CN110619134B - Integrated detection and repair method for solving problem of flying spot and spot density of road network data - Google Patents

Abstract

The invention relates to the technical field of highway informatization, and discloses an integrated detection and repair method for solving the problems of flying spot and spot density of road network data, which comprises the following steps: data preparation, unifying data formats, performing preliminary detection on the data, and cleaning and warehousing the data; detecting and repairing a long straight line; short straight line, flying spot detection and preliminary processing, namely calculating the distance between all adjacent nodes in a road section and the angle of an included angle formed by all adjacent three nodes respectively, wherein the short straight line is judged if the distance is smaller than a threshold value, only the previous point is reserved if the distance is 0, the flying spot is judged if the angle is smaller than the threshold value, and the flying spot is directly deleted if the angle is too small; the short straight line and the flying spot are integrally processed, the short straight line needs to be comprehensively solved with the flying spot, and the problem of the short straight line is preferentially solved under the condition that the short straight line and the flying spot cannot be considered; and eliminating the problem of residual flying spots. The invention obviously improves the efficiency of line-shaped detection and repair of the highway network data, and has higher accuracy and normalization.

Description

Integrated detection and repair method for solving problem of flying spot and spot density of road network data

Technical Field

The invention relates to the technical field of highway informatization, in particular to an integrated detection and repair method for solving the problem of flying spot and spot density of road network data.

Background

Rural highway construction is an important support and key fulcrum of the rural vibration strategy. In order to accurately grasp the development condition, construction requirement and construction progress of rural highways, the transportation department organizations have conducted investigation work of national rural highway access conditions since 2005, acquire rural highway access conditions in rural areas (towns) and villages by using GPS technology, and collect spatial data and attribute data of rural highways. In 2007, the transportation unit establishes an annual update system of rural highway base data and electronic maps, and requests each province to report the rural highway base data and the annual update data to the transportation unit, and the transportation unit performs quality inspection on the data in a unified manner. Because of drift of the GPS signal, there are many uncontrollable factors in the manual acquisition process, the GPS trajectory data often inevitably has some problems in alignment, the most typical of which include flying spot, long straight line and short straight line problems. In order to practically ensure the quality of rural highway basic data, the linear problems existing in the highway network must be detected and repaired. At present, the detection of the dot density and flying dot problems has been fully automated, but the repair of the problems is mainly dependent on manual editing, the efficiency is low, and the quality is difficult to be ensured.

Disclosure of Invention

The invention aims to provide an integrated detection and repair method for solving the problems of flying spot and spot density of road network data, which has the characteristics of clear thought, clear steps, precise algorithm, small linear change and high operation efficiency, so as to solve the problems in the background technology.

In order to achieve the above purpose, the present invention provides the following technical solutions:

the integrated detection and repair method for solving the problem of the flying spot and the spot density of the road network data comprises the following steps:

s1: data preparation, including unifying data formats, performing preliminary inspection on the data, automatically detecting road data with serious problems, performing manual editing, and cleaning and warehousing the data basically qualified in the preliminary inspection;

s2: detecting and repairing a long straight line, calculating the distance between adjacent nodes in a road section, and judging the long straight line if the distance is greater than a threshold value; the repairing method is that starting from the starting point of a long straight line, taking points along the long straight line according to a fixed distance as newly added nodes of a road section until the end point of the long straight line, and if the distance of the last section is smaller than a short straight line threshold value, merging the section into the last section;

s3: short straight line, flying spot detection and preliminary repair, namely calculating the distance between two adjacent nodes in a road section respectively, judging the distance to be a short straight line if the distance is smaller than a threshold value, only keeping the previous point if the distance is 0, calculating the angle of an included angle formed by the adjacent three nodes in the road section, judging the middle node to be a flying spot if the angle is smaller than the threshold value, deleting the flying spot if the angle is too small, and carrying out the flying spot detection again, and carrying out iterative processing until the flying spot with the too small angle does not exist;

s4: short straight line and flying spot integrated restoration, searching nodes meeting the conditions of the flying spot and the short straight line simultaneously along the advancing direction of the road section within a certain distance range as nodes of the road section, and searching the nodes meeting the conditions of the short straight line as the nodes of the road section if the nodes can not be considered;

s5: and (3) detecting and repairing the residual flying spot, respectively taking the points with certain length from the flying spot on the two sides of the residual flying spot, replacing the flying spot with the two newly acquired nodes, and performing the flying spot detection again after the processing is finished, and performing iterative processing until the flying spot does not exist in the road section.

Further, in order to facilitate the organization and management of data, S1 imports the road network data stored in shape format into Oracle and SQL Server databases through ArcSDE.

Further, the flying spot deleting angle in the step 3 is smaller than 20 degrees.

Further, in S4, a new point sequence array is established for each section of polyline, newly selected nodes are added into the array, and after the point selection is finished, new polyline is formed according to the array to replace the original polyline.

Further, first, adding the first node point1 of the polyline into the array as a first node, and then selecting a second node of the array, wherein the selection of the second node is completely based on the distance from the first node, and the specific selection mode is as follows:

1) If the distance between the next node point2 of the polyline and the point1 is larger than the short linear threshold, directly adding the point2 into the array to serve as a second node, and if the distance between the point2 and the point1 is smaller than or equal to the short linear threshold, turning to the next step;

2) And marking the next node of the point2 as the point3 on the polyline, searching for a point meeting the condition on a line segment formed by the point2 and the point3 if the distance between the point1 and the point3 is larger than a short straight line threshold value, and continuing to transfer the step into the step by taking the point3 as a new point2 if the distance between the point1 and the point3 is smaller than the short straight line threshold value.

Further, selecting a third and subsequent node of the array until the last node of the polyline, wherein the specific selection mode of the node is as follows:

1) Selecting the penultimate point of the array as point1, the penultimate point of the array as point2, and the next node of the polyline as point3, if the distance between the point3 and the point2 is larger than a short linear threshold value, and the angle formed by the point1, the point2 and the point3 is larger than an angle threshold value, adding the point3 into the array, and if the point3 does not meet the condition, turning to the next step;

2) Setting the next point of the point3 on the polyline as the point4, setting the line segment formed by the point3 and the point4 as the polylineTmp, selecting a point Add according to a step length of 0.1 meter from the point3 on the polylineTmp, adding the point Add into the array if the point Add meets the conditions of a flying point and a short straight line, and setting the point4 as a new point3 if the distance between the point4 and the point2 is smaller than raidus until the point4 does not meet the conditions of the flying point and the short straight line at the same time, repeating the step, and switching to the next step if the distance between the point Add and the point2 is larger than radius;

3) Starting from the last point added to the array, the next node of the polyline is designated as point3. If the distance between the point3 and the point2 is larger than the short straight line threshold value, adding the point3 into the array, otherwise, starting from the point3, selecting a point Add in a step length of 0.1 meter along the advancing direction of the polyline, and if the distance between the point Add and the point2 is larger than the short straight line threshold value, adding the point Add into the array;

4) When the last point of the polyline is selected, the point is marked as point2, the last point of the array is marked as point1, if the distance between the point2 and the point1 is smaller than a short straight line threshold value, the point1 is removed from the array, then the point2 is added into the array, and if the distance between the point2 and the point1 is larger than the short straight line threshold value, the point2 is directly added into the array, and a new line shape formed by the array is replaced by the original line shape.

Compared with the prior art, the invention has the beneficial effects that: the invention provides an integrated detection and repair method for solving the problems of flying spots and dot density of road network data, which automatically detects road section data with serious linear problems or format problems and carries out manual editing, then detects and repairs long straight lines in the road section, then carries out short straight lines, flying spot detection and preliminary repair, then selects nodes of the road section on the premise of comprehensively considering the problems of the flying spots and the short straight lines, and if the problems of the flying spots and the short straight lines cannot be considered, the problems of the short straight lines are solved preferentially, the problem of the short straight lines is solved completely in the step is ensured, finally, for the residual flying spots, the points with fixed lengths on two sides from the flying spots are selected to replace the original flying spots as new nodes of the road section, and iterative processing is carried out until the flying spots are eliminated completely. The invention can process the linear problems of point density, flying spot and the like in the highway network according to the relative requirements of traffic management departments on highway alignment, and the invention remarkably improves the efficiency of highway network data linear detection and repair by utilizing the space information technology and has higher accuracy and standardization.

Drawings

FIG. 1 is a flow chart of the present invention;

FIG. 2 is a schematic diagram of a flying spot computing process according to the present invention;

FIG. 3 is a schematic diagram of a second point selection process of the road segment according to the present invention;

FIG. 4 is a schematic diagram of a third and subsequent point selection process for a road segment according to the present invention;

fig. 5 is a schematic diagram of the process of eliminating the residual flying spot in the road segment of the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

Referring to fig. 1, the integrated detection and repair method for solving the problem of flying spot and spot density of road network data comprises the following steps:

step 1: data preparation:

the main content of the data preparation comprises a unified data format, the data is subjected to preliminary inspection, road data with serious problems (such as the same coordinates of all nodes in a road section and the data with self-intersecting, self-weighing and other topological problems in a line shape) are automatically detected, and the data with basically qualified preliminary inspection are subjected to manual editing, and are cleaned and put in storage; firstly, the road network data is initially checked, the road data with obvious problems are removed, for example, the coordinates of all nodes in a road section are the same, the topology check is carried out on the data, and the road section data with topology errors such as self-intersection, self-gravity and the like are found out.

Then, in order to facilitate the organization and management of data, the road network data stored in the SHAPE format is imported into databases such as Oracle and SQL Server through ArcSDE, after the data is imported, the attribute information of the road network is stored in the corresponding attribute field in the database, and the space information is stored in the SHAPE field. For ease of calculation, the SHAPE type is set to Geometry, and the spatial coordinate system selects a geographic coordinate system, such as: WGS84 coordinate system or CGCS2000 coordinate system.

Step 2: long straight line problem detection and repair:

too small a dot density may be a long straight line problem, i.e., the distance between two adjacent nodes is greater than a certain threshold. The detection method of the long straight line comprises the steps of traversing all nodes in a road section in sequence, calculating Euclidean distances between adjacent nodes, and marking the long straight line when the distance exceeds a threshold value. In the process of distance calculation, firstly, a space coordinate system of road network data is required to be converted into a projection coordinate system from a geographic coordinate system, and for a WGS84 coordinate system, general transverse-axis cutterhead projection with a 6-degree band is generally adopted; for the CGCS2000 coordinate system, a gaussian-g projection with 6 degree bands is typically used.

Calculating the distance between adjacent nodes in the road section, and judging the distance as a long straight line if the distance is greater than a threshold value; the repairing method is that starting from the starting point of a long straight line, taking points along the long straight line according to a fixed distance as newly added nodes of a road section until the end point of the long straight line, and if the distance of the last section is smaller than a short straight line threshold value, merging the section into the last section; through the step, the problem of long straight line can be solved, and the problem of new short straight line can not be generated.

Step 3: short straight line and flying spot detection and primary repair:

detection of short lines and flying spots also requires conversion of the spatial coordinate system of the data from a geographic coordinate system to a projection coordinate system. For the road section after projection, firstly calculating the distance between all adjacent nodes in the road section, if the distance is smaller than a specified threshold value, judging the road section as a short straight line, if the distance is 0 m, only reserving the former point, deleting the latter point to eliminate the short straight line with the length of 0 m; and calculating included angle angles formed by all three adjacent nodes in the road section, judging as flying spots if the angles are smaller than a certain threshold value, deleting the flying spots if the angles are smaller than 20 degrees, and performing the flying spot detection again, and performing iterative processing until the flying spots with the angles smaller than the angles do not exist.

Wherein, 1. Angle calculation formula

In the flying spot detection process, actually, the angle of an included angle formed by three adjacent nodes in a road section is calculated, namely the size of an ACB (angle ACB) in fig. 2, and the angle calculation adopts a cosine theorem, namely:

where a is the length of side AC, b is the length of side BC, and c is the length of side AC.

2. Distance and angle calculation efficiency optimization

In general, for each road segment, the distance between all two adjacent nodes and the angle between all three adjacent nodes are calculated, if one road segment has n nodes, the distance calculation (n-1) and the angle calculation (n-2) are needed in total, and the time-consuming operations such as squaring, dividing and the like are involved, a large number of repeated calculations exist, and the calculation efficiency is low. In order to improve the calculation efficiency, a numpy library of python is used to convert multiple numerical calculations into single matrix operations, batch calculation of distances and angles is realized, and the calculation efficiency can be improved by more than hundred times due to the characteristics of numpy in the aspects of memory access mode, CPU cache, vectorization instruction and the like.

Step 4: short straight line and flying spot integrated repair:

the problem of long straight lines has been completely eliminated in step 2, leaving only the problem of short straight lines and flying spots. This step eliminates all short straight line problems but leaves some flying spot problems. The problem of short straight line is to dilute the node, the problem of flying spot is to encrypt the node, the two need to be considered comprehensively, the solution idea of the invention is to search the node meeting the condition of flying spot and short straight line as the node of the road section along the advancing direction of the road section in a certain distance range, if not, the node meeting the condition of short straight line is searched as the node of the road section;

and establishing a new point sequence array for each section of polyline, adding the newly selected nodes into the array, and forming a new polyline according to the array after the point selection is finished to replace the original polyline. First, the first node point1 of the polyline is added to the array as the first node. Then, a second node of the array is selected. The second node is selected based entirely on the distance from the first node. The specific selection mode is as follows:

1) If the distance between the next node point2 of the polyline and the point1 is larger than the short linear threshold, directly adding the point2 into the array to serve as a second node, and if the distance between the point2 and the point1 is smaller than or equal to the short linear threshold, turning to the next step;

2) The next node of point2 on the polyline is denoted as point3, and if the distance between point1 and point3 is greater than the short straight line threshold, a point meeting the condition is found on the line segment formed by point2 and point3, and there must be a point with a distance from point1 equal to the short straight line threshold. As shown in fig. 3, the length of L3 is a short straight-line threshold, the length of L2 can be calculated according to a cosine formula, the length of L1 can be calculated by using the pythagorean theorem, and the distance between A, B, i.e., the length between point2 and a can be calculated to determine the coordinates of point a, and the point a is placed in the array. If the distance between the point1 and the point3 is smaller than the short straight line threshold value, taking the point3 as a new point2, and continuing to transfer to the steps.

Then, the third and subsequent nodes of the array are selected until the last-to-last node of the polyline. And searching a new node which simultaneously meets the conditions of the short straight line and the flying spot in a certain range along the road section, adding the new node into the array, and giving priority to the problem of the short straight line under the condition that the new node cannot simultaneously meet the conditions. The maximum searching range is set as radius, the value of radius cannot be too small or too large, if radius is too small, the modification which can be generated on the line shape is limited, and the flying spot problem is difficult to solve; if radius is too large, the flying spot problem is easy to solve, but the change of the line shape may be too large, so that the detail information of the road section is lost, and the integrity of the information of the road section is damaged, especially in mountain areas, the situation that a sharp curve exists in the road section is likely to be in line with reality, and the modification of the line shape should be more careful. The default value of radius is typically 10 meters, and for roads and highways in land areas with flat topography, radius can be set to be slightly larger, and for roads and rural highways in areas with complex topography, radius value should be relatively smaller. The specific selection mode of the nodes is as follows:

1) Selecting the penultimate point of the array as point1, the penultimate point of the array as point2, and the next node of the polyline as point3, and adding point3 into the array if the distance between point3 and point2 is larger than a short straight line threshold value and the angle of an included angle formed by point1, point2 and point3 is larger than an angle threshold value. If point3 does not meet the condition, go to the next step.

2) As shown in fig. 4, the next point of point3 on the polyline is designated as point4, the line segment formed by point3 and point4 is designated as polylineTmp, and on polylineTmp, from point3, the point pointAdd is selected in a step of 0.1 meter, and if the pointAdd satisfies the flying spot and short straight line conditions, the pointAdd is added to the array. If the flying spot and the short straight line condition are not satisfied at all until point4, and the distance between point4 and point2 is smaller than raidus, then point4 is defined as new point3, and step 2 is repeated. If the distance between the pointAdd and point2 is greater than radius, go to the next step.

3) Starting from the last point added to the array, the next node of the polyline is designated as point3. If the distance between point3 and point2 is greater than the short straight threshold, then point3 is added to the array. Otherwise, point3 is followed by a point add in 0.1 meter step along the forward direction of the polyline, and if the distance between point add and point2 is greater than the short straight line threshold, then point add is added to the array.

Finally, when the last point of the polyline is selected, the point is marked as point2, the last point of the array is marked as point1, if the distance between the point2 and the point1 is smaller than a short straight line threshold value, the point1 is removed from the array, and then the point2 is added into the array. If the distance between point2 and point1 is greater than the short straight line threshold, then point2 is added directly to the array. And replacing the original linear shape with the new linear shape formed by the array.

Step 5: detecting and repairing residual flying spots:

the residual flying spot is needed to be eliminated in a spot encryption mode, and the specific encryption mode is that the two sides of the residual flying spot are respectively taken to be points with a certain distance from the flying spot, the newly acquired two nodes are used for replacing the flying spot, the line shape is modified, the flying spot detection is carried out again after the processing is finished, and the iteration processing is carried out until the flying spot does not exist in the road section. As shown in fig. 5, the specific operation is that the angle BAC is smaller than the threshold value, the point A is the flying spot, and the points E, D are respectively taken on the AB and the AC, so that the distance between AE and AD is equal to the fixed length, and the flying spot can be eliminated by using D, E points instead of the original point A.

The following describes the method according to the present invention by taking road basic data of a certain province as an example: and selecting road network data of certain province in China to carry out linear detection and repair experiments. The road network comprises approximately 14000 road sections, the area of approximately 20 ten thousand square kilometers is covered, the spans of the abscissas and the ordinates are all over 500 kilometers, most situations which can be met in the actual road network are covered, and the practicability and the reliability of the proposed algorithm can be accurately evaluated. The threshold value for the short straight line was set to 3 meters, the threshold value for the long straight line was set to 200 meters, and the threshold value for the flying spot was set to 130 °. Before and after repair, line-shaped detection is carried out on road network data respectively, and the detection results are shown in the following table 1:

TABLE 1

	Number of short straight line problems	Number of long straight line problems	Number of flying spot problems	Total number of line-shaped questions
					Road network data before repair	80896	1526	2203	84625
Repaired road network data	2348	0	0	2348
					Proportion of repair problem	97.1％	100％	100％	97.2％

Before and after repair, the length of the road section is calculated and the length change is counted, and the counted results are shown in table 2:

TABLE 2

Percent of length change	Road segment number	The proportion of the number of road segments to the total number
			>5％	2	0.01％
1％‐3％	40	0.29％
			0.1％‐1％	522	3.75％
<0.1％	13370	95.95％

According to the analysis experimental result, the method provided by the invention solves all the flying spot and long straight line problems on the premise that the line shape is not changed obviously, the number of short straight line problems is also reduced obviously, and the total number of line problems is reduced by 97%.

In the experimental part, the line-shaped detection and repair are carried out by selecting the line-shaped data of the road network in the whole province in China, and the experimental result shows that the method can rapidly detect the line-shaped problem of the road network and repair the line-shaped problem to the greatest extent, and has higher practicability and reliability.

In summary, the method for integrally detecting and repairing the flying spot and the dot density problem of the road network data provided by the invention automatically detects the road section data with serious linear problems or format problems and manually edits, then detects and repairs the long straight line problems in the road section, then detects and primarily repairs the short straight line and the flying spot, then selects the nodes of the road section on the premise of comprehensively considering the flying spot and the short straight line problems, if the problems cannot be considered, the short straight line problems are preferentially considered to be solved, the problem of the short straight line is completely solved in the step, finally, for the residual flying spot, the dot with fixed length between the two sides and the flying spot is selected to replace the original flying spot as a new node of the road section, and the iterative processing is performed until the flying spot is completely eliminated. The invention can process the linear problems of point density, flying spot and the like in the highway network according to the relative requirements of traffic management departments on highway alignment, and the invention remarkably improves the efficiency of highway network data linear detection and repair by utilizing the space information technology and has higher accuracy and standardization.

The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art, who is within the scope of the present invention, should be covered by the protection scope of the present invention by making equivalents and modifications to the technical solution and the inventive concept thereof.

Claims (6)

1. The integrated detection and repair method for solving the problems of flying spot and spot density of road network data is characterized by comprising the following steps:

s1: data preparation, including unifying data formats, performing preliminary inspection on the data, automatically detecting road data with serious problems, performing manual editing, and cleaning and warehousing the data basically qualified in the preliminary inspection;

s2: detecting and repairing a long straight line, calculating the distance between adjacent nodes in a road section, and judging the long straight line if the distance is greater than a threshold value; the repairing method is that starting from the starting point of a long straight line, taking points along the long straight line according to a fixed distance as newly added nodes of a road section until the end point of the long straight line, and if the distance of the last section is smaller than a short straight line threshold value, merging the section into the last section;

s3: short straight line, flying spot detection and preliminary repair, namely calculating the distance between two adjacent nodes in a road section respectively, judging the distance to be a short straight line if the distance is smaller than a threshold value, only keeping the previous point if the distance is 0, calculating the angle of an included angle formed by the adjacent three nodes in the road section, judging the middle node to be a flying spot if the angle is smaller than the threshold value, deleting the flying spot if the angle is too small, and carrying out the flying spot detection again, and carrying out iterative processing until the flying spot with the too small angle does not exist;

s4: short straight line and flying spot integrated restoration, searching nodes meeting the conditions of the flying spot and the short straight line simultaneously along the advancing direction of the road section within a certain distance range as nodes of the road section, and searching the nodes meeting the conditions of the short straight line as the nodes of the road section if the nodes can not be considered;

s5: and (3) detecting and repairing the residual flying spot, respectively taking the points with certain length from the flying spot on the two sides of the residual flying spot, replacing the flying spot with the two newly acquired nodes, and performing the flying spot detection again after the processing is finished, and performing iterative processing until the flying spot does not exist in the road section.

2. The integrated detection and repair method for solving the problem of flying spot and spot density of road network data according to claim 1, wherein S1 is used for conveniently organizing and managing the data, and importing the road network data stored in shape format into Oracle and SQL Server databases through ArcSDE.

3. The integrated detection and repair method for solving the problems of flying spot and spot density of road network data according to claim 1, wherein the angle of flying spot deletion in the step 3 is smaller than 20 °.

4. The integrated detection and repair method for solving the problem of flying spot and dot density of road network data according to claim 1, wherein in S4, a new dot sequence array is established for each road section polyline, newly selected nodes are added into the array, and after the dot selection is finished, new polyline is formed according to the array to replace the original polyline.

5. The integrated detection and repair method for solving the problem of flying spot and dot density of road network data according to claim 4, wherein first, a first node point1 of a polyline is added into an array as a first node, then, a second node of the array is selected, and the selection of the second node is completely based on the distance from the first node, specifically by the following selection modes:

1) If the distance between the next node point2 of the polyline and the point1 is larger than the short linear threshold, directly adding the point2 into the array to serve as a second node, and if the distance between the point2 and the point1 is smaller than or equal to the short linear threshold, turning to the next step;

2) And marking the next node of the point2 as the point3 on the polyline, searching for a point meeting the condition on a line segment formed by the point2 and the point3 if the distance between the point1 and the point3 is larger than a short straight line threshold value, and continuing to transfer the step into the step by taking the point3 as a new point2 if the distance between the point1 and the point3 is smaller than the short straight line threshold value.

6. The integrated detection and repair method for solving the problem of flying spot and dot density of road network data according to claim 4, wherein the method for selecting the third and subsequent nodes of the array until the last node of the polyline is as follows:

1) Selecting the penultimate point of the array as point1, the penultimate point of the array as point2, and the next node of the polyline as point3, if the distance between the point3 and the point2 is larger than a short linear threshold value, and the angle formed by the point1, the point2 and the point3 is larger than an angle threshold value, adding the point3 into the array, and if the point3 does not meet the condition, turning to the next step;

2) Setting the next point of the point3 on the polyline as the point4, setting the line segment formed by the point3 and the point4 as the polylineTmp, selecting a point Add according to a step length of 0.1 meter from the point3 on the polylineTmp, adding the point Add into the array if the point Add meets the conditions of a flying point and a short straight line, and setting the point4 as a new point3 if the distance between the point4 and the point2 is smaller than raidus until the point4 does not meet the conditions of the flying point and the short straight line at the same time, repeating the step, and switching to the next step if the distance between the point Add and the point2 is larger than radius;

3) Starting from the last point added with the array, the next node of the polyline is designated as point3, if the distance between the point3 and the point2 is larger than a short straight line threshold value, adding the point3 into the array, otherwise starting from the point3, selecting a point Add at a step length of 0.1 meter along the advancing direction of the polyline, and if the distance between the point Add and the point2 is larger than the short straight line threshold value, adding the point Add into the array;

4) When the last point of the polyline is selected, the point is marked as point2, the last point of the array is marked as point1, if the distance between the point2 and the point1 is smaller than a short straight line threshold value, the point1 is removed from the array, then the point2 is added into the array, and if the distance between the point2 and the point1 is larger than the short straight line threshold value, the point2 is directly added into the array, and a new line shape formed by the array is replaced by the original line shape.

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