A model of desertification process in a semi-arid environment employing multi-spectral images

A model of desertification in semi-arid environment employing satellite multi-spectral images is presented. The variables proposed to characterize desertification are: texture of terrain, vegetation index for semi-arid terrain, and albedo of terrain. The texture is derived from a divergence operator applied upon the vector field formed by the first three principal components of the image. The vegetation index selected is the TSAVI, suitable for semi-arid environment where vegetation is scarce. The albedo is calculated from the first principal component obtained from the bands of the multi-spectral image. These three variables are input into a clustering algorithm resulting in six desertification grades. These grades are ordered from no-desertification to severe desertification. Details are provided for the computer calculation of the desertification variables, and the parameters employed in the clustering algorithm. A multi-spectral Landsat TM image is selected for this research. A thematic map of desertification is then generated with the support of ancillary data related to the study area.