Digital mapping of limonitic rocks by using Landsat MSS radio data

Color-ratio composite images of Landsat MSS (multi-spectral scanner) bands have been used by other workers to map the distribution of limonitic rocks in semi-arid and arid areas as possible indicators of hydrothermal alteration (Rowan et al, 1974). The images are particularly useful for broad overviews, but detailed analysis at large scales requires both numerical analysis of the ratio values to distinguish consistently among categories of limonitic rocks and a precise transfer of the data to large-scale base maps. Both requirements can be met by digital classification followed by a precise geometric registration of the classified data.