Correction of topographic effects affecting forest stands by modelling consequences of variations in roof canopy structure on radiometry for high resolution satellite images

To correct SPOT images for changes in radiometry with topography classical approaches, requiring the use of bi-directional reflectance functions, revealed unsuited when applied to a forested area located in south-western France. Actually variations of canopy top structure with topography, a factor liable to explain a part of radiometric variations, is not taken into account by the models presented in literature. An empirical model, based on changes in roof structure, was then proposed. Expression of digital counts according to slope and aspect was estimated for three stand types and a general formulation could be set up. The images were then corrected according to a topographic position of reference. As expected, a reduction of radiometric heterogeneity was noticed