CN114898095A - A Data Downsizing Method for Linear Feature Spots in National Land Survey - Google Patents

Abstract

The invention discloses a data downscaling method oriented to a land survey linear feature map, which realizes efficient and accurate dimension reduction of a land survey linear feature map into a linear feature. The main steps of the invention include: according to the national land survey Data downsizing technical specifications, identifying linear feature patches that need to be reduced in dimension to linear features; dimensionality reduction and segmentation and dissolution of linear feature patches whose long sides overlap with administrative boundaries; based on Delaunay triangulation algorithm The linear feature map spot is a constrained triangular network, and the skeleton line is extracted; the triangular network is optimized, the skeleton line is redrawn, the spike contour disturbance of the linear feature map spot is corrected, and the end jitter is corrected, which is used as the linear feature map spot for dimensionality reduction After the linear features; take the common connection point of the adjacent patch boundary as the end point, draw the linear feature map segmentation line, trim the redundant skeleton line, divide the linear feature map, and dissolve it into the corresponding adjacent patch. , to form the final national land survey data reduction results.

Description

A Data Downsizing Method for Linear Feature Spots in National Land Survey

technical field

The invention relates to the technical field of land survey data downsizing, in particular to a data downscaling method for land survey linear feature patterns.

Background technique

In the downsizing of national land survey data, reducing the dimension of linear feature maps to linear features is essentially the problem of extracting skeleton lines from linear feature maps. Map downsizing is the downsizing of large-scale digital maps into a series of small-scale maps; downsizing is a kind of cartography. In the comprehensive process, it is necessary to select and summarize the cartographic objects, select the information useful for the cartographic purpose to keep on the map, and discard the unnecessary information; at the same time, simplify the shape, quantity and quality characteristics of the cartographic objects to meet the The professional needs of different industries and departments for spatial data processing, such as data product production, data desensitization and declassification, etc., avoid repeated production and save the investment of manpower, material resources and funds. In the process of map downsizing, when the widths of long and narrow objects such as roads and rivers do not meet the minimum requirements of the above map, they need to be converted into linear symbols, and the linear feature patches should be decomposed into multiple patches and dissolved to adjacent areas. Figure spots.

Aiming at reducing the dimension of linear feature map spots to linear features, the current common method is to use computer graphics comprehensive software to perform man-machine interactive downscaling, which has shortcomings such as low efficiency, long time, and inability to guarantee quality. A data downscaling method for linear feature patches in land surveys.

SUMMARY OF THE INVENTION

In order to solve the deficiencies mentioned in the above-mentioned background art, the purpose of the present invention is to provide a data reduction method for the linear feature pattern of national land survey.

The object of the present invention can be realized through the following technical solutions: a data reduction method for the linear characteristic pattern of land survey, the method comprises the following steps:

Step 1: Identify the linear feature patches that need to be reduced in dimension to linear features according to the technical specifications for the downsizing of national land survey data;

Step 2: Since the boundaries of administrative regions are mostly divided according to mountains, rivers, etc., if the linear feature map spots are reduced to linear features in the way of obtaining triangular nets and skeleton lines, it is not in line with the actual business situation. Therefore, if the long side of the linear feature map spot coincides with the boundary of the administrative region, the administrative region boundary is directly taken as the linear feature after the linear feature map has been reduced. , only one is retained. After the dimension is reduced to linear features, the linear feature map patches are dissolved into adjacent patches in blocks;

Step 3: If the long sides on both sides of the linear feature map do not coincide with the boundaries of the administrative region, construct a triangulation network constrained by the linear feature map based on the Delaunay triangulation algorithm, and extract the skeleton line;

Step 4: Optimize the triangulation, redraw the skeleton line, correct the disturbance of the spike outline of the linear feature map, and correct the end jitter, which is used as the linear feature after the dimension reduction of the linear feature map;

Step 5: Take the common connection point of the border of adjacent patches as the endpoint, obtain the segmentation line of linear feature patches, divide the linear feature patches, dissolve them into corresponding neighboring patches, and form the final result of land survey data reduction.

Further, the process of segmenting the linear feature map patches that are collinear with the administrative region boundary includes:

Extend the line segment on the adjacent patch that is connected with the linear feature patch until it intersects with the boundary of the administrative region, and divide the linear feature patch into blocks according to the line segment and dissolve it into the corresponding neighboring patch.

Further, if the long sides on both sides of the linear feature map spot are not overlapped with the administrative area boundary, a triangulation network constrained by the linear feature map spot is constructed based on the Delaunay triangulation algorithm, and the skeleton line is extracted, and the process includes:

Extend the line segment on the adjacent patch that is connected with the linear feature patch until it intersects with the boundary of the administrative region, and divide the linear feature patch into blocks according to the line segment and dissolve it into the corresponding neighboring patch.

Further, the process of optimizing the triangulation, redrawing the skeleton line, correcting the disturbance of the contour of the line feature map, and correcting the end jitter includes the following steps:

Step S1: Disturbance correction of the contour of the spot spike in the linear feature map. If the end point of the skeleton line formed in step 3 is not at the end of the linear feature map spot, it is determined as a spike contour disturbance of the linear feature map spot, delete the A-type triangle where the skeleton line segment of the end point is located, form a new triangular network, and redraw Skeleton line.

Step S2: end jitter correction. The angle between the skeleton line of the A-type triangle and the skeleton line of the other triangle connected to it is not equal to 180°, and it is determined that the end is shaking. Connect the midpoints of the triangles of class A and other triangles with the vertex corresponding to the common edge and the midpoint of the other two sides respectively, and calculate the angle between the skeleton line of the triangle of class A and the three line segments above, and keep the three included angles. The line segment corresponding to the smallest absolute value of the 180° difference is one of the line segments of the linear feature after the spot dimension reduction of the linear feature map. The new skeleton line formed after the end jitter correction is the linear feature after the dimension reduction of the linear feature map.

Further, the process of obtaining the line-like feature graph spot segmentation line with the common connection point of the adjacent graph spot boundary as the endpoint, dividing the linear feature graph spot, and dissolving it into the corresponding adjacent graph spot includes the following steps:

Step W1: Draw the division line of the spot. Extending the line segment connected with the linear feature pattern spot on the adjacent pattern spot to intersect with the skeleton line formed in step S2;

Step W2: Redundant skeleton line trimming. The skeleton line segment between the end point of the skeleton line formed in step S2 and the intersection point obtained in step W1 is a redundant line segment, which is deleted, and the deleted line segment is the dividing line of the linear feature map spot;

Step W3: Dissolving in pieces. According to the dividing line formed in step W2, the linear feature patch is divided into a plurality of sub-patches, which are respectively dissolved into corresponding adjacent patches.

Beneficial effects of the present invention:

To sum up, the present invention proposes a data downscaling method for the linear feature map of national land survey, which takes into account the actual business situation that the long side of the linear feature map coincides with the boundary of the administrative region, and the linear feature map The contour disturbance and end jitter of the spot spikes are corrected. At the same time, the linear features and the segmentation lines of the linear feature map after the dimension reduction of the linear feature map are clearly defined. The linear features are designed to reflect the geometry of the linear feature map. The dividing line takes into account the adjacent patches, and aims to reasonably divide the linear feature patches and dissolve them into the adjacent patches. It has the characteristics of mature theory, easy programming, high efficiency, and relatively optimal skeleton line extraction.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. In other words, on the premise of no creative work, other drawings can also be obtained from these drawings;

Fig. 1 is the schematic flow chart of the present invention;

Figure 2 is a schematic diagram of the drawdown when the long side of one side of the linear feature map spot coincides with the boundary line of the administrative region, wherein Figure 2(a) is a schematic diagram of the map spot before the drawdown, and Figure 2(b) is a schematic diagram of the dissolution of the line object and the map spot after the drawdown;

Fig. 3 is a schematic diagram of a Delaunay triangulation triangle and a skeleton line;

Figure 4 is the line feature map speckle spike contour disturbance correction and end jitter correction, in which Figure 4(a) is a schematic diagram of the line feature map speckle spike contour before disturbance correction, and Figure 4(b) is the line feature map speckle tip Figure 4(c) is the schematic diagram before the end jitter correction, and Figure 4(d) is the schematic diagram after the end jitter correction;

Figure 5 is a schematic diagram of segmentation and dissolution of linear feature maps, in which Figure 5(a) is a schematic diagram of dividing lines and a schematic diagram of redundant skeleton lines before trimming, and Figure 5(b) is a schematic diagram of redundant skeleton lines after trimming.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

As shown in Figure 1, a method for data downscaling for linear feature maps of national land survey, the method includes the following steps:

Step 1: Identify the linear feature patches. This step has been supported by relevant standards and norms and mature theories, and will not be repeated here;

Step 2: Perform dimensionality reduction and segmentation and dissolution of the linear feature patches whose long sides coincide with the boundaries of the administrative districts. It needs to be further explained that this step mainly considers that in the actual situation, different administrative regions are mostly divided according to mountains, rivers, etc., and the linear feature pattern on the boundary side of the administrative region is also reflected by the skeleton line. Accurate, the present invention proposes to directly take the administrative area boundary as the linear feature map after dimension reduction, which is more in line with the actual situation;

As shown in Figure 2, the long side of the linear feature map spot C coincides with the administrative area boundary, and the Q ₁ Q ₂ section of the administrative area boundary line is the linear feature after the dimension reduction of the graph spot C, while extending the adjacent graph spots A, The line segment P ₁ P ₂ is connected to the linear feature map segment C to the administrative area boundary point P ₃ , and the line segment P ₂ P ₃ divides the linear feature map segment C into two parts C ₁ and C ₂ , and C ₁ is dissolved in In patch A, C ₂ is dissolved in patch B, and the result of the reduction of linear feature patch C is obtained.

Step 3: If the long sides on both sides of the linear feature map do not coincide with the boundaries of the administrative region, construct a triangulation network constrained by the linear feature map based on the Delaunay triangulation algorithm, and extract the skeleton line;

As shown in Figure 3, with the linear feature patches as constraints, a triangulation network is constructed based on the Delaunay triangulation algorithm, and the obtained triangles are all within the linear feature patches, which are divided into three categories: A, B, and C, among which the A-type triangles There are adjacent triangles on one side, as shown in Figure 3 △P ₁ P ₂ P ₈ , △P ₂ P ₃ P ₄ , △P ₅ P ₆ P ₇ , the midpoint connecting the triangle vertices and the common side of the adjacent triangles is the line segment of the skeleton line, As shown in Figure 3, P ₁ Q ₁ , P ₃ Q ₂ , P ₆ Q ₅ , P ₁ , P ₃ , and P ₆ are also called endpoints; a type B triangle has adjacent triangles on both sides, as shown in Figure 3 △P ₄ P ₇ P _8. △P ₄ P ₅ P ₇ , connecting two adjacent triangles with the midpoint of the common side as the line segment of the skeleton line, as shown in Figure 3 Q ₃ Q ₄ , Q ₄ Q ₅ ; Class C triangles have adjacent triangles on the three sides, such as For △P ₂ P ₄ P ₈ in Figure 3, first determine its center of gravity, and connect the midpoint of each side to the center of gravity as a line segment of the skeleton line, as shown in Figure 3 Q ₁ O, Q ₂ O, Q ₃ O. Corresponding line segments are extracted from all triangles according to the three types of triangle connection rules to form the skeleton line of the linear feature pattern.

Step 4: Optimize the triangular network, correct the disturbance of the spike outline of the linear feature map, redraw the skeleton line, and correct the end jitter, and use it as the linear feature after the dimension reduction of the linear feature map;

It should be further explained that, in the specific implementation process, the process of correcting the contour disturbance of the spot spike in the linear feature map and correcting the end jitter includes the following steps:

Step S1: Disturbance correction of the contour of the spot spike in the linear feature map. For linear feature patches similar to "one", the skeleton line reflecting the geometric features of the patch should have only two endpoints. The line should have only three endpoints. For a similar "cross"-shaped linear feature pattern, the skeleton line reflecting the geometric characteristics of the pattern should have only four endpoints. For a similar "I"-shaped linear feature pattern, it should reflect the geometric characteristics of the pattern. The skeleton line of the The third method to obtain the skeleton line, there will be redundant endpoints, so that the skeleton line has many bifurcations, which cannot directly reflect the geometric characteristics of the linear feature pattern.

As shown in Figure 4(a), it is a "one"-shaped pattern spot. After the skeleton line is obtained according to the method in step 3, there are three end points P ₁ , P ₃ and P ₅ , but obviously P ₁ and P ₅ are the ends. The end point, P ₃ is the end point caused by the existence of sharp thorns in the outline of the pattern, which needs to be corrected. The correction method is to delete the triangles △P ₂ P ₃ P ₄ , △ P ₂ P ₄ P ₆ corresponding to the skeleton line segment P ₃ Q ₁ where the endpoint P ₃ is located, from the C-type triangle to the B-type triangle, and the triangle formed by the new triangle The network redraws the skeleton line, and corrects the spike disturbance of the linear feature map spot outline, as shown in Figure 4(b).

Step S2: jitter correction at the end of the linear feature pattern spot. As shown in Figure 4(c), the end of the linear feature map spot is a type A triangle, and the direction is determined by the line connecting the midpoint of the common triangle and the vertex of the type A triangle, which cannot accurately reflect the true direction of the end of the linear feature map spot, ∠ Q ₄ Q ₂ P ₅ and ∠Q ₅ Q ₃ P ₁ are not equal to 180°, so there is end jitter.

Find the midpoints of the two non-common sides of the two triangles at the end, R ₁ , R ₂ , R ₃ , R ₄ , calculate ∠Q ₅ Q ₃ R ₁ , ∠Q ₅ Q ₃ P ₁ , ∠Q ₅ Q ₃ R ₂ , and calculate the absolute value of the difference from 180°, the absolute value of the difference between ∠Q ₅ Q ₃ P ₁ and 180° is the smallest, the skeleton line retains P ₁ Q ₃ , and the other end is corrected in the same way, ∠ The absolute value of the difference between Q ₄ Q ₂ R ₃ and 180° is the smallest, the skeleton line retains R ₃ Q ₂ , and a new skeleton line with P ₁ and R ₃ ends formed after the end jitter correction is a linear feature map Linear features after spot dimensionality reduction, as shown in Figure 4(d)

Step 5: Downsizing of the national land survey data In addition to reducing the dimension of the linear feature maps to linear features, it is also necessary to dissolve the linear feature maps into adjacent maps. The specific method is to take the common connection point of the border of adjacent patches as the endpoint, obtain the segmentation line of the linear feature patch, segment the linear feature patch, dissolve it into the corresponding neighboring patch, and form the final national land survey data reduction result.

It should be further explained that, in the specific implementation process, the common connection point of the border of adjacent patches is used as the endpoint to obtain the segmentation line of the linear feature map, segment the linear feature map, and dissolve it into the corresponding adjacent patch. The process includes the following steps:

Step W1: Draw the division line of the spot. Since the purpose of patch segmentation is to dissolve into adjacent patches, segmentation is performed with the common connection point of adjacent patch boundaries as endpoints. As shown in Figure 5(a), the common connection points of the borders of the three adjacent patches of the linear feature patch are P ₂ , P ₄ , and P ₆ , and the line segment connected to the linear feature patch on the adjacent patch is extended to reach the skeleton. The lines intersect, extending P ₁ P ₂ to Q ₁ , P ₃ P ₄ to Q ₂ , P ₅ P ₆ to Q ₃ , respectively.

Step W2: Redundant skeleton line trimming. The dividing line drawn by the above steps has redundant line segments P ₇ Q ₁ and P ₈ Q ₃ from the dividing point to the end point. Trim the redundant line segments and divide the linear feature map into three parts, as shown in the figure after trimming. 5(b).

Step W3: Dissolving in pieces. The three parts divided in step W2 are respectively dissolved into three adjacent corresponding spots.

The final downscaling results of the linear feature patches are the linear features after dimensionality reduction and the dissolved patches, and the results are shown in Figure 4(d) and Figure 5(b).

The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention.

Claims (5)

1. A data compiling method for homeland survey linear characteristic pattern spots is characterized by comprising the following steps:

the method comprises the following steps: identifying linear characteristic pattern spots needing dimension reduction into linear ground objects according to the technical specification of homeland survey data compilation;

step two: because the administrative area boundary is divided according to mountains, rivers and the like, if the linear feature pattern spots are reduced into linear ground objects in a manner of obtaining skeleton lines according to a triangulation network, the actual business situation is not met, if the long edge of one side of each linear feature pattern spot is overlapped with the administrative area boundary, the administrative area boundary is directly used as the linear ground objects after the linear feature pattern spots are contracted and woven, only one linear feature pattern spot is reserved when the linear feature pattern spots on the two sides of the administrative area boundary are reduced into the same administrative area boundary, and after the linear feature pattern spots are reduced into the linear ground objects, the linear feature pattern spots are dissolved into adjacent pattern spots in a blocking manner;

step three: if the long edges of the two sides of the linear characteristic pattern spots are not coincident with the administrative area boundary lines, constructing a triangular net which takes the linear characteristic pattern spots as constraints based on a Delaunay triangulation algorithm, and extracting skeleton lines;

step four: optimizing a triangular net, redrawing a skeleton line, correcting the sharp-prick profile disturbance of the linear characteristic pattern spot, and correcting the end shake to serve as a linear ground object after the dimension of the linear characteristic pattern spot is reduced;

step five: and taking the public connection point of the boundary of the adjacent pattern spots as an end point, obtaining a linear characteristic pattern spot segmentation line, segmenting the linear characteristic pattern spots, and dissolving the linear characteristic pattern spots into the corresponding adjacent pattern spots to form a final homeland survey data compilation result.

2. The data compiling method for national survey linear feature patches according to claim 1, wherein the process of blocking the linear feature patches collinear with administrative area boundaries comprises the following steps:

and extending the line segment on the adjacent pattern spot, which is connected with the linear feature pattern spot, until the line segment is intersected with the administrative area boundary line, and partitioning and dissolving the linear feature pattern spot into the corresponding adjacent pattern spot according to the line segment.

3. The data compiling method for the linear feature map spot facing the homeland survey according to claim 1, wherein if the long edges of the two sides of the linear feature map spot are not coincident with the administrative region boundary line, a triangulation network with the linear feature map spot as a constraint is constructed based on a Delaunay triangulation algorithm, and a skeleton line is extracted, and the process comprises the following steps:

the method comprises the steps of taking linear characteristic diagram spots as constraints, constructing a triangulation network based on a Delaunay triangulation algorithm, dividing triangles of the triangulation network into a type A, a type B and a type C, wherein one side of the type A triangle is provided with an adjacent triangle, two sides of the type B triangle are provided with adjacent triangles, three sides of the type C triangle are provided with adjacent triangles, for the type A triangle, the middle point of the common side of the vertex of the connected triangle and the adjacent triangle is a line segment of a skeleton line, for the type B triangle, the middle point of the common side of two adjacent triangles is connected to be a line segment of the skeleton line, for the type C triangle, the gravity center of the type C triangle is determined, the middle point of each side and the gravity center are connected to be a line segment of the skeleton line, and all triangles extract corresponding line segments according to the connection rule of the types three triangles to form the skeleton line of the linear characteristic diagram spots.

4. The data compiling method for the homeland survey linear feature pattern spot facing to the claim 1 is characterized in that the process of optimizing the triangulation network, redrawing the skeleton line, correcting the sharp-prick profile disturbance of the linear feature pattern spot and correcting the terminal jitter comprises the following steps:

step S1: correcting the sharp spine profile disturbance of the linear characteristic pattern spot, if the end point of the skeleton line formed in the step three is not at the tail end of the linear characteristic pattern spot, judging that the sharp spine profile disturbance of the linear characteristic pattern spot is generated, deleting a type A triangle where the skeleton line segment of the end point of the skeleton line is located, forming a new triangular net, and redrawing the skeleton line;

step S2: and correcting the terminal jitter, wherein the included angle between the skeleton line of the A-type triangle and the skeleton line of the other triangle connected with the skeleton line of the A-type triangle is not equal to 180 degrees, judging that the terminal jitter exists, respectively connecting the common midpoint of the A-type triangle and the other triangles with the vertex corresponding to the common side and the midpoints of the other two sides, calculating the included angles between the skeleton line of the triangle common to the A-type triangle and the three line segments, keeping the corresponding line segment with the minimum absolute value of the difference value of 180 degrees in the three included angles, wherein the line segment is one of the line segments of the linear ground object after the dimension of the linear feature pattern spot is reduced, and a new skeleton line formed after correcting the terminal jitter is the linear ground object after the dimension of the linear feature pattern spot is reduced.

5. The data compiling method facing to the territorial survey linear feature pattern spot is characterized in that the process of obtaining a linear feature pattern spot segmentation line by taking a public connection point of a boundary of an adjacent pattern spot as an end point, segmenting the linear feature pattern spot and dissolving the linear feature pattern spot into the corresponding adjacent pattern spot comprises the following steps:

step W1: drawing a pattern spot segmentation line, and extending a line segment which is connected with the linear characteristic pattern spot on the adjacent pattern spot until the line segment is intersected with the skeleton line formed in the step S2;

step W2: trimming redundant skeleton lines, namely deleting redundant line segments from the end points of the skeleton lines formed in the step S2 to the intersection points acquired in the step W1, wherein the deleted line segments are the dividing lines of the linear characteristic pattern spots;

step W3: and (5) block dissolving, namely, dividing the linear characteristic pattern spot into a plurality of sub-pattern spots according to the dividing line formed in the step W2, and dissolving the sub-pattern spots into corresponding adjacent pattern spots respectively.

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