A second order backscatter model for wheat canopies. Formulation and comparison with data

This paper describes a theoretical study on radar backscatter from a wheat canopy, based on experimental data. The objective is to interpret C-band SAR data provided by ERS and RADARSAT, and the forthcoming ENVISAT. Data from four ERS overpasses during the growth season are interpreted in a first step using 1st order coherent modelling. For fully-developed wheat stands, however, this type of modelling fails to correctly estimate the attenuation of the incident wave within the canopy, resulting in a predicted backscattering coefficient one order of magnitude lower than that observed by SAR system. The main reason for these observed discrepancies between theory and observation is shown to be the assumption of a sparse scatterers in the original model, a condition which does not apply to fully-grown wheat canopies. Accordingly we trace an outline of future modeling work that will be carried out to tackle this problem.