Potential of polarimetric Radarsat-2 data in geological mapping – a case study in parts of Dharwar craton, India

Abstract

Polarimetry is a technique for quantitatively estimating the change in polarization in a backscattered electromagnetic signal (in this case a radar signal) with reference to the polarization of the incident signal for estimating the geophysical properties (roughness and dielectric constant) of surface elements. In this study, quadrapole Radarsat-2 data have been utilized for mapping geological elements in Archaean terrain based on their geophysical parameters preserved in the four polarization channels of Radarsat-2 data. The study illustrates how single-look complex polarimetric data can be processed to extract information on lithology, geological structure, and land covers (i.e. soil type, etc.) preferentially developed over each rock type. The study revealed that C-band polarization power images can be used indirectly to delineate lithounits provided each unit has characteristic surface roughness and moisture resulting from the surface cover or exposure pattern developed over each lithounit. Moreover, polarimetric data (inclusive of phase and amplitude) provide complementary information when we compare this information with the information derived from simple polarization composites, derived from the backscattered image of each polarization channel. It is also observed that structural imprints are enhanced in co-polarized (HH, VV) data, whereas the cross-polarized channel (HV, VH) provides information on land cover.

Acknowledgements

We thank Dr V. K. Dadhwal, Director, National Remote Sensing Centre (NRSC), Hyderabad, for his support and encouragement to carry out the research work. We also express our gratitude to G. Behera, Deputy Director, RS&GIS AA, NRSC, for his time to time guidance.