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This paper discusses the potential of radar signal to characterise the bare surface roughness in and or semi-arid regions. Two different scales have been considered with two microwave sensors: high resolution ERS/SAR and low resolution ERS Wind Scatterometer instruments. Ground truth measurements were acquired over different and sites in the South of Tunisia. An empirical approach is proposed to derive the surface roughness from SAR measurements. In this approach, the surface roughness is characterised by a parameter called Zs.

Then, a good correlation between SAR and WSC data is demonstrated. Using these two sensors, we are able to derive the backscattering signal versus incidence angle, in the cases of big sand dunes, rocky relief and others. An empirical model is then proposed to retrieve the sand dune percentage within the different cells of the WSC. Keywords: SAR, Wind scatterometer, roughness, dunes.