A geological investigation of multispectral remote sensing data for the Mahd Adh Dhahab and Jabal said districts, western Saudi Arabia

Abstract

This thesis examines the effect of spatial resolution on lithological and alteration mapping using remotely sensed multispectral data. The remotely sensed data were obtained by the Thematic Mapper (TM) and Airborne Thematic Mapper (ATM) over two areas in the Arabian Shield. These were the Mahd Adh Dhahab and Jabal Said areas. The ATM data had a nominal spatial resolution of 7.5m, 5m, and 2.5m. In order to compare these data sets it was necessary to correct for, sensor- and scene-related distortions. This was achieved by calibrating each data set and converting them to reflectance units using ground spectra with a similar spectral resolution obtained with the Barringer Hand Held Ratioing Radiometer (HHRR) . The ATM data were also corrected for X-track shading by normalising the brightness of each column to that of the centre column. The result of X-ray and laboratory spectral analysis of samples collected from the study areas, support the presence of characteristic minerals associated with the alteration zones. The corrected data were analysed by a variety of techniques in order to enhance the geological information present in the data. These included false colour compositing, decorrelating stretching and band ratioing. The latter two techniques proved most effective for discrimination and several additional geological units and areas were identified which had not been mapped previously. Results further indicate that the increased spatial resolution of the ATM data did not permit greater discrimination than the TM data. This suggests TM data should prove to be a cost-effective way of mapping and detection of alteration zones in the Arabian Shield.