| Summary: | 碩士 === 國立中興大學 === 土木工程學系所 === 107 === The Digital Elevation Model (DEM) is a numerical topographical information that records changes in terrain fluctuations. It not only implies information on ridgelines and valleys, but is also used in developing method for automatically extracting topographic features. Ridge line and valley line are topographic structural lines formed under the geological action of nature. They have the characteristics of water separation and water combination, and play an extremely important role in hydrology and terrain analysis.
This study compares the results in extracting ridge lines and valley lines from DEM by applying an image processing method and ArcGIS 10.2 in two regions with different elevation undulations for their accuracy and differences in different elevation relief areas.
The results of the study show that the image processing method is superior to ArcGIS in the extraction of the ridgeline, especially in the area where the terrain is undulating or gentle, and ArcGIS is superior to the image processing method in extracting the valley line. In addition, it is found that when the local land form is affected by human development factors (such as railways or highways), it is easy to form a valley line misjudgment, which affects the extraction accuracy.
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