Journal of Geo-information Science >
Extraction and Analysis of Gully Feature Points Based on DEMs
Received date: 2012-11-09
Revised date: 2012-12-24
Online published: 2013-02-25
Gully feature points (GFPs) are crucial for studies on spatial pattern and evolution of gully landforms, and the extraction of the GFPs is the basis of related researches. Previously, scholars have made different methods for GFP detection and most are about runoff nodes. However, these methods are still not integral and have deficiencies in either accuracy or computational efficiency as analyzed in this paper. Thus, based on detailed analysis of DEMs and their derivatives, a series of new algorithms are proposed to improve the performance of GFP detection (including runoff nodes, river heads, confluence origins, potential knickpoints and outlets) by trace of flow direction and neighborhood feature judgment. The methods examine the essential features of GFPs and most thresholds used are invariable in different kinds of landforms. Thus, both the robustness and efficiency of the extraction are improved by the new algorithms. As orders of nodes and knickpoints are important in further analyses, criteria for automatic order classification are also established based on Strahler rules. By using 5m resolution DEMs in the test area in Yijun County, Shaanxi Province, experiments are made to test the methods' ability in both GPF extraction and classification. The results of runoff nodes, river heads, confluence origins and outlets are consistent with manual marks. The detected potential knickpoints also create favorable conditions for researches on gully evolution and guarantee the integrity of GFPs to the maximum extent. Preliminary analyses are made using the GFP results and reflect the variation characteristics of the sum of GFPs as rainfall changes. Finally, the impact of watershed completeness on the accuracy of GFP extraction is discussed in details. It shows that both the loss of stream pixels and confluence accumulations could cause the omission of the points. As the influences brought by data incompleteness can hardly be removed in the extraction process, it is crucial to guarantee that the boundaries of watersheds are within the data extent.
Key words： digital terrain analysis; gully feature point; DEM
XIE Die-Qun, SHU Gong-Chun, SHANG Guo-An, CENG Rui-An . Extraction and Analysis of Gully Feature Points Based on DEMs[J]. Journal of Geo-information Science, 2013 , 15(1) : 61 -67 . DOI: 10.3724/SP.J.1047.2013.00061
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