SAR IMAGE SIMULATION AND ANALYSIS OF ALPINE TERRAIN

We describe the implementation of a so-called object-space algorithm t o use a digital elevation model (DEM) and a sensor flight path as inpu t for the production of simulated SAR images. The method aims to achie ve a high geometric accuracy and employs a parametric mapping model ba sed on SAR range and Doppler equations. Information about SAR layover and shadow areas is stored in a so-called 'layover and shadow map'. We simulate ERS-1, X-SAR, and JERS-1 images of high-relief terrain, and compare them with corresponding real images. Manual measurements on th e ERS-1 image show a simulation accuracy of better than 25 m, if suffi ciently accurate sensor parameters are available. A cosine reflectance model delivers a good overall radiometric impression. However, this i s being improved where ground truth exists, most notably on glaciers a nd areas covered with snow. As an application, we discuss the use of t he simulated products for geometric rectification and radiometric cali bration as a prerequisite for thematic analysis. (C) 1998 Elsevier Sci ence B.V. All rights reserved.