Topo-Hydrographic Airborne Laser Scanner with Online Waveform Processing
Repetitive surveying of inshore waters is becoming more and more
essential to evaluate reservoir sedimentation, river degradation,
• excellently suited for combined land
and hydrographic airborne survey
water flow and water level dynamics, structure and zone variations
• high-accuracy ranging based on
echo digitization and online waveform processing with multiple target
tive way by employing high-resolution hydrographic airborne laser
• high spatial resolution due to laser
repetition rate up to 520 kHz, high
scanning speed up to 200 scanlines/
second and a wide field of view
up to 60°
Integrated into a Complete Platform for Airborne Scanning, it can
• compact, rugged and light-weight
modular configuration, compatible
with standard airborne platforms.
• optional waveform data output,
data accessible via RiWAVELiB
• seamless integration with other
RIEGL ALS Systems and
software packages
of rivers and riparian areas. This can only be achieved in an effecscanning.
The RIEGL VQ-820-G Topo-Hydrographic Airborne Laser Scanner is
specifically designed to survey seabeds or ground of rivers or lakes.
easily be installed in any type of aircraft, e.g. fixed wing or helicopter.
Laser range measurements for high resolution surveying of underwater
topography, the bottom of shallow waters and riverbeds, are carried
out with a narrow, visible green laser beam at 532 nm, emitted from a
powerful laser source. Depending on water turbidity this particular laser
wavelength allows measuring into water.
To handle target situations with complex multiple echo signals, the RIEGL
VQ-820-G gives access to detailed target parameters by digitizing the
echo signal and performing RIEGL´s highly developed online waveform
Typical applications include
• Coastline and Shallow Water Mapping
• River Bed Profiling
• Acquiring Base Data for Flood Prevention
• Measurement for Aggradation Zones
• Habitat Mapping
• Surveying for Hydraulic Engineering
• Monitoring of Hydraulics Laboratories
• Hydro-Archaeological-Surveying
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Airborne Laser Scanning
Key Features RIEGL VQ®-820-G
The RIEGL VQ-820-G consists of an unrivalled compact and lightweight
scan head connected to a powerful laser source via an armored glass
fiber cable and electrical cables, allowing easy installation into existing
and certified airborne scanning platforms and hatches of standard size
with similar key data for Fit, Form & Function, as well as in terms of power
supply requirements and weight & balance considerations - total weight
is approx. 26 kg, power consumption is less than 200 W.
photo courtesy of AHM
The scan mechanism of the VQ-820-G is based on a rotating multifacet mirror where the scan axis is tilted by about 20° with respect to
the nominal flight direction, so that the angle of incidence of the laser
beam to the water surface varies only by about 1° over the entire scan
range of up to 60°. This results in an arc-like scan pattern on ground.
Aiming at high resolution, the laser scanner emits a narrow beam of
about 1 cm diameter with a beam divergence in the range of 1 mrad.
Therefore, at the nominal flight altitude of 600 m, the spatial resolution
as defined by the laser beam geometry is in the range of 60 cm. High
spatial resolution is also supported by an exceptionally high net measurement rate of 200,000 measurements per second.
photo courtesy
of AHM
Echo Analysis
The incoming echoes are digitized at a sampling rate matched to the
pulse width. The instrument is equipped with online waveform processing. Concurrently echo waveform data can be stored for full waveform post processing by means of the optional waveform data output.
For each trigger event a so called sample block containing a certain
number of samples before and after the trigger event is recorded.
For every target echo, the position, amplitude, and pulse deviation are
determined. If the echo pulse is severely deteriorated by turbidity or
multi-target returns, this will be signaled through an increased value of
the scanner’s pulse deviation reading and the corresponding waveform
can then be analyzed with more sophisticated algorithms if requested.
Considering Refraction
Refraction is taken into account during post processing of
the data with the Hydrography AddOns available for the
well known and acknowledged RIEGL ALS software package
RiPROCESS. After georeferencing the acquired pointclouds, the water
surface is determined and targets below the water surface are shifted to
the correct position according to refraction (beam bending and waveform compression). The water surface can be defined as a simple plane
but may also be represented by a detailed model determined from the
laser scan data.
Main Dimensions
Complete Platform RIEGL CP-820-G
RIEGL VQ®-820-G Scan Head & Laser Unit
Main Dimensions
Example Project RIEGL VQ®-820-G
Floodplain Area Alongside the Danube
A small floodplain area alongside the Danube in Lower Austria was
chosen where several waterbodies of different size and depth are
available. The waterbodies were partly covered with a thin layer of ice.
At windless conditions, the water surface was perfectly flat.
VQ-820-G measurements were performed from a helicopter
platform at the following parameters:
Operating altitude:
Ground speed:
Laser pulse repetition rate:
Scanning rate:
Resulting point density:
125 m AGL
25 knots
70 lines/second
50 meas./square meter
Snapshot from a nadir-pointed video camera also showing the thin ice
layer and several power lines going over the waterbody.
Perspective view of the
flight strip with and without
subaqueous points as
well as the power lines.
The point cloud of the
power lines with masts
gives a good impression
of the very high measurement resolution.
Cross section indicating targets above water level,
subaqueous points, natural land targets and power lines.
Technical Data RIEGL VQ®-820-G
Export Classification
The VQ-820-G is subject to export restrictions as set up by the Wassenaar Arrangement.
It is classified as dual-use good according to position number 6A8j3 of the official Dual-Use-List to
be found on site http://www.wassenaar.org. Within the European Union, Council Regulation
(EC) No 428/2009 implements the export restrictions of the Wassenaar Arrangement.
The corresponding position number is 6A008j3.
The Topo-Hydrographic Airborne Laser Scanner VQ-820-G
has been designed and developed for commercial
topographic, hydrographic, and bathymetric surveying
Laser Product Classification
Laser Class
Class 3B Laser Product according to IEC60825-1:2007
The following clause applies for instruments delivered into the United States: Complies with
21 CFR 1040.10 and 1040.11 except for deviations pursuant to Laser Notice No. 50, dated June 24, 2007.
The Instrument must be used only in
combination with the appropriate laser
safety box.
532 nm
NOHD 1) 2)
100 m
1) NOHD ... Nominal Ocular Hazard Distance
2) If it can be assumed that potential viewers are hit by a single pulse only (e.g., when the instrument is
mounted on a platform moving so fast that the pulses do not overlap at the NOHD.)
Range Measurement Performance
Measuring Principle
Topography (diffusely reflecting targets)
Max. Measurement Range 3) 4)
natural targets
20 %
natural targets
60 %
Typ. Operating Flight Altitude AGL 5)
Typ. Measurement Range 4)
Typ. Operating Flight Altitude AGL
Minimum Range 7)
Accuracy 8) 10)
Precision 9) 10)
Laser Pulse Repetition Rate
Max. Effective Measurement Rate
Echo Signal Intensity
Number of Targets per Pulse
Laser Wavelength
Laser Beam Divergence
Laser Beam Footprint (Gaussian Beam Definition)
time of flight measurement, echo signal digitization, online waveform processing
1 500 m
2 500 m
1 200 m (3 900 ft.)
1 Secchi depth 6)
600 m (1 970 ft.)
10 m
25 mm
25 mm
up to 520 kHz 11)
up to 200 000 meas./sec. (@ 520 kHz PRR & 42° FOV)
for each target, high-resolution 16 bit intensity information is provided
unlimited (digitized waveform processing)
1.0 mrad 12)
100 mm @ 100 m, 1000 mm @ 1000 m
3) The following conditions are assumed: target larger than the
footprint of the laser beam, average ambient brightness,
visibilit y 23 km, perpendicular angle of incidence, ambiguity
resolved by multiple-time-around processing.
4) In bright sunlight the operational range may be considerably
shorter than under an overcast sky.
5) Reflectivit y
20%, 42° FOV, additional roll angle ±5°
6) The Secchi depth is defined as the depth at which a standard
black and white disc deployed into the water is no longer
visible to the human eye.
7) Limitation for range measurement capability, does not consider laser safety!
8) Accuracy is the degree of conformit y of a measured quantity to its actual (true) value.
9) Precision, also called reproducibilit y or repeatabilit y, is the degree to which further measure ments show
the same result.
10) Topography, one sigma @ 150m range under RIEGL test conditions.
11) Rounded values
12) Measured at the 1/e² points. 1.0 mrad corresponds to an increase of 10 0 cm of beam diameter per
100 0 m distance.
Scanner Performance
Scanning Mechanism
Scan Pattern
Field of View (selectable)
Scan Speed (selectable)
rotating multi-facet mirror
section of an ellipse
42°, max. 60° (with reduced measurement range)
Angular Step Width
50 - 200 scans/sec
0.01° (for PRR 520 kHz)
Angle Measurement Resolution
between consecutive laser shots
Data Interfaces
Scan Data Output
GNSS Interface
LAN 10/100/1 000 Mbit/sec
LAN 10/100/1 000 Mbit/sec, USB 2.0
Serial RS232 interface for data string with GNSS-time information,
TTL input for 1PPS synchronization pulse
Mechanical Interfaces
Mounting of Scan Head
Mounting of IMU Sensor
3 x M8 thread inserts in the base plate
3 x M8 thread inserts at both sides of the housing
(rigidly coupled with the internal mechanical structure)
General Technical Data
Scan Head
Power Supply Input Voltage
Power Consumption
Main Dimensions
Protection Class Scan Head
Max. Flight Altitude (operating / not operating)
Temperature Range
18 - 32 V DC
18 - 32 V DC
typ. 65 W 13)
typ. 120 W 13)
360 x 232 x 279 mm
323 x 270 x 94 mm
approx. 16 kg
approx. 9.5 kg
non condensing
IP54, dust and splash-proof
16 500 ft (5 000 m) above MSL / 18 000 ft (5 500 m) above MSL
+10°C up to +40°C (operation) / -10°C up to +50°C (storage)
13) Laser unit can be supplied through scan head resulting in typ. 185 W
total power consumption.
Laser Unit
14) For standard atmospheric conditions: 1013 mbar, +15°C at sea level
RIEGL Laser Measurement Systems GmbH
Riedenburgstraße 48
3580 Horn, Austria
Phone: +43 2982 4211 Fax: +43 2982 4210
Orlando, Florida info@rieglusa.com www.rieglusa.com
RIEGL Japan Ltd.
Tokyo, Japan info@riegl-japan.co.jp www.riegl-japan.co.jp
RIEGL China Ltd.
Beijing, China info@riegl.cn www.riegl.cn
Information contained herein is believed to be accurate and reliable. However, no responsibility
is assumed by RIEGL for its use. Technical data are subject to change without notice.
Data Sheet, RIEGL VQ-820 -G, 2015-03-24
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