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The GAMMA SAR and Interferometry Software is a collection of programs that allows processing of SAR, interferometric SAR (InSAR) and differential interferometric SAR (DInSAR) data for airborne and spaceborne SAR systems. The software supports the entire processing from raw data to high level products such as digital elevation models, displacement maps, point target analysis and landuse maps. The software is arranged in packages, each dealing with a specific aspect of the processing. Learn more...

The GAMMA Software runs on any Unix or Linux system as well as on Win32-based platforms (W2K, Windows XP). Recommended OS is Linux. Any distribution should work as long as the GTK toolkit is version 2.8.12 or higher. A nice free distribution is Ubuntu. Both 32- and 64-bit processors are supported on Linux. On Windows and Solaris a 32-bit environment is needed. The GAMMA Software is also known to run on OS-X and other *IX systems. Contact GAMMA if you have special needs.

With its functionality, flexibility, robustness, efficiency, and competitive price, GAMMA software is an excellent solution for demanding processing jobs. This has been demonstrated by license sales to users at many leading institutes world-wide, since 1995. Another distinct advantage of the GAMMA software is the competent user support provided directly by the developers and experienced users of the software and the availability of ad-hoc and training courses.
 
Modular SAR Processor
The Modular SAR Processor (MSP) is a system for deriving synthetic aperture radar images from raw SAR data from both airborne and spaceborne sensors. The MSP calculates from raw data single look complex (SLC) and multi-look intensity (MLI) images in radar slant range/Doppler coordinates. The processing includes radiometric calibration and is phase preserving for interferometric processing.
 
The main taks of the MSP are
preparation of raw SAR data in the GAMMA Software format for processing
pre-processing and data conditioning
range compression with optional azimuth prefiltering
autofocus
azimuth compression
multi-look post processing
A flow chart for the MSP is shown beside. For motion compensation of airborne data the advanced motion compensation is required.
MSP Flowchart
(click image to enlarge)
 Software Brochure
 
Interferometric SAR Processor
The Interferometric SAR Processor (ISP) package encompasses a full range of algorithms required for the generation of interferograms, height maps, coherence maps, and differential interferometric products. The ISP allows:
 
baseline estimation from orbit data
precision registration of interferometric image pairs
interferogram generation (including common spectral band filtering)
removal of flat Earth phase trend
estimation of interferometric correlation
adaptive filtering of interferograms
phase unwrapping
precision estimation of interferometric baselines from ground control points
generation of topographic height
image rectification and interpolation of interferometric height and slope maps
The flow chart for a typical interferometric processing is shown beside. Quality control
programs complement the main processing sequence.
ISP Flowchart
(click image to enlarge)
 Software Brochure
 
Differential Interferometry and Geocoding package
The Differential Interferometry and Geocoding (DIFF&GEO) package is a collection of programs designed to support the differential interferometric processing of SAR data as well as geocoding between range-Doppler coordinates and map projections. The reason for inclusion of these quite different processes into one package is that geocoding capability is required for 2-pass differential interferometry.

Geocoding is the coordinate transformation between the coordinates of an imaging system, in this case range-Doppler coordinates of the SAR, and orthonormal map coordinates. Geocoding is necessary to combine information retrieved by the imaging system (e.g. the SAR image and products derived from it) with information in map coordinates (e.g. a digital elevation model, a landuse inventory, geocoded information from optical remote sensing, etc.). In addition inverse geocoding, i.e. the coordinate transformation from orthonormal map coordinates to the range-Doppler coordinates, is required for 2-pass differential interferometry, namely for the simulation of the interferometric phase (in range-Doppler coordinates) from the DEM in map coordinates.

Figures beside show the flow chart of respectively the geocoding part and the differential interferometry part of the DIFF&GEO package. The selected approach is very flexible as it allows calculating the geocoding lookup table based on a DEM in map coordinates as well as based on an interferometric height estimate in range-Doppler coordinates. A variety of approaches for 2-, 3-, and 4-pass differential interferometry are supported. The processing scheme showing the different approaches to differential interferometry is summarized in Figure 4.

The DIFF&GEO package extends the functionality of the ISP. It is therefore recommended that it is used in combination with the ISP.
 
DIFF&GEO Flowcharts
Flow chart of the geocoding part of the DIFF&GEO package. The topography may either be known in map or range-Doppler coordinates. (click image to enlarge)
   
Flow chart for differential interferometry processing methods. The selection of the appropriate method depends on the availability of a digital elevation model (DEM) and on the capability to unwrap the interferometric phase (cpx stands for the complex interferograms, unw for the unwrapped phase image, sim_unw for the simulated unwrapped topographic phase calculated from the DEM). The processing chains for 3- and 4-pass differential interferometry are identical except that no additional registration step is required in the 3-pass approach if both interferometric pairs use the same scene as reference geometry. (click image to enlarge)
 Software Brochure
 
Interferometric Point Target Analysis
The Interferometric Point Target Analysis (IPTA) package is a collection of tools to exploit the temporal and spatial characteristics of interferometric signatures collected from point targets to accurately map surface deformation histories, terrain heights, and relative atmospheric path delays. The analysis can be summarized as an iterative improvement of the model parameters to achieve an optimal match to the observed interferometric phases. The analysis is done for a selected list of points which correspond to point target candidates, which dramatically improves efficiency and storage requirements.

The advantage of using point targets is that these do not exhibit geometric decorrelation such as distributed targets, permitting a more complete use of the data as even pairs with very long baselines can be interpreted, resulting in improved accuracies and temporal coverage. An important element of the IPTA is the analysis across the data stack, respectively in the time dimension. The IPTA is fully compatible with the other GAMMA Software packages - identical phase models are used and programs to convert between the raster and vector data formats are included. Therefore it is easy to use IPTA in combination with traditional InSARtechniques and use in a synergetic way the strengths of the two methods combined.
 
 Software Brochure
 
GAMMA SAR Geocoding and Image Registration Software
The GAMMA SAR Geocoding and Image Registration Software (GEO) is a collection of tools for SAR geocoding and multi-source image registration. Geocoding is the coordinate transformation between the coordinates of an imaging system, in our case the range-Doppler coordinate of the SAR, and orthonormal map coordinates. Geocoding is necessary to combine information retreived by the SAR system with information in map coordinates (e.g. a topographic map, a landuse inventory, a geocoded optical data set). GAMMA's concept for the automation of the SAR geocoding includes advanced cross-correlation algorithms for precise image registration between the SAR image and a reference image in map geometry which can be a SAR image simulated from a Digital Elevation Model (DEM) or a geocoded optical image. Functionality includes:
 
generate multi-look intensity image (MLI) in slant range geometry
co-register multiple images in slant range geometry
SAR geocode without refinement: slant range and ground range to map geometry, with DEM (terrain corrected) / slant range and ground range to map geometry, without DEM (ellipsoid corrected)
SAR geocode with refinement: slant range and ground range to map geometry, with DEM (terrain corrected) / slant range and ground range to map geometry, without DEM (ellipsoid corrected)
co-register multiple images in map geometry (different SAR systems, different track geometries, different incidence angles, SAR-optical imagery)
additional functionality like mosaicing, data type conversions, use of precision orbits, radiometric calibration
display and rasterfile generation tools
 
 Software Brochure
 
Land Application Tools
The GAMMA Land Application Tools (LAT) package is a collection of programs designed to support data processing in the context of using SAR and SAR interferometry for land applications. The LAT includes special programs for filtering, parameter estimation, and data visualization. There are programs to select test areas, and to extract the corresponding signatures. In addition, the LAT supports simple classification schemes and image mosaicing. More in detail, the LAT package includes programs for:
 
parameter estimation classification filtering
test-area analysis data format conversion visualization
autofocus mosaicing    
 Software Brochure
 
Display Tools
Essential for making full use of the GAMMA Software is a set of tools that can display results on the screen and produce raster image products for documentation and archive purposes. The programs within the Display Tools and Utilities (DISP) package are organized by data type and display functionality. The DISP package is bundled with any of the individual GAMMA Software packages. Supported input data include:
 
raw SAR data and byte images
single look complex and detected multi-look intensity SAR images
interferograms, unwrapped phase, and interferometric correlation
DEMs and interferometric height maps, showing both geographic and map-projection coordinates
differential interferometric products such as subsidence maps
display and editing of phase unwrapping flag files
8- and 24-bit SUNraster and bmp image format files
MSP Flowchart
Screenshot of the graphical user interface of the display programs. On the left side you have the view of the dataset (here an interferogram), on the right you have a magnification of a selected area and below informations about a selected point and you can choose which color table should be used.
(click image to enlarge)
 
 Software Brochure
 
Within the DISP package there are also programs for display of multiple data sets, either by merging the data, such as combining intensity and interferometric phase, or rapidly flickering between images of the same type. Each screen display program can access the original data files to extract the data values at the cursor position. The cursor coordinates are calculated in map projection coordinates when DEM or raster data are in a map projection format such as UTM. Graphical editing of the files used to support phase unwrapping is also supported.

The screen display programs were developed using the open source GTK+ toolkit (http://www.gtk.org) that can be compiled to run both under the X or Win32 2000, XP graphic environment. Therefore the user has the same display functionality if running either a Linux or Win32 operating system on an X86 compatible platform.

The screen display and raster image generation programs are parallel in terms of functionality.The images produced can be displayed using either the DISP programs or any other raster image file viewer or imported into a GIS software.