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, /spl sigma//sub 0/, and the maximum height, h/sub max/, of the rocks making up the arid landscape. The simplified relationship /spl sigma//sub 0/=4.63.1og h/sub max/-15.29 (with h/sub max/ in cm and /spl sigma//sub 0/ in dB) was established from field measurements, giving an r/sup 2/ of about 88%. This empirical relationship is confirmed by another close relation between /spl sigma//sub 0/ and the statistical parameter s, the height standard deviation. The advantage of h/sub 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.