OUTLINE Introduction Material and methods Case studies Results Future Works
Introduction Because of the climate changing and extreme rainfall, more and more geologic hazard appearing in recent years. For the purpose of landslides study and sensitive zone planning, we need to use the appropriate mapping unit to create various types of landslide potential evaluation system.
Introduction The classic ways to incorporate relief units into a landscape assessment is to delineate them during field survey or using stereo aerial photographs.
Introduction Mapping unit (Carrara et al., 1995 ) (Guzzeti et al.,1999) (a) Grid cells (b) Slope units (c) Geomorphological, Terrain units
Introduction Main enhancements of automatic methods The reduction of human errors by eliminating manual classification steps The facilitation of comparisons of results derived from different datasets The reduction in processing time This study applied automatic method to generate a suitable slope unit.
Introduction Automatic image interpretation Pixel-based methods are ill-suited to represent a geomorphic process salt & pepper Object-oriented method is a knowledge driven method Pixels Based Objects Based
Material and methods DTMs and digital geomorphologic analysis During the last two decades the availability of DTM data has been continuously growing, data accuracy has improved, and additional algorithms have been developed to derive new attributes from gridded DTMs Derivatives from the DTMs Slope, Aspect, Curvature, Catchment, River…
Material and methods Terrain Analysis （ Wilson and Gallant, 2000 ）
Material and methods Using the “Definiens “ object based image analysis software multi-scale segmentation and object relationship modeling The largest homogeneity within the slope-unit The largest heterogeneity between slope-units ‘build’ topomorphologic objects in the multi-scale segmentation step, delineating areas of relative homogeneity within the spatial layers of topographic variables such as slope, curvature, aspect,catchment, catchment, river..
Scale parameter Decides the segmentation size Color ／ Shape factor Smoothness ／ Compactness
Future works Adjust the weight of each layer and produce a more reasonable slope-unit Adjust and discuss the river threshold value, generate the appropriate size catchment Appling this criteria in other regions for validation, and review the effectiveness Statistics the distribution of gradient, aspect and unit-size, and discussion