CN107958485B - Pseudo mountain vertex removing method - Google Patents
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- CN107958485B CN107958485B CN201711294454.4A CN201711294454A CN107958485B CN 107958485 B CN107958485 B CN 107958485B CN 201711294454 A CN201711294454 A CN 201711294454A CN 107958485 B CN107958485 B CN 107958485B
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Abstract
The invention discloses a method for eliminating a pseudo mountain vertex, which comprises the following steps: (1) extracting a mountain vertex from DEM data and storing the mountain vertex in a point set P; (2) constructing an irregular triangular net based on the point set P, screening mountain top points based on the length of the middle edge of the irregular triangular net, and storing the screened result into a point set P'; (3) constructing an irregular triangulation network based on the point set P ', and acquiring a height value set H' of areas covered by each side of the irregular triangulation network; (4) based on the set H ', adopting a height difference threshold value to screen mountain tops, storing the screened result into a point set P', and finishing the elimination of pseudo mountain tops; (5) and writing the point set P' of the pseudo mountain top points after elimination into the mountain top point image layer. The invention has high execution efficiency and good rejection effect.
Description
Technical Field
The invention relates to the field of geographic information technology application, in particular to a method for eliminating false mountain tops by acquiring distance information between mountain tops and height difference information around the mountain tops based on an irregular triangulation network.
Background
The mountain top is one of important topographic factors which form a topographic contour skeleton and influence environmental change, hydrological processes, biological distribution, landform characteristics and the like, and the spatial distribution characteristics of the mountain top are important indexes which are used for describing the spatial change processes by people.
Based on the important role of the mountain vertex in the geological research, various theories and methods for extracting the mountain vertex based on DEM have appeared at present. For example, the method of combining hydrology and window analysis is utilized in Tang national security and the like to effectively extract mountain top points; the trypan is based on a morphological method, fast extraction of mountain vertexes is achieved by means of neighborhood analysis and topology analysis, and influences of DEM resolution and neighborhood analysis window size on the mountain vertex extraction are analyzed.
The mountain apex is geometrically the highest elevation point. Thus in a regular grid DEM, the mountain vertices are the elevation maxima of the local region S, i.e. within a specific neighborhood analysis range, the mountain vertices are higher than the surrounding points. However, the condition of the highest point of the local region cannot be directly used for judging, and the extracted mountain top points still need to conform to geomorphology definition. In the application of the related method, the simple dependence on neighborhood analysis and topology analysis inevitably generates more pseudo mountain vertexes. Therefore, how to quickly and effectively eliminate the pseudo mountain top points becomes one of the problems which are urgently needed to be solved at present.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the problems in the prior art, the invention provides a method for removing the pseudo-mountain top points generated by DEM data.
The technical scheme is as follows: the method for eliminating the top points of the pseudo mountains comprises the following steps:
(1) extracting a mountain vertex from DEM data and storing the mountain vertex in a point set P;
(2) constructing an irregular triangular net based on the point set P, screening mountain top points based on the length of the middle edge of the irregular triangular net, and storing the screened result into a point set P';
(3) constructing an irregular triangulation network based on the point set P', and acquiring a height value set H of areas covered by each side of the irregular triangulation network;
(4) based on the set H, adopting a height difference threshold value to screen mountain tops, storing the screened result into a point set P', and finishing the elimination of pseudo mountain tops;
(5) and writing the point set P' of the pseudo mountain top points after elimination into the mountain top point image layer.
Further, the method for extracting the mountain top point in the step (1) comprises the following steps: and extracting the DEM data by using a neighborhood analysis method in ArcMap.
Further, the step (2) specifically comprises:
(2-1) constructing an irregular triangulation network by using the mountain vertex set P;
(2-2) traversing each edge of the irregular triangulation network, and adding the edge with the length smaller than the edge length threshold value d into the edge set E;
(2-3) for any point P in the set of points PiIn E with piStoring edges with adjacency into set Ei；
(2-4) if set EiIf not, executing the step (2-5); otherwise, executing the step (2-7);
(2-5) from the set EiThe end points of all edges are obtained and stored in the set EPi；
(2-6) traversal of EPiIf EPiIn the absence of elevation less than piAt a point of (1), then p isiDeleting from the point set P;
and (2-7) circularly executing the steps (2-3) to (2-6) until the screening of all the points in the point set P is finished, and storing the screened result into the point set P'.
Further, the step (3) specifically comprises:
(3-1) constructing an irregular triangulation network based on the point set P ', and reading the edge of the irregular triangulation network into an edge set E';
(3-2) reading DEM data, taking E' as a statistical region, and performing partition statistics based on ArcEngine to obtain each edge E in EiMinimum elevation value h ofiAnd are entered in the set H, where H { (e)1,h1),...,(en,hn) N is the number of edges in E'.
Further, the step (4) specifically comprises:
(4-1) for any point P in the set of points Pi', the elevation is marked as height, all tuples corresponding to the edges which have adjacency relation with the height are found out from H, and the tuples are stored into a set H', H { (e)1,h1),...,(em,hm) Wherein m is equal to the point pi' number of edges having an abutting relationship, and m<n；
(4-2) traversing each tuple in the set H', and judging whether a tuple (e) exists or notk,hk) Satisfy height-hk<h, if present, point pi'deleted from the set of points P'; wherein h is a preset threshold value, k belongs to [1, m ∈]；
And (4-3) circularly executing the steps (4-1) to (4-2) until the elevation screening of all the points in the point set P 'is completed, and storing the screened result in the point set P'.
Furthermore, parameters such as the side length threshold, the elevation threshold and the like in the invention can be properly adjusted according to the actual application requirements.
Has the advantages that: compared with the prior art, the invention has the following remarkable advantages: the method can realize effective deletion of the pseudo-mountain vertex through distance constraint and elevation constraint. Compared with the prior art, the method has the advantages of high execution efficiency and good rejection effect.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 shows experimental data in examples;
FIG. 3 shows mountaintop points extracted based on DEM in the embodiment;
FIG. 4 is an example of an irregular triangulation network generated based on mountain vertices;
FIG. 5 is an edge of an irregular triangular mesh having an edge length of less than 200m in an embodiment;
FIG. 6 is a schematic diagram of side length screening in the example;
FIG. 7 is the mountain top points screened based on the side length in the example;
FIG. 8 is a diagram illustrating mountain vertices filtered based on elevation in an embodiment.
Detailed Description
As shown in fig. 1, the method for eliminating the top of the pseudo mountain provided in this embodiment includes the following steps:
(1) and (4) extracting a mountain vertex from the DEM data and adding the mountain vertex into the point set P.
The example selects 1: 500 deg. mountain DEM data (fig. 2), in the form of an Esri Grid format. The extraction method adopts a neighborhood analysis method in ArcMap, and the statistical window size rho is 100. Firstly, opening a 100 × 100 square window for window analysis to extract a maximum value, and obtaining a maximum value grid file; secondly, subtracting the original DEM from the maximum value raster file, extracting all 0 value grids and converting the 0 value grids into vector planes; and finally, extracting the central point of the vector plane to obtain a candidate mountain vertex. The extracted mountain top points are shown in fig. 3.
(2) And constructing an irregular triangular net based on the point set P, screening mountain top points based on the length of the middle edge of the irregular triangular net, and storing the screened result into the point set P'. The method specifically comprises the following steps:
(2-1) constructing an irregular triangulation network by using the mountain vertex set P;
(2-2) traversing each edge of the irregular triangulation network, and adding the edge with the length smaller than the edge length threshold value d into the edge set E; in this embodiment, the side length threshold d is 200, the constructed TIN is shown in fig. 4, and the side set E is shown in fig. 5;
(2-3) for any point P in the set of points PiIn E with piThere is an abutmentStoring edges of relationships into a set Ei(ii) a For example, in the present embodiment, with p1The edges and end points of the adjacent points are shown in FIG. 6;
(2-4) if set EiIf not, executing the step (2-5); otherwise, executing the step (2-7);
(2-5) from the set EiThe end points of all edges are obtained and stored in the set EPi；
(2-6) traversal of EPiIf EPiIn the absence of elevation less than piAt a point of (1), then p isiDeleting from the point set P; for example, in the present embodiment, p1The elevation value of the point is 1281, and the point with the elevation less than 1281 exists, so p1Points are reserved;
and (2-7) circularly executing the steps (2-3) to (2-6) until the screening of all the points in the point set P is finished, and storing the screened result into the point set P'. In this example, the mountain top points screened based on the side length are shown in fig. 7.
(3) Constructing an irregular triangulation network based on the point set P', and acquiring a height value set H of areas covered by each side of the irregular triangulation network; the method specifically comprises the following steps:
(3-1) constructing an irregular triangulation network based on the point set P ', and reading the edge of the irregular triangulation network into an edge set E';
(3-2) reading DEM data, taking E' as a statistical region, and performing partition statistics based on ArcEngine to obtain each edge E in EiMinimum elevation value h ofiAnd are entered in the set H, where H { (e)1,h1),...,(en,hn) N is the number of edges in E'. In this embodiment, the partition statistical result H is shown in table 1.
TABLE 1
(4) Based on the set H, adopting a height difference threshold value to screen mountain tops, storing the screened result into a point set P', and finishing the elimination of pseudo mountain tops; the method specifically comprises the following steps:
(4-1) for any point P in the set of points Pi', the elevation is marked as height, all tuples corresponding to the edges which have adjacency relation with the height are found out from H, and the tuples are stored into a set H', H { (e)1,h1),...,(em,hm) Wherein m is equal to the point pi' number of edges having an abutting relationship, and m<n；
(4-2) traversing each tuple in the set H', and judging whether a tuple (e) exists or notk,hk) Satisfy height-hk<h, if present, point pi'deleted from the set of points P'; where h is a preset threshold, which is set to 50 in this embodiment, k ∈ [1, m ∈ [ ]]；
And (4-3) circularly executing the steps (4-1) to (4-2) until the elevation screening of all the points in the point set P 'is completed, and storing the screened result in the point set P'.
(5) And writing the point set P' of the pseudo mountain top points after elimination into the mountain top point image layer. In this embodiment, the mountain vertex map layer from which the pseudo-mountain vertices are removed is shown in fig. 8.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Claims (4)
1. A pseudo mountain vertex eliminating method is characterized by comprising the following steps:
(1) extracting a mountain vertex from DEM data and storing the mountain vertex in a point set P;
(2) constructing an irregular triangular net based on the point set P, screening mountain top points based on the length of the middle edge of the irregular triangular net, and storing the screened result into a point set P';
(3) constructing an irregular triangulation network based on the point set P', and acquiring a height value set H of areas covered by each side of the irregular triangulation network; the method specifically comprises the following steps:
(3-1) constructing an irregular triangulation network based on the point set P ', and reading the edge of the irregular triangulation network into an edge set E';
(3-2) reading DEM data, taking E' as a statistical region, and performing partition statistics based on ArcEngine to obtain each edge E in EiIs smallest inHeight hiAnd are entered in the set H, where H { (e)1,h1),...,(en,hn) N is the number of edges in E';
(4) based on the set H, adopting a height difference threshold value to screen mountain tops, storing the screened result into a point set P', and finishing the elimination of pseudo mountain tops;
(5) and writing the point set P' of the pseudo mountain top points after elimination into the mountain top point image layer.
2. The pseudo mountain vertex rejection method according to claim 1, wherein: the method for extracting the mountain top point in the step (1) comprises the following steps: and extracting the DEM data by using a neighborhood analysis method in ArcMap.
3. The pseudo mountain vertex rejection method according to claim 1, wherein: the step (2) specifically comprises the following steps:
(2-1) constructing an irregular triangulation network by using the mountain vertex set P;
(2-2) traversing each edge of the irregular triangulation network, and adding the edge with the length smaller than the edge length threshold value d into the edge set E;
(2-3) for any point P in the set of points PiIn E with piStoring edges with adjacency into set Ei；
(2-4) if set EiIf not, executing the step (2-5); otherwise, executing the step (2-7);
(2-5) from the set EiThe end points of all edges are obtained and stored in the set EPi；
(2-6) traversal of EPiIf EPiIn the absence of elevation less than piAt a point of (1), then p isiDeleting from the point set P;
and (2-7) circularly executing the steps (2-3) to (2-6) until the screening of all the points in the point set P is finished, and storing the screened result into the point set P'.
4. The pseudo mountain vertex rejection method according to claim 1, wherein: the step (4) specifically comprises the following steps:
(4-1) for Point set P'Any point p 'in'iAnd the height is marked as height, all tuples corresponding to the edges with the adjacency relation are found out from the H, and the tuples are stored into a set H', H { (e)1,h1),...,(em,hm) Wherein m is 'with point p'iThe number of edges having an adjacency, and m<n；
(4-2) traversing each tuple in the set H', and judging whether a tuple (e) exists or notk,hk) Satisfy height-hk<h, if present, dot p'iDeleting from the point set P'; wherein h is a preset threshold value, k belongs to [1, m ∈]；
And (4-3) circularly executing the steps (4-1) to (4-2) until the elevation screening of all the points in the point set P 'is completed, and storing the screened result in the point set P'.
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