Abstract
As the basic geomorphologic unit for the occurrence of geological hazards, slope unit is widely used in the prevention and evaluation of landslide-based geological hazards. Its extraction is the primary target and important foundation for the risk assessment of landslide hazards. A new slope unit extraction method based on improved marked watershed is proposed in this paper. Firstly, the DEM image is segmented by marker-based watershed to extract mountain objects. Then the positive and negative terrain of the mountain objects are segmented by watershed to extract ridge lines and valley lines. Finally, these lines are superimposed to extract the slope unit. The experimental results show that slope unit can be extracted by this method. Compared with the traditional GIS methods, horizontal planes and inclined planes can be segmented correctly, and the problem of parallel boundaries caused by filling of depressions can be effectively avoided through this method.
Highlights
Slope unit is the basic geomorphologic unit for the occurrence of geological hazards, which is divided by ridge lines and valley lines
Combined with the positive and negative terrain in GIS, watershed algorithm is used to segment terrain images, i.e. DEM images, to overcome the shortcomings of traditional GIS methods, which are prone to parallel boundaries and cannot effectively distinguish horizontal planes from inclined planes
According to the features of DEM images, marker-based watershed algorithm is used to solve the problem of over-segmentation in this paper, so as to extract the boundaries of mountains and obtain mountain objects, and combined with the idea of the positive and negative terrain in GIS, the positive and negative terrain of mountain objects are segmented to extract ridge lines and valley lines respectively, and these lines are superimposed to obtain slope units
Summary
Slope unit is the basic geomorphologic unit for the occurrence of geological hazards, which is divided by ridge lines and valley lines. The GIS methods mentioned above are widely used, there are still two shortcomings as follows: first of all, these methods are prone to parallel boundaries due to the effect of filling of depressions[9]; besides, these methods cannot effectively distinguish horizontal planes from inclined planes when there are mountain basins or large wide valleys in the terrain[10]. Due to these facts, the slope units extracted by GIS methods often do not conform to the actual topography, making complicated manual revision work a must, which makes the extraction inefficient. Combined with the positive and negative terrain in GIS, watershed algorithm is used to segment terrain images, i.e. DEM images, to overcome the shortcomings of traditional GIS methods, which are prone to parallel boundaries and cannot effectively distinguish horizontal planes from inclined planes
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