Bidirectional Reflectances of Three Soil Surfaces and Their Characterization through Model Inversion

Abstract

Spectral bidirectional reflectances were measured over three natural soil sites using a specially designed radiometer called the PARABOLA. TWo of the sites were bare soils and the third had a sparse cover of desert scrub. The reflectances were strongly non­ Lambertian for all three surfaces but with markedly different patterns. The measured data were fitted with a quasi-physical reflectance model in which the surface back­ scattering and forwardscattering are separately formulated. A soil reflectance characterization was obtained by assessing the contributions of the forward, -backward and Lambertian components. This three-parameter characterization produced a satisfactory fit to the measured reflectances, and appears promising to provide a basis for soils categorization.