REPEAT-PASS SAR INTERFEROMETRY OVER FORESTED TERRAIN

Repeat-pass synthetic aperture radar (SAR) interferometry provides the possibility of producing topographic maps and geocoded as well as rad iometrically calibrated radar images. However, the usefulness of such maps and images depends on our understanding of how different types of terrain affect the radar measurements. It is essential that the scene coherence between passes is sufficient, In this paper, we derive a ge neral system model including both radar system and scene scattering pr operties, The model is used to interpret measurements over a forested area where the scene coherence varies between 0.2 and 0.5. The coheren ce is found to be sensitive to temperature changes around 0 degrees C but surprisingly insensitive to wind speed. The interferometric height discontinuity at the forest to open-field boundary shows good agreeme nt with in situ tree height measurements for a dense boreal forest, bu t is observed to decrease for a less dense forest. This suggests the p ossibility of estimating bole volume from the interferometric tree hei ght and a ground DEM. The decrease of scene coherence over a dense for est with increasing baseline is also used to estimate the effective sc attering layer thickness.