The synoptic view and multispectral nature of the satellite imagery help in discrimination and mapping of different lithologic units. Geological mapping is carried out mainly based on visual interpretation of satellite images (Figure 8.1) adopting deductive approach by studying image characteristics and terrain information in conjunction with a prior knowledge of general geological setting of the area. The tone (colour) and landform characteristics combined with relative erodibility, drainage, soil type, land use/ land cover and other contextual information observable on the satellite image are useful in differentiating different rock groups / types.