Extraction of typhoon-damaged forests from multi-temporal high-resolution polarimetric SAR images

The purpose of this study is to extract the forests destroyed by typhoons and to quantitatively estimate the damage levels by using high-resolution polarimetric synthetic aperture radar (SAR) data. The study area is located in Tomakomai, Hokkaido, Japan. Two sets of data were acquired before and after the typhoon by the L-band airborne Pi-SAR (Polarimetric-interferometric SAR) with 3m × 3m resolution (4-look in azimuth direction). It was found that the values of RCS (Radar Cross Section) averaged over the whole image after the typhoon damage changed by -0.47 dB, 0.05 dB, and 0.64 dB at HH-, HV-, and VV-polarization respectively in comparison with those before the damage. To fully utilize the data, a scattering model of the linear combination of the cross- and co-polarization RCS changes was developed to estimate the damage levels. Similar analytical approaches were also applied using the three-component decomposition analysis. The changes in RCS of double-, volume- and surfacescattering mechanisms after the damage were respectively 27.5 dB, -0.20 dB and -20.3 dB. Finally, by comparing the results with the ground survey data, the accuracies of 64.1% and 77.7% were obtained for the RCS and decomposition analyses respectively.