ASTER ratio indices for supraglacial terrain mapping

Supraglacial terrain, such as that found in the Himalayas, is typically composed of snow, ice, ice-mixed-debris (IMD) and debris. This letter presents a methodology for systematic discrimination and mapping of these supraglacial cover types using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. The Normalized Difference Snow Index (NDSI) has been used previously for discrimination of snow/ice-bearing zones versus debris. Two new indices, the Normalized Difference Glacier Index (NDGI) and the Normalized Difference Snow Ice Index (NDSII), are presented. The combination of all three indices allows discrimination of snow, ice and IMD in a systematic manner.