A BACKSCATTER MODEL FOR WHEAT CANOPIES. COMPARISON WITH C-BAND MULTIPARAMETER SCATTEROMETER MEASUREMENTS

摘要

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, RADARSAT, and the forthcoming ENVISAT. In a first step, ERS data and scatterometer data over the growth season at two test sites are compared with results of a first order coherent modelling. For fully-developed wheat canopies, however, this type of modelling fails to correctly estimate the attenuation of the incident wave within the canopy, resulting in a predicted backscatter ing coefficient one order of magnitude lower than that observed by the SAR system. The main reason for these observed discrepancies between theory and observation, is identified to be the sparse medium assumption in the original model, an assumption which does not apply to fully-grown wheat canopies. Accordingly, we propose higher order modelling based on numerical solution of multiple scattering Foldy-Lax equation. The new modelling improves the backscatter estimate for the both test site.