Seawall wave absorbing block displacement tracking method and system

Abstract

The invention discloses a seawall wave absorbing block displacement tracking method and system. The method comprises the following steps: regularly collecting three-dimensional point cloud data; segmenting the three-dimensional point cloud data according to a set ceramic tile area; processing the point cloud data of the segmented ceramic tile area, introducing a three-dimensional geometric model of the wave absorbing block, extracting the point cloud data of a single wave absorbing block, and calculating the center coordinate of the point cloud data; performing registration on the multi-temporal three-dimensional point cloud data by using the angular points of the fixed building, and performing point cloud superposition on the central points of the wave absorbing blocks of each time sequence; and the three-dimensional displacement is calculated by matching the center point of the same wave absorbing block. The system comprises a scanning module, a segmentation module, a monomer extraction module, a registration module and a displacement calculation module. By using the method of the invention, the displacement change of the wave absorbing block in the multi-temporal point cloud can be accurately tracked. The method can be widely applied to the field of seawall monitoring.

Description

Technical Field

[0001] The present invention relates to the field of seawall monitoring, and particularly to a method and system for tracking the displacement of wave dissipating blocks on a seawall. Background Art

[0002] As an important protective facility in coastal areas, the main structure of the seawall and its attached wave dissipating blocks may undergo displacement, settlement or even detachment under the long-term action of tides, waves and storm surges. This will weaken the protective function of the seawall and pose a threat to the safety of coastal infrastructure and residents. Therefore, accurately monitoring the displacement change of the wave dissipating blocks on the seawall is of great significance for evaluating the safety of the seawall structure and optimizing the protection design. Although traditional monitoring methods (such as manual measurement, total station and RTK-GPS) can provide a certain degree of accuracy, they often suffer from low efficiency, limited coverage and difficulty in adapting to complex stacked structures. Summary of the Invention

[0003] In view of this, in order to solve the technical problems of the existing seawall wave dissipating block monitoring methods that cannot meet the timeliness, scope and accuracy required by the actual scenario, on the one hand, the present invention proposes a method for tracking the displacement of seawall wave dissipating blocks, and the method includes the following steps:

[0004] Regularly collect three-dimensional point cloud data;

[0005] Divide the three-dimensional point cloud data according to the established tile areas;

[0006] Based on the RANSAC algorithm, process the point cloud data of the segmented tile areas, introduce the three-dimensional geometric model of the wave dissipating blocks, extract the point cloud data of the individual wave dissipating blocks and calculate their center coordinates;

[0007] Use the corner points of fixed buildings to register the multi-temporal three-dimensional point cloud data, and superimpose the point clouds of the center points of the wave dissipating blocks in each time series;

[0008] Calculate the three-dimensional displacement amount by matching the center points of the same wave dissipating block.

[0009] In some embodiments, in order to reduce the error caused by the angular difference, it further includes;

[0010] Project the displacement components of the center point of the wave dissipating block onto the reference plane, and optimize the displacement calculation result using the principle of similar triangles.

[0011] In some embodiments, in order to ensure the integrity of the segmentation result and the continuity of the data at the boundary, and provide more reliable point cloud data support for subsequent processing, during the segmentation process, it further includes:

[0012] Set a certain range of buffer zones for each area.

[0013] In some embodiments, the three-dimensional geometric model of the wave dissipating block consists of four truncated cones (frustums of a cone), where the central axis of one frustum coincides with the z-axis, and the central axes of the other three frustums are symmetrically distributed around the z-axis at an angle of 120 degrees. Through this fitting method based on geometric features, the three-dimensional structure and its spatial position of a single wave dissipating block can be extracted more precisely.

[0014] In some embodiments, to further extract the wave dissipating blocks that have not been recognized, it further includes:

[0015] Stitch the remaining outlier cloud data after extracting a single wave dissipating block, and repeat the RANSAC segmentation to extract a single wave dissipating block and calculate its central coordinates.

[0016] The present invention also proposes a displacement tracking system for wave dissipating blocks on a high seawall, and the system includes:

[0017] A scanning module for regularly collecting three-dimensional point cloud data;

[0018] A segmentation module for segmenting the three-dimensional point cloud data according to a predetermined tile area;

[0019] A single-block extraction module processes the point cloud data of the segmented tile area based on the RANSAC algorithm, introduces the three-dimensional geometric model of the wave dissipating block, extracts the point cloud data of a single wave dissipating block and calculates its central coordinates;

[0020] A registration module registers the multi-temporal three-dimensional point cloud data using the corner points of fixed buildings and superimposes the point clouds of the central points of the wave dissipating blocks in each time series;

[0021] A displacement calculation module calculates its three-dimensional displacement by matching the central points of the same wave dissipating block.

[0022] Based on the above solution, a method for tracking the displacement of wave dissipating blocks on a seawall based on three-dimensional laser scanning and the RANSAC algorithm provided by the present invention innovatively introduces the three-dimensional geometric model of the wave dissipating block, combines the RANSAC algorithm, realizes high-precision segmentation and fitting of irregularly arranged wave dissipating blocks, and overcomes the problem that traditional methods cannot accurately identify in the case of complex stacking and occlusion. Secondly, by accurately tracking the displacement changes of wave dissipating blocks in multi-temporal three-dimensional point clouds, the noise interference and geometric deviation are effectively reduced, and the accuracy and reliability of displacement monitoring are significantly improved. At the same time, by using the multi-temporal point cloud registration and superposition technology, the point cloud data of a large-scale seawall area is quickly processed, and the data processing efficiency is greatly improved. In addition, this technology can provide an efficient and intelligent solution for seawall dynamic monitoring, wave dissipating block optimization design and disaster warning, is applicable to complex marine environments, has strong engineering applicability, and has important practical application value. Description of the Drawings

[0023] Figure 1It is the flowchart of the steps of a method for tracking the displacement of a seawall wave dissipating block according to the present invention;

[0024] Figure 2 It is the schematic diagram of the area of the actual seawall scene according to the present invention;

[0025] Figure 3 It is the schematic diagram of the segmentation by tile area in a specific embodiment of the present invention;

[0026] Figure 4 It is the schematic diagram of the process of the frustum translation in a specific embodiment of the present invention;

[0027] Figure 5 It is the schematic diagram of the process of generating leg 2 after the frustum rotation in a specific embodiment of the present invention;

[0028] Figure 6 It is the schematic diagram of the process of generating leg 3 and leg 4 after the frustum rotation in a specific embodiment of the present invention;

[0029] Figure 7 It is the schematic diagram of the geometric model of the wave dissipating block in a specific embodiment of the present invention. Detailed implementation manners

[0030] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0031] It should be noted that for the convenience of description, only the parts related to the relevant invention are shown in the drawings. Without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0032] It should be understood that the "system", "device", "unit" and / or "module" used in the present application are a method for distinguishing different components, elements, parts, portions or assemblies at different levels. However, if other words can achieve the same purpose, they can be replaced by other expressions.

[0033] As shown in the present application and the claims, unless the context clearly indicates an exceptional situation, words such as "a", "an", "one" and / or "the" are not specifically singular, but may also include plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the clearly identified steps and elements, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements. Elements defined by the statement "including one..." do not exclude the existence of other identical elements in the process, method, commodity or device including the element.

[0034] In the description of the embodiments of the present application, "a plurality" means two or more than two. The following terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0035] In addition, flowcharts are used in the present application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the operations before or after do not necessarily need to be executed precisely in sequence. On the contrary, the steps can be processed in reverse order or simultaneously. At the same time, other operations can also be added to these processes, or one or several steps can be removed from these processes.

[0036] Refer to Figure 1 , which is a schematic flowchart of an optional example of the seawall wave-dissipating block displacement tracking method proposed by the present invention. This method can be applied to computer devices. The displacement tracking method proposed in this embodiment may include but is not limited to the following steps:

[0037] Step S1: Use a drone equipped with a laser scanner to regularly collect three-dimensional point cloud data covering the seawall wave-dissipating block stacking area;

[0038] Step S2: Divide the overall collected three-dimensional point cloud data according to the pre-set tile area division rules to obtain the segmented point cloud data;

[0039] Step S3: Based on the three-dimensional geometric model of the wave-dissipating block, apply the RANSAC algorithm to process the segmented point cloud data to extract the point cloud data of the single wave-dissipating block; among them, the RANSAC fitting model uses the newly proposed three-dimensional geometric model of the wave-dissipating block, which is composed of four truncated cones (frustums of a cone). The central axis of one frustum coincides with the z-axis, and the central axes of the other three frustums are symmetrically distributed around the z-axis at an angle of 120 degrees.

[0040] Step S4: Register the multi-temporal three-dimensional point cloud data of the seawall wave-dissipating block area based on the corner points of the reference object to obtain the registered data;

[0041] Step S5: Based on the registered data and the point cloud data of the single wave-dissipating block, match the center points of the same wave-dissipating block and calculate its three-dimensional space displacement amount to obtain the displacement data.

[0042] The schematic diagram of this seawall scene refers to Figure 2 .

[0043] In some feasible embodiments, step S1 specifically includes:

[0044] The collected area includes fixed buildings around the seawall as reference targets to ensure the comprehensiveness of data collection and the accuracy of subsequent processing.

[0045] By planning the UAV flight path to cover the entire riprap accumulation area and including the fixed buildings in the scanning range, using their stable geometric features (such as corner points, edges, etc.) as the registration benchmark for multi-temporal point cloud data, to ensure the unity and comparability of the data.

[0046] In some feasible embodiments, step S2 specifically includes:

[0047] As Figure 3 shown, divide the point cloud data by tile area and introduce a buffer zone at the boundary to reduce errors and ensure data integrity.

[0048] Among them, the buffer zone supports area splicing and multi-temporal monitoring analysis, improving the accuracy and efficiency of riprap change monitoring.

[0049] In some feasible embodiments, step S3 specifically includes:

[0050] For each tile of point cloud, use the RANSAC hybrid riprap 3D model fitting method to extract a single riprap block and calculate its center at the same time.

[0051] First, start from the highest point of each tile and its k neighbor points, and fit the frustum formula (i.e., the cone formula):

[0052] x 2 +y 2 =(r - cz) 2

[0053] r is the radius of the frustum at the height of z = 0.

[0054] As Figure 4 shown, (x, y, z) is the nominal position of each point in the point cloud, that is, the original position after translation and rotation restoration, which is obtained by first translating the original coordinates of the point cloud to the origin and then rotating and transforming around the x-axis and y-axis:

[0055]

[0056] Ω and Φ respectively represent the rotation angles around the x and y axes, R 1 、R 2 respectively represent the rotation matrices around the x and y axes, and c is the gradient factor of the frustum.

[0057] After rotation, the central axis of the frustum has overlapped with the z-axis and can be defined as the riprap leg 1 (q = 1). When leg 1 rotates 120° around the x-axis, leg 2 (q = 2) can be obtained, as Figure 5 shown.

[0058] By rotating the leg 2 by 120° and 240° respectively around the z-axis, the legs 3 (q = 3) and 4 (q = 4) can be generated, as Figure 6 shown.

[0059] Therefore, the geometric model of the wave dissipating block can be expressed as:

[0060] x 2 +y 2 =(r - cz) 2

[0061]

[0062] where Ω and Φ represent the rotation angles around the X and Y axes respectively, R 1 , R 2 , R 3 represent the rotation matrices around the X, Y and Z axes respectively, q is the serial number of the leg of the frustum, and (x c , y c , z c ) is the central coordinate point of the wave dissipating block.

[0063] By iterating the RANSAC process to perform least-squares fitting of the point cloud to this model ( Figure 7 ), the single wave dissipating block can be extracted and the coordinates of its center point can be calculated.

[0064] Currently, in order to track the wave dissipating block, a large number of geometric fittings and analyses of different planes are required, lacking a method for considering the shape, position and attitude of the entire wave dissipating block. The present invention proposes a new three-dimensional geometric model of the wave dissipating block, realizing high-precision segmentation and fitting of irregularly arranged wave dissipating blocks in a large area. Through point cloud segmentation and geometric fitting, the problems of complex stacking and occlusion are solved, and the displacement changes of the wave dissipating block in multi-temporal point clouds are accurately tracked.

[0065] RANSAC is a classic robust estimation algorithm, widely used in the segmentation of three-dimensional point clouds, geometric model fitting and registration (Fischler and Bolles, 1981). It searches for the largest consistent point set in the point cloud that conforms to a specific geometric model (such as a plane, a cylinder or a polyhedron) by iterative random sampling, thereby removing noise and outliers. For the wave dissipating blocks of the seawall, the RANSAC algorithm can be used for feature point extraction, identification of single wave dissipating blocks, and matching and registration of multi-temporal point clouds. In addition, the noise resistance of RANSAC gives it significant advantages in complex marine environments.

[0066] In some feasible embodiments, step S3 further includes:

[0067] After the inlier points in the model have been extracted into different single breakwater blocks, the remaining RANSAC outliers in the entire tile area are merged, and RANSAC segmentation is repeated to extract the remaining single breakwater blocks, and their central coordinates are calculated.

[0068] In some feasible embodiments, step S4 specifically includes:

[0069] In order to register multi-temporal point clouds using the corner points of fixed buildings and overlay the point clouds of the center points of the breakwater blocks in each time series, Horn's Method can be used to perform accurate rigid transformation calculations. In multi-temporal point clouds (P 1 , P 2 , …, P n ), select the corner points of fixed buildings as the reference point set. For example, the four corner point coordinates of a building in P 1 (which can be calculated using the plane fitting formula for facade and ceiling point clouds) are {a 1 , b 1 , c 1 , d 1}, and for P 2 , they are {a 2 , b 2 , c 2 , d 2}. Apply Horn's Method to calculate the rigid transformation (R, T) and register the point clouds of the center points of the breakwater blocks in multi-temporal.

[0070] In some feasible embodiments, step S5 specifically includes:

[0071] For the matched center point pairs of the breakwater blocks, calculate their three-dimensional displacement vector Δν:

[0072] Δυ = (υ x υ y υ z ) = (x t+1,i - x t,i y t+1,i - y t,i z t+1,i - z t,i )

[0073] And calculate the magnitude of the displacement (Euclidean distance), and organize the three-dimensional displacement vector into a time series result for subsequent analysis

[0074]

[0075] In some feasible embodiments, it further includes:

[0076] Optimize displacement calculation using the principle of similar triangles. Project the displacement components of the multi-temporal center points onto the reference plane, correct the x, y, and z components through proportional relationships, and reduce the errors caused by angular differences, thereby improving the accuracy of displacement calculation.

[0077] Use the known geometric dimensions of the wave-dissipating block (such as the distance r from the feature point to the center point) to construct similar triangles:

[0078]

[0079] In the formula, Δp is the actual displacement vector; r c is the motion characteristic proportionality factor of the center point (which can be taken as the radius calculated by the least squares adjustment of the wave-dissipating block); r p is the motion ratio of the feature point (the distance from the feature point to the center point).

[0080] A displacement tracking system for seawall wave-dissipating blocks, comprising:

[0081] A scanning module that uses a drone equipped with a laser scanner to regularly collect three-dimensional point cloud data covering the piled-up area of the seawall wave-dissipating blocks;

[0082] A segmentation module that divides the overall collected three-dimensional point cloud data according to the pre-set tile area division rules to obtain the segmented point cloud data;

[0083] A single-block extraction module that processes the segmented point cloud data based on the three-dimensional geometric model of the wave-dissipating block using the RANSAC algorithm to extract the point cloud data of the single wave-dissipating block; among them, the RANSAC fitting model uses the newly proposed three-dimensional geometric model of the wave-dissipating block, which consists of four truncated cones (frustums of a cone), where the axis of one frustum coincides with the z-axis, and the axes of the other three frustums are symmetrically distributed around the z-axis at an angle of 120 degrees.

[0084] A registration module that registers the multi-temporal three-dimensional point cloud data of the seawall wave-dissipating block area based on the corner points of the reference object to obtain the registered data;

[0085] A displacement calculation module that matches the center points of the same wave-dissipating block based on the registered data and the point cloud data of the single wave-dissipating block and calculates its three-dimensional space displacement amount to obtain displacement data.

[0086] The content in the above method embodiments is applicable to the present system embodiment. The functions specifically implemented by the present system embodiment are the same as those in the above method embodiments, and the beneficial effects achieved are also the same as those in the above method embodiments.

[0087] A displacement tracking device for seawall wave-dissipating blocks:

[0088] At least one processor;

[0089] At least one memory for storing at least one program;

[0090] When the at least one program is executed by the at least one processor, the at least one processor implements a seawall wave dissipating block displacement tracking method as described above.

[0091] The content in the above method embodiments is applicable to the device embodiments of the present invention. The functions specifically implemented by the device embodiments of the present invention are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those of the above method embodiments.

[0092] A storage medium storing instructions executable by a processor, where the instructions executable by the processor are used to implement a seawall wave dissipating block displacement tracking method as described above when executed by the processor.

[0093] The content in the above method embodiments is applicable to the storage medium embodiments of the present invention. The functions specifically implemented by the storage medium embodiments of the present invention are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those of the above method embodiments.

[0094] The above has specifically described the preferred embodiments of the present invention, but the present invention is not limited to the described embodiments. Those skilled in the art can make various equivalent deformations or substitutions without departing from the spirit of the present invention, and these equivalent deformations or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A method for tracking the displacement of a seawall wave-breaking block, characterized in that: The following steps are involved: Obtain three-dimensional point cloud data of the seawall wave-breaking block area; Segmenting the three-dimensional point cloud data into a preset area to obtain segmented point cloud data; Based on the three-dimensional geometric model of the wave-breaking block, the segmented point cloud data is processed to extract the point cloud data of the single wave-breaking block; Registering the three-dimensional point cloud data of the seawall wave-breaking block area based on the corner points of the reference object to obtain registered data; Based on the registered data and the point cloud data of the single wave-breaking block, the center point of the same wave-breaking block is matched and the coordinate difference of the wave-breaking blocks between different time series is calculated to obtain the displacement data.

2. A method for tracking displacement of seawall wave-breaking blocks according to claim 1, characterized in that: Also includes: Project the displacement component of the center point of the wave-cutting block onto the reference plane, and correct the x, y, and z components through proportional relationships.

3. A method for tracking displacement of seawall wave-breaking blocks according to claim 1, characterized in that: The three-dimensional geometric model of the wave-breaking block is specifically composed of four frustums, wherein the central axis of one frustum coincides with the Z axis, and the central axes of the other three frustums are symmetrically distributed around the Z axis at an angle of 120 degrees.

4. A method for tracking displacement of seawall wave-breaking blocks according to claim 1, characterized in that: The expression of the three-dimensional geometric model of the wave-breaking block is as follows: x 2 +y 2 =(r-cz) 2 Among them, Ω and Φ represent the rotation angles around the X and Y axes respectively, R1, R2, and R3 represent the rotation matrices of the X, Y, and Z axes respectively, and q is the serial number of the legs of the frustum. c ,y c ,z c ) is the center coordinate point of the wave-breaking block, (x, y, z) represents the nominal position, r represents the radius of the cone at z = 0 height, and c represents the gradient factor of the cone.

5. A method for tracking displacement of seawall wave-breaking blocks according to claim 1, characterized in that: Also includes: Merge the remaining point clouds after extracting a single wave-breaking block point cloud to obtain the external point data; The point cloud data of the single wave-breaking block is extracted according to the external point data, and the center coordinates of each wave-breaking block are calculated.

6. A method for tracking displacement of seawall wave-breaking blocks according to claim 1, characterized in that: The step of segmenting the three-dimensional point cloud data into a preset area to obtain segmented point cloud data specifically includes: The three-dimensional point cloud data is divided into tile areas, and a buffer zone is introduced at the boundary to obtain segmented point cloud data.

7. A method for tracking displacement of seawall wave-breaking blocks according to claim 4, characterized in that: The step of registering the three-dimensional point cloud data of the seawall wave-breaking block area based on the corner points of the reference object to obtain the registered data specifically includes: In the multi-temporal 3D point cloud data of the seawall wave-breaking block area, the corner points of fixed buildings are selected as the reference point set; Based on the corner points of the fixed building, the Horn's Method is used to perform rigid transformation to complete the registration; Superimpose the center point cloud of the single wave-breaking block.

8. A seawall wave-breaking block displacement tracking system, characterized in that: include: A scanning module is used to obtain three-dimensional point cloud data of the seawall wave-breaking block area; A segmentation module, used to segment the three-dimensional point cloud data into a preset area to obtain segmented point cloud data; A monomer extraction module processes the segmented point cloud data based on the three-dimensional geometric model of the wave-breaking block to extract the point cloud data of the monomer wave-breaking block; A registration module, which registers the three-dimensional point cloud data of the seawall wave-breaking block area based on the corner points of the reference object to obtain registered data; The displacement calculation module matches the center point of the same wave-breaking block and calculates the coordinate difference of the wave-breaking blocks between different time series based on the registered data and the point cloud data of the single wave-breaking block to obtain the displacement data.

9. A seawall wave-breaking block displacement tracking device, characterized in that: include: at least one processor; at least one memory for storing at least one program; When the at least one program is executed by the at least one processor, the at least one processor implements the method for tracking the displacement of seawall wave-breaking blocks as described in any one of claims 1-7.

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