Use of synthetic aperture radar polarimetry to characterize wetland targets of Keoladeo National Park, Bharatpur, India

Abstract

Timely and accurate information about various habitats of a wetland ecosystem is necessary for the assessment, monitoring and management of a wetland. In this article, the state-of-the-art Polarimetric Synthetic Aperture Radar (PolSAR) data have been analysed to characterize various components of a wetland ecosystem. SAR polarimetry has received negligible attention in India, mostly owing to lack of data over the Indian sub-continent. With a recent DLR-ESAR (Experimental- SAR) flight over India, it was possible to conduct a detailed, planned experiment to explore the potentials of SAR polarimetry. This study has been carried out using fully polarimetric, multi-frequency DLR-ESAR data over parts of a world heritage and Ramsar site, the Keoladeo National Park, Bharatpur, India. Scattering models based on physical principles have been applied to characterize the wetland targets like open-water habitat, various types of aquatic vegetation with or without standing water, along with various species of forested areas. Entropy, alpha angle and anisotropy have been derived by performing eigen vector-based target decomposition on L- and P-bands fully polarimetric SAR data, enabling us to understand the differences in wetland targets in terms of their scattering behaviour at the L- and P-bands. A significant outcome of this study is that it explores and demonstrates the potential of the state-of-the-art technique of PolSAR for characterizing scattering behaviour of various components of a wetland ecosystem, which is a less explored application of SAR, particularly in the Asian countries.