Evaluation of radar backscatter models IEM, OH and Dubois using experimental observations

Synthetic aperture radar (SAR) observations have been used in numerous studies to estimate soil moisture and surface roughness, because of their important roles in many domains. The objective of this paper is to validate, on bare soils, the most common surface backscattering models: the semi-empirical models of Oh et al. and Dubois et al., and the theoretical integral equation model (IEM) of Fung et al. This evaluation is based on a large database consisting of C-band SAR images (ERS-2, RADARSAT-1 and ASAR) and ground measurements (roughness and moisture). The discrepancies observed between the radar signals measured by the SAR sensors and those predicted by the models have been correlated with radar incidence angle, soil moisture (mv), and rms surface height. The results show that the models frequently tend to over-estimate the radar response. The errors indicate that the models tested are dependent on the rms surface height, the soil moisture, and/or the radar incidence.