Comparative Analysis of Potentials of ASTER Thermal Infrared Band Derived Emissivity Composite, Radiance Composite and Emissivity-Temperature Composite in Geological Mapping of Proterozoic Rocks in Parts of Banswara, Rajasthan

In this study, we have compared the potential utility of relative emissivity bands derived from Level 1B (at sensor georectified radiance) and Level 2 (multiband emissivity product provided by ASTER service provider) data products of Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) sensor for delineating different geological units of volcano-sedimentary provinces in parts Banswara, Rajasthan. Reference channel method was used for deriving emissivity from Level 1B data whereas temperature emissivity separation algorithm was used to derive Level 2 emissivity data products. In the false colour composite image of emissivity bands of two different data products, quartzite was enhanced but other rocks were not discernible. On the other hand, other rocks of the study area were detectable (basalt, gneiss, dolomitic marble) in Level 1B radiance data. In radiance image, variations in surface temperature and emissivity were recorded and this was helpful for delineating different rocks. Surface temperature is sensitive to land cover, moisture and it helped in detecting rocks like dolomite which was covered with moisture rich soil and vegetation. Similarly, emissivity-temperature composite was also proved useful in delineating basalt, quartzite (chloritic), dolomite/dolomitic marble and associated gneiss/migmatites as it brought out the contrast of composition and the differences in the thermophysical parameters resulted temperature variation. An image composite prepared using emissivity band 13, ratio band derived using emissivity band 12 and band 11 and radiant temperature band also could delineate all the major rock types. Further, scatter plots of emissivity bands and temperature used for clustering of different rock units could delineate these rocks from each other. Therefore, conjugate composite images of emissivity and radiant temperature was suitable in delineating all the rocks than the emissivity composite images of different types.