Bias in Ampcor Offsets
Large bias in the ampcor offsets (i.e. more than 0.25 pixels in range offsets or more than 0.5 pixels in azimuth offsets) is often associated with processor-induced phase ramp in the interferogram, especially after residual motion correction. However, bias in the ampcor offsets and phase ramp in the interferogram could also be due to real physical changes in the scene. Extra careful analysis must be done to extract scientific results from data marked with this issue.
Example of ampcor range offset biased by around -0.5 pixel:
Example of unbiased ampcor range offset:
Example of resulting phase ramp in the interferogram after residual motion correction from the above left biased range offset. The high-frequency aircraft motion banding is reduced, but a phase ramp perpendicular to the flight track is introduced.
Uncorrected interferogram phase
Corrected interferogram phase
