Validation of a Rough Surface Model Based on Fractional Brownian Geometry with SIRC and ERASME Radar Data over Orgeval

During the 1994 SIRC/XSAR mission, part of the scientific activities were devoted to hydrology applications. To complement the shuttle radar data, the helicopter scatterometer ERASME was used on the Orgeval site. As a result, incidence angles ranging from 25° to 57° are available in the C band. Terrain measurements of soil moisture and roughness were also taken. The objective of this study was to take advantage of this data set to improve the geometrical characterization of local soil structure using a fractional Brownian model in order to simulate radar backscattering over agricultural fields. The experimental soil profiles are proved to be locally fractal over a spatial range of a few centimeters (clod structure). The relation between the shape of the correlation function and the fractal dimension is brought to light. A new empirical correlation function is used to adjust the experimental one. It leads to an improvement in the analytic backscattering model Integral Equation Model. Soil profiles, generated with combination between fractional Brownian local structure and global structure with respect to the surface root mean square (rms height) and the correlation length, are used in Moment Method backscattering simulations, which provide results in excellent agreement with radar data.