C940504052DFB*20
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3 – Special Input Data Commands
$RTCM... (RTCMA)
R
Use this special data input command to directly input RTCMA differential correction data, ASCII format (RTCM data
converted to ASCII hexadecimal, with NovAtel header added). The data can be accepted using the host PC console (PC
Series cards), COM1, or COM2. The differential corrections will be accepted and applied upon receipt of this special
data input command. Refer to Chapter 8, page 129, for further information on RTCM related topics.
The data is generated from a GPSCard RTCMA log and is accepted by a GPSCard remote station as in the following
format:
$RTCM,664142404E7257585C6E7F424E757D7A467C47414F6378635552427F7357726162427877
7F5B5A525C7354527C4060777B4843637C7F555F6A784155597D7F6763507B77496E7F7A6A426F
555C4C604F4E7F467F5A787F6B5F69506C6D6A4C*2B
NOTE: The $DCSA, $RTCA and $RTCM commands allow the user to intermix differential corrections along with other
ASCII commands or logs over a single port. (You must, however, ensure that the ACCEPT command option is set to
“COMMANDS”.
TIP: The decoding success and status of $DCSA, $RTCA and $RTCM records can be monitored using the CDSA/B data
log. These commands will not generate any reply response from the command interpreter. They will simply be
processed for valid format and checksum and used internally. If there is any problem with the data, characters missing or
checksum fail, the data will be discarded with no warning message.
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51
5 – NovAtel Format Data Logs
4
OUTPUT LOGGING
GENERAL
The GPSCard provides versatility in your logging requirements. You can direct your logs to the console, COM1, COM2,
or all three ports, as well as combine data types. The GPSCard has four major logging formats:
•
•
•
•
NovAtel Format Data Logs (ASCII/Binary)
NMEA Standard Format Data Logs (ASCII)
RTCM Standard Format Data Logs (Binary)
RTCA Standard Format Data Logs (Binary)
All data types can be logged using several methods of triggering each log event. Each log is initiated using the LOG
command. The LOG command and syntax are listed below.
Syntax:
log port,datatype,[trigger,{period},{offset}]
Syntax
LOG
port
datatype
trigger
period
offset
Description
Console, COM1 or COM2
Enter one of the valid ASCII or Binary Data Logs (see Chapter 5, page 54)
Enter one of the following triggers.
ONCE
Immediately logs the selected data to the selected port once. Default if trigger field is left blank.
ONMARK
Logs the selected data when a MARKIN electrical event is detected. Outputs internal buffers at
time of mark – does not extrapolate to mark time. Use MKPA/B for extrapolated position at time
of mark .
ONNEW
Logs the selected data each time the data is new even if the data is unchanged.
ONCHANGED
Logs the selected data only when the data has changed.
ONTIME
Immediately logs the selected data and then periodically logs the selected data at a frequency
[period],
determined by the period and offset parameters. The logging will continue until an UNLOG
[offset]
command pertaining to the selected data item is received (see UNLOG Command, page 37).
CONTINUOUSLY Will log the data all the time. The GPSCard will generate a new log when the output buffer
associated with the chosen port becomes empty. This may cause unpredictable results if
more than one log is assigned to the port. The continuously option was designed for use with
differential corrections over low bit rate data links. This will provide optimal record generation
rates. The next record will not be generated until the last byte of the previous record is loaded
into the output buffer of the UART.
Use only with the ONTIME trigger. Units for this parameter are seconds. The selected period may be any value from
0.05 second to 3600 seconds. Selected data is logged immediately and then periodic logging of the data will start at
the next even multiple of the period. If a period of 0.20 sec is chosen, then data will be logged when the receiver time
is at the 0.20, 0.40, 0.60 and the next (0.80) second marks. If the period is 15 seconds, then the logger will log the data
when the receiver time is at even 1/4 minute marks. The same rule applies even if the chosen period is not divisible
into its next second or minute marks. If a period of 7 seconds is chosen, then the logger will log at the multiples of 7
seconds less than 60, that is, 7, 14, 21, 28, 35, 42, 49, 56 and every 7 seconds thereafter.
Use only with the ONTIME trigger. Units for this parameter are seconds. It provides the ability to offset the logging
events from the above startup rule. If you wished to log data at 1 second after every minute you would set the period to
60 seconds and the offset to 1 second (Default is 0).
Example
LOG
COM1
POSA
ONTIME
60
1
Example:
log com1,posa,ontime,60,1
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5 – NovAtel Format Data Logs
If the LOG syntax does not include a trigger type, it will be output only once following execution of the LOG command.
If trigger type is specified in the LOG syntax, the log will continue to be output based on the trigger specification.
Specific logs can be disabled using the UNLOG command, whereas all enabled logs will be disabled by using the
UNLOGALL command (refer to Chapter 2, page 37). All activated logs will be listed in the receiver configuration status
log (RCCA).
Table 4-1 GPSCard Log Summary
Datatype
ALMA/B
CDSA/B
CLKA/B
COM1A/B
COM2A/B
CONSOLEA/B
CTSA/B
DCSA/B
DOPA/B
FRMA/B
FRWA/B
GGAB
MKPA/B
MKTA/B
NAVA/B
P20A/B
PAVA/B
POSA/B
GPALM
GPGGA
GPGLL
GPGRS
GPGSA
GPGST
Syntax: log port,datatype,trigger,[period,offset]
NovAtel Format Logs
Description
Datatype
Description
Decoded Almanac
PRTKA/B
Computed Position
Communication and Differential Decode Status
PXYA/B
Computed Cartesian Coordinate Position
Receiver Clock Offset Data
RALA/B
Raw Almanac
Log data from COM1
RCCA
Receiver Configuration
Log data from COM2
RCSA/B
Receiver status incl. S/W version, # of working channels,
CPU idle time, BISTs status, clock status
Log data from console
REPA/B
Raw Ephemeris
Channel Tracking Status
RGEA/B/C/D Channel Range Measurements
Differential Corrections - NovAtel format
RT20A/B
Computed Position – Time Matched
Dilution of Precision
RTCAA/B
RTCA format Differential Corrections with NovAtel headers
Framed Raw Navigation Data
RTCMA/B
RTCM Type 1 Differential Corrections with NovAtel headers
Framed Raw Navigation Words
RTCM16T
Special Message – NovAtel ASCII Format
Global Position System Fix Data - Binary Format
RTKA/B
Computed Position – Time Matched
Mark Position
SATA/B
Satellite Specific Data
Time of Mark Input
SPHA/B
Speed and Direction Over Ground
Navigation Data
SVDA/B
SV Position in ECEF XYZ Coordinates with Corrections
Computed Position – Best Available
TM1A/B
Time of 1PPS
Positioning Averaging Status
VERA/B
GPSCard current hardware type and software version number
Computed Position
VLHA/B
Velocity, Latency, and Direction over Ground
NMEA Format Logs
Almanac Data
GPGSV
GPS Satellites in View
Global Position System Fix Data
GPGSV
GPS Satellites in View
Geographic Position - lat/lon
GPRMB
Generic Navigation Information
GPS Range Residuals for Each Satellite
GPRMC
GPS Specific Information
GPS DOP and Active Satellites
GPVTG
Track Made Good and Ground Speed
Pseudorange Measurement Noise Statistics
GPZDA
UTC Time and Date
GPZTG
UTC & Time to Destination Waypoint
RTCA Format
RTCA
RTCA Differential Corrections
RTCM
RTCM3
RTCM16
RTCM59
RTCM Format
Type 1 – Differential Corrections
Type 3 – Reference Station Precise Position Data
Type 16 – Special Message
Type 59 Proprietary Message “N” – Pseudorange and Carrier Phase Observation Data
N.B.
A/B/C/D
A
B
C
D
refers to GPSCard output logs in ASCII format.
refers to GPSCard output logs in Binary format.
refers to GPSCard output logs in Compressed binary format.
refers to GPSCard output logs in Compressed binary format.
GPSCard™ Command Descriptions Manual Rev 3
53
5 – NovAtel Format Data Logs
5
NOVATEL FORMAT DATA LOGS
GENERAL
The GPSCard is capable of executing more than 30 NovAtel format log commands. Each log is selectable in ASCII and
Binary formats. The one exception to this rule is the RGE log, which can be logged as RGEC/D. The "C" or “D”
indicates a compressed binary format to allow higher speed logging. Any format can be selected individually or
simultaneously over the same COMn ports.
All of the following log descriptions are listed in alphabetical order. Each log first lists the ASCII format, followed by
the Binary format description.
ASCII LOG STRUCTURE
Log types ending with the letter A (or a) will be output in ASCII format (e.g., POSA). The structures of all ASCII logs
follow the general conventions as noted here:
1.
The lead code identifier for each record is '$'.
2.
Each log is of variable length depending on amount of data and formats.
3.
All data fields are delimited by a comma ',' with the exception of the last data field, which is followed by a * to
indicate end of message data.
4.
Each log ends with a hexadecimal number preceded by an asterisk and followed by a line termination using the
carriage return and line feed characters, e.g., *xx[CR][LF]. This 8-bit value is an exclusive OR (XOR) of all
bytes in the log, excluding the '$' identifier and the asterisk preceding the two checksum digits.
Structure:
$xxxx, data field..., data field...,
data field...
*xx [CR][LF]
BINARY LOG STRUCTURE
Log types ending with the letter B (or b) will be output in Binary format (e.g., POSB). The structures of all Binary logs
follow the general conventions as noted here:
1.
Basic format of:
2.
The Sync bytes will always be:
Byte
First
Second
Third
3.
54
Sync
Checksum
Message ID
Message byte count
Data
Hex
AA
44
11
3 bytes
1 byte
4 bytes unsigned integer
4 bytes unsigned integer
x bytes
Decimal
170
68
17
The Checksum is an XOR of all the bytes (including the 12 header bytes) and is initially set to 00.
GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
4.
The Message ID identifies the type of log to follow.
5.
The Message byte count equals the total length of the data block including the header.
NOTE: Maximum flexibility for logging data is provided to the user by these logs. The user is cautioned, however, to
recognize that each log requested requires additional CPU time and memory buffer space. Too many logs may result in
lost data and degraded CPU performance. CPU overload can be monitored using the idle-time and buffer overload bits
from the RCSA/B log. Refer to Table 5-5, page 90.
The following table describes the format types used in the description of binary logs.
Type
char
Size (bytes)
1
Size (bits)
8
int
4
32
double
8
64
float
4
32
Description
The char type is used to store the integer value of a member of the representable character set.
That integer value is the ASCII code corresponding to the specified character.
The size of a signed or unsigned int item is the standard size of an integer on a particular machine.
On a 32-bit processor (such as the NovAtel GPSCard), the int type is 32 bits, or 4 bytes. The int
types all represent signed values unless specified otherwise. Signed integers are represented in
two’s-complement form. The most-significant bit holds the sign: 1 for negative, 0 for positive and
zero.
The double type contains 64 bits: 1 for sign, 11 for the exponent, and 52 for the mantissa. Its
range is ±1.7E308 with at least 15 digits of precision.
The float type contains 32 bits: 1 for the sign, 8 for the exponent, and 23 for the mantissa. Its
range is ±3.4E38 with at least 7 digits of precision.
Each byte within an int has its own address, and the smallest of the addresses is the address of the int. The byte at this
lowest address contains the eight least significant bits of the doubleword, while the byte at the highest address contains
the eight most significant bits. The following illustration shows the arrangement of bytes within words and doublewords.
Similarly the bits of a "double" type are stored least significant byte first. This is the same data format used by IBM PC
computers.
0
7
char
address n
int
23
31
float
7
0
two’s
complement
n+3
62
double
15
55
n+2
51
n+1
47
address n
39
31
S Biased
52-bits mantissa
exponent
63
52
n+5
n+7
n+6
n+4
n+3
30
15
7
22
0
32-bits mantissa
S Biased
exponent
23
31
address n
n+2
n+1
n+3
GPSCard™ Command Descriptions Manual Rev 3
23
7
15
0
0
n+2
n+1
address n
55
5 – NovAtel Format Data Logs
GPS TIME vs LOCAL RECEIVER TIME
All logs report GPS time expressed in GPS weeks and seconds into the week. The time reported is not corrected for local
receiver clock error. To derive the closest GPS time, one must subtract the clock offset shown in the CLKA log (field 4)
from GPS time reported.
GPS time is based on an atomic time scale. Universal Time Coordinated (UTC) time (reported in NMEA logs) is also
based on an atomic time scale, with an offset of seconds applied to coordinate Universal Time to GPS time. GPS time is
designated as being coincident with UTC at the start date of January 6, 1980 (00 hours). GPS time does not count leap
seconds, and therefore an offset exists between UTC and GPS time (at this date: 12 seconds). The GPS week consists of
604800 seconds, where 000000 seconds is at Saturday midnight. Each week at this time, the week number increments by
one, and the seconds into the week resets to 0.
LOG DESCRIPTIONS
ALMA/B
B
Decoded Almanac
This log contains the decoded almanac parameters from subframes four and five as received from the satellite with the
parity information removed and appropriate scaling applied. Multiple messages are transmitted, one for each SV almanac
collected. The Ionospheric Model parameters (IONA) and the UTC Time parameters (UTCA) are also provided,
following the last almanac records. For more information on Almanac data, refer to the GPS SPS Signal Specification.
(See Appendix D, page 178, of this manual for References.)
You can use the ALMA log to create a PC Series GPSCard almanac boot-up file. The boot file can then be used to inject
recent almanac data back into the GPSCard when performing a cold start. See the “PC Series GPSCard Installation and
Operating Manual” for more information on creating almanac boot files. 12 channel OEM cards with the
SAVECONFIG option will automatically save almanacs in their Flash memory, therefore creating an almanac boot file
would not be necessary.
ALMA
Structure:
$ALMA
A
prn ecc
incl-angle
seconds
health-4
week
rate-ra
health-5
ra
w
Mo
health-alm
af0
af1
cor-mean-motion
*xx [CR][LF]
ALMA Format
Field #
1
2
3
4
5
6
7
56
Field type
$ALMA
prn
ecc
seconds
week
rate-ra
ra
Data Description
Log header
Satellite PRN number for current message
Eccentricity
Almanac reference time, seconds into the week
Almanac reference week (GPS week number)
Rate of right ascension, radians
Right ascension, radians
Example
$ALMA
1
3.55577E-003
32768
745
-7.8860E-009
-6.0052951E-002
GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
Field #
8
9
Field type
w
Mo
Data Description
Argument of perigee, radians
Mean anomaly, radians
Example
-1.1824254E+000
1.67892137E+000
Clock aging parameter, seconds
-1.8119E-005
11
af0
af1
Clock aging parameter, seconds/second
-3.6379E-012
12
13
14
15
16
17
18
19
cor-mean-motion
A
incl-angle
health-4
health-5
health-alm
*xx
[CR][LF]
Corrected mean motion, radians/second
Semi-major axis, metres
Angle of inclination, radians
Anti-spoofing and SV config from subframe 4, page 25
SV health, 6 bits/SV (subframe 4 or 5, page 25)
SV health, 8 bits (almanac)
Checksum
Sentence terminator
1.45854965E-004
2.65602281E+007
9.55576E-001
1
0
0
*20
[CR][LF]
$ALMA
$ALMA
$IONA
$UTCA
Next satellite PRN almanac message
Last satellite PRN almanac message
Ionospheric Model Parameters
UTC Time Parameters
10
1 – 19
1 – 19
1 – 11
1 – 11
Example:
$ALMA,1,3.55577E-003,32768,745,-7.8860E-009,-6.0052951E-002,-1.1824254E+000,
1.67892137E+000,-1.8119E-005,-3.6379E-012,1.45854965E-004,2.65602281E+007,
9.55576E-001,1,0,0*20[CR][LF]
...
$ALMA,31,4.90665E-003,32768,745,-8.0460E-009,3.05762855E+000,6.14527459E-001,
1.69958217E+000,6.67572E-006,3.63797E-012,1.45861888E-004,2.65593876E+007,
9.61664E-001,1,0,0*13[CR][LF]
IONA Format
Structure:
$IONA
Field #
1
2
3
4
act a1ot
a2ot
a3ot
bct
b1ot
b2ot
b3ot
*xx [CR][LF]
Field type
$IONA
act
a1ot
a2ot
Data Description
Log header
Alpha constant term, seconds
Alpha 1st order term, sec/semicircle
Alpha 2nd order term, sec/(semic.)2
Example
$IONA
1.0244548320770265E-008
1.4901161193847656E-008
-5.960464477539061E-008
5
a3ot
-1.192092895507812E-007
6
7
8
bct
b1ot
b2ot
Alpha 3rd order term, sec/(semic.)3
Beta constant term, seconds
Beta 1st order term, sec/semicircle
Beta 2nd order term, sec/(semic.)2
8.8064000000000017E+004
3.2768000000000010E+004
-1.966080000000001E+005
Beta 3rd order term, sec/(semic.)3
Checksum
Sentence terminator
*02
[CR][LF]
9
b3ot
10
11
*xx
[CR][LF]
-1.966080000000001E+005
Example:
$IONA,1.0244548320770265E-008,1.4901161193847656E-008,-5.960464477539061E-008,
-1.192092895507812E-007,8.8064000000000017E+004,3.2768000000000010E+004,
-1.966080000000001E+005,-1.966080000000001E+005*02[CR][LF]
GPSCard™ Command Descriptions Manual Rev 3
57
5 – NovAtel Format Data Logs
UTCA Format
Structure:
$UTCA
*xx
pct p1ot
data-ref
wk#-utc
wk#-lset
delta-time
lsop
day #-lset
[CR][LF]
Field #
1
2
3
4
5
6
7
8
9
10
11
Field type
$UTCA
pct
p1ot
data-ref
wk #-utc
wk #-lset
delta-time
lsop
day #-lset
*xx
[CR][LF]
Data Description
Log header
Polynomial constant term, seconds
Polynomial 1st order term, seconds/second
UTC data reference time, seconds
Week number of UTC reference, weeks
Week number for leap sec effect time, weeks
Delta time due to leap sec, seconds
For use when leap sec on past, seconds
Day number for leap sec effect time, days
Checksum
Sentence terminator
Example
$UTCA
-2.235174179077148E-008
-1.243449787580175E-014
32768
745
755
9
10
5
*37
[CR][LF]
Example:
$UTCA,-2.235174179077148E-008,-1.243449787580175E-014,32768,745,755,9,10,5*37
[CR][LF]
ALMB
ALMB Format:
Field #
1
(header)
58
Message ID = 18
2
3
4
5
6
7
8
9
10
Field Type
Sync
Checksum
Message ID
Message byte count
Satellite PRN number
Eccentricity
Almanac ref. time
Almanac ref. week
Omegadot - rate of right ascension
Right ascension
Argument of perigee
w
Mean anomaly
Mo
Clock aging parameter
af0
11
Clock aging parameter
12
13
14
15
16
17
Corrected mean motion
Semi-major axis
Angle of inclination
Sv health from subframe 4
Sv health from subframe 5
Sv health from almanac
af1
A
Message byte count = 120
Bytes
3
1
4
4
4
8
8
4
8
8
8
8
8
Format
Units
Offset
0
3
4
8
12
16
24
32
36
44
52
60
68
integer
double
double
integer
double
double
double
double
double
dimensionless
dimensionless
seconds
weeks
radians/second
radians
radians
radians
seconds
8
double
seconds/second
76
8
8
8
4
4
4
double
double
double
integer
integer
integer
radians/second
metres
radians
discretes
discretes
discretes
84
92
100
108
112
116
GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
IONB Format:
Field #
1
(header)
Message ID = 16
Message byte count = 76
2
3
4
Field Type
Sync
Checksum
Message ID
Message byte count
Alpha constant term
Alpha 1st order term
Alpha 2nd order term
Bytes
3
1
4
4
8
8
8
Format
char
char
integer
integer
double
double
double
Units
5
Alpha 3rd order term
8
double
Beta constant term
Beta 1st order term
Beta 2nd order term
8
8
8
double
double
double
sec/(semic.)3
seconds
sec/semic
sec/(semic.)2
6
7
8
44
52
60
9
Beta 3rd order term
8
double
sec/(semic.)3
68
UTCB Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
Message ID = 17
bytes
seconds
sec/semicircle
sec/(semic.)2
Offset
0
3
4
8
12
20
28
36
Message byte count = 52
Field Type
Sync
Checksum
Message ID
Message byte count
Polynomial constant term
Polynomial 1st order term
UTC data reference time
Week number UTC reference
Week number for leap sec effect time
Delta time due to leap sec
For use when leap sec on past
Day number for leap sec effect time
Bytes
3
1
4
4
8
8
4
4
4
4
4
4
Format
char
char
integer
integer
double
double
integer
integer
integer
integer
integer
integer
CDSA/B Communication and Differential Decode Status
Units
bytes
seconds
seconds/second
seconds
weeks
weeks
seconds
seconds
days
Offset
0
3
4
8
12
20
28
32
36
40
44
48
B (R)
The GPSCard maintains a running count of a variety of status indicators of the data link. This log outputs a report of
those indicators.
Parity and framing errors will occur if poor transmission lines are encountered or if there is an incompatibility in the data
protocol. If errors occur, you may need to confirm the bit rate, number of data bits, number of stop bits, and parity of
both the transmit and receiving ends. Overrun errors will occur if more characters are sent to the UART than can be
removed by the on-board microprocessor.
GPSCard™ Command Descriptions Manual Rev 3
59
5 – NovAtel Format Data Logs
CDSA
Structure:
$CDSA
week
seconds
xon1
xon2
cts2
parity2
overrun2
rtca
crc
res’d
rtcaa
chk
res’d
rtca
good
res’d
Field type
$CDSA
week
seconds
xon1
Data Description
Log header
GPS week number
GPS seconds into the week
Flag to indicate that the com1 is using XON/XOFF handshaking protocol and port has received an xoff
and will wait for an xon before sending any more data.
Flag to indicate that com1 is using CTS/RTS handshake protocol and cts line port has been asserted.
The port will wait for the line to de-assert before sending any more data.
A running count of character parity errors from the UART of COM1
A running count of UART buffer overrun errors of COM1
A running count of character framing error from the UART of COM1
A running count of the characters received from COM1
A running count of the characters sent out COM1
Flag to indicate that the COM2 is using XON/XOFF handshaking protocol and port has received an xoff
and will wait for an xon before sending any more data.
Flag to indicate that COM2 is using CTS/RTS handshake protocol and cts line port has been asserted.
The Port will wait for the line to de-assert before sending any more data.
A running count of character parity errors from the UART of COM2
A running count of UART buffer overrun errors of COM2
A running count of character framing error from the UART of COM2
A running count of the characters received from COM2
A running count of the characters sent out COM2
A running count of RTCA CRC failures
A running count of invalid ASCII $RTCA,....,*xx records indicating that the ASCII checksum "xx" failed.
A running count of RTCA records that pass error checking
A running count of 30 bit RTCM parity failures
A running count of invalid ASCII $RTCM,....,*xx records indicating that the ASCII checksum "xx" failed.
A running count of RTCM records that pass error checking
A running count of invalid ASCII $DCSA,....,*xx records
A running count of DCSA records that pass error checking
A running count of invalid binary DCSB records
A running count of DCSB records that pass error checking
Reserved for future use
Reserved for future use
Reserved for future use
Checksum
Sentence terminator
Field #
1
2
3
4
5
cts1
6
7
8
9
10
11
parity1
overrun1
framing1
rx1
tx1
xon2
12
cts2
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
parity2
overrun2
framing2
rx2
tx2
rtcacrc †
rtcaachk †
rtcagood †
rtcmpar †
rtcmachk †
rtcmgood †
dcsachk †
dcsagood †
dcsbchk †
dcsbgood †
*xx
[CR][LF]
†
rtcm
par
*xx
cts1
parity1
framing2
rtcma
rtcm
chk
good
[CR][LF]
overrun1
framing1
rx1
tx1
rx2 tx2
dcsa
chk
dcsa
good
dcsb
chk
dcsb
good
Example
$CDSA
787
500227
0
0
0
0
0
0
9
0
0
0
0
0
0
9
0
0
0
0
0
0
0
0
0
0
0
0
0
*33
[CR][LF]
Fields 18-27 will be 0 except on GPSCards with (R) options.
Example:
$CDSA,787,500227,0,0,0,0,0,0,9,0,0,0,0,0,0,9,0,0,0,0,0,0,0,0,0,0,0,0,0
*33[CR][LF]
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
CDSB
Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
CLKA/B
Message ID = 39
Message byte count = 128
Data
Sync
Checksum
Message ID
Message byte count
Week number
Time of week
Xon COM1
CTS COM1
Parity errors COM1
Overrun errors COM1
Framing error COM1
Bytes received in COM1
Bytes sent out COM1
Xon COM2
CTS COM2
Parity errors COM2
Overrun errors COM2
Framing error COM2
Bytes received in COM2
Bytes sent out COM2
RTCA CRC fails †
RTCAA checksum fails †
RTCA records passed †
RTCM parity fails †
RTCMA checksum fails †
RTCM records passed †
DCSA checksum fails †
DCSA records passed †
DCSB checksum fails †
DCSB records passed †
Reserved
Reserved
Reserved
Receiver Clock Offset Data
Bytes
3
1
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
Format
char
char
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
integer
Units
weeks
seconds
1 or 0
1 or 0
Total count
Total count
Total count
Total count
Total count
1 or 0
1 or 0
Total count
Total count
Total count
Total count
Total count
Total count
Total count
Total count
Total count
Total count
Total count
Total count
Total count
Total count
Total count
Total count
Total count
Total count
Offset
0
3
4
8
12
16
20
24
28
32
36
40
44
48
52
56
60
64
68
72
76
80
84
88
92
96
100
104
108
112
116
120
124
B
This record is used to monitor the state of the receiver time. Its value will depend on the CLOCKADJUST command. If
CLOCKADJUST is enabled, then the offset and drift times will approach zero. If not enabled, then the offset will grow
at the oscillator drift rate. Disabling CLOCKADJUST and monitoring the CLKA/B log will allow you to determine the
error in your GPSCard receiver reference oscillator as compared to the GPS satellite reference.
All logs report GPS time not corrected for local receiver clock error. To derive the closest GPS time one must subtract
the clock offset shown in the CLKA log (field 4) from GPS time reported.
The interpretation of Field #6 will depend on whether an external oscillator is used (for further information, please refer
to the EXTERNALCLOCK command, page 29).
GPSCard™ Command Descriptions Manual Rev 3
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5 – NovAtel Format Data Logs
CLKA
Structure:
$CLKA
week
seconds
offset
drift
drift rate offset std
drift std cm status
*xx [CR][LF]
Field #
1
2
3
4
5
Field type
$CLKA
week
seconds
offset
drift
6 (case 1)
drift rate
6 (case 2)
SA GaussMarkov state
7
8
9
offset std
drift std
cm status
10
11
*xx
[CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week
Receiver clock offset, in seconds. A positive offset implies that the receiver clock is
ahead of GPS Time. To derive GPS time, use the following formula:
GPS time = receiver time – (offset)
Receiver clock drift, in seconds per second. A positive drift implies that the receiver
clock is running faster than GPS Time.
In normal (TCXO) mode, this field contains the value of the receiver’s internal clock‘s
drift rate, in units of seconds per second per second.
In the presence of an external reference clock (after the EXTERNALCLOCK command
has been issued) this field contains the output value of the Gauss-Markov Selective
Availability clock dither estimator, in units of seconds. The value reflects both the
collective SA-induced short-term drift of the satellite clocks as well as any range bias
discontinuities that would normally affect the clock model’s offset and drift states.
Standard deviation of receiver clock offset, in seconds
Standard deviation of receiver drift, in seconds per second
Receiver Clock Model Status where 0 is valid and values from -21 to -1 imply that the
model is in the process of stabilization
Checksum
Sentence terminator
Example
$CLKA
637
511323.00
-4.628358547E-003
-2.239751396E-007
8.292986898E-013
2.061788299E-006
5.369997167E-008
4.449097711E-009
0
*7F
[CR][LF]
Example (case 1):
$CLKA,637,511323.00,-4.628358547E-003,-2.239751396E-007,8.292986898E-013,
5.369997167E-008,4.449097711E-009,0*7F[CR][LF]
Example (case 2):
$CLKA,841,499296.00,9.521895494E-008,-2.69065747E-008,2.061788299E-006,
9.642598169E-008,8.685638908E-010,0*4F
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
CLKB
Format:
Field #
1
(header)
2
3
4
5
6 (case 1)
6 (case 2)
7
8
9
COM1A/B
Message ID = 02
Field Type
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
Clock offset
Clock drift
Clock drift rate
SA Gauss-Markov state
StdDev clock offset
StdDev clock drift
Clock model status
Message byte count = 68
Bytes
3
1
4
4
4
8
8
8
8
8
8
8
4
Format
char
char
integer
integer
integer
double
double
double
double
double
double
double
integer
Data Pass-Through COM1 port
Units
bytes
weeks
seconds
seconds
seconds per second
seconds per second squared
seconds
seconds
seconds per second
0 = good, -1 to –21 = bad
Offset
0
3
4
8
12
16
24
32
40
48
56
64
B
See Chapter 6, page 113, for details concerning Pass-Through logs.
COM2A/B
Data Pass-Through COM2 port
B
See Chapter 6, page 113, for details concerning Pass-Through logs.
CONSOLEA/B
Data Pass-Through Console port
B
See Chapter 6, page 113, for details concerning Pass-Through logs.
CTSA/B
Channel Tracking Status
B
This log provides channel tracking status information for each of the GPSCard parallel channels. The channel
information is sequential from channel 1 to channel n, where n is the highest tracking channel available in the GPSCard
you are currently using. This log is intended for status display only. Because some of the data elements are not
synchronized together, do not use this information for measurement data. Refer to the logs RGEA/B/C/D, page 93,
SATA/B, page 102, and SVDA/B, page 105, to obtain synchronized data for post processing analysis.
GPSCard™ Command Descriptions Manual Rev 3
63
5 – NovAtel Format Data Logs
CTSA
Structure:
$CTSA
prn
week
seconds
sol status # chans
chan st
dopp
c/no
chan st
dopp
c/no residual locktime psr reject code *xx [CR][LF]
residual locktime psr reject code
:
prn
Field #
1
2
3
4
5
6
7
8
9
10
11
12
13
14-21
94-101
102
103
Field type
$CTSA
week
seconds
sol status
# chans
prn
chan st
dopp
c/no
residual
locktime
psr
reject code
*xx
[CR][LF]
†
Data Description
Log header
GPS week number
GPS seconds into the week (receiver time, not corrected for clock error,
CLOCKADJUST enabled)
Solution status (see Table 5-2, page 65)
Number of receiver channels with information to follow
Satellite PRN number (1-32) (channel 1)
Channel tracking state (See Table 5-1, page 65)
Instantaneous carrier Doppler frequency, in Hz
Carrier to noise density ratio in dB/Hz
Residual from position filter (cf $SATA) (metres)
Number of seconds of continuous tracking (no cycle slips)
Pseudorange measurement, in metres
Indicates that the range is being used in the solution (code 0) or that it was
rejected (code 1-11), as shown in Table 5-7 GPSCard Range Reject Codes
Next PRN (channel 2)
..
(channel n)
Checksum
Sentence terminator
Example
$CTSA
791
242805.0
0
0
12
28
4
-72.4
0.000
0.000
0.0
0.00
1
*2C
[CR][LF]
Example:
$CTSA,791,242805.00,0,12,28,4,-72.4,0.000,0.000,0.0,0.00,1,29,4,-3457.7,
42.684,4.451,2271.3,23182218.85,0,22,4,-3644.9,34.142,0.782,2278.5,
25139342.49,0,18,4,-2364.9,47.428,-10.199,2232.9,21086400.04,0,31,4,
2294.5,44.457,-8.949,2192.1,22192637.97,0,2,4,3389.9,36.117,10.247,
680.1,24886405.46,0,17,1,474.9,0.000,0.000,0.0,0.00,1,26,0,-1833.9,
0.000,0.000,0.0,0.00,1,19,4,475.7,47.985,24.028,2232.4,20162343.19,0,16,4,
867.9,42.432,2.895,2245.5,23437731.14,0,27,4,2712.0,46.145,-23.226,2278.5,
21867641.20,0,2,0,4756.9,0.000,0.000,0.0,0.00,1*2C[CR][LF]
† REMEMBER: The maximum number of tracking channels depends on your GPSCard specific model type. If you
are using a 12 channel GPSCard with the setchan command set to “10”, then this log will only report on the first 10
channels.
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
CTSB
Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11
12
13
14 ...
Message ID = 19
Message byte count = 32 + (n*52) where n is number of channels in receiver
Data
Sync
Checksum
Message ID
Message byte count
Week number
Time of week
Solution status
No. of channels †
PRN number (chan 0)
Channel tracking state
Doppler
C/NO (db-Hz)
Residual
Locktime
Pseudorange
Rejection code
Offset = 32 + (chan * 52) where chan varies from 0 – 11
Bytes
3
1
4
4
4
8
4
4
4
4
8
8
8
8
8
4
Format
char
char
integer
integer
integer
double
integer
integer
integer
integer
double
double
double
double
double
integer
Units
weeks
seconds
(See Table 5-2, page 65)
number of channels in receiver
(See Table 5-1, page 65)
Hz
db/Hz
metres
seconds
metres
(See SATA, Table 5-7, page 103)
Offset
0
3
4
8
12
16
24
28
32
36
40
48
56
64
72
80
Table 5-1 GPSCard Channel Tracking States
State
0
1
2
3
4
5
Description
Idle
Sky searching
Wide band frequency pull-in
Narrow band frequency pull-in
Phase lock loop achieved
Reacquisition
Higher numbers are reserved for future use
Table 5-2 GPSCard Solution Status
Value
0
1
2
3
4
5
6
7
Description
Solution computed
Insufficient observations
No convergence
Singular AtPA Matrix
Covariance trace exceeds maximum (trace > 1000 m)
Test distance exceeded (maximum of 3 rej if distance > 10 km)
Not yet converged from cold start
Height or velocity limit exceeded. (In accordance with COCOM export licensing restrictions)
Higher numbers are reserved for future use
GPSCard™ Command Descriptions Manual Rev 3
65
5 – NovAtel Format Data Logs
Table 5-3 Position Type
Type
0
1
2
3
4
5
Definition
No position
Single point position
Differential pseudorange position
RT-20 position
RT-2 position
WAAS position solution
Higher numbers are reserved for future use
Table 5-4 RTK Status for Position Type 3 (RT-20)
Status
0
1
2
3
4
5
6
7
8
Definition
Floating ambiguity solution (converged)
Floating ambiguity solution (not yet converged)
Modeling reference phase
Insufficient observations
Variance exceeds limit
Residuals too big
Delta position too big
Negative variance
RTK position not computed
Higher numbers are reserved for future use
DCSA/B
R
Pseudorange Differential Corrections
This log can be transmitted or received by any GPSCard with the “R” option. The log contains pseudorange and rangerate corrections as computed by the GPSCard operating in reference mode.
Before the GPSCard reference station can correctly log this data, it must be operating in “reference mode” by utilizing the
FIX POSITION command. As well, the reference GPSCard must be tracking at least three healthy SVs before the log
will be correctly transmitted.
The log will contain a variable number of fields, depending on the number of healthy SVs being tracked. However, any
SVs locked out by the LOCKOUT command, or any SVs designated with bad health with the SETHEALTH command,
will not be reported in this log.
NOTES: The DCSA/B log is specific to NovAtel cards and cannot be interpreted by GPS receivers supplied by other
manufacturers.
As the checksum of the DCSB log is 1 byte, there is a 1 in 255 possibility that a complete DCSB log will contain an error.
In previous software releases, this log was recommended as the most efficient differential format because the DCSB
format most closely matches the internal data structure of the GPSCard receiver, and requires minimal CPU power to
process. However with the introduction of the RTCA Standard, the RTCA log is now the recommended format for
greatest efficiency combined with data integrity.
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
DCSA
This log is transmitted, in NovAtel ASCII format, by the GPSCard reference station. The data can be directly interpreted
by a GPSCard remote station as a special data input command $DCSA. The remote receiver must have the ACCEPT
command set to ACCEPT port COMMANDS (default setting).
Structure:
$DCSA
prn
week
seconds
station ID
iode
diff cor
cor rate
iode
diff cor
cor rate
# obs
:
prn
Field #
1
2
3
4
5
6
7
8
9
10 – 13
variable
variable
variable
Field type
$DCSA
week
seconds
station id
# obs
prn
iode
diff cor
cor rate
...
...
*xx
[CR][LF]
*xx [CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week
Reference station ID
Number of valid satellite observations with information to follow:
Satellite PRN number (1-32)
Issue of data for the current ephemeris being used
Differential range correction, in metres
Differential correction rate of change, in m/s
Next PRN (4 fields) ...
Last PRN
Checksum
Sentence terminator
Example
$DCSA
653
338608.50
0
8
18
224
-43.054
0.203
*36
[CR][LF]
Example:
$DCSA,653,338608.50,0,8,18,224,-43.054,0.203,3,109,8.014,-0.262,13,193,
-28.666,-0.240,25,135,-0.389,-0.128,16,63,7.748,0.248,24,98,-32.389,
0.165,12,72,-23.717,-0.251,20,176,59.575,-0.786*36[CR][LF]
GPSCard™ Command Descriptions Manual Rev 3
67
5 – NovAtel Format Data Logs
DCSB
The DCSB differential correction log data can be interpreted by other NovAtel GPSCard receivers operating as a remote
station. The remote station must be initialized by using the ACCEPT port DCSB command before it will interpret the
DCSB data.
Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
10...
Message ID = 09
Message byte count = 32 + (#obs*24)
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
Station ID
Number of correction sets to follow (obs)
PRN, 1-32 (obs 0)
IODE
Correction
Correction rate of change
Next PRN offset = 32 + (obs * 24) where obs
varies from 0 to (obs-1)
Bytes
3
1
4
4
4
8
4
4
4
4
8
8
Format
char
char
integer
integer
integer
double
integer
integer
integer
integer
double
double
Units
bytes
weeks
seconds
metres
m/s
Offset
0
3
4
8
12
16
24
28
32
36
40
48
CAUTION: The DCSB message only has an 8-bit error-check value. Because of this, it is not recommended for use
over broadcast transmissions where the bit error rate could be high (i.e., > 10-3). The most reliable data integrity format
for differential correction broadcast is RTCA.
REMEMBER: When the accept port DCSB command is issued, the port specified will be dedicated to interpret only
DCSB differential corrections input data; all other commands and differential data types to the port will be ignored.
However pass-through data will still be accepted but not interpreted by the GPSCard port command interpreter.
For further information about the DCSA/B logs, refer to Chapter 10, page 139.
DOPA/B
B
Dilution of Precision
The dilution of precision data is calculated using the geometry of only those satellites that are currently being tracked and
used in the position solution by the GPSCard and updated once every 60 seconds or whenever a change in the
constellation occurs. Therefore, the total number of data fields output by the log is variable, depending on the number of
SVs tracking. Twelve is the maximum number of SV PRNs contained in the list.
NOTE: If a satellite is locked out using the LOCKOUT command, it will still be shown in the prn list, but is
significantly deweighted in the DOP calculation.
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
DOPA
Structure:
$DOPA
*xx
week
seconds
gdop
pdop
htdop
hdop
tdop
# sats prn list
[CR][LF]
Field #
1
2
3
4
Field type
$DOPA
week
seconds
gdop
5
6
pdop
htdop
7
hdop
8
9
10...
variable
variable
tdop
# sats
prn list
*xx
[CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week
Geometric dilution of precision - assumes 3-D position and receiver clock offset (all 4 parameters)
are unknown
Position dilution of precision - assumes 3-D position is unknown and receiver clock offset is known
Horizontal position and time dilution of precision - assumes height is known if the FIX HEIGHT
command has been invoked. If not, it will give the normalized precision of the horizontal and time
parameters given that nothing has been constrained.
Horizontal dilution of precision - makes no constraint assumptions about time, and about height only
if the FIX HEIGHT command has been invoked.
Time dilution of precision - assumes 3-D position is known and only receiver clock offset is unknown
Number of satellites used in position solution (0-12)
PRN list of SV PRNs tracking (1-32), null field until first position solution available
Checksum
Sentence terminator
Example
$DOPA
637
512473.00
2.9644
2.5639
2.0200
1.3662
1.4880
6
18,6,11,2,16,19
*29
[CR][LF]
Example:
$DOPA,637,512473.00,2.9644,2.5639,2.0200,1.3662,1.4880,6,18,6,11,2,16,19
*29[CR][LF]
DOPB
Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11...
Message ID = 07
Message byte count = 68+(sats*4)
Data
Bytes
Sync
3
Checksum
1
Message ID
4
Message byte count
4
Week number
4
Seconds of week
8
gdop
8
pdop
8
htdop
8
hdop
8
tdop
8
Number of satellites used
4
1st PRN
4
Next satellite PRN Offset = 68 + (sats*4) where sats = 0 to (number of sats-1)
GPSCard™ Command Descriptions Manual Rev 3
Format
char
char
integer
integer
integer
double
double
double
double
double
double
integer
integer
Units
bytes
weeks
seconds
Offset
0
3
4
8
12
16
24
32
40
48
56
64
68
69
5 – NovAtel Format Data Logs
FRMA/B
B
Framed Raw Navigation Data
This message contains the raw framed navigation data. An individual message is sent for each PRN being tracked. The
message is updated with each new frame, therefore it is best to log the data with the ‘onnew’ trigger activated.
FRMA
Structure:
$FRMA
*xx
Field #
1
2
3
4
5
6
week
seconds
prn
cstatus
# of bits
framed raw data
[CR][LF]
Field type
$FRMA
week
seconds
prn
cstatus
# of bits
7
framed raw data
Data Description
Log header
GPS week number
GPS seconds into the week
PRN of satellite from which data originated
Channel Tracking Status (see Table 5-6, page 95)
Number of bits transmitted in the message. 250 for WAAS, 300 for
GPS and 85 for GLONASS.
One field of raw framed navigation data.
8
9
*xx
[CR][LF]
Checksum
Sentence terminator
Example
$FRMA
845
238623.412
120
80811F14
250
9AFE5354656C2053796E6368726F6E6963
6974792020202020202020B0029E40*3F
*42
[CR][LF]
FRMB
Format:
Field #
1
(header)
Message ID = 54
2
3
4
5
6
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
PRN number
Channel Tracking Status (see Table 5-1, page 65)
Number of Bits
7
Data Sub-frame
FRWA/B
Bytes
3
1
4
4
4
8
4
4
4
variable
Framed Raw Navigation Words
Message byte count = variable
Format
char
char
integer
integer
integer
double
integer
integer
integer
char
Units
bytes
weeks
seconds
1-999
n/a
250 for WAAS
300 for GPS
85 for GLONASS
N/A
Offset
0
3
4
8
12
16
24
28
32
36
B
This message contains the raw framed navigation words. An individual message is sent for each PRN being tracked. The
message is updated with each new word, therefore it is best to log the data with the ‘onnew’ trigger activated.
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
FRWA
Structure:
$FRWA
*xx
week
seconds
prn
cstatus
# of bits
framed raw data
[CR][LF]
Field
1
2
3
4
5
6
Data
header
week
seconds
PRN
channel status
nav word
Example
$FRWA
845
238626.672
16
80811F14
FEEFF00F
Data Description
ASCII log header
GPS week number
GPS Seconds into the week first bit of word received
PRN number of satellite data is from
Channel tracking status of channel tracking this satellite
2 bits of previous word + 30 bits of new nav word
FRWB
Field
1
2
3
4
5
6
Data
header
week
seconds
PRN
channel status
2+30 bit word
Bytes
12
4
8
4
4
4
Format
bytes
integer
double
integer
integer
integer
Offset
0
12
16
24
28
32
Example:
$FRWA,0,28.982,19,EB4,C016FBBE*45
NOTES:
-
Each log will contain a new 30 bit nav word (in the least significant 30 bits), plus the last 2 bits of the previous word
(in the most significant 2 bits). The 30 bit nav word contains 24 bits of data plus 6 bits of parity.
-
The time stamp is the GPS time that the first bit of the 30 bit nav word was received. Only navigation data that
passes parity checking will appear in this log.
-
One log will appear for each PRN tracking every 0.6 seconds if logged ONNEW or ONCHANGED.
-
Both ASCII and binary versions will be provided ($FRWA, $FRWB), but they will not be supported by NovAtel’s
convert utility.
GPSCard™ Command Descriptions Manual Rev 3
71
5 – NovAtel Format Data Logs
GGAB
B (R)
Global Position System Fix Data (Binary Format)
Time, position and fix-related data of the GPS receiver. This binary log is a replica of the NMEA GPGGA ASCII log
expressed in binary format with NovAtel header added.
Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11
MKPA/B
Message ID = 27
Message byte count = 80
Data
Sync
Checksum
Message ID
Message byte count
UTC time of position
Latitude (DDmm.mm)
(+ is North, - is South)
Longitude (DDDmm.mm)
(+ is East, - is West)
Fix status
0 = fix not available or invalid
1 = GPS fix
†
2 = DifferentialGPS fix
Number of satellites in use. May be different to the number in view
Horizontal dilution of precision
Antenna altitude above/below mean-sea-level (geoid)
Geoidal separation
†
††
Age of Differential GPS data
†
Differential reference station ID, 0000-1023
Bytes
3
1
4
4
8
8
Format
char
char
integer
integer
double
double
Units
8
double
degrees
4
integer
36
4
8
8
8
8
4
integer
double
double
double
double
integer
40
44
52
60
68
76
†
Fields 5, 10, and 11 will not report this data unless the GPSCard has the (R) option.
††
The maximum age reported here is limited to 99 seconds.
Mark Position
bytes
hhmmss.ss
degrees
metres
metres
seconds
Offset
0
3
4
8
12
20
28
B
This log contains the estimated position of the antenna at detected mark impulse. It uses the last valid position and
velocities to extrapolate the position at time of mark. Refer to the “GPSCard Installation and Operating Manual
Appendix” for Mark Input pulse specifications. The latched time of mark impulse is in GPS weeks and seconds into the
week. The resolution of the latched time is 49 nsec.
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
MKPA
Structure:
$MKPA
week
sol status
Field #
1
2
3
seconds
*xx
Field type
$MKPA
week
seconds
4
lat
5
lon
6
7
8
9
10
11
12
13
14
hgt
undulation
datum ID
lat std
lon std
hgt std
sol status
*xx
[CR][LF]
lat
lon
hgt
undulation
datum ID
lat std
lon std
hgt std
[CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week measured from the receiver clock, coincident with the time of
electrical closure on the Mark Input port.
Latitude of position in current datum, in degrees/decimal degrees (DD.dddddddd), where a
negative sign implies South latitude
Longitude of position in current datum, in degrees/decimal degrees (DDD.dddddddd), where a
negative sign implies West longitude
Height of position in current datum, in metres above MSL
Geoid undulation, in metres
Current datum (see Table A-2, page 166) I.D. #
Standard deviation of latitude solution element, in metres
Standard deviation of longitude solution element, in metres
Standard deviation of height solution element, in metres
Solution status as listed in Table 5-2, page 65
Checksum
Sentence terminator
Example
$MKPA
653
338214.773382376
51.11227014
-114.03907552
1003.799
-16.199
61
7.793
3.223
34.509
0
*3C
[CR][LF]
Example:
$MKPA,653,338214.773382376,51.11227014,-114.03907552,1003.799,-16.199,61,
7.793,3.223,34.509,0*3C[CR][LF]
MKPB
Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11
12
Message ID = 05
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
Latitude
Longitude
Height
Undulation
Datum ID
StdDev of latitude
StdDev of longitude
StdDev of height
Solution status
Message byte count = 88
Bytes
3
1
4
4
4
8
8
8
8
8
4
8
8
8
4
GPSCard™ Command Descriptions Manual Rev 3
Format
char
char
integer
integer
integer
double
double
double
double
double
integer
double
double
double
integer
Units
bytes
weeks
seconds
degrees (+ is North, - is South)
degrees (+ is East, - is West)
metres above MSL
metres
see Table A-2, page 166
metres
metres
metres
see Table 5-2, page 65
Offset
0
3
4
8
12
16
24
32
40
48
56
60
68
76
84
73
5 – NovAtel Format Data Logs
MKTA/B
B
Time of Mark Input
This log contains the time of the detected Mark Input pulse leading edge as detected at the Mark Input I/O port. The
resolution of this measurement is 49 ns. Refer to the “GPSCard Installation and Operating Manual Appendix” for the
Mark Input pulse specifications.
MKTA
Structure:
$MKTA
Field #
1
2
3
week
seconds
Field type
$MKTA
week
seconds
4
offset
5
6
offset std
utc offset
7
cm status
8
9
*xx
[CR][LF]
offset
offset std
utc offset cm status
*xx
Data Description
Log header
GPS week number
Seconds into the week as measured from the receiver clock, coincident with the time of
electrical closure on the Mark Input port.
Receiver clock offset, in seconds. A positive offset implies that the receiver clock is ahead
of GPS Time. To derive GPS time, use the following formula:
GPS time = receiver time – (offset)
Standard deviation of receiver clock offset, in seconds
This field represents the offset of GPS time from UTC time, computed using almanac
parameters. To reconstruct UTC time, algebraically subtract this correction from field 3
above (GPS seconds).
UTC time = GPS time – (utc offset)
Receiver Clock Model Status where 0 is valid and values from -20 to -1 imply that the model
is in the process of stabilization
Checksum
Sentence terminator
[CR][LF]
Example
$MKTA
653
338214.773382376
0.000504070
0.000000013
-8.000000000
0
*05
[CR][LF]
Example:
$MKTA,653,338214.773382376,0.000504070,0.000000013,-8.000000000,0 *05[CR][LF]
MKTB
Format:
Field #
1
(header)
2
3
4
5
6
7
74
Message ID = 04
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
Clock offset
StdDev clock offset
UTC offset
Clock model status
Message byte count = 52
Bytes
3
1
4
4
4
8
8
8
8
4
Format
char
char
integer
integer
integer
double
double
double
double
integer
Units
bytes
weeks
seconds
seconds
seconds
seconds
0 = good, -1 to -20 = bad
Offset
0
3
4
8
12
16
24
32
40
48
GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
NAVA/B
B
Waypoint Navigation Data
This log reports the status of your waypoint navigation progress. It is used in conjunction with the SETNAV command.
REMEMBER: The setnav command must be enabled before valid data will be reported from this log.
NAVA
Structure:
$NAVA
week
nav status
Field #
1
2
3
4
seconds
distance
sol status
Field type
$NAVA
week
seconds
distance
5
bearing
6
distance
7
xtrack
8
etaw
9
etas
10
11
12
13
nav status
sol status
*xx
[CR][LF]
bearing
distance
xtrack etaw
etas
*xx [CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week
Straight line horizontal distance from current position to the destination waypoint, in metres (see
SETNAV command, Chapter 2; Figure 2-6, page 46)
Direction from the current position to the destination waypoint in degrees with respect to True North
(or Magnetic if corrected for magnetic variation by MAGVAR command)
Horizontal track distance from the current position to the closest point on the waypoint arrival
perpendicular; expressed in metres
The horizontal distance (perpendicular track-error) from the vessel’s present position to the closest
point on the great circle line that joins the FROM and TO waypoints. If a "track offset" has been
entered in the SETNAV command, xtrack will be the perpendicular error from the "offset track".
Xtrack is expressed in metres. Positive values indicate the current position is right of the Track,
while negative offset values indicate left.
Estimated GPS week number at time of arrival at the "TO" waypoint along-track arrival
perpendicular based on current position and speed, in units of GPS weeks. If the receiving antenna
is moving at a speed of less than 0.1 m/sec in the direction of the destination, the value in this field
will be “9999”.
Estimated GPS seconds into week at time of arrival at destination waypoint along-track arrival
perpendicular, based on current position and speed, in units of GPS seconds into the week. If the
receiving antenna is moving at a speed of less than 0.1 m/sec in the direction of the destination, the
value in this field will be “0.000”.
Navigation data status, where 0 = good, 1 = no velocity, and 2 = bad navigation calculation
Solution status as listed in Table 5-2, page 65
Checksum
Sentence terminator
Example
$NAVA
640
333115.00
6399.6305
88.017
6396.9734
184.3929
657
51514.000
0
1
*11
[CR][LF]
Example:
$NAVA,640,333115.00,6399.6305,88.017,6396.9734,184.3929,657,51514.000,0,1
*11[CR][LF]
NOTE: All distances and angles are calculated using Vincenty’s long line geodetic equations that operate on the
currently selected user datum.
GPSCard™ Command Descriptions Manual Rev 3
75
5 – NovAtel Format Data Logs
NAVB
Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11
76
Message ID = 08
Message byte count = 76
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
Distance
Bearing
Along track
Xtrack
ETA week
ETA seconds
NAV status where 0 = good, 1 = no velocity, 2 = bad navigation
Solution status
Bytes
3
1
4
4
4
8
8
8
8
8
4
8
4
4
Format
char
char
integer
integer
integer
double
double
double
double
double
integer
double
integer
integer
Units
bytes
weeks
seconds
metres
degrees
metres
metres
weeks
seconds
see Table 5-2, page 65
Offset
0
3
4
8
12
16
24
32
40
48
56
60
68
72
GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
Figure 5-1 Example of Navigation Parameters
True North
Magnetic North
Arrival Perpendicular
Variation
* local MAGVAR CORRECTION = -208
if magnetic bearings required
20
B
TO,
lat-lon
50
G
70
F
FROM,
D
X
A
lat-lon
E
C
A
B
AB
AC
BD
CD
F
FD
E
EF
FG
=
=
=
=
=
=
=
=
=
=
=
AB –
AB –
FROM lat-lon
TO lat-lon
Great circle line drawn between FROM A lat-lon and TO B lat-lon
Track offset from A to C
Track offset from B to D
Offset track to steer (parallel to AB)
Current GPS position
Current distance and bearing from F to D
Xtrack perpendicular reference point
Xtrack error from E to F (perpendicular to CD)
Along track from F to G (perpendicular to BD)
True bearing
Magnetic bearing
GPSCard™ Command Descriptions Manual Rev 3
=
=
=
=
70°
True + (MAGVAR correction)
70° + (-20)
50°
77
5 – NovAtel Format Data Logs
P20A/B
B (R) (RT20)
Computed Position – Best Available
This log contains the best available position computed by the receiver, along with three status flags. In addition, it reports
other status indicators, including differential lag, which is useful in predicting anomalous behavior brought about by
outages in differential corrections. GPSCards with the RT-20 option are limited to a maximum logging rate of 5 Hz.
P20A
Structure:
$P20A
week
lon std
seconds diff lag
hgt std
Field #
1
2
3
4
5
6
7
Field type
$P20A
week
seconds
†
diff lag
# sats
lat
lon
8
9
10
11
12
13
14
15
16
hgt
undulation
datum ID
lat std
lon std
hgt std
sol status
rt20 status††
fix stat
17
% idle
18
19
20
stn ID
*xx
[CR][LF]
†
# sats
lat lon hgt undulation datum ID lat std
sol status rt20 status
fix stat
% idle stn ID *xx [CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week
Age of differential correction (seconds) (= 0 if fix status - 2)
Number of satellites in use (00-12). May be different to the number in view.
Latitude of position in current datum, in degrees (DD.dddddddd). A negative sign implies South latitude.
Longitude of position in current datum, in degrees (DDD.dddddddd). A negative sign implies West
longitude
Height of position in current datum, in metres above mean sea level (MSL) (see Figure 5-2, page 79)
Geoidal separation, in metres, where positive is above spheroid and negative is below spheroid
Current datum ID # (see Table A-2, page 166)
Standard deviation of latitude solution element, in metres
Standard deviation of longitude solution element, in metres
Standard deviation of height solution element, in metres
Solution status as listed in Table 5-2, page 65
RT20 status as listed in Table 5-4 RTK Status for Position Type 3 (RT-20)
Fix status indicator
0 =fix not available or invalid
1 =single point
†
2 =differential fix
An integer number representing percent idle time for the CPU, with a valid range of 0 to 99. (System
performance degrades when idle time is < 10%.)
Differential reference station ID, 0000-1023
Checksum
Sentence terminator
†
Fields 4, 16 and 18 will not report differential data unless the GPSCard has the “R” option.
††
Field 15 will always report an “8” unless the GPSCard has the “RT-20” option.
Example
$P20A
779
237330.00
2.000
9
51.11411139
-114.04302698
1058.566
-16.263
61
0.016
0.016
0.016
0
0
2
7
200
*16
[CR][LF]
Example:
$P20A,779,237330.00,2.000,9,51.11411139,-114.04302698,1058.566,-16.263,61,
0.016,0.016,0.016,0,0,2,7,200*16[CR][LF]
78
GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
Figure 5-2 Illustration of GPSCard Height Measurements
GPSCard™ Command Descriptions Manual Rev 3
79
5 – NovAtel Format Data Logs
P20B
Format:
Message ID = 37
Field #
1
(header)
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
†
Differential lag
Number of sats in solution
Latitude
Longitude
Height
Undulation
Datum ID
StdDev of latitude
StdDev of longitude
StdDev of height
Solution status
††
RT20 status
Fix status indicator
0=
fix not available or invalid
1=
single point
†
2=
differential fix
CPU idle time
Reference station ID
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
PAVA/B
Message byte count = 116
Bytes
3
1
4
4
4
8
8
4
8
8
8
8
4
8
8
8
4
4
4
†
4
4
Format
char
char
integer
integer
integer
double
double
integer
double
double
double
double
integer
double
double
double
integer
integer
integer
integer
integer
Units
bytes
weeks
seconds
seconds
degrees (+ is North, - is South)
degrees (+ is East, - is West)
metres with respect to MSL
metres
see Table A-2, page 166
metres
metres
metres
see Table 5-2, page 65
see Table 5-4, page 66
percent
Offset
0
3
4
8
12
16
24
32
36
44
52
60
68
72
80
88
96
100
104
108
112
B
Position Averaging Status
These logs are meant to be used in conjunction with the posave command. If the posave command has not been issued, all
fields in the PAVA/B logs except week and seconds will be zero. However, when position averaging is underway, the
various fields contain the parameters being used in the position averaging process. The log trigger onchanged is
recommended, but ontime can also be used.
See the description of the POSAVE command, page 39.
NOTE: All quantities are referenced to the WGS84 ellipsoid, regardless of the use of the datum or userdatum
commands, except for the height parameter (field 6). The relation between the geoid and the WGS84 ellipsoid is the
geoidal undulation, and can be obtained from the POSA/B logs.
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
PAVA
Structure :
$PAVA
sdhgt
Field #
1
2
3
4
5
6
7
8
9
10
11
12
13
week
seconds lat
time
Field type
$PAVA
week
seconds
lat
lng
hgt
sdlat
sdlng
sdhgt
time
samples
*xx
[CR][LF]
samples
lng
hgt sdlat
*xx
sdlng
[CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week
Average WGS84 latitude (degrees)
Average WGS84 longitude (degrees)
Average height above sea level, or geoid (m)
Estimated standard deviation of the average latitude (m)
Estimated standard deviation of the average longitude (m)
Estimated standard deviation of the average height (m)
Elapsed time of averaging (s)
Number of samples in the average
Checksum
Sentence terminator
Example
$PAVA
846
145872.00
51.11381167
-114.04356455
1068.100
26.2
12.1
54.9
7
1
*0C
[CR][LF]
Example:
$PAVA,846,145872.00,51.11381167,114.04356455,1068.100,26.2,12.1,54.9,7,1*0C [CR][LF]
PAVB
Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11
Message ID = 50 Message byte count = 80
Data
Sync
Checksum
Message ID
Message byte count
GPS week number
GPS seconds into the week
Average WGS84 latitude
Average WGS84 longitude
Average height above sea level
Estimated standard deviation of the average latitude
Estimated standard deviation of the average longitude
Estimated standard deviation of the average height
Elapsed time of averaging
Number of samples in the average
GPSCard™ Command Descriptions Manual Rev 3
Bytes
3
1
4
4
4
8
8
8
8
8
8
8
4
4
Format
char
char
integer
integer
integer
double
double
double
double
double
double
double
integer
integer
Units
weeks
seconds
degrees
degrees
meters
meters
meters
meters
seconds
Offset
0
3
4
8
12
16
24
32
40
48
56
64
72
76
81
5 – NovAtel Format Data Logs
POSA/B
B
Computed Position
This log will contain the last valid position and time calculated referenced to the GPSAntenna phase center. The position
is in geographic coordinates in degrees based on your specified datum (default is WGS-84). The height is referenced to
mean sea level. The receiver time is in GPS weeks and seconds into the week. The estimated standard deviations of the
solution and current filter status are also included.
POSA
Structure:
$POSA
week
hgt std
Field #
1
2
3
4
seconds
sol status
Field type
$POSA
week
seconds
lat
5
lon
6
hgt
7
undulation
8
9
10
11
12
13
14
datum ID
lat std
lon std
hgt std
sol status
*xx
[CR][LF]
lat lon hgt undulation
datum ID
lat std
lon std
*xx [CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week
Latitude of position in current datum, in degrees (DD.dddddddd). A negative sign
implies South latitude
Longitude of position in current datum, in degrees (DDD.dddddddd). A negative
sign implies West longitude
Height of position in current datum, in metres above mean sea level (MSL) (see
Figure 5-2, page 79)
Geoidal separation, in metres, where positive is above spheroid and negative is
below spheroid
Current datum ID # (see Table A-2, page 166)
Standard deviation of latitude solution element, in metres
Standard deviation of longitude solution element, in metres
Standard deviation of height solution element, in metres
Solution status as listed in Table 5-2, page 65
Checksum
Sentence terminator
Example
$POSA
637
511251.00
51.11161847
-114.03922149
1072.436
-16.198
61
26.636
6.758
78.459
0
*12
[CR][LF]
Example:
$POSA,637,511251.00,51.11161847,-114.03922149,1072.436,-16.198,61,26.636,
6.758,78.459,0*12[CR][LF]
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
POSB
Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11
12
Message ID = 01
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
Latitude
Longitude
Height
Undulation
Datum ID
StdDev of latitude
StdDev of longitude
StdDev of height
Solution status
PRTKA/B
Message byte count = 88
Bytes
3
1
4
4
4
8
8
8
8
8
4
8
8
8
4
Format
char
char
integer
integer
integer
double
double
double
double
double
integer
double
double
double
integer
Computed Position
Units
bytes
weeks
seconds
degrees (+ is North, - is South)
degrees (+ is East, - is West)
metres with respect to MSL
metres
see Table A-2, page 166
metres
metres
metres
see Table 5-2, page 65
Offset
0
3
4
8
12
16
24
32
40
48
56
60
68
76
84
(RTK)
This log contains the best available position computed by the receiver, along with three status flags. In addition, it reports
other status indicators, including differential lag, which is useful in predicting anomalous behavior brought about by
outages in differential corrections.
This log replaces the P20A log; it is similar, but adds extended status information. With the system operating in an RTK
mode, this log will reflect the latest low-latency solution for up to 30 seconds after reception of the last reference station
observations. After this 30 second period, the position reverts to the best solution available; the degradation in accuracy is
reflected in the standard deviation fields, and is summarized in Table 10-3, page Error! Bookmark not defined.. If the
system is not operating in an RTK mode, pseudorange differential solutions continue for 60 seconds after loss of the data
link, though a different value can be set using the dgpstimeout command.
GPSCard™ Command Descriptions Manual Rev 3
83
5 – NovAtel Format Data Logs
PRTKA
Structure:
$PRTKA
week
lon
hgt
rtk status
posn type
Field #
1
2
3
4
5
6
Field type
$PRTKA
week
sec
lag
#sv
#high
7
8
L1L2 #high
lat
9
lon
10
11
12
13
14
15
16
17
18
19
20
21
22
hgt
undulation
datum ID
lat s
lon s
hgt s
soln status
rtk status
posn type
idle
stn ID
*xx
[CR][LF]
sec
undulation
idle
lag
#sv
#high
L1L2 #high
lat
datum ID
lat s
lon s
hgt s
soln status
stn ID
*xx
[CR][LF]
Data Description
Log header
GPS week number
GPS time into the week (in seconds)
Differential lag in seconds
Number of matched satellites; may differ from the number in view.
Number of matched satellites above RTK mask angle; observations from satellites below
mask are heavily de-weighted
Unused, will report 0
Latitude of position in current datum, in decimal fraction format. A negative sign implies
South latitude
Longitude of position in current datum, in decimal fraction format. A negative sign implies
West longitude
Height of position in current datum, in meters above mean sea level
Geoidal separation, in meters, where(+ve) is above ellipsoid and (-ve) is below ellipsoid
Current datum (See Appendix A, page 166)
Standard deviation of latitude solution element, in meters
Standard deviation of longitude solution element, in meters
Standard deviation of height solution element, in meters
Solution status (see Table 5-2, page 65)
RTK status (see Table 5-3, page 66)
Position type (see Table 5-3, page 66)
Percent idle time, percentage
Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385)
Checksum
Sentence terminator
Example
$PRTKA
872
174963.00
1.000
8
7
0
51.11358042429
-114.04358006710
1059.4105
-16.2617
61
0.0096
0.0100
0.0112
0
0
4
42
119
*51
[CR][LF]
Example:
$PRTKA,872,174963.00,1.000,8,7,0,51.11358042429,
-114.04358006710,1059.4105,
-16.2617,61,0.0096,0.0100,0.0112,0,0,4,42,119*51[CR][LF]
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
PRTKB
Format:
Message ID = 63
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
PXYA/B
Message byte count = 124
Data
Sync
Checksum
Message ID
Message byte count
Week number
GPS time into the week
Differential lag
Number of matched satellites (00-12)
Number of matched satellites above RTK mask angle
Unused, will report 0
Latitude
Longitude
Height above mean sea level
Undulation
Datum ID
Standard deviation of latitude
Standard deviation of longitude
Standard deviation of height
Solution status (see Table 5-2, page 65)
RTK status (see Table 5-4, page 66)
Position type (see Table 5-3, page 66)
Idle
Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385)
Computed Cartesian Coordinate Position
Bytes
3
1
4
4
4
8
8
4
4
4
8
8
8
8
4
8
8
8
4
4
4
4
4
Format
char
char
integer
integer
integer
double
integer
integer
integer
double
double
double
double
integer
double
double
double
integer
integer
integer
integer
integer
Units
weeks
seconds
seconds
degrees
degrees
meters
meters
meters
meters
meters
Offset
0
3
4
8
12
16
24
32
36
40
44
52
60
68
76
80
88
96
104
108
112
116
120
B (R)
This log contains the last valid position, expressed in Cartesian x-y-z space coordinates, relative to the center of the Earth.
The positions expressed in this log are always relative to WGS-84 regardless of the setting of the DATUM or
USERDATUM command. Refer to Figure 5-3, page 108, for a definition of the coordinates.
GPSCard™ Command Descriptions Manual Rev 3
85
5 – NovAtel Format Data Logs
PXYA
Structure:
$PXYA
week
diff lag
Field #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
seconds
*xx
Field type
$PXYA
week
seconds
x
y
z
x std
y std
z std
sol status
fix status
diff lag
*xx
[CR][LF]
x
y
z
x std
y std
z std
sol status
fix status
[CR][LF]
†
Data Description
Log header
GPS week number
GPS seconds into the week
Position x coordinate, in metres
Position y coordinate, in metres
Position z coordinate, in metres
Standard deviation of x, in metres
Standard deviation of y, in metres
Standard deviation of z, in metres
Solution status as listed in Table 5-2
0 = fix not available or invalid
1 = Single point standalone fix
†
2 = Differential fix
(only available with the “R” option)
Age of differential correction (seconds) (= 0 if fix status - 2)
Checksum
Sentence terminator
Example
$PXYA
713
488150.00
-1634756.995
-3664965.028
4942151.391
2.335
3.464
4.156
0
2
0.4
*08
[CR][LF]
† This log provides differential fix and lag status. The GPSCard must have the “R” option before fields 11 and 12 will report differential status.
Example:
$PXYA,713,488150.00,-1634756.995,-3664965.028,4942151.391,2.335,3.464,
4.156,0,2,0.4*08[CR][LF]
PXYB
Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11
12
86
Message ID = 26
Message byte count = 88
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
x
y
z
StdDev of x
StdDev of y
StdDev of z
Solution status
Fix status
Differential lag, age of differential corrections
†
†
Bytes
3
1
4
4
4
8
8
8
8
8
8
8
4
4
8
Format
char
char
integer
integer
integer
double
double
double
double
double
double
double
integer
integer
double
Units
bytes
weeks
seconds
metres
metres
metres
metres
metres
metres
see Table 5-2, page 65
seconds
Offset
0
3
4
8
12
16
24
32
40
48
56
64
72
76
80
GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
RALA/B
B
Raw Almanac
Almanac and health data are contained in subframes four and five of the satellite broadcast message. Subframe four
contains information for SVs 25-32, as well as ionospheric, UTC and SV configuration data. Subframe five contains
information for SVS 1-24.
Subframes four and five each contain 25 pages of data, and each page contains ten 30-bit words of information as
transmitted from the satellite. The RALA/B log outputs this information with parity bits checked and removed (ten
words - 24 bits each). The log will not be generated unless all ten words pass parity.
This log will alternately report each page from subframes four and five as they are collected. Logging this log onnew
would be the optimal logging rate to capture data from pages in subframes four and five as they are received.
RALA logs contain a hex representation of the raw almanac data (one of the possible 25 pages of either subframe 4 or 5).
RALB contains the raw binary information.
RALA
Structure:
$RALA
Field #
1
2
3
4
5
6
chan # prn subframe
*xx
[CR][LF]
Field type
$RALA
chan #
prn
subframe
Data Description
Log header
Channel number collecting almanac data (0-11)
PRN of satellite from which data originated
Subframe 4 or 5 of almanac data (60 hex characters)
*xx
[CR][LF]
Checksum
Sentence terminator
Example
$RALA
7
16
8B0A54852C964C661F086366FDBE00A
10D53DA6565F2503DD7C2AACBFED3
*05
[CR][LF]
Example:
$RALA,7,16,8B0A54852C964C661F086366FDBE00A10D53DA6565F2503DD7C2AACBFED3
*05[CR][LF]
RALB
Format:
Field #
1
(header)
2
3
4
5
Message ID = 15
Data
Sync
Checksum
Message ID
Message byte count
Channel number
PRN number
Almanac data
Filler bytes
Message byte count = 52
Bytes
3
1
4
4
4
4
30
2
Format
char
char
integer
integer
integer
integer
char
char
GPSCard™ Command Descriptions Manual Rev 3
Units
bytes
0-11
1-32
data [30]
Offset
0
3
4
8
12
16
20
50
87
5 – NovAtel Format Data Logs
RCCA
Receiver Configuration
B
This log outputs a list of all current GPSCard command settings. Observing this log is a good way to monitor the
GPSCard configuration settings. See Chapter 2, page 17, for the RCCA default list.
RCCA
Example:
$RCCA,COM1,9600,N,8,1,XON,OFF*11
$RCCA,COM2,9600,N,8,1,N,OFF*05
$RCCA,COM1_DTR,HIGH*70
$RCCA,COM2_DTR,HIGH*73
$RCCA,COM1_RTS,HIGH*67
$RCCA,COM2_RTS,HIGH*64
$RCCA,UNDULATION,TABLE*56
$RCCA,DATUM,WGS84*15
$RCCA,USERDATUM,6378137.000,298.257223563,0.000,0.000,0.000,0.000,0.000,0.000,
0.000*6A
$RCCA,SETNAV,DISABLE*5C
$RCCA,MAGVAR,0.000*33
$RCCA,DYNAMICS,HIGH*1B
$RCCA,UNASSIGNALL*64
$RCCA,ACCEPT,COM1,COMMANDS*5B
$RCCA,ACCEPT,COM2,COMMANDS*58
$RCCA,UNLOCKOUTALL*20
$RCCA,RESETHEALTHALL*37
$RCCA,UNFIX*73
$RCCA,RTCMRULE,6CR*32
$RCCA,RTCM16T,*48
$RCCA,CSMOOTH,20.00*7E
$RCCA,ECUTOFF,0.00*45
$RCCA,FREQUENCY_OUT,DISABLE*12
$RCCA,CLOCKADJUST,ENABLE*47
$RCCA,MESSAGES,ALL,ON*67
$RCCA,SETCHAN,12*56
$RCCA,DGPSTIMEOUT,60,120*51
$RCCA,SETDGPSID,ALL*1D
$RCCA,LOG,COM2,POSA,ONTIME,5.00,0.00*3D
RCSA/B
Receiver Status
B
The RCSA log will always output four records: one for VERSION, one for receiver CHANNELS, one for receiver CPU
IDLE time, and one indicating receiver self-test STATUS. However, RCSB will embed the same information in a single
record.
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
RCSA
Structure:
$RCSA
VERSION
sw ver
*xx
[CR][LF]
$RCSA
CHANNELS
# chans
*xx
[CR][LF]
$RCSA
IDLE
idle time
*xx
[CR][LF]
$RCSA
STATUS
rec status
*xx
[CR][LF]
Log
$RCSA
Data Identifier
VERSION
$RCSA
$RCSA
CHANNELS
IDLE
$RCSA
STATUS
Data Description
Checksum
sw ver:
.Software information indicating model, S/N, S/W version
*xx
and S/W version date
# chans:
Indicates number of parallel channels on GPSCard
*xx
idle time:
An integer number representing percent idle time for
*xx
the CPU, with a valid range of 0 to 99
rec status:
Indicates result of hardware self-test and software
*xx
status as shown in Table 5-4
String End
[CR][LF]
[CR][LF]
[CR][LF]
[CR][LF]
Example:
$RCSA,VERSION,GPSCard-2 3951R LGR94160001 HW 16 SW 3.15 Mar 31/94*16
$RCSA,CHANNELS,10*12
$RCSA,IDLE,40*03
$RCSA,STATUS,000007F6*60
The status code is a hexadecimal number representing the results of the GPSCard BIST test and software status. As an
example, the status code ’000000F6’ indicates that the GPSAntenna is not working properly or is disconnected and the
GPSCard is good, while ’000000F7’ indicates that the GPSAntenna and the GPSCard are both functioning properly.
Refer to Table 5-4, page 66, for a detailed description of the status code. Bit 0 is the least significant bit of the status
code and Bit 16 is the most significant bit.
RCSB
Format:
Message ID = 13
Data
Sync
Checksum
Message ID
Message byte count
Software version #
Number of receiver channels
CPU idle time
Filler
Self-test status
Bytes
3
1
4
4
80
1
1
2
4
Message byte count = 100
Format
char
char
integer
integer
char
char
char
bytes
integer
GPSCard™ Command Descriptions Manual Rev 3
Units
bytes
ASCII
percent
See Table 5-5, page 90
Offset
0
3
4
8
12
92
93
94
96
89
5 – NovAtel Format Data Logs
Table 5-5 GPSCard Receiver Self-test Status Codes
N7
N6
N5
N4
N3
N2
31 30 2 9 28 27 26 2 5 24 23 2 2 2 1 20 19 1 8 1 7 16 15 1 4 13 12 11 1 0 9
N1
8
7
6
5
N0
4
3
2
1
0
<- <- Nibble Number
Bit
Description
lsb = 0 ANTENNA
Range Values
Hex Value
1 = good, 0 = bad
00000001
1
2
3
4
PRIMARY PLL
RAM
ROM
DSP
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
00000002
00000004
00000008
00000010
5
6
PRIMARY AGC
COM 1
1 = good, 0 = bad
1 = good, 0 = bad
00000020
00000040
7
COM 2
1 = good, 0 = bad
00000080
8
9
WEEK
NO COARSETIME
1 = not set, 0 = set
1 = not set, 0 = set
00000100
00000200
10
11
NO FINETIME
PRIMARY JAMMER
1 = not set, 0 = set
1 = present, 0 = normal
00000400
00000800
12
13
14
15
BUFFER COM 1
BUFFER COM 2
BUFFER CONSOLE
CPUOVERLOAD
1 = overrun, 0 =normal
1 = overrun, 0 =normal
1 = overrun, 0 =normal
1 = overload, 0 = normal
00001000
00002000
00004000
00008000
16
ALMANACSAVED IN NVM
1 = yes, 0 = no
00010000
17
18
19
20
RESERVED
RESERVED
RESERVED
RESERVED
21
22
RESERVED
RESERVED
23
24
RESERVED
RESERVED
25
26
RESERVED
RESERVED
27
RESERVED
28
29
30
31
RESERVED
RESERVED
RESERVED
RESERVED
NOTE: Self-test bits 2, 3, 4, 6, 7 are set only once when the GPSCard is first powered up. All other bits are set by
internal test processes each time the RCSA/B log is output .
Receiver Status - Detailed Bit Descriptions of Self-Test
Bit 0
Antenna
1
This bit will be set good if the antenna is drawing the appropriate amount of current from the GPSCard antenna
jack.
0
If the antenna connections are shorted together, open, not drawing appropriate current, or not connected to the
antenna, then this bit will be clear (0) indicating a possible antenna port problem.
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
NOTE: If the user decides to use an alternate antenna not meeting the GPSCard power requirements or alternate power
to the antenna using a DC block, then this bit will set to 0 because the GPSCard detects an abnormal condition at the
antenna port. Providing that GPS signals are presented to the receiver, the GPSCard will operate normally. If you are
using an OEM card, and have set the external LNA jumper plug (P3) to the external position, then self-test bit 0 will
always be set to 1.
Bit 1
PLL
1
When the RF downconverter passes self-test, the bit will be set to 1.
0
If a fault is detected in the RF downconverter, this bit is set to 0.
Bit 2
RAM
1
When this bit is set to 1, the GPSCard RAM has passed the self-test requirements.
0
If the bit has been set to 0, then RAM test has failed and the GPSCard should be returned for service.
Bit 3
ROM
1
When this bit is set to 1, the GPSCard ROM test has passed the self-test requirements.
0
A zero bit indicates the GPSCard has failed the ROM test. (The GPSCard PC Series do not have built in ROM
and therefore a clear bit for this test is normal.)
Bit 4
DSP
1
This bit will be set to 1 when the digital signal processors (DSP) have passed the self-test requirements.
0
If this bit is set to 0, one or both of the DSP chips has failed self-test and the GPSCard should be returned for
service.
Bit 5
AGC
1
When set to 1, the AGC circuits are operating within normal range of control.
0
This bit will be set clear if the AGC is operating out of normal range. Intermittent setting of the AGC bit
indicates that the card is experiencing some electro-magnetic interference of a very short duration. Continuous
setting of the AGC bit may indicate that the card is receiving too much signal power from the antenna or that a
more serious problem with the card may exist. Failure of this test could be the result of various possibilities,
such as: bad antenna LNA, excessive loss in the antenna cable, faulty RF downconverter, or a pulsating or high
power jamming signal causing interference. If this bit is continuously set clear, and you cannot identify an
external cause for the failed test, please contact NovAtel Customer Service.
Bit 6
COM1
1
When set to 1, the COM1 UART has passed the self-test requirements.
0
If set to 0, the COM1 UART has failed self-test and cannot be used for reliable communications.
Bit 7
COM2
1
When set to 1, the COM2 UART has passed the self-test requirements.
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91
5 – NovAtel Format Data Logs
0
If set to 0, the COM2 UART has failed self-test and cannot be used for reliable communications.
Bits 8, 9, 10
Time
0
These bits indicate the state of the receiver time and are set only once, generally in the first few minutes of
operation, in the presence of adequate numbers of satellite signals to compute position and time.
1
If these bits are not all set to zero, then the observation data, pseudorange, carrier phase, and Doppler
measurements may jump as the clock adjusts itself.
Bit 11
Jammer Detection
0
Normal operation is indicated when this bit is 0.
1
If set to 1, the receiver has detected a high power signal causing interference. When this happens, the receiver
goes into a special anti-jamming mode where it re-maps the A/D decode values as well as special AGC feedback
control. These adjustments help to minimize the loss that will occur in the presence of a jamming signal. You
should monitor this bit, and if set to 1, do your best to remedy the cause of the jamming signal. Nearby
transmitters or other electronic equipment could be the cause of interference; you may find it necessary to
relocate your antenna position if the problem persists.
Bits 12, 13, 14
COM Buffers
0
Normal operation is indicated by a 0 value.
1
These bits are set to 1 to inform the user when any of the 8-Kbyte output buffers have reached an over-run
condition (COM1, COM2, or the PC console if applicable). Over-run is caused by requesting more log data than
can be taken off the GPSCard because of bit rate limitations or slow communications equipment. If this
happens, the new data attempting to be loaded into the buffer will be discarded. The GPSCard will not load a
partial data record into an output buffer.
Bit 15
CPU Overload
0
Normal operation is indicated by a 0 value.
1
A value of 1 indicates that the CPU is being over-taxed. Requesting an excessive amount of information from
the GPSCard may cause this. If this condition is occurring, limit redundant data logging or change to using
binary data output formats, or both.
You can attempt to tune the logging requirements to keep the idle time above 20% for best operation. If the
average idle % drops below 10% for prolonged periods of time (2-5 seconds), critical errors may result in
internal data loss and the over-load bit will be set to 1. You can monitor the CPU % idle time by using the
RCSA log message.
As the amount of CPU power becomes limited, the software will begin to slow down the position calculation
rate. If the CPU becomes further limited, the software will begin to skip range measurement processing.
Priority processing goes to the tracking loops.
Bit 16
Almanac Saved
0
Almanac not saved in flash memory.
1
Almanac saved in flash memory (12 channel OEM cards only).
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
REPA/B
B
Raw Ephemeris
REPA
This log contains the raw Binary information for subframes one, two and three from the satellite with the parity
information removed. Each subframe is 240 bits long (10 words – 24 bits each) and the log contains a total 720 bits (90
bytes) of information (240 bits x 3 subframes). The PRN number of the satellite from which it originated precedes this
information. This message will not be generated unless all 10 words from all 3 frames have passed parity.
Ephemeris data whose toe (time of ephemeris) is older than six hours will not be shown.
Structure:
$REPA prn
Field #
1
2
3
subframe1 subframe2 subframe3 *xx [CR][LF]
Field type
$REPA
prn
subframe1
Data Description
Log header
PRN of satellite from which data originated
Subframe 1 of ephemeris data (60 hex characters)
4
subframe2
Subframe 2 of ephemeris data (60 hex characters)
5
subframe3
Subframe 3 of ephemeris data (60 hex characters)
6
7
*xx
[CR][LF]
Checksum
Sentence terminator
Example
$REPA
14
8B09DC17B9079DD7007D5DE404A9B2D
04CF671C6036612560000021804FD
8B09DC17B98A66FF713092F12B359D
FF7A0254088E1656A10BE2FF125655
8B09DC17B78F0027192056EAFFDF2724C
9FE159675A8B468FFA8D066F743
*57
[CR][LF]
Example:
$REPA,14,8B09DC17B9079DD7007D5DE404A9B2D04CF671C6036612560000021804FD,
8B09DC17B98A66FF713092F12B359DFF7A0254088E1656A10BE2FF125655,
8B09DC17B78F0027192056EAFFDF2724C9FE159675A8B468FFA8D066F743*57[CR][LF]
REPB
Format:
Field #
1
(header)
2
3-4-5
Message ID = 14
Data
Sync
Checksum
Message ID
Message byte count
PRN number
Ephemeris data
Filler bytes
RGEA/B/C/D
Message byte count = 108
Bytes
3
1
4
4
4
90
2
Format
char
char
integer
integer
integer
char
char
Channel Range Measurements
Units
bytes
1-32
data [90]
Offset
0
3
4
8
12
16
106
51
The RGEA/B message replaces the obsolete RNGA/B and RQGA/B logs. It is smaller than the RNGA/B message and
outputs an improved channel status number that contains more information for the user. The RGEC/D messages are a
compressed form of the RGEB message.When using these logs, please keep in mind the constraints noted along with the
description.
GPSCard™ Command Descriptions Manual Rev 3
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5 – NovAtel Format Data Logs
It is important to ensure that the receiver clock has been set and can be monitored by the bits in the rec-status word.
Large jumps in range as well as ADR will occur as the clock is being adjusted. If the ADR measurement is being used in
precise phase processing it is important not to use the ADR if the "parity known" flag in the tr-status word is not set as
there may exist a half (1/2) cycle ambiguity on the measurement. The tracking error estimate of the pseudorange and
carrier phase (ADR) is the thermal noise of the receiver tracking loops only. It does not account for possible multipath
errors or atmospheric delays.
RGEA
Structure:
$RGEA
prn
week
seconds
# obs
rec status
psr psr std
adr adr std
dopp
C/No
locktime
tr-status
prn
psr psr std
adr adr std
dopp
C/No
locktime
tr-status
*xx
[CR][LF]
:
Field #
1
2
3
Field type
$RGEA
week
seconds
4
5
6
7
8
9
10
11
12
13
14
# obs
rec status
prn
psr
psr std
adr
adr std
dopp
C/N0
locktime
tr-status
15-23
...
variable
variable
*xx
[CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week (receiver time, not corrected for clock error,
CLOCKADJUST enabled)
Number of satellite observations with information to follow
Receiver self-test status (cf. Table 5-4)
Satellite PRN number (1-32) of range measurement
† Pseudorange measurement, in metres
† Pseudorange measurement standard deviation, in metres
† Carrier phase, in cycles (accumulated Doppler range)
† Estimated carrier phase standard deviation, in cycles
Instantaneous carrier Doppler frequency, in Hz
Signal to noise density ratio, where C/No = 10[log10(S/N0)], in dBHz
Number of seconds of continuous tracking (no cycle slipping)
Hexadecimal number indicating phase lock, channel number and channel
state as shown in Table 5-6, page Error! Bookmark not defined.
Next PRN range measurement
Next PRN range measurement
Checksum
Sentence terminator
†
Example
$RGEA
663
247893.30
7
000040F6
26
23704623.130
0.148
-124567967.330
0.010
2659.351
43.0
2693.370
E04
*73
[CR][LF]
These fields are only valid with X51(R) and XX51(R) models.
This output will always be a hexadecimal representation that must be converted to a binary format.
Example:
$RGEA,747,238091.45,7,000000F6,
26,23704623.130,0.148,-124567967.330,0.010,2659.351,43.0,2693.370,E04,
16,24492422.112,0.234,-128707643.246,0.015,-2473.786,39.0,6803.360,E14,
27,19929152.742,0.076,-104727535.338,0.006,15.233,48.7,6790.780,E34,
2,21729907.530,0.084,-114191131.178,0.006,2219.321,47.9,5899.770,E54,
19,21063013.716,0.088,-110686797.802,0.007,-1989.666,47.5,6801.570,E74,
28,24457949.736,0.202,-128525991.915,0.013,-3214.007,40.2,6556.760,E84,
31,22049154.556,0.108,-115869177.391,0.008,-1877.032,45.7,6788.370,EA4*6E
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
RGEB
Format:
Message ID = 32
Field #
1
(header)
Message byte count = 32 + (obs*44)
2
3
4
5
6
7
8
9
10
11
12
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
Number of observations (obs)
Receiver self-test status
PRN
† Pseudorange
† StdDev pseudorange
† Carrier phase (adr)
† StdDev accumulated Doppler
Doppler frequency
C/N0
Bytes
3
1
4
4
4
8
4
4
4
8
4
8
4
4
4
13
14
15...
Locktime
Tracking status
Next PRN offset = 32 + (obs*44)
4
4
Format
char
char
integer
integer
integer
double
integer
integer
integer
double
float
double
float
float
float
Units
metres
metres
cycles
cycles
Hz
C/N0=10*log(S/N0)dBHz
float
integer
seconds
see Table 5-6, page 95 ††
Offset
0
3
4
8
12
16
24
28
32
36
44
48
56
60
64
bytes
weeks
seconds
cf. Table 5-4
†
These fields are only valid with X51(R) and XX51(R) models.
††
The maximum channel, reported in the channel number field, is dependent on the GPSCard model type.
68
72
Table 5-6 GPSCard Tracking Status
N 7
31
30
29
N 6
28
27
26
25
N 5
24
23
22
21
N 4
20
19
18
17
N 3
16
15
14
13
N 2
12
11
10
9
N 1
8
7
6
5
N 0
4
3
2
1
0
<- <- Nibble Number
Bit
Description
Range Values
lsb = 0
Hex.
1
1 Tracking state
0 - 7 See below
2
2
4
3
8
4
10
5
0-n
(0 = first, n = last)
6 Channel num ber
(n depends on GPSCard)
7
20
40
80
8
100
9 Phase lock flag
1 = Lock, 0 = Not locked
200
10 Parity known flag
1 = Known, 0 = Not known
400
11 Code locked flag
1 = Lock, 0 = Not locked
12
800
1000
13 Reserved
2000
14
4000
15
8000
16 Reserved
10000
17
20000
18 Reserved
40000
19 Grouping
1 = Grouped, 0 = Not grouped
80000
20 Frequency
1 = L2, 0 = L1
100000
21 Code type
0 = C/A
2 = P-codeless
200000
22
1=P
3 = Reserved
400000
23 Reserved
800000
24
:
Reserved
29
30 Reserved
31 Reserved
GPSCard™ Command Descriptions Manual Rev 3
95
5 – NovAtel Format Data Logs
Table 5-6, Bits 0 -7: Channel Tracking State and Channel Number
State
0
1
2
3
Description
Idle
Sky search
Wide frequency band pull-in
Narrow frequency band pull-in
State
4
5
6
7
Description
Phase-lock loop
Re-acquisition
Steering
Frequency-lock loop
Higher numbers are reserved for future use
Example:
Offset (bytes)
Data (Hex) *
00000000:
00000016:
00000032:
00000048:
00000064:
AA
00
02
46
19
44
00
00
AA
E4
11
00
00
64
2A
43
00
00
65
42
20
70
14
6D
C3
00
F5
9B
84
95
00
0C
C1
9F
D3
00
41
62
C1
43
*
Refer to Binary Log Structure, page 54, for details on binary log formats.
AC
09
84
3A
04
01
00
FD
C5
0E
00
00
77
24
00
00
00
41
3C
00
1A
F6
BD
34
03
00
00
00
00
00
81
1B
3E
B7
55
45
... start of next record
where :
Data Location (bytes offset )
0 .. 2
3
4 .. 7
8 .. 11
12 ..15
16 ..23
24 .. 27
28 ..31
32 .. 35
36 .. 43
44 .. 47
48 .. 55
56 .. 59
60 .. 63
64 .. 67
68 .. 71
72 .. 75
96
Data
AA 44 11
43
20000000
AC010000
1A030000
00000000
09000000
F6000000
02000000
149BC162
ED811B3E
46AA6465
3AC5243C
34B75545
19E42A42
C395D343
040E0000
70F50C41
84FD7741
6D849FC1
Description
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
Number of observations
Receiver self-test status
PRN
Pseudorange
Std deviation pseudorange
Carrier phase (adr)
Std deviation accumulated Doppler
Doppler frequency
C/N0
Decoded Value
32
428
794
237230.00
9
000000F6
2
25155654.172
0.152
-132193113.348
0.010
3419.450
42.7
Locktime
Tracking status
423.170
E04
GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
RGEC/D
Format:
Message ID = 33 (RGEC) or Message ID = 65 (RGED) Message byte count = 24 + (20*number of obs)
Data
Sync
Checksum
Message ID
Message byte count
Number of obs
Week number
Seconds of week
Receiver status
First PRN range record
Bytes
3
1
4
4
2
2
4
4
20
Format
char
char
integer
integer
Scale
integer
integer
See tables below: Range Record Format and Range Record Format (RGED only)
1
1
1/100
1
Offset
0
3
4
8
12
14
16
20
24
Next PRN offset = 24 + (20*number of obs)
Range Record Format
Data
PRN
1
C/No
2
Lock time
3
Accumulated Doppler range *
Doppler frequency
Pseudorange
StdDev Accumulated Doppler
StdDev Pseudorange
Bit(s) from first to last
0..5
6..10
11.31
32..63
68..95
64..67 msn
96..127 lsw
128..131
132..135
Channel Tracking Status
136..159
*
Length (bits)
6
5
21
32
28
36
Units
integer
integer
integer
integer 2’s comp.
integer 2’s comp.
integer 2’s comp.
Scale
1
(20+n) dBHz
1/32 seconds
1/256 cycles
1/256 Hz
1/128 m
4
4
integer
integer
24
integer
[(n+1)*1/512] cyc
RGEC = [(n+1)*1/16] m
RGED = see 4
see Table 5-6, page 95
Accumulated Doppler range will roll over every ± 8388608 carrier cycles.
Notes on Range Record Format (RGED only)
1
C/No is constrained to a value between 20-51dB-Hz, Thus, if it is reported that C/No = 20 dB-Hz, the actual value
could be less. Likewise, if it is reported that C/No = 51 dB-Hz, the true value could be greater.
2
Lock time rolls over after 2,097,151 seconds.
3
ADR (Accumulated Doppler Range) is calculated as follows:
ADR_ROLLS = ( -RGED_PSR / WAVELENGTH - RGED_ADR) / MAX_VALUE
Round to the closest integer
IF (ADR_ROLLS ≤ -0.5)
ADR_ROLLS = ADR_ROLLS - 0.5
ELSE
ADR_ROLLS = ADR_ROLLS + 0.5
At this point change ADR_ROLLS to an integer
CORRECTED_ADR = RGED_ADR + (MAX_VALUE * ADR_ROLLS)
GPSCard™ Command Descriptions Manual Rev 3
97
5 – NovAtel Format Data Logs
where:
ADR has units of cycles
WAVELENGTH = 0.1902936727984 for L1
WAVELENGTH = 0.2442102134246 for L2
MAX_VALUE = 838860
4
StdDev Pseudorange Scale
Code
5
RGED
Code
RGED
0
0.000 to 0.050
8
0.855 to 1.281
1
0.051 to 0.075
9
1.282 to 2.375
2
0.076 to 0.113
10
2.376 to 4.750
3
0.114 to 0.169
11
4.751 to 9.500
4
0.170 to 0.253
12
9.501 to 19.000
5
0.254 to 0.380
13
19.001 to 38.000
6
0.381 to 0.570
14
38.001 to 76.000
7
0.571 to 0.854
15
76.001to 52.000
Only bits 0 - 23 are represented in the RGED log
RT20A/B
Computed Position – Time Matched
RT20
This log represents positions that have been computed from time-matched reference and remote observations. There is
no extrapolation error on these positions but because they are based on buffered measurements, they lag real time by
some amount depending on the latency of the data link. With the recommended reference station logs active (RTCM3
ontime 10, RTCM59 ontime 2, RTCM ontime 5), the lag varies from 1-2 seconds at 1200 bps to about 0.4 seconds at
9600 bps.
The data in the RT-20 logs will change only when a reference observation (RTCM59) changes. If the log is being output
at a fixed rate and the reference corrections are interrupted, then the RT20A/B log will continue to be output at the same
rate but the position and time will not change.
A better trigger for this log is “ONCHANGED”. Then, only positions related to unique reference messages will be
produced, and the existence of this log will indicate a successful link to the base.
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
RT20A
Structure:
$RT20A week seconds
hgt std
Field #
1
2
3
4
5
sol status
Field type
$RT20A
week
seconds
# sats
lat
6
lon
7
hgt
8
9
10
11
12
13
14
15
16
17
undulation
datum ID
lat std
lon std
hgt std
sol status
rt20 status
stn ID
*xx
[CR][LF]
# sats
lat
rt20 status
lon
stn ID
hgt
*xx
undulation
datum ID
lat std
lon std
[CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week
Number of satellites in use (00-12). May be different to the number in view
Latitude of position in current datum, in degrees (DD.dddddddd). A negative sign implies South
latitude
Longitude of position in current datum, in degrees (DDD.dddddddd). A negative sign implies
West longitude
Height of position in current datum, in metres above mean sea level (MSL) (see Figure 5-2,
page 79)
Geoidal separation, in metres, where positive is above spheroid and negative is below spheroid
Current datum (see Table A-2, page 166)
Standard deviation of latitude solution element, in metres
Standard deviation of longitude solution element, in metres
Standard deviation of height solution element, in metres
Solution status as listed in Table 5-2, page 65
RT20 status as listed in Table 5-4, page 66
Differential reference station ID, 0000-1023
Checksum
Sentence terminator
Example
$RT20A
779
237328.00
9
51.11411137
-114.04302707
1058.601
-16.263
61
0.015
0.016
0.015
0
0
200
*47
[CR][LF]
Example:
$RT20A,779,237328.00,9,51.11411137,-114.04302707,1058.601,-16.263,61,0.015,
0.016,0.015,0,0,200*47[CR][LF]
GPSCard™ Command Descriptions Manual Rev 3
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5 – NovAtel Format Data Logs
RT20B
Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Message ID = 35
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
Number of sats in solution
Latitude
Longitude
Height
Undulation
Datum ID
StdDev of latitude
StdDev of longitude
StdDev of height
Solution status
RT20 status
Reference station ID
RTCAA/B
Message byte count = 100
Bytes
3
1
4
4
4
8
4
8
8
8
8
4
8
8
8
4
4
4
Format
char
char
integer
integer
integer
double
integer
double
double
double
double
integer
double
double
double
integer
integer
integer
Units
bytes
weeks
seconds
degrees (+ is North, - is South)
degrees (+ is East, - is West)
metres above MSL
metres
see Table A-2, page 166
metres
metres
metres
see Table 5-2, page 65
see Table 5-4, page 66
Real Time Differential Corrections (Aviation)
Offset
0
3
4
8
12
16
24
28
36
44
52
60
64
72
80
88
92
96
R
The RTCAA/B logs contain RTCA standard differential corrections. The RTCAA log contains RTCA data in ASCII
hexadecimal with a NovAtel header and terminating with a checksum. The RTCAB log contains RTCA data in binary
format with a NovAtel header. See Chapter 9, page 135, for more detailed information on RTCA.
RTCMA/B
Real Time Differential Corrections (Maritime)
R
The RTCMA/B logs contain RTCM standard differential corrections. The RTCMA log contains RTCM data in ASCII
hexadecimal with a NovAtel header and terminating with a checksum. The RTCMB log contains RTCM data in binary
format with a NovAtel header. See Chapter 8, page 129, for more detailed information on RTCM.
RTKA/B
Computed Position - Time Matched
RTK
This log represents positions that have been computed from time-matched reference and remote observations. There is no
reference station extrapolation error on these positions but because they are based on buffered measurements, they lag
real time by some amount depending on the latency of the data link. If the remote receiver has not been enabled to accept
RTK differential data, or is not actually receiving data leading to a valid solution, this will be reflected by the code shown
in field #16 (RTK status) and #17 (position type).
The data in the logs will change only when a reference observation (RTCM Type 59 or the corresponding RTCA Type 7)
changes. If the log is being output at a fixed rate and the differential data is interrupted, then the RTKA/B logs will
continue to be output at the same rate but the position and time will not change.
A good message trigger for this log is "onchanged". Then, only positions related to unique reference station messages will
be produced, and the existence of this log will indicate a successful link to the reference station.
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
RTKA
Structure:
$RTKA
week
seconds
# sv
lat
lon
hgt
undulation
datum ID
lat s
lon s
hgt s
soln status
rtk status
dyn mode
stn ID
[CR][LF]
posn type
Field #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Field type
$RTKA
week
seconds
#sv
#high
L1L2 #high
lat
lon
hgt
undulation
datum ID
lat s
lon s
hgt s
soln status
rtk status
posn type
dyn mode
stn ID
*xx
[CR][LF]
# high
*xx
L1L2 #high
Data Description
Log header
GPS week number
GPS time into the week (in seconds)
Number of matched satellites; may differ from the number in view.
Number of matched satellites above RTK mask angle; observations from satellites below mask are heavily
de-weighted
Unused, will report 0
Latitude of position in current datum, in decimal fraction format. A negative sign implies South latitude
Longitude of position in current datum, in decimal fraction format. A negative sign implies West longitude
Height of position in current datum, in meters above mean sea level
Geoidal separation, in meters, where positive is above ellipsoid and negative is below ellipsoid
Current datum (see Appendix A, page 166)
Standard deviation of latitude solution element, in meters
Standard deviation of longitude solution element, in meters
Standard deviation of height solution element, in meters
Solution status (see Table 5-2, page 65)
RTK status (see Table 5-4, page 66)
Position type (seeTable 5-3, page 66)
Dynamics mode (0= static, 1= kinematic)
Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385)
Checksum
Sentence terminator
Example
$RTKA
872
174962.00
8
7
0
51.11358039754
-114.04358003164
1059.4105
-16.2617
61
0.0036
0.0039
0.0066
0
0
4
0
119
*33
[CR][LF]
Example:
$RTKA,872,174962.00,8,7,0,51.11358039754,-114.04358003164,1059.4105,
-16.2617,61,0.0036,0.0039,0.0066,0,0,4,0,119*33[CR][LF]
GPSCard™ Command Descriptions Manual Rev 3
101
5 – NovAtel Format Data Logs
RTKB
Format:
Message ID = 61
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
SATA/B
Message byte count = 116
Data
Bytes
Sync
Checksum
Message ID
Message byte count
Week number
GPS time into the week
Number of matched satellites (00-12)
Number of matched satellites above RTK mask angle
Unused, will report 0
Latitude
Longitude
Height above mean sea level
Undulation
Datum ID
Standard deviation of latitude
Standard deviation of longitude
Standard deviation of height
Solution status
RTK status
Position type
Dynamics mode
Reference station identification (RTCM: 0 - 1023, or RTCA: 266305 - 15179385)
Satellite Specific Data
3
1
4
4
4
8
4
4
4
8
8
8
8
4
8
8
8
4
4
4
4
4
Format
char
char
integer
integer
integer
double
integer
integer
integer
double
double
double
double
integer
double
double
double
integer
integer
integer
integer
integer
Units
weeks
seconds
degrees
degrees
meters
meters
meters
meters
meters
Offset
0
3
4
8
12
16
24
28
32
36
44
52
60
68
72
80
88
96
100
104
108
112
B (R)
This log provides satellite specific data for satellites actually being tracked. The record length is variable and depends on
the number of satellites.
Each satellite being tracked has a reject code indicating whether it is used in the solution, or the reason for its rejection
from the solution. The reject value of 0 indicates the observation is being used in the position solution. Values of 1
through 11 indicate the observation has been rejected for the reasons specified in Table 5-5. A range reject code of 8 only
occurs when operating in differential mode and an interruption of corrections has occurred or the DGPSTIMEOUT has
been exceeded.
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
SATA
Structure:
$SATA
prn
week
seconds
sol status
# obs
azimuth
elevation residual
reject code
azimuth
elevation residual
reject code
:
prn
Field #
1
2
3
4
5
6
7
8
9
10
11...
variable
variable
Field type
$SATA
week
seconds
sol status
# obs
prn
azimuth
elevation
residual
reject code
..
*xx
[CR][LF]
*xx [CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week
Solution status as listed in Table 5-2, page 65
Number of satellite observations with information to follow:
Satellite PRN number (1-32)
Satellite azimuth from user position with respect to True North, in degrees
Satellite elevation from user position with respect to the horizon, in degrees
Satellite range residual from position solution for each satellite, in metres
Indicates that the range is being used in the solution (code 0) or that it was rejected (code
1-11), as shown in Table 5-7, page 103
Next PRN
Checksum
Sentence terminator
Example
$SATA
637
513902.00
0
7
18
168.92
5.52
9.582
0
*1F
[CR][LF]
Example:
$SATA,637,513902.00,0,7,18,168.92,5.52,9.582,0,6,308.12,55.48,0.737,0,
15,110.36,5.87,16.010,0,11,49.63,40.29,-0.391,0,
2,250.05,58.89,-12.153,0,16,258.55,8.19,-20.237,0,
19,118.10,49.46,-14.803,0*1F[CR][LF]
Table 5-7 GPSCard Range Reject Codes
Value
0
1
2
3
4
5
6
7
8†
9
10
11
Description
Observations good
Bad health
Old ephemeris
Eccentric anomaly error
True anomaly error
Satellite coordinate error
Elevation error
Misclosure too large
No Differential Correction
No Ephemeris
Invalid IODE
Locked Out
Higher values reserved for future use.
† This code only available with “R” option.
GPSCard™ Command Descriptions Manual Rev 3
103
5 – NovAtel Format Data Logs
SATB
Format:
Message ID = 12
Field #
1
(header)
Message byte count = 32 + (obs*32)
Data
Bytes
Format
Units
Sync
3
char
Checksum
1
char
Message ID
4
integer
Message byte count
4
integer
bytes
Week number
4
integer
weeks
Seconds of week
8
double
seconds
Solution status
4
integer
see Table 5-2, page 65
Number of observations (obs)
4
integer
PRN
4
integer
Azimuth
8
double
degrees
Elevation
8
double
degrees
Residual
8
double
metres
Reject code
4
integer
see Table 5-7, page 103
Next PRN offset = 32 + (obs * 32) where obs varies from 0 to (obs-1)
2
3
4
5
6
7
8
9
10
11...
SPHA/B
Offset
0
3
4
8
12
16
24
28
32
36
44
52
60
B
Speed and Direction Over Ground
This log provides the actual speed and direction of motion of the GPSCard antenna over ground, at the time of
measurement, and is updated up to 10 times per second. It should be noted that the GPSCard does not determine the
direction a vessel, craft, or vehicle is pointed (heading), but rather the direction of motion of the GPS antenna relative to
ground.
Structure:
$SPHA
Field #
1
2
3
4
5
week
seconds
Field type
$SPHA
week
seconds
hor spd
trk gnd
6
vert spd
7
8
9
sol status
*xx
[CR][LF]
hor spd
trk gnd
vert spd
sol status
*xx [CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week
Horizontal speed over ground, in m/s
Actual direction of motion over ground (track over ground) with respect to True North, in
degrees
Vertical speed, in m/s, where positive values indicate increasing altitude (up) and negative
values indicate decreasing altitude (down)
Solution status as listed in Table 5-2
Checksum
Sentence terminator
Example
$SPHA
640
333111.00
0.438
325.034
2.141
0
*02
[CR][LF]
Example:
$SPHA,640,333111.00,0.438,325.034,2.141,0*02[CR][LF]
104
GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
SPHB
Format:
Message ID = 06
Field #
1
(header)
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
Horizontal speed
Track over ground (TOG)
Vertical speed
Solution status
2
3
4
5
6
7
SVDA/B
Message byte count = 52
Bytes
3
1
4
4
4
8
8
8
8
4
Format
char
char
integer
integer
integer
double
double
double
double
integer
Units
bytes
weeks
seconds
m/s
degrees
m/s
see Table 5-2, page 65
SV Position in ECEF XYZ Coordinates with Corrections
Offset
0
3
4
8
12
16
24
32
40
48
B (R)
When combined with a RGEA/B/C/D log, this data set contains all of the decoded satellite information necessary to
compute the solution: satellite coordinates (ECEF WGS-84), satellite clock correction, ionospheric corrections (from
broadcast model), tropospheric correction (Hopfield model), decoded differential correction used and range weight
standard deviation. The corrections are to be added to the pseudoranges. Only those satellites that are healthy are
reported here. Also see Figure 5-3, page 108.
GPSCard™ Command Descriptions Manual Rev 3
105
5 – NovAtel Format Data Logs
SVDA
Structure:
$SVDA
prn
week
seconds
rec clk err
# obs
x
y
z
clk corr
ion corr
trop corr diff corr rng std
x
y
z
clk corr
ion corr
trop corr diff corr rng std
..
prn
Field #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15..
variable
variable
Field type
$SVDA
week
seconds
rec clk err
# obs
prn
x
y
z
clk corr
ion corr
trop corr
diff corr †
rng std
..
*xx
[CR][LF]
†
*xx [CR][LF]
Data Description
Log header
GPS week number
GPS seconds into the week (receiver time, not corrected for clock error, CLOCKADJUST enabled)
Solved receiver clock error (metres)
Number of satellite observations to follow
Satellite PRN number (1-32)
Satellite x coordinate (metres)
Satellite y coordinate (metres)
Satellite z coordinate (metres)
Satellite clock correction (metres)
Ionospheric correction (metres)
Tropospheric correction (metres)
Decoded differential correction used (metres)
Range weight standard deviation (metres)
Next PRN
Checksum
Sentence terminator
Example
$SVDA
766
143860.00
-4.062
7
20
-15044774.225
-9666598.520
19499537.398
6676.013
-1.657
-2.662
16.975
0.674
*23
[CR][LF]
This field only valid in GPSCards with “R” options.
Example:
$SVDA,766,143860.00,-4.062,7,
20,-15044774.225,-9666598.520,19499537.398,6676.013,-1.657,-2.662,16.975,0.674
5,-10683387.874,-21566845.644,11221810.349,18322.228,-1.747,-2.819,-8.864,0.790,
6,-20659074.698,-28381.667,16897664619,57962.693,-2.543,4.401,-37.490,1.203,
16,142876.148,-26411452.927,2795075.561,-22644.136,-2.733,-4.904,7.701,1.259,
24,-852160.876,-16138149.057,21257323.813,229594.682,-1.545,-2.451,32.178,0.420,
25,-12349609.643,11102877.199,20644151.935,-4313.339,-3.584,-8.579,-42.813,1.370,
..,
4,14209626.440,-9259502.647,20544348.215,12811.399,-2.675,-4.741,-10.778,1.239
*23[CR][LF]
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GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
SVDB
Format:
Field #
1
(header)
2
3
4
5
6
7
8
9
10
11
12
13
14
15...
Message ID = 36
Message byte count = 36 +(obs*68)
Data
Sync
Checksum
Message ID
Message byte count
Week number
Time in seconds
Receiver clock error
Number of observations to follow (obs)
Satellite PRN number
x coordinate of satellite
y coordinate of satellite
z coordinate of satellite
Satellite clock correction
Ionospheric correction
Tropospheric correction
Decoded differential correction used
†
Range weight standard deviation
Next PRN offset = 36 + (obs*68) where obs
varies from 0 to (obs-1)
GPSCard™ Command Descriptions Manual Rev 3
Bytes
3
1
4
4
4
8
8
4
4
8
8
8
8
8
8
8
8
Format
char
char
integer
integer
integer
double
double
integer
integer
double
double
double
double
double
double
double
double
Units
weeks
seconds
metres
metres
metres
metres
metres
metres
metres
metres
metres
Offset
0
3
4
8
12
16
24
32
36
40
48
56
64
72
80
88
96
107
5 – NovAtel Format Data Logs
Figure 5-3 The WGS-84 ECEF Coordinate System
108
GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
TM1A/B
B
Time of 1PPS
This log provides the time of the GPSCard 1PPS in GPS week number and seconds into the week. It also includes the
receiver clock offset, the standard deviation of the receiver clock offset and clock model status. This log will output at a
maximum rate of 1 Hz.
TM1A
Structure:
$TM1A
Field #
1
2
3
week
seconds
Field type
$TM1A
week
seconds
4
offset
5
6
offset std
utc offset
7
cm status
8
9
*xx
[CR][LF]
offset offset std
utc offset cm status *xx
Data Description
Log header
GPS week number
GPS seconds into the week at the epoch coincident with the 1PPS output strobe
(receiver time)
Receiver clock offset, in seconds. A positive offset implies that the receiver clock is
ahead of GPS Time. To derive GPS time, use the following formula:
GPS time = receiver time – (offset)
Standard deviation of receiver clock offset, in seconds
This field represents the offset of GPS time from UTC time, computed using almanac
parameters. To reconstruct UTC time, algebraically subtract this correction from field 3
above (GPS seconds).
UTC time = GPS time – (utc offset)
Receiver Clock Model Status where 0 is valid and values from -20 to -1 imply that the
model is in the process of stabilization
Checksum
Sentence terminator
[CR][LF]
Example
$TM1A
794
414634.999999966
-0.000000078
0.000000021
-9.999999998
0
*57
[CR][LF]
Example:
$TM1A,794,414634.999999966,-0.000000078,0.000000021,-9.999999998,0*57[CR][LF]
TM1B
Format:
Field #
1
(header)
2
3
4
5
6
7
Message ID = 03
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
Clock offset
StdDev clock offset
UTC offset
Clock model status
Message byte count = 52
Bytes
3
1
4
4
4
8
8
8
8
4
GPSCard™ Command Descriptions Manual Rev 3
Format
char
char
integer
integer
integer
double
double
double
double
integer
Units
bytes
weeks
seconds
seconds
seconds
seconds
0 = good, -1 to -20 = bad
Offset
0
3
4
8
12
16
24
32
40
48
109
5 – NovAtel Format Data Logs
VERA/B
B
Receiver Hardware and Software Version Numbers
This log contains the current hardware type and software version number for the GPSCard. Together with the RVSA/B
log, it supersedes the RCSA/B log.
VERA
Structure:
$VERA
week
Field #
1
2
3
4
5
6
seconds
version *xx
[CR][LF]
Field type
$VERA
week
seconds
version
Data Description
Log header
GPS week number
GPS seconds into the week.
GPSCard hardware type and software version number
*xx
[CR][LF]
Checksum
Sentence terminator
Example
$VERA
853
401364.50
OEM-3 MILLENSTD CGL96170069 HW 3-1 SW
4.42/2.03 May 14/96
*2B
[CR][LF]
Example:
$VERA,853,401364.50,OEM-3 MILLENSTD CGL96170069 HW 3-1 SW 4.42/2.03 May
14/96*2B[CR][LF]
VERB
Format:
Field #
1
(header)
2
3
4
VLHA/B
Data
Sync
Checksum
Message ID
Message byte count
Week number
Time into week
Version numbers
Message ID = 58
Bytes
3
1
4
4
4
8
80
Message byte count = 104
Format
char
char
integer
integer
integer
double
char
Velocity, Latency, and Direction over Ground
Units
weeks
s
Offset
0
3
4
8
12
16
24
B (R)
This log is similar to the SPHA/B message. As in the SPHA/B messages the actual speed and direction of the GPSCard
antenna over ground is provided. The VLHA/B differs in that it provides a measure of the latency in the velocity time tag
and a new velocity status word that gives the user more velocity quality information. The velocity status indicates
varying degrees of velocity quality. To ensure healthy velocity, the position sol-status must also be checked. If the solstatus is non-zero, the velocity will likely be invalid. Also, it includes the age of the differential corrections used in the
velocity computation. It should be noted that the GPSCard does not determine the direction a vessel, craft, or vehicle is
pointed (heading), but rather the direction of motion of the GPS antenna relative to ground.
110
GPSCard™ Command Descriptions Manual Rev 3
5 – NovAtel Format Data Logs
VLHA
Structure:
$VLHA
week
vel status
Field #
1
2
3
4
seconds
Field type
$VLHA
week
seconds
latency
†
5
6
7
age
hor spd
trk gnd
8
vert spd
9
10
sol status
vel status
†††
*xx
[CR][LF]
†
11
12
latency
age
hor spd
trk gnd
vert spd
sol status
*xx [CR][LF]
††
Data Description
Log header
GPS week number
GPS seconds into the week
A measure of the latency in the velocity time tag in seconds. It should be subtracted
from the time to give improved results.
Age of Differential GPS data in seconds
Horizontal speed over ground, in m/s
Actual direction of motion over ground (track over ground) with respect to True North, in
degrees
Vertical speed, in m/s, where positive values indicate increasing altitude (up) and
negative values indicate decreasing altitude (down)
Solution status as listed in Table 5-2
Velocity status as listed in Table 5-6
Checksum
Sentence terminator
Example
$VLHA
640
333111.00
0.250
3.500
0.438
325.034
2.141
0
0
*02
[CR][LF]
Velocity Latency
The velocity is computed using Doppler values derived from differences in consecutive carrier phase measurements. As such, it is an average velocity based on the
time difference between successive position computations and not an instantaneous velocity at the SPHA/B time tag. Under normal operation the position’s
coordinates are updated at a rate of two times per second. The velocity latency compared to this time tag will normally be 1/2 the time between position fixes. The
default filter rate is 2 Hz, so this latency is typically 0.25 second, but if, for example, the POSA records were to be logged ontime 0.2, then the velocity latency would
be one half of 0.2, or 0.1 second. The latency can be reduced further by the user requesting the POSA/B, the SPHA/B, or the VLHA/B message at rates higher than
2 Hz. For example, a rate of 10 Hz will reduce the velocity latency to 1/20 of a second. For integration purposes, the velocity latency should be applied to the record
time tag.
††
Differential age is only available from receivers with the “R” or “RT-20” option.
†††
Only receivers with the “R” option can report a value of 0, 1, or 2.
Example:
$VLHA,640,333111.00,0.250,3.500,0.438,325.034,2.141,0,0*02[CR][LF]
NOTE: Logging rates greater than once per second require x51 or xx51 models.
GPSCard™ Command Descriptions Manual Rev 3
111
5 – NovAtel Format Data Logs
VLHB
Format:
Message ID = 34
Field #
1
(header)
Data
Sync
Checksum
Message ID
Message byte count
Week number
Seconds of week
Latency
Age
††
Horizontal speed
Track over ground (TOG)
Vertical speed
Solution status
Velocity status
†††
2
3
4
5
6
7
8
9
10
Message byte count = 72
Bytes
3
1
4
4
4
8
8
8
8
8
8
4
4
Format
char
char
integer
integer
integer
double
double
double
double
double
double
integer
integer
Units
bytes
weeks
seconds
m/s
seconds
m/s
degrees
m/s
see Table 5-2, page 65
see Table 5-8, page 112
Offset
0
3
4
8
12
16
24
32
40
48
56
64
68
Table 5-8 GPSCard Velocity Status
Value
0 †††
1 †††
2 †††
3
4
5
Description
Velocity computed from differentially corrected carrier phase data
Velocity computed from differentially corrected Doppler data
Old velocity from differentially corrected phase or Doppler (higher latency)
Velocity from single point computations
Old velocity from single point computations (higher latency)
Invalid velocity
††† Higher values reserved for future use
112
GPSCard™ Command Descriptions Manual Rev 3
6 – Special Pass-Through Logs
6
SPECIAL PASS-THROUGH LOGS
The pass-through logging feature enables the GPSCard to redirect any ASCII or binary data that is input at a specified
port (COM1, COM2, or Console) to any specified GPSCard port (COM1, COM2, or Console). This capability, in
conjunction with the SEND command, can allow the GPSCard to perform bi-directional communications with other
devices such as a modem, terminal, or another GPSCard.
Figure 6-1 Illustration of Pass-Through
gpsload main.btl
gpscon/a
log console com1a onchanged
ta
ut da
Inp
GPSCard
(PC Series)
COM1
s-throug
h
for pas
- Data Link
- MODEM
- GPSCard
- Other Data Sources...
gpsload
main.bt
l
gpscon
/a
log con
sole com
1a onc
hanged
Hos
t PC
There are three pass-through logs – COM1A/B, COM2A/B, and CONSOLEA/B (console is available only with PC
Series GPSCards).
Pass-through is initiated the same as any other log, i.e., LOG [to-port] [data-type-A/B] [trigger]. However, pass-through
can be more clearly specified as: LOG [to-port] [from-port-A/B] [onchanged]. Now, the [from-port-A/B] field
designates the port which accepts data (i.e., COM1, COM2, or Console) as well as the format in which the data will be
logged by the [to-port] — (A for ASCII or B for Binary).
When the [from-port-A/B] field is designated with an [A], all data received by that port will be redirected to the [to-port]
in ASCII format and will log according to standard NovAtel ASCII format. Therefore, all incoming ASCII data will be
redirected and output as ASCII data. However, any binary data received will be converted to a form of ASCII
hexadecimal before it is logged.
When the [from-port-A/B] field is designated with a [B], all data received by that port will be redirected to the [to-port]
exactly as it is received. The log header and time-tag adhere to standard NovAtel Binary Format followed by the passthrough data as it was received (ASCII or binary).
Pass-through logs are best utilized by setting the [trigger] field as onchanged or onnew. Either of these two triggers will
cause the incoming data to log when any one of the following conditions is met:
•
•
•
Upon receipt of a <CR> character
Upon receipt of a <LF> character
Upon receipt of 80 characters
GPSCard™ Command Descriptions Manual Rev 3
113
6 – Special Pass-Through Logs
•
1/2 second timeout following receipt of last character
Each pass-through record transmitted by the GPSCard is time tagged by the GPSCard clock in GPS weeks and seconds.
For illustration purposes, you could connect two PC Series GPSCards together via their COM1 ports such as in a
reference station – remote station scenario. If the reference station were logging DCSA data to the remote station, it
would be possible to use the pass-through logs to pass through the received DCSA differential correction data to a disk
file (let's call it DISKFILE.log) at the remote station host PC hard disk. (See Figure 6-2, page 114.)
Figure 6-2 Pass-Through Log Data
When pass-through logs are being used, the GPSCard's command interpreter continues to monitor the port for valid input
commands and replies with error messages when the data is not recognized as such. If you do not want the pass-through
input port to respond with error messages during unrecognized data input, refer to the MESSAGES command, page 39,
for details on how to inhibit the port's error message responses. As well, if you do not want the reference station to accept
any input from the remote device, use the ACCEPT NONE command to disable the port's command interpreter.
COMMAND SYNTAX
Syntax:
log
to-port
from-port-A/B
Syntax
log
to-port
from-port-[A/B]
Range Value
—
COM1, COM2, or console
COM1A/B, COM2A/B, ConsoleA/B
trigger
onchanged or onnew
trigger
Description
Log command
Port that will output the pass-through log data
Port that will accept input data;
[A] option logs data as ASCII,
[B] option logs data with binary header
log will output upon receipt of :
<CR>, <LF>, 80 characters, or 1/2 sec. timeout
Default
unlogall
—
—
—
Example 1:
log com2 com1a onchanged
Example 2:
log console com1a onnew
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GPSCard™ Command Descriptions Manual Rev 3
6 – Special Pass-Through Logs
ASCII LOG STRUCTURE
$port ID
Field #
1
2
3
4
5
6
week
seconds
pass-through data
Field type
$port ID
week
seconds
pass-through data
Data Description
Log header: Identifies port accepting input data
GPS week number
GPS seconds into the week at time of log
Data accepted into COM1(up to 80 characters)
*xx
[CR][LF]
Checksum
Sentence terminator
*xx
[CR][LF]
Example
$COM1
747
347131.23
$TM1A,747,347131.000000000,
0.000000058,0.000000024,
-9.000000009,0*78<CR>
*2E
[CR][LF]
Example 1:
$COM1,747,347131.23,$TM1A,747,347131.000000000,0.000000058,0.000000024,
-9.000000009,0*78<CR>*2E[CR][LF]
$COM1,747,347131.31,<LF>*4F[CR][LF]
$COM1,747,347131.40,Invalid Command Option<LF>*7C[CR][LF]
$COM1,747,347131.42,Com1>Invalid Command Option<LF>*30[CR][LF]
$COM1,747,347131.45,Com1>*0A[CR][LF]
Example 1 above shows what would result if a GPSCard logged TM1A data into the COM1 port of another GPSCard,
where the accepting card is redirecting this input data as a pass-through log to its COM2 port (log com2 com1a
onchanged). Under default conditions the two cards will “chatter” back and forth with the Invalid Command Option
message (due to the command interpreter in each card not recognizing the command prompts of the other card). This
chattering will in turn cause the accepting card to transmit new pass-through logs with the response data from the other
card. To avoid this chattering problem, use the GPSCard MESSAGES command on the accepting port to disable error
reporting from the receiving port command interpreter or if the incoming data is of no use to the GPSCard, then disable
the command interpreter with the ACCEPT NONE command.
If the accepting port’s error reporting is disabled by MESSAGES OFF, the $TM1A data record would pass through
creating two records as follows:
Example 1a:
$COM1,747,347204.80,$TM1A,747,347203.999999957,-0.000000015,0.000000024,
-9.000000009,0*55<CR>*00[CR][LF]
$COM1,747,347204.88,<LF>*48[CR][LF]
The reason that two records are logged from the accepting card is because the first record was initiated by receipt of the
$TM1A log’s first terminator <CR>. Then the second record followed in response to the $TM1A log’s second terminator
<LF>.
Note that the time interval between the first character received ($) and the terminating <LF> can be calculated by
differencing the two GPS time tags (0.08 seconds). This pass-through feature is useful for time tagging the arrival of
external messages. These messages could be any user-related data. If the user is using this feature for tagging external
events then it is recommended that the command interpreter be disabled so that the GPSCard does not respond to the
messages. See the ACCEPT command, page 20.
--------Example 1b illustrates what would result if $TM1B binary log data were input to the accepting port
(i.e., log com2 com1a onchanged).
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115
6 – Special Pass-Through Logs
Example 1b:
$COM1,747,349005.18,<AA>D<DC1>k<ETX><NUL><NUL><NUL>4<NUL><NUL><NUL>
<EB><STX><NUL><NUL><FE>3M<NAK>A<VT><83><D6>o<82><C3>Z<BE><FC><97>I
<91><C5>iV><7F><8F>O<NUL><NUL><NUL>"<C0><NUL><NUL><NUL><NUL>*6A
As can be seen, the $TM1B binary data at the accepting port was converted to a variation of ASCII hexadecimal before it
was passed through to COM2 port for logging (MESSAGES command set to OFF).
--------Example 2 below illustrates what would result if $DCSA data is accepted into the GPSCard COM1 port and logged to the
host PC console (MESSAGES command set to OFF) (i.e., log console com1a onchanged).
Example 2:
$COM1,747,328116.97,$DCSA,747,327962.50,123,6,19,161,46.125,0.044,2,17,
47.844,-0.151,15,164,-7.166,*55[CR][LF]
$COM1,747,328117.05,0.095,27,237,61.697,-0.125,7,64,-13.049,0.048,26,0,
36.795,0.106*16<CR>*53[CR][LF]
$COM1,747,328117.12,<LF>*40[CR][LF]
Here, it can be seen that the single $DCSA message accepted into the GPSCard COM1 port resulted in three records
being logged to the console. This is because the first record resulted from receipt of the 80 character input data limit, the
second record resulted from receipt of the $DCSA record terminator character <CR>, and a third record followed receipt
of the $DCSA record terminator character <LF>.
--------Example 3 shown below is the result of data being manually transmitted from a dumb terminal into an accepting
GPSCard COM1 port which may then be saved to a PC disk file. The [Return] key was not pressed at the terminal.
Pass-through was set up as: log console com1a onnew. The PC Series GPSCard has been booted using
GPSCON/adiskfile.log as the console disk logging destination.
The command interpreter was disabled via ACCEPT COM1 NONE so that if valid commands were in the data, e.g.,
"creset" or "unlogall", the GPSCard would not be erroneously reconfigured. Use the MESSAGES OFF command if the
incoming data is to be processed by the GPS receiver. Use ACCEPT COM1 NONE for pass-through data that has
nothing to do with the receiver.
Multiple messages resulted from the pass-through log 1/2 second default time-out.
Example 3:
$COM1,747,328850.28,This is a test us*06
$COM1,747,328855.08,ing the passthru log*1B
$COM1,747,328860.79,s.*3F
$COM1,747,328866.89,If *4A
$COM1,747,328868.64,I pause too long the recor*3D
$COM1,747,328876.07,d will send automatically*61
$COM1,747,328898.43,As you can see *0C
$COM1,747,328903.72,I*0A
$COM1,747,328904.47, am not a very fast*62
$COM1,747,328910.79, typist.*79
$COM1,747,328922.14,End of *06
$COM1,747,328924.42,test*53
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GPSCard™ Command Descriptions Manual Rev 3
6 – Special Pass-Through Logs
BINARY LOG STRUCTURE
Format:
Message ID =
Message byte count =
Field #
1
(header)
2
3
4
Data
Sync
Checksum
Message ID
Message byte
count
Week number
Seconds of week
Pass-through data
Bytes
3
1
4
4
4
8
variable
29 for CONSOLEB
30 for COM1B
31 for COM2B
24 + (length of pass-through data string received (80 maximum)
Format
char
char
integer
integer
Units
integer
double
char
weeks
seconds
data as received
bytes
Offset
0
3
4
8
12
16
24 + (variable data)
RTK
After setting up your system and initialising the positioning algorithms you can use the logs listed in this chapter to record
the data collected. The low-latency-solution logs (e.g. PRTKA/B) are recommended for kinematic users, while the
matched-solution logs (e.g. RTKA/B) are recommended for stationary users.
A matched solution is always a carrier-phase differential solution, and consequently offers the greatest possible accuracy.
A low-latency solution, on the other hand, is the best one that is currently available; the possibilities are categorised as
follows, starting with the one offering the greatest accuracy and precision:
1.Carrier-phase differential solution
2.Pseudorange differential solution
3.Single-point solution
Therefore, if an RTK solution is not available, then a low-latency-solution log will contain a pseudorange differential
solution if it exists. If neither an RTK nor a pseudorange differential solution is available, then a low-latency-solution log
will contain a single-point solution.
GPSCard™ Command Descriptions Manual Rev 3
117
7 – NMEA Format Data Logs
7
NMEA FORMAT DATA LOGS
GENERAL
The NMEA log structures follow format standards as adopted by the National Marine Electronics Association. The
reference document used is "Standard For Interfacing Marine Electronic Devices NMEA 0183 Version 2.00". For further
information, refer to Appendix D, page 178.
The following table contains excerpts from Table 6 of the NMEA Standard that defines the variables for the NMEA logs.
The actual format for each parameter is indicated after its description.
Field Type
Special Format Fields
Status
Symbol
Definition
A
Latitude
llll.ll
Longitude
yyyyy.yy
Time
hhmmss.ss
Single character field:
A = Yes, Data Valid, Warning Flag ClearV = No, Data Invalid, Warning Flag Set
Fixed/Variable length field:
degrees|minutes.decimal - 2 fixed digits of degrees, 2 fixed digits of minutes and a variable number of
digits for decimal-fraction of minutes. Leading zeros always included for degrees and minutes to maintain
fixed length. The decimal point and associated decimal-fraction are optional if full resolution is not
required.
Fixed/Variable length field:
degrees|minutes.decimal - 3 fixed digits of degrees, 2 fixed digits of minutes and a variable number of
digits for decimal-fraction of minutes. Leading zeros always included for degrees and minutes to maintain
fixed length. The decimal point and associated decimal-fraction are optional if full resolution is not required
Fixed/Variable length field:
hours|minutes|seconds.decimal - 2 fixed digits of hours, 2 fixed digits of minutes, 2 fixed digits of seconds
and variable number of digits for decimal-fraction of seconds. Leading zeros always included for hours,
minutes and seconds to maintain fixed length. The decimal point and associated decimal-fraction are
optional if full resolution is not required.
Some fields are specified to contain pre-defined constants, most often alpha characters. Such a field is
indicated in this standard by the presence of one or more valid characters. Excluded from the list of
allowable characters are the following which are used to indicate field types within this standard:
"A", "a", "c", "hh", "hhmmss.ss", "llll.ll", "x", "yyyyy.yy"
Defined field
Numeric Value Field
Variable numbers
Fixed HEX field
Information Fields
Variable text
Fixed alpha field
Fixed number field
Fixed text field
1.
2.
3.
4.
5.
x.x
hh___
Variable length integer or floating numeric field. Optional leading and trailing zeros. The decimal point and
associated decimal-fraction are optional if full resolution is not required (example: 73.10 = 73.1 = 073.1 =
73)
Fixed length HEX numbers only, MSB on the left
Variable length valid character field.
Fixed length field of uppercase or lowercase alpha characters
Fixed length field of numeric characters
Fixed length field of valid characters
NOTES:
Spaces may only be used in variable text fields.
A negative sign "-" (HEX 2D) is the first character in a Field if the value is negative. The sign is omitted if value is positive.
All data fields are delimited by a comma (,).
Null fields are indicated by no data between two commas (,,). Null fields indicate invalid or no data available.
The NMEA Standard requires that message lengths be limited to 82 characters.
118
c--c
aa___
xx___
cc___
GPSCard™ Command Descriptions Manual Rev 3
7 – NMEA Format Data Logs
GPALM
B
Almanac Data
This log outputs raw almanac data for each satellite PRN contained in the broadcast message. A separate record is logged
for each PRN, up to a maximum of 32 records. Following a GPSCard reboot, no records will be output until new
broadcast message data is received from a satellite. It takes a minimum of 12.5 minutes to collect a complete almanac
following GPSCard boot-up. (The almanac reported here has no relationship to the NovAtel $ALMA almanac injection
command. Following a cold start, the log will output null fields until a new almanac is collected from a satellite.)
Structure:
# msg
$GPALM
omegadot
Field
1
2
3
4
5
6
7
8
9
msg #
rt axis
PRN GPS wk SV hlth
omega
long asc node
Mo
ecc
af0
alm ref time incl angle
af1 *xx [CR][LF]
Structure
$GPALM
# msg
msg #
PRN
GPS wk
SV hlth
ecc
alm ref time
incl angle
Field Description
Log header
Total number of messages logged
Current message number
Satellite PRN number, 01 to 32
GPS reference week number
SV health, bits 17-24 of each almanac page
e, eccentricity
toa, almanac reference time
(sigma)i, inclination angle
10
11
12
13
omegadot
rt axis
omega
long asc node
OMEGADOT, rate of right ascension
(A)1/2, root of semi-major axis
omega, argument of perigee
(OMEGA)o,longitude of ascension node
14
Mo
af0
Mo, mean anomaly
†††
†††
af0, clock parameter
af1
*xx
[CR][LF]
†
af1, clock parameter
15
16
17
18
Symbol
x.x
x.x
xx
x.x
hh
hhhh
hh
hhhh
Example
$GPALM
17
17
28
653
00
3EAF
87
OD68
hhhhhhhh
hhhhhh
hhhhhh
hhhhhh
FFFFFD30
A10CAB
6EE732
525880
hhhhhh
6DC5A8
†††
hhh
009
†††
hhh
005
*hh
*37
[CR][LF]
†
††
†††
†††
†††
†††
†††
†††
Checksum
Sentence terminator
Variable length integer, 4-digits maximum from (2) most significant binary bits of Subframe 1, Word 3 reference Table 20-I, ICD-GPS-200, Rev. B, and (8)
least significant bits from subframe 5, page 25, word 3 reference Table 20-I, ICD-GPS-200, Rev. B, paragraph 20.3.3.5.1.7.
††
Reference paragraph 20.3.3.5.1.3, Table 20-VII and Table 20-VIII, ICD-GPS-200, Rev. B.
†††
Reference Table 20-VI, ICD-GPS-200, Rev. B for scaling factors and units.
Example:
$GPALM,17,17,28,653,00,3EAF,87,0D68,FFFFFD30,A10CAB,6EE732,525880,6DC5A8,009,
005*37[CR][LF]
NOTE:
To obtain copies of ICD-GPS-200, refer to Appendix D, page 178, for address information.
GPSCard™ Command Descriptions Manual Rev 3
119
7 – NMEA Format Data Logs
GPGGA
B (R)
Global Position System Fix Data
Time, position and fix-related data of the GPS receiver. The information contained in this log is also available in the
NovAtel GGAB log in binary format. This log will output all null data fields until the GPSCard has achieved first fix.
Structure:
$GPGGA utc lat
null
Field
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
age stn ID
Structure
$GPGGA
utc
lat
lat dir
lon
lon dir
GPS qual
# sats
hdop
alt
units
null
null
age
stn ID
*xx
[CR][LF]
lat dir
*xx
lon
lon dir GPS qual
# sats hdop
alt
units
null
[CR][LF]
Field Description
Log header
UTC time of position (hours/minutes/seconds/ decimal seconds)
Latitude (DDmm.mm)
Latitude direction (N = North, S = South)
Longitude (DDDmm.mm)
Longitude direction (E = East, W = West)
GPS Quality indicator
0 = fix not available or invalid
1 = GPS fix
2 = Differential GPS fix
†
Number of satellites in use (00-12). May be different to the number in view
Horizontal dilution of precision
Antenna altitude above/below mean sea level (geoid)
Units of antenna altitude, in metres
(This field not available on GPSCards)
(This field not available on GPSCards)
Age of Differential GPS data (in seconds)
†
††
Differential reference station ID, 0000-1023
†
Checksum
Sentence terminator
† Fields 7, 14, and 15 will not report this data unless the GPSCard has the “R” option.
††
Symbol
hhmmss.ss
llll.ll
a
yyyyy.yy
a
x
xx
x.x
x.x
m
xx
xxxx
*hh
Example
$GPGGA
220147.50
5106.7194489
N
11402.3589020
W
1
08
0.9
1080.406
m
,,
,,
,,
,,
*48
[CR][LF]
The maximum age reported here is limited to 99 seconds.
Example:
$GPGGA,220147.50,5106.7194489,N,11402.3589020,W,1,08,0.9,1080.406,M,,,,
*48[CR][LF]
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GPSCard™ Command Descriptions Manual Rev 3
7 – NMEA Format Data Logs
GPGLL
B
Geographic Position – Lat/Lon
Latitude and longitude of present vessel position, time of position fix, and status. This log will output all null data fields
until the GPSCard has achieved first fix.
Structure:
$GPGLL
Field
1
2
3
4
5
6
7
8
9
lat lat dir
Structure
$GPGLL
lat
lat dir
lon
lon dir
utc
data status
*xx
[CR][LF]
lon lon dir
utc data status
Field Description
Log header
Latitude (DDmm.mm)
Latitude direction (N = North, S = South)
Longitude (DDDmm.mm)
Longitude direction (E = East, W = West)
UTC time of position (hours/minutes/seconds/decimal seconds)
Data status: A = Data valid, V = Data invalid
Checksum
Sentence terminator
*xx [CR][LF]
Symbol
llll.ll
a
yyyyy.yy
a
hhmmss.ss
A
*hh
Example
$GPGLL
5106.7198674
N
11402.3587526
W
220152.50
A
*1B
[CR][LF]
Example:
$GPGLL,5106.7198674,N,11402.3587526,W,220152.50,A*1B[CR][LF]
GPGRS
B
GPS Range Residuals for Each Satellite
Range residuals can be computed in two ways, and this log reports those residuals. Under mode 0, residuals output in this
log are used to update the position solution output in the GPGGA message. Under mode 1, the residuals are re-computed
after the position solution in the GPGGA message is computed. The GPSCard computes range residuals in mode 1. An
integrity process using GPGRS would also require GPGGA (for position fix data), GPGSA (for DOP figures), and
GPGSV (for PRN numbers) for comparative purposes.
Structure:
$GPGRS
utc
mode
res res res res res res res res res res res res
*xx [CR][LF]
Field
1
2
3
4 - 15
16
17
Structure
$GPGRS
utc
mode
res
*xx
[CR][LF]
Field Description
Log header
UTC time of position (hours/minutes/seconds/ decimal seconds)
Mode 0 = residuals were used to calculate the position given in the
matching GGA line (apriori) (not used by GPSCard)
Mode 1 = residuals were recomputed after the GGA position was
computed (preferred mode)
Range residuals for satellites used in the navigation solution. Order
matches order of PRN numbers in GPGSA.
Checksum
Sentence terminator
Symbol
hhmmss.ss
x
x.x,x.x,.....
*hh
Example
$GPGRS
192911.0
1
-13.8,-1.9,11.4,-33.6,0.9,
6.9,-12.6,0.3,0.6, -22.3
*65
[CR][LF]
Example:
$GPGRS,192911.0,1,-13.8,-1.9,11.4,-33.6,0.9,6.9,-12.6,0.3,0.6,-22.3,,
*65[CR][LF]
GPSCard™ Command Descriptions Manual Rev 3
121
7 – NMEA Format Data Logs
NOTES:
-
If the range residual exceeds ± 99.9, then the decimal part will be dropped. Maximum value for this field is ± 999.
-
The sign of the range residual is determined by the order of parameters used in the calculation as follows:
range residual = calculated range – measured range.
GPGSA
B
GPS DOP and Active Satellites
GPS receiver operating mode, satellites used for navigation and DOP values.
Structure:
$GPGSA
pdop
Field
1
2
mode MA
hdop
vdop
Structure
$GPGSA
mode MA
3
4 - 15
mode 123
prn
16
17
18
19
20
pdop
hdop
vdop
*xx
[CR][LF]
mode 123
prn prn prn prn prn prn prn prn prn prn prn prn
*xx [CR][LF]
Field Description
Log header
A = Automatic 2D/3D (not used by GPSCard)
M = Manual, forced to operate in 2D or 3D
Mode: 1 = Fix not available; 2 = 2D; 3 = 3D
PRN numbers of satellites used in solution (null for unused fields), total of
12 fields
Position dilution of precision
Horizontal position and time dilution of precision
Vertical dilution of precision
Checksum
Sentence terminator
Symbol
M
x
xx,xx,.....
x.x
x.x
x.x
*hh
Example
$GPGSA
M
3
18,03,13,25,16,
24,12,20,,,,
1.5
0.9
1.2
*3F
[CR][LF]
Example:
$GPGSA,M,3,18,03,13,25,16,24,12,20,,,,,1.5,0.9,1.2*3F[CR][LF]
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7 – NMEA Format Data Logs
GPGST
B
Pseudorange Measurement Noise Statistics
Pseudorange measurement noise statistics are translated in the position domain in order to give statistical measures of the
quality of the position solution.
Structure:
$GPGST
utc
rms
smjr std
smnr std
orient lat std
lon std
alt std
*xx [CR][LF]
Field
1
2
3
4
5
6
7
8
9
10
11
Structure
$GPGST
utc
rms
smjr std
smnr std
orient
lat std
lon std
alt std
*xx
[CR][LF]
Field Description
Log header
UTC time of position (hours/minutes/seconds/ decimal seconds)
RMS value of the standard deviation of the range inputs to the navigation
process. Range inputs include pseudoranges and DGPS corrections.
Standard deviation of semi-major axis of error ellipse (metres)
Standard deviation of semi-minor axis of error ellipse (metres)
Orientation of semi-major axis of error ellipse (degrees from true north)
Standard deviation of latitude error (metres)
Standard deviation of longitude error (metres)
Standard deviation of altitude error (metres)
Checksum
Sentence terminator
Symbol
hhmmss.ss
x.x
x.x
x.x
x.x
x.x
x.x
x.x
*hh
Example
$GPGST
192911.0
28.7
21.6
12.0
20.4
20.7
13.6
11.9
*51
[CR][LF]
Example:
$GPGST,192911.0,28.7,21.6,12.0,20.4,20.7,13.6,11.9*51[CR][LF]
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7 – NMEA Format Data Logs
GPGSV
B
GPS Satellites in View
Number of SVs in view, PRN numbers, elevation, azimuth and SNR value. Four satellites maximum per message. When
required, additional satellite data sent in second or third message. Total number of messages being transmitted and the
current message being transmitted are indicated in the first two fields.
Structure:
$GPGSV
prn
# msg
msg #
# sats
elev
azimuth
SNR
elev
azimuth
SNR
:
prn
Field
1
2
3
4
5
6
7
8
9-12
13-16
17-20
21
22
1 - 22
1 - 22
*xx [CR][LF]
Structure
$GPGSV
# msg
msg #
# sats
prn
elev
azimuth
SNR
Field Description
Log header
Total number of messages, 1 to 3
Message number, 1 to 3
Total number of satellites in view
Satellite PRN number
Elevation, degrees, 90° maximum
Azimuth, degrees True, 000 to 359
SNR (C/N0) 00-99 dB, null when not tracking
*xx
[CR][LF]
2nd satellite PRN number, elev, azimuth, SNR,
3rd satellite PRN number, elev, azimuth, SNR,
4th satellite PRN number, elev, azimuth, SNR
Checksum
Sentence terminator
Symbol
x
x
xx
xx
xx
xxx
xx
xx,xx,xxx,xx,
xx,xx,xxx,xx,
xx,xx,xxx,xx
*hh
Example
$GPGSV
3
1
09
03
51
140
42
16,02,056,40,
17,78,080,42,
21,25,234,00
*72
[CR][LF]
2nd $GPGSV message (optional)
3rd $GPGSV message (optional)
Example:
$GPGSV,3,1,09,03,51,140,42,16,02,056,40,17,78,080,42,21,25,234,00*72[CR][LF]
$GPGSV,3,2,09,22,19,260,00,23,59,226,00,26,45,084,39,27,07,017,39*78[CR][LF]
$GPGSV,3,3,09,28,29,311,44*42[CR][LF]
NOTES:
-
Satellite information may require the transmission of multiple messages. The first field specifies the total number of
messages, minimum value 1. The second field identifies the order of this message (message number), minimum
value 1.
-
A variable number of ’prn-Elevation-Azimuth-snr’ sets are allowed up to a maximum of four sets per message. Null
fields are not required for unused sets when less than four sets are transmitted.
-
GPGSV logs will not output until time of first fix.
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7 – NMEA Format Data Logs
GPRMB
B
Navigation Information
Navigation data from present position to a destination waypoint. The destination is set active by the GPSCard SETNAV
command. If SETNAV has been set, a command to log either GPRMB or GPRMC will cause both logs to output data.
Structure:
$GPRMB
dest lon
Field
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
data status
lon dir
Structure
$GPRMB
data status
xtrack
dir
origin ID
dest ID
dest lat
lat dir
dest lon
lon dir
range
bearing
vel
arr status
*xx
[CR][LF]
†
xtrack
range
dir
bearing
origin ID dest ID
vel arr status
dest lat
*xx
Field Description
Log header
Data status: A = data valid; V = navigation receiver warning
Cross track error – nautical miles
†
Direction to steer to get back on track (L/R)
††
Origin waypoint ID
†††
Destination waypoint ID
†††
Destination waypoint latitude (DDmm.mm)
†††
Latitude direction (N = North, S = South)
†††
Destination waypoint longitude (DDDmm.mm) †††
Longitude direction (E = East, W = West)
†††
Range to destination, nautical miles
††††
Bearing to destination, degrees True
Destination closing velocity, knots
Arrival status: A = perpendicular passed,
V = destination not reached or passed
Checksum
Sentence terminator
lat dir
[CR][LF]
Symbol
A
x.x
a
c--c
c--c
llll.ll
a
yyyyy.yy
a
x.x
x.x
x.x
A
*hh
Example
$GPRMB
V
0.011
L
START
END
5106.7074000
N
11402.3490000
E
0.0127611
153.093
0.3591502
V
*13
[CR][LF]
– If cross track error exceeds 9.99 NM, display 9.99
– Represents track error from intended course
– one nautical mile = 1,852 m
††
Direction to steer is based on the sign of the crosstrack error,
†††
Fields 5, 6, 7, 8, 9, and 10 are tagged from the GPSCard SETNAV command.
††††
If range to destination exceeds 999.9 NM, display 999.9
i.e., L = xtrack error (+); R = xtrack error (–)
Example:
$GPRMB,V,0.011,L,START,END,5106.7074000,N,11402.3490000,W,0.0127611,153093,
0.3591502,V*13[CR][LF]
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7 – NMEA Format Data Logs
GPRMC
B
GPS Specific Information
Time, date, position, track made good and speed data provided by the GPS navigation receiver. RMC and RMB are the
recommended minimum navigation data to be provided by a GPS receiver. This log will output all null data fields until
the GPSCard has achieved first fix.
Structure:
$GPRMC
utc pos status
mag var
Field
1
2
3
4
5
6
7
8
9
10
11
var dir
*xx
lat lat dir
lon
lon dir
speed Kn
track true
date
[CR][LF]
Structure
$GPRMC
utc
pos status
lat
lat dir
lon
lon dir
speed Kn
track true
date
mag var
Field Description
Log header
UTC of position
Position status: A = data valid; V = data invalid
Latitude (DDmm.mm)
Latitude direction (N = North, S = South)
Longitude (DDDmm.mm)
Longitude direction (E = East, W = West)
Speed over ground, knots
Track made good, degrees True
Date: dd/mm/yy
Magnetic variation, degrees 2
12
var dir
13
14
*xx
[CR][LF]
Magnetic variation direction E/W1
Checksum
Sentence terminator
Symbol
hhmmss.ss
A
llll.ll
a
yyyyy.yy
a
x.x
x.x
xxxxxx
x.x
Example
$GPRMC
220216.50
A
5106.7187663
N
11402.3581636
W
0.3886308
130.632
150792
0.000
a
E
*hh
*4B
[CR][LF]
Example:
$GPRMC,220216.50,A,5106.7187663,N,11402.3581636,W,0.3886308,130.632,150792,
0.000,E*4B[CR][LF]
NOTES:
-
Easterly variation (E) subtracts from True course
Westerly variation (W) adds to True course
-
Note that this field is the actual magnetic variation East or West and is the inverse sign of the value entered into the
MAGVAR command. See MAGVAR, page 37, for more information.
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7 – NMEA Format Data Logs
GPVTG
B
Track Made Good And Ground Speed
The track made good and speed relative to the ground.
Structure:
$GPVTG track true
Field
1
2
3
4
5
6
7
8
9
10
11
T
Structure
$GPVTG
track true
T
track mag
track mag M
speed Kn
N
speed km
Field Description
Log header
Track made good, degrees True
True track indicator
Track made good, degrees Magnetic;
Track mag = Track true + (MAGVAR correction)
See MAGVAR command, page 37.
Magnetic track indicator
Speed over ground, knots
Nautical speed indicator (N = Knots)
Speed, kilometers/hour
Speed indicator (K = km/hr)
Checksum
Sentence terminator
M
speed Kn
N
speed km
K
*xx
[CR][LF]
K
Symbol
x.x
T
x.x
M
x.x
N
x.x
K
*hh
*xx [CR][LF]
Example
$GPVTG
24.168
T
24.168
M
0.4220347
N
0.781608
K
*7A
[CR][LF]
Example:
$GPVTG,24.168,T,24.168,M,0.4220347,N,0.781608,K*7A[CR][LF]
GPZDA
B
UTC Time and Date
This log will output all null data fields until the GPSCard has achieved first fix.
Structure:
$GPZDA utc day month
Field
1
2
3
4
5
6
7
8
9
year
null
null
*xx [CR][LF]
Structure
$GPZDA
utc
day
month
year
null
null
Field Description
Log header
UTC time
Day, 01 to 31
Month, 01 to 12
Year
Local zone description - not available
Local zone minutes description 1 - not available
*xx
[CR][LF]
Checksum
Sentence terminator
Symbol
hhmmss.ss
xx
xx
xxxx
xx
xx
*hh
Example
$GPZDA
220238.00
15
07
1992
,,
,,
*6F
[CR][LF]
Example:
$GPZDA,220238.00,15,07,1992,00,00*6F[CR][LF]
1 NOTE:
The GPSCard does not support Local time zones. Fields 6 and 7 will always be null.
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7 – NMEA Format Data Logs
GPZTG
B
UTC & Time to Destination Waypoint
This log reports time to destination waypoint. Waypoint is set using the GPSCard SETNAV command. If destination
waypoint has not been set with SETNAV, time-to-go and destination waypoint ID will be null. This log will output all
null data fields until the GPSCard has achieved first fix.
Structure:
$GPZTG utc time
Field
1
2
3
4
5
6
Structure
$GPZTG
utc
time
dest ID
*xx
[CR][LF]
dest ID
*xx
[CR][LF]
Field Description
Log header
UTC of position
Time to go (995959.00 maximum reported)
Destination waypoint ID
Checksum
Sentence terminator
Symbol
hhmmss.ss
hhmmss.ss
c--c
*hh
Example
$GPZTG
220245.00
994639.00
END
*36
[CR][LF]
Example:
$GPZTG,220245.00,994639.00,END*36[CR][LF]
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GPSCard™ Command Descriptions Manual Rev 3
8 – RTCM Commands and Logs
8
RTCM STANDARD COMMANDS AND LOGS
The Global Positioning System is a world-wide positioning service developed by the U.S. Department of Defense (DOD)
and is operated and maintained by the U.S. Air Force Space Division. As usage of the GPS Standard Positioning Service
(SPS) has gained world wide commercial acceptance, the applications have become wide and varied. Of special
importance have been the developments in the use of differential GPS (DGPS). DGPS enables system users to leap from
nominal 100 m system accuracies (single point) to the more desirable 1 - 5 m nominal accuracies possible from utilizing
differential corrections between reference and remote stations.
As DGPS systems exist all over the world, the need arose to establish a set of operating standards that all DGPS receivers
could use for the purpose of transmitting and receiving differential corrections between GPS receivers of various types,
regardless of receiver design or manufacturer.
The Radio Technical Commission for Maritime Services (RTCM) was established to facilitate the establishment of
various radionavigation standards, which includes recommended GPS differential standard formats.
The standards recommended by the Radio Technical Commission for Maritime Services Special Committee 104,
Differential GPS Service (RTCM SC-104,Washington, D.C.), have been adopted by NovAtel for implementation into the
GPSCard receivers with the “R” option. Because the GPSCard is capable of utilizing RTCM formats, it can easily be
integrated into positioning systems around the globe.
As it is beyond the scope of this manual to provide in-depth descriptions of the RTCM data formats, it is recommended
that anyone requiring explicit descriptions of such, should obtain a copy of the published RTCM specifications. See
Appendix D, page 178, for reference information.
RTCM GENERAL MESSAGE FORMAT
All GPSCard RTCM standard format logs adhere to the structure recommended by RTCM SC-104. Thus, all RTCM
message are composed of 30 bit words. Each word contains 24 data bits and 6 parity bits. All RTCM messages contain a
2-word header followed by 0 to 31 data words for a maximum of 33 words (990 bits) per message.
Message Frame Header
Word 1
Data
–
Message frame preamble for synchronization
–
Frame/message type ID
–
Reference station ID
–
Parity
Word 2
–
–
–
–
–
Modified z-count (time tag)
Sequence number
Length of message frame
Reference station health
Parity
Bits
8
6
10
6
13
3
5
3
6
The remainder of this chapter will provide further information concerning GPSCard commands and logs that utilize the
RTCM data formats.
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8 – RTCM Commands and Logs
GPSCard COMMANDS
All of the GPSCard commands that follow are only available with the “R” option.
R
RTCMRULE
The RTCM standard states that all equipment shall support the use of the “6 of 8” format (data bits a1 through a6 where
bits a1 through a6 are valid data bits and bit a7 is set to mark and bit a8 is set to space.
The GPSCard RTCMRULE command allows for flexibility in the use of the bit rule to accommodate compatibility with
equipment that does not strictly adhere to the RTCM stated rule.
Syntax:
RTCMRULE
Syntax
RTCMRULE
rule
rule
Range Value
6CR
6SP
6
8
Description
Command
6CR is for 6 bits of valid data per byte. A <CR> character follows each frame.
6SP (6 bit special); the RTCM decoder of the remote receiver will ignore the two MSB of the
data and hence all 6 bit data will be accepted. This allows users with non-conforming 6 bit
rule data to use the NovAtel receiver to accept their RTCM data. The user will not be allowed
to enter extra control data such as CR/LF, as this will be treated as RTCM data and cause
the parity to fail. This option does not affect RTCM generation. The output will be exactly the
same as if the RTCMRULE 6 option was chosen. The upper two bits are always encoded as
per RTCM specification.
6 is for 6 bits of valid data per byte
8 is for 8 bits of valid data per byte
Default
6CR
Example:
rtcmrule 6cr
R
RTCM16T
This is a NovAtel GPSCard command that relates to the RTCM Type 16 – Special Message.
This command allows the GPSCard user to set an ASCII text string. Once set, the text string can be transmitted as
standard format RTCM Type 16 data (refer to the RTCM16 log, page 100). The text string entered is limited to a
maximum of 90 ASCII characters. This message is useful for a reference station wanting to transmit special messages to
remote users.
The text string set here can be verified by observing the RCCA command configuration log. As well, the message text
can be transmitted as a NovAtel Format ASCII log by utilizing the “LOG port RTCM16T” command.
Syntax:
RTCM16T
Syntax
RTCM16T
message
message
Range Value
up to 90 characters
Description
Command
ASCII text message
Example:
rtcm16t This is a test of the RTCM16T Special Message.
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8 – RTCM Commands and Logs
GPSCard LOGS
All of the GPSCard logs that follow are only available with the “R” option.
R
RTCM
This is the primary RTCM log used for pseudorange differential corrections. This log follows RTCM Standard Format
for Type 1 messages. It contains the pseudorange differential correction data computed by the reference station
generating this Type 1 log. The log, depending on the number of satellites visible and pseudoranges corrected by the
reference station, is of variable length. Satellite specific data begins at word 3 of the message.
Structure:
(Follows RTCM Standard for Type 1 message)
Type 1 messages contain the following information for each satellite in view at the reference station:
•
•
•
•
Satellite ID
Pseudorange correction
Range-rate correction
Issue of Data (IOD)
When operating as a reference station, the GPSCard must be in FIX POSITION mode before the data can be correctly
logged.
When operating as a remote station, the GPSCard COM port receiving the RTCM data must have its ACCEPT command
set to “ACCEPT port RTCM”.
REMEMBER: Upon a change in ephemeris, GPSCard reference stations will transmit Type 1 messages based on the
old ephemeris for a period of time defined by the dgpstimeout command. After the timeout, the reference station will
begin to transmit the Type 1 messages based on new ephemeris.
RTCMA
R
This log contains the same data available in the RTCM Standard Format Type 1 messages, but has been modified to
allow flexibility in using the RTCM data. The RTCM data has been reformatted to be available in ASCII hexadecimal,
utilizing a NovAtel header and terminates with a checksum.
This message was designed so that RTCM data can be intermixed with other NovAtel ASCII data over a common
communications port. The log is not in pure RTCM SC104 format. The header ($RTCM) and terminator (*xx) must be
stripped off at the receiving end, then the data will need to be converted from hexadecimal to binary before the RTCM
information is retrieved. The RTCM data is further defined by the RTCM rule (refer to the RTCMRULE command, page
40).
Other NovAtel GPSCard receivers operating as remote stations can directly decode The RTCMA log. They will
recognize the $RTCM header as a special data input command and the differential correction data will be directly
applied. The GPSCard remote station receiving this log must have the ACCEPT command set to “ACCEPT port
COMMANDS”.
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8 – RTCM Commands and Logs
Structure:
$RTCM
Field #
1
2
3
4
rtcm data
*xx
[CR][LF]
Field Type
$RTCM
rtcm data
Data Description
NovAtel format ASCII header
hexadecimal representation of binary
format RTCM SC104 data
*xx
[CR][LF]
Checksum
Sentence terminator
Example
$RTCM
664142406B61455F565F7140607E5D526A5366C7
C7F6F5A5B766D587D7F535C4B697F54594060685
652625842707F77555B766558767F715B7746656B
*54
[CR][LF]
Example:
$RTCM,664142406B61455F565F7140607E5D526A5366C7C7F6F5A5B766D587D7F535C4B6
97F54594060685652625842707F77555B766558767F715B7746656B*54[CR][LF]
R
RTCMB
This log contains the same data available in the RTCM Standard Format Type 1 messages, but has been modified to
allow flexibility in using the RTCM data. The RTCM data has been reformatted to be available in NovAtel Binary
Format, utilizing a NovAtel binary header.
This message was designed so that RTCM data can be transmitted intermixed with other NovAtel binary data over a
common communications port. The log is not in pure RTCM SC104 format and is not directly usable as such. GPSCard
remote receivers cannot decode or interpret the RTCMB data (however, the GPSCard can directly interpret RTCM and
RTCMA). The 12 byte NovAtel binary header must be stripped off before the RTCM information can be retrieved. The
RTCM data is further defined by the RTCM rule (refer to the RTCMRULE command, page 40).
REMEMBER: Ensure that the RTCM rule is the same between all equipment.
Format:
Field #
1
(header)
2
RTCM3
Message ID = 10
Data
Sync
Checksum
Message ID
Message byte count
Data
Message byte count = variable
Bytes
3
1
4
4
variable
Format
char
char
integer
integer
Units
bytes
RTCM SC104 data
Offset
0
3
4
8
12
R
The RTCM Type 3 log contains the reference position of the reference station expressed in ECEF XYZ WGS-84
parameters (regardless of the local operating datum).
This log uses four RTCM data words following the header, for a total frame length of six 30 bit words (180 bits
maximum).
The GPSCard only transmits the RTCM Type 3 message (RTCM3) when operating as a reference station paired with
GPSCard remote receivers operating in RT-20 Carrier Phase Mode. (Refer to Chapter 11, page 148, for more
information.)
GPSCard remote receivers must utilize the “ACCEPT port RT20” before the RTCM3 data can be decoded and processed.
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8 – RTCM Commands and Logs
NOTE: This log is intended for use when operating in RT-20 mode.
R
RTCM16
This log contains special ASCII text information as set by the reference station. The default setting for the RTCM16 data
log follows RTCM Standard Format. Words 1 and 2 contain RTCM header information followed by words 3 to n (where
n is variable from 3 to 32) which contain the special message ASCII text. Up to 90 ASCII characters can be sent with
each RTCM Type 16 message frame.
Structure (variable):
•
RTCM Standard format Type 16 message when used with RTCM Type 1 log.
•
NovAtel ASCII hex version when used with RTCMA Type 1 log.
•
NovAtel binary version when used with RTCMB Type 1 log.
For GPSCards operating as a reference station, the RTCM16 message can be logged out to remote stations capable of
receiving RTCM Type 16 messages. The GPSCard reference station must use the RTCM16T command to set the
required ASCII text message. Once set, the message can then be issued at the required intervals with the “LOG port
RTCM16 interval” command. If the reference station desires that only updated text messages be transmitted, it is
recommended that the GPSCard log interval be set to “onnew” or “onchanged”.
GPSCard receivers operating as remote stations must have the ACCEPT command set to ACCEPT port RTCM before
the GPSCard will decode the RTCM Standard Format messages.
GPSCard receivers, operating as remote stations, do not require any special settings to receive the RTCM16 message
when received as NovAtel ASCII hexadecimal format (refer to the RTCMA log, page 100, for handling of RTCMA
ASCII hexadecimal data). However the ACCEPT command must be set to “COMMANDS”.
The NovAtel binary version of RTCM16 cannot be directly decoded by a GPSCard receiver (refer to the RTCMB log,
page 100, for handling of RTCMB binary data).
REMEMBER: The default format is RTCM16 Standard Format. However, the format of the RTCM16 message will
change to be the same as the last RTCM differential corrections format used for differential corrections (RTCM,
RTCMA, or RTCMB). For example, if an RTCMA log was the last log format transmitted on com1 to send differential
corrections, then issuing the command “log com1 rtcm16” will transmit the message in NovAtel ascii hex format.
R
RTCM16T
This NovAtel Format ASCII log is used to report the contents of the RTCM Type 16 Special Message. If the GPSCard
sending this log is operating as a reference station, the log is used to report the Special Message settings of the GPSCard
RTCM16T command. (The Special Message setting can also be verified in the RCCA configuration log.)
If the GPSCard sending this log is operating as a remote station, it can be used to report to the user the RTCM Type 16
Special Message received over the data link from the reference station.
Structure:
$RTCM16T
ASCII Special Message of up to 90 characters
*xx
[CR][LF]
When logging RTCM16T messages, it is recommended that you use the “onnew” or “onchanged” logging trigger; this
will avoid unnecessary repetition of old messages.
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8 – RTCM Commands and Logs
RT20 (51)
RTCM59
RTCM Type 59 messages are reserved for proprietary use by RTCM reference station operators. NovAtel has defined
this message as a Type 59N message and has dedicated its use for operation in GPSCard receivers capable of operating in
RT-20 Carrier Phase Differential Positioning Mode.
This log is primarily used by GPSCard receivers to broadcast RT-20 reference station observation data to remote RT-20–
capable GPSCard receivers. This log may be variable in length, up to the RTCM maximum of 990 data bits (33 words
maximum).
Remote GPSCard receivers must utilize the “ACCEPT port RT20” command to decode the Type 59N data.
NOTES:
-
The CDSA/B log is very useful for monitoring the serial data link, as well as differential data decode success.
-
This log is intended for use when operating in RT-20 mode. GPSCards with the RT-20 option can transmit or
receive this log, however GPSCard models xx51r can only transmit this log.
RTCM RECEIVE ONLY DATA
The following RTCM data types can be received and decoded by the GPSCard, however these log types are no longer
transmitted.
R
RTCM Type 2
Quite often a reference station may have new ephemeris data before remote stations have collected the newer ephemeris.
The purpose of Type 2 messages is to act as a bridge between old and new ephemeris data. A reference station will
transmit this Type 2 bridge data concurrently with Type 1’s for a few minutes following receipt of a new ephemeris. The
remote station adds the Type 2 data (delta of old ephemeris minus new ephemeris) to the Type 1 message data (new
ephemeris) to calculate the correct pseudorange corrections (based on the old ephemeris). Once the remote receiver has
collected its own updated ephemeris, it will no longer utilize the Type 2 messages.
The GPSCard will accept and decode RTCM Standard Type 2 messages, when available and if required. However, the
GPSCard no longer transmits Type 2 messages.
Type 2 messages are variable in length, depending on the number of satellites being tracked by the reference station.
R
RTCM Type 9
RTCM Type 9 messages follow the same format as Type 1 messages. However, unlike Type 1 messages, Type 9’s do
not require a complete satellite set. This allows for much faster differential correction data updates to the remote stations,
thus improving performance and reducing latency.
The reference station transmitting the Type 9 corrections must be operating with a high stability clock to prevent
degradation of navigation accuracy due to unmodelled clock drift that can occur between Type 9 messages.
All GPSCards with the “R” option are capable of receiving and decoding Type 9 messages.
NOTE: Currently, Type 9 messages are not transmitted from GPSCard reference stations (unless specially configured).
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9 – RTCA Standard
9
RTCA STANDARD LOGS
The RTCA (Radio Technical Commission for Aviation Services) Standard is being designed to support Differential
Global Navigation Satellite System (DGNSS) Special Category I (SCAT-I) precision instrument approaches. The RTCA
Standard is in a preliminary state. Described below is NovAtel’s current support for this Standard. It is based on
“Minimum Aviation System Performance Standards DGNSS Instrument Approach System: Special Category I (SCATI)” dated August 27, 1993 (RTCA/DO-217).
GPSCard LOGS
Only GPSCard receivers with the “R” option can generate or utilize RTCA logs.
R
RTCA
This log enables transmission of RTCA Standard format Type 1 messages from the GPSCard when operating as a
reference station. Before this message can be transmitted, the GPSCard FIX POSITION command must be set. The
RTCA log will be accepted by a GPSCard operating as a remote station over a COM port after an ACCEPT port RTCA
command is issued.
The RTCA Standard for SCAT-I stipulates that the maximum age of differential correction (Type 1) messages accepted
by the remote station cannot be greater than 22 seconds. Refer to the DGPSTIMEOUT command, page 27, in Chapter 2,
for information regarding DGPS delay settings.
The RTCA Standard also stipulates that a reference station shall wait five minutes after receiving a new ephemeris before
transmitting differential corrections. Refer to the DGPSTIMEOUT command, page 27, for information regarding
ephemeris delay settings.
The basic SCAT-I Type 1 differential correction message is as follows:
Format:
Message length = 11 + (6*obs) : (83 bytes maximum)
Field Type
SCAT-I header
Data
–
Message block identifier
–
Reference station ID
(this field will always report 00000001)
–
Message type
–
Message length
Type 1 header
–
–
–
–
–
–
–
Type 1 data
CRC
Modified z-count
Acceleration error bound
Satellite ID
Pseudorange correction
Issue of data
Range rate correction
UDRE
(In the GPSCard, this field will report 000)
†
†
Cyclic redundancy check
† The pseudorange correction and range rate correction fields have a range of ±655.34 m and ±4.094 m/s respectively.
Bits
8
24
8
8
13
3
6
16
8
12
6
Bytes
6
2
6 *obs
3
Any satellite that exceeds these limits will
not be included.
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135
9 – RTCA Standard
R
RTCAA
This log contains the same data available in the RTCA SCAT-I message, but has been modified to allow flexibility in
using the RTCA data. The RTCA data has been reformatted to be available in ASCII hexadecimal, utilizing a NovAtel
header and terminates with a checksum.
This message was designed so that RTCA data can be intermixed with other NovAtel ASCII data over a common
communications port. The log is not in pure RTCA format. The header ($RTCA) and terminator (*xx) must be stripped
off at the receiving end, then the data will need to be converted from hexadecimal to binary before the RTCA information
is retrieved.
Other NovAtel GPSCard receivers, operating as remote stations, can directly decoded the RTCAA log. They will
recognize the $RTCA header as a special data input command and the differential correction data will be directly applied.
The GPSCard remote station receiving this log must have the ACCEPT command set to “ACCEPT port COMMANDS”.
Structure:
$RTCA
Field #
1
2
3
4
rtca data
*xx
[CR][LF]
Field Type
$RTCA
SCAT-I
Data Description
Log header
SCAT-I type 1 differential
corrections
*x x
[CR][LF]
Checksum
Example
$RTCA
990000000447520607BE7C92FA0B82423E9FE507DF5F3FC9FD0
71AFC7FA0D207D090808C0E045BACC055E9075271FFB020041
3F43FF810049C9DFF8FFD074FCF3C940504052DFB
*20
[CR][LF]
Example:
$RTCA,990000000447520607BE7C92FA0B82423E9FE507DF5F3FC9FD071AFC7FA0D207D090808C0E
045BACC055E9075271FFB0200413F43FF810049C9DFF8FFD074FCF3C940504052DFB*20[CR][LF]
R
RTCAB
The RTCAB log contains the SCAT-I differential corrections message with the standard NovAtel binary log preamble
(header) added. The GPSCard, over a COM port, after an “ACCEPT PORT RTCA” command is issued, will accept the
RTCAB log.
Format:
Field #
1
(header)
2
3
4
5
6
136
Message ID = 38
Message byte count = 12 + (11+(6*obs)) : 95 bytes maximum
Data
Bytes
Sync
3
Checksum
1
Message ID
4
Message byte count
4
– Message block identifier
6
–
Reference station ID
–
Message type
–
Message length
– Modified z-count
2
–
Acceleration error bound
– Satellite ID
6
–
Pseudorange correction
–
Issue of data
–
Range rate correction
–
UDRE
Next PRN offset = 26 + (6*obs) where obs varies from 0 to (obs1)
CRC
3
Format
char
char
integer
integer
Units
bytes
Offset
0
3
4
8
12
18
20
GPSCard™ Command Descriptions Manual Rev 3
Appendix A
10
PSEUDORANGE DIFFERENTIAL POSITIONING
GPS SYSTEM ERRORS
In general, GPS SPS C/A code single point pseudorange positioning systems are capable of absolute position accuracies
of about 100 m or less. This level of accuracy is really only an estimation, and may vary widely depending on numerous
GPS system biases, environmental conditions, as well as the GPS receiver design and engineering quality.
There are numerous factors that influence the single point position accuracies of any GPS C/A code receiving system. As
the following list will show, a receiver’s performance can vary widely when under the influences of these combined
system and environmental biases.
•
Ionospheric Group Delays – The earth’s ionospheric layers cause varying degrees of GPS signal propagation
delay. Ionization levels tend to be highest during daylight hours causing propagation delay errors of up to 30
m, whereas night time levels are much lower and may be up to 6 m.
•
Tropospheric Refraction Delays – The earth’s tropospheric layer causes GPS signal propagation delays that
biases the range measurement. The amount of delay is at the minimum (about 3 m) for satellite signals
arriving from 90 degrees above the horizon (overhead), and progressively increases as the angle above the
horizon is reduced to zero where delay errors may be as much as 50 m at the horizon.
•
Ephemeris Errors – Some degree of error always exists between the broadcast ephemeris’ predicted satellite
position and the actual orbit position of the satellites. These errors will directly affect the accuracy of the
range measurement.
•
Satellite Clock Errors – Some degree of error also exists between the actual satellite clock time and the clock
time predicted by the broadcast data. This broadcast time error will cause some bias to the pseudorange
measurements.
•
Receiver Clock Errors – Receiver clock error is the time difference between GPS receiver time and true GPS
time. All GPS receivers have differing clock offsets from GPS time that vary from receiver to receiver by an
unknown amount depending on the oscillator type and quality (TCXO vs. OCXO, etc.). However, because a
receiver makes all of its single point pseudorange measurements using the same common clock oscillator, all
measurements will be equally offset, and this offset can generally be modeled or quite accurately estimated to
effectively cancel the receiver clock offset bias. Thus, in single point positioning, receiver clock offset is not
a significant problem. However, in pseudorange differential operation, between-receiver clock offset is a
source of uncorrelated bias.
•
Selective Availability (SA) – Selective availability is when the GPS Control Segment intentionally dithers
satellite clock timing and broadcast orbit data to cause reduced positioning accuracy for general purpose GPS
SPS users (non-military). When SA is active, range measurements may be biased by as much as 30 m.
•
Multipath Signal Reception – Multipath signal reception can potentially cause large pseudorange and carrier
phase measurement biases. Multipath conditions are very much a function of specific antenna site location
versus local geography and man-made structural influences. Severe multipath conditions could skew range
measurements by as much as 100 m or more. (See Chapter 12, page 158, for more information about
multipath).
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Appendix A
The NovAtel GPSCard Series of receivers are capable of absolute single point positioning accuracies of 15 m CEP
(GDOP < 2; no multipath) when SA is off and 40 m CEP while SA is on. (As the status of selective availability is
generally unknown by the real-time GPS user, the positioning accuracy should be considered to be that of when SA is
on).
The general level of accuracy available from single point operation may be suitable for many types of positioning such as
ocean going vessels, general aviation, and recreational vessels that do not require position accuracies of better than 100 m
CEP. However, increasingly more and more applications desire and require a much higher degree of accuracy and
position confidence than is possible with single point pseudorange positioning. This is where differential GPS (DGPS)
plays a dominant role in higher accuracy real-time positioning systems.
DUAL STATION DIFFERENTIAL POSITIONING
It is the objective of operating in differential mode to either eliminate or greatly reduce most of the errors introduced by
the above types of system biases. Pseudorange differential positioning is quite effective in largely removing most of the
biases caused by satellite clock error, ionospheric and tropospheric delays (for baselines less than 50 km), ephemeris
prediction errors, and SA. However, the biases caused by multipath reception and receiver clock offset are uncorrelated
between receivers and thus cannot be cancelled by “between receiver single differencing” operation.
Differential operation requires that stations operate in pairs. Each pair consists of a reference station and a remote
station. A differential network could also be established when there is more than one remote station linked to a single
reference station.
In order for the differential pair to be effective, differential positioning requires that both reference and remote station
receivers track and collect satellite data simultaneously from common satellites. When the two stations are in relatively
close proximity (< 50 km), the pseudorange bias errors are considered to be nearly the same and can be effectively
cancelled by the differential corrections. However, if the baseline becomes excessively long, the bias errors begin to
decorrelate, thus reducing the accuracy or effectiveness of the differential corrections.
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Appendix A
Figure 10-1 Typical Differential Configuration
Radio Data Link
GPSAntenna
With Chokering
Differential
Corrections
Input
Modem
Differential
Corrections
Output
GPS Receiver
Reference Station
Remote Station
(OEM or PC Performance
Series GPSCard)
(OEM or PC Performance
Series GPSCard)
GPSCard™ Command Descriptions Manual Rev 3
139
Appendix A
THE REFERENCE STATION
The nucleus of the differential network is the reference station. To function as a reference station, the GPS receiver
antenna must be positioned at a bench-mark whose position is fixed and of known precision. Typically, the fixed position
will be that of a geodetic marker or a pre-surveyed point of known accuracy.
The reference receiver must then be initialized to fix its position to agree with the latitude, longitude, and height of the
phase centre of the reference station GPS receiver antenna. Of course, the antenna offset position from the marker must
be accurately accounted for.
Because the reference station’s position is fixed at a known location, it can now compute the range of its known position
to the satellite. The reference station now has two range measurements with which to work: computed pseudoranges
based on its known position relative to the satellite, and measured pseudoranges which assumes the receiver position is
unknown. Now, the reference station’s measured pseudorange (unknown position) is differenced against the computed
range (based on known position) to derive the differential correction which represents the difference between known and
unknown solutions for the same antenna. This difference between the two ranges represents the combined pseudorange
measurement errors resulting from atmospheric delays, satellite clock error, orbital errors, and SA.
The reference station will derive pseudorange corrections for each satellite being tracked. These corrections can now be
transmitted over a data link to one or more remote stations. It is important to ensure that the reference station’s FIX
POSITION setting be as accurate as possible, as any errors here will directly bias the pseudorange corrections computed.
As well, the reference station’s pseudorange measurements may be biased by multipath reception. Refer to Chapter 12,
page 158, for further discussions on multipath issues.
THE REMOTE STATION
A remote station is generally any receiver whose position is of unknown accuracy, but has ties to a reference station
through an established data link. If the remote station is not receiving differential corrections from the reference station,
it is essentially utilizing single point positioning measurements for its position solutions, thus is subject to the various
GPS system biases. However, when the remote GPS receiver is receiving a pseudorange correction from the reference
station, this correction is algebraically summed against the local receiver’s measured pseudorange, thus effectively
canceling the effects of orbital and atmospheric errors (assuming baselines < 50 km), as well as eliminating satellite clock
error.
The remote must be tracking the same satellites as the reference in order for the corrections to take effect. Thus, only
common satellites will utilize the differential corrections. When the remote is able to compute its positions based on
pseudorange corrections from the reference, its position accuracies will approach that of the reference station.
Remember, the computed position solutions are always that of the GPS receiving antenna phase centre.
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Appendix A
THE GPSCard AND DIFFERENTIAL POSITIONING
The NovAtel GPSCard Performance Series receivers with the “R” option are capable of operation utilizing pseudorange
“between-receiver single differencing” techniques. The accuracy gains are quite substantial for GPSCard receivers
operating as a differential “remote station” as compared to single point positioning. Previously, it was stated that a
GPSCard operating in single point mode is capable of absolute position accuracies of about 40 m CEP (SA on). Now,
when two GPSCards are operated as a differential pair (one reference and one remote), the remote receiver is capable of
absolute position accuracies of 2 m or less when operated with the GPSAntenna model 501 (no choke ring ground plane,
low multipath). And, when operated with the GPSAntenna 501 with the NovAtel Choke Ring Ground Plane,
pseudorange position accuracies of less than 1 m are possible. If the receivers have the “RM” option (Real-time
differential, and MET - Multipath Elimination Technology), then absolute position accuracies of 0.75 m are achievable.
To achieve accuracies better than 0.75 m, the GPSCard user will require the GPSCard RT-20 option. Refer to Chapter
11, page 148, for more information about RT-20.
OPERATING THE GPSCard IN DIFFERENTIAL MODES
Any OEM or PC Series GPSCard with the “R” option is capable of operating in differential mode. As well, these
receivers are capable of operating as either a reference station or a remote station. This makes the GPSCard Series ideal
for design into DGPS systems.
The GPSCard is capable of utilizing various formats of differential corrections. These formats are divided into three
primary groups. Refer to Table 10-1, page 141, for a list of these formats.
For detailed data structure information concerning these logs, please refer to Chapter 4, page 52, Chapter 5, page 54, and
Chapter 8, page 129.
Table 10-1 Summary of GPSCard Differential Corrections Formats
NovAtel Proprietary Format
RTCM Formats
RTCA Formats
ASCII
Tx/Rx
Binary
Tx/Rx
All Binary
Tx/Rx
All Binary
Tx/Rx
DCSA
Tx/Rx
DCSB
Tx/Rx
RTCM(1)
Tx/Rx
RTCA
Tx/Rx
RTCMA
Tx/Rx
RTCMB
Tx
RTCM(2)
Rx
RTCAA
Tx/Rx
RTCAB
Tx/Rx
RTCM(3)
Tx/(Rx)
RTCM(9)
Rx
RTCM(16)
Tx/Rx
RTCM(59)
Tx/(Rx)
see notes
NOTES:
-
Tx = GPSCard capable of transmitting this log.
-
Rx = GPSCard capable of decoding this log.
-
RTCMA and RTCMB differential logs contain RTCM type 1 data formatted in NovAtel ASCII/Binary formats.
-
RTCAA and RTCAB differential logs contain RTCA data formatted into NovAtel ASCII/Binary formats.
-
RTCM(3) and RTCM(59) differential logs can only be received by GPSCards with the RT-20 option.
-
Only GPSCards specially configured for OCXO operation can transmit RTCM(9) data.
-
To utilize differential corrections, the GPSCard must have the “R” option.
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Appendix A
ESTABLISH A DATA LINK
Operating the GPSCard with a DGPS system requires that the reference station broadcast differential correction data
messages to one or more remote receivers. As there are many methods by which this can be achieved, it is left to the
responsibility of the system provider to establish an appropriate data link that best suits the system remote user
requirements.
Whatever data link is chosen, the reference station will want to ensure that the bit rate of data transmission is suitable for
the anticipated data link and remote users. Use the GPSCard COMn command to change the COM port default bit rate
(default is 9600 bps, no parity, 8 data bits, 1 stop bit, no handshake, echo off).
Note that the GPSCard COMn_DTR and COMn_RTS commands are available for remote device keying (such as a radio
transmitter). These commands allow for flexible control of the DTR and RTS lines to be precisely timed with log
transmissions.
INITIALIZATION – REFERENCE STATION
Differential mode of operation is established at the reference station through a two step process: fix position and logging
observation and correction data.
FIX POSITION
The reference station must initialize the precise position of its reference antenna phase centre (lat/lon/hgt). This is
accomplished by utilizing the GPSCard FIX POSITION command. The syntax is as follows:
Syntax:
FIX POSITION
lat
lon
height
station id
health
Example:
fix position 51.3455323,-114.2895345,1201.123,555,0
NOTES:
-
Entry of the station ID and health are optional.
-
The accuracy of the reference station’s fix position setting will directly affect the accuracy of its computed
differential corrections. Good results at the remote station are dependent on the reference station’s combined
position errors being kept to a minimum (e.g., fix position error + multipath errors).
-
The GPSCard performs all computations based on WGS-84 and is defaulted as such, regardless of datum command
setting. The datum in which you choose to operate is converted to and from WGS-84; therefore, all differential
corrections are based on WGS-84. Ensure that any change in your operating datum is set prior to fix position.
-
When transmitting RTCM type data, the GPSCard has various options for assigning the number of data bits per byte.
Please refer to the GPSCard command rtcmrule, page 40, for further information concerning RTCM data bit rule
settings.
-
The fix position “health” field entered will be reported in word 2 of the RTCM message frame header.
Once the GPSCard has its position fixed and is tracking three or more satellites, it is now ready to transmit differential
correction and observation data to the remote stations.
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Appendix A
LOG BROADCAST DATA
Assuming that a data link has been established, use the GPSCard LOG command to send observation and differential
corrections data for broadcast to the remote stations.
Syntax:
LOG
port
data
ontime
seconds
Example:
log com1 dcsb ontime 5
REMINDER: Ensure that the bit rate of the data link is suitable for the differential data type, logging rate and maximum
message length of the data type being logged.
OPTIONS FOR LOGGING DIFFERENTIAL CORRECTIONS
The logging method used for sending differential corrections from the reference station to a remote station will depend on
various factors that the user will weigh for optimal advantage. The GPSCard is capable of sending differential
corrections data types listed in Table 10-1 to its paired remote stations.
The remote station may or may not be a NovAtel GPSCard receiver. The GPSCard, whether it be a PC Series or OEM
Series, is capable of sending logs in various formats to accommodate varying situations and requirements. The following
chapters will give an overview of each type of differential corrections log provided by the GPSCard and its intended
applications.
SET DGPSTIMEOUT
The DGPSTIMEOUT command allows the reference station to set the delay period by which it will inhibit utilization of
new ephemeris data in its differential corrections. This delay ensures that the remote receivers have had sufficient time to
collect updated ephemeris data as well.
A delay of 120 to 300 seconds will typically ensure that the remote stations have collected updated ephemeris. After the
delay period is passed, the reference station will begin using new ephemeris data. To enter an ephemeris delay value, you
must first enter a numeric placeholder in the DGPS delay field (e.g., 2). When operating as a reference station, DGPS
delay will be ignored (refer to the DGPSTIMEOUT command, page 27, for further information on using this command at
remote stations).
Syntax:
DGPSTIMEOUT
Command
DGPSTIMEOUT
dgps delay
ephem delay
Option
min.
max.
min.
max.
2
1000
0
600
dgps delay
ephem delay
Description
Command
Maximum age in seconds
Default
Minimum time delay in seconds
120
60
Example:
dgpstimeout 2,300
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Appendix A
USING THE DCSA DIFFERENTIAL CORRECTIONS LOG
This data type can be logged out any port of the GPSCard reference station and accepted through any port of the
GPSCard remote station without dedicating a port for this purpose. The DCSA data type is directly digestible by any
NovAtel GPSCard Series of receivers and will be recognized as a Special Data Input Command ($DCSA). The remote
receiver accepting this data log must have its ACCEPT command set to “ACCEPT port COMMANDS”.
If you wish to redirect the DCSA log through the host PC COM ports or MODEM, then you will be required to log to the
Console and write your own custom user interface program to properly route the console log to the appropriate
destination port.
USING THE DCSB DIFFERENTIAL CORRECTIONS LOG
The DCSB log transmits differential corrections in NovAtel Binary Format. The DCSB binary format is more efficient
than DCSA because the DCSB format more closely matches the internal data structure of the GPSCard receiver and
requires minimal CPU power to process.
To utilize the DCSB log, the remote station must issue the ACCEPT port DCSB command and dedicate one of the
GPSCard COM ports for receiving the differential data. Once the ACCEPT port DCSB command has been issued, the
designated COM port cannot be used for any other command type input.
If the reference station wishes to redirect the DCSB log through the host PC COM ports or MODEM, then you will be
required to log to the Console and write your own custom user interface program to properly route the console log to the
appropriate destination port.
Remember that even though you may be able to route the DCSB log through your remote station host PC ports, the log
can only be interpreted directly into a GPSCard COM1 or COM2 port in conjunction with the remote station ACCEPT
port DCSB command. If the remote station's customized user interface program requires that the received DCSB data be
sent across the console bus interface, the custom program running the PC will need to convert the DCSB data to DCSA
format and then send them across as $DCSA commands.
NOTE:
-
The DCSA/B log is specific to NovAtel cards and cannot be interpreted by GPS receivers supplied by other
manufacturers.
-
As the checksum of the DCSB log is 1 byte, there is a 1 in 255 possibility that a complete DCSB log will contain an
error.
-
In previous software releases, this log was recommended as the most efficient differential format because the DCSB
format most closely matches the internal data structure of the GPSCard receiver, and requires minimal CPU power to
process. However with the introduction of the RTCA Standard, the RTCA log is now the recommended format for
greatest efficiency combined with data integrity.
USING RTCM SC-104 LOG TYPES
RTCM SC-104 is a standard for transmitting differential corrections between equipment from different manufacturers.
The NovAtel GPSCard is capable of transmitting or receiving RTCM data.
To facilitate transmitting the RTCM data over shared data links, the GPSCard is also capable of sending the RTCM log in
NovAtel ASCII format (RTCMA) or with the NovAtel Binary Header (RTCMB) added to allow synchronous
transmission and reception along with other data types.
REMEMBER: When sending or receiving RTCM log types, it is important to ensure that all connected equipment are
using the same rtcmrule for compatibility.
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Appendix A
The easiest method to send RTCM Standard logs is from the COM1 or COM2 ports of the reference GPSCard. The
easiest method to receive the RTCM data is through the COM1 or COM2 port of the remote GPSCard. The remote
GPSCard must issue the “ACCEPT port RTCM” command to dedicate a port before it will accept the RTCM data input
to that port.
The RTCMA log can be intermixed with other NovAtel ASCII data over a common communications port. It will be
directly interpreted by a remote GPSCard as a Special Data Input Command ($RTCM). “ACCEPT port COMMANDS”
must be used with this input command. A non-NovAtel remote station will need to strip off the header ($RTCM) and
terminator (*xx), then convert the hexadecimal data to binary before the RTCM Standard data can be retrieved.
The RTCMB log can be intermixed with other NovAtel Binary data over a common communications port. A GPSCard
operating as a remote station does not directly interpret this log. To accept this log type, the remote station must first
strip off the 12 byte NovAtel Binary Header before it can be used as an RTCM Standard differential correction.
REMEMBER: Use the CDSA/B logs to monitor the COM port activity, success, and decoding errors.
USING RTCA LOG TYPES
RTCA logs are currently under development and therefore their format is preliminary. The RTCA (Radio Technical
Commission for Aviation Services) Standard is being designed to support Differential Global Navigation Satellite System
(DGNSS) Special Category I (SCAT-I) precision approaches. The perceived advantage to using RTCA type messages
for transmitting and receiving differential corrections versus using RTCM type messages is that RTCM transmits 30-bit
words, and the data is difficult to decode and process because of the parity algorithm used and regular word sizes used.
RTCA is transmitted in 8-bit words, which are easier to generate and process decode. The RTCA messages are therefore
smaller, they have a 24 bit CRC that is much more robust than RTCM messages, and they permit the use of a four-alphacharacter station ID.
RTCA Standard logs can be received through the COM1 or COM2 port of the remote GPSCard. The remote GPSCard
must issue the “ACCEPT port RTCA” command to dedicate a port before it will accept the RTCA data input to that port.
The RTCA logs cannot be intermixed with other logs.
The RTCAA log can be intermixed with other NovAtel ASCII data over a common communications port. It will be
directly interpreted by a remote GPSCard as a Special Data Input Command ($RTCA). “ACCEPT port commands” must
be used with this input command. A non-NovAtel remote station will need to strip off the header ($RTCA) and
terminator (*xx), then convert the hexadecimal data to binary before the RTCA Standard data can be retrieved.
The RTCAB log can be intermixed with other NovAtel binary data. The COM1 or COM2 port of the remote GPSCard
must be dedicated to receiving RTCA data only, and so the “ACCEPT port RTCA” command must be issued. The
remote GPSCard will ignore any data bytes between RTCA messages, including the NovAtel binary log header. The
remote GPSCard identifies the RTCAB log by the message block identifier contained in the message, and will interpret
only the RTCA data portion of the log.
NOTE: The CDSA/B logs may be used to monitor the COM port activity and differential data decode success.
INITIALIZATION – REMOTE STATION
It is necessary to initialize the remote receiver to accept observation data from the reference station. If the receiver is not
correctly initialized, it will proceed to compute solutions in single point positioning mode.
Before initializing, ensure that the data link with the reference station has been properly set up. As well, ensure that the
COM port which is to receive the differential data is set up to match the bit rate and protocol settings of the reference
station broadcast data.
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Appendix A
Establishing differential mode of operation at the remote receiver is primarily a one-step process whereby the ACCEPT
command is used to enable reception of observation data from the reference station.
ACCEPT COMMAND
The ACCEPT command is primarily used to set the GPSCard’s COM port command interpreter for acceptance of various
data formats. For example, if it is set to ACCEPT port COMMANDS, the COM port will accept all valid GPSCard
ASCII format data (including $DCSA, $RTCM, and $RTCA differential corrections data). On the other hand, if it is set
to ACCEPT port DCSB, the GPSCard will only accept the NovAtel format DCSB differential corrections data in
NovAtel binary format. As well, if it is set to accept “RTCM”, the GPSCard command interpreter (for that specified
port) will only accept RTCM types 1, 2, 9 , and 16 RTCM Standard data (RTCM types 3 and 59 will not be utilized
unless ACCEPT is set to “RT20”).
Syntax:
ACCEPT
port
mode
Example:
accept com2 DCSB
Once initialized, the remote GPSCard receiver will operate in single point mode until the differential messages are
received. If the data messages are lost, the GPSCard will revert to single point positioning until the pseudorange
correction messages are restored.
NOTE: Ensure that the GPSCard RTCMRULE settings agree with the bit rule being transmitted by the RTCM reference
station. Unless otherwise set, all GPSCards default to 6CR.
LOG POSITION DATA AND OTHER USEFUL DATA
The GPSCard remote receiver has many options for information data logging. To monitor position status, the user may
find the PRTKA/B logs to be the most informative. Other options exist, such as POSA/B and GPGGA. As well, velocity
data can be found in the VLHA/B, SPHA/B, and GPVTG logs. It is really up to the user’s specific applications as to the
full range of logs required by the user.
Table 10-2 GPSCard Pseudorange Differential Initialization Summary
REFERENCE STATION
REMOTE STATION
Required:
FIX POSITION lat lon hgt id (health)
LOG port DATATYPE ontime 5
Recommended Options:
LOG DATATYPES (binary):
DCSB
RTCMB
RTCAB
RTCM
RTCA
LOG DATATYPES (ascii):
DCSA
RTCMA
RTCAA
Required:
ACCEPT port DATATYPE
146
Recommended Options:
ACCEPT DATATYPES (binary):
DCSB
RTCM
RTCA
ACCEPT COMMANDS (ascii):
DCSA
RTCMA
RTCAA
GPSCard™ Command Descriptions Manual Rev 3
Appendix A
REFERENCE STATION
REMOTE STATION
Related Commands /Logs:
RTCMRULE
DATUM
Related Commands /Logs:
RTCMRULE
DATUM
POSA/B
PRTKA/B
VLHA/B
CDSA/B
GPGGA
Example 1:
Example 1:
fix position 51.3455323 -114.2895345 1201.123 555 0
accept com2 rtcm
log com1 RTCM ontime 2
log com1 posa ontime 1
Example 2:
Example 2:
fix position 51.3455323 -114.2895345 1201.123 555
accept com2 commands
log com2 dcsa ontime 2
log com1 posa ontime 0.2
log com1 vlha ontime 0.2
NOTE: Italicized entries indicate user definable.
Table 10-3 Latency-Induced Extrapolation Error
Time since last reference station observation
0-2 seconds
2-7 seconds
7-30 seconds
GPSCard™ Command Descriptions Manual Rev 3
Typical extrapolation error (CEP)
1 cm/sec
2 cm/sec
5 cm/sec
147
Appendix A
RT-20 CARRIER PHASE MEASUREMENT SYSTEM
11
INTRODUCTION
The GPSCard RT-20 option has been developed to fill niche market needs for relatively low cost, real-time DGPS
receivers capable of nominal positioning accuracies of 10 to 30 cm, while on-the-fly.
RT-20 provides high performance functionality intended for system developers who need the 10 to 30 cm level of
accuracy built into their positioning systems. Allowing for ease of integration, RT-20 is a software option available as an
upgrade to existing 12 channel PC Series and OEM Series GPSCards.
RT-20 OVERVIEW
It was discussed in the previous chapter that pseudorange (C/A code) single differencing techniques are capable of
positioning accuracies of typically one to 5 m CEP, and NovAtel’s 3951R/3151R receivers are capable of pseudorange
single differencing accuracies of 0.75 m (real-time) when used with the GPSAntenna 501 and Choke Ring Ground Plane.
To improve on this level of accuracy performance, more sophisticated ranging measurement techniques are required.
NovAtel’s RT-20 Carrier Phase Measurement System incorporates specialized methods which improves the real-time
positioning performance to < 20 cm CEP nominal accuracy. The GPSCard accomplishes this by using pseudorange and
carrier phase measurements in a double difference algorithm.
By using carrier phase ranging measurements, sub-wavelength accuracies are easily achievable (one wavelength at L1
carrier frequency = 19.01 cm). It has been widely understood that carrier phase measurements in themselves are not
difficult to achieve. However, the problem is in resolving the carrier cycle integer ambiguities (on which cycle are we
measuring the phase?). Post processing packages have been doing this for a long time now – but what about in real-time
static and kinematic modes where < 20 cm position solutions are required? RT-20 accomplishes this task with the use of
its robust floating ambiguity resolution techniques.
To further improve its ranging and positioning confidence, RT-20 combines carrier phase measurements with double
differencing techniques. Double differencing utilizes a combination of observation differences between satellites and
receivers. For baselines less than 10 km, double differencing virtually eliminates all biases (with the exception of
multipath) which includes the between-receiver clock errors that single differencing techniques are incapable of
eliminating. This reduction of errors enables faster, more accurate and reliable carrier phase floating point ambiguity
resolution.
RT-20 FEATURES SUMMARY
RT-20 mode provides the following features list:
148
•
A robust system for applications requiring real-time kinematic accuracies in the 10 to 30 cm range
•
Accuracy improves with longer periods of uninterrupted operation (down to 5 cm CEP)
•
Nominal velocity accuracy of < 2 cm/sec RMS
•
Utilizes double difference positioning techniques acting on GPS L1 carrier phase measurements.
•
On-the-fly floating ambiguity resolution without the need for static initialization
•
Cycle slip detection in the tracking loops
GPSCard™ Command Descriptions Manual Rev 3
Appendix A
•
OEM format resides on a single printed circuit board (Eurocard) for easy OEM integration into your
customized positioning system.
•
Utilizes an optimal data packet formatted as an RTCM message carrying both pseudorange and carrier phase
data for real-time double-difference DGPS operation.
•
Very low position latency (< 70 msec)
•
Automatic motion detection allows improved on-the-fly kinematic specifications for seamless transition
between RT-20 static and kinematic modes.
•
System accuracy performance degrades gracefully as the length of the baseline increases.
•
Very little (< 3 cm) degradation in accuracy for correction delays of up to 2.0 seconds
•
Maintains a high position rate regardless of the differential link rate.
THE RT-20 SYSTEM
RT-20 is essentially a high performance mode of differential operation in which the GPSCard can be set up to operate.
To utilize the benefits of RT-20 mode, the user must have already purchased a GPSCard (or RT-20 software upgrade)
with the RT-20 option enabled.
To operate in RT-20 mode also requires that the GPSCard be operating as part of an “RT-20 system”. The RT-20 system
is comprised of a GPSCard reference station in conjunction with one or more GPSCard RT-20 remote stations. As
well, some form of data link is required such that the GPSCard reference station can transmit differential observation data
to the remote GPSCard stations.
To be fully functional, the RT-20 system requires that the reference station transmit its reference position, as well as
observation data, to the remote receivers. This is accomplished with a data packet utilizing a modified message in the
RTCM Standards data format. More specifically, the data packet is comprised of a minimum of an RTCM Type 3
message followed by an RTCM Type 59 “N” message. (For further information, refer to RTCM3, page 132, and
RTCM59, page 134.) As well, RT-20 mode allows the reference station to transmit RTCM Type 1 messages.
Transmitting Type 1 messages concurrently with Type 59 “N” messages allows the remote receivers to revert to
“pseudorange single differencing mode” (≅ 1 m accuracy level) if the RT-20 filter is unable to generate a position.
OPERATING IN RT-20 MODE
Operating in RT-20 mode requires that the GPSCard reference and GPSCard remote receivers be appropriately
“initialized” and linked by some form of data link (to be supplied by the user). The receivers must be tracking a
minimum of four common satellites before the remote receivers will begin the double difference carrier phase ambiguity
resolution convergence process.
ESTABLISH A DATA LINK
The RT-20 system requires that the GPSCard reference station broadcast RTCM type data messages to one or more
RT-20 remote receivers. As there are many methods by which this can be achieved, it is left to the responsibility of the
system provider to establish an appropriate data link that best suits the system remote user requirements.
Whatever data link is chosen, the reference station will want to ensure that bit rate of data transmission is suitable for the
anticipated data link and remote users. Use the GPSCard COMn command to change the COM port default bit rate
(default is 9600 bps, no parity, 8 data bits, 1 stop bit, no handshake, echo off).
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Appendix A
It is worth noting that the GPSCard COMn_DTR and COMn_RTS commands are available for remote device keying
(such as a radio transmitter). These commands allow for flexible control of the DTR and RTS lines to be precisely timed
with log transmissions.
INITIALIZATION – REFERENCE STATION
RT-20 mode of operation is established at the reference station through a two step process: fixing position and logging
observation and correction data.
FIX POSITION
The reference station must initialize the precise position of its reference antenna phase centre (lat/lon/hgt). This is
accomplished by utilizing the GPSCard FIX POSITION command. The syntax is as follows:
Syntax:
FIX POSITION
lat
lon
height
station id
health
Example:
fix position 51.3455323,-114.2895345,1201.123,555,1
NOTES:
-
Entry of the station ID and health are optional.
-
The accuracy of the reference station’s fix position setting will directly affect the accuracy of its computed
differential corrections. Good results at the remote station are dependent on the reference station’s combined
position errors being kept to a minimum (e.g., fix position error + multipath errors).
-
The GPSCard performs all computations based on wgs-84 and is defaulted as such, regardless of datum command
setting. The datum in which you choose to operate is converted to and from wgs-84. Therefore all differential
corrections are based on that datum. Ensure that any change in your operating datum is set prior to fix position.
-
When transmitting RTCM type data, the GPSCard has various options for assigning the number of data bits per byte.
Please refer to the GPSCard command rtcmrule, page 40, for further information concerning RTCM data bit rule
settings.
-
The fix position “health” field entered will be reported in word 2 of the RTCM message frame header.
LOG BROADCAST DATA
Once a data link has been established, use the GPSCard “LOG” command to send observation and differential corrections
data for broadcast to the remote stations. There are two required logs and one optional log. The two logs required for
RT-20 data broadcast are “RTCM3” and “RTCM59”, whereas the optional log is “RTCM”.
The RTCM3 data log reports the precise position of the reference station antenna as previously entered into the fix
position command. Remote RT-20 receivers require this data message to establish the reference station’s reference
position before precise positioning computations can begin.
The RTCM59 data log is used to broadcast the reference station’s satellite observation data to the RT-20 remote stations.
This observation data contains the pseudorange and carrier phase for up to 12 satellites. The remote RT-20 receiver will
require this data for performing the carrier phase double difference computations and the floating ambiguity resolution.
(For further information about these data formats, refer to RTCM3, page 132, and RTCM59, page 134.)
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The RT-20 reference station may also broadcast the optional differential correction log “RTCM”. This contains RTCM
type 1 message data and may be used by the RT-20 remote receivers to quickly achieve 1 m position accuracy at start-up
or during other periods when the RT-20 remote is unable to generate a position.
Syntax:
LOG
port
data
ontime
seconds
Example:
log com2 rtcm3 ontime 10
log com2 rtcm59 ontime 2
log com2 rtcm ontime 5
NOTE: When transmitting RTCM type data, the GPSCard has various options for assigning the number of data bits per
byte. Please refer to the GPSCard command rtcmrule, page 40, for further information concerning RTCM data bit rule
settings. Unless otherwise set, the GPSCard default is 6cr (6 bits valid data per byte followed by <cr>).
REMINDER: Ensure that the bit rate of the data link is suitable for the logging rate and maximum message length of
the RTCM data being logged. Refer to Table 11-2, page 155, or Chapter 8, page 129, for details on RTCM message
lengths.
INITIALIZATION – REMOTE STATION
It is necessary to initialize the RT-20 remote receiver to accept observation data from the reference station. If the RT-20
receiver is not correctly initialized, it will proceed to compute solutions in single point positioning mode.
Before initializing for RT-20 mode, ensure that the data link with the reference station has been properly set up. As well,
ensure that the COM port which is to receive the RTCM type data is set up to match the bit rate and protocol settings of
the reference station broadcast data.
Establishing RT-20 mode of operation at the remote receiver is primarily a one-step process whereby the ACCEPT
command is used to enable reception of observation data from the reference station.
ACCEPT COMMAND
The ACCEPT command is primarily used to set the GPSCard’s COM port command interpreter for acceptance of various
data formats. For example, if it is set to accept “COMMANDS”, the COM port will accept all valid GPSCard ASCII
format data (including $DCSA, $RTCA, and $RTCM differential corrections data). On the other hand, if it is set to
accept “DCSB”, the GPSCard will only accept the NovAtel format DCSB differential corrections data in NovAtel binary
format. As well, if it is set to accept “RTCM”, the GPSCard command interpreter (for that specified port) will only
accept RTCM types 1, 2, 9, and 16 RTCM standard data (RTCM types 3 and 59 will not be utilized). To operate in RT20 mode as a real-time double differencing carrier phase measurement system, the ACCEPT command must be set to
accept “RT20”.
Syntax:
ACCEPT
port
mode
Example:
accept com2 rt20
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Appendix A
Once initialized, the remote RT-20 receiver will operate in single point mode until sufficient RT20 messages are
received. If RTCM type 1 messages are concurrently being received as well, the receiver will immediately operate in
single differencing pseudorange differential mode. Once sufficient RT20 messages are received, the GPSCard will begin
the carrier phase double differencing convergence process. If an interruption in RT20 messages occurs, the GPSCard will
utilize the concurrently received RTCM type 1 messages to maintain pseudorange differential accuracies. If the RTCM
type 1 messages are not available, the GPSCard will revert to single point positions until the RT20 messages are restored.
NOTES:
-
Each time rt20 mode reverts to single point or single differencing mode and then back to rt20 mode, the GPSCard
will automatically perform an rt20 reset, which recommences the convergence process. (Convergence begins at the
1 m level and converges to < 20 cm in 3 - 5 minutes after reset occurs. See Table 11-3, page 156, for RT-20
convergence summary.)
-
Ensure that the GPSCard rtcmrule settings agree with the bit rule being transmitted by the reference station. Unless
otherwise set, all GPSCards default to 6cr.
-
When accept is set to “accept port rt20”, the GPSCard will also accept RTCM Type 1 corrections.
LOG POSITION DATA
RT-20 mode of operation utilizes two dedicated position data logs: RTKA/B and PRTKA/B. PRTKA/B log provides a
best computed position available during RT-20 mode operation. RTKA/B logs will provide position solutions that have
been computed from time matched reference and remote station observations. Refer to Chapter 5, RTKA/B, page 100,
and PRTKA/B, page 83, for more specific information about these logs. (The POSA log, page 82, also contains the RT20 position data, but is not as detailed.)
Table 11-1 RT-20 System Initialization Summary
RT-20 Reference Station
Required:
FIX POSITION lat lon hgt (id) (health)
LOG port rtcm3 ontime 10
LOG port rtcm59 ontime 2
Recommended Option:
LOG port rtcm ontime 5
Related Commands / Logs:
RTCMRULE
DATUM
RT-20 Remote Station
Required:
ACCEPT port RT20
LOG port PRTKA period interval
Recommended Option:
LOG port RTKA onchanged
Related Commands / Logs:
RESETRT20
RTCMRULE
DATUM
VLHA/B
CDSA/B
NOTE: Italicized entries indicate user definable.
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RT-20 PERFORMANCE
STEADY STATE
The RT-20 system provides nominal 20 cm accuracy (CEP) after 3 minutes of continuous lock in static mode. After an
additional period of continuous tracking (from 10 to 20 minutes), the system reaches steady state and position accuracies
in the order of 3 to 4 cm are typical. The time to steady state is about 3 times longer in kinematic mode.
Figure 11-1 shows the performance of the RT-20 system running with RTCM59 corrections received at a 1/2 Hz rate.
The system by this time is in steady state and the position errors are well represented by the standard deviations shown in
the position display.
Figure 11-1 Illustration of RT-20 Steady State Performance
PERFORMANCE DEGRADATION
The performance will degrade if satellites are lost at the remote or if breaks occur in the differential correction
transmission link. The degradations related to these situations are described in the following paragraphs.
Provided lock is maintained on at least 4 SVs and steady state has been achieved, the only degradation will be the result
of a decrease in the geometrical strength of the observed satellite constellation. If steady state has not been achieved,
then the length of time to ambiguity resolution under only 4-satellite coverage will be increased significantly.
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Appendix A
REMOTE TRACKING LOSS
If less than 4 satellites are maintained, then the RT-20 filter will be reset and all ambiguity information for all satellites
(tracked or not) will be lost. When this occurs, the POSA/B and P20A/B logs will be generated with differential (if
RTCM Type 1 messages are transmitted with the Type 59 messages) or single point pseudorange solutions. When the
satellites are reacquired, the RT-20 initialization process described below occurs (see Figure 11-2, page 154).
DIFFERENTIAL LINK BREAKDOWN
1.
Provided the system is in steady state, and the loss of observation data is for less than 30 seconds, the RT-20
positions will degrade according to the divergence of the reference observation extrapolation filters. This causes a
decrease in accuracy of about an order of magnitude per 10 seconds without a reference observation, and this
degradation is reflected in the standard deviations of the POSA/B and P20A/B logs. Once the data link has been reestablished, the accuracy will return to normal after several samples have been received.
2.
If the loss of differential corrections lasts longer than 30 seconds, the RT-20 filter is reset and all ambiguity and
reference model information is lost. The timeout threshold for RT-20 differential corrections is 30 seconds, but for
Type 1 pseudorange corrections, the timeout is 60 seconds. Therefore, when the RT-20 can no longer function
because of this timeout, the pseudorange filter can produce differential positions for an additional 30 seconds
(provided RTCM Type 1 messages were transmitted along with the Type 59 messages) before the system reverts to
single point positioning. Furthermore, once the link is re-established, the pseudorange filter produces an immediate
differential position while the RT-20 filter takes an additional 14 seconds to generate its positions. The reference
models require 7 reference observations before they are declared useable, and this will take 14 seconds, based on a
1/2 Hz differential correction rate. The reference model must be healthy before solutions are logged to the POSA/B
and P20A/B logs, so there is a delay in the use of real time carrier positioning to the user once the link has been reestablished. The RT20A/B log uses matched observations only (no extrapolated observations), and these will be
available after three reference observations are received, but will have about 1.5 seconds latency associated with
them.
Figure 11-2 RT-20 Re-initialization Process
REFERENCE
REMOTE
14 sec
RTCM59 messages
required following
RESETRT20
1
2
Monitor
Doppler
MONITOR
REFERENCE
REMOTE
RTCM59 messages
required fol owing 1
RESETRT20
2
3
4
5
6
7
REMOTE
Monitor
Doppler
154
Start generating monitor
phase models and RT20A/B logs
Models
ready
sec
Generate RT20A/B
and P20A/B ;pgs
RTCM59 messages
required following
RESETRT20
1
2
Monitor
Doppler
3
4
5
Start generating monitor
phase models and
RT20A/B logs
6
Models
ready14
7
Generate RT20A/B
and
P20A/B logs
3
4
5
Start generating monitor
phase models and
RT20A/B logs
6
Models
ready
7
Generate RT20A/B
and
P20A/B logs
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Appendix A
The RT-20 system is based on a time-matched double difference observation filter. This means that observations at the
remote site have to be buffered while the reference observation is encoded, transmitted, and decoded. Only two seconds
of remote observations are saved, so the reference observation transmission process has to take less than 2 seconds if any
time matches are to be made. In addition, only remote observations on even second boundaries are retained, so reference
observations must also be sent on even seconds if time matches are to be made.
NOTES ON THE USE OF RT-20
-
Note that the RT-20 processing in a remote receiver is specifically linked to corrections from a particular GPSCard
reference station. Switching to a new GPSCard reference station will cause the algorithm to reset and start over
again.
-
For users on longer baselines (> 10 km), performance can be improved by downloading a recently stored almanac
and ionospheric information into the receiver before starting operation. (12 channel OEM cards can save almanac in
flash.)
-
Although not essential, even very short periods of sitting still (1 to 3 minutes) during the convergence process can
reduce the time to steady state dramatically.
-
The following commands will have no effect on RT-20 positioning:
•
•
•
•
•
ECUTOFF
FIX HEIGHT
LOCKOUT
SETHEALTH
RESETHEALTH
Table 11-2 RT-20 Performance Specifications
Item
Operating Frequency:
Channels:
Time To First Fix:
Reacquisition:
Range Measurements:
RT-20 Mode Resolution Time:
RT-20 mode Position Accuracy:
Pseudorange Differential Accuracy:
Single Point Positioning Accuracy:
Position Latency:
Velocity Accuracy:
RT-20 Data Packet:
Position Logging Rate:
Specification
1575.42 MHz (L1)
12 (or 10, depending on GPSCard model option)
< 70 seconds typical
3 seconds typical
C/A code pseudorange and carrier phase double differencing techniques
3 to 5 minutes typical (static)
0.20 m CEP1 (also see Table 11-3, page 156)
0.75 m CEP
40 m CEP (SA on)
≅ 70 msec (independent of data link)
< 2 cm/sec (nominal)
RTCM3 (180 data bits maximum)
RTCM59 “N” (up to 990 data bits maximum)
RTCM type 1 message (optional)
Check with dealer for maximum rate
NOTES:
-
Nominal accuracy after 3 minutes static or 10 minutes kinematic minimum. Kinematic resolution with continuous
good satellite coverage (6 SVs).
-
RT-20 double difference accuracies are based on PDOP < 2 and continuous tracking of a minimum 5 satellites
(6 preferred) and elevations > 15•.
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Appendix A
PERFORMANCE SUMMARY – TABLES AND FIGURES
Table 11-3 RT-20 Convergence Summary
Tracking Time (sec)
1 to 180
180 to 3000
3000 or more
S/K*
S
S
S
1 to 600
600 to 3000
3000 or more
Data Delay (sec)
0
0
0
Distance (km)
1
1
1
K
K
K
S/K
S/K
S/K
S/K
0
0
0
0 to 2
2 to 7
7 to 30
30 to 60
1
1
1
1
1
1
1
S/K
S/K
S/K
S/K
60 or more
0
0
0
1
0 to 10
10 to 20
20 to 50
Accuracy (cm) (CEP)
100 to 25
25 to 5
5 or less 1
100 to 25
25 to 5
5 or less
+1 per sec
+2 per sec
+5 per sec
+7 per sec 2
Single Point
+0.5 per km
+0.75 per km
+1.0 per km
* K = Kinematic (during initial ambiguity resolution)
S = Static (during initial ambiguity resolution)
1 The accuracy specifications refer to the P20A/B logs, page 78, which include about 3 cm extrapolation error. RT20A/B logs, page 98, are more accurate but have more latency associated with
them.
2 Between 30 and 60 seconds assumes pseudorange differential positioning. If Type 1 corrections have not been transmitted, the accuracy drops to single point mode after 30 seconds.
Figure 11-3 CEP Accuracy Over Cumulative Tracking Time
120
100
Horizontal CEP (cm)
Static
80
Kinematic
60
40
20
0
0
10
20
30
40
50
Resolution Time (Minutes)
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Appendix A
Figure 11-4 CEP Accuracy Degradation with Increasing Baseline
45
40
CEP baseline factor (cm)
35
30
25
20
15
10
5
0
0
10
20
30
40
50
60
Baseline length (km)
Figure 11-5 Typical Example of Static Resolution Performance
Jan 27/94
(reset RT-20 every 200 seconds)
Static Resolution Performance Jan 27/94
0.9
0.8
0.7
0.6
0.5
Horizontal Error (metres)
0.4
0.3
0.2
0.1
0
347066
347266
347466
347666
347866
348066
348266
348466
348666
348866
GPS Time of Week
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Appendix A
12
MULTIPATH ELIMINATION TECHNOLOGY
Multipath signal reception is one of the most plaguing problems that detracts from the accuracy potential of GPS
pseudorange differential positioning systems. This chapter will provide a brief look at the problems of multipath
reception and some solutions developed by NovAtel.
MULTIPATH
Multipath occurs when an RF signal arrives at the receiving antenna from more than one propagation route (multiple
propagation paths – thus multipath).
Figure 12-1 Illustration of GPS Signal Multipath
Water
Body
WHY DOES MULTIPATH OCCUR?
When the GPS signal is emitted from the satellite antenna, the RF signal propagates away from the antenna in many
directions. Because the RF signal is emitted in many directions simultaneously and is traveling different paths, these
signals encounter various and differing natural and man-made objects along the various propagation routes. Whenever a
change in medium is encountered, the signal is either absorbed, attenuated, refracted, or reflected.
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Refraction and reflection cause the signals to change direction of propagation. This change in path directions often
results in a convergence of the direct path signal with one or more of the reflected signals. When the receiving antenna is
the point of convergence for these multipath signals, the consequences are generally not favorable.
Whenever the signal is refracted, some signal polarity shifting takes place; and when full reflection occurs, full polarity
reversal results in the propagating wave. The consequences of signal polarity shifting and reversal at the receiving
antenna vary from minor to significant. As well, refracted and reflected signals generally sustain some degree of signal
amplitude attenuation.
It is generally understood that, in multipath conditions, both the direct and reflected signals are present at the antenna and
the multipath signals are lower in amplitude than the direct signal. However, in some situations, the direct signal may be
obstructed or greatly attenuated to a level well below that of the received multipath signal. Obstruction of direct path
signals is very common in city environments where many tall buildings block the line of sight to the satellites. As
buildings generally contain an abundance of metallic materials, GPS signal reflections are abundant (if not
overwhelming) in these settings. Obstructions of direct path signals can occur in wilderness settings as well. If the GPS
receiver is in a valley with nearby hills, mountains and heavy vegetation, signal obstruction and attenuation are also very
common.
CONSEQUENCES OF MULTIPATH RECEPTION
Because GPS is a radio ranging and positioning system, it is imperative that ground station signal reception from each
satellite be of direct line of sight. This is critical to the accuracy of the ranging measurements. Obviously, anything other
than direct line of sight reception will skew and bias the range measurements and thus the positioning triangulation (or
more correctly, trilateration). Unfortunately, multipath is almost always present to some degree, due to real world
conditions.
When a GPS multipath signal converges at the GPS antenna, there are two primary problems that occur:
1.
a multiple signal with amplitude and phase shifting, and
2.
a multiple signal with differing ranges.
When the GPS antenna intercepts a direct signal and multipath signal, the two signals will sum according to the phase and
amplitude of each. This summation of signals causes the composite to vary greatly in amplitude, depending on the degree
of phase shift between the direct signal versus the multipath signal. If the multipath signal lags the direct path signal by
less than 90º, the composite signal will increase in amplitude (relative to the direct signal, depending on the degree of
phase shift between 0º and 90º). As well, if the multipath signal lags the direct path signal by greater than 90º, but less
than 270º, the composite signal will decrease in amplitude. Depending on the relative amplitude of the multipath signal
(or signals), the composite signal being processed by the receiver correlator may experience substantial amplitude
variations, which can play havoc with the receiver’s automatic gain control circuitry (AGC) as it struggles to maintain
constant signal levels for the receiver correlator. A worst case scenario is when the multipath signal experiences a lag of
180º and is near the same strength as the direct path signal – this will cause the multipath signal to almost completely
cancel out the direct path signal, resulting in loss of satellite phase lock or even code lock.
Because a multipath signal travels a greater distance to arrive at the GPS antenna, the two C/A code correlations are, by
varying degrees, displaced in time, which in turn causes distortion in the correlation peak and thus ambiguity errors in the
pseudorange (and carrier phase, if applicable) measurements.
As mentioned in previous paragraphs, it is possible that the received multipath signal has greater amplitude than the direct
path signal. In such a situation the multipath signal becomes the dominant signal and receiver pseudorange errors become
significant due to dominant multipath biases and may exceed 150 m. For single point pseudorange positioning, these
occasional levels of error may be tolerable, as the accuracy expectations are at the 40 m CEP level (using standard
correlator). However, for pseudorange single differencing DGPS users, the accuracy expectations are at the 1 - 5 m CEP
level (with no multipath). Obviously, multipath biases now become a major consideration in trying to achieve the best
possible pseudorange measurements and position accuracy.
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Appendix A
If a differential reference station is subject to significant multipath conditions, this in turn will bias the range corrections
transmitted to the differential remote receiver. And in turn, if the remote receiver also experiences a high level of
multipath, the remote receiver position solutions will be significantly biased by multipath from both stations. Thus, when
the best possible position solutions are required, multipath is certainly a phenomenon that requires serious consideration.
SOME HARDWARE SOLUTIONS FOR MULTIPATH REDUCTION
A few options exist by which GPS users may reduce the level of multipath reception. Among these include: antenna site
selection, special antenna design, and ground plane options.
ANTENNA SITE SELECTION
Multipath reception is basically a condition caused by environmental circumstances. Some of these conditions you may
have a choice about and some you may not.
Many GPS reception problems can be reduced, to some degree, by careful antenna site selection. Of primary importance
is to place the antenna so that unobstructed line-of-sight reception is possible from horizon to horizon and at all bearings
and elevation angles from the antenna. This is, of course, the ideal situation, which may not be possible under actual
operating conditions.
Try to place the antenna as far as possible from obvious reflective objects, especially reflective objects that are above the
antenna’s radiation pattern horizon. Close-in reflections will be stronger, and typically have a shorter propagation delay
allowing for autocorrelation of signals with a propagation delay of less than one C/A code chip (300 m).
Figure 12-2 Illustration of GPS Signal Multipath vs. Increased Antenna Height
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Appendix A
When the antenna is in an environment with obstructions and reflective surfaces in the vicinity, it is advantageous to
mount the antenna as high as possible to reduce the obstructions, as well as reception from reflective surfaces, as much as
possible.
Water bodies are extremely good reflectors of GPS signals. Because of the short wavelengths at GPS frequencies, even
small ponds and water puddles can be a strong source of multipath reception, especially for low angle satellites. Thus, it
can be concluded that water bodies such as lakes and oceans are among the most troublesome multipath environments for
low angle signal reception. Obviously, water body reflections are a constant problem for ocean going vessels.
ANTENNA DESIGNS
Low angle reflections, such as from water bodies, can be reduced by careful selection of antenna design. For example,
flat plate microstrip patch antennas have relatively poor reception properties at low elevation angles near their radiation
pattern horizon.
Quadrifilar helix antennas and other similar vertically high profile antennas tend to have high radiation gain patterns at
the horizon. These antennas, in general, are more susceptible to the problems resulting from low angle multipath
reception. So, for marine vessels, this type of antenna encourages multipath reception. However, the advantages of good
low angle reception also means that satellites can be acquired more easily while rising in the horizon. As well, vessels
subject to pitch and roll conditions will experience fewer occurrences of satellite loss of lock.
Figure 12-3 Illustration of Quadrifilar vs. Microstrip Patch Antennae
Quadrifilar Elements
Radom
Antenna
Dielectri
Patch Ground
Quadrifilar Helix Antenna
Microstrip Patch Antenna
A good antenna design will also incorporate some form of left hand circular polarization (LHCP) rejection. Multipath
signals change polarization during the refraction and reflection process. This means that generally, multipath signals may
be LHCP oriented. This property can be used to advantage by GPS antenna designers. If a GPS antenna is well designed
for RHCP polarization, then LHCP multipath signals will automatically be attenuated somewhat during the induction into
the antenna. To further enhance performance, antennas can be designed to increase the rejection of LHCP signals.
NovAtel’s GPSAntenna model 501 is an example of an antenna optimized to further reject LHCP signals by more than 10
dB.
GPSCard™ Command Descriptions Manual Rev 3
161
Appendix A
ANTENNA GROUND PLANES
Nearby objects can influence the radiation pattern of an antenna. Thus, one of the roles of the antenna ground plane is to
create a stabilizing artificial environment on which the antenna rests and which becomes a part of the antenna structure
and its resultant radiation pattern.
A small ground plane (relative to one wavelength at the operating frequency) may have minimal stabilizing effect,
whereas a large ground plane (multiple wavelengths in size) will have a highly stabilizing effect.
Large ground planes also exhibit a shielding effect against RF signal reflections originating below the antenna’s radiation
pattern horizon. This can be a very effective low angle shield when the antenna is elevated on a hill or other structure
above other reflecting surfaces such as vehicles, railway tracks, soil with high moisture content, water bodies, etc.
One of the drawbacks of a “flat plate” ground plane is that they do provide an above horizon reflective surface for low
angle GPS signals. This means that the flat plate is also a multipath generating surface. For pseudorange code
measurements, these multipath signals are too close to cause any significant range errors. However, for carrier phase
measurements, the flat plate can cause significant biases. Even if carrier phase is not being used for range measurements,
the flat plate reflections could be substantial enough to cause signal fades and drop-outs due to carrier phase reversals
from the flat plate reflections (keeping in mind that these problems are most substantial for low angle signals). It should
also be kept in mind that low profile antennas such as the patch antenna will obviously be less susceptible to this
phenomenon than higher profile quadrifilar and bifilar helix antennas.
The most effective type of multipath reduction ground plane structure is the “choke ring” ground plane. Due to its
surface cavity construction, surface reflections are essentially trapped, thus minimizing the problems encountered by flat
plate ground planes. This is what makes NovAtel’s GPSAntenna model 501 so successful when used with the NovAtel
GPSAntenna Choke Ring Ground Plane.
Figure 12-4 Example of GPSAntenna on a Flat Plate vs. Choke Ring Ground Plane
Flat plate
Choke Ring
NOVATEL’S INTERNAL RECEIVER SOLUTIONS FOR MULTIPATH REDUCTION
The multipath antenna hardware solutions described in the previous paragraphs are capable of achieving varying degrees
of multipath reception reduction. These options, however, require specific conscious efforts on the part of the GPS user.
In many situations, especially kinematic, few (if any) of the above solutions may be effective or even possible to
incorporate. By far, the best solutions are those which require little or no special efforts in the field on the part of the
GPS user. This is what makes NovAtel’s internal receiver solutions so desirable and practical.
NovAtel has placed long term concerted effort into the development of internal receiver solutions and techniques that
achieve multipath reduction, all of which are transparent to the GPSCard user. These achievements have led to three
patented technologies:
•
•
162
Narrow Correlator Technology
MET Technology
GPSCard™ Command Descriptions Manual Rev 3
Appendix A
•
MEDLL Technology
Each of the above listed solutions utilizes innovative patented correlator delay lock loop (DLL) techniques. As it is
beyond the scope of this manual to describe in detail how the correlator techniques achieve the various levels of
performance, the following paragraphs will provide highlights of the advantages of each technology.
NARROW CORRELATOR TECHNOLOGY
NovAtel’s Performance Series of GPSCard receivers (900/3900/2100/3100 Series) achieve a higher level of pseudorange
positioning “performance” vs. standard (wide) correlator, by virtue of its celebrated Narrow Correlator technology. By
utilizing Narrow Correlator techniques, the GPSCard Performance Series is capable of pseudorange measurement
improvements better than 2:1 when compared to standard correlation techniques. As well, the Narrow Correlator
inherently reduces multipath reception (approaching a factor of eight compared to standard correlator) by virtue of its
narrower autocorrelation function.
Figure 12-5 illustrates relative multipath-induced tracking errors encountered by standard correlators vs. NovAtel’s
Narrow Correlator. As can be seen, standard correlators are susceptible to substantial multipath biases for C/A code chip
delays of up to 1.5 chip, with the most significant C/A code multipath bias errors occurring at about 0.25 and 0.75 chip
(approaching 80 m error). On the other hand, the Narrow Correlator multipath susceptibility peaks at about 0.2 chip
(about 10 m error) and remains relatively constant out to 0.95 chip, where it rapidly declines to negligible errors after 1.1
chip.
Figure 12-5 Comparison of Multipath Error Envelopes
GPSCard™ Command Descriptions Manual Rev 3
163
Appendix A
While positioning in single point mode, the multipath and ranging improvement benefits of a Narrow Correlator receiver
vs. standard correlator are overridden by a multitude of GPS system biases and errors (with or without an antenna choke
ring ground plane). In either case, positioning accuracy will be in the order of 40 m CEP (SA on, no multipath).
However, the benefits of the Narrow Correlator become most significant during pseudorange DGPS operation, where the
GPS systematic biases are largely cancelled.
Receivers operating DGPS with standard correlator technology typically achieve positioning accuracies in the 2 - 5 m
CEP range (low multipath environment and using choke ring ground plane), while NovAtel’s Narrow Correlator receivers
are able to achieve positioning accuracies in the order of 0.75 m CEP (low multipath environment and using choke ring
ground plane). The Narrow Correlator achieves this higher accuracy through a combination of lower noise ranging
measurements combined with its improved multipath resistance when compared to the standard correlator.
MET TECHNOLOGY
It has been recognized that the use of a choke ring ground plane is highly effective in reducing reception of low angle
multipath signals. However, installation and usage of the choke ring is not always practical (or desirable) for many types
of installations, such as on aircraft and other high dynamics vehicles. To help alleviate the necessity of a choke ring
ground plane, NovAtel has developed a new technology called MET – Multipath Elimination Technology. MET is
currently available as a software upgrade to existing non-MET Performance Series GPSCard receivers.
MET is a further enhancement of NovAtel’s GPSCard Narrow Correlator technology. By means of software
manipulation, MET is able to model the direct path signal’s shape and slope, and thus model out the pseudorange
multipath correlation distortions. By reducing the correlation distortions, there is less noise and ambiguity about the
correlation peak, and thus greater confidence in the resultant ranging measurements.
Refer to Figure 12-5, page 163, for a comparative illustration of pseudorange multipath error envelopes. As can be seen
in the figure, MET provides significant reductions in multipath-induced tracking errors for C/A code delays greater than
0.15 chip. As well, MET virtually rejects all multipath delays greater than 1.15 chip, whereas standard correlators are
susceptible up to 1.50 chip.
In practice, a GPSCard utilizing the MET option can typically achieve pseudorange multipath error reductions of up to
30% (relative to NovAtel’s Narrow Correlator) without the use of the GPSAntenna Choke Ring Ground Plane. This can
be of real benefit to high dynamic installations where a choke ring ground plane is not practical to install. As well,
because choke ring ground planes primarily reduce low angle multipath, MET’s 30% reduction applies to multipath
signals arriving from any propagation angle, which includes higher angles where choke ring and flat plate ground planes
are less effective.
When used in combination with the choke ring ground plane, MET will typically provide up to 50% pseudorange
multipath elimination. This 50% multipath error reduction will provide significant position confidence improvements
when used at both the DGPS reference and remote differential stations. It should be noted that MET has no influence
over carrier phase multipath biases.
Using a GPSCard with the MET option installed is exactly the same as non-MET GPSCard operation. This means that
MET functions in the background without any operator intervention, while providing the user with enhanced
performance.
MEDLL TECHNOLOGY
NovAtel has developed a multipath elimination technology that approaches the theoretical limits of multipath-free GPS
signal reception. This new patented technology, called “Multipath Estimation Delay-Lock-Loop” (MEDLL), utilizes a
combination of hardware and software techniques that are capable of reducing the combined effects of pseudorange and
carrier-phase multipath errors by as much as 90% compared to a system using a narrow correlator. As well, MEDLL
does all this without the need to mount the antenna on a choke ring ground plane.
164
GPSCard™ Command Descriptions Manual Rev 3
Appendix A
The MEDLL technology takes further advantage of NovAtel’s parallel channel Narrow Correlator sampling techniques,
and goes far beyond the capabilities of MET. While utilizing a proprietary complex correlator sampling technique
combined with “maximum likelihood estimation” techniques, MEDLL is able to deconvolve the received signals into
their direct path and multipath components by determining the amplitude, delay, and phase angle of each of the composite
signals. Once the composite signal has been broken down into its components, the signal with the least delay is
determined to be the direct signal, and all other signals with greater delay are considered to be the multipath components
(assuming that the direct path signal is available and unobstructed).
To do this, however, MEDLL utilizes a multicard hardware configuration which is housed in a standard 3U high by 28
HP wide “plug-in unit”, designed for quick mounting into a standard 3U by 19” cabinet sub-rack. As well, optional
packaging configurations are available. In addition to this configuration, MEDLL is available with, or without, an
external OCXO oscillator to enhance its higher performance capabilities.
MEDLL can effectively remove all multipath signals that have a propagation delay of greater than 0.1 chip, relative to the
direct path signal. The remaining multipath effect on the C/A code pseudorange measurements is now in the order of
magnitude as a “P” code GPS receiver (without the use of a choke ring ground plane). Refer to Figure 12-5, page 163,
for a comparative illustration of multipath error envelopes for MEDLL, MET, Narrow Correlator, vs. standard
correlators.
SUMMARY
Any localized propagation delays or multipath signal reception cause biases to the GPS ranging measurements that cannot
be differenced by traditional DGPS single or double differencing techniques. Generally speaking, single point
positioning systems are not too concerned with multipath reception, as the system errors are quite large to begin with.
However, multipath is recognized as the greatest source of errors encountered by a system operating in differential mode.
It has been discussed that careful site selection and good antenna design combined with a choke ring ground plane are
fairly effective means of reducing multipath reception.
Internal receiver solutions for multipath elimination are achieved through various types of correlation techniques, where
the “standard correlator” is the reference by which all other techniques can be compared.
The Narrow Correlator has a two fold advantage over standard correlators: improved ranging measurements due to a
sharper, less noisy correlation peak, and reduced susceptibility to multipath due to rejection of C/A code delays of greater
than 1.0 chip. When used with a choke ring ground plane, the Narrow Correlator provides substantial performance gains
over standard correlator receivers operating in differential mode.
The MET option incorporates further enhancements to the Narrow Correlator technique, and with the aid of software
modeling, can provide multipath elimination of up to 30% without a choke ring ground plane, and as much as 50% when
used with a choke ring ground plane (when compared to Narrow Correlation performance).
MEDLL is a very high performance pseudorange C/A code ranging system capable of reducing multipath bias errors by
as much as 90% as compared to the Narrow Correlator – without the aid of a choke ring ground plane. Utilizing a
combination of hardware and software techniques, MEDLL consists of a multicard configuration suitable for mounting in
a standard 19” sub-rack (other configurations available).
GPSCard™ Command Descriptions Manual Rev 3
165
Appendix A
A
GEODETIC DATUMS
The following tables contain the internal ellipsoid parameters and transformation parameters used in the GPSCard. The
values contained in these tables were derived from the following DMA technical reports:
1.
TR 8350.2
Department of Defense World Geodetic System 1984 – Its Definition and Relationships with
Local Geodetic Systems - Revised March 1, 1988.
2.
TR 8350.2B
Supplement to Department of Defense World Geodetic System 1984 Technical Report - Part
II - Parameters, Formulas, and Graphics for the Practical Application of WGS-84 - December
1, 1987.
Table A-1 Reference Ellipsoid Constants
ELLIPSOID
Airy 1830
Modified Airy
Australian National
Bessel 1841
Clarke 1866
Clarke 1880
Everest (India 1830)
Everest (Brunei & E.Malaysia)
Everest (W.Malaysia & Singapore)
Geodetic Reference System 1980
Helmert 1906
Hough 1960
International 1924
South American 1969
World Geodetic System 1972
World Geodetic System 1984
ID CODE
AW
AM
AN
BR
CC
CD
EA
EB
ED
RF
HE
HO
IN
SA
WD
WE
a (metres)
6377563.396
6377340.189
6378160.0
6377397.155
6378206.4
6378249.145
6377276.345
6377298.556
6377304.063
6378137.0
6378200.0
6378270.0
6378388.0
6378160.0
6378135.0
6378137.0
1/f
299.3249647
299.3249647
298.25
299.1528128
294.9786982
293.465
300.8017
300.8017
300.8017
298.257222101
298.30
297.00
297.00
298.25
298.26
298.257223563
f
0.00334085064038
0.00334085064038
0.00335289186924
0.00334277318217
0.00339007530409
0.00340756137870
0.00332444929666
0.00332444929666
0.00332444929666
0.00335281068118
0.00335232986926
0.00336700336700
0.00336700336700
0.00335289186924
0.00335277945417
0.00335281066475
Table A-2 Transformation Parameters (Local Geodetic to WGS-84)
GPSCard Datum
ID number
1
2
3
4
5
6
7
8
9
10
11
166
NAME
DX
DY
ADIND
ARC50
ARC60
AGD66
AGD84
BUKIT
ASTRO
CHATM
CARTH
CAPE
DJAKA
-162
-143
-160
-133
-134
-384
-104
175
-263
-136
-377
-12
-90
-8
-48
-48
664
-129
-38
6
-108
681
DZ
206
-294
-300
148
149
-48
239
113
431
-292
-50
DATUM DESCRIPTION
ELLIPSOID
Adindan (Ethiopia, Mali, Senegal & Sudan)
ARC 1950 (SW & SE Africa)
ARC 1960 (Kenya, Tanzania)
Australian Geodetic Datum 1966
Australian Geodetic Datum 1984
Bukit Rimpah (Indonesia)
Camp Area Astro (Antarctica)
Chatum 1971 (New Zealand)
Carthage (Tunisia)
CAPE (South Africa)
Djakarta (Indonesia)
Clarke 1880
Clarke 1880
Clarke 1880
Australian National
Australian National
Bessel 1841
International 1924
International 1924
Clarke 1880
Clarke 1880
Bessel 1841
GPSCard™ Command Descriptions Manual Rev 3
Appendix A
GPSCard Datum
ID number
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
NAME
DX
DY
EGYPT
ED50
ED79
GUNSG
GEO49
GRB36
GUAM
HAWAII
KAUAI
MAUI
OAHU
HERAT
HJORS
HONGK
HUTZU
INDIA
IRE65
KERTA
KANDA
LIBER
LUZON
MINDA
MERCH
NAHR
NAD83
CANADA
ALASKA
NAD27
CARIBB
MEXICO
CAMER
MINNA
OMAN
PUERTO
QORNO
ROME
CHUA
SAM56
SAM69
CAMPO
SACOR
YACAR
TANAN
TIMBA
TOKYO
TRIST
VITI
WAK60
-130
-87
-86
-403
84
375
-100
89
45
65
56
-333
-73
-156
-634
289
506
-11
-97
-90
-133
-133
31
-231
0
-10
-5
-8
-7
-12
0
-92
-346
11
164
-255
-134
-288
-57
-148
-206
-155
-189
-689
-128
-632
51
101
110
-98
-98
684
-22
-111
-248
-279
-290
-290
-284
-222
46
-271
-549
734
-122
851
787
40
-771
-70
146
-196
0
158
135
160
152
130
125
-93
-1
72
138
-65
229
175
1
136
172
171
-242
691
481
438
391
52
DZ
-13
-121
-119
41
209
431
259
-183
-172
-190
-181
114
-86
-189
-201
257
611
5
86
88
-51
-72
47
482
0
187
172
176
178
190
194
122
224
-101
-189
9
-29
-376
-41
90
-6
37
-91
-46
664
-609
-36
-39
GPSCard™ Command Descriptions Manual Rev 3
DATUM DESCRIPTION
ELLIPSOID
Old Egyptian
European 1950
European 1979
G. Segara (Kalimantan - Indonesia)
Geodetic Datum 1949 (New Zealand)
Great Britain 1936 (Ordinance Survey)
Guam 1963 (Guam Island)
Hawaiian Hawaii (Old)
Hawaiian Kauai (Old)
Hawaiian Maui (Old)
Hawaiian Oahu (Old)
Herat North (Afghanistan)
Hjorsey 1955 (Iceland)
Hong Kong 1963
Hu-Tzu-Shan (Taiwan)
Indian (India, Nepal, Bangladesh)
Ireland 1965
Kertau 1948 (West Malaysia and Singapore)
Kandawala (Sri Lanka)
Liberia 1964
Luzon (Philippines excluding Mindanoa Is.)
Mindanoa Island
Merchich (Morocco)
Nahrwan (Saudi Arabia)
N. American 1983 (Includes Areas 37-42)
N. American Canada 1927
N. American Alaska 1927
N. American Conus 1927
N. American Caribbean
N. American Mexico
N. American Central America
Nigeria (Minna)
Oman
Puerto Rica and Virgin Islands
Qornoq (South Greenland)
Rome 1940 Sardinia Island
South American Chua Astro (Paraguay)
South American (Provisional 1956)
South American 1969
S. American Campo Inchauspe (Argentina)
South American Corrego Alegre (Brazil)
South American Yacare (Uruguay)
Tananarive Observatory 1925 (Madagascar)
Timbalai (Brunei and East Malaysia) 1948
Tokyo (Japan, Korea and Okinawa)
Tristan Astro 1968 (Tristan du Cunha)
Viti Levu 1916 (Fiji Islands)
Wake-Eniwetok (Marshall Islands)
Helmert 1906
International 1924
International 1924
Bessel 1841
International 1924
Airy 1830
Clarke 1866
International 1924
International 1924
International 1924
International 1924
International 1924
International 1924
International 1924
International 1924
Everest (EA)
Modified Airy
Everest (ED)
Everest (EA)
Clarke 1880
Clarke 1866
Clarke 1866
Clarke 1880
Clarke 1880
GRS-80
Clarke 1866
Clarke 1866
Clarke 1866
Clarke 1866
Clarke 1866
Clarke 1866
Clarke 1880
Clarke 1880
Clarke 1866
International 1924
International 1924
International 1924
International 1924
S. American 1969
International 1924
International 1924
International 1924
International 1924
Everest (EB)
Bessel 1841
International 1924
Clarke 1880
Hough 1960
167
Appendix A
GPSCard Datum
ID number
60
61
62
63
NAME
DX
WGS72
WGS84
ZANDE
USER
0
0
-265
0
DY
0
0
120
0
DZ
4.5
0
-358
0
DATUM DESCRIPTION
ELLIPSOID
World Geodetic System - 72
World Geodetic System - 84
Zanderidj (Surinam)
User Defined Datum Defaults
WGS-72
WGS-84
International 1924
User *
*
Default user datum is WGS 84.
*
Also see commands DATUM, page 26, and USERDATUM, page 27, in Chapter 2.
*
The GPSCard DATUM command sets the Datum value based on the name entered as listed in the “NAME” column
in Table A-2 (e.g., NAD83).
*
The following GPSCard logs report Datum used according to the “GPSCard Datum ID” column: POSA/B, P20A/B,
RT20A/B, and MKPA/B.
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GPSCard™ Command Descriptions Manual Rev 3
Appendix B
B
GPS GLOSSARY OF TERMS
ASCII – A 7 bit wide serial code describing numbers, upper and lower case alpha characters, special and non-printing
characters.
Address field – for sentences in the NMEA standard, the fixed length field following the beginning sentence delimiter
"$" (HEX 24). For NMEA approved sentences, composed of a two character talker identifier and a three
character sentence formatter. For proprietary sentences, composed of the character "P" (HEX 50) followed by a
three character manufacturer identification code.
Almanac – a set of orbit parameters that allows calculation of approximate GPS satellite positions and velocities. The
almanac is used by a GPS receiver to determine satellite visibility and as an aid during acquisition of GPS
satellite signals.
Arrival alarm – an alarm signal issued by a voyage tracking unit which indicates arrival at or at a pre-determined
distance from a waypoint [see arrival circle].
Arrival circle – an artificial boundary placed around the destination waypoint of the present navigation leg, and
entering of which will signal an arrival alarm.
Arrival perpendicular – crossing of the line which is perpendicular to the course line and which passes through the
destination waypoint.
Attenuation – reduction of signal strength
Azimuth – the horizontal direction of a celestial point from a terrestrial point, expressed as the angular distance from
000° (reference) clockwise through 360°. The reference point is generally True North, but may be Magnetic
North, or Relative (ship's head).
Bearing – the horizontal direction of one terrestrial point from another terrestrial point, expressed as the angular
distance from a reference direction, usually measured from 000° at the reference direction clockwise through
360°. The reference point may be True North, Magnetic North, or Relative (ship's head).
Carrier
– the steady transmitted RF signal whose amplitude, frequency, or phase may be modulated to carry
information.
Checksum – by NMEA standard, a validity check performed on the data contained in the sentences, calculated by the
talker, appended to the message, then recalculated by the listener for comparison to determine if the message
was received correctly. Required for some sentences, optional for all others.
Circular Error Probable (CEP) – the radius of a circle, centered at the user's true location, that contains 50 percent of
the individual position measurements made using a particular navigation system.
Coarse Acquisition (C/A) Code – a spread spectrum direct sequence code that is used primarily by commercial GPS
receivers to determine the range to the transmitting GPS satellite. Uses a chip rate of 1.023 MHz.
Communication protocol – a method established for message transfer between a talker and a listener which includes
the message format and the sequence in which the messages are to be transferred. Also includes the signaling
requirements such a bit rate, stop bits, parity, and bits per character.
Control segment – the Master Control Station and the globally dispersed Reference Stations used to manage the GPS
satellites, determine their precise orbital parameters, and synchronize their clocks.
GPSCard™ Command Descriptions Manual Rev 3
169
Appendix B
Course – the horizontal direction in which a vessel is to be steered or is being steered; the direction of travel through
the air or water. Expressed as angular distance from reference North (either true, magnetic, compass, or grid),
usually 000° (north), clockwise through 360°. Strictly, the term applies to direction through the air or water, not
the direction intended to be made good over the ground (see track). Differs from heading.
Course Made Good (CMG) – the single resultant direction from a given point of departure to a subsequent position;
the direction of the net movement from one point to the other. This often varies from the track caused by
inaccuracies in steering, currents, cross-winds, etc. This term is often considered to be synonymous with Track
Made Good, however, track made good is the more correct term.
Course Over Ground (COG) – the actual path of a vessel with respect to the Earth (a misnomer in that courses are
directions steered or intended to be steered through the water with respect to a reference meridian); this will not
be a straight line if the vessel's heading yaws back and forth across the course.
Cross Track Error (XTE) – the distance from the vessel’s present position to the closest point on a great circle line
connecting the current waypoint coordinates. If a track offset has been specified in the GPSCard SETNAV
command, the cross track error will be relative to the offset track great circle line.
Cycle slip – an error in the continuous count of carrier phase cycles.
Dead Reckoning (DR) – the process of determining a vessel's approximate position by applying from its last known
position a vector or a series of consecutive vectors representing the run that has since been made, using only the
courses being steered, and the distance run as determined by log, engine rpm, or calculations from speed
measurements.
Destination – the immediate geographic point of interest to which a vessel is navigating. It may be the next waypoint
along a route of waypoints or the final destination of a voyage.
Differential GPS (DGPS) – a technique to improve GPS accuracy that uses pseudorange errors measured at a known
location to improve the measurements made by other GPS receivers within the same general geographic area.
Dilution of Precision (DOP) – A numerical value expressing the confidence factor of the position solution based on
current satellite geometry. The lower the value, the greater the confidence in the solution. DOP can be
expressed in the following forms.
GDOP
PDOP
HTDOP
HDOP
VDOP
TDOP
-
all parameters are uncertain (latitude, longitude, height, clock offset)
3D parameters are uncertain (latitude, longitude, height)
2D parameters and time are uncertain (latitude, longitude, time)
2D parameters are uncertain (latitude, longitude)
height is uncertain
clock offset is uncertain
Doppler – the change in frequency of sound, light or other wave caused by movement of its source relative to the
observer.
Doppler aiding – a signal processing strategy, which uses a measured Doppler shift to help a receiver smoothly track
the GPS signal, to allow more precise velocity and position measurement.
Earth-Centered-Earth-Fixed (ECEF) – a right-hand Cartesian coordinate system with its origin located at the center
of the Earth. The coordinate system used by GPS to describe three-dimensional location.
ECEF – Earth-Centered-Earth-Fixed coordinates are centered on the WGS-84 reference ellipsoid, have the "Z" axis
aligned with the Earth's spin axis, the "X" axis through the intersection of the Prime Meridian and the Equator
and the "Y" axis is rotated 90 degrees East of the "X" axis about the "Z" axis.
170
GPSCard™ Command Descriptions Manual Rev 3
Appendix B
Ephemeris – a set of satellite orbit parameters that is used by a GPS receiver to calculate precise GPS satellite positions
and velocities. The ephemeris is used in the determination of the navigation solution and is updated periodically
by the satellite to maintain the accuracy of GPS receivers.
Field – a character or string of characters immediately preceded by a field delimiter.
Fixed field – a field in which the number of characters is fixed. For data fields, such fields are shown in the sentence
definitions with no decimal point. Other fields that fall into this category are the address field and the checksum
field (if present).
Flash ROM – Programmable read-only memory.
GDOP – Geometric Dilution of Precision – A numerical value expressing the confidence factor of the position solution
based on current satellite geometry. Assumes that 3D position (latitude, longitude, height) and receiver clock
offset (time) are variables in the solution. The lower the GDOP value, the greater the confidence in the solution.
Geodetic datum – the reference ellipsoid surface that defines the coordinate system.
Geoid – the figure of the earth considered as a sea level surface extended continuously through the continents. The
actual geoid is an equipotential surface coincident with mean sea level to which at every point the plumb line
(direction in which gravity acts) is perpendicular.
Geostationary – a satellite orbit along the equator that results in a constant fixed position over a particular reference
point on the earth’s surface. (GPS satellites are not geostationary.)
Global Positioning System (GPS) – full name NAVSTAR Global Positioning System, a space-based radio positioning
system which provides suitably equipped users with accurate position, velocity and time data. When fully
operational, GPS will provide this data free of direct user charge worldwide, continuously, and under all weather
conditions. The GPS constellation will consist of 24 orbiting satellites, four equally spaced around each of six
different orbiter planes. The Department of Defense under U.S. Air Force management is developing the
system.
Great circle – the shortest distance between any two points along the surface of a sphere or ellipsoid, and therefore the
shortest navigation distance between any two points on the Earth. Also called Geodesic Line.
HDOP – Horizontal Dilution of Precision - A numerical value expressing the confidence factor of the horizontal
position solution based on current satellite geometry. Makes no constraint assumptions about time, and about
height only if the FIX HEIGHT command has been invoked. The lower the HDOP value, the greater the
confidence in the solution.
HTDOP – Horizontal position and Time Dilution of Precision – A numerical value expressing the confidence factor of
the position solution based on current satellite geometry. Assumes height is known if the FIX HEIGHT
command has been invoked. If not, it will give the normalized precision of the horizontal and time parameters
given that nothing has been constrained. The lower the HTDOP value, the greater the confidence factor.
Heading – the direction in which a vessel points or heads at any instant, expressed in degrees 000° clockwise through
360° and may be referenced to True North, Magnetic North, or Grid North. The heading of a vessel is also
called the ship's head. Heading is a constantly changing value as the vessel oscillates or yaws across the course
due to the effects of the air or sea, cross currents, and steering errors.
L1 frequency – the 1575.42 MHz GPS carrier frequency, which contains the coarse acquisition (C/A) code, as well as
encrypted P-code, and navigation, messages used by commercial GPS receivers.
L2 frequency – a secondary GPS carrier, containing only encrypted P-code, used primarily to calculate signal delays
caused by the ionosphere. The L2 frequency is 1227.60 MHz.
GPSCard™ Command Descriptions Manual Rev 3
171
Appendix B
Magnetic bearing – bearing relative to magnetic north; compass bearing corrected for deviation.
Magnetic heading – heading relative to magnetic north.
Magnetic variation – the angle between the magnetic and geographic meridians at any place, expressed in degrees and
minutes east or west to indicate the direction of magnetic north from true north.
Mask angle – the minimum GPS satellite elevation angle permitted by a particular GPS receiver design. Satellites
below this angle will not be used in position solution.
Measurement error variance – the square of the standard deviation of a measurement quantity. The standard deviation
is representative of the error typically expected in a measured value of that quantity.
Multipath errors – GPS positioning errors caused by the interaction of the GPS satellite signal and its reflections.
Nanosecond – 1 x 10-9 second
Nautical mile – any of various units of distance for sea and air navigation; in the U.S. since 1959, an international unit
of linear measure equal to 1 minute of arc of a great circle of the Earth, 1,852 m (6,076 feet).
Null field – by NMEA standard, indicates that data is not available for the field. Indicated by two ASCII commas, i.e.,
",," (HEX 2C2C), or, for the last data field in a sentence, one comma followed by either the checksum delimiter
"*" (HEX 2A) or the sentence delimiters <CR><LF> (HEX 0D0A). [Note: the ASCII Null character (HEX 00)
is not to be used for null fields.]
Obscuration – term used to describe periods of time when a GPS receiver's line-of-sight to GPS satellites is blocked by
natural or man-made objects.
Origin waypoint – the starting point of the present navigation leg, expressed in latitude and longitude.
P-Code (precise or protected) – a spread spectrum direct sequence code that is used primarily by military GPS
receivers to determine the range to the transmitting GPS satellite. Uses a chipping rate of 10.23 MHz.
PDOP – Position Dilution of Precision – A numerical value expressing the confidence factor of the position solution
based on current satellite geometry. 3D position (latitude, longitude, and height) is unknown. The lower the
PDOP value, the greater the confidence factor.
PRN – PseudoRandom Noise number – the identity of the GPS satellites as determined by a GPS receiver. Since all
GPS satellites must transmit on the same frequency, they are distinguished by their pseudorandom noise codes.
Parallel receiver – a receiver that monitors four or more satellites simultaneously with independent channels.
Precise Positioning Service (PPS) – the GPS positioning, velocity, and time service which will be available on a
continuous, worldwide basis to users authorized by the U.S. Department of Defense (typically using P-Code).
Pseudolite – an Earth-based transmitter designed to mimic a satellite. May be used to transmit differential corrections.
Pseudorange – the calculated range from the GPS receiver to the satellite determined by taking the difference between
the measured satellite transmit time and the receiver time of measurement, and multiplying by the speed of light.
This measurement generally contains a large receiver clock offset error.
RT-20 – NovAtel’s Double Differencing Technology for real-time kinematic (RTK) carrier phase floating ambiguity
resolution.
Receiver channels – a GPS receiver specification that indicates the number of independent hardware signal processing
channels included in the receiver design.
Relative bearing – bearing relative to heading or to the vessel.
172
GPSCard™ Command Descriptions Manual Rev 3
Appendix B
Residual – in the context of measurements, the residual is the misclosure between the calculated measurements, using
the position solution and actual measurements.
Route – a planned course of travel, usually composed of more than one navigation leg.
Satellite elevation – the angle of the satellite above the horizon.
Selected waypoint – the waypoint currently selected to be the point toward which the vessel is travelling. Also called
"to" waypoint, destination or destination waypoint.
Selective Availability (SA) – the method used by the United States Department of Defense to control access to the full
accuracy achievable by civilian GPS equipment (generally by introducing timing and ephemeris errors).
Sequential receiver – a GPS receiver in which the number of satellite signals to be tracked exceeds the number of
available hardware channels. Sequential receivers periodically reassign hardware channels to particular satellite
signals in a predetermined sequence.
Spherical Error Probable (SEP) – the radius of a sphere, centered at the user's true location, that contains 50 percent
of the individual three-dimensional position measurements made using a particular navigation system.
Spheroid – sometimes known as ellipsoid; a perfect mathematical figure which very closely approximates the geoid.
Used as a surface of reference for geodetic surveys. The geoid, affected by local gravity disturbances, is
irregular.
Standard Positioning Service (SPS) – a positioning service made available by the United States Department of
Defense which will be available to all GPS civilian users on a continuous, worldwide basis (typically using C/A
Code).
SV -
Space Vehicle ID, sometimes used as SVID; also used interchangeably with Pseudo-Random Noise Number
(PRN).
TDOP – Time Dilution of Precision - A numerical value expressing the confidence factor of the position solution based
on current satellite geometry. The lower the TDOP value, the greater the confidence factor.
Three-dimensional coverage (hours) – the number of hours-per-day when four or more satellites are available with
acceptable positioning geometry. Four visible satellites are required to determine location and altitude.
Three-dimensional (3D) navigation – navigation mode in which altitude and horizontal position are determined from
satellite range measurements.
Time-To-First-Fix (TTFF) – the actual time required by a GPS receiver to achieve a position solution. This
specification will vary with the operating state of the receiver, the length of time since the last position fix, the
location of the last fix, and the specific receiver design.
Track – a planned or intended horizontal path of travel with respect to the Earth rather than the air or water. The track
is expressed in degrees from 000° clockwise through 360° (true, magnetic, or grid).
Track made good – the single resultant direction from a point of departure to a point of arrival or subsequent position at
any given time; may be considered synonymous with Course Made Good.
True bearing – bearing relative to true north; compass bearing corrected for compass error.
True heading – heading relative to true north.
Two-dimensional coverage (hours) – the number of hours-per-day with three or more satellites visible. Three visible
satellites can be used to determine location if the GPS receiver is designed to accept an external altitude input.
GPSCard™ Command Descriptions Manual Rev 3
173
Appendix B
Two-dimensional (2D) navigation – navigation mode in which a fixed value of altitude is used for one or more position
calculations while horizontal (2D) position can vary freely based on satellite range measurements.
Undulation – the distance of the geoid above (positive) or below (negative) the mathematical reference ellipsoid
(spheroid). Also known as geoidal separation, geoidal undulation, geoidal height.
Universal Time Coordinated (UTC) – this time system uses the second-defined true angular rotation of the Earth
measured as if the Earth rotated about its Conventional Terrestrial Pole. However, UTC is adjusted only in
increments of one second. The time zone of UTC is that of Greenwich Mean Time (GMT).
Update rate – the GPS receiver specification, which indicates the solution rate, provided by the receiver when operating
normally.
VDOP – Vertical Dilution of Precision - A numerical value expressing the confidence factor of the position solution
based on current satellite geometry. The lower the VDOP value, the greater the confidence factor.
Variable field – by NMEA standards, a data field which may or may not contain a decimal point and which may vary in
precision following the decimal point depending on the requirements and the accuracy of the measuring device.
WGS-84 – World Geodetic System 1984 is an ellipsoid designed to fit the shape of the entire Earth as well as possible
with a single ellipsoid. It is often used as a reference on a worldwide basis, while other ellipsoids are used
locally to provide a better fit to the Earth in a local region. GPS uses the center of the WGS-84 ellipsoid as the
center of the GPS ECEF reference frame.
Waypoint – a reference point on a track.
174
GPSCard™ Command Descriptions Manual Rev 3
Appendix C
C
GPS GLOSSARY OF ACRONYMS
1PPS
2D
3D
One Pulse Per Second
Two Dimensional
Three Dimensional
A/D
ADR
AGC
ASCII
Analog-to-Digital
Accumulated Doppler Range
Automatic Gain Control
American Standard Code for Information Interchange
BIST
bps
Built-In-Self-Test
Bits per Second
C/A Code
CEP
CPU
CR
CRC
CTS
Coarse/Acquisition Code
Circular Error Probable
Central Processing Unit
Carriage Return
Cyclic Redundancy Check
Clear To Send
dB
DCE
DGNSS
DGPS
DOP
DSP
DSR
DTR
Decibel
Data Communications Equipment
Differential Global Navigation Satellite System
Differential Global Positioning System
Dilution Of Precision
Digital Signal Processor
Data Set Ready
Data Terminal Ready
ECEF
ESD
Earth-Centered-Earth-Fixed
Electrostatic Discharge
GDOP
GMT
GND
GPS
Geometric Dilution Of Precision
Greenwich Mean Time
Ground
Global Positioning System
HDOP
hex
HTDOP
Hz
Horizontal Dilution Of Precision
Hexadecimal
Horizontal position and Time Dilution Of Precision
Hertz
IC
IF
I/O
IODE
IRQ
Integrated Circuit
Intermediate Frequency
Input/Output
Issue of Data (Ephemeris)
Interrupt Request
GPSCard™ Command Descriptions Manual Rev 3
175
Appendix C
LF
LHCP
LNA
LO
lsb
Line Feed
Left Hand Circular Polarization
Low Noise Amplifier
Local Oscillator
Least significant bit
MET
MEDLL
MKI
MKO
msb
msec
MSL
Multipath Elimination Technology
Multipath Estimation Delay Lock Loop
Mark In
Mark Out
Most significant bit
millisecond
Mean sea level
N. mi.
NAVSTAR
NCO
NMEA
nsec
Nautical mile
NAVigation Satellite Timing And Ranging (synonymous with GPS)
Numerically Controlled Oscillator
National Marine Electronics Association
nanosecond
OCXO
OEM
Oven Controlled Crystal Oscillator
Original Equipment Manufacturer
PC
P Code
PDOP
PLL
PPS
PRN
Personal Computer
Precise Code
Position Dilution Of Precision
Phase Lock Loop
Precise Positioning Service or Pulse Per Second
PseudoRandom Noise number
RAM
RF
RHCP
ROM
RTCA
RTCM
RTK
RTS
RXD
Random Access Memory
Radio Frequency
Right Hand Circular Polarization
Read Only Memory
Radio Technical Commission for Aviation Services
Radio Technical Commission for Maritime Services
Real Time Kinematic
Request To Send
Received Data
SA
SCAT-I
SEP
SNR
SPS
SV
SVN
Selective Availability
Special Category I
Spherical Error Probable
Signal-to-Noise Ratio
Standard Positioning Service
Space Vehicle
Space Vehicle Number
TCXO
TDOP
TTFF
TXD
Temperature Compensated Crystal Oscillator
Time Dilution Of Precision
Time-To-First-Fix
Transmitted Data
UART
UDRE
UTC
Universal Asynchronous Receiver Transmitter
User Differential Range Error
Universal Time Coordinated
176
GPSCard™ Command Descriptions Manual Rev 3
Appendix C
VARF
VDOP
Variable Frequency
Vertical Dilution of Precision
WGS
wpt
World Geodetic System
Waypoint
XTE
Crosstrack Error
GPSCard™ Command Descriptions Manual Rev 3
177
Appendix E
D
STANDARDS AND REFERENCES
RTCM STANDARDS REFERENCE
RTCA STANDARDS REFERENCE
For detailed specifications of RTCM, refer to RTCM SC104 Version 2.1 of
"RTCM Recommended Standards For Differential NAVSTAR GPS Service",
January 3, 1994
For copies of the Minimum Aviation System Performance Standards
DGNSS Instrument Approach System: Special Category-I (SCAT-I),
contact:
Radio Technical Commission for Maritime Services
1800 Diagonal Road, Suite 600
Alexandria, VA 22314 U.S.A
Telephone:
(703) 684-4481
Fax:
(703) 836-4229
Website: http://www.navcen.uscg.mil/faq/dgpsfaq1.htm#Where
RTCA, Incorporated
1140 Connecticut Avenue N.W., Suite 1020
Washington, D.C. 20036-4001 U.S.A.
Telephone:
(202) 833-9339
Fax:
(202) 833-9434
Website:
http://www.rtca.org
GPS SPS SIGNAL SPECIFICATION REFERENCE
NMEA REFERENCE
For copies of the Interface Control Document (ICD)-GPS-200, contact:
National Marine Electronics Association, NMEA 0183 Standard for
Interfacing Marine Electronic Devices, Version 2.00, January 1, 1992
ARINC Research Corporation
2551 Riva Road
Annapolis, MD 21401-7465 U.S.A.
Telephone:
(410) 266-4000
Fax:
(410) 266-4049
Website:
http://www.arinc.com
NMEA Executive Director
P.O. Box 3435
New Bern, NC 28564-3435 U.S.A.
Telephone:
(252) 638-2626
Fax:
(252) 638-4885
Website:
http://www4.coastalnet.com/nmea
GEODETIC SURVEY OF CANADA
U.S. NATIONAL GEODETIC SURVEY
Geodetic Survey of Canada
615 Boothe Street
Ottawa, ON K1A 0E9 Canada
NGS Information Services
1315 East-West Highway
Station 9244
Silver Springs, MD 20910-3282 U.S.A.
Telephone:
(301) 713-2692
Fax:
(301) 713-4172
Website:
http://www.ngs.noaa.gov
Telephone:
Fax:
Website:
(613) 995-4410
(613) 995-3215
http://www.geocan.nrcan.gc.ca/ps/geode.html
NOVATEL REFERENCE
NovAtel Inc.
th
1120-68 Avenue NE
Calgary, Alberta, Canada
T2E 8S5
Telephone:
Canada or USA 1-800-NOVATEL
International
403-295-4900
Fax:
403-295-4901
Internet:
http://www.novatel.ca
E-mail:
gps@novatel.ca
Note: Website addresses, postal addresses, and telephone numbers may be subject to change. However, they are accurate at the time of publication.
178
GPSCard™ Command Descriptions Manual Rev 3
Appendix E
E
CONVERSIONS
Section E.1 shows the conversion from Degrees to Decimal degrees. Sections E.2 to E.5 list commonly used equivalents
between the SI (Syste"me Internationale) units of weights and measures used in the metric system, and those used in the
imperial system. An example of the conversion from GPS time of week to calendar day is shown in Section E.6, while a
complete list of hexadecimal values with their binary equivalents is given in Section E.7.
E.1 DEGREES TO DECIMAL DEGREES
ÇÈ
Degrees/decimal degrees
Degrees/Minutes/Seconds
DDD = Degrees (000 - 360)
DD = Degrees (00 - 90)
DDD.ddd
MM = Minutes (00 - 60)
.mmm = decimal minutes (variable length)
SS = Seconds (00 - 60)
.sss = decimal seconds (variable length)
(.ddd * 60 = MM.mmm)
.dd m = decimal degrees derived from minutes
.dd s = decimal degrees derived from seconds
(.mmm * 60 = SS.sss)
.ddd = decimal degrees (.dd m + .dds )
DDD
MM
.dd m = M M
SS.sss
.dd s = S S . s s s
60
.ddd = (.ddm)
3600
+
(.dds )
DDD.ddd
E.2 DISTANCE MEASUREMENTS
E.3 VOLUME
1 meter (m) = 100 centimeters (cm) = 1000 millimeters (mm)
1 kilometer (km) = 1000 meters (m)
1 nautical mile = 1852 meters
1 international foot = 0.3048 meters
1 statute mile = 1609 meters
1 US survey foot = 0.3048006096 meters
1 litre (l) = 1000 cubic centimeters (cc)
1 gallon (Imperial) = 4.546 litres
1 gallon (US) = 3.785 litres
GPSCard™ Command Descriptions Manual Rev 3
179
Appendix E
E.4 TEMPERATURE
E.5 WEIGHT
degrees Celsius = (5/9) x [(degrees Fahrenheit) – 32]
degrees Fahrenheit = [(9/5) x (degrees Celsius)] + 32
1 Kilogram (kg) = 1000 grams
1 pound = 0.4536 kilogram (kg)
E.6 GPS TIME OF WEEK TO CALENDAR DAY
example:
Day 5 (Thursday) + 22 hours, 0 minutes, 0 seconds into Friday.
511200 seconds
Day
Hour
Minute
Second
511200 / 86400 seconds per day
.9166666667 x 86400 / 3600 seconds per hour
.000 x 3600 / 60 seconds per minute
.000 x 60
=
=
=
=
5.9166666667
days
22.0000 hours
0.000 minutes
0.00 seconds
E.6.1 Calendar Date To GPS Time
example:
January 22, 1995 at 11:30 hours
Days from January 6, 1980 to January 22, 1995
=
15 years x 365 days/year
=
Add one day for each leap year (a year which is divisible by 4 or 400 but not by 100; every 100 years a leap year is skipped)
Days into 1995 (22nd day is not finished)
Total days:
Deduct 5 days: Jan 1 through 5, 1980
GPS Week:
5495 x 86400 seconds per day
=
474768000 seconds/ 604800 sec per week
=
Seconds into week: 22nd day :
11.5 hrs x 3600 sec/hr
GPS time of week:
5475 days
4 days
21 days
5500 days
5495 days
785
41400 seconds
Week 785,
41400 seconds
E.7 HEXADECIMAL AND BINARY EQUIVALENTS
Hexadecimal
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
180
Binary
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
GPSCard™ Command Descriptions Manual Rev 3
Appendix F
F
COMMAND AND LOG SUMMARY CHARTS
Table F-1 GPSCard Command Summary
Command
Description
Syntax
$ALMA
$DCSA
$IONA
$RTCA
$RTCM
$UTCA
ACCEPT
ASSIGN
UNASSIGN
UNASSIGNALL
CLOCKADJUST
COMn
Injects almanac
Injects NovAtel format differential corrections
Injects ionospheric refraction corrections
Injects RTCA format DGPS corrections in ASCII (Type 1)
Injects RTCM format differential corrections in ASCII (Type 1)
Injects UTC information
Port input control (set command interpreter)
Assign a prn to a channel #
Un-assign a channel
Un-assign all channels
Adjust 1PPS continuously
Initialize Serial Port (1 or 2)
COMn_DTR
COMn_RTS
CRESET
CSMOOTH
DATUM
USERDATUM
Programmable DTR lead/tail time
Programmable RTS lead/tail time
Configuration reset to factory default
Sets carrier smoothing
Choose a DATUM name type
User defined DATUM
DGPSTIMEOUT
DYNAMICS
ECUTOFF
FIX HEIGHT
FIX POSITION
FIX VELOCITY
UNFIX
FREQUENCY_OUT
HELP or ?
LOCKOUT
UNLOCKOUT
UNLOCKOUTALL
LOG
UNLOG
UNLOGALL
MAGVAR
MESSAGES
RESET
RESETRT20
RTCM16T
Sets maximum age of differential data to be accepted and ephemeris delay
Set receiver dynamics
Set elevation cutoff angle
Sets height for 2D navigation
Set antenna coordinates for reference station
Accepts INS xyz (ECEF) input to aid in high velocity reacquisition of SVs
Remove all receiver FIX constraints
Variable frequency output (programmable)
On-line command help
Lock out satellite
Restore satellite
Restore all satellites
Choose data logging type
Kill a data log
Kill all data logs
Set magnetic variation correction
Disable error reporting from command interpreter
Performs a hardware reset (OEM only)
Performs a manual restart of RT20 mode
Enter an ASCII text message
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
(follows NovAtel ASCII log format)
accept port,option
assign channel,prn,doppler, search window
unassign channel
unassignall
clockadjust switch
comn bps,parity,databits,stopbits,
handshake,echo
comn_dtr control,active,lead,tail
comn_rts control,active,lead,tail
creset
csmooth value
datum option
userdatum semi-major,flattening,dx,dy,dz,
rx,ry,rz, scale
dgpstimeout value value
dynamics option
ecutoff angle
fix height height
fix position lat,lon,height [station id] [health]
fix velocity vx,vy,vz
unfix
frequency_out n,k
help option or ? option
lockout prn
unlockout prn
unlockoutall
log port,datatype,trigger,[period,offset]
unlog port,data type
unlogall
magvar value
messages port,option
reset
resetrt20
rtcm16t ascii message
GPSCard™ Command Descriptions Manual Rev 3
181
Appendix F
Command
Description
Syntax
RTCMRULE
RTKMODE
SAVECONFIG
SEND
SENDHEX
SETCHAN
SETDGPSID
SETHEALTH
RESETHEALTH
RESETHEALTHALL
SETNAV
Set variations of the RTCM bit rule
Set up the RTK mode
rtcmrule rule
rrtkmode argument, data range
Save current configuration in flash memory (OEM only)
Send an ASCII message to any of the communications ports
Sends non-printable characters in hexadecimal pairs
Sets maximum number of channels for tracking
Enter in a reference station ID
Override PRN health
Reset PRN health
Reset all PRN health
Set a destination waypoint
UNDULATION
VERSION
Choose undulation
Current software level
saveconfig
send port ascii-message
sendhex port data
setchan option
setdgpsid option
sethealth prn,health
resethealth prn
resethealthall
setnav from lat,from lon,to lat, to lon,track
offset, from port,to port
undulation separation
version
NOTES:
-
Commands are not case sensitive (e.g. HELP or help)
-
All commands and required entries can be separated by a space or a comma (command,variable OR command
variable).
-
A command or command string must be followed by pressing the Return key.
-
Also refer to the Command/Log Functional Relationship chart, page 183, in Appendix F.
Table F-2 GPSCard Log Summary
Syntax: log port,datatype,trigger,[period,offset]
Log Name
Binary
Description
Log ID
Log Name
Binary
Log ID
ALMA/B
CDSA/B
CLKA/B
COM1A/B
COM2A/B
18
39
02
30
31
NovAtel Format Logs
Decoded Almanac
PRTKA/B
Communication and Differential Decode Status
PXYA/B
Receiver Clock Offset Data
RALA/B
Log data from COM1
RCCA
Log data from COM2
RCSA/B
26
15
N/A
13
CONSOLEA/B
CTSA/B
DCSA/B
DOPA/B
29
19
09
07
Log data from console
Channel Tracking Status
Differential Corrections - NovAtel format
Dilution of Precision
REPA/B
RGEA/B/C/D
RT20A/B
RTCAA/B
14
32,33
35
38
GGAB
27
RTCMA/B
10
MKPA/B
MKTA/B
NAVA/B
P20A/B
PAVA/B
05
04
08
37
Global Position System Fix Data - Binary
Format
Mark Position
Time of Mark Input
Navigation Data
Computed Position – best available
RTCM16T
RTKA/B
SATA/B
SPHA/B
SVDA/B
N/A
POSA/B
01
182
Positioning Averaging Status
Computed Position
TM1A/B
VERA/B
VLHA/B
12
06
36
03
34
Description
Computed Position
Computed Cartesian Coordinate Position
Raw Almanac
Receiver Configuration
Receiver status incl. S/W version, # of working
channels, CPU idle time, BISTs status, clock status
Raw Ephemeris
Channel Range Measurements
Computed Position – Time Matched
RTCA format Differential Corrections with NovAtel
headers
RTCM SC104 Differential Corrections with NovAtel
headers
NovAtel ASCII Format – Special Message
Computed Position – Time Matched
Satellite Specific Data
Speed and Direction Over Ground
SV Position in ECEF XYZ Coordinates with
Corrections
Time of 1PPS
Receiver Hardware and Software Version Numbers
Velocity, Latency, and Direction over Ground
GPSCard™ Command Descriptions Manual Rev 3
Appendix F
Log Name
Binary
Log ID
Description
Log Name
Binary
Log ID
Description
GPALM
GPGGA
GPGLL
GPGRS
GPGSA
GPGST
N/A
N/A
N/A
N/A
N/A
N/A
NMEA Almanac Data
NMEA Global Position System Fix Data
NMEA Geographic Position - lat/lon
GPS Range Residuals for Each Satellite
NMEA GPS DOP and Active Satellites
Pseudorange Measurement Noise Statistics
N/A
N/A
N/A
N/A
N/A
NMEA GPS Satellites in View
NMEA Generic Navigation Information
NMEA GPS Specific Information
NMEA Track Made Good and Ground Speed
NMEA UTC Time and Date
NMEA UTC & Time to Destination Waypoint
RTCAA/B
38
RTCA Differential Corrections
RTCMA/B
RTCM3
RTCM16
RTCM59
10
N/A
N/A
N/A
RTCM SC104 Format, Type 1 – Differential Corrections
RTCM Format Type 3 – Reference Station Precise Position Data
RTCM Format, Type 16 – Special Message
RTCM Type 59 Proprietary Message “N” – Pseudorange and Carrier Phase Observation Data
NMEA Format Logs
GPGSV
GPRMB
GPRMC
GPVTG
GPZDA
GPZTG
RTCA Format
RTCM Format
N.B.
A/B/C
A
B
C
refers to GPSCard output logs in ASCII format.
refers to GPSCard output logs in Binary format.
refers to GPSCard output logs in Compressed binary format.
Table F-3Command/Log Relationships
The following table has been compiled to illustrate correlations among functions, commands & related logs.
COMMUNICATIONS, CONTROL AND STATUS
Related Commands
COMn
COMn_DTR
COMn_RTS
LOG
RTCMRULE
SEND
SENDHEX
RTCM16T
Descriptions
COMn port configuration control
DTR handshaking control
RTS handshaking control
Logging control
Sets up RTCM bit rule
Sends ASCII message to COM port
Sends non-printable characters
Enters an ASCII message
Related Logs
RCSA/B
CDSA/B
RTCM16T
RTCM16
COMnA/B
Descriptions
Receiver self-test status
COM port communications status
NovAtel ASCII format special message
RTCM format special message
Pass-through data logs
GENERAL RECEIVER CONTROL AND STATUS
Related Commands
VERSION
CRESET
HELP
Descriptions
Software/hardware information
Reset receiver to factory default
On-line command help
DYNAMICS
$ALMA
SAVECONFIG
Set correlator tracking bandwidth
Download almanac data file
Saves current configuration (OEM only)
GPSCard™ Command Descriptions Manual Rev 3
Related Logs
RCCA
RCSA/B
VERA/B
Descriptions
Receiver configuration status
Version and self-test status
Receiver hardware and software version
numbers
183
Appendix F
POSITION, PARAMETERS, AND SOLUTION FILTERING CONTROL
Related Commands
DATUM
USERDATUM
UNDULATION
FIX POSITION
FIX HEIGHT
FRESET
LOCKOUT
ECUTOFF
CSMOOTH
RESETRT20
$IONA
RTKMODE
Descriptions
Select a standard datum
User-customized datum
Ellipsoid-geoid separation
Constrains to fixed lat, lon, height
Constrains to fixed height (2D mode)
Clears all data which is stored in NVM
Deweights a satellite in solutions
Satellite elevation cut-off for solutions
Sets amount of carrier smoothing
Manual reset of RT20 mode
Download ionospheric correction data
Set-up the RTK mode
Related Logs
POSA/B
PXYA/B
GPGGA
GPGLL
DOPA/B
GPGSA
MKPA/B
GPGRS
GPGST
P20A/B
RT20A/B
GGAB
PRTKA/B
RTKA/B
Descriptions
Position data
Position (Cartesian x,y,z coordinates)
NMEA, position data
NMEA, position data
DOP of SVs currently tracking
NMEA, DOP information
Position at time of mark
NMEA, range residuals
NMEA, measurement noise statistics
Computed position – best available
Computed position – time matched
GPS fix data
Computed position – best available
Computed position – time matched
SATELLITE TRACKING AND CHANNEL CONTROL
Related Commands
ASSIGN
DYNAMICS
FIX VELOCITY
SETHEALTH
$ALMA
Descriptions
Satellite channel assignment
Sets correlator tracking bandwidth
Aids high velocity reacquisition
Overrides broadcast satellite health
Download almanac data file
Related Logs
CTSA/B
DOPA/B
ALMA/B
RALA/B
RGEA/B/C/D
SATA/B
SVDA/B
GPALM
GPGSA
GPGSV
Descriptions
Channel tracking status
DOP of SVs currently tracking
Current decoded almanac data
Raw almanac data (hex)
Satellite range measurements
Satellite specific information
SV position (ECEF xyz)
NMEA, almanac data
NMEA, SV DOP information
NMEA, satellite-in-view information
WAYPOINT NAVIGATION
Related Commands
SETNAV
MAGVAR
184
Descriptions
Waypoint input
Magnetic variation correction
Related Logs
NAVA/B
SPHA/B
VLHA/B
POSA/B
MKPA/B
GPRMB
GPRMC
GPVTG
GPZTG
Descriptions
Navigation waypoint status
Speed and course over ground
Velocity, latency & direction over ground
Position data
Position at time of mark input
NMEA, waypoint status
NMEA, navigation information
NMEA, track made good and speed
NMEA, time to destination
GPSCard™ Command Descriptions Manual Rev 3
Appendix F
DIFFERENTIAL REFERENCE STATION
Related Commands
FIX POSITION
RTCMRULE
Descriptions
Constrain to fixed (reference)
Selects RTCM bit rule
Related Logs
RTCM
RTCMA/B
LOG
Selects required differential-output log
RTCAA/B
DGPSTIMEOUT
SETDGPSID
POSAVE
Sets ephemeris delay
Set reference station ID
Implements position averaging for reference
station
DCSA/B
CDSA/B
ALMA/B
Descriptions
Transmits RTCM SC104 standard corrections
Transmits RTCM information in NovAtel
ASCII/binary
Transmits RTCA differential corrections in
NovAtel ASCII/bin
NovAtel format differential corrections
COM port data transmission status
Current almanac information
RGEA/B
SATA/B
RTCM3
RTCM59
PAVA/B
Channel range measurements
Satellite specific information
Reference position
NovAtel format RT-20 observation data
Parameters being used in the position
averaging process
DIFFERENTIAL REMOTE STATION
Related Commands
ACCEPT
RTCMRULE
$DCSA
$RTCM
$ALMA
$RTCA
DGPSTIMEOUT
RESETRT20
SETDGPSID
Descriptions
Accepts RTCM, RTCA, DCSB, or RT20 diff.
inputs
Selects RTCM bit rule
NovAtel format differential correction input (ASCII)
RTCM differential correction input (ASCII)
Input almanac data
RTCA differential correction input (ASCII)
Set maximum age of differential data accepted
Manual reset of RT20 mode
Select differential reference station ID to receive
Related Logs
GPGGA
Descriptions
NMEA, position fix data
GGAB
POSA/B
CDSA/B
SATA/B
VLHA/B
SVDA/B
P20A/B
RT20A/B
CDSA/B
PRTKA/B
RTKA/B
NovAtel binary version of GPGGA
Position information
Differential decode status
Satellite specific information
Velocity, latency & direction over ground
SV position in ECEF XYZ with corrections
Computed Position – best available
Computed Position – Time Matched
COM port data transmission status
Computed Position – best available
Computed Position – Time Matched
POST PROCESSING DATA
Related Commands
Depends on operating platform
Descriptions
CLOCK INFORMATION
Related Commands
CLOCKADJUST
$UTCA
Descriptions
Enable clock modeling & 1PPS adjust
Download UTC data
GPSCard™ Command Descriptions Manual Rev 3
Related Logs
RGEA/B/C/D
REPA/B
SATA/B
SVDA/B
CLKA/B
Descriptions
Satellite and ranging information
Raw ephemeris information
Satellite specific information
SV position in ECEF XYZ with corrections
Receiver clock offset information
STATUS AND TIME
Related Logs
CLKA/B
TM1A/B
MKTA/B
GPZDA
GPZTG
Descriptions
Receiver clock offset information
Time of 1PPS
Time of mark input
NMEA, UTC time and date
NMEA, UTC and time to waypoint
185
Appendix F
NAVIGATION DATA
Related Commands
186
Descriptions
Related Logs
FRMA/B
FRWA/B
Descriptions
Framed raw navigation data
Framed raw navigation words
GPSCard™ Command Descriptions Manual Rev 3
Appendix G
G
SUMMARY OF STATUS TABLES
Table 5-1 GPSCard Channel Tracking States
State
0
1
2
3
4
5
Description
Idle
Sky searching
Wide band frequency pull-in
Narrow band frequency pull-in
Phase lock loop achieved
Reacquisition
Higher numbers are reserved for future use
Table 5-2 GPSCard Solution Status
Value
0
1
2
3
4
5
6
7
Description
Solution computed
Insufficient observations
No convergence
Singular AtPA Matrix
Covariance trace exceeds maximum (trace > 1000 m)
Test distance exceeded (maximum of 3 rej if distance > 10 km)
Not yet converged from cold start
Height or velocity limit exceeded. (In accordance with COCOM
export licensing restrictions)
Higher numbers are reserved for future use
Table 5-3 Position Type
Type
0
1
2
3
4
5
Definition
No position
Single point position
Differential pseudorange position
RT-20 position
RT-2 position
WAAS position solution
Higher numbers are reserved for future use
GPSCard™ Command Descriptions Manual Rev 3
187
Appendix G
Table 5-4 RTK Status for Position Type 3 (RT-20)
Status
0
1
2
3
4
5
6
7
8
Definition
Floating ambiguity solution (converged)
Floating ambiguity solution (not yet converged)
Modeling reference phase
Insufficient observations
Variance exceeds limit
Residuals too big
Delta position too big
Negative variance
RTK position not computed
Higher numbers are reserved for future use
Table 5-5 GPSCard Receiver Self-test Status Codes
N7
N6
N5
N4
N3
N2
31 30 2 9 28 27 26 2 5 24 23 2 2 2 1 20 19 1 8 1 7 16 15 1 4 13 12 11 1 0 9
N1
8
7
6
5
N0
4
3
2
1
0
<- <- Nibble Number
Bit
Description
lsb = 0 ANTENNA
188
Range Values
Hex Value
1 = good, 0 = bad
00000001
1
2
3
4
PRIMARY PLL
RAM
ROM
DSP
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
1 = good, 0 = bad
00000002
00000004
00000008
00000010
5
6
PRIMARY AGC
COM 1
1 = good, 0 = bad
1 = good, 0 = bad
00000020
00000040
7
COM 2
1 = good, 0 = bad
00000080
8
9
WEEK
NO COARSETIME
1 = not set, 0 = set
1 = not set, 0 = set
00000100
00000200
10
11
NO FINETIME
PRIMARY JAMMER
1 = not set, 0 = set
1 = present, 0 = normal
00000400
00000800
12
13
14
15
BUFFER COM 1
BUFFER COM 2
BUFFER CONSOLE
CPUOVERLOAD
1 = overrun, 0 =normal
1 = overrun, 0 =normal
1 = overrun, 0 =normal
1 = overload, 0 = normal
00001000
00002000
00004000
00008000
16
ALMANACSAVED IN NVM
1 = yes, 0 = no
00010000
17
18
19
20
RESERVED
RESERVED
RESERVED
RESERVED
21
22
RESERVED
RESERVED
23
24
RESERVED
RESERVED
25
26
RESERVED
RESERVED
27
RESERVED
28
29
30
31
RESERVED
RESERVED
RESERVED
RESERVED
GPSCard™ Command Descriptions Manual Rev 3
Appendix G
Table 5-6 GPSCard Tracking Status
N 7
31
30
29
N 6
28
27
26
25
N 5
24
23
22
21
N 4
20
19
18
17
N 3
16
15
14
13
N 2
12
11
10
9
N 1
8
7
6
5
N 0
4
3
2
1
0
<- <- Nibble Number
Bit
Description
Range Values
lsb = 0
Hex.
1
1 Tracking state
0 - 7 See below
2
2
4
3
8
4
10
5
0-n
(0 = first, n = last)
6 Channel num ber
(n depends on GPSCard)
7
20
40
80
8
100
9 Phase lock flag
1 = Lock, 0 = Not locked
200
10 Parity known flag
1 = Known, 0 = Not known
400
11 Code locked flag
1 = Lock, 0 = Not locked
12
800
1000
13 Reserved
2000
14
4000
15
8000
16 Reserved
10000
17
20000
18 Reserved
40000
19 Grouping
1 = Grouped, 0 = Not grouped
80000
20 Frequency
1 = L2, 0 = L1
100000
21 Code type
0 = C/A
2 = P-codeless
200000
22
1=P
3 = Reserved
400000
23 Reserved
800000
24
:
Reserved
29
30 Reserved
31 Reserved
Table 5-7 GPSCard Range Reject-Codes
Value
0
1
2
3
4
5
6
7
8
9
10
11
GPSCard™ Command Descriptions Manual Rev 3
Description
Observations good
Bad health
Old ephemeris
Eccentric anomaly error
True anomaly error
Satellite coordinate error
Elevation error
Misclosure too large
No Differential Correction
No Ephemeris
Invalid IODE
Locked Out
189
Appendix G
Table 5-8 GPSCard Velocity Status
Value
190
Description
0
Velocity computed from differentially corrected carrier phase data
1
Velocity computed from differentially corrected Doppler data
2
Old velocity from differentially corrected phase or Doppler (higher latency)
3
Velocity from single point computations
4
Old velocity from single point computations (higher latency)
5
Invalid velocity
GPSCard™ Command Descriptions Manual Rev 3
Index
INDEX
1
1PPS, 109
1PPS, 23
2
2D mode, 30, 122
3
3D mode, 122
A
accumulated Doppler, 94
age of differential corrections, 78, 86, 110
almanac, 15, 56
almanac tables, 49
ambiguity, 159
antenna, 90, 120
antenna altitude, 72, 120
antenna design, 161
antenna motion, 22
antenna position, 72
antenna site, 160
ASCII log header, 48
azimuth, 103, 124
B
bandwidth, 28
bearing, 75
binary log header, 54
broadcast, 15
broadcast health, 44
buffer overload, 55
C
C/A code, 15
C/N0, 64, 94, 124
carrier phase, 92
Carrier phase, 94
carrier smoothing, 26
channel, 94
channel information, 63
channel state, 21, 94
channel status, 63
channel tracking, 21
channels (number of), 43, 89
chatter, 115
checksum, 54
GPSCard™ Command Descriptions Manual Rev 3
checksum, 54
choke ring, 148, 162
clock, 15, 92
clock adjustment, 23
clock drift, 62
clock drift rate, 23
clock frequency error, 22
clock model status, 62, 109
clock offset, 62, 69, 74, 109
COM buffers, 92
command defaults, 19
command interpreter, 114
communications port, 42
configuration, 33
configuration, 42
constellation, 15
control segment, 44
course over ground, 104
CPU, 55, 78, 89
CPU overload, 55, 92
CPU power, 144
cross track, 75
D
data injection, 48
data link, 142
datum, 82, 85
datum, 167
datum ID, 73, 82
delay lock loop, 163
de-weighting, 35
differential corrections, 30, 50, 131, 136, 144, 145
differential fix, 72, 80
differential lag, 78, 86
differential positioning, 138
direction of motion, 104
direction over ground, 110
distance, 75
Doppler, 64, 92, 94
Doppler offset, 21
double differencing, 148
E
ECEF, 32
elevation, 103
elevation cut-off, 26, 28
ellipsoid, 167
ellipsoidal datum, 27
ephemerides, 15
ephemeris, 15
error message, 39, 114
errors, 137
191
Index
F
M
factory default, 33
factory default, 19, 25, 42
flash memory, 42
magnetic variation, 75
Magnetic variation, 126
master control station, 15
mean sea level, 30, 82, 120
misclosure, 103
modem, 39, 42, 113
monitor station, 15
multipath, 158, 163
G
GDOP, 69
geodetic datum, 26, 167
geographic coordinates, 82
geoid, 30, 31, 72, 120
geoid undulation, 46
Geoid undulation, 73
geoidal separation, 72
Geoidal separation, 78, 82, 99
GPS time, 23, 56
great circle, 45
ground plane, 148, 162
H
hardware reset, 40
hdop, 120, 122
HDOP, 69
heading, 104
health, 57
height, 30
height, 78, 82, 99
Height, 73
help, 17, 34
high power signal, 92
HTDOP, 69
I
idle time, 92
Inertial Navigation System (INS), 32
ionospheric, 56
ionospheric corrections, 49, 105
ionospheric data, 48
K
kinematic, 117
L
latched time, 72
latency, 117
latency, 110
latitude, 72, 78, 82, 99, 120, 121, 126
Latitude, 73
L-band, 15
lockout satellite, 35
locktime, 26, 64, 94
longitude, 72, 73, 78, 82, 99, 120, 121, 126
192
N
narrow correlator, 163
navigation, 125
navigation, 126
navigation calculations, 45
NAVSTAR, 15
NMEA, 118
non-printable characters, 43
non-volatile memory, 33
O
offset, 52
orbit period, 15
output pulse, 32
P
pass through data, 113
pdop, 122
PDOP, 69
phase lock, 28, 94
phase lock loop, 21, 65
polarity, 159
poor reception, 48
position constraints, 32
power requirements, 91
propagation, 158
pseudorange, 105, 117
pseudorange measurement, 64, 92, 123
R
RAM, 91
range weight standard deviation, 105
raw almanac, 87, 119
reacquisition, 21, 32, 65
receiver clock offset, 109
receiver self-test, 90
receiver self-test status, 94
receiver status, 90, 92
redirect data, 113
reference station, 30, 44, 140, 144
reject code, 64, 103
GPSCard™ Command Descriptions Manual Rev 3
Index
remote station, 131, 136, 140, 144, 145
residual, 64, 103, 121
RF signal, 158
RMS, 123
RTCA, 44, 135, 136, 145
RTCA, 100
RTCM, 145
RTCM, 44, 100, 131, 132, 144
velocity latency, 111
velocity quality, 110
W
waypoint, 45, 75, 125, 128
WGS-84, 85
WGS-84, 26, 46
S
satellite, 33
segment, control, 14
segment, space, 14
segment, user, 14, 15
self-test, 88, 94
smoothing, 26
software version, 47
space vehicle number, 15
speed, 75, 104, 110, 126
speed over ground, 104, 111, 126, 127
station ID, 44, 67
subframes, 56
SV health, 119
T
TCXO, 28
TDOP, 69
track made good, 126, 127
track offset, 45
track over ground, 104, 111
tracking status, 94
transformation, 167
triangulation, 159
trigger, 36, 52
trilateration, 159
tropospheric corrections, 105
true north, 37, 75, 123
True North, 103, 104, 111
U
undulation, 73, 82
user datum, 75
UTC, 56, 58, 72, 128
UTC data, 48
UTC offset, 74, 109
UTC parameters, 50
UTC time, 120, 121, 123, 127
V
VARF, 32
VDOP, 122
velocity, 32, 75
GPSCard™ Command Descriptions Manual Rev 3
193
Printed in Canada
on recycled paper
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