An automatic delineation method and system for delineating a soil contamination surface using clean points

Abstract

The application provides an automatic delineation method and system for surrounding a soil pollution surface with clean points, comprising: obtaining sampling point data; dividing the sampling points into clean points and over-standard points; constructing a Thiessen polygon based on all the sampling points; identifying a Thiessen polygon cell containing over-standard points as a target cell, obtaining clean points in adjacent Thiessen polygon cells having a common edge with the target cell as candidate surrounding surface points; constructing a closed clean surrounding surface from the candidate surrounding surface points; and fusing the closed clean surrounding surfaces according to spatial adjacency to generate a continuous pollution surface domain. The application removes redundant clean points that contribute the least to the contour shaping of over-standard points, and uses a non-adjacent removal rule to avoid the removed points being concentrated on the same side, thereby automatically constructing a closed clean surrounding surface with clean points surrounding over-standard points, without relying on manual intervention, and greatly shortening the time-consuming of pollution range delineation.

Description

Technical Field

[0001] This invention belongs to the field of soil pollution status investigation and analysis technology, and in particular relates to an automatic delineation method and system for surrounding soil pollution surfaces using clean points. Background Technology

[0002] Soil pollution status investigation is a legally mandated prerequisite for the redevelopment and utilization of a land parcel. The accuracy and completeness of the investigation data directly determine the rationality of the land parcel planning and the safety of remediation and utilization. Among the key tasks, clarifying the horizontal distribution range of pollutants is crucial. The investigation unit needs to determine both the horizontal extent and vertical depth of the pollutants to accurately calculate the volume of polluted soil, providing guidance for subsequent soil remediation projects and land development and utilization.

[0003] Currently, management departments and review experts generally recognize and use the manual method of cleaning points around areas exceeding the standard to delineate the contamination range. This method involves selecting clean sampling points around the areas exceeding the standard, constructing quadrilaterals or other closed shapes with these clean points as vertices, and enclosing the areas exceeding the standard within these shapes to define the boundary of the contamination range. Compared with other methods for delineating contamination ranges, this method's delineation logic is more conservative, following the principle of "better too much than too little," and can completely cover all areas exceeding the standard.

[0004] However, the current manual cleaning of areas exceeding pollution standards relies entirely on the experience of practitioners, lacking standardized quantitative mapping. Even on the same site, different technicians often select different cleaning points for the same area exceeding standards, leading to significant differences in the final pollution range mapping results, resulting in poor repeatability and standardization. Furthermore, for complex medium-to-large-sized sites, these sites not only have a large number of sampling points and involve numerous pollutant indicators and complex soil layer divisions, but also require the mapping of a large number of pollution range maps. The manual mapping process is extremely time-consuming, severely slowing down the overall project progress. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention aims to propose an automatic delineation method and system for surrounding soil contamination surfaces using clean points, thereby solving the problems of long time consumption, inconsistent standards, and non-standard drawing in the existing manual clean point encirclement of contaminated surfaces.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows: An automated method for delineating soil contamination surfaces using clean points includes the following steps: Acquire sampling point data, which includes the spatial coordinates of each sampling point and the pollutant concentration detection value; Based on the comparison between the pollutant concentration detection values ​​at each sampling point and the preset risk screening values, the sampling points are divided into clean points and points exceeding the standard. Construct Thiessen polygons based on all sampling points, so that each Thiessen polygon unit contains only one sampling point. Identify the Thiessen polygonal units containing points exceeding the standard as target units, and obtain the cleaning points corresponding to the common edges of the target units as candidate enclosure points; wherein, the common edge refers to the edge shared by the target unit and the adjacent Thiessen polygonal units, and the edge of the target unit that coincides with the site boundary is a non-common edge. When the number of sides of the target unit is less than or equal to 4, a closed clean enclosure is constructed from the candidate enclosure points; when the number of sides of the target unit is greater than 4, according to the length of each common side of the target unit, the common sides are gradually eliminated according to the preset elimination rules until the target unit has 4 sides remaining, and a closed clean enclosure is constructed from the candidate enclosure points corresponding to the common sides of the remaining 4 sides. Each closed clean enclosure is merged according to its spatial adjacency to generate a continuous contaminated area.

[0007] Furthermore, the preset rejection rules specifically include: Extract all common edges of the target unit and obtain the length of each common edge; Sort all common edges in ascending order of length; In the first round of elimination, the shortest common edge among all common edges is selected and eliminated. From the second round onwards, in each round of elimination, the shortest common edge that has not been eliminated and is not adjacent to any eliminated common edge is selected and eliminated. This process is repeated until the target unit has 4 edges remaining.

[0008] Furthermore, when the target unit does not have non-common edges, the step of constructing a closed clean enclosure from the candidate enclosure points is as follows: When the number of edges of the target unit is less than or equal to 4, the candidate enclosure points corresponding to each common edge are connected in sequence to construct a closed clean enclosure. When the number of edges of the target unit is greater than 4, the edges are gradually removed from the common edges according to the preset removal rules until the target unit has 4 edges remaining. The candidate enclosure points corresponding to the remaining 4 common edges are then connected in sequence to construct a closed clean enclosure.

[0009] Furthermore, when the target unit has non-common edges, the step of constructing a closed clean enclosure from the candidate enclosure points is as follows: When the number of sides of the target unit is less than or equal to 4, perpendicular lines are drawn from the candidate enclosure points corresponding to the common side to the site boundary corresponding to the adjacent non-common side. The candidate enclosure points are connected in sequence, and the connection lines between the candidate enclosure points, the perpendicular lines, and the site boundary segments corresponding to the non-common side are used to enclose and form a closed clean enclosure. When the number of edges of the target unit is greater than 4, the edges are gradually removed from the common edges according to the preset removal rules until the target unit has 4 edges remaining. A closed clean enclosure is then constructed in the manner that the number of edges of the target unit is equal to 4.

[0010] Furthermore, when the shape of the site boundary has inflection points, causing a candidate enclosure point to draw a perpendicular line to the site boundary corresponding to its adjacent non-common edge, the foot of the perpendicular cannot fall on the site boundary segment. In this case, the line connecting the candidate enclosure point and the inflection point of the site boundary is used to replace the perpendicular line. The line, the site boundary segment, and the line connecting the candidate enclosure points together form a closed clean enclosure.

[0011] Furthermore, the specific steps for merging the closed clean enclosures according to their spatial adjacency to generate a continuous contaminated area include: Iterate through all closed clean surfaces and determine whether any two closed clean surfaces share a common edge. If two closed clean surfaces share a common edge, delete the common edge and merge the two closed clean surfaces into a single region. Repeat the above judgment and merging operations until there are no more adjacent closed clean enclosures that can be merged, forming a continuous contaminated area.

[0012] Furthermore, when acquiring candidate enclosure points, if the sampling points inside the adjacent Thiessen polygonal units that share a common edge with the target unit are out-of-range points, then the sampling points inside the adjacent Thiessen polygonal units will not be used as candidate enclosure points for the target unit, and the closed clean enclosure will be constructed from the clean points inside the remaining adjacent Thiessen polygonal units.

[0013] Furthermore, the lengths of the common edges of the target unit are obtained in the following way: Under a preset projection coordinate system, the vector line segment data of the Thiessen polygon unit is read, and the length of the vector line segment corresponding to each common edge is calculated.

[0014] An automated delineation system for surrounding contaminated soil surfaces using clean points, for performing the aforementioned automated delineation method for surrounding contaminated soil surfaces using clean points, comprising: The data preprocessing module is used to acquire sampling point data, which includes the spatial coordinates of each sampling point and the pollutant concentration detection value. The sampling point classification module is used to classify sampling points into clean points and points exceeding the standard based on the comparison results between the pollutant concentration detection values ​​of each sampling point and the preset risk screening values. The Thiessen polygon building module is used to construct Thiessen polygons based on all sampling points, so that each Thiessen polygon cell contains only one sampling point. The target unit identification module is used to identify Thiessen polygon units containing excessive points as target units, and to obtain the clean points corresponding to the common edges of the target units as candidate enclosure points. The enclosure construction module is used to construct a closed clean enclosure from the candidate enclosure points when the number of sides of the target unit is less than or equal to 4; when the number of sides of the target unit is greater than 4, it gradually eliminates the common sides according to the length of each common side of the target unit and according to the preset elimination rules until the target unit has 4 sides remaining, and constructs a closed clean enclosure from the candidate enclosure points corresponding to the common sides of the remaining 4 sides. The area fusion module is used to merge each closed clean enclosure according to its spatial adjacency to generate a continuous contaminated area. The mapping module is used to receive the continuous contaminated surface region generated by the surface region fusion module and export the continuous contaminated surface region as a vector file in a preset format.

[0015] Furthermore, the automatic delineation system is deployed on a soil pollution status survey data screening platform, which also includes: The sampling management module is used to upload sampling point files, sampling plan files, and assign sampling tasks; The Android mobile app is used to receive and display information from the sampling management module, and to perform on-site sampling and recording. The data aggregation module is used to generate sampling point data, including spatial coordinates and pollutant concentration detection values, based on the sampling data from the Android mobile device. The benchmarking standard database is used to store national standards, local standards, industry standards, foreign standards and risk screening values. Based on the land use type, pollutant type and soil layer information corresponding to the sampling point, the preset risk screening value of the pollutant concentration detection value corresponding to the sampling point is matched from the benchmarking standard database. The automatic delineation system's data preprocessing module obtains sampling point data from the data aggregation module and preset risk screening values ​​from the benchmark database.

[0016] Compared with existing technologies, the automatic delineation method and system for surrounding soil contamination surfaces using clean points, as described in this invention, have the following advantages: This invention constructs Thiessen polygons using all sampling points, and utilizes the fixed mathematical generation principle of Thiessen polygons to ensure the objectivity, uniqueness, and reproducibility of the processing results. By using whether each Thiessen polygon unit contains out-of-standard points as the criterion, the target unit to be processed is accurately located. By obtaining clean points in adjacent units of the target unit as candidate enclosing points, the core logic of surrounding out-of-standard points with clean points is realized.

[0017] This invention extracts all common edges of the target unit and obtains the length of each common edge. In the first round, the shortest common edge is eliminated. From the second round onwards, the shortest common edge that has not yet been eliminated and is not adjacent to any eliminated common edge is eliminated until only 4 edges remain. Utilizing the spatial geometry principle that the shortest common edge constraint contributes the least to the shaping of the outer contour of the out-of-standard points, redundant clean points that contribute the least to the shaping of the outer contour of the out-of-standard points are eliminated first. At the same time, the non-adjacent elimination rule is used to avoid the eliminated points being concentrated on the same side, so that the remaining clean points are evenly distributed in space around the out-of-standard points. This ensures that the enclosure completely covers the out-of-standard points and does not cause local missing outer contours, while avoiding unnecessary expansion of the enclosure due to the retention of redundant close-range points, thus artificially increasing the contaminated area. This achieves a balance between conservative delineation and precise control.

[0018] Compared to existing methods that involve manually cleaning points to continuously enclose areas exceeding the standard, the delineation results of this method are unique and reproducible, and are not affected by human experience. Compared to the Thiessen polygon method, which directly uses polygon boundaries as pollution boundaries, this method reconstructs quadrilateral enclosures by selecting clean points within adjacent units, thus meeting the review requirements of management departments for the delineation of pollution areas. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the control flow provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of sampling points provided in an embodiment of the present invention (black indicates clean points, and red indicates points exceeding the standard). Figure 3 This is a schematic diagram of the generation of Thiessen polygonal units provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a quadrilateral target unit structure provided in an embodiment of the present invention; Figure 5 for Figure 4 A schematic diagram of the closed clean enclosure structure generated by the quadrilateral target element; Figure 6 This is a schematic diagram of the pentagonal target unit structure provided in an embodiment of the present invention; Figure 7 for Figure 6 A schematic diagram of the closed clean enclosure structure generated by the medium pentagonal target element; Figure 8 This is a schematic diagram of the hexagonal target unit structure provided in an embodiment of the present invention; Figure 9 for Figure 8 A schematic diagram of the closed clean enclosure structure generated by the hexagonal target element; Figure 10 for Figure 8 Schematic diagram of the structure of the hexagonal target cell without removing the shortest side; Figure 11 for Figure 8 A schematic diagram showing the removal of the second-to-last non-adjacent shortest side from the shortest side of the hexagonal target cell; Figure 12 This is a schematic diagram of a closed cleaning enclosure for adjacent points exceeding the standard, provided in an embodiment of the present invention. Figure 13 This is a schematic diagram showing that the target unit provided in this embodiment of the invention is a triangle with one non-common side; Figure 14 This is a schematic diagram showing that the target unit provided in this embodiment of the invention is a quadrilateral with two non-common sides; Figure 15 The target unit provided in this embodiment of the invention is a hexagon with 3 non-common sides.

[0020] Explanation of reference numerals in the attached figures: 1. Cleaning points; 2. Exceeding standards points; 3. Tyson polygonal units; 31. Quadrilateral target units; 32. Pentagonal target units; 33. Hexagonal target units; 4. Closed cleaning enclosure; 5. Site boundaries. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0022] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] like Figures 1 to 15 As shown, an automatic delineation method for surrounding contaminated soil surfaces using clean points includes the following steps: S1. Obtain sampling point data, which includes the spatial coordinates of each sampling point and the pollutant concentration detection value; Specifically, the sampling point data originates from on-site sampling and testing during the soil pollution status investigation. In one implementation scenario, investigators, following the required sampling density according to national guidelines and standards, set up sampling points within the site, collected soil or groundwater samples from each point, and sent them to the laboratory for testing to obtain the corresponding pollutant concentration values ​​for each sampling point. The acquired sampling point data is then entered into a soil pollution status investigation data screening platform for use in subsequent steps.

[0024] S2. Based on the comparison results between the pollutant concentration detection values ​​at each sampling point and the preset risk screening values, the sampling points are divided into clean points and points exceeding the standard. Specifically, sampling points where the pollutant concentration is lower than the preset risk screening value are marked as clean points, and sampling points where the pollutant concentration exceeds the preset risk screening value are marked as exceeding the standard points.

[0025] S3. Construct Thiessen polygons based on all sampling points, so that each Thiessen polygon unit contains only one sampling point. Specifically, based on the algorithm in the JTS Topology Suite database, the spatial coordinates of all sampling points are used as discrete point inputs to draw global Thiessen polygons. Due to the spatial distribution and density of the site locations, the shape and number of sides of each generated Thiessen polygon cell are different, and it can contain polygon cells with triangles, quadrilaterals, pentagons, hexagons, or even higher numbers of sides. There is no uniform side length for each polygon cell, and adjacent cells share common sides.

[0026] S4. Identify the Thiessen polygonal units containing points exceeding the standard as target units, and obtain the cleaning points corresponding to the common edges of the target units as candidate enclosure points; wherein, the common edge refers to the edge shared by the target unit and the adjacent Thiessen polygonal units, and the edge of the target unit that coincides with the site boundary is a non-common edge. Specifically, since each Thiessen polygon cell contains only one sampling point, whether the Thiessen polygon cell is a target cell can be determined by judging whether this sampling point is an out-of-range point. For Thiessen polygon cells that do not contain out-of-range points, the subsequent clean enclosure construction process is not performed. For the target cell, all adjacent Thiessen polygon cells that share a common edge with the target cell are read, the sampling points inside these adjacent cells are extracted, and it is determined whether each sampling point is a clean point. All clean points are used as candidate enclosure points. If a sampling point inside an adjacent cell is also an out-of-range point, then these two out-of-range points are not used as candidate enclosure points for each other, and a closed clean enclosure is constructed using other clean points, such as... Figure 12 As shown.

[0027] S5. When the number of sides of the target unit is less than or equal to 4, a closed clean enclosure is constructed from the candidate enclosure points; when the number of sides of the target unit is greater than 4, according to the length of each common side of the target unit, the common sides are gradually eliminated according to the preset elimination rules until the target unit has 4 sides remaining, and a closed clean enclosure is constructed from the candidate enclosure points corresponding to the common sides of the remaining 4 sides. Specifically, when the number of edges of the target unit is less than or equal to 4, the number of edges can only be 3 or 4.

[0028] S6. Merge each closed clean enclosure according to its spatial adjacency to generate a continuous contaminated area.

[0029] Specifically, each point exceeding the standard generates a corresponding closed clean enclosure according to the above steps. By merging adjacent closed clean enclosures with a common edge, the discrete single-point quadrilateral enclosures are automatically connected into a continuous and unified area of ​​pollution exceeding the standard, eliminating defects such as missing areas, missing breakpoints, and local omissions caused by manual drawing.

[0030] This invention uses Thiessen polygons as the basic tool for spatial discretization. By utilizing the spatial proximity characteristics of Thiessen polygons, the problem of delineating soil contamination surfaces is transformed into a problem of connecting and enclosing polygon vertices (candidate confinement points). By controlling the number of confinement vertices through preset elimination rules, the geometric shape of the closed clean confinement surfaces is ensured to be regular. Through surface fusion, the discrete confinement surfaces are integrated into continuous contaminated surfaces, realizing the automatic conversion from point data to surface results. The entire process is automated, requiring no manual drawing, and significantly reducing the workload of indoor processing in soil contamination surveys.

[0031] In a preferred embodiment of the present invention, the preset rejection rule specifically includes: Extract all common edges of the target unit and obtain the length of each common edge; Sort all common edges in ascending order of length; In the first round of elimination, the shortest common edge among all common edges is selected and eliminated. From the second round onwards, in each round of elimination, the shortest common edge that has not been eliminated and is not adjacent to any eliminated common edge is selected and eliminated. This process is repeated until the target unit has 4 edges remaining.

[0032] Specifically, all common edges are sorted in ascending order of length. For example, if a pentagonal target unit has 5 common edges with lengths of 10m, 8m, 2m, 7m, and 6m, the sorted order would be: 2m, 6m, 7m, 8m, 10m.

[0033] In the first round of elimination, the shortest common edge among all common edges is selected, and the candidate enclosure points corresponding to the shortest common edge are eliminated. Taking the pentagon above as an example, the shortest common edge is 2m long. The clean points in the adjacent units corresponding to the 2m common edge are eliminated, leaving 4 candidate enclosure points. At this point, the requirement of having 4 remaining edges is met, and the elimination ends.

[0034] Starting from the second round, in each round of elimination, the shortest common edge that has not yet been eliminated and is not adjacent to any eliminated common edge is selected, and the candidate enclosing points corresponding to this shortest common edge are eliminated. This process is repeated until only 4 edges remain. Taking a hexagonal target unit as an example, let the lengths of its 6 common edges be: edge 1 = 10m, edge 2 = 8m, edge 3 = 2m, edge 4 = 7m, edge 5 = 6m, and edge 6 = 9m. After sorting, the shortest edge is edge 3 (2m). In the first round, the candidate enclosing points corresponding to edge 3 are eliminated. When entering the second round, it is determined whether the current shortest edge (edge ​​5, 6m) shares an endpoint with the eliminated edge 3. If edge 5 shares an endpoint with edge 3, then edge 5 is adjacent to the eliminated common edge, and edge 5 is skipped. The process continues to determine whether the next short edge (edge ​​4, 7m) shares an endpoint with edge 3. If edge 4 does not share an endpoint with edge 3, then the candidate enclosing points corresponding to edge 4 are eliminated in the second round. At this point, two points have been eliminated, leaving four edges, corresponding to four candidate enclosing points. The elimination process is now complete.

[0035] By using the above-mentioned non-adjacent elimination rule, the defects of the enclosure being too close to the over-standard point and the outer range being uneven caused by continuously eliminating the vertices corresponding to two adjacent short sides are avoided. This ensures that the remaining 4 clean points are evenly distributed in space around the over-standard point, forming a regular quadrilateral enclosure.

[0036] This embodiment achieves the technical effect of automatically selecting the optimal four points from more than four candidate enclosure points by combining the shortest common edge priority elimination and non-adjacent elimination rules. The shortest common edge represents the lowest constraint weight of the adjacent unit corresponding to the common edge on the outer contour of the target unit. Even if this point is removed, the remaining clean points in other directions can still completely enclose the internal excess points. The clean points corresponding to the short common edge have a large overlap in the control range of other clean points in other directions, which are duplicate constraint points. After elimination, there will be no loss of local outer contour range. At the same time, by prohibiting the elimination of points corresponding to two adjacent short edges, the remaining points are prevented from being concentrated on the same side in space, which would lead to enclosure distortion and excess points deviating from the geometric center. Moreover, the quadrilateral enclosure after elimination can keep the excess points stably in the geometric center region of the quadrilateral, which not only ensures the integrity of the conservative delineation, but also avoids unnecessary expansion of the enclosure.

[0037] In a preferred embodiment of the present invention, when the target unit does not have a non-common edge, the step of constructing a closed and clean enclosure from the candidate enclosure points is as follows: When the number of edges of the target unit is less than or equal to 4, the candidate enclosure points corresponding to each common edge are connected in sequence to construct a closed clean enclosure. When the number of edges of the target unit is greater than 4, the edges are gradually removed from the common edges according to the preset removal rules until the target unit has 4 edges remaining. The candidate enclosure points corresponding to the remaining 4 common edges are then connected in sequence to construct a closed clean enclosure.

[0038] Specifically, when the target unit has no non-common edges, the target unit is completely located inside the site, and all its edges are common edges shared with adjacent Thiessen polygon units. In this case, the entire boundary of the closed clean enclosure is formed by the lines connecting the candidate enclosure points, without the need for the site boundary segments to participate in the enclosure, making the construction method the simplest; after polygon removal, it is uniformly a quadrilateral enclosure with a regular shape, which is convenient for subsequent fusion and mapping output.

[0039] In a preferred embodiment of the present invention, when the target unit has a non-common edge, the step of constructing a closed and clean enclosure from the candidate enclosure points is as follows: When the number of sides of the target unit is less than or equal to 4, perpendicular lines are drawn from the candidate enclosure points corresponding to the common side to the site boundary corresponding to the adjacent non-common side. The candidate enclosure points are connected in sequence, and the connection lines between the candidate enclosure points, the perpendicular lines, and the site boundary segments corresponding to the non-common side are used to enclose and form a closed clean enclosure. When the number of edges of the target unit is greater than 4, the edges are gradually removed from the common edges according to the preset removal rules until the target unit has 4 edges remaining. A closed clean enclosure is then constructed in the manner that the number of edges of the target unit is equal to 4.

[0040] Specifically, when a target unit has a non-common edge, it indicates that the target unit is adjacent to the site boundary, and the site boundary itself is a natural enclosing boundary. Drawing perpendicular lines from the candidate enclosure points to the site boundary is to achieve the connection between the candidate enclosure points and the site boundary using the shortest path, so that the closed clean enclosure naturally closes at the site boundary. The selection of the perpendicular line direction ensures a smooth transition and clear geometric relationship between the enclosure boundary and the site boundary.

[0041] If the point exceeding the standard is located at the site boundary, it can be divided into three cases: the first case is that the target unit has one non-common edge, that is, the target unit has one edge that coincides with the site boundary; the second case is that the point exceeding the standard is located at the corner of the site, and the target unit has two non-common edges, that is, the target unit has two edges that coincide with two site boundaries respectively; the third case is the boundary of a special plot, and the target unit has three non-common edges.

[0042] (1) In the first case, when the target unit has one non-common edge, When the number of sides of the target unit is equal to 3, perpendicular lines are drawn from the two candidate enclosure points corresponding to the two common sides to the site boundary corresponding to the non-common sides, connecting the two candidate enclosure points. The line connecting the two candidate enclosure points, the perpendicular lines, and the site boundary constitute a closed clean enclosure; for example... Figure 13 As shown; When the number of sides of the target unit is equal to 4, then draw perpendicular lines from the two candidate enclosure points on both sides to the site boundary corresponding to the non-common side, connect the candidate enclosure points corresponding to the 3 common sides, and construct a closed clean enclosure with the perpendicular lines and the site boundary. When the target unit has 5 or more sides, common edges are removed according to the preset removal rules until the target unit has 4 sides remaining, and a closed clean enclosure is constructed in the manner that the target unit has 4 sides.

[0043] (2) In the second case, when the point exceeding the standard is located at a corner of the site (corner), the target unit has two non-common sides, meaning the target unit is truncated by the bidirectional land boundary, forming a polygon with the land boundary. Due to the geometric constraints of the corner boundary, very few can form a triangular configuration (the bidirectional land boundary forms an acute angle) under this condition; most are quadrilateral, pentagonal, hexagonal, or more-sided configurations. Differentiated enclosure rules are adopted for different polygon configurations: When the number of sides of the target unit is equal to 3, perpendicular lines are drawn from the candidate enclosure points corresponding to the 1 common edge to the site boundaries corresponding to the 2 non-common edges, and a closed clean enclosure is constructed by the perpendicular lines and the site boundaries. When the number of sides of the target unit is equal to 4, draw perpendicular lines from the candidate enclosure points corresponding to the two common sides to the site boundary corresponding to their adjacent non-common sides, connect the two candidate enclosure points, and construct a closed clean enclosure with the perpendicular lines and the site boundary; for example Figure 14 As shown; When the target unit has 5 or more sides, common edges are removed according to the preset elimination rules until the target unit has 4 sides remaining. The candidate enclosure points corresponding to the remaining 2 common edges are then used to construct a closed, clean enclosure in the manner used when the target unit has 4 sides. This ensures a uniform enclosure shape and that any points exceeding the standard are centered.

[0044] (3) The third type is a special plot boundary where the target unit has three non-common edges. When the target point is located in a special area such as a plot depression or narrow strip, and is adjacent to three plot boundaries, the original Tyson polygon and the plot boundary form a polygon. Constrained by the three boundaries, it cannot form a triangular configuration, and is mostly a quadrilateral or pentagonal configuration. Hexagonal or more open-side configurations are very rare. It can be combined with the three plot boundaries to form a complete polygon. Differentiated enclosure rules are adopted for different polygon configurations: When the number of sides of the target unit is equal to 4, then the candidate enclosure points corresponding to one common side are perpendicular to the site boundaries corresponding to the two adjacent non-common sides, and a closed clean enclosure is constructed by the perpendicular lines and the site boundaries. When the target unit has 5 or more sides, such as Figure 15 As shown, common edges are eliminated according to the preset elimination rules until the target unit has 4 edges remaining. The candidate enclosure points corresponding to the remaining 2 common edges are used to construct a closed clean enclosure in the manner that the number of edges of the target unit is equal to 4.

[0045] In a preferred embodiment of the present invention, when the shape of the site boundary has a turning point, and the perpendicular line drawn from the candidate enclosure point to the site boundary corresponding to its adjacent non-common edge cannot fall on the site boundary segment, the perpendicular line is replaced by the line connecting the candidate enclosure point and the turning point of the site boundary. The line, the site boundary segment, and the line connecting the candidate enclosure points together enclose and form a closed clean enclosure.

[0046] Specifically, the inflection point refers to the turning point where the direction of the site boundary changes abruptly, that is, where two adjacent site boundary segments form a non-180° angle at this point. When a candidate enclosure point is perpendicular to the site boundary, if the foot of the perpendicular falls on the extension line of that site boundary segment rather than the boundary segment itself, it is determined that the foot of the perpendicular cannot fall on that site boundary segment. In this case, the line connecting the candidate enclosure point and the inflection point of the site boundary is used instead of the perpendicular line, such as... Figure 15 As shown.

[0047] When the site boundary has inflection points (such as L-shaped or sawtooth-shaped boundaries), the foot of the perpendicular line drawn from some candidate enclosure points to the site boundary may fall outside the boundary segment. If the foot of the perpendicular is forcibly taken on the extended line, the perpendicular segment will exceed the site area, resulting in the enclosure exceeding the boundary. Using the inflection point as the connection point ensures that the endpoint of the connecting line falls on the site boundary, while also allowing the enclosure boundary to naturally curve along the site boundary, preventing boundary violations.

[0048] In a preferred embodiment of the present invention, the specific steps for merging the closed clean enclosures according to their spatial adjacency to generate a continuous contaminated area include: Iterate through all closed clean surfaces and determine whether any two closed clean surfaces share a common edge. If two closed clean surfaces share a common edge, delete the common edge and merge the two closed clean surfaces into a single region. Repeat the above judgment and merging operations until there are no more adjacent closed clean enclosures that can be merged, forming a continuous contaminated area.

[0049] Specifically, by using fixed topological adjacency fusion rules, spatially adjacent exceeding-standard units are connected as a whole. In the traditional manual drawing process of cleaning points, human error such as visual judgment bias, hand-drawn breaks, omissions, or neglect of local blank areas can easily lead to missing points, incomplete delineation, fragmentation, and local gaps in areas exceeding standards. This embodiment completely eliminates these human defects through automated shared edge detection and merging operations, achieving complete, full-coverage, and seamless automated delineation of contaminated areas. The final output is a vector surface showing the overall pollutant exceeding-standard range with continuous boundaries, complete topology, and no gaps or omissions.

[0050] In a preferred embodiment of the present invention, when obtaining candidate enclosure points, if the sampling points inside the adjacent Thiessen polygonal units that share a common edge with the target unit are out-of-range points, then the sampling points inside the adjacent Thiessen polygonal units are not used as candidate enclosure points for the target unit, and the closed clean enclosure is constructed by the clean points inside the remaining adjacent Thiessen polygonal units.

[0051] In a preferred embodiment of the present invention, the lengths of the common sides of the target unit are obtained in the following manner: Under a preset projection coordinate system, the vector line segment data of the Thiessen polygon unit is read, and the length of the vector line segment corresponding to each common edge is calculated.

[0052] Specifically, in the soil pollution status survey data screening platform, after the Thiessen polygons are constructed, each Thiessen polygon cell is stored in vector graphics data format. Each Thiessen polygon cell is enclosed by several edges (line segments), and each edge has definite start and end coordinates. After reading the boundary line segment data of the target cell, the system traverses each edge and identifies the line segments belonging to the common edge (that is, the line segment is also the boundary line segment of a certain adjacent Thiessen polygon cell). For each identified common edge, the length is calculated in a preset projection coordinate system based on its start and end coordinates to obtain the length value of the common edge.

[0053] By processing the coordinates of sampling points under a predefined projected coordinate system, all side length calculations are ensured to be based on a unified benchmark, avoiding inconsistencies in length values ​​across different coordinate systems. The length is directly calculated using the endpoint coordinates of vector line segment data; this algorithm is simple and computationally efficient, providing an accurate data foundation for subsequent sorting and elimination operations.

[0054] In a preferred embodiment of the present invention, the automatic delineation method is executed independently for a single pollutant index and a single soil layer, generating a corresponding continuous pollution area for each pollutant index and each soil layer.

[0055] Specifically, in soil pollution surveys, a site typically involves multiple pollutant indicators and multiple soil layers. Different pollutant indicators have different spatial distribution patterns, and the pollution status of different soil layers also varies. Therefore, it is necessary to draw pollution extent maps for each pollutant in each soil layer separately.

[0056] In practice, all sampling points are first grouped according to their respective soil layers based on the generalized soil layer information. Then, for each soil layer, the automatic delineation method is applied to each pollutant index at each sampling point within that soil layer, ultimately generating multiple continuous pollution area maps multiplied by the number of pollutant indexes and the number of soil layers.

[0057] The algorithm enables automatic batch execution, which can complete the delineation of the pollution range of all combinations in a short time. The drawing standards of each map are completely consistent, and the results are reproducible, which greatly improves work efficiency and the quality of results. It provides comprehensive and accurate data support for subsequent remediation engineering quantity calculation and remediation plan preparation.

[0058] The present invention also provides an automatic delineation system for surrounding soil contaminated surfaces using clean points, for performing the above-described automatic delineation method for surrounding soil contaminated surfaces using clean points, comprising: The data preprocessing module is used to acquire sampling point data, which includes the spatial coordinates of each sampling point and the pollutant concentration detection value. The sampling point classification module is used to classify sampling points into clean points and points exceeding the standard based on the comparison results between the pollutant concentration detection values ​​of each sampling point and the preset risk screening values. The Thiessen polygon building module is used to construct Thiessen polygons based on all sampling points, so that each Thiessen polygon cell contains only one sampling point. The target unit identification module is used to identify Thiessen polygon units containing excessive points as target units, and to obtain the clean points corresponding to the common edges of the target units as candidate enclosure points. The enclosure construction module is used to construct a closed clean enclosure from the candidate enclosure points when the number of sides of the target unit is less than or equal to 4; when the number of sides of the target unit is greater than 4, it gradually eliminates the common sides according to the length of each common side of the target unit and according to the preset elimination rules until the target unit has 4 sides remaining, and constructs a closed clean enclosure from the candidate enclosure points corresponding to the common sides of the remaining 4 sides. The area fusion module is used to merge each closed clean enclosure according to its spatial adjacency to generate a continuous contaminated area. The mapping module is used to receive the continuous contaminated surface region generated by the surface region fusion module and export the continuous contaminated surface region as a vector file in a preset format.

[0059] Specifically, the continuous contaminated areas generated by the area fusion module are in the platform's internal vector data format, containing the boundary coordinates and corresponding attribute data of each area. After receiving this data, the mapping module converts it into a standard vector file for external use. The preset formats include SHP format, a common vector data format in the geographic information system (GIS) field, which can be directly read, edited, and used for secondary calculations by various mainstream GIS software, data analysis software, and engineering calculation software. The vector files output by the mapping module are suitable for pollution range statistics, remediation boundary delineation, engineering quantity calculation, output of result maps, and subsequent refined data analysis.

[0060] In a preferred embodiment of the present invention, the automatic delineation system is deployed on a soil pollution status survey data screening platform, the soil pollution status survey data screening platform further comprising: The sampling management module is used to upload sampling point files, sampling plan files, and assign sampling tasks; The Android mobile app is used to receive and display information from the sampling management module, and to perform on-site sampling and recording. The data aggregation module is used to generate sampling point data, including spatial coordinates and pollutant concentration detection values, based on the sampling data from the Android mobile device. The benchmarking standard database is used to store national standards, local standards, industry standards, foreign standards and risk screening values. Based on the land use type, pollutant type and soil layer information corresponding to the sampling point, the preset risk screening value of the pollutant concentration detection value corresponding to the sampling point is matched from the benchmarking standard database. The automatic delineation system's data preprocessing module obtains sampling point data from the data aggregation module and preset risk screening values ​​from the benchmark database.

[0061] This embodiment embeds the automatic delineation system into the soil pollution status survey data screening platform, realizing full-process information management from on-site sampling, data aggregation, classification and judgment, boundary delineation to result output, which greatly improves the work efficiency and result quality of soil pollution status surveys.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An automatic delineation method for surrounding contaminated soil surfaces using clean points, characterized in that, Includes the following steps: Acquire sampling point data, which includes the spatial coordinates of each sampling point and the pollutant concentration detection value; Based on the comparison between the pollutant concentration detection values ​​at each sampling point and the preset risk screening values, the sampling points are divided into clean points and points exceeding the standard. Construct Thiessen polygons based on all sampling points, so that each Thiessen polygon unit contains only one sampling point. Identify the Thiessen polygonal units containing points exceeding the standard as target units, and obtain the cleaning points corresponding to the common edges of the target units as candidate enclosure points; wherein, the common edge refers to the edge shared by the target unit and the adjacent Thiessen polygonal units, and the edge of the target unit that coincides with the site boundary is a non-common edge. When the number of sides of the target unit is less than or equal to 4, a closed clean enclosure is constructed from the candidate enclosure points; when the number of sides of the target unit is greater than 4, according to the length of each common side of the target unit, the common sides are gradually eliminated according to the preset elimination rules until the target unit has 4 sides remaining, and a closed clean enclosure is constructed from the candidate enclosure points corresponding to the common sides of the remaining 4 sides. Each closed clean enclosure is merged according to its spatial adjacency to generate a continuous contaminated area.

2. The automatic delineation method for surrounding soil contamination surfaces using clean points according to claim 1, characterized in that: The preset rejection rules specifically include: Extract all common edges of the target unit and obtain the length of each common edge; Sort all common edges in ascending order of length; In the first round of elimination, the shortest common edge among all common edges is selected and eliminated. From the second round onwards, in each round of elimination, the shortest common edge that has not been eliminated and is not adjacent to any eliminated common edge is selected and eliminated. This process is repeated until the target unit has 4 edges remaining.

3. The automatic delineation method for surrounding soil contamination surfaces using clean points according to claim 1, characterized in that: When the target unit does not have any non-common edges, the steps for constructing a closed clean enclosure from the candidate enclosure points are as follows: When the number of edges of the target unit is less than or equal to 4, the candidate enclosure points corresponding to each common edge are connected in sequence to construct a closed clean enclosure. When the number of edges of the target unit is greater than 4, the edges are gradually removed from the common edges according to the preset removal rules until the target unit has 4 edges remaining. The candidate enclosure points corresponding to the remaining 4 common edges are then connected in sequence to construct a closed clean enclosure.

4. The automatic delineation method for surrounding soil contamination surfaces using clean points according to claim 1, characterized in that: When the target unit has non-common edges, the steps for constructing a closed clean enclosure from the candidate enclosure points are as follows: When the number of sides of the target unit is less than or equal to 4, perpendicular lines are drawn from the candidate enclosure points corresponding to the common side to the site boundary corresponding to the adjacent non-common side. The candidate enclosure points are connected in sequence, and the connection lines between the candidate enclosure points, the perpendicular lines, and the site boundary segments corresponding to the non-common side are used to enclose and form a closed clean enclosure. When the number of edges of the target unit is greater than 4, the edges are gradually removed from the common edges according to the preset removal rules until the target unit has 4 edges remaining. A closed clean enclosure is then constructed in the manner that the number of edges of the target unit is equal to 4.

5. The automatic delineation method for surrounding soil contamination surfaces using clean points according to claim 4, characterized in that: When the shape of the site boundary has inflection points, and the perpendicular line drawn from the candidate enclosure point to the site boundary corresponding to its adjacent non-common edge cannot fall on the site boundary segment, the perpendicular line is replaced by the line connecting the candidate enclosure point and the inflection point of the site boundary. The line, the site boundary segment, and the line connecting the candidate enclosure points together form a closed clean enclosure.

6. The automatic delineation method for surrounding soil contamination surfaces using clean points according to claim 1, characterized in that: The specific steps for merging the closed clean enclosures according to their spatial adjacency to generate a continuous contaminated area include: Iterate through all closed clean surfaces and determine whether any two closed clean surfaces share a common edge. If two closed clean surfaces share a common edge, delete the common edge and merge the two closed clean surfaces into a single region. Repeat the above judgment and merging operations until there are no more adjacent closed clean enclosures that can be merged, forming a continuous contaminated area.

7. The automatic delineation method for surrounding soil contamination surfaces using clean points according to claim 1, characterized in that: When acquiring candidate enclosure points, if the sampling points inside the adjacent Thiessen polygonal units that share a common edge with the target unit are out-of-range points, then the sampling points inside the adjacent Thiessen polygonal units will not be used as candidate enclosure points for the target unit, and the closed clean enclosure will be constructed from the clean points inside the remaining adjacent Thiessen polygonal units.

8. The automatic delineation method for surrounding soil contamination surfaces using clean points according to claim 1, characterized in that: The lengths of the common edges of the target unit are obtained in the following way: Under a preset projection coordinate system, the vector line segment data of the Thiessen polygon unit is read, and the length of the vector line segment corresponding to each common edge is calculated.

9. An automatic delineation system for surrounding contaminated soil surfaces using clean points, characterized in that: The method for automatically delineating a soil contaminated surface using clean points as described in any one of claims 1-8 includes: The data preprocessing module is used to acquire sampling point data, which includes the spatial coordinates of each sampling point and the pollutant concentration detection value. The sampling point classification module is used to classify sampling points into clean points and points exceeding the standard based on the comparison results between the pollutant concentration detection values ​​of each sampling point and the preset risk screening values. The Thiessen polygon building module is used to construct Thiessen polygons based on all sampling points, so that each Thiessen polygon cell contains only one sampling point. The target unit identification module is used to identify Thiessen polygon units containing excessive points as target units, and to obtain the clean points corresponding to the common edges of the target units as candidate enclosure points. The enclosure construction module is used to construct a closed clean enclosure from the candidate enclosure points when the number of sides of the target unit is less than or equal to 4; when the number of sides of the target unit is greater than 4, it gradually eliminates the common sides according to the length of each common side of the target unit and according to the preset elimination rules until the target unit has 4 sides remaining, and constructs a closed clean enclosure from the candidate enclosure points corresponding to the common sides of the remaining 4 sides. The area fusion module is used to merge each closed clean enclosure according to its spatial adjacency to generate a continuous contaminated area. The mapping module is used to receive the continuous contaminated surface region generated by the surface region fusion module and export the continuous contaminated surface region as a vector file in a preset format.

10. The automatic delineation system for surrounding soil contamination surfaces using clean points according to claim 9, characterized in that, The automatic delineation system is deployed on the soil pollution status survey data screening platform, which also includes: The sampling management module is used to upload sampling point files, sampling plan files, and assign sampling tasks; The Android mobile app is used to receive and display information from the sampling management module, and to perform on-site sampling and recording. The data aggregation module is used to generate sampling point data, including spatial coordinates and pollutant concentration detection values, based on the sampling data from the Android mobile device. The benchmarking standard database is used to store national standards, local standards, industry standards, foreign standards and risk screening values. Based on the land use type, pollutant type and soil layer information corresponding to the sampling point, the preset risk screening value of the pollutant concentration detection value corresponding to the sampling point is matched from the benchmarking standard database. The automatic delineation system's data preprocessing module obtains sampling point data from the data aggregation module and preset risk screening values ​​from the benchmark database.

Images