Coherent and incoherent scattering from tilled soil surfaces

Abstract

A recent experimental study by Wegmuller et al. has reported on directional backscattering patterns in the Synthetic Aperture Radar (SAR) response of bare or sparsely vegetated agricultural soils that require a better understanding of scattering from tilled soils. Shin and Kong modeled the latter as quasi-periodic rough surfaces and showed that the total backscatter consists of three terms, one due to the coherent field and the other two arising from the incoherent scattered field. However, all the simulations reported by Shin and Kong are only concerned with one of the terms contributing to the incoherent scattering and could not predict highly directional backscattering patterns. In this context, the objective of this work is: (1) to extend the Shin–Kong model in order to compute in a finite form all the coherent and incoherent terms; (2) to describe the case of quasi-periodic rough surfaces having quasi-parallel row directions. Results indicate that the new model can predict very narrow (i.e. a few tenths of a degree angular aperture) backscatter peaks when the wave incidence plane is quasi-orthogonal to the row tillage direction. More generally, the paper's results point to the importance of anisotropic tillage patterns in modulating the radar backscatter in the entire azimuthal plane.

Acknowledgements

The research in this paper was funded through European Space Agency Grant 21659/08/NL/lvH. The author wishes to thank Evert Attema, Nicolas Floury and Urs Wegmuller for valuable discussions that helped to improve the paper.