| Tibet is located in the southwest border of the motherland,is the key of the western development,large-scale economic development will inevitably lead to geological disasters threat,also need to draw high attention,to correctly deal with the development of economy and the protection of geological environment,the relationship between the geological disaster prevention,reduce economic losses and casualties,ensure the development of China’s Tibet career smoothly.In this context,this project selects the most typical glacial mudslide disaster in Tibet as the research object for specific research.The study area,Tianmogou,is located in the Yigong Zangbo-Palong Zangbo Deep Valley Fault Zone along National Highway 318,which is a deep cut river valley of The Jianmupuqu,a small tributary of the Palong Zangbo.The main ditch is about 4 km long,and the average ditch bed ratio drops by 244%.Its steep terrain and meltwater provide good water conditions for the formation of mudslides,while the large accumulation of loose moraine in the valley provides the source basis for the formation of mudslides.Tianmogou Glacier is located on the upper edge of the peak of Tianmogou,with an average slope of more than 60°,high in the south and low in the north,and the overall appearance is butterfly-shaped.The glacier has been melting for nearly a decade,and its area is decreasing.In order to better carry out systematic research on Thermogou Glacier in order to explore the deep causes of the eruption of the Tianmogou mudslide,this paper takes the extraction and identification method of the Tianmogou Glacier as the entry point,and uses the data of Gaofen No.2 satellite as the basis for boundary extraction of the Tianmogou Glacier by six methods.This includes four traditional methods: visual interpretation,ratio threshold method,snow cover index method,and supervised classification method,as well as two new methods: matlab edge extraction method assisted by middle streamline and glacier extraction method based on SAR data.The Mid-streamline assisted Matlab edge extraction method is the innovation point of this research,among the many operators,the Cany operator with the highest degree of completion and the most comprehensive extraction idea is selected as the basic operator of the Tianmogou glacier extraction,and the final image is relatively clear to outline the basic outline of the Tianmogou glacier,but in the part where the glacier is connected with the snow on the southern edge of the glacier,there is no effective distinction between glacier and snow.To this end,an auxiliary experiment of the middle streamline of the glacier was added,and the middle streamline of the surface of the Tianmogou glacier was extracted on the basis of DEM data through hydrological analysis,and the extraction result of the Cany operator was assisted in determining the extraction result of the Cany operator according to the length of the mesoliflow line.Due to the superiority of SAR data in glacier extraction,this study takes the glacier boundary of SAR data extraction as the evaluation scale,and evaluates the accuracy of the other five extraction methods from the two dimensions of area and morphology.Experimental results show that although the visual interpretation method looks clumsy and earthy,it is one of the best methods for extracting accuracy.As an innovative point of this paper,the MATLAB edge extraction method assisted by the middle streamline is used in the edge extraction algorithm commonly used in the industrial field on the Tianmogou glacier,supplemented by the middle streamline of the glacier to improve the accuracy,and the final extraction accuracy reaches 81.384%,second only to the visual interpretation method,which provides a little new idea for the extraction method of the glacier. |
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