A method for selecting mountaintop points based on DEM

Abstract

The present invention discloses a method for selecting mountaintop points based on DEM, including: 1. Using the neighborhood analysis method to extract potential mountaintop points from the DEM, adding elevation values to the potential mountaintop points, and sorting them from large to small according to the elevation values; 2. Generating contour lines from the DEM; 3. According to the generated contour lines, using the iterative method to generate a contour surface from each closed contour line and append it to the contour surface; 4. According to the spatial relationship between the potential mountaintop points and the contour surface, using the iterative method to select the potential mountaintop points according to the set elevation difference threshold to obtain the selected mountaintop points that meet the requirements. The mountaintop points selected by the present invention can meet the requirements of the elevation difference threshold, without pseudo-mountaintop points and missed mountaintop points, and the method is simple to operate and easy to implement.

Description

Technical Field

[0001] The present invention belongs to the field of application of geographic information technology, and particularly relates to a method for selecting mountaintop points based on DEM. Background Art

[0002] Mountaintop points are the maximum points of elevation in a local area and are the most important topographic feature points. In geomorphology, a mountain is defined as a highland with an altitude of more than 500 meters, a relative relief greater than 200 meters, and a relatively steep slope. In some mountain surveys, different relative height differences are required as the basis for dividing county-level, township-level, and village-level mountains. How to automatically and quickly select the required mountaintop points from DEM according to the relative height difference of the mountains has important research significance.

[0003] There are various methods for extracting mountaintop points. Among them, the neighborhood analysis method has higher efficiency. The number of extracted mountaintop points is related to the size of the neighborhood setting radius. If the neighborhood setting radius is too small, too many pseudo mountaintop points will be generated. If the neighborhood setting radius is too large, mountaintop points will be missed. To overcome this shortcoming, Chen Panpan et al. in the literature "Chen Panpan, Zhang Youshun, Wang Chun, etc. Fast Extraction Technology of Mountaintop Points Based on DEM [J]. Modern Surveying and Mapping, 2006, 29(2): 11-13" used the height difference threshold as the contour interval and quickly extracted mountaintop points from DEM through the functions of neighborhood analysis and overlay analysis. Luo Mingliang et al. in the literature "Luo Mingliang, Tang Guonan. Extraction of Mountaintop Points for Geomorphic Cognition and Spatial Subdivision [J]. Science of Surveying and Mapping, 2010, 35(5): 126-127, 253" proposed a fast extraction method for mountaintop points based on spatial subdivision. Gu Liuwan et al. in the literature "Gu Liuwan, Wang Chun, Liu Minshi, etc. Research on a High-Precision Extraction Model of Mountaintop Points Based on DEM [J]. Engineering of Surveying and Mapping, 2013, 22(5): 51-53" constructed a new mountaintop point extraction model based on the successive descent of the reference plane with the relative height difference as the basis. Liu Hongjian et al. in the literature "Liu Hongjian, Liu Jianzhong, Cai Zhongxiang, etc. A Method for Extracting Mountaintop Points Based on Watershed Subdivision [J]. Journal of Surveying and Mapping Science and Technology, 2014(2): 119-122" established a watershed subdivision model and discussed the influence of the height difference threshold on the model accuracy. Kong Yueping et al. in the literature "Kong Yueping, Qi Yanjun, Jiang Jing, etc. A Method for Extracting Mountaintop Points by Topological Analysis of Mountain Control Areas [J]. Journal of Surveying and Mapping Science and Technology, 2018, 35(1): 77-81" established a closed contour tree mountaintop control area analysis model and formed a method for extracting mountaintop points with the height difference threshold of the mountain control area as the constraint condition. The invention patent CN106033611A discloses "A Method for Extracting Mountaintop Points in DEM Data", and the method obtains the primary selection area of mountaintop points from the contour tree and eliminates pseudo mountaintop points according to the height difference threshold.

[0004] In summary, there are many methods for extracting mountaintop points, but they all have certain defects to varying degrees. Some algorithms are very complex, and some have the phenomena of missing extraction of mountaintop points and over-extracting pseudo-mountaintop points. Summary of the Invention

[0005] Object of the Invention: Aiming at the deficiencies existing in the prior art, the present invention provides a method for selecting mountaintop points based on DEM. The mountaintop points selected by the traversal method can meet the requirements of the elevation difference threshold, and there will be no missing extraction of mountaintop points and over-extracting pseudo-mountaintop points. The method is simple to operate and easy to implement.

[0006] . Technical Solution: The method for selecting mountaintop points based on DEM described in the present invention includes the following steps:

[0007] Step 1, extract potential mountaintop points from the DEM by using the neighborhood analysis method, add elevation values to the potential mountaintop points, and sort them from large to small according to the elevation values;

[0008] Step 2, generate contour lines from the DEM;

[0009] Step 3, according to the generated contour lines, use the iterative method to generate a contour surface from each closed contour line and append it to the contour surface;

[0010] Step 4, according to the spatial relationship between the potential mountaintop points and the contour surface, use the iterative method to select the potential mountaintop points according to the set elevation difference threshold to obtain the selected mountaintop points that meet the requirements.

[0011] In the fourth step, the method for selecting potential mountaintop points by using the iterative method specifically includes:

[0012] The first step, use the potential mountaintop points as the target elements for iterative element selection;

[0013] The second step, use the iterated potential mountaintop points as the target elements and the contour surface as the connection elements for spatial connection to obtain the number of contour surfaces connected by the potential mountaintop points;

[0014] The third step, compare the number of contour surfaces connected by the potential mountaintop points with the number of contour surfaces corresponding to the elevation difference threshold, and screen out the potential mountaintop points that meet the requirements of the elevation difference threshold;

[0015] The fourth step, append the screened potential mountaintop points to the selected mountaintop points;

[0016] The fifth step, according to the screened potential mountaintop points, select the contour surfaces that intersect with them by position, and then delete the selected contour surfaces;

[0017] The sixth step, iteratively execute the first step to the fifth step until all potential mountaintop points are selected, and the selected results are stored in the selected mountaintop points.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] First, the present invention uses the neighborhood comparison method to extract potential mountaintops. By setting a relatively small neighborhood radius, a sufficient number of potential mountaintops can be obtained, avoiding the omission of mountaintops;

[0020] Second, by traversing all potential mountaintops and screening them according to the set elevation difference threshold, all pseudo mountaintops are removed;

[0021] Third, the relative height of a mountaintop can be understood as the vertical height from the mountaintop to the saddle point or the foot of the mountain. When determining whether the highest mountaintop meets the requirements, the relative height of the highest mountaintop can be understood as the vertical height from the mountaintop to the foot of the mountain, which can be calculated based on the number of contour planes occupied by the highest mountaintop and the contour interval. When determining whether the second-highest mountaintop meets the requirements, the relative height of the second-highest mountaintop can be understood as the vertical height from the second-highest mountaintop to its saddle point. After deleting all the contour planes occupied by the highest mountaintop from the contour planes, this relative height can also be calculated based on the number of contour planes occupied by the second-highest mountaintop and the contour interval. Iterating this judgment process to complete the selection of all potential mountaintops, the physical meaning of the mountaintop selection method is clear and the algorithm is concise;

[0022] Fourth, the present invention uses the model constructed by ArcMap to complete the generation of contour planes and the selection of mountaintops, with high execution efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flowchart of the method of the present invention;

[0024] Figure 2 is a contour plane generation model diagram in the embodiment;

[0025] Figure 3 is a mountaintop selection model diagram in the embodiment. MODE OF IMPLEMENTATION

[0026] The present invention will be further described below in conjunction with the drawings and embodiments. Embodiment

[0027] Taking the DEM of Mianchi County with a grid accuracy of 30 meters as an example, as Figure 1 shown, the specific implementation method of the present invention is as follows:

[0028] Step 1: Use ArcMap software to extract potential mountaintops from the DEM of Mianchi County by using the neighborhood analysis method. Set the neighborhood radius to 5 pixels, and 1550 potential mountaintops are extracted. Then, based on the DEM of Mianchi County, add elevation values to the potential mountaintops and sort them in descending order of elevation value;

[0029] Step 2: Use the ArcMap contour tool to generate contours from the Mianchi County DEM, set the contour interval to 1 meter, and the starting contour to 400 meters;

[0030] Step 3: Based on the generated contours, use the contour surface generation model built by ArcMap to implement the process of generating a contour surface from the contours. The model is as Figure 2 shown;

[0031] Step 4: Based on the potential mountaintop points and the contour surface, according to the set elevation difference threshold of 100 meters, use the mountaintop point selection model built by ArcMap to select the potential mountaintop points, and obtain the selected mountaintop points that meet the requirements. The model is as Figure 3 shown. The mountaintop point selection model specifically includes:

[0032] The first step: Use the potential mountaintop points as the target elements for iterative element selection;

[0033] The second step: Use the iterated potential mountaintop points as the target elements and the contour surface as the connecting element for spatial connection to obtain the number of contour surfaces connected to the potential mountaintop points;

[0034] The third step: Compare the number of contour surfaces connected to the potential mountaintop points with the number of contour surfaces corresponding to the elevation difference threshold. The expression is Join_Count >= 100, and filter out the potential mountaintop points that meet the elevation difference threshold requirements;

[0035] The fourth step: Append the filtered potential mountaintop points to the selected mountaintop points;

[0036] The fifth step: According to the filtered potential mountaintop points, select the intersecting contour surfaces by position, and then delete the selected contour surfaces;

[0037] The sixth step: Iteratively execute the first step to the fifth step until all potential mountaintop points are selected. The selected results are stored in the selected mountaintop points, and 14 selected mountaintop points are obtained.

[0038] The above-disclosed is only a preferred embodiment of the present invention, and it cannot be used to limit the scope of the rights of the present invention. Therefore, equivalent changes made according to the claims of the present invention still fall within the scope covered by the present invention.

Claims

1. A method for selecting mountaintop points based on DEM, characterized in that, It includes the following steps: Step 1: Use the neighborhood analysis method to extract potential mountaintop points from the DEM, add elevation values to the potential mountaintop points, and sort them in descending order of elevation values; Step 2: Generate contour lines from the DEM; Step 3: According to the generated contour lines, use the iterative method to generate a contour surface from each closed contour line and append it to the contour surfaces; Step 4: According to the spatial relationship between the potential mountaintop points and the contour surfaces, use the iterative method to select the potential mountaintop points according to the set elevation difference threshold to obtain the selected mountaintop points that meet the requirements. Step 4 specifically includes: The first step: Use the potential mountaintop points as the target elements for iterative element selection; The second step: Use the iterated potential mountaintop points as the target elements and the contour surfaces as the connecting elements for spatial connection to obtain the number of contour surfaces connected to the potential mountaintop points; The third step: Compare the number of contour surfaces connected to the potential mountaintop points with the number of contour surfaces corresponding to the elevation difference threshold, and screen out the potential mountaintop points that meet the elevation difference threshold requirements; The fourth step: Append the screened potential mountaintop points to the selected mountaintop points; The fifth step: According to the screened potential mountaintop points, select the intersecting contour surfaces by position, and then delete the selected contour surfaces; The sixth step: Iteratively execute the first step to the fifth step until all potential mountaintop points are selected, and store the selected results in the selected mountaintop points.

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