Detection and interpretation of landslides using satellite images

The severity of the landslide hazard in Hong Kong has resulted in the establishment of a comprehensive landslide database, the Natural Terrain Landslide Inventory (NTLI). It is derived mainly from the interpretation of medium to large-scale aerial photographs, and describes the location of all landslides. In view of the labour-intensive nature of air photo interpretation, as well as the lack of regular air photo cover in many countries, satellite images were examined for their ability to monitor landslides at a similarly detailed level, using the NTLI database as a reference. Using automated change detection with SPOT XS® images it was possible to identify 70% of landslides, the main omissions being due to those less than 10 m in width, and many of those identified were of sub-pixel width. The study also examined different techniques of image fusion for the enhancement of IKONOS images, and demonstrated that landslides on fused images are of similar detail to those on air photos. A methodology for regional scale monitoring is proposed which combines the efficiency of automated techniques for large area monitoring using SPOT® with the qualitative detail obtained from Pan-sharpened IKONOS images.