A method for constructing a three-dimensional model of a substation cable trench based on laser point cloud

Abstract

The present invention discloses a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud, including: after the completion of civil engineering construction such as the substation cable trench, first using a three-dimensional laser scanner to scan and obtain the laser point cloud data of the cable trench, then fitting the point cloud of the cable trench wall with a plane model, then fitting the point cloud of the cable support with a cuboid model, and finally establishing the positional relationship between the cable support and the cable trench wall, and outputting a complete three-dimensional model of the substation cable trench. This method efficiently and accurately realizes the three-dimensional visualization of the substation cable trench, which is beneficial for the staff to intuitively understand the construction situation of the cable trench and can provide direct guidance for the subsequent cable laying scheme design.

Description

Technical Field

[0001] The present invention relates to the technical field of transmission and transformation project construction, and more particularly to a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud. Background Art

[0002] Cable laying operation has always been an important part of substation construction. At present, it is still the main form for construction workers to complete cable laying operations with reference to 2D design drawings. This method is time-consuming and laborious and it is not easy to find problems. Specifically, on the one hand, construction workers need to search for 2D drawing information at the corresponding position, build a corresponding three-dimensional solid model in their minds, and then overlay this model onto the engineering site that the workers see at present. After determining that the model is correct, subsequent construction is carried out. However, this requires workers to have good spatial imagination ability and is extremely prone to judgment errors. On the other hand, after the completion of civil engineering construction such as substation cable trenches, the actual situation may deviate from the design drawings. At this time, if construction is still carried out according to the original drawings, construction problems will inevitably occur. Therefore, there is an urgent need to introduce new methods and new technologies to improve the current situation of substation cable laying operations. Summary of the Invention

[0003] An embodiment of the present invention provides a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud, including:

[0004] Obtaining laser point cloud data of the cable trench and segmenting the cable trench point cloud data to obtain the segmented cable trench point cloud;

[0005] Based on the segmented cable trench point cloud, extracting the cable trench wall point cloud and fitting the cable trench wall point cloud with a plane model to obtain a cable trench wall model;

[0006] Based on the cable trench wall model, identifying the cable support point cloud in the cable trench and fitting the identified cable support point cloud data with a cuboid model to obtain a cable support model;

[0007] Constructing a three-dimensional geometric model of the cable trench based on the cable trench wall model and the cable support model.

[0008] Furthermore, obtaining laser point cloud data of the cable trench and segmenting the cable trench point cloud data includes:

[0009] Scanning and obtaining laser point cloud data of the cable trench by using a ground-type or underground void-type three-dimensional laser scanner, and setting a scanning point every certain distance;

[0010] Using point cloud stitching software to stitch the point cloud data of each station's scanning points;

[0011] Place the point cloud data of the cable trench under the top view, and manually mark the center points of the cable trench at regular intervals along the cable trench direction. Among them, the center points must be marked at the corners of the cable trench;

[0012] Fit the straight line equation representing the cable trench direction according to the marked center points;

[0013] Segment the point cloud data of the cable trench according to the straight line equation to obtain the segmented point cloud of the cable trench;

[0014] Use the statistical analysis method to filter out the outlier points in the point cloud of the cable trench.

[0015] Furthermore, the steps to obtain the cable trench wall model include:

[0016] Perform voxel downsampling on the segmented point cloud of the cable trench to reduce the number of point clouds;

[0017] Use the random sample consensus algorithm to extract the four plane point clouds of the cable trench wall;

[0018] Fit the four plane point clouds of the extracted cable trench wall with four plane equations respectively to obtain the plane equations P1, P2, P3, and P4, where P1 and P2 are the two side planes of the cable trench perpendicular to the ground, and P3 and P4 are the bottom and top surfaces of the cable trench parallel to the ground;

[0019] Calculate the normal vector of each plane equation and check whether the adjacent planes are perpendicular to each other;

[0020] Calculate the intersection lines formed by every two adjacent planes, construct a closed cuboid, and filter out the irrelevant point clouds.

[0021] Furthermore, the steps to obtain the cable support model include:

[0022] Extract the point cloud q within the closed cuboid formed by the four planes;

[0023] Obtain the intermediate plane PO from P1 and P2;

[0024] Take the intermediate plane PO as the dividing line and divide the point cloud q into two parts, point cloud q1 and point cloud q2;

[0025] Use the random sample consensus algorithm to extract the straight line point clouds in point cloud q1 and point cloud q2 respectively;

[0026] Fit each straight line point cloud with a straight line equation and calculate the distance from each point on the straight line point cloud to the straight line {d1, d2,..., d n}, where n is the number of points on the straight line point cloud, take dist = max{d1, d2,... d n}, and let is the cross-sectional width of the cable support;

[0027] Calculate the projection length of the linear point cloud on the linear equation, and use this as the length of the cable support.

[0028] Furthermore, the steps for constructing the three-dimensional model of the cable trench include:

[0029] According to the intersection points {P1, P2,..., P m} of each linear equation of the cable support model and the plane of the cable trench wall model, where m is the number of cable supports, obtain the positions of each cable support;

[0030] Place the obtained cable support models at the corresponding intersection points in sequence;

[0031] Generate a three-dimensional geometric model of the cable trench in glTF format.

[0032] The embodiment of the present invention provides a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud. Compared with the prior art, its beneficial effects are as follows:

[0033] After the civil engineering construction of the substation cable trench is completed, the present invention uses a three-dimensional laser scanner to obtain its laser point cloud data and reversely reconstructs its three-dimensional model, providing guidance for the three-dimensional design of the cable laying scheme. The present invention can truly restore the construction site of the substation cable trench, improve the visualization level of the cable laying scheme design, reduce the probability of construction problems, and has good application prospects. Description of the Drawings

[0034] Figure 1 is the implementation flowchart of a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud provided by the embodiment of the present invention;

[0035] Figure 2 is the cable trench laser point cloud data of a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud provided by the embodiment of the present invention;

[0036] Figure 3 is the segmented cable trench laser point cloud data of a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud provided by the embodiment of the present invention;

[0037] Figure 4 is the cable trench point cloud data after voxel filtering of a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud provided by the embodiment of the present invention;

[0038] Figure 5 is the extracted cable trench wall point cloud of a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud provided by the embodiment of the present invention;

[0039] Figure 6 The cable support point cloud extracted by a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud provided by an embodiment of the present invention;

[0040] Figure 7 The completed three-dimensional model of the cable trench constructed by a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud provided by an embodiment of the present invention; Detailed implementation manners

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0042] See Figures 1 to 7 , the present invention provides a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud. Taking a certain substation as an example, the implementation process of the present invention will be described in detail.

[0043] As Figure 1 shown in the implementation flowchart of the present invention, a method for constructing a three-dimensional model of a substation cable trench based on laser point cloud includes the following steps:

[0044] (1) Scan to obtain the laser point cloud data of the cable trench, filter out the noise points, and divide the point cloud of the cable trench. Step (1) includes the following steps:

[0045] 1-1) In this embodiment, a Faro350 ground three-dimensional laser scanner is used to scan and obtain the laser point cloud data of the cable trench, and scanning points are set every 10 meters;

[0046] 1-2) Use Scene point cloud processing software to splice the point cloud data of each station's scanning points. The spliced cable trench point cloud data is as Figure 2 shown, and the point cloud size is 57,373,996 points. It is difficult to directly process such a large-scale point cloud, so the point cloud of the cable trench needs to be segmented;

[0047] 1-3) Place the cable trench point cloud data under the top view, and manually mark the center points of the cable trench every two meters along the cable trench direction. Among them, the center points at the corners of the cable trench must be marked;

[0048] 1-4) Fit the straight line equation representing the cable trench direction according to the marked center points;

[0049] 1-5) Segment the point cloud data of the cable trench according to the straight line equation so that the length of each part of the cable trench point cloud is between 5 and 10 meters, forming a point cloud set Q{q1, q2,... q n}, where n is the number of point clouds obtained by partitioning. As shown in Figure 3 , the point cloud of the cable trench obtained by one of the partitions is shown. The size of the point cloud is 12,757,595 points, and the scale of the point cloud is still very large.

[0050] 1-6) Therefore, the statistical analysis method is used to filter out the outliers in the cable trench point cloud. The number of neighborhood points is set to 6, and the distance threshold is set to 0.5 m. After processing, the size of the point cloud becomes 10,626,535 points;

[0051] (2) Use the Random Sample Consensus (RANSAC) algorithm to extract the point cloud of the cable trench wall and fit the point cloud of the cable trench wall with a plane model. Step (2) includes the following steps:

[0052] 2-1) Perform voxel downsampling on the cable trench point cloud. The voxel grid used here is a cube with a side length of 0.05 m. After voxel filtering, the size of the point cloud is 16,368 points. As shown in Figure 4 , it can be seen that the scale of the point cloud is greatly reduced, which is beneficial to improving the subsequent calculation efficiency;

[0053] 2-2) Use the RANSAC algorithm to extract the planes in the point cloud. The threshold δ for judging inliers is set to 0.05 m, and a total of 4 extractions are performed to obtain 4 plane point clouds. As shown in Figure 5 , different colors are used to mark the different planes extracted.

[0054] 2-3) Fit the four extracted plane point clouds with four plane equations respectively to obtain plane equations P1, P2, P3, P4, as follows:

[0055] P1: -0.0020765x + 0.587724y + 0.809059z = -2.57564

[0056] P2: -0.00520926x + 0.595778y + 0.80313z = -1.17696

[0057] P3: 0.277154x - 0.765081y + 0.581237z = -0.793404

[0058] P4: 0.281456x - 0.76606y + 0.577871z = 0.356916

[0059] Among them, P1 and P2 are the two side planes of the cable trench perpendicular to the ground, and P3 and P4 are the bottom and top planes of the cable trench parallel to the ground;

[0060] 2-4) Calculate the normal vector of each plane equation respectively and check whether it is perpendicular to the adjacent planes;

[0061] 2-5) Calculate the intersection lines formed by every two adjacent planes and filter out the irrelevant point clouds outside the closed cuboid formed by the four planes.

[0062] (3) Using a straight line model to identify the point cloud of the cable support in the cable trench, and fitting the identified point cloud data of the cable support with a rectangular parallelepiped model, step (3) includes the following steps:

[0063] 3-1) Extract the point cloud q in the closed cuboid formed by the four planes in step (2), as Figure 6 As shown, it can be seen that both sides of the cable channel wall are covered with cable brackets;

[0064] 3-2) Obtain the middle plane PO from P1 and P2:

[0065] PO:-0.00364289x+0.591752y+0.806095z=-1.8763

[0066] 3-3) Using the middle plane PO as the dividing line, divide the point cloud q into two parts q1 and q2;

[0067] 3-4) The straight line point clouds in point clouds q1 and q2 are extracted using a random sampling consensus algorithm, where the threshold ε for identifying in-place points is set to 0.1 meters. If the number of points in each straight line point cloud is greater than 50, the straight line point cloud is retained, otherwise it is discarded;

[0068] 3-5) Fit each line point cloud with a straight line equation and calculate the distance {d1, d2, ..., d n} (n is the number of points in the point cloud of the straight line), take dist = max{d1,d2,...d n}, and let Edist be the cross-sectional width of the cable support;

[0069] 3-6) Calculate the projection length L of the straight line point cloud on the straight line equation and use it as the length of the cable bracket.

[0070] (4) The cable trench wall model formed in step (2) and the cable support model formed in step (3) are spliced to generate a three-dimensional model of the cable trench. Step (4) includes the following steps:

[0071] 4-1) Calculate the intersection of each straight line equation with the plane to which it belongs {P1,P2,...,P m}(m is the number of cable brackets), i.e. the position of each cable bracket;

[0072] 4-2) Place the cuboid models representing cable supports at the corresponding intersection points in sequence, as Figure 7 shown;

[0073] 4-3) Generate a 3D model of the cable trench in glTF format.

[0074] The above are only several specific embodiments of the present invention disclosed. Those skilled in the art can make various changes and modifications to the embodiments of the present invention without departing from the spirit and scope of the present invention. However, the embodiments of the present invention are not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for constructing a three-dimensional model of a substation cable trench based on laser point cloud, characterized in that, Including: Obtain the laser point cloud data of the cable trench and segment the cable trench point cloud data to obtain the segmented cable trench point cloud; Based on the segmented cable trench point cloud, extract the cable trench wall point cloud and fit the cable trench wall point cloud with a plane model to obtain the cable trench wall model; Based on the cable trench wall model, identify the cable support point cloud in the cable trench and fit the identified cable support point cloud data with a cuboid model to obtain the cable support model; Construct a 3D geometric model of the cable trench based on the cable trench wall model and the cable support model; Among them, the steps of obtaining the laser point cloud data of the cable trench and segmenting the cable trench point cloud data include: Use a ground-based or underground void 3D laser scanner to scan and obtain the laser point cloud data of the cable trench, and set a scanning point every certain distance; Use point cloud stitching software to stitch the point cloud data of each station's scanning points; Place the cable trench point cloud data under the top view, and manually mark the center points of the cable trench at regular intervals along the cable trench direction. Among them, the center points at the cable trench corners must be marked; Fit the straight line equation representing the cable trench direction according to the marked center points; Segment the cable trench point cloud data according to the straight line equation to obtain the segmented cable trench point cloud; Use a statistical analysis method to filter out the outlier points in the cable trench point cloud; The steps of obtaining the cable trench wall model include: Perform voxel downsampling on the segmented cable trench point cloud to reduce the number of point clouds; Use the random sample consensus algorithm to extract the four plane point clouds of the cable trench wall; Respectively fit the four extracted plane point clouds of the cable trench wall with four plane equations to obtain plane equations P1, P2, P3, and P4, where P1 and P2 are the two side planes of the cable trench perpendicular to the ground, and P3 and P4 are the bottom and top surfaces of the cable trench parallel to the ground; Calculate the normal vector of each plane equation and check whether adjacent planes are perpendicular to each other; Calculate the intersection line formed by every two adjacent planes, construct a closed cuboid, and filter out the point clouds outside the cuboid; The steps of obtaining the cable support model include: Extract the point cloud q within the closed cuboid formed by the four planes; Obtain the middle plane PO from P1 and P2; Take the middle plane PO as the dividing line and divide the point cloud q into two parts of point cloud q1 and point cloud q2; Use the random sample consensus algorithm to extract the straight line point clouds in point cloud q1 and point cloud q2 respectively; For each straight line point cloud, perform linear equation fitting, and calculate the distance from each point on the straight line point cloud to the straight line {d1, d2, ..., d n} , where n is the number of points in the straight line point cloud, and take dist = max{d1, d2, ... d n}, and let Edist be the cross-sectional width of the cable bracket; Calculate the projection length of the straight line point cloud on the straight line equation, and use this as the length of the cable support; The steps of constructing the 3D geometric model of the cable trench include: According to the intersection points {P1, P2,..., P m} of each straight-line equation of the cable support model and the plane of the cable trench wall model, where m is the number of cable supports, the positions of each cable support are obtained; Place the obtained cable support model at the corresponding intersection points in turn; Generate a 3D geometric model of the cable trench in glTF format.

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