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Orbital images digital number conversion to surface BRF values



TM/Landsat 5 images from four different dates have been converted to surface Bidirectional Reflectance Factors (BRF surface) through two alternatives. The first one has included the 6S atmospheric correction code and the second one has been based on the radiometric normalization of the TM/Landsat 5 images. Radiometric data from a pasture during the Landsat 5 flight over the study area (one specific date) were compared to the BRF surface determined from the two conversion alternatives. Results have indicated that the spectral characterizations of different targets, independent from the conversion alternative, would be consistent, mainly for targets no so dark as water, for instance. The spectral characterization carried out by BRF surface values calculated by the 6S code presented higher consistency. The statistical comparison between the BRF surface from the field and those determined by the two alternatives has indicated higher similarity between BRF surface from the pasture and those originated from the 6S code application.