Abstract
Hillshaded digital elevation models are a well-known information layer used to determine the geomorphological properties of landslides. However, their use is limited because the results are dependent on a particular sun azimuth and elevation. Approaches proposed to overcome this bias include positive openness, sky-view factor, red relief image maps, and prismatic openness. We propose an upgrade to all these methods, a method named Visualization for Archaeological Topography (VAT). The method is based on a fusion of four information layers into a single image (hillshaded terrain, slope, positive openness, and sky-view factor). VAT can be used to enhance visibility of features of varied scale, height, orientation, and form that sit on terrain ranging from extremely flat to very steep. Besides this, the merits of VAT are that the results are comparable across diverse geographical areas. We have successfully tested the method for landslide recognition and analysis in five different areas in the Vipava Valley (SW Slovenia). Geomorphology of the area is very diverse and holds various types of mass movements. In contrast to classical hillshaded digital elevation models (DEMs), the geomorphological features of landslides obtained by the VAT method are very clearly seen in all studied mass movements.
Highlights
A hillshaded digital elevation model (DEM) derived from airborne laser scanning is one of the basic modern tools for recognizing landslides, especially in vegetated areas or non-accessible areas
We propose an upgrade to these methods, using Visualization for Archaeological Topography (VAT), which has been used successfully in this paper for landslide recognition and analysis
The studied area is located in the lower part of the landslides, in the vicinity of the lower concrete wall
Summary
A hillshaded digital elevation model (DEM) derived from airborne laser scanning is one of the basic modern tools for recognizing landslides, especially in vegetated areas or non-accessible areas. Hillshading algorithms are included in most GIS software and are available to anyone. Most of this software has default values for the simulated sun azimuth and elevation, and these are usually set at 315◦ and 45◦, respectively (in ESRI ArcGIS and QGIS). A known problem is that if a ravine, gully, or crest is oriented in the same direction as the illumination azimuth, there will be no shadow and, no morphological features visible on the hillshaded DEM
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