Understanding C-band radar backscatter from wheat canopy using a multiple-scattering coherent model

This paper describes a modeling approach to interpret the C-band synthetic aperture radar (SAR) data from wheat canopies as provided by European Remote Sensing (ERS) satellites, RADARSAT, and the forthcoming Environmental Satellite/Advanced Synthetic Aperture Radar (ENVISAT/ASAR) satellite. At a first step, the results of a first-order modeling were compared to ERS data and scatterometer data over the growing season at two different test sites. The prediction by first-order approach was in disagreement with the data from stem extension stage to soft ripening stage. The first-order approach was found to overestimate the attenuation at vertical (V) polarization, resulting in a predicted backscattering coefficient one order of magnitude lower than that observed by the SAR system. To improve the prediction, a multiple-scattering modeling based on numerical solution of multiple-scattering Foldy–Lax equation was used. The multiple-scattering modeling provides better backscatter estimates at vertical–vertical (VV) polarization for both test sites. Then, the model is used to derive the prevailing interactions mechanisms at horizontal–horizontal (HH) and VV polarizations and 23 and 40 of incidence angle. Finally, the retrieval of crop parameters from C-band SAR data is addressed.