The term Range-Doppler designates the timely ordered subsequence of processing steps of which the Most 
important are 
® Range Compression, 
© Azimuth Compression and 
9 Interpolation. 
The penalty for breaking up the twodimensional nature of the imaging process into two onedimensional pro- 
cedures comprises in two additional processing steps which take care for earth rotation and for effects due to 
varying across track distance to a target during integration time. 
There is a requirement that the software shall be implemented in a high level language. Additionally there shall 
be an integrated software development system covering all phases of the software lifecycle. An analysis of 
all development systems on the market showed a large variety of products all of which had some deficiencies, 
From that point of view ADA has been chosen as implementation language, because it includes its own 
development environment. 
All central parts of the software system will be managed by the expert system running on the KEW which 
controls the whole production process by 
receiving production orders from the PAF, 
configuring the production process, 
supervising the correlation sequence and 
supporting the operator in all decisions processes. 
Up to that point all processing is related to products of level 1.5. The generation of all higher level SAR 
products of the German PAF will be described in the subsequent chapter. 
4. The Geocoding Workstations 
The term Geocoding describes the task, which accepts digital SAR image data sets from the Preprocessing 
System and generates geometrically corrected and precisely located Geocoded Products in different map pro- 
jections. The high accuracy shall be achieved using precise orbit/attitude data, Ground Control Points and 
Digital Elevation Models. The achieved accuracy shall be within the range of the pixel size. The throughput 
design goal for the Geocoding System is to produce an average of 8 Geocoded Products per day or 2000 
products per year. 
The precision Geocoding of SAR images is a task which requires both, an image display system for the 
interactive subtasks such as registration and quality control and a high performance processor for the recti- 
fication tasks which are required for the rotation and resampling of large data matrices with high throughput. 
The hardware to be selected shall be compatible with other systems presently used at the German Remote 
Sensing Data Center. 
The DFD has started to implement a network of UNIX-workstations, all interfaced to a Local Area Network, 
with some of these workstations performing image processing tasks. The UNIX-workstation concept was cho- 
sen deliberately to become as far as possible indepent of the selected hardware configuration for future software 
developments. In addition to that, such workstations are cheap compared to minicomputers and the use of 
several identical workstations increases the throughput capability and the operational reliability. 
Present plans are to implement three workstations for the SAR Geocoding task. Though the final decision for 
the manufacturer has not been made, a state of the art workstation SUN-3/160 from SUN Microsystems, Inc. 
is being used as model configuration (see Figure 4). 
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