The utility of Landsat images in delineating volcanic cones in Harrat Kishb, Kingdom of Saudi Arabia

Landsat images have been analysed visually to assess their utility in delineating cones/ventsin one of the Cenozoic volcanic fields, Harrat Kishb, in the western region of Saudi Arabia. Volcanic cones identified from six sets of Landsat data (one Return Boom Vidicon, two Thematic Mapper and three Multispectral Scanner images) were checked in the field and then compared with those extracted from aerial photographs as shown on the existing geological maps. The result shows that the accuracy of the visual identification varies greatly from 51 per cent for the Multispectral Scanner to 93 per cent for the Thematic Mapper. A new measure of mapping accuracy which incorporates both the commission and omission errors was computed to range between 63 and 88 per cent, respectively, for these two images. To demonstrate further the usefulness of the Landsat images in geological investigations on volcano-tectonics, geometrical properties associated with those delineated cones were also estimated. The cone density is 2·66 cones 100km −2 with an average (geometric mean) spacing of 2·29km. The alignment of cones identified on the Thematic Mapper image covering the study area has a mean orientation of N 8°W.