Seasonal Change Investigation of Water Area in Lake Sakata Based on POLSAR Image Analysis

This paper examines seasonal change of the water area in Lake Sakata by using Polarimetric Synthetic Aperture Radar (POLSAR) image analysis. Statistical POLSAR image analysis is carried out for both Xand L-band data, based on a threecomponent scattering power decomposition method, where the decomposed components are surface scattering, doublebounce scattering and volume scattering components. From the results of the image analysis for the L-band POLSAR data acquired by Pi-SAR system, it is found that strong doublebounce scattering can be observed at the vicinity of the boundary region between water area and the surrounding emerged-plants area in early and middle summer seasons. To verify the generating mechanism of the double-bounce scattering, the Finite-Difference Time-Domain (FDTD) polarimetric scattering analysis is also executed for a simplified boundary model, which simulates the local boundary region around the lake and consists of lots of vertical thin dielectric pillars on a perfect electric conductor (PEC) plate or on a PEC and dielectric hybrid plate. Taking into account the polarimetric feature of the double-bounce scattering obtained by both the FDTD and POLSAR image analyses, one can distinguish the water area form the bush of the emerged-plants around the lake, even when the water area are concealed by emergedplants and/or floating-leaved plants. Consequently, it is found that by using the proposed approach, one can estimate the water area seasonal change for the lake and the surrounding wetland.