Getting Started in ENVI - Harris Geospatial Solutions

Getting Started
with ENVI
ENVI Versions 4.7 and 4.7 SP1
December, 2009 Edition
Copyright © ITT Visual Information Solutions
All Rights Reserved
20GST471DOC
Restricted Rights Notice
The IDL®, IDL Advanced Math and Stats™, ENVI®, ENVI Zoom™, and ENVI® EX software programs and the accompanying procedures, functions,
and documentation described herein are sold under license agreement. Their use, duplication, and disclosure are subject to the restrictions stated in the
license agreement. ITT Visual Information Solutions reserves the right to make changes to this document at any time and without notice.
Limitation of Warranty
ITT Visual Information Solutions makes no warranties, either express or implied, as to any matter not expressly set forth in the license agreement,
including without limitation the condition of the software, merchantability, or fitness for any particular purpose.
ITT Visual Information Solutions shall not be liable for any direct, consequential, or other damages suffered by the Licensee or any others resulting
from use of the software packages or their documentation.
Permission to Reproduce this Manual
If you are a licensed user of these products, ITT Visual Information Solutions grants you a limited, nontransferable license to reproduce this particular
document provided such copies are for your use only and are not sold or distributed to third parties. All such copies must contain the title page and this
notice page in their entirety.
Export Control Information
This software and associated documentation are subject to U.S. export controls including the United States Export Administration Regulations. The
recipient is responsible for ensuring compliance with all applicable U.S. export control laws and regulations. These laws include restrictions on
destinations, end users, and end use.
Acknowledgments
ENVI® and IDL® are registered trademarks of ITT Corporation, registered in the United States Patent and Trademark Office. ION™, ION Script™,
ION Java™, and ENVI Zoom™ are trademarks of ITT Visual Information Solutions.
ESRI®, ArcGIS®, ArcView®, and ArcInfo® are registered trademarks of ESRI.
Portions of this work are Copyright © 2009 ESRI. All rights reserved.
PowerPoint® and Windows® are registered trademarks of Microsoft Corporation in the United States and/or other countries.
Macintosh® is a registered trademark of Apple Inc., registered in the U.S. and other countries.
UNIX® is a registered trademark of The Open Group.
Adobe Illustrator® and Adobe PDF® Print Engine are either registered trademarks or trademarks of Adobe Systems Incorporated in the United States
and/or other countries.
Numerical Recipes™ is a trademark of Numerical Recipes Software. Numerical Recipes routines are used by permission.
GRG2™ is a trademark of Windward Technologies, Inc. The GRG2 software for nonlinear optimization is used by permission.
NCSA Hierarchical Data Format (HDF) Software Library and Utilities. Copyright © 1988-2001, The Board of Trustees of the University of Illinois. All
rights reserved.
NCSA HDF5 (Hierarchical Data Format 5) Software Library and Utilities. Copyright © 1998-2002, by the Board of Trustees of the University of
Illinois. All rights reserved.
CDF Library. Copyright © 2002, National Space Science Data Center, NASA/Goddard Space Flight Center.
NetCDF Library. Copyright © 1993-1999, University Corporation for Atmospheric Research/Unidata.
HDF EOS Library. Copyright © 1996, Hughes and Applied Research Corporation.
SMACC. Copyright © 2000-2004, Spectral Sciences, Inc. and ITT Visual Information Solutions. All rights reserved.
This software is based in part on the work of the Independent JPEG Group.
Portions of this software are copyrighted by DataDirect Technologies, © 1991-2003.
BandMax®. Copyright © 2003, The Galileo Group Inc.
Portions of this computer program are copyright © 1995-2008 Celartem, Inc., doing business as LizardTech. All rights reserved. MrSID is protected by
U.S. Patent No. 5,710,835. Foreign Patents Pending.
Portions of this software were developed using Unisearch’s Kakadu software, for which ITT has a commercial license. Kakadu Software. Copyright ©
2001. The University of New South Wales, UNSW, Sydney NSW 2052, Australia, and Unisearch Ltd, Australia.
This product includes software developed by the Apache Software Foundation (www.apache.org/).
MODTRAN is licensed from the United States of America under U.S. Patent No. 5,315,513 and U.S. Patent No. 5,884,226.
QUAC and FLAASH are licensed from Spectral Sciences, Inc. under U.S. Patent No. 6,909,815 and U.S. Patent No. 7,046,859 B2.
Portions of this software are copyrighted by Merge Technologies Incorporated.
Support Vector Machine (SVM) is based on the LIBSVM library written by Chih-Chung Chang and Chih-Jen Lin (www.csie.ntu.edu.tw/~cjlin/libsvm),
adapted by ITT Visual Information Solutions for remote sensing image supervised classification purposes.
IDL Wavelet Toolkit Copyright © 2002, Christopher Torrence.
IMSL is a trademark of Visual Numerics, Inc. Copyright © 1970-2006 by Visual Numerics, Inc. All Rights Reserved.
Other trademarks and registered trademarks are the property of the respective trademark holders.
Contents
Chapter 1
Introduction to ENVI ................................................................................ 9
What is ENVI? ................................................................................................................
ENVI + IDL, ENVI, and IDL ...................................................................................
About ENVI Functionality ..............................................................................................
End-to-End Processing .............................................................................................
Hyperspectral Data Analysis ....................................................................................
About ENVI Zoom ..........................................................................................................
About ENVI EX ..............................................................................................................
ENVI Add-On Modules ..................................................................................................
DEM Extraction ........................................................................................................
ENVI Orthorectification ...........................................................................................
Atmospheric Correction: QUAC and FLAASH .......................................................
NITF/NSIF ................................................................................................................
Using This Guide .............................................................................................................
Getting Started with ENVI
10
11
12
12
13
14
15
16
16
16
16
17
18
3
4
Additional ENVI Documentation .................................................................................... 19
ENVI Support .................................................................................................................. 21
Contacting Technical Support ................................................................................... 21
Contacting Sales ........................................................................................................ 21
Training and Custom Development Services .................................................................. 22
ENVI Training ........................................................................................................... 22
Additional Resources ....................................................................................................... 23
ITT Visual Information Solutions Website ............................................................... 23
IDL Newsgroup ......................................................................................................... 23
Chapter 2
Before You Begin .................................................................................. 25
Starting and Exiting ENVI ............................................................................................... 26
Using Startup Scripts ................................................................................................. 26
Exiting ENVI ............................................................................................................. 28
ENVI Image Files ............................................................................................................ 29
ENVI Header Files ........................................................................................................... 30
ENVI File Naming Conventions ...................................................................................... 31
ENVI Supported Input File Formats ................................................................................ 33
ENVI Supported Output File Formats ............................................................................. 35
Chapter 3
The ENVI Interface ................................................................................ 37
The ENVI Main Menu Bar .............................................................................................. 38
The Available Bands List ................................................................................................. 39
Folding and Unfolding Data Sets .............................................................................. 40
Opening Files from the Available Bands List ........................................................... 41
Opening Files in ArcMap .......................................................................................... 41
Opening Files in ENVI Zoom ................................................................................... 42
Closing Files from the Available Bands List ............................................................ 42
Hiding and Showing the Available Bands List ......................................................... 43
Available Bands List Right-Click Menus ................................................................. 44
Locating Bands by Wavelength ................................................................................ 45
Showing Displayed Band Information ...................................................................... 45
Display Groups ................................................................................................................ 46
Reduced Resolution Data Sets .................................................................................. 48
Opening New Display Groups .................................................................................. 48
Contents
Getting Started with ENVI
5
Resizing Display Group Windows ...........................................................................
Maximizing Open Displays ......................................................................................
Positioning the Zoom and Scroll Windows ..............................................................
Displaying Scroll Bars ..............................................................................................
Hiding and Unhiding Display Group Windows .......................................................
Display Group Right-Click Menus ...........................................................................
Controlling the Zoom Window .................................................................................
Controlling the Scroll Window .................................................................................
Using the Window Finder .........................................................................................
Saving Display Groups .............................................................................................
Restoring Saved Display Groups ..............................................................................
Setting Preferences for an Individual Display Group ...............................................
Closing Display Groups ............................................................................................
The Available Vectors List ..............................................................................................
Opening Files from the Available Vectors List ........................................................
Opening Vector Layers in ENVI Zoom ....................................................................
Opening Vector Layers in ArcMap ..........................................................................
Opening New Vector Windows ................................................................................
Editing Layer Names ................................................................................................
Creating New Layers ................................................................................................
Saving Vector Layers ................................................................................................
The Remote Connection Manager ...................................................................................
Vector Displays ...............................................................................................................
Starting New Vector Windows .................................................................................
Zooming In and Out of Vector Windows .................................................................
Panning in Vector Windows .....................................................................................
Using Cursor Tracking in Vector Windows .............................................................
Vector Options ..........................................................................................................
Vector Attributes .......................................................................................................
Plot Windows ..................................................................................................................
Opening New Plot Windows ....................................................................................
Closing All Plot Windows ........................................................................................
ENVI Mouse Buttons ......................................................................................................
Image Window Mouse Button Functions .................................................................
Zoom Window Mouse Button Functions ..................................................................
Scroll Window Mouse Button Functions ..................................................................
Getting Started with ENVI
48
49
49
49
50
50
52
55
56
57
57
58
60
61
62
62
62
63
63
63
64
67
68
71
71
71
71
72
72
73
74
74
75
76
76
77
Contents
6
Vector Window Mouse Button Functions ................................................................. 78
Plot Window Mouse Button Functions ..................................................................... 79
Chapter 4
Opening and Displaying Files ............................................................. 81
Opening Image Files in ENVI ......................................................................................... 82
Supported Platforms .................................................................................................. 83
Opening External Image Files in ENVI ......................................................................... 101
Opening Previously Opened Files ................................................................................. 102
Opening Vector Files ..................................................................................................... 103
Opening Spectral Library Files ...................................................................................... 106
Displaying Images ......................................................................................................... 107
Displaying Gray Scale Images ................................................................................ 108
Displaying RGB Images .......................................................................................... 109
Displaying True Color or Color Infrared Images .................................................... 109
Displaying Default RGB Combinations .................................................................. 111
Displaying Vectors ......................................................................................................... 112
Chapter 5
Working with Header Files ................................................................. 113
The ENVI Header Format .............................................................................................. 114
Example ENVI Header File .................................................................................... 120
Creating Header Files .................................................................................................... 123
Importing Header Information from Other Files ..................................................... 124
Entering Required Header Information ................................................................... 125
Entering Optional Header Information .................................................................... 125
Editing Header Files ...................................................................................................... 127
ENVI File Type File ...................................................................................................... 128
ENVI Sensor File ........................................................................................................... 130
Chapter 6
Common Tools and Functions in ENVI ............................................. 133
Working with ENVI Dialogs ......................................................................................... 134
ENVI Dialog Components ...................................................................................... 134
The Input File Dialog .............................................................................................. 136
Selecting Multiple Items in Lists ............................................................................. 138
Selecting Output to File or Memory ........................................................................ 139
Contents
Getting Started with ENVI
7
Queuing ENVI Processes ........................................................................................
Compressing Output ...............................................................................................
Closing Dialog Windows ........................................................................................
Selecting Bands or Files for Processing ........................................................................
Selecting a Spatial Subset .......................................................................................
Selecting a Spectral Subset .....................................................................................
Selecting a Mask .....................................................................................................
ENVI Processing Status Window ..................................................................................
Showing Display Group Information ............................................................................
Displaying Pixel Location .............................................................................................
Displaying Cursor Location/Value ................................................................................
Cursor Location/Value Reporting Options .............................................................
Collecting Points ...........................................................................................................
Linking Display Groups ................................................................................................
Using Dynamic Overlays ..............................................................................................
Annotating Displays ......................................................................................................
Defining Regions of Interest .........................................................................................
Turning Off ROI Definition ....................................................................................
Using the Available Files List .......................................................................................
Viewing File Information .......................................................................................
Editing Header Files from the Available Files List ................................................
Opening New Files from the Available Files List ..................................................
Closing All Files from the Available Files List ......................................................
Deleting Memory Items ..........................................................................................
Storing Files in Memory .........................................................................................
Saving In-Memory Files to Disk ............................................................................
Deleting Files from Disk .........................................................................................
Closing Selected Files .............................................................................................
140
141
142
143
143
145
145
147
148
149
151
152
154
155
156
157
159
161
162
163
163
163
163
164
164
164
164
165
Chapter 7
Creating Output ................................................................................... 167
Saving Image Files ........................................................................................................
Saving as Standard ENVI Files ..............................................................................
Saving as ENVI Meta Files ....................................................................................
Saving as ASCII Files .............................................................................................
Saving Display Output ..................................................................................................
Getting Started with ENVI
168
168
170
171
173
Contents
8
Printing in ENVI ............................................................................................................ 174
Changing Output Directories ......................................................................................... 176
Chapter 8
Configuring and Customizing ENVI .................................................. 177
Setting ENVI Preferences .............................................................................................. 178
User-Defined File Preferences ................................................................................ 179
Default Directory Preferences ................................................................................. 181
Display Default Preferences .................................................................................... 181
ENVI Graphics Colors ............................................................................................ 182
Plot Default Preferences .......................................................................................... 183
Grid Line Default Preferences ................................................................................. 185
Previous Files List Preferences ............................................................................... 185
Miscellaneous Preferences ...................................................................................... 186
Customizing ENVI ......................................................................................................... 188
Customizing ENVI in a Multiple-User Windows Environment ............................. 188
Customizing ENVI in UNIX ................................................................................... 189
Platform-Specific Customization ............................................................................ 191
Customizing Configuration and Definition Files .................................................... 193
Using IDL with ENVI .................................................................................................... 196
Importing IDL Variables ......................................................................................... 196
Exporting to IDL Variables ..................................................................................... 197
Compiling IDL Code ............................................................................................... 197
Appendix 9
Glossary .............................................................................................. 199
Index .................................................................................................... 229
Contents
Getting Started with ENVI
Chapter 1
Introduction to ENVI
This chapter provides a general overview of ENVI. It includes:
What is ENVI? . . . . . . . . . . . . . . . . . . . . . .
About ENVI Functionality . . . . . . . . . . . . .
About ENVI Zoom . . . . . . . . . . . . . . . . . . .
About ENVI EX . . . . . . . . . . . . . . . . . . . . .
ENVI Add-On Modules . . . . . . . . . . . . . . .
Getting Started with ENVI
10
12
14
15
16
Using This Guide . . . . . . . . . . . . . . . . . . . .
Additional ENVI Documentation . . . . . . . .
ENVI Support . . . . . . . . . . . . . . . . . . . . . . .
Training and Custom Development Services
22
Additional Resources . . . . . . . . . . . . . . . . .
18
19
21
..
23
9
10
Chapter 1: Introduction to ENVI
What is ENVI?
ENVI is the ideal software for the visualization, analysis, and presentation of all types
of digital imagery. ENVI’s complete image-processing package includes advanced,
yet easy-to-use, spectral tools, geometric correction, terrain analysis, radar analysis,
raster and vector GIS capabilities, extensive support for images from a wide variety
of sources, and much more.
ENVI’s unique approach to image processing combines file-based and band-based
techniques with interactive functions. When you open a data input file, its bands are
stored in a list where you can access them from all system functions. If you open
multiple files, you can process bands of disparate data types as a group. ENVI’s
interactive analysis capabilities include:
•
Multiple dynamic overlay capabilities that allow easy comparison of images in
multiple displays.
•
Real-time extraction and linked spatial/spectral profiling from multispectral
and hyperspectral data that provide you with new ways of looking at highdimensional data.
•
Interactive tools to view and analyze vectors and GIS attributes.
•
Standard capabilities, such as contrast stretching and 2D scatter plots.
ENVI’s interface is complemented by its comprehensive library of processing
algorithms. ENVI includes all the basic image processing functions. ENVI does not
impose limitations on the number of spectral bands that you can process, so you can
use either multispectral or hyperspectral data sets. ENVI also includes advanced tools
for analyzing radar data sets.
ENVI addresses common image processing problem areas such as input of nonstandard data types, viewing and analysis of large images, and simple extensions of
analysis capabilities (add-on functions). The software includes essential tools
required for image processing across multiple disciplines, and it has the flexibility to
allow implementation of customized analysis strategies.
What is ENVI?
Getting Started with ENVI
Chapter 1: Introduction to ENVI
11
ENVI + IDL, ENVI, and IDL
ENVI is written in IDL (Interactive Data Language), a powerful structured
programming language that offers integrated image processing. The flexibility of
ENVI is due largely to IDL’s capabilities.
There are two types of ENVI licenses:
•
ENVI + IDL: ENVI plus a full version of IDL
•
ENVI: ENVI plus a runtime version of IDL
ENVI + IDL users can use IDL to customize their own command-line functions.
Advanced ENVI + IDL users should find the flexibility offered by IDL’s interactive
features helpful for their dynamic image analyses.
Getting Started with ENVI
What is ENVI?
12
Chapter 1: Introduction to ENVI
About ENVI Functionality
ENVI simplifies comprehensive interactive processing of large multiband data sets,
screen-sized images, spectral plots and libraries, and image regions of interest
(ROIs), while providing flexible display capabilities and geographic-based image
browsing. ENVI provides a multitude of interactive functions, including:
•
x,y,z profiling
•
Image transects
•
Linear and non-linear histogramming and contrast stretching
•
Color tables
•
Density slicing
•
Classification color mapping
•
Quick filter preview
•
ROI definition and processing
•
Vector creation and display
ENVI provides methods for locating specific pixels and for interactive
spatial/spectral pixel editing. It also offers interactive scatter plot functions, including
2D dancing pixels and the n-Dimensional Visualizer. With ENVI, you can
interactively link images together and create dynamic overlays, create comprehensive
vector overlays with GIS attributes, and add map grids as well as annotations to
images. Other ENVI interactive functions include 3D (perspective) viewing and flythrough animation, surface shading, and geometric rectification and mosaicking.
ENVI functionality works with full data files and subsets. It provides a complete set
of tools to process panchromatic images, AVHRR, Landsat TM, ASTER, MODIS,
QuickBird, WorldView, IKONOS, Orbview-3, and ENVISAT data, as well as dozens
of other data types. ENVI is also capable of processing many other multispectral and
hyperspectral images, and data from advanced SAR systems.
End-to-End Processing
ENVI includes tools for complete end-to-end processing of any type of remotely
sensed imagery. From orthorectification to information extraction to integration with
geographic information systems (GIS), ENVI combines all the tools you need for any
type of project.
About ENVI Functionality
Getting Started with ENVI
Chapter 1: Introduction to ENVI
13
Hyperspectral Data Analysis
ENVI provides a full suite of tools for processing hyperspectral data. Developed by
experts in the field, ENVI’s spectral analysis tools are unequaled. Among others,
ENVI provides tools for:
•
Sub-pixel analysis
•
Feature extraction
•
Spectrum identification
•
Anomaly detection
•
Mapping of materials
•
Target finding
Getting Started with ENVI
About ENVI Functionality
14
Chapter 1: Introduction to ENVI
About ENVI Zoom
ENVI Zoom is a simplified, yet powerful, version of ENVI that lets you display and
manipulate remote sensing images, vectors, and annotation, with ease and efficiency.
The interface provides quick access to common display tools such as contrast,
brightness, sharpening, and transparency. You can also re-project and re-sample
images and vectors on-the-fly. ENVI Zoom provides tools to help you keep track of
multiple data sets and their properties, and it includes a Portal viewer to let you see
multiple data sets at once. ENVI Zoom also contains the robust RX Anomaly
Detection, Pan Sharpening, and Vegetation Suppression tools.
For more information, see the ENVI Zoom User’s Guide.
About ENVI Zoom
Getting Started with ENVI
Chapter 1: Introduction to ENVI
15
About ENVI EX
ENVI EX is ENVI’s image processing and analysis solution for GIS users. ENVI EX
includes advanced image manipulation tools that allow you to interactively visualize
your data.
With ENVI EX, you can perform image processing tasks like pan sharpening,
vegetation suppression, and anomaly detection quickly and easily from the ENVI EX
toolbox.
The ENVI EX automated image analysis workflows take the complexity out of image
processing. They provide step by step procedures and instructions to guide you
through orthorectifying images, detecting change in an area over time, finding
features of interest over a wide area, and classifying land cover. All of the processing
and analysis tools in ENVI EX are based on ENVI’s scientific algorithms and
methods.
Getting Started with ENVI
About ENVI EX
16
Chapter 1: Introduction to ENVI
ENVI Add-On Modules
ITT Visual Information Solutions offers several add-on modules to extend ENVI’s
functionality. User documentation for each are included in PDF format on the ENVI
Resource DVD (included with your software), and in the ENVI Help. Each module
requires an additional license in your installation; contact your ENVI sales
representative to obtain a license.
DEM Extraction
The ENVI Digital Elevation Model (DEM) Extraction Module enables you to extract
elevation data from pushbroom stereo images, such as those from the ALOS PRISM,
ASTER, CARTOSAT-1, FORMOSAT-2, GeoEye-1, IKONOS, KOMPSAT-2,
OrbView-3, QuickBird, WorldView-1, WorldView-2, and SPOT satellites. The DEM
Extraction Module includes the DEM Extraction Wizard and three DEM tools the
DEM Editing Tool, Stereo Pair 3D Measurement Tool, and Epipolar 3D Cursor Tool.
See the DEM Extraction Module User’s Guide for details about using the DEM
Extraction Module.
ENVI Orthorectification
The ENVI Orthorectification Module allows you to build highly accurate
orthorectified images by rigorously modeling the object-to-image transformation.
The details of this transformation are mostly transparent, which means you can
quickly create orthorectified images without defining any detailed model parameters.
For more information, see the ENVI Orthorectification Module User’s Guide.
Atmospheric Correction: QUAC and FLAASH
For those interested in quantitative analysis of surface reflectance, removing the
influence of the atmosphere is a critical pre-processing step. ENVI’s Atmospheric
Correction Module provides two options: Quick Atmospheric Correction (QUAC)
and Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes (FLAASH).
The Atmospheric Correction Module allows you to accurately remove the obscuring
effects of the atmosphere. QUAC and FLAASH were developed by Spectral
Sciences, Inc., a world leader in optical phenomenology research, in collaboration
with U.S. Air Force Research Laboratory (AFRL) and Spectral Information
Technology Application Center (SITAC) personnel.
ENVI Add-On Modules
Getting Started with ENVI
Chapter 1: Introduction to ENVI
17
See the Atmospheric Correction Module User’s Guide for details about using QUAC
and/or FLAASH.
NITF/NSIF
The ENVI National Imagery Transmission Format (NITF) and NATO Secondary
Image Format (NSIF) Module and NITF for ArcGIS® support reading and writing
image files in the NITF and NSIF formats. The NITF/NSIF Module and NITF for
ArcGIS provide compliant NITF software environments that take advantage of
ENVI’s image analysis capabilities. With the NITF/NSIF Module and NITF for
ArcGIS, ENVI and ArcMap™ can read and display all compressed or uncompressed
NITF version 2.0 and 2.1 and NSIF 1.0 files, as well as legacy NITF 1.1 files, and
write NITF version 2.0 and 2.1 and NSIF 1.0 files.
See the NITF/NSIF Module User’s Guide for details about using the NITF/NSIF
Module.
The NITF for ArcGIS license is included with the NITF Module license. It can also
be purchased separately at additional cost from ITT Visual Information Solutions,
ESRI®, or your ENVI Distributor. If you have ArcGIS 9.3 or later installed, you can
license NITF then install and run NITF for ArcGIS. NITF for ArcGIS provides the
ability to read NITF data within the ArcGIS environment and create data products
with ArcGIS Desktop that comply with the latest NITF specifications.
ENVI also supports reading TFRD files, but requires a separate module license and
install. These can be obtained by contacting ITT Visual Information Solutions.
Getting Started with ENVI
ENVI Add-On Modules
18
Chapter 1: Introduction to ENVI
Using This Guide
This guide describes the general concepts of ENVI and provides overviews of the
more commonly used functions of the application. For detailed information on how to
use specific ENVI functions, see ENVI Help. This guide discusses:
•
ENVI basics, such as starting and exiting ENVI, image and header files, file
naming conventions, supported image file formats.
•
The most commonly used areas of the ENVI interface, including the ENVI
main menu bar, the Available Bands List, display groups, the Available Vectors
List, Vector windows, plot windows, and mouse button behavior for the
different ENVI windows and displays.
•
How to open and display image files and vector files in ENVI, the header files
associated with a image files, and how to create output of ENVI data.
•
How to configure and customize your ENVI installation.
For the Introduction to ENVI tutorial and other ENVI tutorials, visit the ITT Visual
Information Solutions website.
Using This Guide
Getting Started with ENVI
Chapter 1: Introduction to ENVI
19
Additional ENVI Documentation
ENVI provides the following documentation in addition to this guide. Most of the
documentation is available as a download from the ITT Visual Information Solutions
website and/or on the ENVI Resource DVD, which is included with your installation
package.
•
ENVI Help
A compilation of all of the ENVI documentation in a searchable help format.
ENVI Help is included with your ENVI installation, and you can access it by
selecting Help → Start ENVI Help from the ENVI main menu bar. For
Windows, you can optionally access Help by selecting Programs → ENVI
x.x → ENVI Help from the Windows Start menu. For UNIX, you can
optionally access ENVI Help by typing either envihelp, envi_tut, or
envi man at the UNIX prompt (your environment variables must be
appropriately set up).
•
ENVI Zoom Help
The ENVI Zoom User’s Guide in a searchable help format. ENVI Zoom Help
is included with your ENVI Zoom installation, and you can access it by
selecting Help from the ENVI Zoom menu bar.
•
Installation and Licensing Guide
Describes how to install and license ENVI on your machine.
•
ENVI User’s Guide
Provides step-by-step instructions for working with ENVI.
•
ENVI Zoom User’s Guide
Provides step-by-step instructions for working with ENVI Zoom.
•
ENVI Programmer’s Guide
Provides sample code and instructions on programming in ENVI.
•
ENVI Reference Guide
Alphabetically documents all ENVI library routines. Each routine includes a
description, the syntax, arguments (if any), keywords (if any), and an example
of using the routine.
•
ENVI Tutorials
Provides tutorials designed to lead a new user through ENVI’s basic and
advanced functionality. You need a free customer login to access tutorials from
the ITT Visual Information Solutions website. Tutorials are also provided in
PDF format on the ENVI Resource DVD included with your ENVI
installation.
Getting Started with ENVI
Additional ENVI Documentation
20
Chapter 1: Introduction to ENVI
•
ENVI DEM Extraction Module User’s Guide
Describes how to use the DEM Extraction Module.
•
ENVI Orthorectification Module User’s Guide
Describes how to use the Orthorectification Module.
•
ENVI Atmospheric Correction Module User’s Guide
Describes how to use the Atmospheric Correction tools QUAC and FLAASH.
•
ENVI NITF/NSIF Module User’s Guide
Describes how to use the NITF/NSIF Module.
If you purchased an ENVI + IDL license, the following IDL documentation is
available:
•
IDL Online Help
Provides all of the IDL documentation, compiled into a searchable help format.
IDL Online Help is included with your ENVI + IDL installation and is
accessed by selecting Help → Contents from the IDL main menu bar.
•
Using IDL
Provides the basics of using IDL. This document is included in IDL Online
Help.
•
IDL Reference Guide
Alphabetically documents all IDL Functions and procedures. This document is
included in IDL Online Help.
Additional ENVI Documentation
Getting Started with ENVI
Chapter 1: Introduction to ENVI
21
ENVI Support
If you experience a problem with ENVI, first verify that the issue is not a result of
misinterpreting the expected outcome of a specific function or action. Double-check
the ENVI documentation and ENVI Help, or check with a local expert. Make sure
your system is properly configured with enough virtual memory and sufficient
operating system quotas.
If the problem still occurs, report it to Technical Support quickly, so that the issue can
be resolved, or a workaround can be provided. If you cannot find the information you
need in the ENVI documentation or ENVI Help, report this to Technical Support as
well, so that the documentation can be updated.
Contacting Technical Support
To report a problem, you can call, e-mail, or go online to submit a Support Incident:
Technical Support Direct: 303-413-3920
E-Mail: support@ittvis.com
Internet: Go to www.ittvis.com and select Support → Technical Support.
ITT Visual Information Solutions
4990 Pearl East Circle
Boulder, CO 80301 USA
Phone: 303-786-9900
Fax: 303-786-9909
Contacting Sales
Contact ITT Visual Information Solutions Sales to purchase add-on module licenses
or additional ENVI licenses:
ITT Visual Information Solutions
4990 Pearl East Circle
Boulder, CO 80301 USA
Phone: 303-786-9900
Fax: 303-786-9909
E-Mail: sales@ittvis.com
E-Mail (SPAN): ORION::IDL
Getting Started with ENVI
ENVI Support
22
Chapter 1: Introduction to ENVI
Training and Custom Development Services
ITT Visual Information Solutions has a team of Professional Services Group (PSG)
consultants who provide custom software development, consulting services, and
training to commercial, research, and government markets. The PSG team can either
help you define requirements and lead your development cycle from prototyping to
final installation, or they can join your project mid-stream and provide expert
assistance.
Each PSG team member offers expertise in areas such as image processing; data
analysis; visualization; software development; a broad range of scientific application
areas; and government civilian, defense, and intelligence community requirements. If
needed, ITT Visual Information Solutions has staff with the necessary security
clearances to support classified projects.
The PSG team is experienced in extending ENVI’s robust suite of user functions and
batch programming capabilities, and has up-to-date knowledge on recent product
enhancements and future product direction. Their contact information is as follows:
Professional Services Group
ITT Visual Information Solutions
4990 Pearl East Circle
Boulder, CO 80301 USA
Phone: 303-786-9900
Fax: 303-786-9909
E-Mail: sales@ittvis.com
ENVI Training
ITT Visual Information Solutions offers training courses designed to teach users
about ENVI functions. ITT Visual Information Solutions teaches regularly scheduled
ENVI courses at our training facility in Boulder, Colorado. In addition, ITT Visual
Information Solutions offers regional training classes every year at various locations
in the United States, Europe, and Australia. For the latest training schedule, a detailed
course outline, or the cost of a training course, call, send e-mail, or go online:
Phone: 303-786-9900 (ask for Training)
Fax: 303-786-9909
E-Mail: training@ittvis.com
Internet: Go to www.ittvis.com and select Events and Training.
Training and Custom Development Services
Getting Started with ENVI
Chapter 1: Introduction to ENVI
23
Additional Resources
There are two additional resources for ENVI support, the ITT Visual Information
Solutions website and the IDL newsgroup.
ITT Visual Information Solutions Website
The ITT Visual Information Solutions website has several links that provide
additional ENVI support. The website includes access to user-contributed ENVI
code, an ENVI user forum, an IDL user forum, and technical tips. Go to
www.ittvis.com and select User Community to select an option.
IDL Newsgroup
The Usenet newsgroup comp.lang.idl-pvwave is dedicated to the discussion
of IDL. Users post questions and answers and share information about their own IDL
projects. Note that many ITT Visual Information Solutions employees read this
newsgroup, but do not usually post messages to the group.
Send problem reports and technical support questions to ITT Visual Information
Solutions via phone or e-mail. See “Contacting Technical Support” on page 21.
Getting Started with ENVI
Additional Resources
24
Additional Resources
Chapter 1: Introduction to ENVI
Getting Started with ENVI
Chapter 2
Before You Begin
This chapter describes the basic components of ENVI. It includes:
Starting and Exiting ENVI . . . . . . . . . . . . . 26
ENVI Image Files . . . . . . . . . . . . . . . . . . . . 29
ENVI Header Files . . . . . . . . . . . . . . . . . . . 30
Getting Started with ENVI
ENVI File Naming Conventions . . . . . . . . 31
ENVI Supported Input File Formats . . . . . 33
ENVI Supported Output File Formats . . . . 35
25
26
Chapter 2: Before You Begin
Starting and Exiting ENVI
Before starting ENVI, ensure that it is properly installed, as described in the
Installation and Licensing Guide. The Installation and Licensing Guide also provides
steps to start ENVI on Windows, UNIX, and Macintosh.
Using Startup Scripts
Use startup scripts in ENVI to automatically open image files, to load bands into
displays, to open vector files, and to open region of interest (ROI) files. You can
configure your ENVI preferences to run a script at ENVI startup, or you can run a
script manually from the ENVI main menu bar. The format for the startup script is
described below.
To configure your ENVI preferences to run a startup script each time you start ENVI,
see User-Defined File Preference Settings in the ENVI User’s Guide.
To run a startup script manually:
1. From the ENVI main menu bar, select File → Execute Startup Script. The
Input Script Filename dialog appears.
2. Select the startup script filename.
3. Click Open.
Startup Script Format
Create a startup script using a text editor and name the file using the extension .ini.
The available startup commands and their formats are as follows:
Action
Command Syntax
Open an image file
open file = filename
Load a gray scale image
into a new display group
load band = band_number
The band number refers to the file opened in the line
above the load band command.
Table 2-1: Startup Script Command Syntax
Starting and Exiting ENVI
Getting Started with ENVI
Chapter 2: Before You Begin
27
Action
Command Syntax
Load an RGB color
load bands = R_band_number, G_band_number,
image into a new display B_band_number
The band numbers refer to the file opened in the line
above the load band command.
Open an ENVI vector
file (.evf)
open evf = evf_filename
Open an ROI file
open roi = roi_filename
Open a saved display
group
open display group = display_group_filename
Table 2-1: Startup Script Command Syntax (Continued)
Example Startup Script
open
load
open
load
open
file = e:\data\canyon\canyon.tm
bands = 4,3,2
file = e:\data\canyon.tif
band = 1
roi = e:\data\canyon\canyon.roi
Saving a Session to a Script
Use Save Session to Script to save currently open image files and their bands, and
display groups to an ENVI startup script. To execute this startup file, see “Using
Startup Scripts” on page 26.
Note
The Save Session to Script option only works for files that you can open through
the ENVI main menu bar option File → Open Image File (see “Opening Image
Files in ENVI” on page 82).
1. From the ENVI main menu bar, select File → Save Session to Script. The
Output ENVI Script Filename dialog appears.
2. Enter the startup filename (typically with the extension .ini).
Getting Started with ENVI
Starting and Exiting ENVI
28
Chapter 2: Before You Begin
Exiting ENVI
1. Save any open files or in-memory items you wish to keep.
2. From the ENVI main menu bar, select File → Exit. ENVI closes all open files
and in-memory items and exits.
Starting and Exiting ENVI
Getting Started with ENVI
Chapter 2: Before You Begin
29
ENVI Image Files
ENVI uses a general raster data format consisting of a simple flat binary file and a
small associated ASCII (text) header file. This enables ENVI’s flexible use of nearly
any image format, including those with embedded header information. Because
ENVI uses ASCII header files that are built on-the-fly if required, you typically do
not need to convert your image file formats. ENVI supports MSS, TM, SPOT, ERS-1,
AVHRR, AVIRIS, GERIS, GEOSCAN, TIMS, digitized aerial photographs, DEM
data, AIRSAR, RADARSAT, and SIR-C data in their native formats (byte, signed and
unsigned integer, long integer, floating point, double precision, 64-bit integer,
unsigned 64-bit integer, complex, or double complex). The general raster data is
stored as a binary stream of bytes either in Band Sequential Format (BSQ), Band
Interleaved by Pixel Format (BIP), or Band Interleaved by Line Format (BIL)
formats.
BSQ
BSQ format is the simplest format, where each line of the data is followed
immediately by the next line in the same spectral band. This format is optimal for
spatial (x,y) access of any part of a single spectral band.
BIP
BIP format stores the first pixel for all bands in sequential order, followed by the
second pixel for all bands, followed by the third pixel for all bands, and so forth,
interleaved up to the number of pixels. This format provides optimum performance
for spectral (z) access of the image data.
BIL
BIL format stores the first line of the first band, followed by the first line of the
second band, followed by the first line of the third band, interleaved up to the number
of bands. Subsequent lines for each band are interleaved in similar fashion. This
format provides a compromise in performance between spatial and spectral
processing and is the recommended file format for most ENVI processing tasks.
Getting Started with ENVI
ENVI Image Files
30
Chapter 2: Before You Begin
ENVI Header Files
The ENVI header file is a separate text file that contains information ENVI uses to
read an image data file. It is typically created the first time ENVI accesses a data file.
The header file provides the following information:
•
The dimensions of the image
•
The imbedded header, if present
•
The data format
•
Other pertinent information
If the image file does not already have a header file, you enter the required header
information interactively (see “Creating Header Files” on page 123). You can also
edit the header file later (see “Editing Header Files” on page 127). If needed, you can
generate an ENVI header using a text editor (see “The ENVI Header Format” on
page 114).
ENVI Header Files
Getting Started with ENVI
Chapter 2: Before You Begin
31
ENVI File Naming Conventions
ENVI does not impose any constraints on filenames, with the exception of the use of
the.hdr extension used for header files. Some ENVI functions pre-load lists of files
with specific extensions for ease of use (see below). Use these extensions consistently
when running ENVI to maximize file handling efficiency. (This does not preclude
you from using different filenames, if desired.)
File Type
Extension
ENVI bad lines list
.bll
ENVI Band Math or Spectral Math expression
.exp
ENVI calibration factors
.cff
ENVI contour levels file
.lev
ENVI density slice range file
.dsr
ENVI display group
.grp
ENVI filter kernels
.ker
ENVI GCP file
.pts
ENVI grid file
.grd
ENVI header file
.hdr
ENVI image
None defined
ENVI look up table
.lut
ENVI map key
.key
ENVI mosaic template file
.mos
ENVI n-D visualizer state
.ndv
ENVI PPI count file
.cnt
ENVI region of interest
.roi
ENVI spectral library
.sli
ENVI startup script
.ini
Table 2-2: ENVI File Types
Getting Started with ENVI
ENVI File Naming Conventions
32
Chapter 2: Before You Begin
File Type
Extension
ENVI statistics file
.sta
ENVI statistics report
.txt
ENVI surface view path file
.pat
ENVI tape script
.fmt
ENVI vector file
.evf
ENVI vector template file
.vec
JPL AIRSAR compressed stokes matrix radar data
.stk
SIR-C compressed data product
.cdp
Table 2-2: ENVI File Types (Continued)
Cross-Platform File Portability for Header Files
When naming files in ENVI, consider cross-platform portability. This is particularly
important for preserving the relationship between image files and their
corresponding header files.
On UNIX, ENVI appends the image filename with .hdr when creating a header file,
so a UNIX image file named image_1.img has a header file named
image_1.img.hdr. If two image files have the same name but different extensions
(for example, .img and .dat), the corresponding header filenames are
image_1.img.hdr and image_1.dat.hdr.
On Windows, ENVI replaces the image file extension with .hdr when creating a
header file, so a Windows image file named image_1.img has a header file named
image_1.hdr. If there are two image files with the same name but different
extensions (for example, .img and .dat), the files would have the same header
filename of image_1.hdr. This could cause problems in ENVI if the two images are
located in the same directory and have different sizes and characteristics.
If cross-platform portability of images is an issue, the easiest solution is not to name
image files with an extension. As a result, an image file has the same header filename
in both UNIX and Windows. Alternatively, you can rename images and header files
to the Windows convention before moving the images from UNIX to Windows
systems.
ENVI File Naming Conventions
Getting Started with ENVI
Chapter 2: Before You Begin
33
ENVI Supported Input File Formats
•
ALOS Formats: PRISM, AVNIR-2, PALSAR
•
AVHRR Formats: KLMN/Level 1b, Quorum, SHARP
•
ENVISAT Formats: AATSR, ASAR, MERIS
•
EOS Formats: ASTER, MODIS
•
EROS A Formats: Level 1A, Level 1B (GeoTIFF)
•
Flat Binary Formats: BSQ, BIL, BIP
•
FORMOSAT-2
•
Generic Formats: ASCII, HDF, JPEG, JPEG2000, MrSID, PDS, PICT, PNG,
SRF, TIFF/GeoTIFF1, GeoTIFF with metadata (.txt and .met), TIFF world
files (.tfw), XWD
•
GeoEye-1 Formats: GeoTIFF, NITF
•
IKONOS Formats: GeoTIFF, NITF
•
Image Processing Software Formats: ArcView® Raster (.bil), ECW,
ERDAS IMAGINE, ER Mapper, ESRI® GRID, PCI (.pix)
•
IRS Formats: Fast, SuperStructured
•
KOMPSAT-2 Formats: GeoTIFF
•
Landsat Formats: ACRES CCRS, ESA CEOS, FAST, GeoTIFF, HDF,
MRLC, NLAPS
•
Military Formats: ADRG, CADRG, CIB, NITF, miscellaneous formats,
ATSR, DMSP (NOAA), LAS LIDAR, OrbView files, GeoTIFF, NITF
•
QuickBird Formats: GeoTIFF, NITF, QuickBird Tile Products (.til)
•
Radar Formats: AIRSAR, ASAR, COSMO-SkyMed, ERS, JERS,
RADARSAT, TOPSAR
•
RapidEye: GeoTIFF, NITF
•
SeaWIFS Formats: CEOS, HDF
•
SPOT Formats: ACRES SPOT, DIMAP, GEOSPOT, SPOT, Vegetation
1. ENVI supports the following input TIFF compression formats CCITT Group 3 and 4 algorithms, Macintosh PackBits algorithm, ThunderScan 4-bit RLE algorithm, NeXT 2-bit RLE
algorithm, and LogLuv high dynamic range encoding.
Getting Started with ENVI
ENVI Supported Input File Formats
34
Chapter 2: Before You Begin
•
TFRD: (You must purchase a separate module through ITT Visual Information
Solutions.)
•
Thermal Formats: AATSR, ASTER, MASTER, TIMS
•
USGS and Digital Elevation Formats: USGS DRG, USGS DOQ, USGS
DEM, SDTS DEM, DTED, SRTM DEM
•
Vector Formats: ArcInfo® interchange format, shapefile, DXF, ENVI vector
file (.evf), MapInfo Interchange, Microstation DGN, USGS DLG, USGS
DLG in SDTS format
•
WorldView Formats: GeoTIFF, NITF, WorldView Tile Products (.til)
ENVI Supported Input File Formats
Getting Started with ENVI
Chapter 2: Before You Begin
35
ENVI Supported Output File Formats
•
ENVI Flat Binary Formats: BIL, BIP, BSQ
•
Generic Image Formats: ASCII, BMP, HDF, JPEG, JPEG 2000, PICT, PNG,
TIFF (GeoTIFF), TIFF world (.tfw), SRF, XWD
•
Image Processing Formats: ArcView® raster (.bil), ER Mapper, ERDAS
IMAGINE, ESRI® GRID, NITF 02.00/02.10, PCI (.pix)
•
Vector Formats: shapefile, DXF, ENVI vector file (.evf)
Getting Started with ENVI
ENVI Supported Output File Formats
36
ENVI Supported Output File Formats
Chapter 2: Before You Begin
Getting Started with ENVI
Chapter 3
The ENVI Interface
This chapter provides instructions about the ENVI interface components. It includes:
The ENVI Main Menu Bar . . . . . . . . . . . . .
The Available Bands List . . . . . . . . . . . . . . .
Display Groups . . . . . . . . . . . . . . . . . . . . . .
The Available Vectors List . . . . . . . . . . . . . .
Getting Started with ENVI
38
39
46
61
The Remote Connection Manager . . . . . . .
Vector Displays . . . . . . . . . . . . . . . . . . . . .
Plot Windows . . . . . . . . . . . . . . . . . . . . . . .
ENVI Mouse Buttons . . . . . . . . . . . . . . . . .
67
68
73
75
37
38
Chapter 3: The ENVI Interface
The ENVI Main Menu Bar
When you start ENVI, the ENVI main menu bar appears. You initiate activities in
ENVI by using the menus in the ENVI main menu bar, which may be oriented
horizontally or vertically, as shown below. See Miscellaneous Preference Settings in
the ENVI User’s Guide for details on how to orient your ENVI main menu bar.
Figure 3-1: ENVI Main Menu Bar Oriented Horizontally (left) and Vertically (right)
The ENVI Main Menu Bar
Getting Started with ENVI
Chapter 3: The ENVI Interface
39
The Available Bands List
When you open a file for the first time during a session, ENVI automatically places
the filename, with all of its associated bands listed beneath it, into the Available
Bands List. If a file contains map information as well, a map icon appears under the
filename.
ENVI also adds output files to the Available Bands List that are the results of
processing your data using ENVI’s tools.
File
File bands
File map information
Figure 3-2: Available Bands List
If you open multiple files, all of the files with all of their bands appear in the
Available Bands List sequentially, with the most recently opened file at the top of the
list. You can fold the bands displayed under each filename to shorten the list length
(see “Folding and Unfolding Data Sets” on page 40).
Getting Started with ENVI
The Available Bands List
40
Chapter 3: The ENVI Interface
Folding and Unfolding Data Sets
By default, data sets typically display in ENVI in an unfolded state, where a file and
all of its bands are immediately visible in the list. In the Available Bands List and
other band selection dialogs, many bands may be listed, particularly when using
hyperspectral data. You can fold or hide all of the bands of a data set so that they
appear on only one line. This keeps the lists shorter and easier to work with.
Unfolded data set
Folded data sets
Figure 3-3: Folded and Unfolded Data sets
To fold a data set, either:
•
Click on the minus symbol (–) next to the filename.
•
Double-click on the filename of the data set.
•
To fold all data sets in the Available Bands List, right-click in the Select Input
Band field and select Fold All Files, or from the Available Bands List menu
bar, select Options → Fold All Files.
All of the bands of the data set compress and the data set appears with the plus
symbol (+) next to the filename, as illustrated in the example in Figure 3-3.
To unfold a data set, either:
•
Click on the plus symbol (+) next to the filename.
•
Double-click on the filename.
•
To unfold all data sets in the Available Bands List, right-click in the Select
Input Band field and select Unfold All Files.
The Available Bands List
Getting Started with ENVI
Chapter 3: The ENVI Interface
41
All of the bands of the data set expand and the data set appears with the minus
symbol (–) next to the filename, as illustrated in the example in Figure 3-3.
If a band is currently displayed as either a gray scale or RGB image, an asterisk ( * )
appears next to the filename when it is folded.
Opening Files from the Available Bands List
1. From the Available Bands List menu bar, select File → Open Image File. The
Enter Data Filename dialog appears.
2. Select a filename.
3. Click Open. ENVI adds the new file to the top of the Available Bands List.
Tip
To display a list of all open files, from the Available Bands List, select File →
Available Files List.
For additional ways to open image files in ENVI, see “Opening and Displaying Files”
on page 81.
Opening Files in ArcMap
To open a file in ArcMap™ software, you must have ArcMap version 9.2 or higher
installed and licensed on your system.
1. Right-click on a dataset in the Available Bands List, and select Open File in
ArcMap.
Note
If you opened the dataset in a display group and added any image
enhancements or annotations, those will not be retained when you open the
image in ArcMap software. If you want to retain image enhancements or
annotations, use File → Export Image to ArcMap from the display group
menu bar.
2. If you have one or more instances of ArcMap software already running, an
ArcMap Instances dialog appears. Select an instance to display your dataset, or
start a new instance of ArcMap software. Click OK.
If ArcMap software is not already running, ENVI will initiate it for you. The
dataset will display in ArcMap software with ArcMap software’s default
Getting Started with ENVI
The Available Bands List
42
Chapter 3: The ENVI Interface
enhancements and will be added as a new layer to the ArcMap table of
contents.
Raster datasets in GeoTIFF, MrSID, ERDAS IMAGINE, or NITF format, or those
stored in a geodatabase, can pass directly into ArcMap software without any
conversion. For all other formats, ENVI converts the datasets to GeoTIFF format
before passing them to ArcMap software. These are stored in the location you specify
as the Temp Directory. (See Default Directory Preference Settings in the ENVI
User’s Guide.) Datasets exported to ArcMap software remain open in ENVI.
Opening Files in ENVI Zoom
From ENVI, you can open a file in ENVI Zoom from the Available Bands List. The
file must be in a format supported by ENVI Zoom, and it must be a saved file; you
cannot open in-memory files.
In the Available Bands List, right-click on the file to open and select Open in ENVI
Zoom. The file is opened in ENVI Zoom, and is optionally displayed in the Image
window depending on your Auto Display Files On Open preference setting. For
details about using ENVI Zoom, see the ENVI Zoom User’s Guide.
Closing Files from the Available Bands List
You can close individual files or all open files from the Available Bands List.
Closing Selected Files
To close the file associated with the bands currently displayed in the Selected Band
field or in the R, G, and B fields:
•
From the Available Bands List menu bar, select File → Close Selected File.
•
In the Available Bands List, right-click on the file to close and select Close
Selected File.
Tip
If you close one band from a disk file, ENVI closes the entire file and all of the
bands in the file disappear from the Available Bands List. However, the file still
exists on disk, and you can reopen it using File → Open Image File.
The Available Bands List
Getting Started with ENVI
Chapter 3: The ENVI Interface
43
Closing All Files
To close all files in the Available Bands List and delete any items in memory:
1. From the Available Bands List menu bar, select File → Close All Files. A
warning dialog appears.
Note
When you delete an in-memory file, you cannot recover the image.
2. Click Yes to close all files.
Hiding and Showing the Available Bands List
To remove the Available Bands List from view while keeping open the image files it
contains, select File → Cancel from the Available Bands List menu bar.
To recall the Available Bands List at any time, select Window → Available Bands
List from the ENVI main menu bar.
Getting Started with ENVI
The Available Bands List
44
Chapter 3: The ENVI Interface
Available Bands List Right-Click Menus
The Available Bands List has a right-click menu for easy access to common Available
Bands List functions.
Right-click on any filename, band name, or map information icon. The right-click
menu items differ depending upon which item you right-click.
Figure 3-4: Available Bands List Right-click Menus for File (left), Band (center),
and Map Information (right)
Editing Map Information
If a file has map information associated with it, you can view or edit this information.
To view or edit the map information associated with a file, right-click on the Map
Info icon in the Available Bands List and select Edit Map Information. For
information on using the Edit Map Information dialog to edit the data, see Editing
ENVI Headers in the ENVI User’s Guide.
The Available Bands List
Getting Started with ENVI
Chapter 3: The ENVI Interface
45
Locating Bands by Wavelength
For files with associated wavelength values in the header file, use Wavelength
Locator to locate the band that contains a specified wavelength.
To use the wavelength locator:
1. From the Available Bands List, select Options → Wavelength Locator. The
Wavelength Locator dialog appears.
2. Enter the wavelength you want to locate.
3. Click Apply. ENVI highlights the band containing that wavelength in the
Available Bands List.
Showing Displayed Band Information
To display the names and wavelengths of the bands being used in a display group:
1. In the Available Bands List, select the display from the Display #n button.
2. From the Available Bands List menu bar, select Options → Show Current
Displayed Bands.
The band information appears in the R, G, and B, or Selected Band (for gray scale)
fields.
Getting Started with ENVI
The Available Bands List
46
Chapter 3: The ENVI Interface
Display Groups
When you select a file to display from the Available Bands List (see “Displaying
Images” on page 107), a group of windows will appear on your screen allowing you
to manipulate and analyze your image. This group of windows is collectively referred
to as the display group. The default display group consists of the following:
•
Image window: Displays the image at full resolution. If the image is large, the
Image window displays the subsection of the image defined by the Scroll
window Image box.
•
Zoom window: Displays the subsection of the image defined by the Image
window Zoom box. The resolution is at a user-defined zoom factor based on
pixel replication or interpolation.
•
Scroll window: Displays the full image at subsampled resolution. This window
appears only when an image is larger than what ENVI can display in the Image
window at full resolution.
ENVI displays all images with a default 2% linear stretch. You can change the
Display Default Stretch preference setting or set a default stretch in the image
header file (see Editing ENVI Headers in the ENVI User’s Guide).
You can have multiple display groups open at a time, with any combination of gray
scale and color images on display.
The windows included in the default display group and the general appearance of the
display group windows are controlled by the ENVI Display Default Preference
Settings defined for all ENVI sessions. You can also set preferences for an individual
display group for a single session (see Editing ENVI Headers in the ENVI User’s
Guide).
Mouse button functions for each of the display group windows differ. See “ENVI
Mouse Buttons” on page 75 for details on mouse button behavior for each window.
Display Groups
Getting Started with ENVI
Chapter 3: The ENVI Interface
47
Display number
Display group
menu bar
Image window
(area from Image
box, below)
Zoom
box
Zoom factor
Resampling
factor
Image
box
Zoom
window
(area from
Zoom box,
above)
Scroll window
(area displayed in
Image window)
Zoom controls
Figure 3-5: Display Group
Getting Started with ENVI
Display Groups
48
Chapter 3: The ENVI Interface
Reduced Resolution Data Sets
Some remote sensing images include Reduced Resolution Data Set (RRDS) files to
speed the display of the imagery. RRDS files (also called RSETs) are versions of the
original image at various reduced resolutions.
ENVI currently supports RRDS files generated by RemoteView software, with file
extensions of .rv1 through .rvn. Each progressive number represents a spatial
resampling twice that of the previous file. They are in NITF 2.1 uncompressed
format, so you must have a NITF/NSIF Module license in order for ENVI to use them
to display images.
ENVI uses the RRDS files to display imagery in the Scroll window when you zoom
in or out of the display, only as the Scroll window allows.
Opening New Display Groups
To start a new display group, use one of the following:
•
From the Display group menu bar, select Window → Start New Display
Window.
•
From the ENVI main menu bar, select Window → Start New Display
Window.
•
In the Available Bands List, click Display #n and select New Display.
An empty Image window appears. Each window started is numbered sequentially
starting with Display #1. When you load an image into the empty Image window, the
Zoom and Scroll windows associated with that image appear.
Resizing Display Group Windows
To change the size of any display group window, either:
•
Dynamically resize the window up to the available screen size by clicking and
grabbing one of the corners and dragging to the desired size.
If you are resizing the Zoom window, the corresponding Zoom box in the
Image window automatically changes its size and shape to match the resized
Zoom window.
If you are resizing the Scroll window, the resampling factor changes to reflect
the new size of the Scroll window.
Display Groups
Getting Started with ENVI
Chapter 3: The ENVI Interface
49
•
From the Display group menu bar, select File → Preferences and enter the size
in the Display Preferences dialog (see “Setting Preferences for an Individual
Display Group” on page 58).
•
Change the default window size parameters set in your ENVI preferences (see
Display Default Preference Settings in the ENVI User’s Guide).
Maximizing Open Displays
To resize all display group windows to fit the available screen space, use one of the
following:
•
From the Display group menu bar, select Window → Maximize Open
Displays.
•
From the ENVI main menu bar, select Window → Maximize Open Displays.
For example, if four displays are open, each display is resized to fill one-fourth of the
available screen.
Positioning the Zoom and Scroll Windows
You can control the positioning of the Zoom and Scroll windows as follows:
•
To position the Zoom and Scroll windows with respect to the Image window,
select Scroll/Zoom Position from the display group right-click menu.
•
To position the Zoom or Scroll window, left-click and drag the title bar to the
desired position.
•
To group the Zoom and Scroll windows to move with the Image window,
deselect the Scroll/Zoom Position → Auto Placement Off option in the
display group right-click menu.
•
To ungroup the window, select Scroll/Zoom Position → Auto Placement Off
in the right-click menu.
•
To ensure that windows remain where they are placed, select Scroll/Zoom
Position → Auto Placement Off. The windows remain in place until you move
them again.
Displaying Scroll Bars
Use scroll bars in the Image and/or Zoom windows to move around the image. When
you move the scroll bars in the Image window, the Image box in the Scroll window
moves to show what part of the whole image you are in. Likewise, when you move
Getting Started with ENVI
Display Groups
50
Chapter 3: The ENVI Interface
the scroll bars in the Zoom window, the Zoom box in the Image window moves to
show the zoom area.
To display scroll bars, use one of the following:
•
In either the Image window or Zoom window, right-click and select Toggle →
Display Scroll Bars.
•
From the Display group menu bar, select File → Preferences. The Display
Preferences dialog appears, where you can change the default settings for the
display group (see “Setting Preferences for an Individual Display Group” on
page 58).
•
From the ENVI main menu bar, select File → Preferences. The System
Preferences dialog appears, where you can change the default settings for all
ENVI display groups (see Display Default Preference Settings in the ENVI
User’s Guide).
Hiding and Unhiding Display Group Windows
To hide only the Zoom and/or Scroll windows on Microsoft Windows platforms,
button in the upper-right corner of the window.
click the
To unhide the Zoom and/or Scroll windows, right-click in the associated Image
window and click <Find Display> to bring up the hidden windows. You can also
unhide display group windows by using the Window Finder (see “Using the Window
Finder” on page 56).
Display Group Right-Click Menus
The display group has several right-click menus for access to many options. The
right-click menus provide secondary access to functions that are otherwise accessible
from the ENVI main menu bar or the Display group menu bar. In some cases, the
right-click menu may be the only means to access an option.
Display Groups
Getting Started with ENVI
Chapter 3: The ENVI Interface
51
The right-click menu differs, depending on which of the display group windows you
right-click in, and depending on the tools you are using (for example, if interactive
linking is on or off).
Figure 3-6: Right-Click Menus for Image Window (left) and Zoom Window (right)
When you select from the right-click menu, the function applies only to the active
display group.
For example, you can use the right-click menu in any of the three display group
windows to quickly access display group options:
1. Right-click anywhere in any of the three display group windows.
2. Select from the following options:
•
Use Display Window Style to select which of the three display windows
(Image, Scroll, and Zoom) to show.
•
Use Scroll/Zoom Position to place the Scroll and Zoom windows in the
desired position with respect to the Image window and to turn the Auto
Placement option off or on.
•
Use <Find Display> to locate the closed display group windows
associated with the current display group window.
Getting Started with ENVI
Display Groups
52
Chapter 3: The ENVI Interface
Controlling the Zoom Window
The Zoom window provides you with unlimited zoom capabilities, such as zooming
in or out and panning.
See also “Zoom Window Mouse Button Functions” on page 76 for details about
using mouse buttons in the Zoom window.
Controlling the Zoom Window from the Image Window
The Zoom box in the Image window outlines the area that displays in the associated
Zoom window.
To change the region defined by the Zoom box:
•
Click and drag the Zoom box around in the Image window.
•
Use the arrow keys on the keyboard to move the Zoom box in the Image
window by one pixel in the direction of the arrow.
•
Use Shift + arrow keys to move the Zoom box in the Image window by five
pixels in the direction of the arrow.
•
Use scroll bars (see “Displaying Scroll Bars” on page 49).
Scrolling the Zoom Window
To scroll the Zoom window, use one of the following:
Display Groups
•
Use the arrow keys on the keyboard to move the Zoom window by one pixel in
the direction of the arrow.
•
Use Shift + arrow keys to move the Zoom window by 10 pixels in the direction
of the arrow.
•
Use scroll bars (see “Displaying Scroll Bars” on page 49).
Getting Started with ENVI
Chapter 3: The ENVI Interface
53
Controlling the Zoom Factor and Crosshairs
The current zoom factor displays as a number in brackets in the Zoom window title
bar. The default zoom factor is 4.
Zoom Out
Zoom In
Enable/Disable Crosshairs
Figure 3-7: ENVI Zoom Window with Zoom Controls
Getting Started with ENVI
Display Groups
54
Chapter 3: The ENVI Interface
Use the different mouse buttons and the Zoom controls in the Zoom window to
change the zoom factor and to turn the display crosshairs on and off in both the Zoom
and Image windows. The following describes the Zoom controls and their associated
mouse button functions.
Zoom Window
Control
Zoom In
Function
Left-click to increase the zoom factor by 1.
Middle-click to double the zoom factor with each click
(such as, 2, 4, 8, 16).
Right-click to return to the default zoom factor of 4.
Zoom Out
Left-click to decrease the zoom factor by 1.
Middle-click to decrease the zoom factor by half.
Right-click to return to the default zoom factor of 4.
Crosshairs
Left-click to toggle crosshairs in the Zoom window on and
off.
Middle-click to toggle crosshairs in the Image window on
and off.
Right-click to toggle the Zoom box and crosshairs in the
Image window on and off.
Table 3-1: Zoom Window Control Functions with Mouse Button Descriptions
You can also zoom in by a factor of 1 and enable/disable crosshairs using options
from the Zoom window right-click menu:
•
To zoom in by a factor of 1, right-click and select Set Zoom Factor to 1.
•
To toggle crosshairs on/off, right-click and select Toggle → Zoom Cross-hair.
Controlling Zoom Interpolation
You can set your preference for the type of interpolation to use in the Zoom window.
The choices are:
Display Groups
•
Nearest Neighbor: Interpolation using pixel replication (default)
•
Bilinear: Linear interpolation using 4 pixels
•
Bicubic: Interpolation using 16 pixels
Getting Started with ENVI
Chapter 3: The ENVI Interface
•
55
Optimized Bicubic: Best interpolation
To set the interpolation, either:
•
In the Zoom window, right-click and select Zoom Interpolation, then select
the interpolation method.
•
From the Display group menu bar, select File → Preferences (see “Setting
Preferences for an Individual Display Group” on page 58).
•
From the ENVI main menu bar, select File → Preferences (see Display
Default Preference Settings in the ENVI User’s Guide).
Controlling the Scroll Window
The Image box in the Scroll window appears as an outlined area and represents the
area that displays in full resolution in the Image window.
Controlling the Image Window from the Scroll Window
The size of the Image box in the Scroll window is affected by the size of the Image
window.
•
If you change the size of the Image window, the Scroll window Image box also
changes sizes.
•
If the display window style is set to Scroll/Image/Zoom and you resize the
Image window so that the entire image appears at full resolution, the Scroll
window is no longer needed and closes.
•
If you resize the Image window so that the full image cannot be shown at full
resolution, the Scroll window reopens.
•
The Image box in the Scroll window outlines the area that displays in the
associated Image window. To change the region defined by the Image box,
click and drag the Image box around in the Scroll window.
•
Use the arrow keys on the keyboard to move the Image box in the Scroll
window by one pixel in the direction of the arrow. The Image window updates
to show the new area.
•
Use Shift + arrow keys to move the Image box in the Scroll window by five
pixels in the direction of the arrow. The Image window updates to show the
new area.
See also “Scroll Window Mouse Button Functions” on page 77 for details about
using mouse buttons in the Scroll window.
Getting Started with ENVI
Display Groups
56
Chapter 3: The ENVI Interface
Scroll Window Meta Zoom
When very large images display, ENVI may subsample the Scroll window image to
the extent that it is difficult to see image features. When this occurs, use the Scroll
window meta zoom capability to zoom into an area and reduce the subsampling
factor in the Scroll window.
To enable or disable meta zoom:
•
To enable meta zoom, middle-click and drag the Meta Zoom box around the
desired area in the Scroll window. The selected area must be larger than the
current Image window size. The meta zoomed area replaces the full image in
the Scroll window and scroll bars appear.
•
To re-display to the original Scroll window, right-click in the Scroll window
and select Reset Scroll Range.
Using the Window Finder
Use the Window Finder to manage active ENVI windows and dialogs and to bring
windows that are minimized or buried under other windows to the foreground. The
list contains the names of major active windows in the order that they were opened.
The list includes display group windows (Image, Scroll, Zoom), plot windows,
scatter plots, ROI definition windows, and so forth.
1. From the ENVI main menu bar, select Window → Window Finder. The
ENVI Window Finder appears with a list of open windows.
Figure 3-8: Window Finder Dialog
Display Groups
Getting Started with ENVI
Chapter 3: The ENVI Interface
57
2. To call a window to the desktop foreground:
•
Click on the name of a specific display number to bring the Image window
and its associated Scroll and Zoom windows to the front.
•
Click on any other window name to bring that window to the front.
•
If you click on the name of an overlay dialog (Annotation, ROI, Density
Slice, etc.) that was hidden by selecting Overlay → Hide Layer in the
dialog menu bar, double-click the dialog name to hide the dialog again.
For details about hiding dialogs, (see Showing and Hiding Overlay
Dialogs and Layers in the ENVI User’s Guide).
Tip
The ENVI Window Finder moves to the front of the display group if bringing an
ENVI window forward causes it to be covered. If the Window Finder is hidden
behind another window, select Window → Window Finder from the ENVI main
menu bar to bring it to the front again.
Saving Display Groups
You can save a given display group in its present state to a file. When you save a
display group, the displayed bands, window sizes and positions, stretch, any
displayed overlays, any open profiles, any associated two-dimensional scatter plots,
and any display preference settings are saved along with the display in a text file.
Files that are not saved to disk (for example, only in memory) and files that cannot be
opened directly using ENVI’s Open Image File function are not saved with the
display group.
1. From the Display group menu bar, select File → Save As Display Group.
2. Enter an output filename.
3. Click OK. ENVI automatically appends the extension .grp to the filename.
Restoring Saved Display Groups
1. Use one of the following:
•
From the ENVI main menu bar, select File → Restore Display Group.
•
From the Display group menu bar, select File → Restore Display Group.
2. In the Input File dialog, select the .grp file.
Getting Started with ENVI
Display Groups
58
Chapter 3: The ENVI Interface
3. Click OK. If you selected to restore the display group from the ENVI main
menu bar, the display loads into a new display group. If you selected to restore
the display group from the Display group menu bar, the display loads into the
current display group.
Setting Preferences for an Individual Display Group
For each display group you can set preferences that distinguish that display from
other displays. For example, you can add virtual borders to an image, enable scroll
bars, change the size of the Image, Zoom, or Scroll windows, and change the graphics
display colors in those windows. These settings are in effect for only the current
ENVI session, unless you save the display group to restore in a later ENVI session
(see “Saving Display Groups” on page 57 and “Restoring Saved Display Groups” on
page 57).
Display Groups
Getting Started with ENVI
Chapter 3: The ENVI Interface
59
If you prefer to change preferences for all display groups and use the same
preferences for all, see Display Default Preference Settings in the ENVI User’s
Guide.
Figure 3-9: Display Preference Dialog
To set preferences for an individual display group:
1. From the Display group menu bar, select File → Preferences. The Display
Preferences dialog appears. For complete descriptions of the dialog options,
see Display Default Preference Settings in the ENVI User’s Guide.
2. Select the combination of the display group windows to use from the Window
Style drop-down list.
Getting Started with ENVI
Display Groups
60
Chapter 3: The ENVI Interface
3. To have a virtual border around the edge of the display group windows when
an image is loaded, set the width (in pixels) in the Display Border fields. The
left field controls the left border, the top field controls the top border, and so
forth. Click Border Color to select the virtual border color.
4. In the Image Window fields, enter the Xsize and Ysize in pixels, and specify
whether or not to include Scroll Bars.
5. In the Zoom Window fields, enter the Xsize and Ysize in pixels, specify
whether or not to include Scroll Bars, and set the Zoom factor and
Interpolation method.
6. In the Scroll Window fields, enter the Xsize and Ysize in pixels.
7. Click the Display Graphic Color color button to set the color of the Zoom
box, Image box, and Zoom controls.
8. Click OK.
Closing Display Groups
To close a display group, use one of the following:
•
From the Display group menu bar, select File → Cancel.
•
In Microsoft Windows, click the
button in the Image window.
The display group and any associated dialogs close.
To save a display group and its associated windows to a file, see “Saving Display
Groups” on page 57.
Closing All Open Display Groups
To close all open display groups, use one of the following:
Display Groups
•
From the Display group menu bar, select Window → Close All Display
Windows.
•
From the ENVI main menu bar, select Window → Close All Display
Windows.
Getting Started with ENVI
Chapter 3: The ENVI Interface
61
The Available Vectors List
When you load a vector file into memory for the first time during an ENVI session,
ENVI automatically places the vector layers into the Available Vectors List. Data
files that can appear in the Available Vectors List include ENVI vector files, DLG,
Microstation DGN, MapInfo, SDTS, DXF, ArcInfo® Interchange, and shapefiles.
Figure 3-10: Available Vectors List
If you open multiple vector files, all of the files appear in the Available Vectors List
sequentially, with the most recently opened file at the bottom of the list.
From the Available Vectors List, you can select vector files to display as an overlay in
a display group, or in a separate Vector window (see “Displaying Vectors” on
page 112).
Getting Started with ENVI
The Available Vectors List
62
Chapter 3: The ENVI Interface
Opening Files from the Available Vectors List
1. In the Available Vectors List, select File → Open Vector File. The Select
Vector Filenames dialog appears.
2. Select the file type from the Files of type drop-down list.
3. Select the filename.
4. Click Open. ENVI adds the vector file to the Available Vectors List.
For additional ways to open vector files in ENVI, see “Opening Vector Files” on
page 103.
Opening Vector Layers in ENVI Zoom
From ENVI, you can open one or more vector files in ENVI Zoom from the
Available Vectors List. The file must be a saved file; you cannot open in-memory
files. All vector files, including .shp files, open as .evf.
1. Select the file(s) to open.
2. From the Available Vectors List menu bar, select File → Open Layers in
ENVI Zoom. The vector layer(s) are opened in ENVI Zoom, and are
optionally displayed in the Image window depending on your ENVI Zoom
Auto Display Files On Open preference setting. For details about using ENVI
Zoom, see the ENVI Zoom User’s Guide.
Opening Vector Layers in ArcMap
To open data in ArcMap™ software, you must have ArcMap version 9.2 or higher
installed and licensed on your system. At least one vector dataset must be open.
1. Select one or more vector datasets from the Available Vectors List to display
in ArcMap software.
2. From the Available Vectors List menu bar, select File → Open Layers in
ArcMap.
3. If you have one or more instances of ArcMap software already running, an
ArcMap Instances dialog appears. Select an instance to display your dataset, or
start a new instance of ArcMap software.
4. Click OK.
The Available Vectors List
Getting Started with ENVI
Chapter 3: The ENVI Interface
63
If ArcMap software is not already running, ENVI will initiate it for you. The
vector datasets will display in ArcMap software and will be added to the
ArcMap table of contents.
Vector datasets must be in shapefile format or consist of feature classes in a
geodatabase. You cannot export vector data to ArcMap software that have unsaved
edits. You must first commit your edits or revert back to the original vectors before
exporting them to ArcMap software.
Datasets exported to ArcMap software remain open in ENVI.
Opening New Vector Windows
To start a new empty Vector window and an associated parameters dialog, select
Options → Start New Vector Window.
Editing Layer Names
1. In the Available Vectors List, select Options → Edit Layer Names.
2. When the Edit Layer Names dialog appears, click on the name of the layer that
you want to change. The name appears in the Edit Selected Item field.
3. Edit the name. To return the layer to its unedited name, click Reset.
4. Click OK.
Creating New Layers
Use Create New Vector Layer to create a new empty vector layer so you can add
polygons, lines, or points and attributes. These vector layers can have the same
projection and geographic boundaries (size) as existing vector layers, georeferenced
raster images, or you can base them on user-defined input. An empty vector layer can
also be created from non-georeferenced raster images for drawing vectors over those
images. For detailed instruction on creating new layers from existing layers,
projection and boundaries of a raster image, or from user-defined parameters, see
ENVI Help.
Tip
You can also create vector layers by selecting Vector → Create New Vector
Layer from the ENVI main menu (see Creating Vector Layers in the ENVI User’s
Guide).
Getting Started with ENVI
The Available Vectors List
64
Chapter 3: The ENVI Interface
Saving Vector Layers
Vector layers listed in the Available Vectors List are currently in memory. Use this
procedure to save them to a file.
1. In the Available Vectors List, select the layer by clicking on the name.
2. Select File → Save Memory Layers to File.
3. Enter an output filename.
Selecting an Output Geodatabase
You can save raster and vector datasets that are open in ENVI or ENVI Zoom to a
geodatabase. Follow these steps to continue:
1. Select one of the following menu options, depending on the program you are
using:
•
Raster datasets in ENVI:
From the ENVI main menu bar, select File → Save File As → ArcGIS
Geodatabase.
•
Vector datasets in ENVI:
In the Available Vectors List, select a vector layer by clicking on the
name. Select File → Export Layers to ArcGIS Geodatabase.
•
Raster and vector datasets in ENVI Zoom:
From the ENVI Zoom menu bar, select File → Save to ArcGIS
Geodatabase.
If you are saving raster datasets in ENVI or raster/vector datasets in ENVI
Zoom, the Select Input File dialog appears.
2. Select a dataset, and click OK.
The Process Manager updates to show export progress to a geodatabase. The
Process Manager displays the progress, but the coordination between ENVI or
ENVI Zoom and ArcMap™ software does not allow the process to be cancelled
once initiated.
The Select Output Geodatabase dialog appears. This dialog lists all available
geodatabases to which ENVI or ENVI Zoom is connected.
3. If the destination geodatabase is not present in this list, click Connect. The
Connection Properties dialog appears. See “Managing Connection Properties”
on page 96 for instructions on connecting to a dataset. If successful, the new
The Available Vectors List
Getting Started with ENVI
Chapter 3: The ENVI Interface
65
connection is added to the Destination Geodatabase list and selected by
default.
4. Select a geodatabase from the Destination Geodatabase list.
5. In the Select Output Geodatabase dialog, enter a dataset name in the Output
Name field. The default is the name of the input dataset.
6. Optionally set any configuration keywords. (For more information on
configuration keywords, see the ArcGIS Help.)
7. Click OK. ENVI or ENVI Zoom verifies that the output geodatabase has
sufficient write permissions and that you have a valid ArcGIS® license. (See
also ESRI License Type in ENVI Zoom preferences.)
Restrictions
•
You must have an ArcView® license to save to a personal or file geodatabase
and an ArcEditor™ or ArcInfo® license to save to an enterprise geodatabase.
Contact your ESRI sales representative to purchase a license.
•
Personal geodatabases store datasets within a Microsoft Access data file,
which is limited in size to 2 GB.
•
Enterprise geodatabases require a login. Users with read-only access cannot
save data to an enterprise geodatabase.
•
You cannot load vector data with unsaved edits to a geodatabase.
•
You can save point, line, polygon, and multipoint vector data to a geodatabase.
Vector files in ENVI Vector Format (EVF) with multiple record types are not
supported.
•
In ENVI, you cannot save virtual mosaics or spectral libraries to a
geodatabase.
•
In ENVI and ENVI Zoom, display enhancements you add to a raster image
(contrast stretching, sharpening, etc.) are not retained when saving the image
to a geodatabase. You can use the Chip from Display or Chip Display to
ArcMap option in ENVI Zoom, or the Save Image As option from an ENVI
display group, to retain display enhancements.
•
ENVI stores any single-band raster data with a three-color lookup table as an
RGB image upon saving to a geodatabase. ENVI Zoom retains color maps
upon saving to a geodatabase.
•
Traditional map information from input raster data will be retained upon
saving to a geodatabase. RPC information, affine map transformations (kx/ky
Getting Started with ENVI
The Available Vectors List
66
Chapter 3: The ENVI Interface
or pseudo projections), and custom projections are not retained when saving to
a geodatabase.
•
You cannot save a vector dataset (feature class) to an ArcGIS® feature dataset
from ENVI or ENVI Zoom. After saving a feature class to a geodatabase, use
ArcCatalog™ software to drag the feature class to a feature dataset if needed.
•
For NITF data, you can only save individual image segments to a geodatabase.
Composite images, annotation segments, and files with multiple image
segments are not supported. ENVI and ENVI Zoom do not export NITF
metadata to a geodatabase.
•
Metadata that is supported in both ENVI and ArcGIS software will transfer
upon saving to a geodatabase. However, ENVI-specific metadata (such as
spectral information, band names, etc.) will not be stored in a geodatabase.
•
Detailed information on geodatabase types, their structure, and their support in
ArcGIS software can be found in the ArcGIS Desktop help.
The Available Vectors List
Getting Started with ENVI
Chapter 3: The ENVI Interface
67
The Remote Connection Manager
See “Using the Remote Connection Manager” on page 91 for steps.
Getting Started with ENVI
The Remote Connection Manager
68
Chapter 3: The ENVI Interface
Vector Displays
ENVI Vector windows are standalone GIS plots that display vector data and allow
you to compose simple vector-only maps. You can also overlay vectors on display
groups, which includes true vectorization of overlays in all windows, including the
Zoom window. ENVI maintains full precision of vector data and avoids pixellation.
You can open vector files from a variety of input files, or you can create and draw
new vector layers in a Vector window or over images in a display group. In ENVI
Vector windows, you can also:
•
Display latitude/longitude and map coordinate information in the Vector
window status bar while interactively tracking vectors.
•
Display attribute information in real-time as the cursor tracks each vector (see
Vector Attributes in the ENVI User’s Guide).
•
Query vector GIS attribute information directly to generate new layers of
selected information with attributes (see Vector Attributes in the ENVI User’s
Guide).
•
Create shapefiles and associated .dbf attribute files and indexes, or DXF files
from the internal ENVI .evf format (see Managing Vector Layer Files in the
ENVI User’s Guide).
New vector layers you generate and changes you make to vector layers in ENVI are
easily exported to industry-standard GIS formats.
Vector Displays
Getting Started with ENVI
Chapter 3: The ENVI Interface
69
When you select to display vector files in a Vector window, ENVI loads the vectors
into a Vector window.
Cursor mode
(also in title bar)
Coordinates
Active layer
Figure 3-11: Vector Window
Getting Started with ENVI
Vector Displays
70
Chapter 3: The ENVI Interface
When you select to display vector files in a display group, ENVI overlays the vectors
on the image in the selected display group.
Figure 3-12: Vector File Displayed Over Image in Display Group
Vector Displays
Getting Started with ENVI
Chapter 3: The ENVI Interface
71
Starting New Vector Windows
To start a new Vector window, select Window → Start New Vector Window from the
ENVI main menu bar.
Each window is numbered sequentially starting with Vector Window #1. You can
open new vector windows from the Available Vectors List (see “Opening New Vector
Windows” on page 63).
Zooming In and Out of Vector Windows
To zoom in on a section of the Vector window:
•
Middle-click and drag the cursor to define the region to magnify. ENVI
redraws the enlarged zoom region in the Vector window.
•
Shift + middle-click to zoom in to the display centered under the cursor.
To zoom out in the Vector window.
•
Middle-click inside the zoomed region. The vector display steps backward
through the previous zoom levels with one step per click.
•
Right-click inside the Vector window and select Previous Range. The vector
display steps backward through the previous zoom levels.
•
Right-click inside the Vector window and select Reset Range to reset all
zooming and set the vector display back to the original range.
Panning in Vector Windows
To pan to another region in the Vector window, left-click near any edge of the Vector
window. The Mode in the status bar displays Pan direction, where direction is the
direction of the pan, such as North, East, SE, and so forth.
Using Cursor Tracking in Vector Windows
If you are using image-to-map registration (see Registration in the ENVI User’s
Guide), you need to know the location of your cursor. If vectors are overlaid on a
display group, ENVI reports the position of the cursor by displaying it in the
Location field of the Vector Parameters dialog associated with that display group. If
vectors are displayed in a Vector window, ENVI reports the position of the cursor in
the bottom-left of the Vector window status bar.
Getting Started with ENVI
Vector Displays
72
Chapter 3: The ENVI Interface
A check mark appears next to the active layer name when you right-click in the
Vector window and select Select Active Layer. When a layer is active, the vector
cursor snaps to the nearest vector in that layer. When a layer is not active, the cursor
tracks the position anywhere in the window without using snap. In either case, leftclick and drag in the Vector window to list the map coordinates of the cursor’s
location in Easting, Northing order in the lower-left Vector window status bar.
Latitude and longitude display directly under the Easting, Northing map coordinates.
Vector Options
Vector data often consist of multiple layers of data. Use the Vector options in a Vector
window to control the appearance of vector layers, to add new vectors; to export
vector layer coordinates for use in image-to-map registration; and to view, edit, and
query vector attributes (see Working with Vectors in the ENVI User’s Guide for
details).
Vector Attributes
When vector layers have attributes associated with them, ENVI can read and interact
with shapefile attributes. Currently, ENVI only reads shapefile attributes or attributes
added through ENVI.
You can use the cursor to select vectors in the Vector window and highlight the
associated attributes or select an attribute and highlight the associated vector. You can
do a vector attribute query to create new vector layers with attributes selected using
simple mathematical and logical operators. ENVI also allows you to edit the existing
attributes or to add new attributes to vectors. You can plot point attribute names in the
Vector window and point symbol sizes associated with attribute values (see Vector
Attributes in the ENVI User’s Guide for instructions).
Vector Displays
Getting Started with ENVI
Chapter 3: The ENVI Interface
73
Plot Windows
ENVI plot windows present a graphical representation of your data. Plot windows
provide interactive analysis capabilities including moving plots between windows,
data input and output, plot output, editing, annotation, and other options. Plot
windows may contain spatial data (such as an X Profile), spectral data (such as a Z
Profile), or any x,y data.
See the following topics in ENVI Help for details on plots:
•
Extracting X and Y (Horizontal and Vertical) Profiles
•
Extracting Z Profiles
•
Using Interactive Plot Functions
Figure 3-13: X Profile Plot Window
Getting Started with ENVI
Plot Windows
74
Chapter 3: The ENVI Interface
Opening New Plot Windows
To open a new plot window, use one of the following:
•
From the ENVI main menu bar, select Window → Start New Plot Window.
•
From any plot window menu bar, select Options → New Window: Blank.
•
To create a copy of the current plot window including the data within it, select
Options → New Window with Plots from any plot window menu bar.
You can set up new plot windows as data collectors to hold useful plots from profiles
and other plot windows.
To move plots and plot labels between windows, see Using Interactive Plot Functions
in the ENVI User’s Guide.
To use Annotate Plot to annotate the x, y, and z profiles and other plots, see
Annotating Images and Plots in the ENVI User’s Guide).
Tip
Resize both plot and Image windows to their final desired size before annotation. If
you resize the plot window after annotation, the annotated objects are offset from
their correct positions.
Closing All Plot Windows
To close all open plot windows, select Window → Close All Plot Windows from the
ENVI main menu bar.
Plot Windows
Getting Started with ENVI
Chapter 3: The ENVI Interface
75
ENVI Mouse Buttons
To use all of ENVI’s functions, it is recommended that you have a three-button
mouse, or a mouse with two buttons and a scroll wheel.
Note
On Macintosh platforms, where only one mouse button is available, use
Alt/Option+click to emulate a middle mouse button. To emulate a left mouse
button, use Apple/Command+click.
Because mouse button functions vary within ENVI windows, you can view
applicable mouse functions through the Mouse Button Descriptions dialog. If you
have this dialog open, ENVI updates the dialog with mouse button descriptions as
you move the cursor from window to window.
Window ID
Cursor mode
Mouse buttons:
MB1 = left
MB2 = middle
MB3 = right
Figure 3-14: Mouse Button Descriptions Dialog
To display mouse button descriptions, select one of the following:
•
From the ENVI main menu bar, select Window → Mouse Button
Descriptions.
•
From the ENVI main menu bar, select Help → Mouse Button Descriptions.
•
From the Display group menu bar, select Window → Mouse Button
Descriptions.
Tip
Some interactive processes change the mouse functions listed in the following
tables. These processes include defining regions of interest (ROIs), annotation,
vector overlay, and dynamic overlay. These functions may be disabled to restore the
Getting Started with ENVI
ENVI Mouse Buttons
76
Chapter 3: The ENVI Interface
mouse buttons to their normal mode of operation. If the mouse buttons do not
respond as you expect them to, display the Mouse Button Descriptions dialog to
check which mode is in control of the cursor.
Image Window Mouse Button Functions
Mouse
Button
Left
Function
Click inside the Zoom box and drag it to a new location. The Zoom
window updates when you release the button.
Click outside the Zoom box to center it over the current pixel
position. Continue to hold the button and drag to continuously
update the Zoom window.
Double-click in the Image window to display the Cursor
Location/Value dialog.
Middle
No function.
Right
Click to display the right-click menu.
Table 3-2: Mouse Button Functions – Image Window
Zoom Window Mouse Button Functions
Mouse
Button
Left
Function
Click on the desired pixel to center the Zoom window on that pixel.
Click and hold to pan from the center of the window in the
direction of the cursor location. The speed of the pan varies with
the cursor’s distance from the center of the Zoom window. The
closer the cursor is to the center, the slower the pan.
Table 3-3: Mouse Button Functions – Zoom Window
ENVI Mouse Buttons
Getting Started with ENVI
Chapter 3: The ENVI Interface
Mouse
Button
77
Function
Middle
No function.
Right
Click to display the right-click menu.
Table 3-3: Mouse Button Functions – Zoom Window (Continued)
Scroll Window Mouse Button Functions
Mouse
Button
Left
Function
Click anywhere outside the Image box and drag. The Zoom
window and Image window update continuously.
Click, drag, and release the Image box to reposition the image. The
Zoom window and Image window update when you release the
button.
Click to center the Image box and image display over the selected
pixel.
Middle
Click and drag to create the meta Zoom box.
Right
Click to display the right-click menu.
Table 3-4: Mouse Button Functions – Scroll Window
Getting Started with ENVI
ENVI Mouse Buttons
78
Chapter 3: The ENVI Interface
Vector Window Mouse Button Functions
Mouse button functions in vector windows work differently than they do in ENVI
display groups. Cursor functions in the vector windows change depending on the
mode you select. See Controlling Cursor Modes in the ENVI User’s Guide for cursor
functions in the other modes. The Vector window mouse button functions for the
Cursor Query mode are:
Mouse
Button
Left
Function
On active layers: Snap to a near active vector and track map
coordinates and latitude/longitude. The coordinates display at the
bottom of the Vector window.
On inactive layers: Pan the display by clicking at any edge of the
Vector window. When the cursor is near the edge of the Vector
window, the Mode label in the Vector window status bar displays
Pan and the direction of the pan.
Note - To determine the active layer, right-click in the Vector
window and select Select Active Layer. A check mark appears
next to the active layer name.
Middle
Click and hold and drag to form a Zoom box.
Shift-click to zoom in to the display over the selected pixel.
Click to decrease the zoom factor.
Right
Click to display the right-click menu.
Table 3-5: Mouse Button Functions – Vector Window
ENVI Mouse Buttons
Getting Started with ENVI
Chapter 3: The ENVI Interface
79
Plot Window Mouse Button Functions
Mouse
Button
Left
Action
Click and hold and drag inside a plot window over data plot to
display the line-cursor, data point location, and x,y values.
Click and drag the corner of plot window to resize the window.
Click and drag to a new window on plot label to move plots to new
window.
Middle
Click and drag from any point inside the plot frame diagonally to
form a box containing the desired subset rescale x,y plot ranges.
Click inside the plot window to reset to the previous x,y plot
ranges.
Click the left side of the plot frame to set y axis to data range.
Right
Click inside the plot window to toggle the plot name labels.
Click on the plot label to delete a specific data plot.
Table 3-6: Mouse Button Functions – Plot Window
Getting Started with ENVI
ENVI Mouse Buttons
80
ENVI Mouse Buttons
Chapter 3: The ENVI Interface
Getting Started with ENVI
Chapter 4
Opening and
Displaying Files
This chapter provides instructions about opening files in ENVI, selecting files to display, and
loading files into display groups. It includes:
Opening Image Files in ENVI . . . . . . . . . . . 82
Opening Remote Datasets . . . . . . . . . . . . . . 83
Opening External Image Files in ENVI . . 101
Opening Previously Opened Files . . . . . . . 102
Getting Started with ENVI
Opening Vector Files . . . . . . . . . . . . . . . .
Opening Spectral Library Files . . . . . . . .
Displaying Images . . . . . . . . . . . . . . . . . .
Displaying Vectors . . . . . . . . . . . . . . . . . .
103
106
107
112
81
82
Chapter 4: Opening and Displaying Files
Opening Image Files in ENVI
You can open ENVI image files or other binary image files of known format. ENVI
automatically identifies and reads files of the following types:
• AVHRR
• HDF SeaWiFS
• MrSID
• BMP
• JPEG
• NLAPS
• ER Mapper, PCI (.pix)
• JPEG 2000
• PDS
• ERDAS 7.x (.lan)
• Landsat 7 Fast (.fst)
• RADARSAT
• ERDAS IMAGINE 8.x (.img)
• Landsat 7 HDF
• SRF
• GeoTIFF
• MAS-50
• TIFF
• GeoTIFF with metadata
(.txt and.met for Landsat,
*_metadata.txt for GeoEye-1,
*_metadata.xml for RapidEye)
• MRLC (.dda)
• HDF
The file retains its native format, and ENVI reads the necessary information from the
file header. To open other file types, see “Opening External Image Files in ENVI” on
page 101.
1. Choose one of the following options:
•
From the ENVI main menu bar, select File → Open Image File.
•
From the Available Bands List menu bar, select File → Open Image File.
•
From the Available Files List menu bar, select File → Open New File.
•
From any Input File dialog, click Open and select New File.
The Enter Data Filenames dialog appears.
2. Select the file to open.
3. Click Open. ENVI adds the filename and bands to the Available Bands List.
Tip
If the Header Info dialog appears when opening an ENVI-supported file, use the
Open External File option instead (see “Opening External Image Files in ENVI”
on page 101).
Opening Image Files in ENVI
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
83
Note
You can open multiple image files contained in an ASCII text file as long as the first
line of the ASCII file begins with the line ENVI File List. This can then be
followed by a list of filenames. Opening the ASCII text file causes ENVI to open all
the files listed.
Opening Remote Datasets
Use File → Open Remote Dataset or File → Remote Connection Manager to
access data from the following types of Web servers:
•
OGC Servers for Web Map Service (WMS) and Web Coverage Service (WCS)
•
JPEG 2000 Servers for JPEG 2000 Internet Protocol (JPIP) and Image Access
Solutions (IAS)
•
Geodatabases (only accessible from File → Remote Connection Manager)
See “Opening Datasets” on page 86 and “Using the Remote Connection Manager” on
page 91 for steps.
Supported Platforms
Supported platforms vary by connection type:
Windows
Connection Type
32-bit
ArcGIS® geodatabase a,b
Connect to and read from geodatabase
Save to file or personal geodatabase
Save to enterprise SDE geodatabase c
•
IAS and JPIP a
•
OGC WCS and WMS
•
64-bit
•
Mac OS X
Linux
Solaris
32-bit
64-bit
32-bit
64-bit
•
•
•
•
•
•
•
•
32-bit
64-bit
•
•
•
Table 4-1: Remote Dataset Supported Platforms
a
Windows users: these functions only run in 32-bit mode. If you have a 64-bit
Windows PC and you want to use these functions, run ENVI in 32-bit mode as
follows from the Windows Start menu: Program Files → ENVI x.x → 32-bit →
ENVI or ENVI + IDL or ENVI Zoom.
Getting Started with ENVI
Opening Image Files in ENVI
84
Chapter 4: Opening and Displaying Files
b
Supported on ArcGIS® Desktop 9.2 and later; tested on Windows XP 32-bit and
Vista 32-bit operating systems with ArcGIS® Desktop 9.3.
c Requires
an ArcInfo® or ArcEditor™ license (ArcView® software does not support
this feature).
OGC Servers
The Open Geospatial Consortium (OGC) provides a variety of protocol specifications
for transmitting geospatial data via the web. ENVI and ENVI Zoom support two of
these specifications: WMS and WCS. See http://www.opengeospatial.org for more
information.
OGC servers have several common features:
•
Data are sent as image files. ENVI and ENVI Zoom support JPEG 2000, JPEG,
and TIFF/GeoTIFF formats. If a dataset you are querying cannot be
transmitted in one of these formats, you cannot open the dataset.
•
You can customize data delivery by specifying a spatial extent, interpolation
type, pixel size, and map projection, which saves you from reading unwanted
data for regions you are not interested in. ENVI and ENVI Zoom manage the
details of server requests, such as downloading data tiles, deleting temporary
files, and reading data.
•
OGC servers provide a directory listing service called GetCapabilities to list
OGC datasets available on any server, or you can directly connect to an OGC
dataset.
OGC WCS
WCS is a protocol for serving raster data that represent properties of geographic
locations. WCS servers provide coverages that you can manipulate. WCS servers list
datasets at one level instead of in a folder hierarchy.
OGC WMS
WMS is a protocol for serving maps that are generated on-the-fly for display
purposes only. A powerful feature of WMS servers is that you can identify multiple
datasets that meet your criteria, and the server combines them into one displayable
map layer. WMS servers do not specify a pixel size for a given dataset, so ENVI or
ENVI Zoom estimate a default pixel size. You can change this value by setting the
WMS Pixels Per Side preference. WMS servers list datasets on the server in a folder
hierarchy.
Opening Image Files in ENVI
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
85
JPEG 2000 Servers
OGC and JPIP servers support delivery of image data at different resolutions that are
automatically resampled by the servers. IAS and JPIP servers send compression
parameters known as wavelets, while OGC servers send actual image files. This
means that ENVI and ENVI Zoom read any IAS server dataset.
Note
If you are working on a Windows 64-bit platform, you need to start ENVI or ENVI
Zoom in 32-bit mode to access data from JPIP or IAS servers.
To view datasets from IAS and JPIP servers, you need a server that uses the
ISO/IEC 15444-9 JPEG 2000 standard (JPEG 2000 Internet Protocol). IAS 3.x and
higher provides support for this version of the standard.
JPIP
JPIP is a client-server protocol used to serve JPEG 2000 compressed imagery (.jp2,
.j2c, and .jpx). No directory listing service is available with JPIP servers; you
must specify the full path to a dataset you want to view (for example,
jpip://exampleserver:1234/file.jp2).
If a dataset from a JPIP server contains map information, it is stored in the file header
using a GeoJP2 protocol. ENVI and ENVI Zoom attempt to read and import map
information and apply it to the input file whenever possible.
IAS
The IAS product, available from ITT Visual Information Solutions, provides a server
that streams JPEG 2000 and NITF 2.1 C8 compressed imagery using the JPIP
protocol, which you can display and analyze. IAS supports full JPIP streaming
capabilities, plus it provides a directory listing service, NITF support, and a tool to
convert any image file to JPEG 2000 or NITF 2.1 C8 formats. ENVI and ENVI Zoom
do not support opening CMYK compressed JPEG 2000 files using an IAS server.
An IAS server lists datasets in a hierarchy similar to that of a file system. You can
browse data from an IAS server in ENVI and ENVI Zoom.
An IAS server can list datasets that are not JPEG 2000 compressed, but it cannot
serve them; An error message appears if you attempt to open this type of dataset from
an IAS server. Once you select a JPEG 2000 compressed dataset through an IAS
server, you can also access metadata.
Getting Started with ENVI
Opening Image Files in ENVI
86
Chapter 4: Opening and Displaying Files
IAS servers retain and serve metadata associated with NITF datasets. ENVI and
ENVI Zoom can read and interpret NITF metadata, including map and wavelength
information, as well as file and image metadata, text segments (if present), and most
tagged record extensions (TREs). If map information is not present in NITF
metadata, the dataset is read in from a GeoJP2 UUID box, if present. See “Viewing
NITF Metadata from IAS Datasets” on page 90 for details about viewing metadata.
For more information about IAS functionality, refer to the ITT Visual Information
Solutions website.
Geodatabases
The ArcGIS® geodatabase is a data storage mechanism that allows for many types
and sources of geographic data, both raster and vector, to be supported in a consistent
manner. ENVI and ENVI Zoom support personal geodatabases (in Microsoft Access
.mdb format), file geodatabases, and enterprise geodatabases.
Opening Datasets
You can open remote datasets using File → Open Remote Dataset, which is
described here, or File → Remote Connection Manager, which is described in
“Using the Remote Connection Manager” on page 91.
Using the Open Remote Dataset Dialog
Open Remote Dataset is useful when you are already familiar with the connection
details of the dataset you want to open. You cannot use the Open Remote Dataset
dialog to access a server, only a specific dataset. The Open Remote Dataset dialog
only connects to datasets on JPIP, IAS, and OGC servers.
For JPIP and IAS servers, the connection string consists of the IP address or server
(host) name, port number, the path (relative to the server root), and filename. Preface
the URL with http:// or jpip://. For example:
jpip://ias-server:80/data/jpeg2000_file.jp2
URL
scheme
server name
path
filename
port number
For OGC servers, the connection string consists of the server name, port number, CGI
get request (followed by a question mark), and optional OGC keywords. Preface the
Opening Image Files in ENVI
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
87
URL with http://. “OGC Connection Keywords” on page 88 describes the
keywords. For example:
ogc-server.org/cgi-bin/mapserv_dem?coverage=srtmplus_raw&
width=1000&height=1000&bbox=-105,39,-104,40
where:
http://ogc-server.org/cgi-bin/mapserv_dem?coverage=srtmplus_raw&....
URL
scheme
server name
CGI get request
OGC keywords
Because no port number was specified in the example above, ENVI Zoom uses port
80 as the default.
You can also define a proxy server by setting the OGC Proxy Server preference.
Follow these steps to open a remote dataset:
1. Select File → Open Remote Dataset from the ENVI Zoom menu bar or
File → Open Remote File from the ENVI main menu bar. The Open Remote
Dataset dialog appears.
Figure 4-1: Open Remote Dataset Dialog
2. There are two ways to open a dataset from this dialog:
•
To open a new dataset, type (or paste) the connection string for the dataset
in the URL field. Refer to the beginning of this section for examples and
details about the format of the connection string.
•
If you have previously opened datasets, an arrow appears next to the URL
field. Click the arrow and select the dataset from the drop-down list.
3. Click OK.
Getting Started with ENVI
Opening Image Files in ENVI
88
Chapter 4: Opening and Displaying Files
4. If a username and password are required to log in to a server, the Connection
Authentication dialog appears. See “Connection Authentication” on page 90
for details on logging in.
After you click OK and after authentication is complete (if required), the
dataset is displayed and added to the Data Manager in ENVI Zoom or the
Available Bands List in ENVI. If you opened an IAS dataset that contains
metadata, you can view that metadata as described in “Viewing NITF
Metadata from IAS Datasets” on page 90.
OGC Connection Keywords
The OGC keywords specify details about what data to open on the server and how to
open it. You specify the details by using standard keywords defined by OGC.
Separate keywords from their values with =, and separate keyword/value pairs with &
(for example, width=500&height=500). ENVI and ENVI Zoom support the
following keywords:
Keyword
Description
WCS and WMS Keywords
The geographic extent (or bounding box) of the dataset. The
keyword value enables you to subset the data to open from the
server (for example, if the dataset contains data for the whole
world and you need only data for Colorado). Enter values in the
following order: minx, miny, maxx, maxy. The default is to open
the entire dataset. Example:
bbox
bbox=23.73,37.97,23.752,37.984
The number of samples in the image when it is opened. The default
for WCS is to use metadata from the image.
width
The default for WMS is to use the base layer (if there is one) and
use the pixel size of the base layer to calculate the width. If a base
layer is not available, then width is determined by using the WMS
Pixels Per Side preference. A square pixel size is selected, where
the greater of the number of samples and lines are equal to the
WMS Pixels Per Side value. Example: width=500
Table 4-2: OGC Connection Keyword Descriptions
Opening Image Files in ENVI
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
Keyword
89
Description
The number of lines in the image when it is opened. The default for
WCS is to use metadata from the image.
height
The default for WMS is to use the base layer (if there is one) and
use the pixel size of the base layer to calculate the height. If a base
layer is not available, then height is determined by using the WMS
Pixels Per Side preference. A square pixel size is selected, where
the greater of the number of samples and lines are equal to the
WMS Pixels Per Side value. Example: height=500
The format in which to transmit the data across the Internet. The
format must be among the list of formats supported by the OGC
server. ENVI and ENVI Zoom support JPEG 2000, JPEG, and
TIFF as transmission formats. The default is to first look for
JPEG 2000 (lower transmission time). If the server does not
support JPEG 2000, then it looks for any supported JPEG format,
then any supported TIFF format. If the server does not support the
specified format, it returns an error.
format
Example for WMS: format=image/jpeg
Example for WCS: format=jpg
WCS-only Keywords
Required. The name of the dataset. Example:
coverage
coverage=srtmplus_raw
The coordinate reference system of the image. This keyword value
must be a string that comes from the list of reference systems
supported by the server. Example: crs=EPSG:4326
crs
WMS-only Keywords
Required. The name of the layer. You can specify multiple,
comma-delimited, layers. ENVI and ENVI Zoom allow the server
to combine the WMS layers and display them as a single layer.
Example: layers=streets
layers
Table 4-2: OGC Connection Keyword Descriptions (Continued)
Getting Started with ENVI
Opening Image Files in ENVI
90
Chapter 4: Opening and Displaying Files
Keyword
Description
srs
The spatial reference system of the image. This value must be a
string that comes from the list of reference systems supported by
the server. Example: crs=EPSG:4326
style
The display style from the server-supported style list. This
specifies how to display certain features, if used (for example,
display a 2-pixel yellow line for roads). Example: style=visual
Table 4-2: OGC Connection Keyword Descriptions (Continued)
Connection Authentication
If a username and password are required to log in to a server or geodatabase, the
Connection Authentication dialog appears. Perform the following steps:
1. Enter a Username.
2. Enter a Password. Passwords are displayed as a series of asterisks
representing each character you type.
3. Click OK in the Connection Authentication dialog to attempt a connection
using the specified login information. If the connection fails, an error message
appears and the Connection Authentication dialog remains open so that you
can reenter the login information.
Note
Your username and password are retained for as long as the server or dataset
is open.
Viewing NITF Metadata from IAS Datasets
NITF metadata are only present for datasets on IAS servers that are in NITF format
or that were converted from NITF to JPEG2000. To view NITF metadata from an
IAS dataset:
1. Open the dataset using File → Open Remote Dataset (ENVI Zoom) or
File → Remote Connection Manager (ENVI).
Opening Image Files in ENVI
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
91
2. In the Data Manager (ENVI Zoom) or Available Bands List (ENVI), rightclick on the image name and select View NITF Metadata. The NITF
Metadata Viewer dialog appears.
If the NITF preference Automatically View Metadata in ENVI Zoom is set to
True, the metadata are automatically displayed.
When you save an IAS dataset to NITF format, the NITF metadata are passed
to the NITF output file, using the same rules as inheriting NITF metadata in the
NITF/NSIF Module. See Saving NITF Files in the NITF/NSIF Module User’s
Guide for details.
Note
To stream and view NITF imagery and metadata from IAS servers, you must have a
NITF/NSIF Module license.
Using the Remote Connection Manager
Use the Remote Connection Manager dialog to connect to geodatabases and servers,
to add a connection to a list of frequently visited servers, and to manage connection
properties. If accessing datasets on a WMS server, you can also use this dialog to
combine two or more datasets into one displayable map layer.
To open a remote dataset from the Remote Connection Manager dialog:
1. Select File → Remote Connection Manager from the ENVI Zoom menu bar
or Window → Remote Connection Manager from the ENVI main menu bar.
The Remote Connection Manager dialog appears (see Figure 4-2).
Getting Started with ENVI
Opening Image Files in ENVI
92
Chapter 4: Opening and Displaying Files
Figure 4-2: Remote Connection Manager Dialog
2. There are two ways to connect to a server or geodatabase from this dialog.
•
The dialog is initially empty. Click Connection, then select New and see
the steps in “Managing Connection Properties” on page 96 to create a new
connection.
•
If you have a commonly used connection that you have saved as a favorite,
click Favorites, then select the server name from the menu. To add
favorites to the Favorites list, see “Managing Favorites” on page 98.
Note
Connection may be slow.
The icons that appear in the Remote Connection Manager dialog differ
depending on the connection type, to help you easily distinguish among the
four types.
Opening Image Files in ENVI
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
93
3. Select the server or geodatabase from the Connection List. The list of available
datasets appears in the Dataset List with icons that indicate the dataset type:
Select the dataset to open from the Dataset List. The properties for the selected
dataset appear in the Properties List. If needed, you can edit some of the
properties before opening the dataset, as described in “Editing Properties” on
page 95.
Note
For OGC datasets only: if ENVI Zoom does not support one of the formats
under the Supported Formats drop-down list (in the Properties List), you
cannot open the dataset. You can view all of the dataset properties, but the
Open button is disabled.
Additionally, some IAS datasets cannot be opened. When you select an IAS
dataset from the Dataset List that cannot be opened, the properties do not
display in the Properties List, and the Open button is disabled.
4. If you want to combine multiple datasets on a WMS server and open them as
one map layer, select additional datasets from the Dataset List. You can multiselect datasets by pressing the Ctrl or Shift key as you select files.
Getting Started with ENVI
Opening Image Files in ENVI
94
Chapter 4: Opening and Displaying Files
5. Click Open. If ENVI and ENVI Zoom are both running from the same IDL
session, the dataset is opened in both applications. Refer to the following if
you are only running one application:
ENVI:
Raster datasets are added to the Available Bands List. Vector datasets are
added to the Available Vectors List. You cannot use the Edit Header dialog to
change header values for datasets on a server or in a geodatabase, and you
cannot use ENVI’s vector tools to edit a vector layer originating from a
geodatabase. If you opened an IAS dataset that contains NITF metadata, you
can view that metadata as described in “Viewing NITF Metadata from IAS
Datasets” on page 90.
ENVI Zoom:
The dataset may be automatically displayed and added to the Layer Manager,
depending on your display preferences. (See “Display General Preferences” on
page 141.) If you opened multiple WMS datasets as one displayable map layer,
the Layer name in ENVI Zoom is a combination of all selected dataset names.
If you opened an IAS dataset that contains metadata, you can view that
metadata as described in “Viewing NITF Metadata from IAS Datasets” on
page 90. You cannot use ENVI Zoom’s vector tools to edit a vector layer
originating from a geodatabase.
6. If you have connected to a geodatabase and datasets are added to or removed
from the geodatabase while you are working in ENVI Zoom, you can refresh
the Remote Connection Manager to see the updates. In the Remote Connection
Manager, Connection and select Refresh, or right-click on a geodatabase
name in the Connection List and select Refresh. The Dataset List updates to
show the changes.
Opening Image Files in ENVI
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
95
Editing Properties
Edits you make to dataset properties apply to the current dataset only. The properties
you can edit depend on the server type. The following describes the properties you
can edit:
Geodatabases
You cannot edit properties in personal, file, or enterprise geodatabases.
IAS
All properties from IAS servers are read-only. Raw JPIP servers cannot
display properties. The JPEG 2000 compression properties that are
always available for viewing are Number of Layers, Number of
Components, Number of Discard Levels, Progression, Number of Tiles,
Bit Depth, and flags to indicate if the data are reversibly compressed,
YCC rotated, or signed.
• If XML boxes or UUID boxes are present in the dataset, you can
select from their respective drop-down lists to view them in a
separate window.
• If NITF metadata is present in one of the XML boxes, the NITF
metadata is imported if the file is opened, but only the XML data are
accessible in the Remote Connection Manager dialog’s Properties
List.
• If a GeoJP2 style UUID box is present, the map information is
extracted and the following fields are added to the properties listing:
Projection, Top Boundary, Left Boundary, X Pixel Size, and Y Pixel
Size.
WCS
The WCS properties you can edit are Formats, Coordinate System,
Boundary (Top, Bottom, Left, and Right), Interpolation Type, and Pixel
Size (X and Y).
• Formats, Coordinate System, and Interpolation Type are drop-down
lists containing the values provided by the server. Select the value
from the drop-down list.
• Boundary and Pixel Size values are derived from the coverage data.
You can manually edit these values to customize the geographic
extent and resolution of the dataset to open.
Getting Started with ENVI
Opening Image Files in ENVI
96
Chapter 4: Opening and Displaying Files
WMS
The WMS properties you can edit are Formats, Spatial Reference
System, Boundary (Top, Bottom, Left, and Right), Number of Samples,
Number of Lines, and Map Style.
• Formats, Spatial Reference System, and Map Style are drop-down
lists containing the values provided by the server. Select the value
from the drop-down list.
• Boundary, Number of Samples, and Number of Lines are derived
from the layer data. You can manually edit these values to customize
the geographic extent and resolution of the dataset to open.
Multi- WMS
When you select multiple WMS layers to open, the properties that
appear are a subset of the properties available for a single WMS dataset.
The multi-WMS properties you can edit are Formats, Spatial Reference
System, Boundary (Top, Bottom, Left, and Right), Number of Samples,
and Number of Lines.
• Formats and Spatial Reference System drop-down lists contain all
of the options common to all of the selected datasets. Select the
value from the drop-down list.
• The Boundary, Number of Samples, and Number of Lines values
default to value of the first dataset you selected in the Remote
Connection Manager.
Managing Connection Properties
The Connection Properties dialog lets you enter connection information for a new
connection or edit the name of an existing connection.
1. Choose one of the following:
•
To enter properties for a new connection, click Connection in the Remote
Connection Manager and select New. The Connection Properties dialog
appears. The fields are initially blank.
•
To edit the name of an existing connection, select the connection you want
to edit. Click Connection and select Properties. Or, right-click on a server
name in the Connection List and select Properties. The Connection
Properties dialog appears. The fields are populated with the properties of
that connection. You can only edit the connection name.
2. The URL field is optional and provides a convenient place for you to specify a
path or connection details in a single string.
Opening Image Files in ENVI
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
97
If you press Enter or move to another field in the dialog, the remaining fields
are automatically populated from the information in the URL. You can edit the
fields described in Steps 3-8 if necessary. Or, click OK after entering a URL to
connect as described in Step 9.
Following are examples of URLs:
IAS
jpip://exampleserver:1234/
OGC WCS
http://exampleserver:1234/cgi-bin/mapserv.exe?
map=/ogc_data/wcs_test.map&service=wcs
OGC WMS
http://exampleserver:1234/cgi-bin/mapserv.exe?
map=/ogc_data/wms_test.map&service=wms
Enterprise geodatabase
exampleserver:5151
3. In the Name field, enter a custom name for the connection to help you
recognize it in the Connection List. The default value is the name of the
connection.
4. From the Type drop-down list, select from the available list of data sources. If
you are editing existing connection properties, you cannot modify the
selection. The choices are File Based Geodatabase, Personal Geodatabase,
Enterprise (SDE) Geodatabase, OGC Web Coverage Service (WCS),
OGC Web Map Service (WMS), and IAS Service. The list of available
choices depends on your platform. Refer to the Installation and Licensing
Guide for supported platforms. This guide is available from the ITT Visual
Information Solutions web site or from the ENVI Tutorial Data DVD that
shipped with your software.
5. Enter the Connection name you want to connect to.
6. Enter the Port number.
7. If the connection type is OGC, enter a required CGI Path for querying OGC
connections.
8. If the connection type is OGC, you can enter an optional Prefix for querying
OGC connections. This is a configuration string that is required to access the
correct datasets on the server.
9. To open a file or personal geodatabase, select File Based Geodatabase or
Personal Geodatabase from the Type drop-down list. Click the Open button
Getting Started with ENVI
Opening Image Files in ENVI
98
Chapter 4: Opening and Displaying Files
. The Browse for Folder dialog appears. Select a geodatabase from your
computer, and click OK. The Path field in the Connection Properties dialog is
populated with the path and filename of the geodatabase.
10. Click OK in the Connection Properties dialog. ENVI or ENVI Zoom confirms
the information you entered is valid and returns you to the Remote Connection
Manager dialog. You may be prompted for a username and password if they
are required. See “Connection Authentication” on page 90 for details.
If the connection does not respond or any of the connection information is
invalid, an error message appears and the Connection Properties dialog
remains open so that you can reenter the properties.
If you are connecting to an enterprise server and your database version string is
not set to sde.DEFAULT, the Connection Details dialog appears. Select a
transactional version from the Version Name list, or specify the details for a
historical version. See “Creating Spatial Database Connections” in ArcGIS®
Desktop Help for details.
The new or edited connection becomes the active connection in the Remote
Connection Manager dialog, and ENVI or ENVI Zoom queries that connection
for available datasets and displays them in the Dataset List.
Managing Favorites
You can add commonly used connections to a list of favorites, so that you can easily
open those connections in the future.
Note
The Favorites menu option is disabled for connections that require a password.
1. In the Remote Connection Manager dialog, select the connection name from
the Connection List.
2. Select one of the following:
•
Right-click on the connection name and select Add to Favorites.
•
Click Favorites and select Add to Favorites.
The Add to Favorites dialog appears.
3. Do any of the following:
•
In the Name field, enter a custom name for the connection to help you
recognize it in the Favorites List.
Opening Image Files in ENVI
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
•
99
If one or more folders exist in the Favorites List, select the folder into
which to add the new favorite.
4. Click OK. The name is added to the Favorites List, which appears in the
Remote Connection Manager dialog Favorites menu.
You can manage your Favorites List by creating folders in which to group favorites,
by reordering favorites, and by deleting or renaming favorites. To manage favorites,
click Favorites and select Manage to open the Favorites Manager dialog. This dialog
contains the Favorites List.
•
To create a new folder, right-click and select New Folder. The Enter Name
dialog appears. Type a Name for the new folder and click OK. The new folder
appears in the Favorites List.
•
To reorder the Favorites List, or to move favorites to a folder, select the name
from the Favorites List, then drag and drop the name to a new location.
•
To rename a favorite or folder, right-click on the name in the Favorites List and
select Rename. The Enter Name dialog appears. Type a new Name and click
OK. The new name appears in the Favorites List.
•
To delete a favorite or folder, right-click on the name and select Delete. The
name is removed from the Favorites List. Deleting a folder deletes all of the
connections and subfolders associated with it.
You can share your favorites with another user, but the operating systems and bit
architecture (32-bit or 64-bit) must be the same. To share your favorites, give your
user a copy of the ENVI Zoom preference file, envizoom_prefs.sav, which is in
the following directory:
Windows:
Documents and Settings\username\.idl\itt\components-37x_x-osname-bits\
Unix and Linux:
/home/username/.idl/itt/components-37-x_x-osname-bits/
Where x_x is the ENVI version number, osname is the operating system you
are running, and bits is 32 or 64.
Your users should save this file to the components-37-x_x-osname-bits
directory on their computer and restart ENVI Zoom. The next time the user clicks
Favorites in the Remote Connection Manager, the favorites will be available.
Getting Started with ENVI
Opening Image Files in ENVI
100
Chapter 4: Opening and Displaying Files
Note
Copying a .sav file over an existing .sav file overwrites all ENVI Zoom
preference settings or favorites that were previously set.
When you are finished working with the Favorites Manager dialog, click OK to close
the dialog. To access a favorite connection, click Favorites and select the connection
name.
Opening Image Files in ENVI
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
101
Opening External Image Files in ENVI
While you can use the Open Image File and New File options (described in
“Opening Image Files in ENVI” on page 82) to open most file types, it is often more
convenient to use internal or external header information for specific known file
types. Use the Open External File option to read several standard file types
including formats for selected sensors, military formats, digital elevations model
(DEM) formats, image processing software formats, and generic image formats.
ENVI reads the necessary parameters from internal headers and it is usually not
necessary for you to enter any information in the Header Information dialog.
For a list of ENVI’s supported input files, see “ENVI Supported Input File Formats”
on page 33.
1. From the ENVI main menu bar, select File → Open External File →
file_type → file_format.
where:
file_type is the type of external file (for example, Landsat)
file_format is the format of the external file (for example, HDF)
The Enter file_type Filenames dialog appears.
2. Select a file to open.
3. Click Open. ENVI automatically extracts the necessary header information,
including the associated georeferencing information, and places the filename
and bands in the Available Bands List.
Each file type and the associated file format options available from File → Open
External File is discussed in detail in Opening External Files in the ENVI User’s
Guide.
Getting Started with ENVI
Opening External Image Files in ENVI
102
Chapter 4: Opening and Displaying Files
Opening Previously Opened Files
Use the previous files list to open a file from a list of the 25 most recently opened
files in ENVI. When you open a new file, ENVI adds it to the top of the previous files
list. When the list exceeds 25 filenames, ENVI removes the file at the bottom of the
list. You can optionally stipulate that certain files always remain on the previous files
list and always appear at the top of the list (see Previous Files List Preference
Settings in the ENVI User’s Guide).
1. Open the previous files list with either of the following:
•
From the ENVI main menu bar, select File → Open Previous File.
•
From any Input File dialog, click Open and select Previous File.
2. Select the desired filename. ENVI adds the filename and bands to the
Available Bands List.
Opening Previously Opened Files
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
103
Opening Vector Files
You can open vector files in ENVI in several ways. Vector files may be available in
any of the following formats:
• ArcInfo® Interchange (*.e00)
• MapInfo Interchange format (*.mif)
• Shapefiles (*.shp)
• Microstation DGN (*.dgn)
• DXF vector files (*.dxf)
• USGS DLG files (*.ddf, *.dlg)
• ENVI vector files (*.evf)
• USGS SDTS files (*.dlg)
You may load as many vector layers as desired, but each file should contain one
vector layer only.
1. Use one of the following:
•
From the ENVI main menu bar, select File → Open Vector File.
•
From the ENVI main menu bar, select Vector → Open Vector File.
•
From any Input File dialog, click Open and select EVF File.
The Select Vector Filenames dialog appears.
2. In the Files of type drop-down list, select All Files (*).
3. Select one or more vector filenames and click Open. Either of the following
occurs:
•
If you selected an internal vector file, ENVI adds the layers to the
Available Vectors List.
•
If you selected an external vector file, the Import Vector Files Parameter
dialog appears. This dialog enables you to open multiple vector files of
different file types.
Getting Started with ENVI
Opening Vector Files
104
Chapter 4: Opening and Displaying Files
Figure 4-3: Import Vector Files Parameters Dialog
The Selected Input Files field lists the vector filenames. Select a filename,
and the Layer Name and Native File Projection areas update with the
information for that file. Because ENVI vector files (.evf) already contain
layer name and map projection information, these dialog options are inactive.
Opening Vector Files
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
105
4. To load another file, click Input Additional Files. The Select Vector
Filenames dialog appears; choose one or more files of any vector type to open.
5. To send all of the non-EVF vector files to memory, click Output to Memory
for All. Click OK, and the files are listed in the Available Vectors List. EVF
files are native to ENVI and do not require conversion to file or memory.
6. To apply the current map projection parameters to all files in the list with
unknown projections, click Apply Projection to Undefined. Unknown
projections are listed as Arbitrary in the map projections list box of the dialog.
Note
Files listed with known projections are not converted to the current map
projection when you click Apply Projection to Undefined.
7. Click OK to start the specified conversions. When the conversions are
complete, ENVI adds the vector layers to the Available Vectors List.
Getting Started with ENVI
Opening Vector Files
106
Chapter 4: Opening and Displaying Files
Opening Spectral Library Files
To open a spectral library to use for processing:
1. From any Input File dialog, click Open and select Spectral Library. The
Input File dialog appears.
2. Select the desired spectral library.
3. Click Open. The Input File dialog re-appears, and ENVI lists the Spectral
Library file in the Input File dialog Select Input File List, and also in the
Available Bands List.
Opening Spectral Library Files
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
107
Displaying Images
Use the Available Bands List to access the files and the individual bands of each file
that you have open during the current session. From the Available Bands List you can
display gray scale and color images and view meta file components and displayed
band information.
If the image header file contains default bands to load, you do not need to use the
Available Bands List to initiate a display; ENVI automatically loads the image into a
display group when you open the file (see Editing ENVI Headers in the ENVI User’s
Guide).
The options you see in the Available Bands List vary, depending upon whether you
want to display an image in gray scale, or in RGB color.
Active display group
No open display groups
Figure 4-4: Available Bands List Gray Scale Band option (right) and RGB Bands
option (left)
If the Available Bands List is hidden, bring it to the front of other open ENVI
windows by selecting Window → Available Bands List from the ENVI main menu
bar.
Getting Started with ENVI
Displaying Images
108
Chapter 4: Opening and Displaying Files
When there are no open display groups, the button at the bottom of the Available
Bands List reads No Display. When one or more display groups are open, the button
at the bottom of the Available Bands List reads Display #n, where n is the number
corresponding to the number in a display group title bar.
The first image you load automatically appears in a new window. When loading
subsequent images, you can load them into an existing display group, or you can load
them into a new display group. The selected display is called the active display
group.
If RRDS files are available for a given image, ENVI uses these to display the image
in the display group. See “Reduced Resolution Data Sets” on page 48 for more
information.
Displaying Gray Scale Images
To display a gray scale image:
1. In the Available Bands List, select the Gray Scale radio button.
2. If no display groups are open, proceed to the next step. If one or more display
groups are open, select where to display the image. Either:
•
Click Display #n and select New Display to open a new, empty display
group.
•
Click Display #n and select the desired display group.
3. Select the input band name. The band name appears under the Selected Band
area.
4. Click Load Band. ENVI loads the band into the display group.
To display a gray scale band:
1. In the Available Bands List, right-click on the band name.
2. Select either:
•
Load Band to New Display, to load the band to a new display group.
•
Load Band to Current Display, to load the band to the active display
group.
Tip
You can also load the gray scale image by double-clicking the band name.
Displaying Images
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
109
Displaying RGB Images
To display an RGB image:
1. In the Available Bands List, select the RGB radio button.
2. If no display groups are open, proceed to the next step. If one or more display
groups are open, select where to display the image. Either:
•
Click Display #n and select New Display to open a new, empty display
group.
•
Click Display #n and select the desired display group.
3. Select in sequence the red, green, and blue bands to display (or on individual
R, G, or B bands using the radio buttons).
4. Click Load RGB. ENVI loads the bands into the display group.
Tip
You can also load the image by double-clicking the band name you select for the
B band.
Displaying True Color or Color Infrared Images
If an input file has wavelengths for each band stored in the header and the file
contains bands in the needed wavelength ranges, you can display a true color image
or a CIR (color infrared) image from the Available Bands List without having to
designate the individual bands for red, green, and blue.
ENVI displays the true-color image band in the red wavelength region (0.6-0.7 μm)
in red, the band in the green region (0.5-0.6 μm) in green, and the band in the blue
region (0.4-0.5 μm) in blue. ENVI displays the CIR image band in the near-infrared
wavelength region (0.76-0.9 μm) in red, the band in the red region in green, and the
band in the green region in blue.
If the file does not have bands in the needed wavelengths, ENVI uses the bands
nearest to the wavelengths. This may produce a gray scale image if red, green, and
blue are set to the same band.
To display a true-color or CIR image:
1. In the Available Bands List, right-click on the filename.
2. Select either:
Getting Started with ENVI
Displaying Images
110
Chapter 4: Opening and Displaying Files
•
Displaying Images
Load True Color or Load CIR, to load the image to a new display group
if no display groups are open.
Getting Started with ENVI
Chapter 4: Opening and Displaying Files
111
•
Load True Color to <new> or Load CIR to <new>, to load the image to
a new display group.
•
Load True Color to <current> or Load CIR to <current>, to load the
image to the active display group.
Displaying Default RGB Combinations
If the header file has default bands to load (see Editing ENVI Headers in the ENVI
User’s Guide), you can select to load the default bands through the Available Bands
List right-click menu. Typically, ENVI automatically loads default bands when you
open the file; however, the menu option is available if you need to load the display
again while the file is listed in the Available Bands List.
1. In the Available Bands List, right-click on the filename.
2. Either:
•
Select Load Default RGB to load the image to a new display group if no
display groups are open.
•
Select Load Default RGB <new> to load the image to a new display
group.
•
Select Load Default RGB <current> to load the image to the active
display group.
Getting Started with ENVI
Displaying Images
112
Chapter 4: Opening and Displaying Files
Displaying Vectors
Use the Available Vectors List to load vectors into a Vector window or to overlay
them on a displayed image. You can simultaneously overlay vector layers of different
projection types or overlay vector layers that have projection types different than the
image. The image or the first vector layer displayed sets the projection type, and all
other layers are automatically converted to that projection type.
If the Available Vectors List is hidden, bring it to the front of other open ENVI
windows by selecting Window → Available Vectors List from the ENVI main
menu bar.
1. In the Available Vectors List, select the layer name. To display all of the layers,
click Select All Layers.
2. Click Load Selected.
•
If no display groups or other Vector windows are open, ENVI loads the
vector to a new Vector window.
•
If a display group and/or Vector window are open, the Load Vector Layers
dialog appears.
3. If the Load Vector Layers dialog appears, select a vector destination display
window.
•
If any display groups are open, the display names (for example,
Display #1) appear in the list. Select the desired display group to which to
plot the vectors and click OK. ENVI overlays the vectors on the displayed
image.
•
If any Vector windows are open, the Vector window names (such as,
Vector Window #1) appear in the list. Select the desired Vector window to
which to plot the vectors and click OK. ENVI adds the vectors to the open
Vector window.
•
To plot the vectors in a new Vector window, select New Vector Window
and click OK.
See Vector Layer Options in the ENVI User’s Guide for additional details.
Displaying Vectors
Getting Started with ENVI
Chapter 5
Working with Header
Files
This chapter describes how to create and edit ENVI header files. It includes:
The ENVI Header Format . . . . . . . . . . . . . 114
Creating Header Files . . . . . . . . . . . . . . . . 123
Editing Header Files . . . . . . . . . . . . . . . . . 127
Getting Started with ENVI
ENVI File Type File . . . . . . . . . . . . . . . . . 128
ENVI Sensor File . . . . . . . . . . . . . . . . . . . 130
113
114
Chapter 5: Working with Header Files
The ENVI Header Format
The ENVI header file contains information ENVI uses to read an image data file.
ENVI typically creates a header file the first time you access a data file in a format
that it does not automatically recognize. You enter the required information in the
Header Info dialog, which appears when the file is opened (see “Creating Header
Files” on page 123). You can later edit the information using the Edit ENVI Header
option (“Editing Header Files” on page 127).
You can also generate an ENVI header outside ENVI using a text editor. The file
must start with the text string ENVI for ENVI to recognize it as a native file header.
Keywords within the file indicate critical file information. You can add comments to
the file by inserting a line with a semicolon as the first character. ENVI ignores these
lines when parsing the header file. Comments can appear anywhere within a header
file, but they must be on their own line, and the semicolon must be the first character
of that line. Comments cannot follow a keyword/value pair.
A description of the keywords (in alphabetical order) for an ENVI header file
follows. See “Example ENVI Header File” on page 120 for an example header file.
Field
Description
band names
Allows entry of specific names for each band of an image.
bands
The number of bands per image file.
bbl
Lists the bad band multiplier values of each band in an image,
typically 0 for bad bands and 1 for good bands.
byte order
The order of the bytes in integer, long integer, 64-bit integer,
unsigned 64-bit integer, floating point, double precision, and
complex data types. Use one of the following:
• Byte order=0 (Host (Intel) in the Header Info dialog) is
least significant byte first (LSF) data (DEC and MS-DOS
systems).
• Byte order=1 (Network (IEEE) in the Header Info
dialog) is most significant byte first (MSF) data (all other
platforms).
class lookup
This keyword pertains to classification files. It lists RGB color
definitions for each respective class, and class names.
Table 5-1: Header File Keywords
The ENVI Header Format
Getting Started with ENVI
Chapter 5: Working with Header Files
Field
115
Description
class names
This keyword pertains to classification files. It lists the
classification names.
classes
This keyword pertains to classification files. It defines the
number of classes, including the unclassified.
complex
function
Specifies the values to calculate from a complex image and to
use when displaying the image, calculating statistics for the
image, or writing the image to a new file. Values include
Real, Imaginary, Power, Magnitude, and Phase. The
default value is Phase.
Table 5-1: Header File Keywords (Continued)
Getting Started with ENVI
The ENVI Header Format
116
Chapter 5: Working with Header Files
Field
Description
coordinate
system string
When you save a georeferenced file to ENVI raster format,
ENVI adds a coordinate system string field to the
header file. It lists the parameters used for a geographic
coordinate system or projected coordinate system. Following
are some examples:
A geographic coordinate system (for example, Geographic
Lat/Lon) string contains the word GEOGCS and lists the
coordinate system name, datum, spheroid, prime meridian,
and units:
coordinate system string =
GEOGCS["GCS_WGS_1984",
DATUM["D_WGS_1984",
SPHEROID["WGS_1984",6378137.0,298.257223563]],
PRIMEM["Greenwich",0.0],
UNIT["Degree",0.0174532925199433]]
A projected coordinate system string contains the word
PROJCS and lists all of the geographic coordinate system
parameters, plus detailed parameters that describe the
projected coordinate system:
coordinate system string =
PROJCS["WGS_1984_South_Georgia_Lambert",
GEOGCS["GCS_WGS_1984",
DATUM["D_WGS_1984",
SPHEROID["WGS_1984",6378137.0,298.257223563]],
PRIMEM["Greenwich",0.0],
UNIT["Degree",0.0174532925199433]],
PROJECTION["Lambert_Conformal_Conic"],
PARAMETER["False_Easting",0.0],
PARAMETER["False_Northing",0.0],
PARAMETER["Central_Meridian",-37.0],
PARAMETER["Standard_Parallel_1",-54.0],
PARAMETER["Standard_Parallel_2",-54.75],
PARAMETER["Latitude_Of_Origin",-55.0],
UNIT["Meter",1.0]]
Table 5-1: Header File Keywords (Continued)
The ENVI Header Format
Getting Started with ENVI
Chapter 5: Working with Header Files
117
Field
Description
coordinate
system string
Refer to the ITT Visual Information Solutions Tech Tips for a
list of predefined geographic and projected coordinate system
strings:
1. Go to http://www.ittvis.com/services/search.asp.
2. In the Enter Keyword field, type projection engine.
3. Click Submit.
4. In the search results, open the Tech Tip titled, “ESRI
Projection Engine Reference v1.0.”
data gain
values
Gain values for each band.
data ignore
value
Currently used only in ENVI programming (see
ENVI_FILE_QUERY in the ENVI Reference Guide for more
information).
data offset
values
Offset values for each band.
data type
The type of data representation, where 1=8-bit byte; 2=16-bit
signed integer; 3=32-bit signed long integer; 4=32-bit floating
point; 5=64-bit double-precision floating point; 6=2x32-bit
complex, real-imaginary pair of double precision; 9=2x64-bit
double-precision complex, real-imaginary pair of double
precision; 12=16-bit unsigned integer; 13=32-bit unsigned
long integer; 14=64-bit signed long integer; and 15=64-bit
unsigned long integer.
default bands
If set, indicates which band numbers to automatically load into
the Available Bands List gray scale or R, G, and B fields every
time the file is opened. By default, a new image is
automatically loaded when a file that has default bands defined
in its header is opened. If only one band number is used, then
ENVI loads a gray scale image.
default
stretch
Determines what type of stretch (% linear, linear range,
Gaussian, equalization, square root) to use when ENVI
displays the image.
Table 5-1: Header File Keywords (Continued)
Getting Started with ENVI
The ENVI Header Format
118
Chapter 5: Working with Header Files
Field
Description
dem band
Path and filename of a DEM that you associate with an image.
dem file
Index (starting at 1) of a selected DEM band that you associate
with an image. The dem band is not written if the DEM file
contains a single band, or if the first band of an image was
chosen. In these cases, the dem band value defaults to 0. See
Editing ENVI File Headers in the ENVI User’s Guide.
description
A character string describing the image or the processing
performed.
file type
The ENVI-defined file type, such as a certain data format and
processing result. The available file types are listed in the
filetype.txt file (see “ENVI File Type File” on page 128).
The file type ASCII string must match an entry in the
filetype.txt file verbatim, including case.
fwhm
Lists full-width-half-maximum (FWHM) values of each band
in an image. Units should be the same as those used for
wavelength and set in the wavelength units parameter.
geo points
Geographic corners for non-georeferenced files. You can enter
between one and four pixel locations and their corresponding
latitudes and longitudes. Following is an example:
geo points = {
1.0000, 1.0000, 32.89380137, -117.07201460,
1002.0000, 1.0000, 32.87364744, -116.95855862,
1.0000, 1002.0000, 32.80628336, -117.09960891,
1002.0000, 1002.0000, 32.78615422, -116.98625969}
header offset
The number of bytes of imbedded header information present
in the file (for example, 128 bytes for ERDAS 7.5 .lan files).
ENVI skips these bytes when reading the file.
interleave
Refers to whether the data are BSQ, BIP, or BIL.
lines
The number of lines per image for each band.
Table 5-1: Header File Keywords (Continued)
The ENVI Header Format
Getting Started with ENVI
Chapter 5: Working with Header Files
Field
map info
119
Description
Lists geographic coordinates information in the order of
projection name (UTM), reference pixel x location (in file
coordinates), pixel y, pixel easting, pixel northing, x pixel size,
y pixel size, projection zone, North or South (UTM only).
Note - In ENVI, pixel values always refer to the upper-left
corner of the pixel. Map coordinates also typically refer to the
upper-left corner of the pixel. However, if you entered “magic
pixel” coordinates in the ENVI header, the map coordinates
would refer to the x,y coordinates entered. For example,
x=1.5, y=1.5 would make the map coordinates refer to the
center of the pixel.
pixel size
Indicates x and y pixel size in meters for non-georeferenced
files.
major frame
offsets
The number of extra bytes to skip at the beginning and ending
of the major frame. See Editing ENVI File Headers in the
ENVI User’s Guide.
minor frame
offsets
The number of extra bytes to skip at the beginning and ending
of the minor frame. See Editing ENVI File Headers in the
ENVI User’s Guide.
projection
info
Describes user-defined projection information. This keyword
is added to the ENVI header file if a the file uses a userdefined projection instead of a standard projection. ENVI uses
this information to read the file on machines that do not
contain this user-defined projection in the
map_proj\map_proj.txt file.
reflectance
scale factor
The value that, when divided into your data, would scale it
from 0-1 reflectance.
rpc info
Lists rational polynomial coefficient (RPC) geolocation
information if your input file has this associated information.
See Editing ENVI File Headers in the ENVI User’s Guide.
samples
The number of samples (pixels) per image line for each band.
Table 5-1: Header File Keywords (Continued)
Getting Started with ENVI
The ENVI Header Format
120
Chapter 5: Working with Header Files
Field
Description
sensor type
Instrument types, such as Landsat TM, SPOT, RADARSAT,
and so on. The available sensor types are the sensor.txt file
described in “ENVI Sensor File” on page 130. The sensor type
ASCII string defined here must match one of the entries in the
sensor.txt file verbatim, including case.
spectra names
This keyword pertains to spectral library files only. It contains
a comma-separated list of ASCII names enclosed in {curly
brackets}.
wavelength
Lists the center wavelength values of each band in an image.
Units should be the same as those used for the fwhm field
(described next) and set in the wavelength units parameter.
wavelength
units
Text string indicating the wavelength units.
x start and
y start
Defines the image coordinates for the upper-left hand pixel in
the image. Images that are spatial subsets of larger images
often use an image coordinate system that references the
parent (or larger) image so that you can link and dynamically
overlay the two images. The default values are (1,1) so that the
upper-left hand pixel has an image coordinate of (1,1).
Note - Changing these values does not affect the way ENVI
reads the image data from the file.
z plot
average
Values indicate the number of pixels in the x and y directions
to average for Z plots.
z plot range
Values indicating the default minimum and maximum values
for Z plots.
z plot titles
Allows entry of specific x and y axis titles for Z plots.
Table 5-1: Header File Keywords (Continued)
Example ENVI Header File
A typical ENVI header file looks like this:
ENVI
description = {
The ENVI Header Format
Getting Started with ENVI
Chapter 5: Working with Header Files
121
Registration Result. Method1st degree Polynomial w/ nearest
neighbor [Wed Dec 20 23:59:19 1995] }
samples = 709
lines
= 946
bands
= 7
header offset = 0
file type = ENVI Standard
data type = 1
interleave = bsq
sensor type = Landsat TM
byte order = 0
map info = {UTM, 1, 1, 295380.000, 4763640.000, 30.000000,
30.000000, 13, North}
z plot range = {0.00, 255.00}
z plot titles = {Wavelength, Reflectance}
pixel size = {30.000000, 30.000000}
default stretch = 5.0% linear
band names = {
Warp (Band 1:rs_tm.img), Warp (Band 2:rs_tm.img), Warp (Band
3:rs_tm.img), Warp (Band 4:rs_tm.img), Warp (Band 5:rs_tm.img),
Warp (Band 6:rs_tm.img), Warp (Band 7:rs_tm.img)}
wavelength = {
0.485000, 0.560000, 0.660000, 0.830000, 1.650000, 11.400000,
2.215000}
fwhm = {
0.070000, 0.080000, 0.060000, 0.140000, 0.200000, 2.100000,
0.270000}
Getting Started with ENVI
The ENVI Header Format
122
Chapter 5: Working with Header Files
Classification results files include the following additional keywords:
classes = 4
class lookup = {
class names = {
Unclassified,
region 1,
region 2,
region 3}
0,
0,
0,255,
0,
0,
0,255,
0,255,255,
0}
Spectral library files include the following additional keywords:
spectra names = {
ACTINOLITE IN-4A, ALBITE TS-6A, ALMANDINE GARNET NS-4A, ALUNITE
SO-4A,
AMBLYGONITE P-3A, ANALCIME TS-18A, ANATASE SYNTHETIC O-12A,
ANDESINE TS-4A, ANGLESITE SO-10A, ANHYDRITE SO-1A, ANORTHITE TS5A,
ANTHOPHYLLITE IN-8A, ANTLERITE SO-11A, APATITE P-1A, APHTHITALITE
SO-9A}
The ENVI Header Format
Getting Started with ENVI
Chapter 5: Working with Header Files
123
Creating Header Files
When ENVI first opens a file, it requires specific information regarding the file
characteristics. If the file is an ENVI format file, the necessary information is
contained in a separate text header file, located in the same directory as the image
file. The header file uses the same name as the image file, with the file extension
.hdr. If ENVI locates the header file, it opens the file and adds it to the Available
Bands List.
If you open an image file directly from a CD, ENVI saves the header file to the
directory designated in the Alternate Header Directory preference.
If ENVI cannot find the header file or other valid header information when you open
a file, the Header Info dialog appears for you to enter information that creates the
header file.
Figure 5-1: Header Info Dialog
You must enter the required information to create a header file before ENVI can
display the image. Some header information is required, while other information is
optional. You can import header information an existing header file, or you can enter
the information directly in the Header Info dialog.
Getting Started with ENVI
Creating Header Files
124
Chapter 5: Working with Header Files
Required header information is:
•
Number of samples or pixels
•
Number of lines
•
Number of bands
•
Offset in bytes from the start of the file to where the data begins
•
File type
•
Byte order
•
Data type
•
Storage order
Optional header information includes:
•
Default Z Plot range
•
Default stretch for display
•
Georeferencing information
•
Associated wavelengths and associated FWHM (full-width-half-maximum)
values
•
Sensor type
•
Band names
•
Bad bands
Importing Header Information from Other Files
To import header information from one file into the header of the current file:
1. In the Header Info dialog menu bar, click Input Header Info From and select
Other File. The Select File for Header Input dialog appears.
2. Select the file containing the header information.
3. Click OK. The Header Info dialog re-appears.
4. Click OK. ENVI adds the header information to the file. If the image file was
open in a display group, ENVI closes that display group. Re-open the image
from the Available Bands List.
Creating Header Files
Getting Started with ENVI
Chapter 5: Working with Header Files
125
Entering Required Header Information
Use caution when setting the required header parameters for files not in the ENVI file
format. For example, changing the data type of an image in HDF format does not
affect the data type of the displayed or returned data; the HDF format overrides any
settings you add or change. To change the data type of an HDF image, first save the
data to an ENVI file (see “Saving as Standard ENVI Files” on page 168), then change
the data type. This is also true for many external format files opened in ENVI.
In the Header Info dialog, set the following required parameters, which are described
in the table for “The ENVI Header Format” on page 114:
•
Samples: See samples.
•
Lines: See lines.
•
Bands: See bands.
•
Offset: See header offset.
•
File Type: See file type.
•
xstart/ystart: See x start and y start.
•
Data Type: See data type.
•
Byte Order: See byte order.
•
Interleave: See interleave.
•
Use the text field at the bottom of the dialog to describe the data file (see
description).
Entering Optional Header Information
ENVI headers may have associated ancillary information (band names, spectral
library names, wavelengths, bad bands list, FWHM) depending on the image data
type.
Getting Started with ENVI
Creating Header Files
126
Chapter 5: Working with Header Files
In the Header Info dialog, click Edit Attributes and select the desired option to edit
optional header information. For more information on editing optional header
information, see Entering Optional Header Information in the ENVI User’s Guide.
Figure 5-2: Header Info Dialog – Edit Attributes Options
Creating Header Files
Getting Started with ENVI
Chapter 5: Working with Header Files
127
Editing Header Files
1. Open the header file with one of the following:
•
From the ENVI main menu bar, select File → Edit ENVI Header, select
the image filename from the Edit Header Input File dialog, then click OK.
The Header Info dialog appears.
•
From the Available Files List, right-click on the filename and select Edit
Header. The Header Info dialog appears.
2. Modify required header information as described in “Entering Required
Header Information” on page 125. Modify optional header information as
described in Entering Optional Header Information in the ENVI User’s Guide.
3. When the edits are complete, click OK in the Header Info dialog.
Note
If you edit the header of a file that is currently open, ENVI closes that file
and re-opens it when you click OK in the Header Info dialog. Because the
display groups using that file close when the file closes, you must restart
those displays from the Available Bands List.
Getting Started with ENVI
Editing Header Files
128
Chapter 5: Working with Header Files
ENVI File Type File
The menu\filetype.txt is an ASCII file that specifies the file types available in
the Header Info dialog File Type drop-down list. Using the File Type field in the
Header Info dialog allows image files to have an ENVI header, but still exist in their
native formats. The file types include ENVI-specific files such as meta files,
classification results, virtual mosaics, spectral libraries, and FFT results. The file
types also include data-specific formats such as ADRG and AVHRR, TIFF, BMP,
ERDAS 8.x, and PCI files.
You can edit the filetype.txt file and add your own, user-defined file types. The
first {bracketed} entry contains the full file type name, the second entry contains an
abbreviated name to use in the Header Info dialog, and the third entry contains the
name of the routine used to read the data (see Creating Custom File Input in the ENVI
Programmer’s Guide).
The following is the default filetype.txt file included in your ENVI installation.
{ACRES CEOS} {ACRES CEOS} {envi_acres_read_ceos}
{ADRG} {ADRG} {envi_read_adrg}
{AVHRR CD} {AVHRR} {envi_read_avhrr}
{BMP} {BMP} {envi_read_bmp}
{CEOS Generic} {CEOS} {envi_read_ceos}
{COSMO-SkyMed} {COSMO-SkyMed} {envi_read_cosmoskymed}
{ECW} {ECW} {envi_read_ecw}
{ENVISAT} {ENVISAT} {envi_read_envisat}
{ERDAS 8.X} {ERDAS 8.X} {envi_read_erdas}
{ERDAS IMAGINE} {ERDAS IMAGINE} {envi_read_erdas}
{ESA Landsat TM} {ESA TM} {envi_read_esa_tm}
{ESA SHARP} {ESA SHARP} {envi_read_esa_sharp}
{ESRI GRID} {ESRI GRID} {envi_read_grid}
{HDF EOS ASTER} {HDF ASTER} {envi_read_aster}
{HDF EOS MODIS} {HDF MODIS} {envi_read_modis}
{HDF Landsat} {HDF Landsat} {envi_read_landsat_hdf}
{HDF Modis Simulator} {HDF MAS-50} {envi_read_mas50}
{HDF Scientific Data} {HDF SD} {envi_read_hdf_sd}
{HDF SeaWiFS} {HDF SeaWiFS} {envi_read_seawifs_hdf}
{JPEG2000} {JPEG2000} {envi_read_jpeg2000}
{KOMPSAT-2} {KOMPSAT-2} {envi_read_kompsat2}
{MrSID} {MRSID} {envi_read_mrsid}
{NITF} {NITF} {envi_read_nitf}
{NLAPS CD} {NLAPS} {envi_read_nlaps}
{NOAA DMSP} {NOAA DMSP} {envi_read_dmsp}
{PCI} {PCI} {envi_read_pci}
{PDS Image} {PDS Image} {envi_read_pds}
{RADARSAT} {RADARSAT} {envi_read_radarsat}
{RapidEye} {RapidEye} {envi_read_rapideye}
ENVI File Type File
Getting Started with ENVI
Chapter 5: Working with Header Files
129
{SPOT CD} {SPOT} {envi_read_spot}
{TIFF} {TIFF} {envi_read_tiff}
{Tiled QuickBird} {Tiled QB} {envi_mosaic_tiled_qb_product}
{Tiled WorldView} {Tiled WV} {envi_mosaic_tiled_wv_product}
{TFRD} {TFRD} {envi_read_tfrd}
{Zoom} {ENVI Zoom} {envi_read_zoom}
Getting Started with ENVI
ENVI File Type File
130
Chapter 5: Working with Header Files
ENVI Sensor File
This menu\sensor.txt file is an ASCII file that lists sensor types that you can
select in the sensor parameter in an ENVI header. You can modify or add new sensors
to the list using any text editor. The sensor list is shown here:
AATSR
ADAR
ADEOS
ADRG
Air Photo
AIRSAR
AISA
ALOS
ASAR
ASTER
AVHRR
AVIRIS
CARTOSAT-1
CASI
COSMO-SkyMed
DMSP
QuickBird
EROS
ERS
FORMOSAT-2
GER63
GeoEye-1
GEOSCAN
HYDICE
HyMap
Hyperion
IKONOS
IRS LISSIII
IRS Pan
IRS WIFS
JERS-1
KOMPSAT-2
Landsat ETM
Landsat MSS
Landsat TM
MAS
MASTER
MERIS
MIVIS
MODIS
MOMS-02
ENVI Sensor File
Getting Started with ENVI
Chapter 5: Working with Header Files
131
OrbView-3
RADARSAT-1
RADARSAT-2
RapidEye
Scanned Image
SEAWIFS
SEBASS
SIR-C
SPIN-2
SPOT
TIMS
TMS
TRWIS III
USGS DEM
WorldView
X-SAR
Sensor types specified in the header file must match an entry in this list verbatim,
including case.
Getting Started with ENVI
ENVI Sensor File
132
ENVI Sensor File
Chapter 5: Working with Header Files
Getting Started with ENVI
Chapter 6
Common Tools and
Functions in ENVI
This chapter describes how to work with the basic components of ENVI. It includes:
Working with ENVI Dialogs . . . . . . . . . . .
Selecting Bands or Files for Processing . .
ENVI Processing Status Window . . . . . . .
Showing Display Group Information . . . .
Displaying Pixel Location . . . . . . . . . . . . .
Displaying Cursor Location/Value . . . . . .
Getting Started with ENVI
134
143
147
148
149
151
Collecting Points . . . . . . . . . . . . . . . . . . .
Linking Display Groups . . . . . . . . . . . . . .
Using Dynamic Overlays . . . . . . . . . . . . .
Annotating Displays . . . . . . . . . . . . . . . . .
Defining Regions of Interest . . . . . . . . . .
Using the Available Files List . . . . . . . . .
154
155
156
157
159
162
133
134
Chapter 6: Common Tools and Functions in ENVI
Working with ENVI Dialogs
This section describes common options and functions in ENVI dialogs, as well as
some common dialogs you may encounter when using ENVI.
ENVI Dialog Components
The following components are mentioned in procedures throughout the ENVI
documentation:
Component
Description
Button. Click to access another dialog.
Drop-down button. Click and select the desired
option from the resulting menu.
Radio button. Click on the desired option. You
may select only one option at a time.
Drop-down list. Click the arrow to open a list and
select from multiple choices.
Sliders. Slide the bar back or forth, or click on
either arrow, to set the value from a continuous
range of possible values.
Field. Type the desired value. In some cases, such
as file or directory selection, a Choose button
accompanies the field. You can optionally click
Choose, navigate to the desired file or directory,
and select the value to populate the field.
Table 6-1: Basic Dialog Component Descriptions
Working with ENVI Dialogs
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
Component
135
Description
Increase/decrease buttons. Click on either arrow to
increase or decrease the value. Increase/decrease
buttons typically include a field into which you
can optionally type the value.
Toggle buttons. Click the button to alternate
between two choices and select the desired value.
Color button. Left-click on the color button to
cycle forward through the color choices, middleclick to cycle backward through the color choices,
or right-click and select a color from the resulting
menu.
Check box. Select (or clear) one or more check
boxes as needed to enable (or disable) one or more
options. In some ENVI dialogs, selecting a check
box causes additional fields to appear on the
dialog.
Some ENVI menus provide options that you can
toggle between. Select one item from a menu as
needed to enable an option; a check mark appears
next to the selected item. You may enable only
one option at a time.
Table 6-1: Basic Dialog Component Descriptions (Continued)
Getting Started with ENVI
Working with ENVI Dialogs
136
Chapter 6: Common Tools and Functions in ENVI
The Input File Dialog
Before you apply any of ENVI’s processing capabilities to a specific data set, you
must first select the file containing the data to process. Nearly every ENVI image
processing function displays a standard Input File dialog. From the Input File dialog,
you can select an input file or a single band for processing, perform spatial or spectral
subsetting, and, in some cases, mask the input data. When file selection is complete,
ENVI proceeds with processing or prompts you for additional settings.
The title of the Input File dialog changes to reflect the function you select. For
example, Figure 6-1 shows Global Spatial Statistics Input File in the title bar, whereas
the Input File dialog for stretching data would show Data Stretch Input File in the title
bar.
The dialog options vary depending on whether you choose to select input by a file
(Figure 6-1), or by the bands within the file (Figure 6-2).
Title varies by selected function
Figure 6-1: Input Selection by File
Working with ENVI Dialogs
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
137
Details about how to use the Input File dialog are in “Selecting Bands or Files for
Processing” on page 143.
Figure 6-2: Input Selection by Band
Getting Started with ENVI
Working with ENVI Dialogs
138
Chapter 6: Common Tools and Functions in ENVI
Selecting Multiple Items in Lists
Some ENVI dialogs contain lists from which you select a filename or option. In some
of those lists you can select more than one item, either consecutively or randomly.
Figure 6-3: Selecting Individual and Multiple Items in a Dialog
Selecting Items
To select multiple files that are listed consecutively, do one of the following:
•
Select the first file in the group, press and hold the Shift key, and select the last
file in the group.
•
Left-click and hold the button down, and drag the cursor over the group of
items. The items are selected when they are highlighted.
•
If the dialog you are working in has a Select All Items button, click the button
to select all of the items in the list.
To select multiple files that are not listed consecutively, press and hold the Ctrl key
on your keyboard and select each desired file.
Working with ENVI Dialogs
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
139
De-Selecting Items
To de-select a single item, hold the Ctrl key down and click on the item.
To de-select multiple items, click on a single item to de-select all items except the one
you just clicked on.
If the dialog you are working in has a Clear All Items or Clear or Deselect button,
click it to de-select all of the items in the list.
Selecting Output to File or Memory
For most functions, ENVI offers the option of either writing image processing results
to a File or to Memory. If your machine has a large amount of random access
memory (RAM), it can efficiently process images without repeatedly having to store
intermediate processing results in disk files, which makes storing results in memory
feasible.
Saving an image to memory saves it in your computer’s system memory and adds the
file to the Available Bands List or the Available Vectors List for later display. When
you close ENVI, the image is deleted. Saving an image to a file saves the image to
your computer’s hard drive, and adds it to the Available Bands List or the Available
Vectors List for later display. When you close ENVI, the file is retained on your
machine for reuse in future ENVI sessions.
Figure 6-4: File or Memory Output Option
Getting Started with ENVI
Working with ENVI Dialogs
140
Chapter 6: Common Tools and Functions in ENVI
To select the output type:
1. In any dialog where you have the option to specify output, select either:
•
File
•
Memory
2. If you select File, either:
•
Type the output filename in the Enter Output Filename field.
•
Click Choose to select an output filename.
Queuing ENVI Processes
Some ENVI dialogs include a Queue button, which enables you to prepare multiple
functions in advance for processing, but queue them for processing at a later time.
Queuing functions are useful when their processing time is lengthy.
Note
Results from one queued function (procedure) cannot be used as input into another
function.
When queuing is available in a dialog:
1. Set all dialog parameters as needed.
2. Select output to File and enter a filename.
3. Click Queue instead of clicking OK. This places the function in the ENVI
Queue Manager.
4. When you are ready to process that function, either on its own or with other
queued functions, start it from the ENVI Queue Manager, described next.
Figure 6-5: Queue Button
To process queued functions:
1. Ensure that all of the files needed to run the queued functions are open and
listed in the Available Bands List.
Working with ENVI Dialogs
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
141
2. From the ENVI main menu bar, select File → ENVI Queue Manager. The
ENVI Queue Manager dialog displays, with a list of all queued functions.
Figure 6-6: ENVI Queue Manager Dialog
3. In the Queued Procedures List, select one or more procedures to run. To
select all of the procedures, click Select All.
To view information about a procedure in the Procedure Information field,
click on the procedure name.
4. Click Execute Selected. ENVI removes the names from the list and processes
the functions. The resulting filenames appear in the Available Bands List.
Compressing Output
Some ENVI dialogs include a Compress check box. When you select the check box,
it prompts ENVI to compress your output. This check box is only available in
functions that output files sequentially. ENVI applies a lossless GZIP format
compression to the output file. When a you open compressed file, ENVI reads the file
and un-compresses it on-the-fly.
Getting Started with ENVI
Working with ENVI Dialogs
142
Chapter 6: Common Tools and Functions in ENVI
Note
Compressed files are slower to output and input than un-compressed files.
Be aware that ENVI cannot read compressed files that are larger than 2 GB. If you
compress a large file and it remains larger than 2 GB when compressed, you cannot
read it with ENVI.
To compress an output a file, select the Compress check box if it is available in the
dialog, then click OK.
Closing Dialog Windows
Dialogs in ENVI include a Cancel option, which closes the dialog. On some ENVI
dialogs, this option is accessible from the menu bar of the dialog by selecting File →
Cancel, while on other dialogs you can click a Cancel button at the bottom of the
dialog.
When you select the Cancel option, ENVI closes the active dialog and does not save
or process any of the settings you chose during the time the dialog was open.
Figure 6-7: Cancel Option from the File Menu (left) and as a Dialog Button (right)
Working with ENVI Dialogs
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
143
Selecting Bands or Files for Processing
1. From any ENVI menu, select the tool you want to use. The Input File dialog
appears (see “The Input File Dialog” on page 136).
2. Click the Select By toggle button to select File or Band input.
3. Select the desired file or band name from the Select Input File or Select Input
Band column.
If the Select By area is set to File, you can optionally subset the input by
clicking Spatial Subset or Spectral Subset and using the standard subsetting
procedures (see “Selecting a Spatial Subset” on page 143 or “Selecting a
Spectral Subset” on page 145).
4. To start the selected function, without selecting any subsetting, either:
•
Double-click on the selected file or band name.
•
Click OK.
Selecting a Spatial Subset
Use spatial subsetting to limit applying a function to a spatial subset of the image. For
subsetting by spectral bands instead of by spatial regions, see “Selecting a Spectral
Subset” on page 145. You can select spatial subsets by using the following methods:
•
Entering samples and line values.
•
Selecting interactively from the image.
•
Entering map coordinates.
•
Using the same spatial subset that was previously used on another file.
•
Using the image shown in the meta scroll window.
•
Using the bounding box around a region of interest.
Getting Started with ENVI
Selecting Bands or Files for Processing
144
Chapter 6: Common Tools and Functions in ENVI
The options in the Spatial Subset dialog vary depending on whether the current data
are sample-line-based or georeferenced. Additionally, if the same image is open in
more than one display group, you can specify which display number to apply the
subset to.
Figure 6-8: Spatial Subset Dialog
See the following topics in ENVI Help for detailed information:
•
Subsetting by Samples/Lines
•
Subsetting by Images
•
Subsetting by Map Coordinates
•
Subsetting Using Another File’s Subset
•
Subsetting Using ROIs
•
Subsetting by Scroll Window
Selecting Bands or Files for Processing
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
145
Selecting a Spectral Subset
Use spectral subsetting to limit application of a function to selected bands of an
image. For subsetting by spatial regions instead of spectral bands, see “Selecting a
Spatial Subset” on page 143.
Figure 6-9: File Spectral Subset Dialog
See the following topics in ENVI Help for detailed information:
•
Subsetting by Bands
•
Subsetting Using Previous Subsets
•
Subsetting by Ranges
•
Subsetting from an ASCII File
Selecting a Mask
Certain ENVI functions allow spatial masking before processing. These functions
include:
•
Statistics
•
Classification
•
Un-mixing
•
Matched filtering
Getting Started with ENVI
Selecting Bands or Files for Processing
146
Chapter 6: Common Tools and Functions in ENVI
•
Continuum removal
•
Spectral feature fitting
When you select a file to process, you can apply a previously defined spatial mask.
When you use a mask, ENVI does not apply the selected function to the masked
portion of the image. You can build a spatial mask from data ranges, regions of
interest (ROIs), and other types of input.
Figure 6-10: Select Mask Input Band Dialog
See the following topics in ENVI Help for detailed information:
•
Building Masks
•
Masking Options
•
Masking
Selecting Bands or Files for Processing
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
147
ENVI Processing Status Window
Most ENVI functions report the processing status in a window as calculations
proceed, The status window appears immediately after processing begins. The status
window shows:
•
The function being processed in the title bar.
•
Whether the results are being placed in memory or in an output file.
•
A percent complete progress bar, which updates as ENVI processes data.
•
The size of each data increment processed, based on the tile size (see “Image
Tile Size” on page 1161). The function automatically determines the size of
the processing increment.
Figure 6-11: Processing Status Window for Output to File (above) and Output to
Memory (below)
Use the Cancel button to terminate processing if the increment is less than 100%. If
the increment is equal to 100%, interruption of the function is not possible.
Getting Started with ENVI
ENVI Processing Status Window
148
Chapter 6: Common Tools and Functions in ENVI
Showing Display Group Information
Use Display Information to view information about the display group in which the
cursor is currently located. The information is updated as you move the cursor
between the open display group windows. The Display Information window shows:
•
Display number.
•
Number of colors used.
•
Bands displayed.
•
Type of stretch currently applied to each band.
•
Sizes and pixel ranges of the Image, Zoom, and Scroll windows.
To show display information, select one of the following options:
•
From the ENVI main menu bar, select Window → Display Information.
•
From the Display group menu bar, select Window → Display Information.
The Display Information window appears.
Figure 6-12: Display Information Window
Showing Display Group Information
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
149
Displaying Pixel Location
Use the Pixel Locator to manually enter a sample and line location that positions the
cursor at the center of the Zoom window. If the image contains georeferenced data,
you can optionally locate pixels using map coordinates. The Pixel Locator pertains to
the display group from which it was opened. You can open a Pixel Locator for each
display group shown on your screen.
1. To open the pixel locator, use one of the following:
•
From the Display group menu bar, select Window → Pixel Locator.
•
In the display group, right-click and select Pixel Locator.
The Pixel Locator dialog appears, showing the values of the selected pixel. If
the image contains an associated DEM, elevation information displays as well.
In the Zoom window, crosshairs outline the selected pixel.
Figure 6-13: Pixel Locator Dialog
2. If the image header contains x start and y start data, specify whether to
use an image offset by enabling or disabling Options → Use Image Offset
from the Pixel Locator dialog menu bar. The default is Yes. If the header file
does not contain x start and y start data, this option is unavailable.
Getting Started with ENVI
Displaying Pixel Location
150
Chapter 6: Common Tools and Functions in ENVI
3. To locate a pixel, either:
•
Enter a Sample (horizontal) and Line (vertical) location into the
corresponding fields and click Apply. The Zoom box jumps to the
specified pixel location.
•
To move the selected pixel one pixel at a time, click the arrow buttons at
the bottom of the Pixel Locator dialog.
•
If the displayed image is georeferenced, click the Proj toggle button to
choose between map coordinates and geographic coordinates
(latitude/longitude), enter the desired easting (E) and northing (N) or
latitude and longitude, and click Apply. The Zoom box jumps to the
specified pixel location.
4. If ENVI’s image-to-map registration function is active, click Export to deliver
map coordinates (including elevation, if available) to the Ground Control
Points Selection dialog (see Image-to-Map Ground Control Points in the ENVI
User’s Guide).
The Export button produces no effect if a registration session is not active.
Displaying Pixel Location
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
151
Displaying Cursor Location/Value
Use the Cursor Location/Value tool in any display group to display the sample
(horizontal, x) and line (vertical, y) coordinates, the data value of the pixel under the
cursor, and the geographic coordinates (for georeferenced data) of the pixel under the
cursor. The position is continuously updated as you move the cursor around the
image.
Note
For complex data, the Cursor Location/Value tool reports the real and imaginary
components.
To open the Cursor Location/Value window, use one of the following:
•
In the display group, double-left-click.
•
In the display group, right-click and select Cursor Location/Value.
•
From the Display group menu bar, select Tools → Cursor Location/Value.
•
From the Display group menu bar, select Window → Cursor Location/Value.
•
From the ENVI main menu bar, select Window → Cursor Location/Value.
The Cursor Location/Value window appears.
Note
In ENVI, pixel values always refer to the upper-left corner of the pixel. Map
coordinates also typically refer to the upper-left corner of the pixel. However, if you
entered image pixel coordinates in the map information in the ENVI header, the
map coordinates would refer to the x,y coordinates entered (for example, x=1.5,
y=1.5 would make the map coordinates refer to the center of the pixel).
The Cursor Location/Value window applies to all open display groups. When you
move the cursor from one display group to another, the window shows information
for the display group the cursor is over. The Cursor Location/Value window displays
the following data:
•
For all images: The display group number and stretched image (Scrn) and raw
data (Data) values.
•
For RGB images: The red, green, and blue values for the displayed bands.
•
For georeferenced images: The appropriate projection name, the map
coordinates, and latitude and longitude.
Getting Started with ENVI
Displaying Cursor Location/Value
152
Chapter 6: Common Tools and Functions in ENVI
•
For classification images: The class names, along with the cursor location and
value.
•
For linked displays: The data values for the current pixel for all the linked
display groups.
Figure 6-14: Cursor Location/Value Dialog for UTM Coordinates (left) and a
Georeferenced Image (right)
Cursor Location/Value Reporting Options
You can specify how you want the Cursor Location/Value window to report
information. For example, you can report the cursor location in the Zoom window as
an integer number or as a floating-point number, show fractions of a pixel, change the
displayed format of the latitude and longitude information, and set the precision of
the numbers reported (the number of digits displayed after the decimal). The upperleft-corner of a pixel is the position of the whole number coordinates and the x and y
values increase to the right and bottom of the pixel, respectively. The pixel fraction is
shown proportional to the zoom factor. For example, at a zoom of 4x, the pixels are
divided into fourths. The values reported for the Zoom window are from the original
data, not the interpolated data.
To set cursor/location value options from the from the Cursor Location/Value window
menu bar:
•
To view floating-point pixel image locations in the Zoom window, select
Options → Floating Point Locations.
•
To view integer pixel image locations in the Zoom window, deselect
Options → Floating Point Locations.
•
To view pixel locations, including the x and y offset values read from the
header, select Options → Use Image Offset. This is the default selection.
Displaying Cursor Location/Value
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
153
•
For georeferenced data sets: To view latitude and longitude information in
decimal degrees, deselect Options → Lat/Lon DDS.
•
To view latitude and longitude information in degrees, minutes, and seconds,
select Options → Lat/Lon DMS (for georeferenced data sets). This is the
default selection.
•
By default, the Cursor Location/Value window is set to move to front of all
other windows when opened, to disable this option, deselect Options → Auto
Raise Window.
Setting Numeric Precision
The numeric precision is the number of digits displayed after the decimal.
1. In the Cursor Location/Value window menu bar, select Options → Set Report
Precision. The Set Report Precision dialog appears.
2. To set the precision to use to display the map coordinates, enter the value in the
Map Precision field.
3. To set the precision of the display when Lat/Lon:DD is the selected option for
georeferenced data sets, enter the value in the Lat/Lon Precision field.
4. To set the precision to use to display the floating point data values, enter the
value in the Data Precision field. Any changes do not affect the display of byte
and integer data.
5. Select Scientific or Normal as the Floating Report format, from the toggle
button. A normal number is the number in decimal format (for example,
25.88), whereas a scientific number shows a single digit, followed by a
decimal, and e (exponential) power (for example, 2.588e+001).
6. Click OK.
Getting Started with ENVI
Displaying Cursor Location/Value
154
Chapter 6: Common Tools and Functions in ENVI
Collecting Points
Use the Point Collection tool to collects points (both pixel locations and map
locations) from display group windows. The points display in a table in the ENVI
Point Collection window.
To collect points, use one of the following:
•
From the ENVI main menu bar, select Window → Point Collection.
•
From the Display group menu bar, select Tools → Point Collection.
For detailed information and instructions about collecting points, see Collecting
Points in the ENVI User’s Guide.
Collecting Points
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
155
Linking Display Groups
You can link multiple display groups so that all actions in one display are mirrored in
all other linked display group windows. For example moving the Zoom box in the
Image window or the Image box in the Scroll window, changing the zoom factor, or
resizing one Image window in one display group is mirrored in another, linked
display group. Ideally, you should only link images when they are the same size, or
when one image is a subset of the other image. Dynamic overlays are active when
displays are linked.
To link display groups, use one of the following:
•
From the ENVI main menu bar, select Window → Link Displays.
•
From the Display group menu bar, select Tools → Link → Link Displays.
•
In the display group, right-click and select Link Displays.
The Link Displays dialog appears.
See Linking Displays in the ENVI User’s Guide for details on using the Link
Displays dialog.
Getting Started with ENVI
Linking Display Groups
156
Chapter 6: Common Tools and Functions in ENVI
Using Dynamic Overlays
You can use dynamic overlays for real-time overlay, and to toggle (flicker) multiple
gray scale or color images. By default, dynamic overlays are activated automatically
when two or more windows are first linked. Multiple overlays are active in all linked
Image windows simultaneously and in each Zoom window.
1. To use multiple dynamic overlays, use one of the following:
•
From the ENVI main menu bar, select Window → Link Displays.
•
From the Display group menu bar, select Tools → Link → Link Displays.
•
In the display group, right-click and select Link Displays.
2. Link the displays as described in Linking Displays in the ENVI User’s Guide.
3. When the displays are linked, you can use the Dynamic Overlay option to
select On and Off using the following Image window menu bar selections:
•
Select Tools → Link → Dynamic Overlay On
•
Select Tools → Link → Dynamic Overlay Off
See Working with Multiple Dynamic Overlays in the ENVI User’s Guide for
complete details on using the multiple dynamic overlays.
Using Dynamic Overlays
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
157
Annotating Displays
You can annotate images and plots with text, symbols, polygons, lines, polylines,
shapes, map information, and gray scale or color bars. For classification images, you
can also add class keys. For display groups, you can place annotations in the Image
window, the Scroll window, the Zoom window, or in the virtual borders.
Annotation options are similar for images, plots or, surface views. You can save
annotations to files and include them in output options.
You can also use the QuickMap tool to overlay grid lines, titles, declination
diagrams, North arrows, and borders on georeferenced images. See Creating
QuickMaps in the ENVI User’s Guide.
Figure 6-15: Example Annotation in a Display Group
To use virtual borders, append the border to the image before annotating it (see
Setting Virtual Display Borders in the ENVI User’s Guide).
Getting Started with ENVI
Annotating Displays
158
Chapter 6: Common Tools and Functions in ENVI
To create annotations:
1. Select one of the following options:
•
From the Display group menu bar select Overlay → Annotation.
•
From any plot menu bar, including surface plots and x, y, or z profiles,
select Options → Annotation.
The Annotation dialog appears.
2. Select Object → annotation_type. Text annotation is the default mode.
For details on annotation, see Annotating Images and Plots in the ENVI User’s
Guide.
Annotating Displays
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
159
Defining Regions of Interest
Regions of interest (ROIs) are portions of images, either selected graphically or
selected by other means, such as thresholding. Typical uses of ROIs include
extracting statistics for classification, masking, and other functions. You can use any
combination of polygons, points, or vectors as an ROI. ENVI allows you to define
multiple ROIs and draw them in any of the Image, Scroll, or Zoom windows. In
addition, you can grow ROIs to adjacent pixels that fall within a specified pixel value
threshold.
Figure 6-16: ROIs in the Display Group
Getting Started with ENVI
Defining Regions of Interest
160
Chapter 6: Common Tools and Functions in ENVI
Note
ROIs are explicitly related to the spatial size of the image in which they are defined.
If you open images of equal spatial size with their associated ROI Tool dialogs,
ROIs drawn in one image are displayed in all other image displays of the same
spatial size. You can edit or delete shared ROIs from within any of the ROI Tool
dialogs.
To draw an ROI:
1. Select one of the following options for the active display group:
•
From the Display group menu bar, select Overlay → Region of Interest.
•
From the Display group menu bar, select Tools → Region of Interest →
ROI Tool.
•
From the ENVI main menu bar, select Basic Tools → Region of Interest →
ROI Tool.
•
In the display group, right-click and select ROI Tool.
The ROI Tool dialog appears.
Figure 6-17: ROI Tool Dialog
Defining Regions of Interest
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
161
2. Select whether to use the Image, Scroll, or Zoom window to draw the ROIs.
3. Draw ROIs as described in Drawing ROIs in the ENVI User’s Guide.
You can also add, edit, and create additional ROIs, as described in ENVI Help.
Turning Off ROI Definition
When the ROI Definition function is enabled, actions such as zooming, panning and
other display operations are not enabled.
To enable these interactive mouse operated functions without leaving ROI Definition,
select the Off radio button in the ROI Tool dialog.
Getting Started with ENVI
Defining Regions of Interest
162
Chapter 6: Common Tools and Functions in ENVI
Using the Available Files List
Use the Available Files List to view information about the files that are currently open
in ENVI and in memory. You can also use the Available Files List to open new files,
to close files, to save memory items to disk, and to edit ENVI headers.
Tip
Use the Available Files List on a regular basis to remove memory-only calculations
from system memory.
To open the Available Files List, use one of the following:
•
From the ENVI main menu bar, select Window → Available Files List.
•
From the Available Bands List menu bar, select File → Available Files List.
The Available Files List appears.
Figure 6-18: Available Files List
Using the Available Files List
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
163
Viewing File Information
To view important information about each file, select a filename in the Available Files
List. ENVI displays information and parameters from the ENVI header file,
including:
•
Full path and image name.
•
Number of lines, samples, and bands (Dims).
•
File size.
•
Interleave (BSQ, BIL, BIP).
•
Data type (byte, integer, and so forth).
•
File type.
•
Byte order of the data (Host or Network).
•
Whether or not the data is georeferenced.
•
Whether or not any wavelengths are associated with the bands.
Editing Header Files from the Available Files List
You can edit header files from the Available Files List. For details, see “Editing
Header Files” on page 127.
Opening New Files from the Available Files List
You can open ENVI image files or other binary image files of known format. For
details, see “Opening Image Files in ENVI” on page 82.
ENVI opens the file and adds it to the Available Files List. The file information
appears in the right side of the dialog.
Closing All Files from the Available Files List
To close all files (including memory items, which are automatically deleted), select
File → Close All Files from the Available Files List menu bar.
Getting Started with ENVI
Using the Available Files List
164
Chapter 6: Common Tools and Functions in ENVI
Deleting Memory Items
To remove files that exist only in memory without closing open disk files, select
File → Delete All Memory Items from the Available Files List menu bar.
Note
Memory items removed in this fashion are not recoverable.
Storing Files in Memory
To store large image files as an in-memory item for faster processing:
Note
This option is dependent on the amount of RAM available on your system.
1. Select one or more filenames in the Available Files List.
2. From the Available Files List menu bar, select File → Add Selected Files to
Memory. All selected image files, including their parameters, are added as inmemory items to the Available Bands List.
Saving In-Memory Files to Disk
1. Select the item to save in the Available Files List.
2. From the Available Files List menu bar, select File → Save Selected File to
Disk. The Memory to File Storage dialog appears.
3. Enter an output filename.
4. Click OK.
Deleting Files from Disk
1. Select the file(s) to delete in the Available Files List.
2. Select File → Delete Selected File from Disk. Because this is a permanent
action, a warning message appears to verify that you want to permanently
delete the file.
3. Click Yes to delete the file.
Using the Available Files List
Getting Started with ENVI
Chapter 6: Common Tools and Functions in ENVI
165
Closing Selected Files
1. Select the file(s) to close in the Available Files List.
2. Select File → Close Selected File.
If a warning box appears, it means that one or more bands from the file are
currently displayed in one of the display groups. Select Yes to close the file and
to remove the associated bands from the display.
If the file is a memory item, ENVI removes it from memory and closes any
associated displays.
Getting Started with ENVI
Using the Available Files List
166
Using the Available Files List
Chapter 6: Common Tools and Functions in ENVI
Getting Started with ENVI
Chapter 7
Creating Output
This chapter describes creating various types of output in ENVI. It includes:
Saving Image Files . . . . . . . . . . . . . . . . . . 168
Saving Display Output . . . . . . . . . . . . . . . . 173
Getting Started with ENVI
Printing in ENVI . . . . . . . . . . . . . . . . . . . 174
Changing Output Directories . . . . . . . . . . 176
167
168
Chapter 7: Creating Output
Saving Image Files
Use Save File As to create a new standard ENVI disk file or an ENVI meta file from
bands contained in the Available Bands List and to output image data to various
image processing formats. You can create output to image processing formats such as
ArcView® Raster (.bil), ER Mapper, ERDAS IMAGINE (.img),
JPEG 2000 (.jp2), NITF (.ntf), PCI (.pix), TIFF (including GeoTIFF or world
files (.tfw)), and ESRI® GRID files. In addition, you can output your image to an
ASCII (.txt) file.
Note
You can only create new files from bands that have the same spatial dimensions.
Use ENVI’s subsetting capabilities to choose individual bands and to perform onthe-fly subsetting of files to the correct dimensions. See Subsetting Data in the
ENVI User’s Guide.
This section describes how to save data as standard ENVI files, meta files, and ASCII
files. For information on saving output to other image processing formats, see the
following topics in ENVI Help:
•
Saving Files as ArcView Raster Files
•
Selecting an Output Geodatabase
•
Saving Files as ER Mapper Files
•
Saving Files as IMAGINE Files
•
Saving Files as JPEG 2000 Files
•
Saving Files as NITF Files
•
Saving Files as PCI Files
•
Saving Files as TIFF Files
•
Saving Files as ESRI GRID Data
Saving as Standard ENVI Files
Use ENVI Standard to create disk files from a combination of ENVI files, external
(foreign) files, or memory items.
1. From the ENVI main menu bar, select File → Save File As → ENVI Standard.
The New File Builder dialog appears.
Saving Image Files
Getting Started with ENVI
Chapter 7: Creating Output
169
Figure 7-1: New File Builder Dialog
2. Click Import File. The Create New File Input File dialog appears.
3. Select one or more files to include and perform optional spatial subsetting and
spectral subsetting. You can subset a group of files if they are the same size;
the subset is applied to each file. For subsetting details, see Subsetting Data in
the ENVI User’s Guide.
Getting Started with ENVI
Saving Image Files
170
Chapter 7: Creating Output
4. Repeat the file selection using the Import File button for each input file to
include in the new file. Input files are listed in the Selected ENVI Files for
New File list.
•
To delete a file from the list in the New File Builder dialog, select the
filename and click Delete.
•
To change the order in which the files and/or bands are imported, click
Reorder Files to open the Reorder Files dialog, and click on a filename or
band name and drag it to the desired position in the list.
•
To remove the component files, use the Remove Superfluous Files?
toggle button to select Yes (remove files), or No, next to the text label.
Note
Removing component files physically removes the files from the Available
Bands List and the disk:
If transferring memory items to the new file and you select Remove
Superfluous Files?, the items are deleted from memory when the new file is
created.
If transferring all of the bands from a disk file to the new file and Remove
Superfluous Files? is selected, the original disk file is physically deleted
from the disk when the new file (either memory or disk file) is created.
5. Select output to File or Memory.
6. Click OK to build the new file. ENVI creates the file in BSQ format.
Saving as ENVI Meta Files
A meta file is a virtual file, in which no new disk file is actually created. Instead, you
associate files or image bands through a small text file, which contains the names of
the files to treat as a virtual file. When you later select the meta file for input or
processing, ENVI retrieves the image data from the individual disk files and treats
them as if they were part of the same input file for processing. ENVI meta files can
contain images with different data types (byte, integer, floating point, and so forth),
which allows you to combine processing of diverse data sets. ENVI does not need to
perform file conversions, and does not need to create intermediate processing files.
Saving Image Files
Getting Started with ENVI
Chapter 7: Creating Output
171
Note
Files to include in a meta file must reside on disk as ENVI format files. Convert
foreign files imported to ENVI (for example, TIFF files) or files/bands created as
memory items within ENVI to ENVI disk files before creating the meta file.
1. From the ENVI main menu bar, select File → Save File As → ENVI Meta. The
New File Builder dialog appears.
2. Click Import File. The Create New File Input File dialog appears.
3. Select one or more files to include and perform optional spatial subsetting and
spectral subsetting. You can subset a group of files if they are the same size;
the subset is applied to each file. For subsetting details, see Subsetting Data in
the ENVI User’s Guide.
4. Repeat the file selection using the Import File button for each input file to
include in the new file. Input files are listed in the Selected ENVI Files for
New File list.
•
To delete a file from the list in the New File Builder dialog, select the
filename and click Delete.
•
To change the order in which the files and/or bands are imported, click
Reorder Files to open the Reorder Files dialog, and click on a filename or
band name and drag it to the desired position in the list.
5. In the Enter Output Filename field, enter a filename.
6. Click OK to build the new file. ENVI adds the bands in the meta file to the
Available Bands List. The actual meta file, on disk, is a text file that only
contains the names of the imported files.
Saving as ASCII Files
ASCII (.txt) output files contain the DN values for every pixel. You may select the
output format of the DN values (field size including decimal point, white spaces, and
number of decimal places). If you output multiple bands, the file interleave (BSQ,
BIL, BIP) is the same as the input file. The format of the ASCII file is that of a 2D
array.
Note
If your output file contains three asterisks (***), then your ASCII output format is
incorrect for the data type of your DN values.
Getting Started with ENVI
Saving Image Files
172
Chapter 7: Creating Output
1. From the ENVI main menu bar, select File → Save File As → ASCII. The
Output File to ASCII Input Filename dialog appears.
2. Select a file and perform any subsetting.
3. Click OK. The Output to ASCII Parameters dialog appears.
4. Enter an integer value for Total Field Size to set the total number of characters
in the field.
5. To set the number of digits that follow the decimal point in the output data,
enter a value for Decimal Precision.
6. In the Enter Output Filename field, enter a filename.
7. Click OK. ENVI creates an output ASCII file, which you can view using any
text editor.
Saving DEMs to ASCII Format
If your input file is a DEM, the Output Style drop-down list appears in the Output to
ASCII Parameters dialog. Select an output format:
•
ENVI Standard: Output will be consistent with ENVI raster format, where
each data point represents the elevation (in meters) for the corresponding pixel.
•
ESRI ASCIIGRID: Output will be consistent with ESRI GRID format, where
each data point represents the elevation (in meters) for the corresponding pixel.
•
X Y Z: If you select this option, you must enter values for XY Field Size and
XY Decimal Precision. Output will contain a five-line header, followed by six
columns of data per line (two sets of x,y,z data side-by-side in one line, as in
the following example).
Saving Image Files
Getting Started with ENVI
Chapter 7: Creating Output
173
Saving Display Output
You can save ENVI display groups, plot windows, or Vector windows to PostScript
files, image files, or directly to printers. You can include (burn into) all overlays
(annotation, grid lines, vectors, and so forth) in the output.
The image file types you can save to are:
•
ENVI file (RGB binary image with an ASCII header file)
•
BMP
•
HDF
•
JPEG and JPEG 2000
•
PICT
•
Portable Network Graphics (PNG)
•
Sun Raster File (SRF)
•
TIFF (including GeoTIFF and TIFF World [.tfw])
•
X-Windows Dump (XWD)
•
ERDAS (.lan)
•
ER Mapper, PCI (.pix)
•
ArcView® (.bil) files
For detailed instruction on saving files and setting options for page size, image
scaling, graphics overlays, masks, and more, see Saving Images from Displays in the
ENVI User’s Guide.
Getting Started with ENVI
Saving Display Output
174
Chapter 7: Creating Output
Printing in ENVI
You can send output of display groups, plot windows, and Vector windows directly to
system printers. You can send output to any of your system printers or plotters
through your native system printer dialog.
1. Select one of the following options:
•
To output a displayed image to a system printer, select File → Print from
the Display group menu bar.
•
To output a plot or Vector window to a system printer, select File → Print
from the plot or Vector window menu bar.
The Print dialog appears.
2. Set any options specific to your system.
3. Click OK. The Output Display to Printer dialog appears.
4. If the image is georeferenced, you can set the output x or y print size or set the
desired output map scale in the xsize and ysize fields. When you set a size, the
other size parameters change to preserve the aspect ratio of your image.
Note
To maintain the relative aspect between x and y when one dimension is
changed, select the Aspect check box.
5. Set the position of the image origin on the page (with respect to the lower left
corner) using the xoff and yoff parameters. An outline of the image showing its
relative size and position on the page appears within the draw window in the
upper-right of the dialog.
•
To position the image on the output page, left-click and hold the mouse
button inside the image outline in the draw window and drag the image to a
new position.
•
To center the image outline on the page using your mouse, right-click
anywhere on the output page.
6. Click the toggle button to select Landscape or Portrait page orientation.
7. To scale an image to a specified map scale, enter a value in the Map Scale 1
field. The xsize and ysize field values change automatically based on the image
pixel size (ENVI uses a default size of 30 meters no pixel size is present in the
header).
Printing in ENVI
Getting Started with ENVI
Chapter 7: Creating Output
175
8. If desired, perform optional spatial subsetting and spectral subsetting. For
subsetting details, see Subsetting Data in the ENVI User’s Guide.
9. To resize the image, enter a resize factor (less than 1 for subsampling) in the
Input Image Resize Factor field.
10. To set graphics overlay options, see Setting Graphics Overlay Options in the
ENVI User’s Guide.
11. Click OK in the Output Display to Printer dialog to print the image or plot.
Getting Started with ENVI
Printing in ENVI
176
Chapter 7: Creating Output
Changing Output Directories
You can change the output directory for the current ENVI session. To change the
default ENVI directory for all ENVI sessions, see Default Directory Preference
Settings in the ENVI User’s Guide.
1. From the ENVI main menu bar, select File → Change Output Directory. The
Change Output Directory dialog appears.
2. Enter the full path of the directory to which you want ENVI to send the output.
3. Click OK to change the current output directory to the new path.
Changing Output Directories
Getting Started with ENVI
Chapter 8
Configuring and
Customizing ENVI
This chapter describes how to set ENVI preferences and how to customize your ENVI installation.
It includes:
Setting ENVI Preferences . . . . . . . . . . . . . 178
Customizing ENVI . . . . . . . . . . . . . . . . . . 188
Getting Started with ENVI
Using IDL with ENVI . . . . . . . . . . . . . . . 196
177
178
Chapter 8: Configuring and Customizing ENVI
Setting ENVI Preferences
ENVI is installed with system defaults that control a variety of system preferences.
You change these settings through the ENVI interface, or by editing the ENVI
configuration file (menu\envi.cfg) in a text editor.
To set ENVI preferences in the ENVI interface:
1. From the ENVI main menu bar, select File → Preferences. The System
Preferences dialog appears with the parameters to set located under various
tabs.
2. Click on the tab category that you want to modify. The dialog options change
depending on the tab you select. The tabs are detailed in the following
sections:
•
“User-Defined File Preferences” on page 179
•
“Default Directory Preferences” on page 181
•
“Display Default Preferences” on page 181
•
“Plot Default Preferences” on page 183
•
“Grid Line Default Preferences” on page 185
•
“Previous Files List Preferences” on page 185
•
“Miscellaneous Preferences” on page 186
3. In the System Preference dialog tabs, edit the parameters as needed. The
parameters are detailed in the following ENVI Help topics:
•
User-Defined File Preference Settings
•
Default Directory Preference Settings
•
Display Default Preference Settings
•
Plot Default Preference Settings
•
Grid Line Default Preference Settings
•
Previous Files List Preference Settings
•
Miscellaneous Preference Settings
4. Click OK. ENVI prompts you to save the preferences to a file. Either:
•
Click No to use the preference settings for this ENVI session only.
Setting ENVI Preferences
Getting Started with ENVI
Chapter 8: Configuring and Customizing ENVI
•
179
Click Yes to save the preference settings to a file. Saving to a file makes
the preferences available for use in all future ENVI sessions, as well as for
the current session.
5. If you select Yes to save to a file, either:
•
Click OK without entering a new filename to overwrite the current
envi.cfg file.
•
Enter the new configuration filename and click OK.
Note
ENVI uses only a file named envi.cfg for preference settings. If you intend
to use the new configuration file, you must rename the old envi.cfg file
and change your newly saved filename to envi.cfg.
User-Defined File Preferences
Use the User Defined Files tab to specify user-defined files for graphics colors,
graphics color table, ENVI menus, map projections, previous files list, tape device
name, ENVI startup script, math expressions, and user-defined ENVI routines.
Getting Started with ENVI
Setting ENVI Preferences
180
Chapter 8: Configuring and Customizing ENVI
For detailed information on the fields in this dialog, see User-Defined File Preference
Settings in the ENVI User’s Guide.
Figure 8-1: System Preferences Dialog – User Defined Files Tab
Setting ENVI Preferences
Getting Started with ENVI
Chapter 8: Configuring and Customizing ENVI
181
Default Directory Preferences
Use the Default Directories tab to specify the default directories for input and output
files, temporary files, IDL custom routines, spectral library files, and alternative
header file locations for input originating from a CD.
For detailed information on the fields in this dialog, see Default Directory Preference
Settings in the ENVI User’s Guide.
Figure 8-2: System Preferences Dialog – Default Directories Tab
Display Default Preferences
Use the Display Defaults tab to set the display group window sizes, turn on/off
Image and Zoom window scroll bars, set Zoom window interpolation, select which
display group windows to use, choose Scroll/Zoom window graphics colors, display
default stretch, display retain value, set the Scroll/Zoom window positions, and set
the 8-bit color division preferences. You can also change the system graphics colors
and system color tables from this dialog.
Note
If one or more display groups are open when you modify the settings in this tab, the
new settings apply only to subsequent display groups. The open display groups
retain the preference settings that were in effect before you modified them.
Getting Started with ENVI
Setting ENVI Preferences
182
Chapter 8: Configuring and Customizing ENVI
If you prefer to change display preferences for a single display group, see “Setting
Preferences for an Individual Display Group” on page 58.
For detailed information on the fields in this dialog, see Display Default Preference
Settings in the ENVI User’s Guide.
Figure 8-3: System Preferences Dialog – Display Defaults Tab
ENVI Graphics Colors
Use the Edit Graphic Colors dialog to edit the colors ENVI uses for graphics. The
color definitions are stored in the menu\colors.txt file, which ENVI uses unless
you specify a different default graphic colors file (described in “User-Defined File
Preferences” on page 179).
To edit the graphics colors file, see Editing System Graphics Colors in the ENVI
User’s Guide. To add new colors to the graphic colors file, use a text editor to append
Setting ENVI Preferences
Getting Started with ENVI
Chapter 8: Configuring and Customizing ENVI
183
the colors to the end of the file. You can also edit the ENVI color table, which is
described in Editing System Color Tables in the ENVI User’s Guide.
Color system
Color menu button
Sliders
Figure 8-4: Edit Graphic Colors Dialog
Plot Default Preferences
Use the Plot Defaults tab to set the background and foreground colors, fonts,
character size, axis thickness, the number of minor tick marks and length, window
size, and margin sizes to use in ENVI plot windows. See Installing Other TrueType
Fonts with ENVI in the ENVI User’s Guide for additional details about fonts.
Getting Started with ENVI
Setting ENVI Preferences
184
Chapter 8: Configuring and Customizing ENVI
For detailed information on the fields in this dialog, see Plot Default Preference
Settings in the ENVI User’s Guide.
Figure 8-5: System Preferences Dialog – Plot Defaults Tab
Setting ENVI Preferences
Getting Started with ENVI
Chapter 8: Configuring and Customizing ENVI
185
Grid Line Default Preferences
Use the Grid Line Defaults tab to set the colors, fonts, character size, line thickness,
and labels to use in grid line plotting.
Figure 8-6: System Preferences Dialog – Grid Line Defaults Tab
For detailed information on the fields in this dialog, see Grid Line Default Preference
Settings in the ENVI User’s Guide.
Previous Files List Preferences
Select the Previous Files List tab to manage files that appear in the previous files list
when you select File → Open Previous File from the ENVI main menu bar or
Open → Previous File from any Input File dialog. In addition to removing files from
Getting Started with ENVI
Setting ENVI Preferences
186
Chapter 8: Configuring and Customizing ENVI
the list, you can specify files to always keep on the previous files list and to place at
the top of the list when opening a file. This is referred to as making a file sticky.
For detailed information on the fields in this dialog, see Previous Files List
Preference Settings in the ENVI User’s Guide.
Figure 8-7: System Preferences Dialog – Previous Files List Tab
Miscellaneous Preferences
Use the Miscellaneous tab to set the configuration name, the ENVI main menu bar
orientation, maximum number of multilist items, maximum histogram bins, number
of drop-down button items, maximum vertices in memory, PostScript output
parameters, turn on/off IDL command line blocking, the auto apply option for
interactive stretching, and memory usage parameters. You can also set whether to exit
IDL when exiting ENVI, to show a status window for input, to automatically append
Setting ENVI Preferences
Getting Started with ENVI
Chapter 8: Configuring and Customizing ENVI
187
default extensions to filenames, to automatically load default bands, and to open
applicable files to memory.
For detailed information on the fields in this dialog, see Miscellaneous Preference
Settings in the ENVI User’s Guide.
Figure 8-8: System Preferences Dialog – Miscellaneous Tab
Getting Started with ENVI
Setting ENVI Preferences
188
Chapter 8: Configuring and Customizing ENVI
Customizing ENVI
You can set up custom menus, system configuration variables, and even add your
own ENVI routines to the ENVI menu. Several files are used for custom
configurations (located in the menu and map_proj subdirectories):
•
colors.txt: ENVI graphics colors RGB file.
•
display.men: Display group menu bar file (see “Display Group Menu Bar
Definition File” on page 194).
•
display_shortcut.men: Display group right-click menu (see “Display
Group Right-Click Menu Definition File” on page 195).
•
•
e_locate.pro: ENVI directory locator file.
envi.cfg: System configuration file (see “ENVI Configuration File” on
page 194).
•
envi.men: Main menu file (see “Display Group Menu Bar Definition File” on
page 194).
•
filetype.txt: List of ENVI file types and the routine name used to read the
files that need specialized spatial and spectral readers.
•
map_proj.txt: User-defined map projections file (see ENVI Map
Projections File in the ENVI User’s Guide).
•
sensor.txt: List of sensor types that appears in the ENVI header (see
“ENVI Sensor File” on page 130).
•
useradd.txt: Used to define parameters for user-defined plot routines,
Spectral Analyst routines, user-defined map projection routines, user-defined
map projection units, and/or user-defined RPC readers.
•
usersym.txt: Contains user-defined symbols.
Customizing ENVI in a Multiple-User Windows
Environment
Customizing the above files on machines where multiple users work with the same
installation of ENVI may cause problems, as some users may not have access to the
custom files when they start ENVI. One way to avoid problems is to define an
IDL_PATH user variable in the Windows Control Panel.
Customizing ENVI
Getting Started with ENVI
Chapter 8: Configuring and Customizing ENVI
189
To customize ENVI files on a Windows machine without affecting other users who
may run the same installation of ENVI, perform the following steps:
1. Copy the ENVI files you want to customize from the default ENVI installation
directories to your personal directory.
2. Copy the menu\e_locate.pro file into your personal directory. Files in this
directory with a .pro extension cause IDL to add the personal directory to the
search path when it starts up, allowing ENVI to find the copy of your
customized envi.cfg file.
3. In the Windows Control Panel User Variables area, add an IDL_PATH user
variable that places your personal directory before the default installation path.
For instance, for an installation of ENVI in the default
C:\Program Files\ITT\ location, the appropriate Value of the IDL_PATH
Variable for a user called jones would be something like:
C:\users\jones;+C:\Program Files\ITT\IDLxx\products\ENVIxx\lib;+
C:\Program Files\ITT\IDLxx\examples
where xx is the current software version
4. Edit the envi.cfg file in your personal directory to point to the custom files
in your personal directory.
5. Edit the ENVI files in your personal directory. The changes are implemented
when you start ENVI.
6. Create a directory named save_add in your personal directory.
7. Edit your personal envi.cfg to specify the new default save_add directory.
The next time you start ENVI, it looks in the new IDL_PATH for the
envi.cfg file, finds one in the first place it looks (your personal directory),
then reads the ENVI configuration file to determine where to find the rest of
the setup files and your personal save_add folder.
Customizing ENVI in UNIX
Most ENVI users on UNIX systems do not have permissions to change the files listed
under “Customizing ENVI” on page 188, or to add their own procedures to the ENVI
save_add directory. This is because installation of ENVI on UNIX must be
performed by a system administrator logged in as root. Also, multiple users may be
working with the same installation of ENVI, so customizing these files may not be
feasible.
Getting Started with ENVI
Customizing ENVI
190
Chapter 8: Configuring and Customizing ENVI
To customize ENVI files on a UNIX system without affecting other users who may
run the same installation of ENVI, perform the following steps:
Copy the ENVI files you want to customize from the default ENVI installation
directories to your home directory. For a typical UNIX installation, the menu
and map_proj directories are located in
/usr/local/itt/idlxx/products/envixx, where xx is the current
software version. (The installation path may be slightly different on your
machine.)
8. Copy the menu\e_locate.pro file into your home directory. Files in this
directory with a .pro extension cause IDL to add the personal directory to the
search path when it starts up, allowing ENVI to find the copy of your
customized envi.cfg file.
9. Add lines to your .cshrc (or .tcshrc) file in your home directory to execute
the ENVI setup file when you start a new csh (or tcsh) shell and to add your
home directory tree into the IDL file search path. This ensures that ENVI finds
the files in your home directory before it finds copies in the default installation
location where you do not have write permission. Following is an example of
lines to add:
#Set up environment for ENVI x.x and modify IDL search path variable
(IDL_Path).
#(Expecting previously defined IDL search path variable definition)
source /usr/local/itt/idlxx/products/envixx/bin/envi_setup
setenv IDL_PATH ‘+/home/myusername:’$IDL_PATH
where xx is the current software version
You will need to change the home directory path (shown above as
+/home/myusername) to your own home directory path. You may also need
to change the directory path to the envi_setup file if your ENVI installation
is in a location other than /usr/local/itt.
If you anticipate that $IDL_PATH will be undefined (no prior IDL search path
customizations), then be sure to use the string <IDL_DEFAULT> in place of
$IDL_PATH at the end of the second command. Notice in the following
example that <IDL_DEFAULT> is inside the right single-quote character:
#Set up environment for ENVI x.x and modify IDL search path variable
(IDL_Path).
#(Expecting previously defined IDL search path variable definition)
source /usr/local/itt/idlxx/products/envixx/bin/envi_setup
unsetenv IDL_PATH
setenv IDL_PATH ‘+/home/myusername:<IDL_DEFAULT>’
where xx is the current software version
Customizing ENVI
Getting Started with ENVI
Chapter 8: Configuring and Customizing ENVI
191
Bash Shell
Your ENVI installation also contains a setup file for the Bash shell. Place the
following equivalent commands in the .bashrc file in your home directory:
Using a previously defined IDL search path definition:
#Set up environment for ENVI x.x and modify IDL search path
variable (IDL_Path).
#(Expecting previously defined IDL search path variable
definition)
./usr/local/itt/idlxx/products/envixx/bin/
envi_setup.bash
IDL_PATH=‘+/home/myusername:’$IDL_PATH
export IDL_PATH
where xx is the current software version
Not using a previously defined custom IDL search path definition:
#Set up environment for ENVI x.x and modify IDL search path
variable (IDL_Path).
#(Expecting previously defined IDL search path variable
definition)
./usr/local/itt/idlxx/products/envixx/bin/envi_setup.bash
unset IDL_PATH
IDL_PATH=’+/home/myusername:<IDL_DEFAULT>’
export IDL_PATH
where xx is the current software version
10. Edit the envi.cfg file in your home directory to point to its customized files.
11. Edit the ENVI files in your personal directory. The changes will be
implemented when you start ENVI.
12. Create a directory named save_add in your personal directory.
13. Edit your personal envi.cfg to specify the new default save_add directory.
The next time you start ENVI, it looks in the new IDL_PATH for the
envi.cfg file, finds one in the first place it looks (your personal directory),
then reads the ENVI configuration file to determine where to find the rest of
the setup files and your personal save_add folder.
Platform-Specific Customization
Some modifications may be necessary for specific platforms, including:
•
Windows SCSI tape support
•
UNIX fonts
Getting Started with ENVI
Customizing ENVI
192
Chapter 8: Configuring and Customizing ENVI
•
UNIX window auto-placement
•
UNIX color flashing on 24-bit displays
•
UNIX pseudocolor on 24-bit displays
SCSI Tape Support for Windows
ENVI includes tape support for PCs running Microsoft Windows 2000 and
Windows XP. To install the tape drivers for Windows, open the aspi_v470.exe
self-extracting archive in the \tape32 directory on the ENVI for Windows
installation CD. See the included README.DOC file for installation instructions.
When installed, this routine provides transparent access to ENVI tape tools using the
ASPI32 interface provided with Windows. All ENVI tape functions work the same as
their UNIX counterparts on any SCSI tape device that runs under ASPI32. Tape32
for ENVI supports reading of many known tape formats including Landsat MSS,
Landsat TM, AVHRR, AVIRIS, SPOT, etc. See the ENVI Tape Utilities menu
option for a complete list. Use ENVI’s Scan Tape and Dump Tape functions to read
other formats that ENVI does not directly support.
From the ENVI main menu bar, select File → Tape Utilities → tape_function.
Window Auto-Placement on UNIX
On some UNIX platforms, new windows may require your input for screen
placement. It is recommended that you disable this function.
For example, on SGI systems using 4Dwm, the following two lines placed in the
.Xdefaults file will allow auto-placement of windows. See your system
documentation for other options.
4Dwm*InteractivePlacementfalse
4Dwm*ClientAutoPlacefalse
Setting the Font on UNIX Platforms
You can select any font available to the X server for your IDL and ENVI session. The
X windows command xlsfonts lists all the available fonts. The recommended font
for ENVI is either a 12 or 14-point courier (fixed width), or a 12- or 14-point
Times-Bold (proportional). For more information, see the Using IDL manual.
Customizing ENVI
Getting Started with ENVI
Chapter 8: Configuring and Customizing ENVI
193
To enable a particular font for your IDL session, include the following line in your
.Xdefaults file with your selected font replacing the example.
Idl*fontList-adobe-times-bold-r-normal--12-120-75-75-p-67-iso88591
Color Flashing on 24-Bit UNIX Machines
ENVI display groups sometimes flash on 24-bit displays when other programs or the
windowing system requires some of the colors.
You may be able to stop this flashing by entering the following into your
.Xdefaults file.
Idl.gr_visualTrueColor
Idl.gr_depth24
Pseudocolor on 24-Bit UNIX Machines
ENVI automatically configures for both 8-bit and 24-bit displays. For more
information see the Using IDL manual.
To run ENVI in an 8-bit mode on a 24-bit display, enter the following line in your
.Xdefaults file to force your system to operate in 8-bit mode whenever IDL is
started.
Idl.gr_visualPseudoColor
Idl.gr_depth8
Customizing Configuration and Definition Files
You can customize ENVI to:
•
Optimize hardware configurations.
•
Configure the ENVI main menu bar and Display group menu bar.
•
Configure the right-click menu.
Getting Started with ENVI
Customizing ENVI
194
Chapter 8: Configuring and Customizing ENVI
ENVI Configuration File
Use the ENVI configuration file (envi.cfg) to customize ENVI and to optimize
specific hardware configurations to suit your preferences. The file is an ASCII text
file containing keywords and associated values. You can change the way ENVI uses
memory, handles color, and other setup parameters by specifying new values.
The ENVI configuration file must have the keywords ENVI CONFIGURATION FILE
at the top of the file. Keywords determine the ENVI startup configuration. See ENVI
Preference Settings in the ENVI User’s Guide for keyword descriptions.
Edit the file using a text editor or word processor, or change the file from within
ENVI by selecting File → Preferences from the ENVI main menu bar (see “Setting
ENVI Preferences” on page 178).
Note
The envi.cfg file must be in a directory that is in the IDL search path.
ENVI Main Menu Bar Definition File
The ENVI main menu bar definition file is named envi.men. The entire main menu
bar is user-configurable. You can reposition existing items and add new items to suit
your needs. ENVI does not distinguish between ENVI and user functions, which
enables easy integration of user functions. One of ENVI’s most powerful features is
this potential for customization. The specifics of how to configure the menu are
included in the menu file text.
To use your created main menu file as the default menu, enter the complete filename
in the envi.cfg file or enter it using File → Preferences (see “User-Defined File
Preferences” on page 179).
Display Group Menu Bar Definition File
The Display group menu bar definition file is named display.men. The entire menu
is user-configurable. You can reposition existing items and add new items to suit your
needs. Instructions for customizing the menu are included in the menu file text.
To use your own Display group menu bar file as the default menu, enter the complete
filename in the envi.cfg file or enter it using File → Preferences (see “UserDefined File Preferences” on page 179).
Note
If your changes to envi.men or display.men do not take effect, see When the
New Menu Button Does Not Appear in the ENVI Programmer’s Guide.
Customizing ENVI
Getting Started with ENVI
Chapter 8: Configuring and Customizing ENVI
195
Display Group Right-Click Menu Definition File
The display group right-click menu definition file is named
display_shortcut.men. The entire menu is user-configurable. You can reposition
existing items and add new items to suit your needs. Instructions for customizing the
menu are included in the menu file text.
To use your own Display group menu bar file as the default menu, enter the complete
filename in the envi.cfg file or enter it using File → Preferences (see “UserDefined File Preferences” on page 179).
Getting Started with ENVI
Customizing ENVI
196
Chapter 8: Configuring and Customizing ENVI
Using IDL with ENVI
If you have an ENVI + IDL installation, you can configure how IDL multi-threading
is handled (see Modifying IDL CPU Parameters in the ENVI User’s Guide).
In addition to setting IDL multi-threading parameters, this section describes how to:
•
Import and export IDL variables
•
Compile IDL code
Importing IDL Variables
Use Import IDL Variables to import IDL variables into ENVI. The variables must
be defined on the ENVI command line. The Import IDL Variables function is not
available in the ENVI-only license.
To import IDL variables:
1. From the ENVI main menu bar, select File → Import IDL Variables. The
Import IDL Variables dialog appears with a list of all defined variables.
2. Select the desired variable names to import by clicking in the check box next to
the name.
•
To add a range of variable names, enter the starting and ending variable
numbers and click Add Range.
•
To select all the variable names, click Select All.
•
To clear the selected variable names, click Clear.
3. To save a copy of the data in IDL, use the arrow toggle button to select Yes.
Note
If you select No, the data is imported into ENVI and deleted from IDL.
4. Click OK to import the selected variables.
All one-dimensional variables are placed in a plot window; the 2D and 3D
variables appear in the Available Band List as memory items.
Using IDL with ENVI
Getting Started with ENVI
Chapter 8: Configuring and Customizing ENVI
197
Exporting to IDL Variables
Use Export to an IDL Variable to export and/or subset an ENVI band or file to an
IDL variable on the ENVI command line.
Tip
If the ENVI command line is not visible in the IDL window, select Window →
Command Input from the IDL main menu bar. Export to an IDL Variable is not
available in the ENVI-only license.
To export IDL variables:
1. From the ENVI main menu bar, select File → Export to an IDL Variable. The
Export to IDL Input File/Band dialog displays.
2. Select an input file or band and perform optional spatial subsetting and spectral
subsetting. For subsetting details, see Subsetting Data in the ENVI User’s
Guide.
3. In the Export Variable Name dialog, select one of the following options:
•
If the variable was previously defined, select on the name in the Select
variable to receive export list.
•
If the variable is a new one, enter the name of an undefined IDL variable in
the New Variable Name field.
4. Click OK. The exported data is available to use at the ENVI command line.
Compiling IDL Code
Use Compile IDL Module if you have written your own IDL code to use in ENVI.
Each time you modify your IDL code, you must compile it. Optionally, you can have
the code automatically re-compiled each time ENVI starts by saving it in the
save_add directory. See Default Directory Preference Settings and Compiling in the
ENVI User’s Guide for additional information.
To compile IDL code:
1. From the ENVI main menu bar, select File → Compile IDL Module. The
Enter Module Filename dialog appears.
2. Select the module filename.
3. Click OK. Any compile errors are shown in the main IDL window.
Getting Started with ENVI
Using IDL with ENVI
198
Using IDL with ENVI
Chapter 8: Configuring and Customizing ENVI
Getting Started with ENVI
Appendix 9ma
Glossary
This glossary supplements ENVI Help by listing some terms that are frequently
referenced in ENVI documentation or that are unique to ENVI functionality. It is not
an exhaustive list of remote sensing terms. For terms that describe an ENVI function,
see ENVI Help for complete details.
AATSR Advanced Along-Track Scanning Radiometer; an ENVISAT sensor.
absorption feature A region of the electromagnetic spectrum where a given
material absorbs radiation, shown by a low point in a spectral curve. Each material
has unique absorption features, which serve as identifying characteristics.
abundance image In hyperspectral analysis, an image whose values represent the
fractions of total spectrally integrated radiance or reflectance of a pixel contributed by
each spectrally unique material.
ACRES Australian Centre for Remote Sensing.
across track The imaging direction perpendicular to the along track direction of a
satellite or aircraft. The across track viewing angle determines the swath.
Getting Started with ENVI
199
200
Appendix 9: Glossary
adaptive filter A type of spatial filter that uses the standard deviation of those pixels
within a local box (kernel) surrounding each pixel to calculate a new pixel value.
Typically, the original pixel value is replaced with a new value. Unlike a typical lowpass smoothing filter, adaptive filters preserve image sharpness and detail while
suppressing noise.
adjacency effect The change in a pixel value caused by photons that reflect off the
ground and scatter into the sensor field-of-view; radiance from neighboring pixels
affects the measured radiance of a target pixel. The algorithms in the Atmospheric
Correction Module in ENVI account for this effect.
ADRG ARC Digitized Raster Graphics; a National Geospatial-Intelligence Agency
(NGA) data format.
aerosol scattering Redirection of electromagnetic energy caused by aerosols,
which are particles suspended in the atmosphere.
AIRSAR Airborne Synthetic Aperture Radar; a NASA Jet Propulsion Laboratory
(JPL) sensor.
along track The imaging direction parallel to the direction that a satellite or aircraft
moves.
alpha residuals In hyperspectral analysis, alpha residuals are spectra that are a
function of emissivity only. They have a similar shape as emissivity spectra but have a
zero mean.
annotation A graphic element added to an image or map composition. Annotation
objects include, but are not limited to, symbols, shapes, polylines, text, arrows, scale
bars, borders, map keys, declination diagrams, color ramps, images, and plots.
apparent reflectance Reflectance recorded at the sensor; also defined as radiance
normalized by solar irradiance. Apparent reflectance is not true reflectance because
shadows and directional effects have not been accounted for.
arbitrary profile Also called a transect; a line drawn on an image, whose underlying
data values are graphed in a cross-section plot.
area-based matching A method of automatic image-to-image registration that
compares the gray scale values of patches of two or more images and tries to find
conjugate image locations based on the similarity of the gray scale value patterns.
ASAR Advanced Synthetic Aperture Radar; an ENVISAT sensor.
ASCII American Standard Code for Information Interchange; a simple text format.
aspect The direction (azimuth) that a surface faces, typically in degrees clockwise
from North (0 degrees); a parameter used in topographic modeling.
Getting Started with ENVI
Appendix 9: Glossary
201
ASTER Advanced Spaceborne Thermal Emission and Reflection Radiometer; a
NASA EOS sensor.
atmospheric correction A method used to correct sensor radiance for atmospheric
effects by mathematically modeling the physical behavior of radiation as it passes
through the atmosphere. Following are some atmospheric correction methods
available in ENVI:
•
Dark Subtraction: A method that uses the darkest pixel in a remote sensing
image to remove path radiance and scattering effects. The method assumes that
each band in an image contains some pixels at or close to a zero brightness
value, and that atmospheric effects and path radiance add a constant value to
each pixel in a band. Subtracting this constant value from the particular spectra
removes the first-order scattering component. Dark subtraction, however, does
not account for water vapor and ozone absorption.
•
Empirical Line: A method that forces image spectra to match reference
spectra (field or laboratory) through linear regression.
•
FLAASH: Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes;
an atmospheric correction modeling tool in ENVI for retrieving spectral
reflectance from hyperspectral radiance images. FLAASH incorporates the
MODTRAN4 radiation transfer model to compensate for atmospheric effects.
•
Flat Field: A method that calculates the mean spectra for a region assumed to
have no spectral variation. The method divides each pixel spectrum by the Flat
Field spectrum.
•
IAR: Internal Average Reflectance; a method that calculates the mean
spectrum for the entire scene. The method divides each pixel spectrum by the
scene-average spectrum.
•
QUAC: Quick Atmospheric Correction; an automated atmospheric correction
method in ENVI for retrieving spectral reflectance from multispectral and
hyperspectral images.
atmospheric window A region of the electromagnetic spectrum in which satellites
and aircraft cannot acquire measurements because of substances that absorb solar
radiation (the most common are water vapor and CO2).
ATSR Along Track Scanning Radiometer; an ERS-1 and ERS-2 sensor.
attributes Data that describe the properties of a point, line, or polygon record in a
GIS. Attributes are typically stored in table format.
autocorrelation In multivariate statistics, a measure of correlation among residuals
from a regression equation. An autocorrelation (r) value of 1.0 or -1.0 indicates a
Getting Started with ENVI
202
Appendix 9: Glossary
strong relationship between successive residuals, and a value of 0 indicates no
relationship. In remote sensing, autocorrelation provides an indication of the local
homogeneity of a data set, by evaluating the overall pattern between proximity and
similarity of pixel values.
AVHRR Advanced Very High Resolution Radiometer (NOAA).
AVIRIS Airborne Visible/Infrared Imaging Spectrometer (NASA/JPL).
band A discrete portion of the electromagnetic spectrum measured by an aircraft or
satellite sensor. Legacy multispectral sensors typically have fewer, wider bands,
while modern hyperspectral sensors have hundreds of bands that each measure a very
narrow range of wavelengths.
BandMax An algorithm developed by the Galileo Group, Inc., used to increase
classification accuracy of targets in hyperspectral analysis. BandMax determines an
optimal set of bands to help separate targets from known background materials.
Band Math An ENVI tool that allows you to define and apply mathematical
expressions to spatial image data, resulting in a new output image.
band ratio The process of dividing one spectral band by another to enhance their
spectral differences and to reduce the effects of topography.
batch mode Performing a linear sequence of ENVI processing tasks in a non-
interactive manner.
batch mode routine An IDL program that includes ENVI library routines to
perform a non-interactive image processing task.
BIL Band-interleaved-by-line; an interleave format that stores the first line of the first
band, followed by the first line of the second band, followed by the first line of the
third band, interleaved up to the number of bands.
BIP Band-interleaved-by-pixel; an interleave format that stores the first pixel for all
bands in sequential order, followed by the second pixel for all bands, followed by the
third pixel for all bands, and so forth, interleaved up to the number of pixels.
BSQ Band-sequential; an interleave format where each line of the data is followed
immediately by the next line in the same spectral band. This format is optimal for
spatial (x,y) access of any part of a single spectral band.
buffer A user-specified extension zone around a point, line, or polygon. In a buffer
zone image, each pixel represents the distance from that pixel to the nearest pixel of
the selected class(es). Pixels that fall beyond a user-specified maximum distance
threshold are set to that maximum distance.
Getting Started with ENVI
Appendix 9: Glossary
203
byte order The order of bytes in integer, long integer, 64-bit integer, unsigned 64-bit
integer, floating-point, double-precision, and complex data types. Following are the
two methods of byte order:
•
Host (Intel): Least significant byte first (LSF); byte order=0 in the ENVI
Header; used in Intel-based (Windows, Linux, MacIntel) platforms.
•
Network (IEEE): Most significant byte first (MSF); byte order=1 in the ENVI
Header; used in Macintosh and Unix platforms.
CADRG Compressed ARC Digitized Raster Graphics; an NGA data format.
change detection The process of comparing two or more images acquired at
different times.
CCRS Canadian Centre for Remote Sensing.
CIB Controlled Image Base; an NGA data format.
classification The process of assigning pixels of a multispectral image to discrete
categories. Following are some popular classification methods available in ENVI:
•
•
Supervised: A general technique that uses information derived from a few
areas of known identity to classify unknown pixels in the remaining image.
•
Binary Encoding: A technique that encodes data and endmember spectra
into zeros and ones, based on whether a band falls below or above the
spectrum mean, respectively.
•
Maximum Likelihood: Pixels are assigned to the class in which they have
the highest probability of being a member.
•
Minimum Distance: A technique that uses the mean vector of each
endmember and calculates the Euclidean distance from each unknown
pixel to the mean vector for each class.
•
Spectral Angle Mapper: An algorithm that determines the spectral
similarity between two spectra by calculating the angle between them and
treating them as vectors in a space with dimensionality equal to the
number of bands.
Unsupervised: An automated technique that searches for natural groups, or
clusters, of pixels based on their brightness in several bands. Unlike the
supervised method, unsupervised classification does not begin with a
predefined set of classes.
•
K-Means: A technique that calculates initial class means evenly
distributed in the data space, then iteratively clusters the pixels into the
nearest class using a minimum distance technique.
Getting Started with ENVI
204
Appendix 9: Glossary
•
Isodata: A technique that calculates class means evenly distributed in the
data space, then iteratively clusters the remaining pixels using minimum
distance techniques.
clustering The statistical analysis of a set of pixels to detect their inherent tendency
to form clusters in n-dimensional (n-D) measurement space.
color-infrared composite Also called CIR, or false-color composite; An image
where the near-infrared band (0.76 - 0.9 μm) is displayed in red, the red band (0.6 0.7 μm) is displayed in green, and the green band (0.5 - 0.6 μm) is displayed in blue.
color ramp An annotation object that shows a gradual transition from one color to
another. For a gray scale image, the transition is from the minimum to the maximum
gray scale value. For a color image, the color ramp is the distribution of the selected
color palette.
color table A special lookup table that associates screen brightness values with
specific RGB values. For a color image, the output colors consist of different red,
green, and blue values. For a gray scale image, the red, green, and blue data values
are the same for a given data value.
color transform A method used to convert RGB images to a different color space,
and vice-versa; by applying a contrast stretch in another color space, you can
highlight certain features in an image. Also see data fusion and image sharpening.
compound widget In ENVI programming, a predefined widget that ENVI
automatically builds for you when you call the appropriate library routine in your
user function (see the ENVI Reference Guide for a list of library routines). Each
compound widget performs a specific task that is often needed in a custom graphical
user interface for image processing.
confusion matrix Also called a contingency matrix. A table used to assess
classification accuracy and misclassification between categories. The matrix is size m
x m, where m is the number of classes. The rows in the matrix represent classes that
are assumed to be true, while the columns represent classes derived from remote
sensing imagery. The matrix also lists errors of commission and omission.
contour line A line that follows the same elevation on a topographic map.
contrast stretch A method of improving the contrast of a remote sensing image by
stretching the original range of digital numbers (DNs) across the full contrast range
of the display. Following are the most commonly used stretches in ENVI:
•
Equalization: Also called a histogram equalization stretch; you select the
number of output gray scale classes (bins) to redistribute the data into, based
on an image's histogram. The program assigns near-equal numbers of pixels
into each bin. This type of stretch greatly enhances the most populated range of
Getting Started with ENVI
Appendix 9: Glossary
205
brightness values in the image and automatically reduces the contrast in the
very light or very dark parts of an image.
•
Gaussian: A type of stretch based on a Gaussian curve, centered on a mean
DN value that you specify. The range of data values that fall within a given
standard deviation (that you specify) of the mean are stretched from 0 to 255.
•
Linear: A type of stretch that sets a minimum and maximum input value to 0
and 255, respectively. All values in between are linearly aligned to
intermediate output values.
•
Square root: A linear stretch applied to the square root of a histogram.
convolution The process of applying a spatial filter on an image, where each pixel is
based on a weighted average of coefficients within an n x n matrix surrounding the
pixel (where n is an odd number).
correlation A statistical measure of the linear relationship between two data sets. If
they vary in the same direction, the correlation is positive; if they vary in the opposite
direction, the correlation is negative.
correlogram A plot of autocorrelation values at multiple lag distances; a measure of
how autocorrelation decreases as distance increases. For example, if you specify a
maximum lag distance of 5 pixels, autocorrelation is calculated for lags of 5, 4, 3, 2,
and for each pixel's nearest neighbors.
covariance A statistical measure of the tendency of two variables to move or vary
together; more specifically, the simultaneous deviations of two variables from their
means.
data dimensionality The number of variables (bands) present in a data set.
data fusion The process of displaying two data sets of the same area together in one
RGB color composite. The data sets must be registered and resampled so that they
have the same orientation, pixel size, and image dimensions. A popular example of
data fusion is to apply an HSV color transform to one image, replace the value band
with another image, then reverse the color transform. This produces an image that
merges the color characteristics of one image with the spatial characteristics of
another image.
datum A reference point or surface against which position measurements are made,
and an associated model of the shape of the earth for computing positions. Different
nations and agencies use different datums based on local reference points. Examples
include the NAD83 and NAD27.
decision tree A classification technique that uses a series of binary decisions to
place pixels into classes. Each decision point divides pixels into two classes based on
Getting Started with ENVI
206
Appendix 9: Glossary
an expression. Then you can divide each new class into two more classes based on
another expression, and so on.
declination diagram An annotation object that includes any combination of arrows
pointing to true north, grid north, and magnetic north.
delaunay triangulation An image-to-image warping method that fits triangles to
irregularly spaced tie points and interpolates values to the output grid.
DEM Digital elevation model; a raster data set where each pixel represents an
elevation value.
density slice To convert the continuous gray tone of an image into a series of
density intervals, or slices, each corresponding to a specific digital range.
deskew A preprocessing method used to correct systematic distortions caused by
earth rotation and scan skew; these were especially evident in Landsat MSS imagery.
destripe A preprocessing method used to remove periodic scan line striping in
image data. This type of striping is often seen in Landsat MSS data (every 6th line)
and, less commonly, in Landsat TM data (every 16th line).
DIMAP Digital Image Map; a SPOT data format.
display group A term that refers collectively to the Scroll window, Image window,
and Zoom window in ENVI. See “Display Groups” on page 46 for an example.
display group menu bar The menu bar in one window of a display group. See
“Display Groups” on page 46 for an example.
DLG Digital Line Graph; a USGS vector data format.
DMSP Defense Meteorological Satellite Program (U.S. Air Force).
DN Digital number; also called pixel value.
DOQ Digital Orthophoto Quadrangle; a USGS data format.
DRG Digital Raster Graphics; a scanned topographic map generated by the USGS.
DTED Digital Terrain Elevation Data; an NGA data format.
DXF Data Exchange Format; a format for storing vector data in ASCII or binary
files.
dynamic overlay An ENVI feature that allows you to immediately overlay and
toggle (flicker) between two linked images.
ECW Enhanced Compressed Wavelet; a proprietary data format developed by Earth
Resource Mapping that is primarily intended for aerial imagery.
Getting Started with ENVI
Appendix 9: Glossary
207
eigenvalues Transformation coefficients in principle components analysis that can
be used to determine the percent of total variance explained by each of the principle
components.
eigenvectors A set of weights applied to band values to obtain principal
components; they show the relative contributions of the different original bands to the
final principal components bands.
electromagnetic spectrum The full spectrum of electromagnetic radiation,
extending from short cosmic waves to long radio waves.
ellipsoid A smooth mathematical surface that is used to represent the geometric
model of the earth. Its axes approximate the dimensions of the earth, rotated around
the polar axis. Examples include the Clark ellipsoid of 1866 and the GRS80 ellipsoid.
emissivity The ratio of the radiance emitted from an object at a particular
wavelength to the radiance that a blackbody would emit at the same temperature and
wavelength. An emissivity of 1.0 is a perfect blackbody (a perfect “absorber”). Most
earth surface types have emissivities between 0.9 and 1.0.
endmember A pure spectrally unique material that occurs in a scene.
EFFORT Empirical Flat Field Optimal Reflectance Transformation; an algorithm
that “polishes” out noise and errors that may appear in hyperspectral apparent
reflectance data, thus improving the accuracy of the data and making apparent
reflectance spectra appear more like spectra of real materials.
ENVI header file A text file that must accompany an image file and reside in the
same directory as the image file. The header file lists required image characteristics
such as number of samples, number of lines, number of bands, offset, file type, byte
order, data type, and storage order.
ENVI main menu bar The main menu that appears when you start ENVI.
ENVI save files Binary files that contain the basic ENVI library routines and
internal variables required to run ENVI.
ENVISAT Environmental Satellite (European Space Agency)
EOS Earth Observing System (NASA)
EOSAT Earth Observation Satellite Company
epipolar images A stereo pair of images in which the left and right image are
oriented such that ground control points (GCPs) have the same y-coordinates on both
images, thus removing one dimension of variability. Epipolar images are generated
based on epipolar geometry and are used to extract a DEM.
EROS Earth Resources Observation System.
Getting Started with ENVI
208
Appendix 9: Glossary
ERS European Remote Sensing satellite (European Space Agency).
ESA European Space Agency.
ESRI® Environmental Systems Research Institute.
ETM+ Enhanced Thematic Mapper; a Landsat-7 sensor.
exterior orientation In photogrammetry, the process of transforming image
coordinates to object (ground) coordinates using ground control points (GCPs).
event handler IDL code that manages events generated by widgets.
EVF ENVI vector file; a format that ENVI uses to store vector data, no matter what
the input native format is. EVF is the most efficient format for storing and
manipulating vector information within ENVI.
feathering The process of blending the edges of overlapping areas in input images
for pixel-based and map-based mosaicking.
feature Also called spatial feature; A user-defined geographic phenomenon that can
be modeled or represented using geographic data sets. Examples include roads,
buildings, grasslands, and water bodies.
feature-based matching A method of automatic image-to-image registration that
extracts distinct features from images and identifies features that correspond to one
another (by comparing feature attributes and location).
FFT Fast Fourier Transform; a filter used to transform image data into a complex
output image showing its various spatial frequency components.
fiducial marks A series of four or eight crosshairs placed along the edge of aerial
camera film during exposure. The intersection of imaginary lines connecting opposite
fiducial marks corresponds to the principal point of the photograph. Fiducial marks
are used primarily to orthorectify aerial photographs.
field spectra Spectra of natural features such as minerals or vegetation, analyzed in
the field using a handheld spectrometer. Field spectra are often used as a baseline, or
“true” spectra for identification of minerals or vegetation types from hyperspectral
remote sensing imagery.
flat binary A general raster format where data are stored as a binary stream of bytes
in BSQ, BIP, or BIL format.
FLAASH Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes; a first-
principles atmospheric correction modeling tool for retrieving spectral reflectance
from hyperspectral radiance images. FLAASH is a separate add-on module in ENVI.
fly-through A 3D animation along a hypothetical flight path in a 3D SurfaceView.
Getting Started with ENVI
Appendix 9: Glossary
209
frame central projection A modeling scenario used to compute rational polynomial
coefficients (RPCs) in frame camera and digital (frame central) aerial photography.
This projection has one perspective center, which is collinear in space with its object
point and image point.
function In ENVI programming, a program unit containing one or more IDL
statements that returns a value. Functions take the following form:
Result = FUNCTION_NAME(Argument [, Optional Argument])
FWHM Full width half maximum; an engineering term that pertains to the signal
curve of a sensor; in a plot of the measured signal (which approaches a near-Gaussian
distribution), the FWHM is the horizontal distance between the two points on the
signal curve that are half the maximum value. FWHM is an important measure of the
quality of an imaging device and its spectral resolution.
Gain In ENVI, a value that is multiplied by the pixel value to scale it into physically
meaningful units of radiance:
radiance = DN * gain + offset
GCP Ground control point; a point on the ground whose location is known through a
horizontal coordinate system or vertical datum. A GCP relates a point in a remote
sensing image (x,y) to a geographic point on the earth (latitude/longitude, for
example).
GCTP General Cartographic Transformation Package.
geographic coordinate system A coordinate system for defining locations on the
earth’s surface using a 3D spherical model that includes an angular unit of measure, a
prime meridian, and a datum.
geoid An undulating surface that approximates the shape of the earth and mean sea
level throughout the world. The direction of gravity is perpendicular to the geoid at
every point. The geoid is the reference surface for surveying and some inertial
navigation systems. An example is the OSU91A geoid.
geometrically corrected An image that has been adjusted to remove geometric
distortions caused by lens distortion, sampling rate variation, sensor drift,
topographic relief, and other factors.
georeference To map a remote sensing image to a known location on the earth, by
referencing it to a map projection.
GeoTIFF A public-domain metadata standard that allows geographic information to
be embedded within a TIFF file. Remote sensing software uses the metadata to
position the geographic data.
GIS Geographic information systems.
Getting Started with ENVI
210
Appendix 9: Glossary
GLT Geographic lookup table; a binary file that maps an input pixel to an output
pixel based on input geometry information. A GLT file contains integer pixel location
values that are sign-coded to indicate if a certain output pixel is “real” or interpolated
from nearest-neighbor resampling. The two bands of a GLT file refer to the original
sample number and original line number, respectively. You can georeference your
data directly from a GLT file.
GPS Global positioning system.
gray scale A range of black to white tones as displayed on a monitor or in an image;
a gray scale image is created when the red, blue, and green color guns of the monitor
are assigned the same value for each pixel.
HDF Hierarchical Data Format; a data structure developed by the National Center for
Supercomputing Applications.
HDF-EOS Hierarchical Data Format - Earth Observing System; a format used for
storing data from NASA EOS sensors that adds geolocation objects (grid, point, and
swath) to the HDF format.
hill shade image A color shaded-relief image created by transforming a color image
into HSV color space, replacing the value band with a shaded-relief image, and
transforming the color image back to RGB space.
histogram A plot that shows the frequency of occurrence (along the vertical axis) of
individual measurements or data values (along the horizontal axis); a frequency
distribution.
HLS Hue-lightness-saturation color space.
HSV Hue-saturation-value color space.
hyperspectral A term used to describe data sets typically composed of 100 to 200
(or more) spectral bands of relatively narrow, contiguous, bands (5 to 10 nm).
Hyperspectral imaging creates a large number of images from contiguous regions of
the electromagnetic spectrum. This increases sampling of the spectrum (versus
multispectral data) and greatly increases the amount of information available to a
researcher. Also see imaging spectrometer.
IDL Interactive Data Language.
IGM Input Geometry file; an ancillary file that provides map information in two
bands: one for x coordinates and another for y coordinates. Many data sets include
IGM files in their distribution. An IGM file itself is not georeferenced, but it contains
georeferencing information for each original, raw pixel in an image.
IKONOS A GeoEye high-resolution satellite that produces 1 m panchromatic and 4
m multispectral imagery.
Getting Started with ENVI
Appendix 9: Glossary
211
image box The red box inside a Scroll window that defines the area covered in the
Image window. See “Display Groups” on page 46 for an example.
image coordinates Also called pixel coordinates; the location of an image pixel in
generic (sample, line) coordinates. Image coordinates always increase (one unit for
every pixel) with increasing sample and line number. Also see XSTART and
YSTART.
image cube A color image created from a multispectral or hyperspectral file where
the data set is shown with an image represented on the face of a cube and the spectral
information of the edge pixels depicted on the other faces.
image sharpening The process of merging a low-resolution color image with a
high-resolution gray scale image (with resampling to the high-resolution pixel size).
Image window The window in a display group that displays the image at full
resolution. If the image is large, the Image window displays the subsection of the
image defined by the Scroll window Image box. See “Display Groups” on page 46
for an example.
imaging spectrometer A sensor designed to collect hyperspectral imagery.
Examples include AVIRIS and HyMap. Many spectral images are acquired
simultaneously, where each pixel in an image contains a continuous spectrum with
typically hundreds of spectral measurements that is used to analyze surface features
and atmospheric constituents.
incidence angle In a radar system, the angle defined by the incident radar beam and
the vertical (normal) to the intercepting surface. In pushbroom sensors, the along
track incidence angle is the angle between the vertical position of the satellite and its
forward or backward viewing direction. The across track incidence angle is the angle
(in degrees) between the vertical position of the satellite and its side-viewing
direction when the sensor is scanning along the side.
interactive user routine In ENVI programming, a user function that performs some
type of interactive analysis and is triggered by certain events or user selection.
Examples include plot functions, Spectral Analyst functions, user-defined map
projection types, user-defined units, user-defined RPC readers, and user move
routines.
interior orientation In photogrammetry, the process of transforming scanned image
pixel coordinates to image coordinates defined by fiducial marks in the aerial
photograph.
interleave A term that refers to how raster image data are stored. See BSQ, BIL, and
BIP.
IRS Indian Remote Sensing satellite (Government of India, Department of Space).
Getting Started with ENVI
212
Appendix 9: Glossary
JERS Japanese Earth Resources Satellite (Japan Aerospace Exploration Agency).
JITC Joint Interoperability Test Command; an organization that certifies systems
implementing the NITF data format for compliance with NITF standards.
JPEG Joint Photographic Experts Group image format.
JPL Jet Propulsion Laboratory (NASA).
kernel An array of pixels used for digital image filtering or to constrain an operation
to a subset of pixels.
laboratory spectra Spectra of materials (such as minerals or vegetation types)
measured with a spectrometer in a controlled laboratory environment. Laboratory
spectra are often used as a baseline, or “true” spectra for identification of materials
from hyperspectral remote sensing imagery.
Lambertian A surface that emits or reflects radiation isotropically, according to
Lambert’s law; a perfectly diffusing surface; the brightness (luminance, radiance) of a
lambertian surface is constant regardless of the angle from which it is viewed.
LAS A binary data format that contains LIDAR point data records.
layer stacking The process of building a multi-band file from georeferenced images
of various pixel sizes, extents, and projections. The output file has a geographic
extent that either encompasses all of the input file extents or encompasses only the
data extent where all of the files overlap.
library routines IDL programs that encompass nearly all of the functionality in
ENVI. The ENVI Reference Guide contains a complete index and full reference page
for each library routine.
LIDAR Light detection and ranging; a technology that determines distance to an
object or surface by measuring the time delay between a laser pulse transmission and
detection of the return signal.
line central projection A model used to compute rational polynomial coefficients
(RPCs) in imagery from pushbroom sensors and line central aerial photography. Each
scan line has its own projection center.
line of sight A spatial analysis tool that determines which pixels can be seen from a
specific pixel within any file that has an associated DEM; topographic features will
obscure some pixels from view.
line The y component of a raster image coordinate pair (x,y); same as row.
logarithmic residual An input spectrum divided by the spectral geometric mean
(the mean of all bands for each pixel) of a data set, which is then divided by the
spatial geometric mean (the mean of all pixels for each band). Logarithmic residuals
Getting Started with ENVI
Appendix 9: Glossary
213
are used to remove solar irradiance, atmospheric transmittance, instrument gain,
topographic effects, and albedo effects from radiance data.
LUT Lookup table; a static table that associates an image pixel value with a specific
screen brightness value; used for contrast-stretching an image.
majority analysis A post-classification tool used to change spurious pixels within a
large single class to that class. You specify a kernel size, and the center pixel in the
kernel is replaced with the class value represented by the majority of the pixels in the
kernel.
map projection A mathematical method of representing the earth on a flat plane.
Hundreds of map projections are available to satisfy various project requirements
(accurate distance, accurate navigation, equal area, etc.)
MAS MODIS Airborne Simulator (NASA).
mask An image consisting of zeros and ones that, when applied to another image,
tells ENVI which pixels in that image to analyze (ones) and which pixels to ignore
(zeros). A mask is useful, for example, if you want to calculate image statistics while
ignoring missing data values.
MERIS Medium Resolution Imaging Spectroradiometer; an ENVISAT sensor.
meta file A virtual file in ENVI that is essentially a combination of image files or
bands treated as the same input file. An ENVI meta file is a text file with names and
locations of files on disk. When you select the meta file for input or processing, ENVI
retrieves the image data from the individual disk files and treats them as if they were
part of the same input file for processing.
minority analysis A post-classification tool where you enter a kernel size, and the
center pixel in the kernel is replaced with the class value represented by the minority
of the pixels in the kernel.
MNF rotation Minimum Noise Fraction; a transform used to determine the inherent
dimensionality of image data, to segregate noise from the data, and to reduce the
computational requirements for subsequent processing. MNF rotation consists of two
principal component transformations, with a noise whitening step.
MODIS Moderate Resolution Imaging Spectroradiometer; a NASA EOS sensor
aboard the Aqua and Terra satellites.
MODTRAN An atmospheric radiative transfer model developed by the Air Force
Research Laboratory that predicts path radiances and transmissions through the
atmosphere and can be used to describe vertical profiles of water vapor, ozone, and
aerosols. The FLAASH module uses MODTRAN code.
Getting Started with ENVI
214
Appendix 9: Glossary
morphological filter A filter based on mathematical morphology that changes the
shape and connectivity of an object. Unlike a convolution filter that multiplies
neighborhood pixels by values you specify within a kernel, a morphological filter
only works with the data in the neighborhood itself and uses either a statistical
method or mathematical formula to modify the pixel upon which it is focused. The
most common morphological filters are dilation, erosion, opening, and closing.
mosaic A set of overlapping aerial or satellite-based images whose edges are
matched to form a continuous pictorial representation of a portion of the Earth's
surface.
MPEG Moving Picture Experts Group; a data format for digital audio and video.
MRLC Multi-Resolution Land Characteristic; a Landsat TM and DEM data format.
MSS Multispectral Sensor; a Landsat sensor.
multiband file A digital image that contains more than one band of data.
multilooking A method for reducing speckle noise in synthetic aperture radar (SAR)
data and for changing the size of a SAR file by averaging neighboring pixels
throughout the image.
multispectral The ability of a remote sensing instrument to detect wavelengths in
two or more spectral bands.
nadir The point on the ground that lies vertically beneath the perspective center of
the aerial camera lens or satellite sensor.
NDVI Normalized Difference Vegetation Index; a vegetation index used to transform
multispectral data into a single image band whose values indicate the amount of
green vegetation present in the pixel. ENVI uses the standard NDVI algorithm, where
NIR is a near-infrared band:
NDVI = (NIR - Red / NIR + Red)
NITF National Imagery Transmission Format.
NLAPS National Landsat Archive Production System; a Landsat TM and MSS data
format.
NMEA National Marine Electronics Association data format; the NMEA-0183
format is commonly used with a GPS.
NOAA National Oceanic and Atmospheric Administration.
normalize To transform a set of measurements so they may be compared in a
meaningful way. Normalization commonly refers to rescaling minimum and
maximum values between two or more data sets so all of the values range from 0 to 1,
allowing the data sets to be directly compared.
Getting Started with ENVI
Appendix 9: Glossary
215
NSIF NATO Secondary Image Format; a data format similar to NITF that is used by
members of the North Atlantic Treaty Organization (NATO).
object A region of interest with spatial, spectral, and/or texture characteristics
(brightness, color, etc.) that define the region.
object-based processing Techniques that classify a set of input objects rather than
classifying pixels individually.
offset In the context of remote sensing:
•
A correction value added to or subtracted from every pixel in an image,
typically by using image arithmetic (Band Math in ENVI).
•
A variable added to the gain in a regression equation for sensor calibration.
•
The number of bytes of embedded header information present in the file
(ENVI skips these bytes when reading the file).
OLS Operational Linescan System; a NOAA DMSP data format.
orthorectify To remove the effects of radial relief displacement and imaging
geometry from remote sensing imagery.
panchromatic A sensor that detects electromagnetic energy in one very broad band,
which includes most of the visible light spectrum. In aerial photography,
panchromatic refers to a type of film that is sensitive to all wavelengths of visible
light.
PDS Planetary Data System data format.
pedestal height The height of a polarization signature (above 0), calculated by
averaging the following four polarization combinations from SAR data:
Orientation
(degrees)
Ellipticity
(degrees)
0
-45
90
-45
0
45
90
45
Table 9-1: Polarization Combinations
phase image An image derived from polarimetric SAR data whose values represent
the phase difference between the horizontal and vertical polarizations. The phase
Getting Started with ENVI
216
Appendix 9: Glossary
difference is measured in either radians or degrees and ranges from -π to π, or -180
degrees to 180 degrees.
PICT Windows QuickDraw Picture format.
pixel-based processing The traditional approach to exploitation and classification
where each pixel in an image is treated as an independent data point.
Pixel Purity Index A tool used to find the most spectrally pure (extreme) pixels in
multispectral and hyperspectral images. These typically correspond to mixing
endmembers. The PPI is computed by repeatedly projecting n-D scatter plots on a
random unit vector. ENVI records the extreme pixels in each projection (those pixels
that fall onto the ends of the unit vector) and it notes the total number of times each
pixel is marked as extreme. A Pixel Purity Image is created where each pixel value
corresponds to the number of times that pixel was recorded as extreme.
plot function In ENVI programming, a user function that you can add to and call
from the Plot_Function menu of any ENVI plot window.
PNG Portable Network Graphics image format.
polarization signature A plot of radar backscattered power as a function of
ellipticity and orientation angles of the incident radar wave.
polyline A continuous line composed of one or more segments; a vector and
annotation object.
polynomial function A mathematical function with the following form:
f(x) = anxn + an-1xn-1 + … + a1x + a0
Where:
n is a nonnegative integer
an, an-1, etc. are coefficients.
The degree of the polynomial function is the highest value for n, where an is not equal
to 0.
principal components analysis A mathematical technique that transforms a
multivariate data set into a new coordinate system such that the axes, or principal
components, of the new coordinate system are uncorrelated. In remote sensing, an
image is created for each principal component. Because the principal component
rotation maximizes the variance in the first few principal components bands, these
bands usually contain most of the coherent image information and can be used to
isolate features in the data.
Getting Started with ENVI
Appendix 9: Glossary
217
procedure In ENVI programming, a sequence of one or more IDL statements that
you can assign a name (thus creating an IDL program), compile, and call from the
IDL or ENVI command line, using the following form:
PROCEDURE_NAME, Argument [, Optional_Argument]
projected coordinate system A coordinate system that uses Cartesian coordinates
(x,y) to describe a geographic location.
pushbroom sensor Also called an along-track scanner; a sensor with a line array of
small, sensitive detectors stacked side-by-side, where each detector corresponds to a
pixel in the resulting image. As the satellite advances along the ground track, the
array of detectors receives radiation simultaneously. Examples of pushbroom sensors
include ASTER, IKONOS, OrbView-3, QuickBird, SPOT, and CARTOSAT-1.
pyramid layers Copies of a data set at various reduced resolutions. They are used to
speed image display by reducing the resampling required when displaying large
portions of an image at low resolution.
QUAC Quick Atmospheric Correction; an automated atmospheric correction
method in ENVI for retrieving spectral reflectance from multispectral and
hyperspectral images.
QuickBird A Digital Globe high-resolution satellite that provides 61 cm
panchromatic and 2.4 m multispectral imagery.
QuickMap An ENVI feature that allows you to quickly create a map composition
from an image. You can add grid lines, scale bars, titles, north arrows, declination
diagrams, and logos. You can save your settings as a QuickMap template that you can
use with other images.
Quorum A type of receiving station that creates AVHRR 16-bit High Resolution
Picture Transmission (HRPT) files with two header frames. The Quorum format does
not have georeferencing information.
RADARSAT Radar Satellite (Canadian Space Agency).
radiance A measure of the amount of electromagnetic radiation leaving a point on
the surface. More precisely, it is the rate at which light energy is emitted in a
particular direction per unit of projected surface area. The standard unit is W/m2.
Most remote sensing devices directly measure radiance.
raster A grid-based data structure for storing images where each cell, or pixel,
contains a single data value.
reflectance The ratio of radiant energy reflected by a body to the energy incident on
it, usually denoted as a percentage.
Getting Started with ENVI
218
Appendix 9: Glossary
region A broad term that refers to a group of pixels with the same spatial or spectral
characteristics.
register To geometrically align two or more images of the same scene so the images
can be superimposed. The images can come from different viewpoints, different
times, and different sensors. Following are the two most common methods of
registration:
•
Image-to-image registration: Correct a reference (warped) image to match
base image geometry, using tie points between the two images.
•
Image-to-map registration: Assign a reference image to geographic
coordinates, using GCPs with known ground locations.
resample To apply a geometric transformation to an original data set; more
specifically, the interpolation method used to derive output pixel values based on
input pixel values, taking into account the computed distortion. Following are the
most common resampling methods:
•
Nearest neighbor: Each pixel in the output image receives its value from the
nearest pixel in the input (reference) image.
•
Bilinear: Each estimated pixel value in the output image is based on a
weighted average of the four nearest neighboring pixels in the input image.
•
Cubic convolution: Each estimated pixel value in the output image is based on
a weighted average of 16 nearest neighboring pixels in the input image. Cubic
convolution is the slowest method, but it yields the smoothest results.
RGB A color space defined by red, green, and blue values.
RGB color composite An image that uses the red, green, and blue guns of the
display device to form a color additive representation of color.
ROC curve Receiver operating characteristic; a curve used to visualize the
performance of a classification method, in order to select the proper decision
threshold. ROC curves compare a series of rule image classification results for
different threshold values with ground truth information.
ROI Region of interest; a point, polyline, or polygon object drawn on an image, used
to define a specific area of interest for extracting classification statistics, masking,
and other operations in ENVI. From a processing standpoint, ROIs are pixel
addresses with associated data.
RMS error Root mean square error; a statistical measure that represents the
difference between measured and predicted data points. In ENVI, RMS error is often
used to evaluate a set of GCPs for georeferencing:
Getting Started with ENVI
Appendix 9: Glossary
219
Where:
x and y are the original row and column coordinates
x' and y' are the estimated coordinates
routine A general IDL programming term that refers to both functions and
procedures.
RPC Rational polynomial coefficients; used to build interior and exterior orientation
in photogrammetry.
RSM Replacement sensor model; an alternate representation of sensor geometric
information that corrects the deficiencies of RPC-based sensor models. RSM
contains a variety of enhancements over the RPC model, including:
•
Increased accuracy over images with large number of rows or columns (such as
image strips) by breaking the image into tiles with separate models.
•
The ability to store varying degrees of complexity in the polynomial
representation used.
RST Rotation, scaling, and translation; a warping method used in image registration
that uses an affine transformation with at least three ground control points:
x = a1 + a2X + a3Y
y = b1 + b2X + b3Y
rule image An image calculated for each ROI in a supervised classification. They
are called “rule images” because a rule is applied to the pixel values in the images to
determine the class to which each pixel should be assigned. The pixel values in the
rule images, and the rule used to assign classes, depend on the specific classifier used.
For example, with Maximum Likelihood classification, the pixel values in a rule
image for one class are equal to the likelihood that each pixel belongs to that class.
Whichever rule image has the highest likelihood value for a pixel is the class to which
that pixel is assigned.
RXD Reed-Xiaoli anomaly detection algorithm.
sample The x component of a raster image coordinate pair (x,y); same as column.
SAR Synthetic aperture radar.
scale factor A division factor used to convert integer-scaled reflectance or radiance
data into floating-point values. For example, for reflectance data scaled into the range
Getting Started with ENVI
220
Appendix 9: Glossary
of 0 to 10,000, set the scale factor to 10,000. For uncalibrated integer data, set the
scale factor to the maximum value the instrument can measure ((2n) - 1, where n is
the bit depth of the instrument).
scatter plot A plot of measurements from two or more bands of data.
Scroll window The window in a display group that displays the full image at
subsampled resolution. This window appears only when an image is larger than what
ENVI can display in the Image window at full resolution. See “Display Groups” on
page 46 for an example.
SeaWiFS Sea-viewing Wide Field-of-view Sensor; a NASA satellite that collects
global ocean color data.
segmentation The process of partitioning an image into connected regions by
grouping neighboring pixels with similar feature values (brightness, texture, color,
etc.). These segments ideally correspond to real-world objects.
semivariance A statistic that uses the squared difference between neighboring pixel
values to provide a measure of dissimilarity within a dataset. It has the same units as
the input dataset, and its values are greater than or equal to 0.
semivariogram A plot of semivariance values at multiple lag distances; a measure
of how autocorrelation decreases as distance increases.
shaded relief An image created during the topographic modeling process that
renders terrain in 3D by use of graded shadows that would be cast by the sun from a
northwest direction.
shapefile A vector file format; a set of files that contain points, arcs, or polygons
that hold tabular data and a spatial location. One shapefile consists of three individual
files, ending with .shp, .shx, and .dbf file extensions.
shift difference The process of differencing adjacent pixels to the right and above
each pixel and averaging the results to obtain the noise value to assign to the pixel
being processed. The best noise estimate is gathered using the shift-difference
statistics from a homogenous area rather than the whole image.
Sigma nought A measure of the mean backscatter of a radar signal from an area of
1 m2 on the earth's surface, typically denoted in decibels (dB). Sigma nought
describes the backscattering strength of a distributed target, rather than a discrete
target.
SIR-C A synthetic aperture radar (SAR) instrument built by NASA/JPL and Ball
Communication Systems Division for NASA. SIR-C flew aboard the Space Shuttle
and provided L-band and C-band measurements.
Getting Started with ENVI
Appendix 9: Glossary
221
slope The percentage or degree change in elevation over distance; a parameter used
in topographic modeling.
SMACC Sequential Maximum Angle Convex Cone; a sub-pixel spectral tool in
ENVI that finds spectral endmembers and their abundance throughout an image.
smooth To average pixel values within adjacent areas to produce more gradual
transitions.
solar azimuth The angle a horizontal projection of a direct ray from the sun makes
with the True North-south axis, typically denoted as clockwise from True North
through 360 degrees.
solar elevation The angle of the sun above the horizon, extending from 0 degrees
(horizon) to 90 degrees (directly overhead).
solar spectrum The part of the electromagnetic spectrum occupied by the
wavelengths of solar radiation. About 99 percent of solar radiation is constrained to
300 nm (ultraviolet) to 3,000 nm (near-infrared).
spatial filter A filter that removes certain spatial frequencies from an image and
enhances features in the remaining image. Following are the most popular types of
spatial filters:
•
•
•
High pass: Enhances high spatial frequencies. Following is a sample 3 x 3
kernel used for high-pass filters:
-1
-1
-1
-1
9
-1
-1
-1
-1
Low pass: Enhances low frequencies in an image, thus smoothing the image.
Following is a sample 3 x 3 kernel used for low-pass filters:
1
1
1
1
1
1
1
1
1
Edge enhancement: Enhances edges of features in an image, making them
easier to analyze. Following is a sample 3 x 3 kernel used for edge
enhancement filters:
1
1
1
1
-2
1
-1
-1
-1
Getting Started with ENVI
222
Appendix 9: Glossary
spatial profile A plot of pixel values along a line placed in the image.
spatial resolution A measure of the smallest angular or linear separation between
two objects that a sensor can resolve.
Spectral Analyst function In ENVI programming, a user function that implements
a custom spectral mapping method to match an unknown spectrum to the materials in
a spectral library. You can add this user function to ENVI's Spectral Analyst and call
it from the ENVI menu system.
spectral library A collection of spectra measured in the field or laboratory for
materials (minerals, vegetation types, etc.) that are often used as a baseline, or “true”
spectra, for identification of materials from spectral remote sensing imagery.
Spectral mapping method Also called a spectral similarity technique; a method in
hyperspectral analysis for matching image spectra to known (reference) spectra,
usually from a spectral library. Following are descriptions of the spectral mapping
methods used in ENVI.
•
Binary Encoding: A method that encodes data and endmember spectra into
zeros and ones, based on whether a band falls below or above the spectrum
mean, respectively.
•
Linear Spectral Unmixing: A sub-pixel method that determines the relative
abundance of materials depicted in multispectral or hyperspectral imagery
based on the materials' spectral characteristics.
•
LS-Fit: A linear band prediction method that uses least-squares fitting. You
can use it to find regions of anomalous spectral response in a dataset. It
calculates the covariance of the input data and uses it to predict the selected
band as a linear combination of the predictor bands plus an offset.
•
Matched Filtering: A method that finds the abundance of user-defined
endmembers using a partial unmixing technique. Matched filtering maximizes
the response of a known endmember and suppresses the response of the
unknown background, thus matching the known signature. It provides a rapid
means of detecting specific materials based on matches to library or image
endmember spectra and does not require knowledge of all the endmembers
within an image scene.
•
Mixture Tuned Matched Filtering (MTMF): A method that performs
Matched Filtering and adds an infeasibility image to the results. The
infeasibility image is used to reduce the number of false positives that are
sometimes found when using Matched Filtering.
•
Spectral Angle Mapper (SAM): A physically-based spectral classification
method that uses an n-D angle to match pixels to reference spectra. The
Getting Started with ENVI
Appendix 9: Glossary
223
algorithm determines the spectral similarity between two spectra by
calculating the angle between the spectra and treating them as vectors in a
space with dimensionality equal to the number of bands.
•
Spectral Feature Fitting (SFF): A method that compares the fit of image
spectra to reference spectra using a least-squares technique. SFF is an
absorption-feature-based methodology. The reference spectra are scaled to
match the image spectra after the continuum is removed from both data sets.
Spectral Math An ENVI tool that allows you to apply mathematical expressions or
IDL procedures to spectra and to selected multiband images, as long as the number of
bands and spectral channels match.
spectral profile see Z Profile.
Spectral Hourglass Wizard A tool in ENVI that takes you through a step-by-step
process for locating spectral endmembers within a hyperspectral data set and
mapping their locations and sub-pixel abundances. When written in a certain format,
the processing flow resembles an hourglass shape. See Spectral Hourglass Wizard in
the ENVI User’s Guide for a diagram of the hyperspectral processing flow.
spectral resolution The wavelength range that a particular band measures. For
example, Landsat-7 ETM+ Band 1 detects wavelengths from 0.45 μm to 0.52 μm.
The Landsat-7 ETM+ panchromatic band detects wavelengths from 0.50 μm to 0.90
μm. So, Band 1 has a finer spectral resolution than the panchromatic band. Spectral
resolution does not refer to the number of bands available from a particular sensor.
SPOT Satellite Pour l'Observation de la Terra; a series of earth observation satellites
launched by Spot Image of France; the spatial resolution of SPOT data varies from
2.5 to 20 m.
SRF Spectral response function; engineering data that quantify the spectral response
and sensitivity of detectors on an airborne or satellite sensor. The term SRF also
refers to a data format that contains SRF data for particular sensors.
SRTM Shuttle Radar Topography Mission (NASA/JPL).
statistics Numbers or values that help describe the characteristics of a selected
group of data.
stretch See contrast stretch.
subsample To create an output image of reduced resolution based on every nth pixel
from an input image.
super GLT A geographic lookup table (GLT) file that contains information about
how many and which input pixels contribute to the output pixel; a super GLT is not an
image file.
Getting Started with ENVI
224
Appendix 9: Glossary
synthesize With respect to polarimetric radar data, the process of building an image
representing backscatter at specified ellipticity and orientation angles from a
scattering (or related) matrix.
system calibration The process of converting digital numbers (DNs, which
represent the sensor response) in a remote sensing image to radiance or reflectance
above the atmosphere, using pre-launch gain and offset values.
temporal resolution How often a sensor obtains imagery of a particular area.
texture The frequency of change and spatial arrangement of pixel values in an
image, as a function of spatial scale. A flat image in which all digital numbers (DNs)
are equal is said to have a uniform texture.
texture filter A filter used to delineate surface features (for example, biophysical
properties of a forest canopy) that cause local variations in image brightness. A
texture filter is helpful for identifying objects that are more characterized by their
texture than by intensity.
thermal band A band that detects radiation from the far infrared part of the
electromagnetic spectrum, between approximately 7.0 to 15 μm. A thermal band
detects emitted, rather than reflected, radiation from the earth.
threshold A value above which a process is performed and below which it will not
be performed. For example, you can specify a change threshold of 50 percent in a KMeans supervised classification, which means the clustering process ends when the
number of pixels in each class changes by 50 percent or less.
tie points The location of a single feature across two overlapping images, used in
image-to-image registration.
TIFF Tagged Image File Format.
tile For ENVI to process images that are much larger than the total amount of RAM
available on the system, large images are broken into pieces that are small enough for
the system to handle. Each piece is called a tile. When the image is processed, only
one tile is read into memory at a time.
TIMS Thermal Infrared Multispectral Scanner; a NASA/JPL and Daedalus
Enterprises sensor.
TM Thematic Mapper; a Landsat sensor.
TOPSAR Topographic Synthetic Aperture Radar; a NASA/JPL airborne radar
interferometer.
transform An image processing operation that changes data to another data space,
usually by applying a linear function. The goal of most transforms is to improve the
Getting Started with ENVI
Appendix 9: Glossary
225
presentation of information. Transformed images are often more easily interpreted
than the original data.
true-color composite An image where the red band (0.6 μm to 0.7 μm) is displayed
in red, the green band (0.5 μm to 0.6 μm) is displayed in green, and the blue band (0.4
μm to 0.5 μm) is displayed in blue.
user-defined RPC reader In ENVI programming, a user function that reads a
custom rational polynomial coefficients (RPC) file format. You can add the user
function to, and call it from, the Generic RPC menu option in ENVI.
user function A custom program that you can write in IDL, C, Fortran, or another
high-level programming language that performs an interactive ENVI processing task.
If you write a user function in IDL, you can incorporate ENVI library routines into
the code and call the user function from the ENVI menu system to run it.
USGS United States Geological Survey.
UTD Uniform Target Detector; an anomaly detection algorithm in which the
anomaly is defined using (1 - μ) as the matched signature, rather than (r - μ). UTD
and the RXD algorithm work exactly the same, but instead of using a sample vector
from the data (as with RXD), UTD uses the unit vector. UTD extracts background
signatures as anomalies and provides a good estimate of the image background.
UTM Universal Transverse Mercator map projection; a system of plane coordinates
based upon 60 north-south zones, each 6 degrees of longitude wide, that circle the
earth. UTM coordinates consist of the Zone number, an easting (distance in meters or
kilometers east of the western edge of the Zone), and a northing (distance in meters or
kilometers from the equator).
vector A data structure for storing spatial data that consists of points, lines, and
polygons. Lines (also called arcs) are defined by beginning and end points, which
meet at nodes. The locations of these nodes and the topological structure are usually
stored explicitly.
vegetation index A measure of some vegetation property calculated from reflected
solar radiation measurements made across the optical spectrum (400 to 3,000 nm). A
vegetation index is constructed from reflectance measurements in two or more
wavelengths to analyze specific characteristics of vegetation, such as total leaf area
and water content. See ENVI Help for the names and definitions of each vegetation
index calculated in ENVI.
vertical exaggeration The process of multiplying all of the elevation values in a
DEM by a scale factor to exaggerate the landscape's relief when viewed in a 3D
perspective.
Getting Started with ENVI
226
Appendix 9: Glossary
virtual border An annotation object that consists of a temporary border around an
image displayed in ENVI. You can enter the border width (in pixels) and place other
annotation objects within the virtual border.
Virtual Mosaic A saved mosaic template used as an alternative to saving a mosaic to
disk. When you restore a Virtual Mosaic template file, ENVI opens the individual
image files that make up the mosaic and puts them together on the fly. You can
display a Virtual Mosaic file in ENVI and annotate it, stretch it, etc., like any other
image. Using a Virtual Mosaic prevents multiple files from containing the same
images and therefore saves disk space.
warp To stretch an image to fit its ground control points (GCPs), so that distance and
area are uniform in relationship to real-world measurements. ENVI performs warping
with rotation, scaling, and translation (RST); polynomial, or Delaunay triangulation.
wavelength Velocity divided by frequency of an electromagnetic wave. In general,
the mean distance between maxima or minima of a roughly periodic wave pattern.
widget A simple graphical object such as a push button or slider, created in IDL, that
allows user interaction with a pointing device (usually a mouse) and a keyboard. You
can construct and manipulate graphical user interfaces in IDL using widgets.
WorldView-1 A Digital Globe high-resolution satellite that provides 50 cm
panchromatic imagery.
WorldView-2 A Digital Globe high-resolution satellite that provides 46 cm
panchromatic imagery.
X Profile and Y Profile A cross-section of data along the x-axis, and y-axis, of an
image, respectively. X and Y Profiles are also called horizontal and vertical profiles,
respectively.
XWD X Windows Dump
XSTART and YSTART Variables in an image header file that define the image
coordinates for the first pixel in the image. For most images, ENVI sets the default
XSTART and YSTART values to 1, defining the first pixel in an image with a
coordinate of (1,1). Thus, if the image were an IDL 2D array variable, the data
contained in subscript position [0, 0] correspond to image coordinates (1,1). If
XSTART or YSTART are set to any other values (including negative numbers or 0),
the image coordinates begin incrementing from these values.
Z Profile A spectrum plot of the pixel under the cursor, through all bands of the
image.
Zoom box The red box inside an Image window that defines the extent of the Zoom
window. See “Display Groups” on page 46 for an example.
Getting Started with ENVI
Appendix 9: Glossary
227
Zoom window The window in a display group that displays the subsection of the
image defined by the Image window Zoom box. The resolution is at a user-defined
zoom factor based on pixel replication or interpolation. See “Display Groups” on
page 46 for an example.
Getting Started with ENVI
228
Appendix 9: Glossary
Getting Started with ENVI
Index
A
add-on modules, 16
ArcMap
exporting image files to, 41
exporting vector layers to, 62
ASCII
output from DEMs, 172
output from images, 171
available bands list, 39
closing files, 42
color composites, 109
displaying images, 107
folding and unfolding datasets, 40
gray scale images, 108
hiding and showing, 43
locating bands by wavelength, 45
opening files, 41
Getting Started with ENVI
opening files in ENVI Zoom, 42
right-click menus, 44
true-color and color-infrared images, 109
available files list, 162
editing ENVI header, 163
opening new files, 163
available vectors list, 61
editing layer names, 63
opening files, 62
opening vectors in ENVI Zoom, 62
saving layers, 64
starting new vector windows, 63
supported data types, 61
B
BIL format, 29
229
230
BIP format, 29
blocking IDL command line, 186
BSQ format, 29
C
color buttons, 135
color composite images, 109
color-infrared images, 109
colors
editing system preferences, 182
preventing color flashing, 193
combining bands, 168
compressing output, 141
contacting ITT, 21
copyrights, 2
crosshair cursor, 54
cross-platform file portability, 32
cursors
crosshair, 54
custom development services, 22
customizing
See also programming in ENVI.
color flashing, 193
display group menu bars, 194
ENVI configuration files, 194
ENVI main menu bars, 194
fonts on UNIX, 192
multiple Windows PC users, 188
platform dependencies, 191
pseudocolor, 193
right-click menus, 195
SCSI tape support, 192
UNIX, 189
window auto-placement, 192
D
data types
changing in ENVI header, 125
Index
DDF format, 103
default output directories, 176
DEMs
output to ASCII, 172
DGN format, 103
dialog components, 134
display groups, 46
hiding zoom and scroll windows, 50
maximizing, 49
opening new, 48
output options, 173
positioning zoom and scroll windows, 49
preferences, 181
resizing, 48
scroll bars, 49
DLG format, 103
drop-down buttons, 134
drop-down lists, 134
DXF format, 103
E
e00 format, 103
ENVI + IDL licenses, 11
ENVI configuration files, 194
ENVI header file, 114
changing data types, 125
creating, 123
cross-platform portability, 32
editing, 127
format
required parameters, 125
ENVI image format, 29
output, 168
ENVI licenses, 11
ENVI vector files. See EVF
EVF, 103
exiting ENVI, 28
external file formats, 101
Getting Started with ENVI
231
F
favorite servers, 98
file formats, 33
ASCII
file types (filetype.txt), 128
sensor types (sensor.txt), 130
ENVI images, 29
supported
input, 33
output, 35
file management
available files list, 162
closing all files, 163
opening files, 81
saving images, 168
file naming conventions, 31
cross-platform portability, 32
extensions, 31
file types, 128
finding windows, 56
folding datasets, 40
fonts
setting for UNIX, 192
G
geodatabases, 86
connecting to enterprise, 96
opening, 97
refreshing, 94
retaining display enhancements when saving,
65
saving, 64
glossary, 199
graphics colors, 182
gray scale images, 108
See also ENVI header file
I
IAS servers, 85
connecting, 96
summary, 85
IDL, 11
command line blocking, 186
exporting variables, 197
importing variables, 196
newsgroup, 23
image windows, 46
crosshairs, 54
displaying scroll bars, 49
maximizing, 49
mouse button functions, 76
opening new, 48
positioning zoom and scroll windows, 49
resizing, 48
images, 82
displaying, 107
ENVI format, 29
opening files, 82
saving, 168
saving display groups, 173
increase/decrease buttons, 135
input file dialogs, 136
input file formats, 33
interactive analysis tools
pixel locator, 149
interleaving
BIL, 29
BIP, 29
BSQ, 29
J
H
headers
Getting Started with ENVI
JPEG 2000 format, 85
servers, 85
Index
232
JPIP servers, 85
connecting, 96
summary, 85
L
legalities, 2
licensing
ENVI, 11
ENVI + IDL, 11
ENVI modules, 16
M
menus, 38
definition files, 194
meta files, 170
MIF format, 103
modules, 16
Atmospheric Correction, 16
DEM Extraction, 16
FLAASH, 16
NITF/NSIF, 17
QUAC, 16
mouse buttons, 75
emulating on Macintosh, 75
image windows, 76
plot windows, 79
scroll windows, 77
vector windows, 78
zoom windows, 76
N
NITF
IAS servers, 86
Index
O
OGC servers, 84
connecting, 96
keywords, 88
summary, 84
WCS, 84
WMS, 84
opening files
external, 101
images, 82
ENVI format, 29
previous, 102
spectral libraries, 106
vectors, 103
output
directories, 176
display options, 173
file vs. memory, 139
printing, 174
output formats, 35
ASCII, 171
ENVI images, 29, 168
ENVI meta files, 170
supported types, 35
overlays
ROIs
P
pixels, 149
locations, 149
platform dependencies, 191
plots, 73
closing, 74
mouse button functions, 79
new windows, 74
output options, 173
windows, 73
preferences, 178
colors, 182
Getting Started with ENVI
233
previous files
opening, 102
printing, 174
processing status, 147
windows, 147
Professional Services Group, 22
pseudocolor in UNIX, 193
R
radio buttons, 134
reduced resolution data sets
regions of interest. See ROIs
remote datasets, 83
authentication, 90
connecting directly to JPIP, IAS, OGC
datasets, 86
connecting to servers and geodatabases, 91
connection properties, 96
editing properties, 95
favorites, 98
managing, 91
specifying URLs, 96
RGB, 109
displaying images, 109
ROIs
Rsets. See reduced resolution data sets
S
saving
See also output formats.
data to IDL variables, 197
images, 168
scripts
saving sessions, 27
startup, 26
scroll bars, 49
scroll windows, 46, 55
controlling, 55
Getting Started with ENVI
hiding, 50
meta zoom, 56
mouse button functions, 77
positioning, 49
resizing, 48
SCSI tape support, 192
sensor types, 130
SHP format. See shapefiles
spectral libraries
opening files, 106
starting ENVI, 26
startup scripts, 26
format, 26
saving sessions, 27
T
technical support, 21
toggle buttons, 135
trademarks, 2
training, 22
true-color images, 109
U
uncompressing files, 141
unfolding datasets, 40
UNIX
preventing color flashing, 193
pseudocolor, 193
setting fonts, 192
window auto-placement, 192
V
vector windows, 68
cursor tracking, 71
mouse button functions, 78
opening new, 63
panning, 71
Index
234
starting new, 71
zooming, 71
vectors
available vectors list, 61
layers
editing names, 63
saving, 64
opening files, 103
output types, 173
auto-placement on UNIX, 192
finding, 56
plot, 73
processing status, 147
vector, 68
WMS servers, 84
connecting, 96
summary, 84
Z
W
wavelengths
locating bands, 45
WCS servers, 84
connecting, 96
summary, 84
windows
See also display groups.
Index
zoom windows, 46
controlling, 52
crosshairs, 54
hiding, 50
interpolating, 54
mouse button functions, 76
positioning, 49
resizing, 48
Getting Started with ENVI
Download PDF