Abstract

BOLANOS-GONZALEZ, Martín A. et al. Modelation of the sun-sensor geometry effects in the vegetation reflectance. Agrociencia [online]. 2007, vol.41, n.5, pp.527-537. ISSN 2521-9766.

Surface reflectance is not only a function of the spectral properties of incident radiation and surface anisotropy, but also of the direction from which the surface is illuminated and seen; that is, it depends on the illumination-vision geometry (sun-sensor in the specific cases of satellite images) with which it is acquired. The dependence of surface reflectance on sunsensor geometry is described by the Bidirectional Reflectance Distribution Function (BRDF). For that reason, it is necessary to minimize these effects as the first step in calculating vegetation indexes or any other estimation based on surface reflectance that intends to link bio-physical characteristics of crops or natural vegetation. In this study, a model that estimates reflectance at nadir of the red (R) and near infrared (IRC) bands with a single datum of reflectance obtained with any combination of sun-sensor geometry is developed and evaluated. The proposed model was validated with experimental data taken in a natural grassland, with which adequate results (R2=0.967) were obtained.

Keywords : BRDF; sun-sensor geometry; reflectance.