Evaluating Roughness Models of Radar Backscatter

A unique set of data collected for a soil moisture experiment has been used to evaluate three radar backscatter roughness models. The data were collected by the NASA Space Shuttle flight 41G (SIR-B) synthetic aperture radar (SAR) in an intensively farmed area near Fresno, California. The SIR-B data swath included a large number of bare dry fields with a large variety of surface roughnesses. The small perturbation model gave the best results, particularly when fields with a definite periodic row structure were omitted. The standard deviation of surface heights appears to be a good measure of relative roughness conditions, but the correlation length did not appear to be a good descriptor of the surface nor did it seem to be related in any way to the measured backscatter.