n order to obtain reflectance values on the surface, an atmospheric correction was done using the ACORN 4.0 program, based on the radiation transference model MODTRAN 4, which transforms radiance values of ASTER images for surface reflectance values. Data of water vapor were obtained from MODIS sensor data, located at the same Terra satellite corresponding to the same dates of obtainment from these ASTER images (MODIS, 2003).