A method and device for gradually simplifying surface residential area elements taking into account structural characteristics

Abstract

The present invention proposes a method and device for gradual simplification of planar residential elements that take into account structural features. First, the residential polygon data is obtained, including the number of polygon vertices, vertex coordinates, and the length of each side; then, based on the number of polygon vertices and the length of each side of the polygon, it is determined whether the polygon simplification conditions are met; when the polygon simplification conditions are met, the top priority simplification vertex and its two neighboring points are found; finally, the polygons are classified according to the angles and convexity of the top priority simplification vertex and its neighboring points, and the polygons are simplified in a corresponding manner according to different types of polygons, until the number of polygon vertices after simplification is less than or equal to a set threshold or the shortest side length in the simplified polygon is greater than a set minimum visible length threshold. The present invention maintains the contour features in the polygon simplification process as much as possible, ensures that the area change of the polygon after simplification is minimal, and takes into account the right-angle characteristics of the polygon, and is suitable for simplification of various polygons.

Description

Technical Field

[0001] The invention relates to a method and device for gradually simplifying planar residential area elements taking into account structural characteristics, belonging to the technical field of planar element simplification in map synthesis. Background Art

[0002] In the large-scale map automation synthesis, building (group) simplification is an important issue that has received extensive attention from experts and scholars at home and abroad, and has achieved relatively rich research results. In the process of single element simplification, the principle of simplification is to maintain the morphological characteristics, area size and obvious right-angle characteristics of the building polygon before and after simplification, and if the building has been simplified into a rectangle or quadrilateral, the building polygon cannot be simplified again. At present, building polygon simplification algorithms are roughly divided into three categories: raster-based simplification methods, vector-based simplification methods, and raster-vector combined simplification methods.

[0003] In the early simplification methods based on raster data, polygon outline simplification was mainly carried out through mathematical morphology methods, but it was not conducive to maintaining the area of ​​polygons during simplification. In recent years, many scholars have tried to use superpixels and deep learning methods to simplify polygons. The simplification methods based on machine learning have a high degree of automation, but they are highly dependent on the number and quality of sample training sets. The simplification method based on superpixel segmentation has not yet achieved the simplification of right-angled buildings. The simplification method based on raster-vector combination can give full play to the advantages of raster data processing and vector data processing, and has a good simplification effect on building polygons with obvious right-angle features at large scales, but the simplification of complex buildings is still unsatisfactory. In addition, the simplification method based on raster data has the problem of increasing the amount of calculation during the vector-raster conversion process and causing the loss of vector data attribute information. There are many methods based on vector simplification. Among them, the Delaunay simplification method can take into account the overall morphological characteristics of polygons well, but it is not conducive to maintaining the right-angle features and area of ​​buildings. Based on the adjacent four-point or five-point simplification method, a simplification algorithm that takes area into consideration is designed to simplify various types of buildings. However, when simplifying across a large scale, it is difficult to maintain the morphological characteristics of the building. The building simplification method based on shape matching can better maintain the shape characteristics and area size before and after simplification, but due to the limitation of the template library type, it is not ideal for simplification of polygons with complex structures. From the existing research, there are many building simplification algorithms, but under the condition of spanning a large scale, it is difficult to take into account the right angle characteristics, shape characteristics, area preservation and universality in simplification. Summary of the invention

[0004] The present invention provides a method and device for gradually simplifying planar residential area elements taking into account structural characteristics, so as to solve the problem that it is difficult to simultaneously take into account right-angle characteristics, shape characteristics and area preservation in existing planar element simplification methods.

[0005] The present invention proposes a method for gradually simplifying planar residential area elements taking into account structural characteristics, the method comprising the following steps:

[0006] 1) Obtaining polygonal data of residential areas in the target area, including the number of polygon vertices, vertex coordinates and length of each side;

[0007] 2) judging whether the polygon simplification condition is met according to the number of polygon vertices and the length of each side of the polygon, wherein the polygon simplification condition is: the number of polygon vertices is greater than a set number threshold and the length of the shortest side of the polygon is less than a set minimum visible length threshold;

[0008] 3) When the polygon simplification conditions are met, find the shortest side of the polygon, determine the structural area of ​​the vertex corresponding to the shortest side, and take the vertex with the smallest corresponding structural area as the top priority simplification vertex of the polygon; and find the two adjacent points of the top priority simplification vertex; wherein the vertex structural area is the area of ​​the parallelogram formed based on the two adjacent sides of the vertex;

[0009] 4) Classify the polygons according to the angles of the highest priority simplified vertex and its neighboring points found, and simplify them using the corresponding simplification method according to the category to which the polygon belongs, so that the difference between the area of ​​the polygon after simplification and the area of ​​the polygon before simplification is minimized or the increased area of ​​the polygon after simplification is less than or equal to 10% of the area of ​​the polygon before simplification, and obtain the simplified polygon; determine again whether the simplified polygon meets the polygon simplification conditions; when the polygon simplification conditions are met, continue to simplify the simplified polygon until the number of vertices of the simplified polygon is less than or equal to the set threshold or the shortest side length of the simplified polygon is greater than the set minimum visible length threshold.

[0010] The present invention also proposes a device for gradually simplifying planar residential areas taking into account structural features. The device includes a processor and a memory. The processor executes a computer program stored in the memory to implement the method for gradually simplifying planar residential areas.

[0011] The present invention first finds the shortest side of the polygon, determines whether simplification is needed according to the length of the shortest side and the number of polygon vertices, and determines the top-priority simplified vertex according to the structural area of ​​the two vertices corresponding to the shortest side. The polygon is simplified based on the angle and convexity of the top-priority simplified vertex and its adjacent points, maintaining the contour features of the polygon during the simplification process as much as possible, ensuring that the area change of the polygon after simplification is minimal, while taking into account the right-angle characteristics of the polygon, and is suitable for simplification of various polygons.

[0012] Furthermore, in order to quickly realize polygon simplification, the polygons are divided into the following four types in step 4), the first type is that the top priority simplification vertex is a right angle, and there is a right angle in the adjacent points; the second type is that the top priority simplification vertex is a right angle, and there is no right angle in the adjacent points; the third type is that the top priority simplification vertex is a non-right angle, and there is a right angle in the adjacent points; the fourth type is that the top priority simplification vertex is a non-right angle, and there is no right angle in the adjacent points;

[0013] According to the order of polygon vertex connection, the adjacent point connected counterclockwise to the highest priority simplified vertex is taken as the front vertex, the adjacent point connected clockwise to the highest priority simplified vertex is taken as the back vertex, the edge formed by the highest priority simplified vertex and the front vertex is taken as the front adjacent edge, the edge formed by the highest priority simplified vertex and the back vertex is taken as the back adjacent edge, the adjacent edge connected counterclockwise to the front adjacent edge is taken as the first adjacent edge, and the edge connected clockwise to the back adjacent edge is taken as the second adjacent edge.

[0014] Furthermore, in order to quickly simplify polygons according to the angle characteristics and concavity of different vertices, when the polygon is of the first type, it is divided into three-point concavity-convexity same type, adjacent point concavity-convexity different type and adjacent point concavity-convexity same type according to the concavity-convexity of the most prioritized simplified vertex and its two adjacent points;

[0015] When the three points of the most prioritized simplified vertex and its neighboring points have the same concavity and convexity and are all convex, find a point on the front adjacent side of the polygon as a parallel line of the rear adjacent side by using the moving point search method, and extend the intersection of the parallel line and the extended line of the first adjacent side, and take the area between the parallel line and the rear adjacent side in the polygon as the deleted part, and take the area formed by the intersection, the front vertex and the moving point on the front adjacent side as the added part, and determine the position of the moving point according to the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and simplify the polygon according to the determined moving point position; wherein, the rear vertex is a right angle, and the front vertex is a non-right angle;

[0016] When the three points of the most prioritized simplified vertex and its neighboring points have the same concavity and convexity and are all concave, draw a parallel line to the front adjacent side through the rear vertex, and take the area between the front adjacent side and the parallel line to the front adjacent side as the added part. When the area of ​​the added part is less than or equal to 10% of the area of ​​the polygon before simplification, determine the intersection point of the parallel line to the front adjacent side and the first adjacent side, and simplify the polygon according to the determined intersection point.

[0017] When the concavity and convexity of the adjacent points are different, find the adjacent points that are different from the concavity and convexity of the highest priority simplified vertex, use the edge formed by the highest priority simplified vertex and the found adjacent points as the simplified edge, find a point on the simplified edge by the moving point search method, draw parallel lines of two adjacent edges adjacent to the simplified edge, use the area between one of the adjacent edges and its parallel lines as the added part or the deleted part, use the area between the other adjacent edge and its parallel lines as the deleted part or the added part, determine the position of the moving point according to the minimum difference between the deleted area and the added area, and simplify the polygon according to the determined position of the moving point; wherein, the deleted part is the part where the adjacent points of the convex point are located, and the added part is the part where the adjacent points of the concave point are located.

[0018] When the concavity and convexity of adjacent points are the same, a point is found on the front adjacent side to be a parallel line of the first adjacent side, and a point is found on the back adjacent side to be a parallel line of the second adjacent side by the moving point finding method, so that the ratio of the length of the line segment formed by the intersection point of the most prioritized simplified vertex and the front adjacent side to the length of the line segment formed by the intersection point of the most prioritized simplified vertex and the back adjacent side is equal to the ratio of the length of the front adjacent side to the length of the back adjacent side, and the area between the parallel line of the first adjacent side and the first adjacent side and the area between the parallel line of the second adjacent side and the second adjacent side in the polygon is taken as the deleted part or the added part, and the area between the front adjacent side, the back adjacent side, the parallel line of the first adjacent side, and the parallel line of the second adjacent side is taken as the added part or the deleted part, and the position of the moving point is determined according to the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and the polygon is simplified according to the determined position of the moving point; wherein, the deleted part is the part where the convex point is located, and the added part is the part where the concave point is located.

[0019] Furthermore, in order to display and retain the important features of the polygonal contour of the face element, when the polygon is of the first type and the structural area of ​​the most prioritized simplified vertex is greater than the set area threshold, a point is found on the rear adjacent edge through the moving point search method to make a parallel line segment of the front adjacent edge, and intersect with the first adjacent edge. The intersection point is used as a vertex of the parallel line, so that the parallel line segment is equal to the minimum visible length threshold, and a parallel line of the rear adjacent edge is made through another vertex of the parallel line segment, intersecting the second adjacent edge at a point; the area formed by the parallel lines of the front adjacent edge and the first adjacent edge is used as the deleted part or the added part, and the area where the parallel lines of the rear adjacent edge and the second adjacent edge are located is used as the added part or the deleted part, the moving point position is determined based on the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and the polygon is simplified based on the determined moving point position; wherein, the deleted part is the part where the adjacent points of the convex point are located, and the added part is the part where the adjacent points of the concave point are located.

[0020] Furthermore, in order to quickly simplify polygons according to the angular characteristics and convexity of different vertices, when the polygon is of the second type, a point is found on the front adjacent edge and the rear adjacent edge through the moving point search method to make a parallel line to the straight line where the front vertex and the rear vertex are located, and the area between the front adjacent edge and the rear adjacent edge and the parallel line is used as an added part or a deleted part, and the area between the parallel line, the front adjacent edge, and the first adjacent edge and the area between the parallel line, the rear adjacent edge, and the second adjacent edge are used as a deleted part or an added part. The position of the moving point is determined based on the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and the polygon is simplified based on the determined position of the moving point; wherein, the deleted part is the part where the highest priority vertex is located when it is a convex point, and the added part is the part where the highest priority vertex is located when it is a concave point.

[0021] Furthermore, in order to enhance the right-angle characteristics in the polygon simplification process, when the polygon is of the third type, the edge formed by the most prioritized simplified vertex and the right-angled adjacent point is taken as the right-angled edge, the edge formed by the most prioritized simplified vertex and the non-right-angled adjacent point is taken as the hypotenuse, and the adjacent edge of the hypotenuse passing through the non-right-angled adjacent point is taken as the adjacent edge of the hypotenuse;

[0022] A point is found on the hypotenuse by a moving point search method, a perpendicular line to the right-angled side is drawn through the point, the perpendicular line is extended in the direction of the side adjacent to the hypotenuse, so that the length of the extended perpendicular line is equal to the distance from the highest priority simplified vertex to the side adjacent to the hypotenuse, the area between the perpendicular line, the hypotenuse and the right-angled side is used as a deleted part or an added part, the area between the perpendicular line, the hypotenuse and the side adjacent to the hypotenuse is used as an added part or a deleted part, the position of the moving point is determined according to the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and the polygon is simplified according to the determined position of the moving point; wherein, when the highest priority simplified vertex is a concave point and an acute angle or a convex point and an obtuse angle, the deleted part is the part where the non-right-angled adjacent point is located, and the added part is the part where the highest priority simplified vertex is located; when the highest priority simplified vertex is a concave point and an obtuse angle or a convex point and an acute angle, the deleted part is the part where the highest priority simplified vertex is located, and the added part is the part where the non-right-angled adjacent point is located.

[0023] Furthermore, in order to maintain the contour features and area size of the polygon as much as possible, when the polygon is of the fourth type, the area comparison simplification method is used to make a perpendicular line to the rear adjacent side through the front vertex and intersect the rear adjacent side at the first point, the first adjacent side and the rear adjacent side are extended to intersect at the second point, the perpendicular line to the front adjacent side through the rear vertex and intersects the front adjacent side at the third point, the second adjacent side and the front adjacent side are extended to intersect at the fourth point, the area formed by the first point, the second point and the front adjacent side is calculated respectively, the area formed by the third point, the fourth point and the rear adjacent side and the area of ​​the triangle formed by the front adjacent side and the rear adjacent side are calculated respectively, the point with the smallest corresponding area is found, the highest priority simplified vertex is moved to this point, and the polygon is simplified.

[0024] Furthermore, in order to avoid the difficulty in maintaining the polygonal shape features due to the large moving distance, in step 4), when the distance between the vertex and the corresponding moving point is greater than the minimum visible length threshold, a new moving point whose distance from the vertex is equal to the minimum visible length threshold is found on the straight line where the vertex and the moving point are located, and the vertex is moved to the new moving point.

[0025] Furthermore, in order to reduce the amount of calculation and memory usage, the step 1) and the simplification process also require the removal of the straight-angle vertices in the polygon. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of the method for gradually simplifying the planar residential area elements taking into account the structural characteristics of the present invention;

[0027] Figure 2 is a schematic diagram of determining the top priority simplified vertex of the present invention;

[0028] Figure 3 It is a simplified schematic diagram of the convex-convex-convex type in the first category of the present invention;

[0029] Figure 4 It is a simplified schematic diagram of the concave-concave-concave type of the first type of the present invention;

[0030] FIG5( a ) is a simplified schematic diagram of a concave-convex shape in which adjacent vertices are all at right angles in the first category of the present invention;

[0031] FIG5( b ) is a simplified schematic diagram of a concave-convex shape in which adjacent vertices have non-right angles in the first category of the present invention;

[0032] FIG6( a ) is a simplified schematic diagram of the first type of concave-convex-concave type in the present invention;

[0033] FIG6( b ) is a simplified schematic diagram of the convex-concave-convex type in the first category of the present invention;

[0034] Figure 7 It is an exaggerated processing schematic diagram of the first category of the present invention;

[0035] FIG8( a ) is a simplified schematic diagram of the second type of convex-concave-convex type of the present invention;

[0036] FIG8( b ) is a simplified schematic diagram of the concave-convex-convex type of the second type of the present invention;

[0037] FIG9( a ) is a simplified schematic diagram of the convex-concave-convex type in the third category of the present invention;

[0038] FIG9( b ) is a simplified schematic diagram of the convex-convex-convex type in the third category of the present invention;

[0039] FIG9( c ) is a simplified schematic diagram of the third type of the present invention;

[0040] Fig.10It is a simplified schematic diagram of the fourth category of the present invention;

[0041] Fig.11 It is a schematic diagram of vertex shift control of the present invention. DETAILED DESCRIPTION

[0042] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0043] Method Embodiment

[0044] The present invention proposes a method for gradually simplifying the elements of a planar residential area taking into account structural characteristics. The specific process is as follows: Figure 1 As shown. First, obtain the polygon data of the residential area in the target area, including the number of polygon vertices, vertex coordinates and the length of each side; then determine whether the polygon simplification conditions are met based on the number of polygon vertices and the length of each side of the polygon; then, when the polygon simplification conditions are met, find the top priority simplification vertex and its two neighboring points; finally, classify the polygons according to the angles of the top priority simplification vertex and its neighboring points, and simplify them in a corresponding manner according to the different types of polygons, until the number of polygon vertices after simplification is less than or equal to the set threshold or the shortest side length in the simplified polygon is greater than the set minimum visible length threshold. The present invention maintains the contour features in the polygon simplification process as much as possible, ensures that the area change of the polygon after simplification is minimal, and takes into account the right-angle characteristics of the polygon, and is suitable for simplification of various polygons.

[0045] Step 1. Data acquisition and processing

[0046] The present invention first obtains the polygon of the surface residential area in the target area, measures each point of the building in the target area by using a total station, RTK and other instruments, and then digitizes the measured data to generate surface data. The obtained surface polygon includes the number of vertices, vertex coordinates and the length of each side of each polygon. At the same time, in order to reduce memory usage and subsequent calculations, the flat corner points in the polygon need to be eliminated.

[0047] In addition, due to measurement errors and map digitization errors, it is difficult for the obtained vector building polygons to have right angles or parallel lines in the strict sense, and there are often certain angle errors. The critical value of the angle error is called the angle error threshold. The present invention regards angles within the angle error threshold as right angles and lines within the angle error threshold as parallel lines. As another embodiment, the angle error threshold can be determined according to the measurement accuracy and the map scale.

[0048] Step 2. Determine whether the polygon needs to be simplified

[0049] The present invention determines whether the polygon needs to be simplified based on the number of vertices of each polygon and the length of each side of the polygon. The specific process is as follows: first, set the threshold of the number of polygon vertices and the minimum visible length threshold; compare the number of vertices of each polygon with the set number threshold, when the number of vertices of the polygon is greater than the set number threshold, the polygon needs to be simplified; then compare the shortest side of the polygon with the set minimum visible length threshold, when the shortest side length is less than the minimum visible length threshold, the polygon continues to be simplified. That is, the polygon simplification condition is: the number of polygon vertices is greater than the set number threshold and the shortest side length of the polygon is less than the set minimum visible length threshold; wherein, the minimum visible length threshold refers to the actual distance corresponding to the minimum length that the human eye can distinguish on the map, generally based on 0.3mm on the comprehensive target map as the standard, and the minimum visible length threshold can be determined according to the specific scale size of the map. In this embodiment, the set number threshold is 4, as other implementation methods, the vertex number threshold can be determined according to the specific polygon structure.

[0050] Step 3. Determine the top priority simplification vertex and its neighboring points

[0051] When a polygon meets the simplification conditions, it is necessary to first determine the top priority simplification vertex and its neighboring points of the polygon. First, find the shortest side of the polygon, determine the two vertices corresponding to the shortest side, calculate the structural area of ​​the two vertices of the shortest side, and compare the size of the structural area of ​​the two vertices. The vertex with the smallest corresponding structural area is taken as the top priority simplification vertex of the polygon, and the two neighboring points of the top priority simplification vertex are found. Among them, the vertex structural area is the area of ​​the parallelogram formed based on the two adjacent sides of the vertex. Figure 2 As shown, the shortest side of polygon ABCDEF is BC. Calculate the structural area of ​​vertices B and C. The structural area of ​​vertex B is as follows: Figure 2 The area of ​​quadrilateral ABCH in which the structural area of ​​vertex C is Figure 2 From the area of ​​quadrilateral BCDG, we can see that the structural area of ​​vertex C is smaller, so vertex C is taken as the top priority vertex for simplification, and the two neighboring points (B and D) of the top priority vertex are determined at the same time.

[0052] Step 4. Polygon simplification

[0053] The present invention classifies polygons according to the angles of the most prioritized simplified vertex and its neighboring points found, simplifies polygons using corresponding simplification methods according to the categories to which the polygons belong, so that the difference between the area of ​​the polygon after simplification and the area of ​​the polygon before simplification is minimized or the area increased by the polygon after simplification is less than or equal to 10% of the area of ​​the polygon before simplification, thereby obtaining a simplified polygon; again judging whether the simplified polygon meets the polygon simplification conditions; when the polygon simplification conditions are met, continuing to simplify the simplified polygon until the number of vertices of the simplified polygon is less than or equal to a set threshold or the length of the shortest side in the simplified polygon is greater than a set minimum visible length threshold.

[0054] The present invention divides polygons into the following four types according to the angles of the top priority simplification vertex and its neighboring points. The first type is that the top priority simplification vertex is a right angle and there is a right angle in the neighboring points; the second type is that the top priority simplification vertex is a right angle and there is no right angle in the neighboring points; the third type is that the top priority simplification vertex is a non-right angle and there is a right angle in the neighboring points; the fourth type is that the top priority simplification vertex is a non-right angle and there is no right angle in the neighboring points. According to the connection order of the polygon vertices, the neighboring point connected counterclockwise to the top priority simplification vertex is regarded as the front vertex, the neighboring point connected clockwise to the top priority simplification vertex is regarded as the back vertex, the edge formed by the top priority simplification vertex and the front vertex is regarded as the front adjacent edge, the edge formed by the top priority simplification vertex and the back vertex is regarded as the back adjacent edge, the adjacent edge connected counterclockwise to the front adjacent edge is regarded as the first adjacent edge, and the edge connected clockwise to the back adjacent edge is regarded as the second adjacent edge. The specific simplification scheme of the polygon is determined according to different types.

[0055] Category 1: The top priority is to simplify vertices to right angles, and there are right angles in the adjacent vertices

[0056] When the top priority is to simplify the vertex to a right angle and there are right angles at the adjacent points, the three points are divided into three types according to their concavity and convexity, including the type with the same concavity and convexity of the three points, the type with different concavity and convexity of the adjacent points, and the type with the same concavity and convexity of the adjacent points.

[0057] Among them, when the three points have the same convexity and are all convex, that is, the simplification type is convex-convex-convex, a point is found on the front adjacent side of the polygon as a parallel line to the rear adjacent side through the moving point search method, and the parallel line is extended to find the intersection with the extension line of the first adjacent side, and the area between the parallel line and the rear adjacent side in the polygon is used as the deleted part, and the area formed by the intersection, the front vertex and the moving point on the front adjacent side is used as the added part. The position of the moving point is determined based on the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and the polygon is simplified according to the determined moving point position; wherein the rear vertex is a right angle, and the front vertex is a non-right angle. As Figure 3As shown, ABCDE is a part of the building polygon, BC is the shortest side, point C is the highest priority vertex for simplification, B is the front vertex, D is the back vertex, BC is the front adjacent side, CD is the back adjacent side, AB is the first adjacent side, points C and D are right-angled vertices, point B is a non-right-angled vertex, and all three points are convex points; find a point F on the line segment BC through the moving point search method, make a parallel line of CD through F, intersecting DE at G, and AB intersecting GF at H; take quadrilateral CDGF as the deleted part, and take triangle HFB as the added part. When the difference between the area of ​​quadrilateral CDGF and the area of ​​triangle HFB is the smallest, determine the position of point F, and at the same time determine the positions of points H and G; shift points C and D to points H and G respectively, delete point B, and simplify ABCDE to AHGE.

[0058] Among them, when the concavity and convexity of the three points are the same and all are concave, that is, the simplification type is concave-concave-concave. In order to maintain the shape characteristics of this type of polygon, a parallel line of the front adjacent side is drawn through the back vertex. This parallel line intersects with the first adjacent side at one point. The area formed by the front adjacent side and the parallel line of the front adjacent side is taken as the added part, and the intersection point of the parallel line of the front adjacent side and the first adjacent side is determined. The polygon is simplified based on the determined intersection point. At the same time, the probability of this type appearing in actual data is extremely low, and the newly added part is the area formed by the shortest side of the polygon and its adjacent sides, which has little effect on the area size of the original polygon. Figure 4 As shown, ABCDEFGHI is a part of the building polygon, point G is the highest priority vertex, F is the front vertex, H is the back vertex, GF is the front adjacent edge, GH is the back adjacent edge, EF is the first adjacent edge, the concavity and convexity of points F, G and H are all concave, point F is a right angle, point H is a non-right angle, and a perpendicular line to EF through point H intersects at J, then point F is shifted to point J, vertex G is deleted, and ABCDEFGHI is simplified to ABCDEJHI.

[0059] Among them, when the concavity and convexity of the adjacent points are different, the adjacent points with different concavity and convexity from the highest priority simplified vertex are found, and the edge formed by the highest priority simplified vertex and the found adjacent points is used as the simplified edge. A point is found on the simplified edge by the moving point search method, and parallel lines are made between two adjacent edges adjacent to the simplified edge. The area between one of the adjacent edges and its parallel lines is used as the added part or the deleted part, and the area between the other adjacent edge and its parallel lines is used as the deleted part or the added part. The position of the moving point is determined according to the minimum difference between the deleted area and the increased area, and the polygon is simplified according to the determined position of the moving point; wherein, the deleted part is the part where the adjacent points of the convex point are located, and the added part is the part where the adjacent points of the concave point are located.

[0060] Taking the concave-concave-convex type as an example, as shown in Figure 5(a) and Figure 5(b), Figure 5(a) is a simplified schematic diagram of the concave-concave-convex type with adjacent vertices at right angles; Figure 5(b) is a simplified schematic diagram of the concave-concave-convex type with adjacent vertices at non-right angles; the simplification methods of the two are the same. The specific process is as follows: the line segment ABCDEFGH is part of the building polygon, point E is the most prioritized simplified vertex, D is the front vertex, F is the back vertex, DE is the front adjacent edge, FG is the back adjacent edge, the concavity and convexity of points D, E, and F are concave, concave, and convex respectively, among which the concavity and convexity of points E and F are different, so a point J is found on EF by the moving point search method, and parallel lines of FG and DE are drawn through point J to intersect GH and CD at K and I respectively. The quadrilateral IJED is taken as the added part, and the quadrilateral FGKJ is taken as the deleted part. When the difference between the areas of quadrilateral IJED and quadrilateral FGKJ is the smallest, the position of point J is determined, and the positions of points K and I are determined at the same time. Move points D, E, and G to points I, J, and K respectively, delete point F, and simplify ABCDEFGH to ABCIJKH. When the adjacent points are all right angles, as shown in Figure 5(a), DE is parallel to FG, and point J is a straight angle vertex. The straight angle vertex will be deleted during the cyclic simplification process. Similarly, convex-concave-concave, concave-convex-convex, and convex-convex-concave types can be simplified.

[0061] Among them, for the adjacent points with the same concavity and convexity, it can be divided into concave-convex-concave type and convex-concave-convex type, and the simplification methods of the two are the same. Through the moving point search method, a point is found on the front adjacent side to be the parallel line of the first adjacent side, and a point is found on the back adjacent side to be the parallel line of the second adjacent side, so that the ratio of the length of the line segment formed by the intersection of the most prioritized simplified vertex and the front adjacent side to the length of the line segment formed by the intersection of the most prioritized simplified vertex and the back adjacent side is equal to the ratio of the length of the front adjacent side to the back adjacent side. The area between the parallel line of the first adjacent side and the first adjacent side and the area between the parallel line of the second adjacent side and the second adjacent side in the polygon are used as the deleted part or the added part, and the area between the front adjacent side, the back adjacent side, the parallel line of the first adjacent side, and the parallel line of the second adjacent side are used as the added part or the deleted part. The moving point position is determined according to the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and the polygon is simplified according to the determined moving point position; wherein, the deleted part is the part where the convex point is located, and the added part is the part where the concave point is located.

[0062] As shown in Figure 6(a), it is a concave-convex-concave type. ABCDEFGH is a part of the building polygon, DE is the shortest side, D is the most prioritized simplified vertex, C is the front vertex, E is the back vertex, CD is the front adjacent side, DE is the back adjacent side, BC is the first adjacent side, EF is the second adjacent side, and the concavity and convexity of points C, D, and E are concave, convex, and concave respectively. By using the moving point search method, find a point L on the back adjacent side DE to make a parallel line to EF, find a point J on the front adjacent side CD to make a parallel line to BC, and the parallel lines of EF intersect. GF is at M, the parallel lines of BC intersect AB at I, and IJ and ML intersect at K. Take quadrilateral KJDL as the deleted part, and take quadrilateral BIJC and quadrilateral LMFE as the added parts. When the difference between the area of ​​quadrilateral KJDL, the area of ​​quadrilateral BIJC and the area of ​​quadrilateral LMFE is the smallest, determine the positions of points I, J, K, L, and M, shift points B, D, and F to points I, K, and M respectively, delete points C and E, and simplify the building polygon ABCDEFGH to AIKMGH.

[0063] As shown in Figure 6(b), it is a convex-concave-convex type. ABCDEFGH is a part of the building polygon, BC is the shortest side, C is the most prioritized simplified vertex, B is the front vertex, D is the back vertex, BC is the front adjacent side, CD is the back adjacent side, AB is the first adjacent side, DE is the second adjacent side, and the concavity of points B, C, and D are convex, concave, and convex respectively. By using the moving point search method, find a point J on the front adjacent side BC to make a parallel line to AB, find a point L on the back adjacent side CD to make a parallel line to DE, and the parallel line of AB is The parallel line intersects AF at I, the parallel line of DE intersects EF at M, and IJ and ML intersect at K. Take quadrilateral KJDL as the added part, and quadrilateral ABJI and quadrilateral LMED as the deleted parts. When the difference between the area of ​​quadrilateral KJDL and the sum of the areas of quadrilateral ABJI and quadrilateral LMED is the smallest, determine the positions of points I, J, K, L, and M, shift points A, C, and E to points I, K, and M respectively, delete points B and D, and simplify the building polygon ABCDEFGH to IKMF.

[0064] At the same time, in order to display and retain the important features of the building's polygonal outline, some details that should be deleted according to the length threshold are exaggerated, such as narrow concave (convex) parts. When the polygon is of the first type and the structural area of ​​the most prioritized simplified vertex is greater than the set area threshold, it needs to be exaggerated. A point is found on the rear adjacent edge through the moving point search method to make a parallel line segment of the front adjacent edge and intersect with the first adjacent edge. The intersection point is used as a vertex of the parallel line, so that the parallel line segment is equal to the minimum visible length threshold. A parallel line of the rear adjacent edge is made through another vertex of the parallel line segment and intersects the second adjacent edge at one point; the area formed by the front adjacent edge and the parallel line of the front adjacent edge is used as the deleted part or the added part, and the area where the parallel line of the rear adjacent edge and the rear adjacent edge are located is used as the added part or the deleted part. The moving point position is determined based on the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and the polygon is simplified based on the determined moving point position; the deleted part is the part where the adjacent points of the convex point are located, and the added part is the part where the adjacent points of the concave point are located. Figure 7 As shown, point E is the most prioritized vertex for simplification, the length of DE is less than ε, and the area value of point E is greater than γ. It is exaggerated, that is, the length of the shortest side is extended to the minimum visible length threshold, while keeping the area equal to that after exaggeration. In polygon ABCDEFGH, DE is the shortest side and E is the most prioritized vertex for simplification, D is the front vertex, F is the back vertex, DE is the front adjacent side, EF is the back adjacent side, CD is the first adjacent side, and FG is the second adjacent side. Use the moving point search method to find a point L on the line segment EF, make a parallel line of DE through point L and intersect CD at K, extend KL to point I, so that the length of KI is equal to ε, make a parallel line of EF through I and intersect FG at J, take quadrilateral KLED as the added part, and take quadrilateral FLIJ as the deleted part. When the difference in area between quadrilateral KLED and quadrilateral FLIJ is the smallest, the positions of points K, L, I, and J can be determined, and points D, E, and F are shifted to points K, I, and J respectively, and ABCDEFGH is simplified to ABCKIJGH.

[0065] The second category: the top priority is to simplify the vertex to a right angle, and there is no right angle in the adjacent points

[0066] When the polygon is of the second type, a point is found on the front adjacent side and the back adjacent side through the moving point search method to make a parallel line to the straight line where the front vertex and the back vertex are located, and the area between the front adjacent side, the back adjacent side and the parallel lines is used as the added part or the deleted part, and the area between the parallel line, the front adjacent side, and the first adjacent side and the area between the parallel line, the back adjacent side, and the second adjacent side is used as the deleted part or the added part. The position of the moving point is determined based on the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and the polygon is simplified based on the determined position of the moving point; wherein, the deleted part is the part where the highest priority simplification vertex is a convex point, and the added part is the part where the highest priority simplification vertex is a concave point.

[0067] According to the convexity of the neighboring points of the most prioritized simplified vertex, it can be divided into convex-concave-convex type and concave-convex-convex type, such as Figure 8(a) and 8(b) As shown in the figure, the two types of simplification methods are consistent. Point C is the most prioritized vertex to be simplified and is a right angle. Points B and D are non-right angles. B is the front vertex, D is the back vertex, BC is the front adjacent edge, CD is the back adjacent edge, AB is the first adjacent edge, and DE is the second adjacent edge. Use the moving point search method to find a point F and G on BC and CD respectively, so that FG is parallel to BD. Extend FG and GF to intersect ED and AB at H and I respectively. In Figure 8(a), triangle FCG is used as the added part, and triangles IBF and GHD are used as the deleted parts. In Figure 8(b), triangle FCG is used as the deleted part, and triangles IBF and GHD are used as the added part. When the difference between the area of ​​triangle FCG and the sum of the areas of triangles IBF and GHD is the smallest, determine the positions of points F, G, H, and I, then shift points B and D to points I and H respectively, delete point C, and simplify ABCDE to AIHE.

[0068] The third category: The top priority is to simplify the vertex that is not a right angle, and there is a right angle in the adjacent vertex

[0069] When the polygon is of the third type, the edge formed by the most prioritized simplified vertex and the right-angled adjacent point is taken as the right-angled edge, the edge formed by the most prioritized simplified vertex and the non-right-angled adjacent point is taken as the hypotenuse, and the adjacent edge of the hypotenuse that passes through the non-right-angled adjacent point is taken as the adjacent edge of the hypotenuse;

[0070] Find a point on the hypotenuse by moving the point-finding method, draw a perpendicular line to the right-angled side through the point, extend the perpendicular line in the direction of the side adjacent to the hypotenuse, make the length of the extended perpendicular line equal to the distance from the most prioritized simplified vertex to the side adjacent to the hypotenuse, take the area between the perpendicular line, the hypotenuse, and the right-angled side as the deleted part or the added part, take the area between the perpendicular line, the hypotenuse, and the side adjacent to the hypotenuse as the added part or the deleted part, determine the position of the moving point based on the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and simplify the polygon based on the determined position of the moving point. Among them, when the highest priority simplified vertex is a concave point and an acute angle or a convex point and an obtuse angle, the deleted part is the part where the non-right angle adjacent points are located, and the added part is the part where the highest priority simplified vertex is located; when the highest priority simplified vertex is a concave point and an obtuse angle or a convex point and an acute angle, the deleted part is the part where the highest priority simplified vertex is located, and the added part is the part where the non-right angle adjacent points are located; when the highest priority simplified vertex is a concave point, the highest priority simplified vertex is an acute angle or an obtuse angle, which means that the external angle of the highest priority simplified vertex in the polygon is an acute angle or an obtuse angle; when the highest priority simplified vertex is a convex point, the highest priority simplified vertex is an acute angle or an obtuse angle, which means that the internal angle of the highest priority simplified vertex in the polygon is an acute angle or an obtuse angle.

[0071] According to the convexity of the most prioritized vertices and neighboring points, it can be divided into convex-concave-convex type, convex-convex-convex type, and convex-convex-concave type, such as Figure 9(a) , 9(b) As shown in Figure 9(c), the simplification methods of these three types are consistent. Point B is the most prioritized vertex for non-right angle simplification, point A is a right angle vertex, point C is a non-right angle vertex, AB is a right angle side, and BC is a hypotenuse. Use the moving point search method to find a point G on the line segment BC and make a perpendicular line to AB intersecting AB at E. Let the distance from point B to line segment CD be Distance_CD, extend EG to F, and make the length of EF equal to Distance_CD. Use the moving point search method to determine the position of point G on BC. When the area difference between triangle BEG and triangle CFG is the smallest, determine the positions of points E and F, then shift point B to point E, add point F, and simplify polygonal line segment ABCD to AEFCD. Figure 9(a) , 9(b) In Figure 9(c), AB and CD are parallel, points C and F are collinear, and point C is a right-angle vertex. The right-angle vertex is deleted during the cyclic simplification process. If smaller detail vertices are generated during the simplification process, due to the change of the right-angle type of the most prioritized vertex, as shown in the third figure from the left in Figure 9(c), the new polygon generated after the third type of simplification meets the requirements of the first type of simplification, and will be simplified according to the first type in the next progressive simplification: after simplification, point F is the most prioritized vertex, and points E, F, and C are right angles, so it will be simplified according to the first type of "convex-convex-concave" type, and the polygon line segment AEFCD will be simplified to AGH.

[0072] Category 4: The top priority simplification vertex is non-right angle, and there is no right angle in the adjacent points

[0073] When the polygon is of the fourth type, the shape and structure of the building are often irregular. In order to keep its contour features and area size as much as possible, the present invention adopts the area comparison simplification method. The idea is to shift the most prioritized simplified vertex to different positions, compare the area changes of the polygon after the shift, and take the position with the smallest area change as the shifted position of the most prioritized simplified vertex; in order to keep the shape features and right angles of the building, the shifted position is generally constructed by making a perpendicular line or an intersection point. The specific simplification process is as follows: make a perpendicular line of the rear adjacent side through the front vertex and intersect with the rear adjacent side at the first point, extend the first adjacent side and intersect with the rear adjacent side at the second point, make a perpendicular line of the front adjacent side through the rear vertex and intersect with the front adjacent side at the third point, extend the second adjacent side and intersect with the front adjacent side at the fourth point, calculate the area formed by the first point, the second point and the front adjacent side respectively, calculate the area formed by the third point, the fourth point and the rear adjacent side respectively, and the area of ​​the triangle formed by the shortest side and the rear adjacent side, find the point with the smallest corresponding area, move the most prioritized simplified vertex to the point, and realize the simplification of the polygon.

[0074] like Fig.10As shown, line segment ABCDE is part of the building polygon, B, C, and D are all non-right angles, B is the front vertex, D is the back vertex, BC is the front adjacent side, CD is the back adjacent side, AB is the first adjacent side, and DE is the second adjacent side. Draw perpendicular lines through points B and D to CD and BC, intersecting at G and I respectively, and extend AB and ED to intersect CD and BC at F and H respectively; for the top priority simplified vertex C, there are generally 5 shift positions to choose from: G, F, H, I, and D (that is, point C is deleted). When the constructed shift position exists, the change area corresponding to each shift position is calculated respectively. The change area corresponding to point G is the area S△CBG of triangle CBG, recorded as Area_G; similarly, the change areas corresponding to points F, I, H, and D are Area_F = S△CBF, Area_I = S△CDI, Area_H = S△CDH, and Area_D = S△CBD. If Area_G is the smallest, such as Fig.10 As shown in the simplified method in the left figure, point C is shifted to point G, ABCDE is simplified to ABGDE, and the same is true for point I and point G; if Area_F is the smallest, such as Fig.10 As shown in the simplified method in the middle figure, point C is shifted to point F, ABCDE is simplified to AFDE, and the same is true for points H and F; if Area_D is the smallest, such as Fig.10 As shown in the simplification method in the middle right figure, point C is deleted and ABCDE is simplified to ABDE.

[0075] In addition, when simplifying the above four types of polygons, since vertex position accuracy is usually very important in large-scale maps, in order to ensure point accuracy and simplification quality and avoid sudden changes in the shape of building outlines due to large vertex displacement, it is necessary to control the displacement of vertices during the simplification process. The present invention controls displacement by establishing a "displaced vertex pair" between the vertices before and after simplification. A shifted vertex pair is two vertices that have a corresponding displacement relationship during simplification. Taking the special case in the second category as an example, Fig.11 As shown, line segment ABCDE is part of the building polygon, where point C is the optimized right-angle vertex, and B and D are non-right angles. According to the simplification method of the second type of polygon, Fig.11 As shown in the middle left figure, point D is shifted to point H, and point B is shifted to point I, then point D and point H, point B and point I respectively constitute a "shifted vertex pair". The size of the position deviation between the "shifted vertex pairs" reflects the change in position accuracy before and after simplification. When line segment DE is approximately parallel to line segment DB, the shift distance between point H and point D will be too large, which is not conducive to maintaining the shape features. The present invention controls the shifting based on the minimum visible length threshold, that is, when the distance between the two vertices in the "shifted vertex pair" is greater than the minimum visible length threshold, as shown in FIG. Fig.11As shown in the middle right figure, draw a circle with point D as the center and ε as the radius, which intersects DH at H'. Then shift point D to H' and simplify the contour ABCDE to AIH'E.

[0076] By using the above method, various types of polygons are simplified, and flat corners are removed during the simplification process to avoid data redundancy and reduce memory usage. The method of the present invention can realize the simplification of different types of polygons, better maintain the polygon outline features and right-angle features, ensure the minimum area change before and after simplification, is suitable for the simplification of various polygons, and can meet the requirements of large and medium scale maps for building simplification.

[0077] Device Example:

[0078] The device proposed in this embodiment includes a processor and a memory, wherein a computer program that can be run on the processor is stored in the memory, and the processor implements the method of the above method embodiment when executing the computer program. That is to say, the method in the above method embodiment should be understood as a process of a method for gradually simplifying planar residential elements that can be implemented by computer program instructions. These computer program instructions can be provided to the processor, so that the processor executes these instructions to generate functions specified by the above method flow.

[0079] The processor referred to in this embodiment refers to a processing device such as a microprocessor MCU or a programmable logic device FPGA; the memory referred to in this embodiment includes a physical device for storing information, which usually digitizes the information and then stores it in a medium using electrical, magnetic or optical methods. For example: various memories that use electrical energy to store information, such as RAM, ROM, etc.; various memories that use magnetic energy to store information, such as hard disks, floppy disks, magnetic tapes, magnetic core memories, magnetic bubble memories, and U disks; various memories that use optical methods to store information, such as CDs or DVDs. Of course, there are other types of memories, such as quantum memories, graphene memories, etc.

[0080] The device is composed of the above-mentioned memory, processor and computer program, and the processor executes corresponding program instructions in the computer to achieve the above-mentioned. The processor can be equipped with various operating systems, such as Windows operating system, Linux system, Android, iOS system, etc. As another embodiment, the device can also include a display, and the display is used to display the result of polygon simplification for reference by the staff.

Claims

1. A method for gradually simplifying planar residential area elements taking into account structural characteristics, characterized in that: The method comprises the following steps: 1) Obtain the polygon data of the target area’s residential area, including the number of polygon vertices, vertex coordinates, and the length of each side; 2) judging whether the polygon simplification condition is met according to the number of polygon vertices and the length of each side of the polygon, wherein the polygon simplification condition is: the number of polygon vertices is greater than a set number threshold and the length of the shortest side of the polygon is less than a set minimum visible length threshold; 3) When the polygon simplification conditions are met, find the shortest side of the polygon, determine the structural area of ​​the vertex corresponding to the shortest side, and take the vertex with the smallest corresponding structural area as the top priority simplification vertex of the polygon; and find the two adjacent points of the top priority simplification vertex; where the vertex structural area is the area of ​​the parallelogram formed based on the two adjacent sides of the vertex; 4) Classify the polygons according to the angles of the most prioritized simplified vertex and its neighboring points, and simplify them using the corresponding simplification method according to the category to which the polygon belongs, so that the difference between the area of ​​the simplified polygon and the area of ​​the polygon before simplification is minimized or the increased area of ​​the simplified polygon is less than or equal to 10% of the area of ​​the polygon before simplification, and obtain the simplified polygon; determine again whether the simplified polygon meets the polygon simplification conditions; when the polygon simplification conditions are met, continue to simplify the simplified polygon until the number of vertices in the simplified polygon is less than or equal to the set threshold or the shortest side length in the simplified polygon is greater than the set minimum visible length threshold; In step 4), the polygons are divided into the following four types: the first type is that the top priority simplification vertex is a right angle, and there is a right angle in the adjacent points; the second type is that the top priority simplification vertex is a right angle, and there is no right angle in the adjacent points; the third type is that the top priority simplification vertex is a non-right angle, and there is a right angle in the adjacent points; the fourth type is that the top priority simplification vertex is a non-right angle, and there is no right angle in the adjacent points; According to the connection order of polygon vertices, the adjacent point connected counterclockwise to the most prioritized simplified vertex is taken as the front vertex, the adjacent point connected clockwise to the most prioritized simplified vertex is taken as the back vertex, the edge formed by the most prioritized simplified vertex and the front vertex is taken as the front adjacent edge, the edge formed by the most prioritized simplified vertex and the back vertex is taken as the back adjacent edge, the adjacent edge connected counterclockwise to the front adjacent edge is taken as the first adjacent edge, and the edge connected clockwise to the back adjacent edge is taken as the second adjacent edge; when the polygon belongs to the first category, it is divided into the same concavity and convexity type of three points, different concavity and convexity type of adjacent points, and the same concavity and convexity type of adjacent points according to the concavity and convexity of the most prioritized simplified vertex and the front and back vertices; When the three-point concavity and convexity of the optimized simplified vertex and its adjacent points are the same, a point is found on the front adjacent side of the polygon as a parallel line to the rear adjacent side, and the added part and / or deleted part of the polygon is determined according to the intersection of the parallel line with the first adjacent side or the second adjacent side, thereby achieving simplification; the first adjacent side is adjacent to the front adjacent side, and the second adjacent side is adjacent to the rear adjacent side; When the concavity and convexity of adjacent points are different, find a point on the rear adjacent side to make a parallel line between the front adjacent side and the second adjacent side, and determine the added and deleted parts according to the area between the parallel line and the front adjacent side and the second adjacent side, so as to achieve simplification; When the concavity and convexity of adjacent points are the same, find a point on the front adjacent edge and the back adjacent edge to make a parallel line between the first adjacent edge and the second adjacent edge, and determine the added and deleted parts according to the areas between the two parallel lines and the front and back adjacent edges and the first and second adjacent edges, so as to achieve simplification; When the polygon belongs to the second category, find a point on the front and back adjacent sides to make a parallel line to the front and back vertices, and determine the addition and deletion parts based on the area between the parallel lines and the front and back adjacent sides, so as to achieve simplification; When the polygon belongs to the third category, find a point on the hypotenuse where the optimal simplification point is located as a perpendicular line to the right-angle side where the simplification point is located, and determine the addition and deletion parts based on the area between the perpendicular line and the hypotenuse and the right-angle side, thereby achieving simplification; When the polygon belongs to the fourth category, draw perpendicular lines to the rear and front adjacent sides through the front and rear vertices respectively, compare the areas enclosed by the perpendicular lines and the front and rear adjacent sides, and achieve simplification based on the area with the smallest area change.

2. The method for gradually simplifying planar residential area elements taking into account structural characteristics according to claim 1, characterized in that: When the three points of the most prioritized simplified vertex and its adjacent points have the same concavity and convexity and are all convex, find a point on the front adjacent side of the polygon as a parallel line of the rear adjacent side by using the moving point search method, and extend the parallel line to find the intersection with the extension line of the first adjacent side, and take the area between the parallel line and the rear adjacent side in the polygon as the deleted part, and take the area formed by the intersection, the front vertex and the moving point on the front adjacent side as the added part, determine the position of the moving point according to the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and simplify the polygon according to the determined moving point position; wherein, the rear vertex is a right angle, and the front vertex is a non-right angle; When the three points of the most prioritized simplified vertex and its neighboring points have the same concavity and convexity and are all concave, draw a parallel line to the front adjacent side through the rear vertex, and take the area between the front adjacent side and the parallel line to the front adjacent side as the added part. When the area of ​​the added part is less than or equal to 10% of the area of ​​the polygon before simplification, determine the intersection point of the parallel line to the front adjacent side and the first adjacent side, and simplify the polygon according to the determined intersection point. When the concavity and convexity of the adjacent points are different, find the adjacent points that are different from the concavity and convexity of the most prioritized simplified vertex, use the edge formed by the most prioritized simplified vertex and the adjacent points that are different from the concavity and convexity as the simplified edge, find a point on the simplified edge by the moving point search method, draw parallel lines of two adjacent edges adjacent to the simplified edge, use the area between one of the adjacent edges and its parallel lines as the added part or the deleted part, use the area between the other adjacent edge and its parallel lines as the deleted part or the added part, determine the position of the moving point according to the minimum difference between the deleted area and the added area, and simplify the polygon according to the determined position of the moving point; wherein the deleted part is the part where the adjacent points of the convex point are located, and the added part is the part where the adjacent points of the concave point are located; When the concavity and convexity of adjacent points are the same, a point is found on the front adjacent side to be a parallel line of the first adjacent side, and a point is found on the back adjacent side to be a parallel line of the second adjacent side by the moving point finding method, so that the ratio of the length of the line segment formed by the intersection point of the most prioritized simplified vertex and the front adjacent side to the length of the line segment formed by the intersection point of the most prioritized simplified vertex and the back adjacent side is equal to the ratio of the length of the front adjacent side to the length of the back adjacent side, and the area between the parallel line of the first adjacent side and the first adjacent side and the area between the parallel line of the second adjacent side and the second adjacent side in the polygon is taken as the deleted part or the added part, and the area between the front adjacent side, the back adjacent side, the parallel line of the first adjacent side, and the parallel line of the second adjacent side is taken as the added part or the deleted part, and the position of the moving point is determined according to the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and the polygon is simplified according to the determined position of the moving point; wherein, the deleted part is the part where the convex point is located, and the added part is the part where the concave point is located.

3. The method for gradually simplifying planar residential area elements taking into account structural characteristics according to claim 1, characterized in that: When the polygon is of the first type and the structural area of ​​the most prioritized simplified vertex is greater than the set area threshold, a point is found on the rear adjacent edge through the moving point search method to make a parallel line segment of the front adjacent edge and intersect with the first adjacent edge. The intersection point is used as a vertex of the parallel line, so that the parallel line segment is equal to the minimum visible length threshold, and a parallel line of the rear adjacent edge is made through another vertex of the parallel line segment to intersect the second adjacent edge at a point; the area formed by the front adjacent edge and the parallel line of the front adjacent edge is used as the deleted part or the added part, and the area where the parallel line of the rear adjacent edge and the rear adjacent edge are located is used as the added part or the deleted part, and the position of the moving point is determined according to the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and the polygon is simplified according to the determined moving point position; wherein, the deleted part is the part where the adjacent points of the convex point are located, and the added part is the part where the adjacent points of the concave point are located.

4. The method for gradually simplifying planar residential area elements taking into account structural characteristics according to claim 1, characterized in that: When the polygon is of the second type, a point is found on the front adjacent side and the back adjacent side through the moving point search method to make a parallel line to the straight line where the front vertex and the back vertex are located, and the area between the front adjacent side, the back adjacent side and the parallel lines is used as the added part or the deleted part, and the area between the parallel line, the front adjacent side, and the first adjacent side and the area between the parallel line, the back adjacent side, and the second adjacent side is used as the deleted part or the added part. The position of the moving point is determined based on the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and the polygon is simplified based on the determined position of the moving point; wherein, the deleted part is the part where the highest priority simplification vertex is a convex point, and the added part is the part where the highest priority simplification vertex is a concave point.

5. The method for gradually simplifying planar residential area elements taking into account structural characteristics according to claim 1, characterized in that: When the polygon is of the third type, the edge formed by the most prioritized simplified vertex and the right-angled adjacent point is taken as the right-angled edge, the edge formed by the most prioritized simplified vertex and the non-right-angled adjacent point is taken as the hypotenuse, and the adjacent edge of the hypotenuse that passes through the non-right-angled adjacent point is taken as the adjacent edge of the hypotenuse; A point is found on the hypotenuse by a moving point search method, a perpendicular line to the right-angled side is drawn through the point, the perpendicular line is extended in the direction of the side adjacent to the hypotenuse, so that the length of the extended perpendicular line is equal to the distance from the highest priority simplified vertex to the side adjacent to the hypotenuse, the area between the perpendicular line, the hypotenuse and the right-angled side is used as a deleted part or an added part, the area between the perpendicular line, the hypotenuse and the side adjacent to the hypotenuse is used as an added part or a deleted part, the position of the moving point is determined according to the minimum difference between the area of ​​the deleted part and the area of ​​the added part, and the polygon is simplified according to the determined position of the moving point; wherein, when the highest priority simplified vertex is a concave point and an acute angle or a convex point and an obtuse angle, the deleted part is the part where the non-right-angled adjacent point is located, and the added part is the part where the highest priority simplified vertex is located; when the highest priority simplified vertex is a concave point and an obtuse angle or a convex point and an acute angle, the deleted part is the part where the highest priority simplified vertex is located, and the added part is the part where the non-right-angled adjacent point is located.

6. The method for gradually simplifying planar residential area elements taking into account structural characteristics according to claim 1, characterized in that: When the polygon is of the fourth type, the area comparison simplification method is used. A perpendicular line to the rear adjacent side is drawn through the front vertex and intersects with the rear adjacent side at the first point. The first adjacent side and the rear adjacent side are extended to intersect at the second point. A perpendicular line to the front adjacent side is drawn through the rear vertex and intersects with the front adjacent side at the third point. The second adjacent side and the front adjacent side are extended to intersect at the fourth point. The areas formed by the first point, the second point and the front adjacent side are calculated respectively. The areas formed by the third point, the fourth point and the rear adjacent side and the area of ​​the triangle formed by the front adjacent side and the rear adjacent side are calculated respectively. The point with the smallest corresponding area is found, and the highest priority simplified vertex is moved to this point to achieve simplification of the polygon.

7. The method for gradually simplifying planar residential area elements taking into account structural characteristics according to claim 1, characterized in that: In step 4), when the distance between the vertex and the corresponding moving point is greater than the minimum visible length threshold, a new moving point whose distance from the vertex is equal to the minimum visible length threshold is found on the straight line where the vertex and the moving point are located, and the vertex is moved to the new moving point.

8. The method for gradually simplifying planar residential area elements taking into account structural characteristics according to claim 1, characterized in that: In the step 1) and the simplification process, it is also necessary to remove the flat vertices in the polygon.

9. A device for gradually simplifying planar residential area elements taking into account structural characteristics, characterized in that: The device comprises a processor and a memory, wherein the processor executes a computer program stored in the memory to implement the method for gradually simplifying planar residential area elements as described in any one of claims 1 to 8.

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