International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B3. Istanbul 2004 
6.4.1 Geocoded Terrain Corrected (GTC) 
The experimental GTC processor will produce a multi-look 
detected product supporting at least the same cartographic and 
geodetic references as the EEC (UTM/UPS and WGS84). The 
image distortions caused by varying terrain height are corrected 
using an external high resolution DEM. Ground control point 
measurement and image adjustment ensure that the image 
geometry will be of sufficient quality even for quick-look and 
rapid orbit input. The rigorous geocoding approach will be 
applied (s. chapter 2.2). Optionally the GIM is generated. 
The experimental GTC processor supports input of the 
TerraSAR-X basic products in single look complex and multi- 
look ground range geometry. Additionally the so called 
enumeration files can be generated. 
6.4.2 Enumeration Files 
The enumeration files are an alternative geocoded product, 
which provides the ground co-ordinates along with the input 
SAR scene. Thus geo-referencing can be performed by the end- 
user without the need for image interpolation. To deliver this 
information two image layers are attached to the SAR image. 
They contain the ground co-ordinates for each input image 
pixel in Easting and Northing, respectively. 
The enumeration files generation is based on the object-to- 
image. approach. For each pixel in the output domain the 
corresponding position in the input SAR image is determined. 
As this step provides a irregular spaced grid it is in a subsequent 
step resampled to a regular spacing in azimuth and range. 
7. CONCLUSION 
TerraSAR-X is a new German radar satellite. Its high frequency 
X-band SAR sensor can be operated in different modes and 
polarisation ranging from SpotLight-, StripMap- to ScanSAR- 
modes. Single and dual polarisation will be available 
operationally, quad-polarised data on an experimental basis. 
Geocoded ellipsoid corrected will be available as well as an 
enhanced ellipsoid corrected product that considers DEMs of a 
moderately coarser resolution than the TerraSAR-X modes. 
SRTM will serve as backbone for this global ortho-rectification 
service. The geocoding sub-system will be integrated into the 
SAR processor TMSP and will be operated on a multi-processor 
Unix computers directly at the receiving station in Neustrelitz. 
An experimental GTC-processor will be implemented that 
enables the high precision geocoding using high using 
resolution DEMS, tie-pointing and image adjustment. 
Three geocoding approaches will be applied to produce the 
GEC, EEC and GTC. The rigorous approach is the most 
accurate. The 3d interpolative approach provides comparable 
results but with higher throughput. The interpolative ellipsoid 
correction does not consider a DEM contrary to rigorous and 3d 
interpolative geocoding. 
8. REFERENCES 
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Frey O., Meier E., Niiesch D., Roth A. 2004. Geometric Error 
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