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1.5.2017 : 8:14 : +0200

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.

Related Documents

DIFF&GEO Flowcharts

Flow chart of the geocoding part of the DIFF&GEO package
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)