An empirical model for interpreting the relationship between backscattering and arid land surface roughness as seen with the SAR

The nature of the surface in a flat arid zone located in the western Sahara desert was studied and its roughness parameters defined, The main geological units were compared with backscattering data from ERS-1 images. Results showed a close correlation between the backscattering coefficient, sigma(0), and the maximum height, h(max), of the rocks making up the arid landscape, The simplified relationship sigma(0) = 4.63.log h(max) - 15.29 (with h(max) in cm and sigma(0) in dB) was established from held measurements, giving an r(2) of about 88%. This empirical relationship is confirmed by an other close relation between sigma(0) and the statistical parameter s, the height standard deviation, The advantage of h(max) is that it can be extracted for any site, whatever its roughness may be, The spatial distribution of the rock facets and the geometric characteristics of the incidence angle of the radar signal seem to explain the results.