Advantage of Multi-polarized SAR data for Flood Extent Delineation

摘要

Microwave remote sensing, due to its ability to image even during severe weather conditions is the main source for deriving flood extent for rapid mapping purpose. Most of the studies from the literature reveal that C-band SAR with HH polarization is a better option for delineation of flood extent when compared with VV polarization, which is sensitive to small ripples over flood surface. However, similar problem is observed in HH, at low incidence angles. This study focuses on the extraction of flood inundation using multi-polarized ENV1SAT ASAR data acquired at both low and high incidence angles. The backscatter values for flood surface in both HH & HV polarizations were extracted. It is observed from the ASAR HH polarized data that the backscatter from floodwater is low at high incidence angles and high, in some pockets, at low incidence angles. However, with ASAR HV polarized data, the variation is marginal at both low and high incidence angles. A comparison was made between ASAR HH & HV datasets and Optical (IRS) data. The flood extents derived from both HH & HV are low when compared with the flood extent from IRS data. It is observed that the flood extent from HH is much lesser at low incidence angles (IS1). Further it is also observed that the combined flood extent from both HH & HV are more comparable with optical data, even at different incidence angles.