Combining Multiple Lithological Indices Derived from ASTER Data Using the HSV Color Model

Abstract

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) has 14 spectral bands in the VNIR, SWIR and TIR regions and their spectral bandpasses were designed for geological mapping. This study developed a method of showing the spatial distribution of hydrothermal alteration areas and carbonate rocks by combining the spectral indices derived from the multispectral ASTER data of the different wavelength regions. The HSV color model was employed to combine the spectral indices to generate a single integrated color image. Spectral indices indicating mineral species and amounts were allocated to the Hue (H) and Saturation (S) elements respectively, and topographic information was added to the image as a Value (V) element. It was easy to interpret the meanings of colors on this image, as they were determined in advance. This method was tested using the ASTER data of the Cuprite and Goldfield areas in Nevada (USA) and we confirmed that the HSV color image clearly showed the distribution and zonal structures of the hydrothermal alteration areas. In addition, their spatial distribution was also exhibited by integrating topographic information. This new method allows us to generate a color image that can be easily interpreted for geologic mapping even by a user who is not familiar with remote sensing.