Assessment of typhoon-damaged forest by multi-temporal and multi-frequency POLSAR and InSAR datasets

The purpose of this study is to quantitatively assess the forests damaged by typhoons using multi-temporal high-resolution polarimetric synthetic aperture radar (SAR) data. The study area is located in Tomakomai, Hokkaido, Japan, where substantial damage was caused by the typhoon “Songda” (Japanese typhoon number 18) in September 8th, 2004. The forests map showing damaged stands from ground survey is available for comparison. In this study, we used two pairs SAR images acquired by the L-band fully polarimetric and X-band interferometric airborne Pi-SAR (Polarimetric Interferometric SAR) with 3 m × 3 m and 1.5 m × 1.5 m resolution (4-look in azimuth direction), respectively. For L-band datasets, the data were acquired before the typhoon damage in November 7th, 2002 (scene number L6407), and after the damage in November, 3rd, 2004 (scene number L8104), under similar conditions, such as the look direction and incidence angle (difference <;0.5° at the study area). For X-band datasets, data acquired before typhoon is in August 20th, 2003 (scene number X6907), and after the damage in November, 3rd, 2004 (scene number X8104), also under similar conditions, as L-band data. The analyses and the results are summarized as follows.