Journal of the Japan Society of Erosion Control Engineering, Vol.65,No.4, 2012

Applicability of methods for detecting landslides by using synthetic aperture radar of ALOS(Daichi)

Shin-ichiro HAYASHI, Masaki MIZUNO, Nobutomo OSANAI, Masato NISHI, Yoshikazu SHIMIZU,
Kazuo NAKAGAWA and Sadakazu MATSUMOTO


Abstract

Synthetic aperture radariSARjinstalled in an artificial satellite can observe ground conditions even at night and in bad weather conditions when disaster surveying by helicopters is difficult. Using SAR in the Japanese artificial satellite ALOSiDaichijto detect landslides applies correlation coefficient difference analysis and NDPIiNormalized Difference Polarization Indexjdifference analysis to the area damaged by the Iwate]Miyagi inland earthquakeiIwate]Miyagijand sediment]related disasters caused by heavy rain in Hofu city, Yamaguchi Pref. iYamaguchi disasterj. The results are summarized as follows. The analysis methods have almost identical landslide detection capability. Both analysis methods can detect landslides with size over 10,000m2 with above 60“ accuracy, and over 40,000m2 with above 80“ accuracy. There may be a minimum detectable landslide size. The size of the Iwate]Miyagi is 900m2 and Yamaguchi disaster is 2,500m2. In all analyzed views of SAR satellite images, detection accuracy was better in the Iwate]Miyagi case than the Yamaguchi disaster case. Landslide size is a more effective determinant of capability to detect landslides than slope gradient. The smaller a landslide's size, the more effective slope direction is as a determinant of landslide detection difficulty.

Key wordsFsynthetic aperture radariSARj, artificial satellite, ALOS, landslide


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