The Recognition of Extended Targets: SAR Images for Level And Hilly Terrain

An experiment was performed using radar image simulation techniques to determine what a SAR image would look like for a collection of area extensive targets, first with flat underlying terrain and second, in the presence of moderate relief. Although compression, layover, and shadow are well known from the one-dimensional geometry analyses, it has not been previously demonstrated in a pictorial fashion what happens to the appearance of the same controlled reflectivity pattern, for level and hilly ground. It is not surprising to radargrammetrists that even modest elevation changes seriously affect the detection and recognition of boundaries and shapes. The image results clearly demonstrate these effects, and are valuable for many researchers who have previously used, or are just beginning to apply SAR imagery to crops and soils, minerals, and water resources assessment, etc. This research was performed during the course of an investigation to establish the performance of the Seasat-A SAR, in terms of user-oriented features, thus the radar system model and geometry are pertinent to that sensor, although the results can be applied to radar imaging in general. A review of range perspective imaging is included, since information extraction from radar imagery necessitates the knowledge of geometry/propagation effects.