TOPOGRAPHIC DEPENDENCE OF SYNTHETIC-APERTURE RADAR IMAGERY

The increasing availability of synthetic aperture radar (SAR) remote-sensing imagery for earth-science applications creates the need for reliable computer methods to improve the relationships between SAR observations and the Earth's abiotic, biotic, and cultural resources. In this paper, the topographic effect on aerial and satellite SAR imagery is quantified and corrected using software modified from an earlier normalized-cosine package written for use with optical/infrared remote-sensing imagery. The basic idea is that the incidence angle and forest canopy interactions with the radar beam can be estimated using a digital elevation model (DEM) and near-coincident observations in the red and near-infrared portions of the spectrum. Four different study areas in Canada and three different types of SAR imagery are used to illustrate the topographic dependence; and the degree of accuracy that;can be expected, following the application of these relatively simple radiometric corrections.