A seawall breakwater block displacement tracking method and system

Abstract

The application discloses a kind of sea embankment wave dissipating block displacement tracking method and system, the method comprises: periodically collecting three-dimensional point cloud data;Three-dimensional point cloud data is divided according to the intended tile area;The point cloud data of the tile area after segmentation is handled, introduce wave dissipating block three-dimensional geometric model, extract the point cloud data of single wave dissipating block and calculate its center coordinates;The corner points of fixed building are used to register multi-temporal three-dimensional point cloud data, and the center points of each time sequence wave dissipating block are point cloud superimposed;The three-dimensional displacement of the center point of the same wave dissipating block is calculated by matching it.The system comprises: scanning module, segmentation module, single extraction module, registration module and displacement calculation module.Using the application, the displacement change of wave dissipating block in multi-temporal point cloud can be accurately tracked.The application can be widely applied in sea embankment monitoring field.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of seawall monitoring, and in particular to a seawall breakwater block displacement tracking method and system. BACKGROUND

[0002] As an important protective facility in coastal areas, the main structure and attached breakwater blocks of seawalls may be displaced, subsided, or even detached under the long-term action of tides, waves, and storm surges, which can weaken the protective function of seawalls and pose a threat to coastal infrastructure and resident safety. Therefore, accurately monitoring the displacement changes of seawall breakwater blocks is of great significance for assessing the safety of seawall structures and optimizing protective design. Traditional monitoring methods (such as manual measurement, total station, and RTK-GPS) can provide certain accuracy, but often have problems such as low efficiency, limited coverage, and difficulty in adapting to complex stacked structures. SUMMARY

[0003] Therefore, in order to solve the technical problem that the existing seawall breakwater block monitoring method cannot meet the timeliness, range, and accuracy required by actual scenarios, in a first aspect, the present application proposes a seawall breakwater block displacement tracking method, which comprises the following steps:

[0004] Periodically collecting three-dimensional point cloud data;

[0005] Segmenting the three-dimensional point cloud data according to the predetermined tile area;

[0006] Processing the segmented tile area point cloud data based on the RANSAC algorithm, introducing a breakwater three-dimensional geometric model, extracting the point cloud data of individual breakwater blocks, and calculating the center coordinates thereof;

[0007] Registering the multi-temporal three-dimensional point cloud data using the corner points of fixed buildings, and superimposing the center point point clouds of the breakwater blocks of each time series;

[0008] Calculating the three-dimensional displacement of the center point of the same breakwater block by matching the center point.

[0009] In some embodiments, in order to reduce the error caused by the angle difference, the method further comprises:

[0010] Projecting the displacement components of the center point of the breakwater block onto the reference plane, and optimizing the displacement calculation result using the similar triangle principle.

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

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

[0013] In some embodiments, the three-dimensional geometric model of the breakwater block is composed of four truncated cones (truncated cones), one of which has a central axis coinciding with the z-axis, and the central axes of the other three 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 spatial position of the single breakwater block can be more accurately extracted.

[0014] In some embodiments, in order to further extract the breakwater blocks that have not been identified, the following steps are further included:

[0015] The remaining outer point cloud data after extracting the single breakwater block is spliced, and the RANSAC segmentation and extraction of the single breakwater block are repeated to calculate the center coordinates.

[0016] The present application also provides a high-seawall breakwater block displacement tracking system, which comprises:

[0017] The scanning module is used for regularly collecting three-dimensional point cloud data;

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

[0019] The single extraction module is used for processing the point cloud data of the segmented tile area based on the RANSAC algorithm, introducing a three-dimensional geometric model of the breakwater block, extracting the point cloud data of the single breakwater block and calculating the center coordinates thereof;

[0020] The registration module is used for registering the multi-temporal three-dimensional point cloud data by using the corner points of the fixed building, and superimposing the center point point clouds of the breakwater blocks in each time sequence;

[0021] The displacement calculation module is used for calculating the three-dimensional displacement of the same breakwater block by matching the center points thereof.

[0022] Based on the above scheme, the present application provides a seawall breakwater block displacement tracking method based on three-dimensional laser scanning and RANSAC algorithm, which innovatively introduces a three-dimensional geometric model of the breakwater block and combines the RANSAC algorithm to realize high-precision segmentation and fitting of irregularly placed breakwater blocks, overcoming the problem that the traditional method cannot accurately identify under complex stacking and shielding conditions. Secondly, by accurately tracking the displacement changes of the breakwater blocks in the multi-temporal three-dimensional point cloud, the noise interference and geometric deviation are effectively reduced, and the accuracy and reliability of the displacement monitoring are significantly improved. At the same time, by using the multi-temporal point cloud registration and superimposition technology, the point cloud data of a large range of seawall area can be 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, breakwater block optimization design and disaster warning, and is suitable for complex marine environments, has strong engineering applicability, and has important practical application value. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1is a step flow chart of a seawall wave dissipating block displacement tracking method of the present application;

[0024] Figure 2 is a regional schematic diagram of an actual seawall scene of the present application;

[0025] Figure 3 is a schematic diagram of the present application in which a specific embodiment is segmented according to tile regions;

[0026] Figure 4 is a process schematic diagram of the present application in which a specific embodiment is translated by a circular table;

[0027] Figure 5 is a process schematic diagram of the present application in which a specific embodiment generates leg 2 after rotating a circular table;

[0028] Figure 6 is a process schematic diagram of the present application in which a specific embodiment generates leg 3 and leg 4 after rotating a circular table;

[0029] Figure 7 is a geometric model schematic diagram of a wave dissipating block of a specific embodiment of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

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

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

[0033] As shown in the present application and claims, unless the context clearly indicates otherwise, "one", "a", "an" and / or "the" do not refer to the singular, but also include the plural. Generally, the terms "comprise" and "include" only indicate the inclusion of the steps and elements explicitly identified, and these steps and elements do not constitute an exclusive list, and the method or device can also include other steps or elements. The element defined by the statement "comprising a" does not exclude the presence of another identical element in the process, method, product or device comprising the element.

[0034] In the description of the embodiments of the present application, "multiple" refers to two or more than two. The following terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the 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 preceding or subsequent operations are not necessarily performed in sequence. On the contrary, each step can be processed in reverse order or simultaneously. Meanwhile, other operations can be added to these processes, or one or more steps of operations can be removed from these processes.

[0036] Referring to Figure 1 An optional example of the seawall breakwater block displacement tracking method proposed in the present application is shown in the flowchart. The method can be applied to a computer device. The displacement tracking method proposed in the present embodiment can include but is not limited to the following steps:

[0037] Step S1, using a UAV carrying a laser scanner to periodically collect three-dimensional point cloud data covering the seawall breakwater block accumulation area;

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

[0039] Step S3, based on the three-dimensional geometric model of the breakwater block, applying the RANSAC algorithm to process the segmented point cloud data to extract the point cloud data of the single breakwater block; wherein the RANSAC fitting model uses the newly proposed three-dimensional geometric model of the breakwater block, which is composed of four truncated cones (truncated cones). One of the truncated cones has its central axis coinciding with the z-axis, and the central axes of the other three truncated cones are symmetrically distributed around the z-axis at an angle of 120 degrees.

[0040] Step S4, registering the multi-temporal three-dimensional point cloud data of the seawall breakwater block area based on the reference corner points to obtain the registered data;

[0041] Step S5, based on the registered data and the point cloud data of the single breakwater block, matching the center points of the same breakwater block and calculating the three-dimensional spatial displacement amount to obtain the displacement data.

[0042] The schematic diagram of the seawall scene is shown in Figure 2 .

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

[0044] The collected area contains 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 route to cover the entire wave-damping block accumulation area and including fixed buildings in the scanning range, the stable geometric features (such as corner points, edges, etc.) of the fixed buildings are used as the registration reference for multi-temporal point cloud data, ensuring the uniformity and comparability of the data.

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

[0047] As shown in Figure 3 , the point cloud data is divided according to the tile area, and a buffer zone is introduced at the boundary to reduce errors and ensure data integrity.

[0048] The buffer zone supports area splicing and multi-temporal monitoring analysis, improving the accuracy and efficiency of wave-damping block change monitoring.

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

[0050] For each tile point cloud, the RANSAC hybrid wave-damping block three-dimensional model fitting method is used to extract a single wave-damping block and calculate its center at the same time.

[0051] First, starting from the highest point of each tile and its k neighbor points, a circular truncated cone formula (i.e. a conical formula) is fitted:

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

[0053] r is the radius of the circular truncated cone at z = 0 height.

[0054] As shown in Figure 4 , (x, y, z) is the nominal position of each point in the point cloud, i.e. the original position after translation and rotation restoration, which is obtained by translating the original coordinates of the point cloud to the origin and rotating around the x and y axes:

[0055]

[0056] Ω and Φ represent the rotation angles around the x and y axes respectively, R1 and R2 represent the rotation matrices of the x and y axes respectively, and c is the gradient factor of the circular truncated cone.

[0057] The central axis of the rotated circular truncated cone has already overlapped with the z axis, which can be defined as wave-damping block leg 1 (q = 1), and when leg 1 rotates 120° around the x axis, leg 2 (q = 2) can be obtained, as shown in Figure 5 .

[0058] Leg 2 rotates 120° and 240° around the z-axis, respectively, to generate leg 3 (q = 3) and leg 4 (q = 4), as shown. Figure 6

[0059] Therefore, the geometric model of the wave-breaking 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, R1, R2, R3 represent the rotation matrices of the X, Y, and Z axes, respectively, q is the serial number of the leg of the circular truncated cone, and (x c ,y c ,z c ) is the center coordinate point of the wave-breaking block.

[0063] By iterating the RANSAC process to least square fit the point cloud with this model, Figure 7 the single wave-breaking block can be extracted and the center coordinate point can be calculated.

[0064] Currently, the wave-breaking block is tracked by geometric fitting and analysis of a large number of different planes, and there is a lack of methods for considering the shape, position, and attitude of the whole wave-breaking block. The present application proposes a new three-dimensional geometric model of the wave-breaking block, which realizes high-precision segmentation and fitting of irregularly placed wave-breaking blocks in a large area. Through point cloud segmentation and geometric fitting, the problem of complex stacking and occlusion is solved, and the displacement change of the wave-breaking block in the multi-temporal point cloud is accurately tracked.

[0065] RANSAC is a classic robust estimation algorithm, which is widely used in three-dimensional point cloud segmentation, geometric model fitting, and registration (Fischler and Bolles, 1981). It finds the largest consistent point set in the point cloud that meets a certain geometric model (such as a plane, a cylinder, or a polyhedron) by iterating random sampling, thereby eliminating noise and abnormal points. For seawall wave-breaking blocks, the RANSAC algorithm can be used for feature point extraction, single wave-breaking block identification, and multi-temporal point cloud matching and registration. In addition, the noise resistance of RANSAC makes it have a significant advantage in complex marine environments.

[0066] In some possible embodiments, step S3 further comprises:

[0067] When the in-model points have been extracted into different single wave-breaking blocks, the remaining RANSAC out-points in the entire tile area are spliced, and the remaining single wave-breaking blocks are repeatedly extracted by RANSAC segmentation, and the center coordinates are calculated. ​

[0068] In some possible embodiments, step S4 specifically comprises:

[0069] In order to register the multi-temporal point clouds by using the corner points of fixed buildings, and superimpose the point clouds of the center points of the wave suppression blocks of each time sequence, Horn's Method can be used to calculate the precise rigid transformation. In the multi-temporal point clouds (P1, P2, …, P n ), the corner points of the fixed buildings are selected as the reference point set. For example, the coordinates of the four corner points of a building in P1 (which can be calculated by using the plane fitting formula of the facade and ceiling point clouds) are {a1, b1, c1, d1}, and those of P2 are {a2, b2, c2, d2}. Horn's Method is used to calculate the rigid transformation (R, T), and the multi-temporal point clouds of the center points of the wave suppression blocks are registered.

[0070] In some possible embodiments, step S5 specifically comprises:

[0071] For the matched center points of the wave suppression blocks, the three-dimensional displacement vector Δν is calculated:

[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] The size (Euclidean distance) of the displacement is calculated, and the three-dimensional displacement vector is sorted into the time sequence results for subsequent analysis

[0074]

[0075] In some possible embodiments, it further comprises:

[0076] The displacement calculation is optimized by using the principle of similar triangles, the displacement components of the multi-temporal center points are projected to the reference plane, the x, y, and z components are corrected through the proportional relationship, the error caused by the angle difference is reduced, and thus the displacement calculation accuracy is improved.

[0077] The known geometric size (such as the distance r from the feature point to the center point) of the wave suppression block is used to construct a similar triangle:

[0078]

[0079] In the formula, Δp is the actual displacement vector; r c is the motion feature proportional factor of the center point (which can be taken as the minimum radius calculated by the least squares of the wave suppression block); r pThe motion scale of the feature point (distance from the feature point to the center point).

[0080] A seawall breakwater block displacement tracking system comprises:

[0081] The scanning module periodically collects three-dimensional point cloud data covering the seawall breakwater block accumulation area by using a laser scanner carried by a UAV.

[0082] The segmentation module divides the overall collected three-dimensional point cloud data according to a pre-set tile area division rule to obtain segmented point cloud data.

[0083] The single body extraction module processes the segmented point cloud data based on a breakwater three-dimensional geometric model and extracts the point cloud data of a single breakwater block by using a RANSAC algorithm. The RANSAC fitting model uses a newly proposed breakwater three-dimensional geometric model, which is composed of four truncated cones (truncated tables). The central axis of one of the truncated tables coincides with the z-axis, and the central axes of the other three truncated tables are symmetrically distributed around the z-axis at an angle of 120 degrees.

[0084] The registration module registers the multi-temporal three-dimensional point cloud data of the seawall breakwater block area based on the corner points of the reference object to obtain registered data.

[0085] The displacement calculation module matches the center points of the same breakwater block and calculates the three-dimensional spatial displacement amount based on the registered data and the point cloud data of the single breakwater block to obtain displacement data.

[0086] The contents in the above method embodiments are applicable to the system embodiments. The system embodiments specifically realize the same functions as the above method embodiments and achieve the same beneficial effects as the above method embodiments.

[0087] A seawall breakwater block displacement tracking device comprises:

[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 breakwater block displacement tracking method as described above.

[0091] The contents in the above method embodiments are applicable to the device embodiments. The device embodiments specifically realize the same functions as the above method embodiments and achieve the same beneficial effects as the above method embodiments.

[0092] A storage medium, wherein processor-executable instructions are stored, which, when executed by a processor, are used to implement a seawall breakwater block displacement tracking method as described above.

[0093] The contents in the method embodiments are applicable to the storage medium embodiment. The storage medium embodiment specifically implements the same functions as the method embodiments and achieves the same beneficial effects as the method embodiments.

[0094] The above is a specific description of the preferred embodiments of the present application, but the present application is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application. These equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A method for tracking the displacement of a seawall wave-breaking block, characterized in that: The method comprises the following steps: acquiring three-dimensional point cloud data of a seawall breakwater block region; segmenting the three-dimensional point cloud data according to a preset region to obtain segmented point cloud data; processing the segmented point cloud data based on a three-dimensional geometric model of a breakwater block to extract point cloud data of a single breakwater block; registering the three-dimensional point cloud data of the seawall breakwater block region based on corner points of a reference object to obtain registered data; matching center points of the same breakwater block and calculating coordinate difference values of the breakwater block between different time sequences based on the registered data and the point cloud data of the single breakwater block to obtain displacement data; the expression of the three-dimensional geometric model of the breakwater block is as follows: x 2 +y 2 = (r - cz) 2 where Ω and Φ represent the rotation angles around the X and Y axes, respectively, R1, R2, R3 represent the rotation matrices of the X, Y and Z axes, respectively, q is the order number of the leg of the circular truncated cone, (x c ,y c ,z c ) is the center coordinate point of the wave-absorbing block, (x, y, z) represents the nominal position, r represents the radius of the circular truncated cone at the height of z = 0, and c represents the gradient factor of the circular truncated cone.

2. The method of tracking displacement of a sea wall breakwater block according to claim 1, wherein, further comprising: projecting displacement components of the center points of the breakwater block onto a reference plane to correct x, y and z components through a proportional relationship.

3. The method of tracking displacement of a sea wall breakwater block according to claim 1, wherein, The three-dimensional geometric model of the breakwater block specifically comprises four truncated cones, a central axis of one of the truncated cones coincides with the Z axis, and central axes of the other three truncated cones are symmetrically distributed around the Z axis at an angle of 120 degrees.

4. The method of tracking displacement of a sea wall breakwater block of claim 1, wherein, further comprising: merging residual point cloud data after extracting point cloud of a single breakwater block to obtain outlier data; extracting point cloud data of a single breakwater block according to the outlier data and calculating center coordinates of each breakwater block.

5. The method of tracking displacement of a sea wall breakwater block of claim 1, wherein, The step of segmenting the three-dimensional point cloud data according to a preset region to obtain segmented point cloud data specifically comprises: dividing the three-dimensional point cloud data according to tile regions and introducing a buffer zone at the boundary to obtain segmented point cloud data.

6. The method of tracking displacement of a sea wall breakwater block of claim 4, wherein, The step of registering the three-dimensional point cloud data of the seawall breakwater block region based on corner points of a reference object to obtain registered data specifically comprises: selecting corner points of a fixed building as a reference point set in multi-temporal three-dimensional point cloud data of the seawall breakwater block region; performing rigid transformation based on the corner points of the fixed building using Horn's Method to complete registration; superimposing center point cloud of a single breakwater block.

7. A seawall armor block displacement tracking system characterized by, A device for performing the seawall breakwater block displacement tracking method of claim 1 comprises: a scanning module for acquiring three-dimensional point cloud data of a seawall breakwater block region; a segmentation module for segmenting the three-dimensional point cloud data according to a preset region to obtain segmented point cloud data; a single extraction module for processing the segmented point cloud data based on a three-dimensional geometric model of a breakwater block to extract point cloud data of a single breakwater block; a registration module for registering the three-dimensional point cloud data of the seawall breakwater block region based on corner points of a reference object to obtain registered data; a displacement calculation module for matching center points of the same breakwater block and calculating coordinate difference values of the breakwater block between different time sequences based on the registered data and the point cloud data of the single breakwater block to obtain displacement data.

8. A sea wall breakwater block displacement tracking device, characterized by, comprise: 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 seawall breakwater block displacement tracking method of any one of claims 1-6.

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