Usage of indices for extraction of built-up areas and vegetation features from Landsat TM image: a case of Dar es salaam and Kisarawe peri-urban areas, Tanzania

Abstract

This paper address the use of Indices Co mbination with Supervision Classification methods to extract urban built-up areas, vegetation and water features fro m Landsat Thematic Mapper (TM7) imagery covering Dar es Salaam and Kisarawe peri-urban areas. The study uses three indices; Normalized Difference Bu ilt-up Index (NDBI), Modified Normalized Difference Water Index (MNDWI), and Soil Adjusted Vegetation Index (SA VI) to reduce the seven bands Landsat TM7 image into three thematic-oriented bands. Data correlation, spectral confusion and redundancy between original mu ltispectral bands were significantly reduced upon application of the techniques. As a result, the spectral signatures of the three urban land-use classes are mo re distinguishable in the new co mposite image than in the original seven-band image since the spectral clusters of the classes are well separated. Through a supervised classification on the newly formed image, the urban built-up areas, vegetation and water features were finally extracted effect ively; with the accuracy of 82.05 percent attained. The results show that the technique is effective and reliable and can be considered for use in other areas with similar characteristics