A COMPARATIVE EVALUATION OF RATIO TRANSFORMED AND ENHANCED THEMATIC MAPPER IMAGES IN LANDCOVER CLASSIFICATION OF THE SAHEL REGION OF WEST AFRICA

摘要

A window of 512 X 512 pixels taken from TM image of Tahoua area of Niger Republic, acquired on 3rd September 1989 was corrected for Atmospheric effects. Principal component analysis was used to select bands for further processing. Band ratioing was applied to the selected bands on one hand to generate 4 ratio composite images while spatial filtering (LP-filtering, directional HP-filtering and undirectional HP-filtering) was applied to the selected bands on the other hand to generate a new multispectral image. Training sites were selected from both the ratio composites and the new multispectral image. A supervised classification technique was used to generate 5 landcover classification maps of the study area. A comparative analysis of the classified maps was made to evaluate the performance of each of the images, in discriminating a given class from the others. The aim was to see which of the images so formed will provide a more acceptable result in studying and mapping landcover changes in this region.