PLATFORM MOT ION COMPENSATION 
IN S AR PROCESSING 
Einar-Arne Herland 
Division for Electronics | 
Norwegian Defence Research Establishment 
Kjeller, Norway 
ABSTRACT 
A correction method to compensate for irregular movement of 
SAR platforms has been developed. The information necessary 
for the correction is estimated from the recorded radar data 
itself. In cases where the phase errors are introduced 
solely by velocity variations in the along-track direction, 
the correction algorithm simultaneously performs geometric 
correction of the image in the same direction. The algorithm 
has been applied to real SAR data where a controlled 
velocity variation has been introduced, and the method is 
shown to give satisfactory results. 
1. INTRODUCTION. 
A synthetic aperture radar achieves it high 
resolution in the along-track direction through coherent 
integration of a series of pulse echoes from the same 
target. This requires highly accurate information about the 
recorded phase history for each target, which is equivalent 
to a very accurate distance measurement. If it is assumed 
that the medium through which the electromagnetic waves are 
travelling does not introduce any phase distortions, there 
are two factors that can cause phase errors: 
- irregularly moving platform 
- moving target 
The former is always detrimental, while the effect 
of the latter may or may not be detrimental, depending on 
the application. This paper is only concerned with the 
errors introduced by the former effect. 
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