DECORRELATION IN INTERFEROMETRIC RADAR ECHOES

A radar interferometric technique for topographic mapping of surfaces promises a high resolution, globally consistent approach to generation of digital elevation models. One implementation approach, that of utilizing a single synthetic aperture radar (SAR) system in a nearly repeating orbit, is attractive not only for cost and complexity reasons but also in that it permits inference of changes in the surface over the orbit repeat cycle from the correlation properties of the radar echoes. Here we characterize the various sources contributing to the echo correlation statistics, and isolate the term which most closely describes surficial change. We then examine the application of this approach to topographic mapping of vegetated surfaces which may be expected to possess varying backscatter over time. We find that there is decorrelation increasing with time but that digital terrain model generation remains feasible. We present such a map of a forested area in Oregon which also includes some nearly unvegetated lava flows, and find that temporal decorrelation contributions to the height errors may be limited to 1.5 and 2.6 m for the forested and lava areas, respectively, if suitable attention is given to experiment design. Such a technique could provide a global digital terrain map.