Evaluation of a rough soil surface description with ASAR-ENVISAT radar data

The input roughness parameters for electromagnetic backscattering modelling need to be accurate to estimate radar measurements correctly over bare soils, particularly in agricultural environments. This paper proposes to evaluate the roughness description in terms of several characterisations through a correlation function using a numerical backscattering model. The experimental database used in this study is based on ASAR-ENVISAT experimental campaigns in the Beauce region (France). Two presentations of the surface height correlation function are proposed in this study. The first one, referred to as the "alpha function" fits the experimental correlation functions up to the correlation length, while the second one, the "(a,b) function", fits the correlation function for scales corresponding to positive values. A relationship is proposed between the rms height of soil surface and the shape of the correlation function. Using the a function, comparisons between radar measurements for high incidence angles and simulations based on the numerical backscattering model (moment method) show a good agreement for soil surfaces with an rms height smaller than 2 cm with medium and high soil moisture. (c) 2004 Elsevier Inc. All rights reserved.