Structure level constrained uav photogrammetry tower deformation monitoring method and system

Abstract

The application discloses a structure level constrained unmanned aerial vehicle photogrammetry tower body deformation monitoring method and system, and the method comprises the following steps: collecting unmanned aerial vehicle oblique photogrammetry images of a tower body to be monitored and a surrounding environment thereof, so as to construct a complete tower body three-dimensional model containing multiple structure layers; detecting an interlayer boundary based on the complete tower body three-dimensional model, defining an adjacent two structure layers as one structure layer between the interlayer boundary of the two structure layers, and determining a main wall surface zone of each structure layer; performing robust facade fitting on the main wall surface zone of each structure layer, and constraining the position of each layer facade according to the position of an angle line; for each structure layer, extracting a local axial section and a structure center; establishing a unified offset reference, and calculating and outputting multi-dimensional deformation indexes based on the unified offset reference. The application realizes non-contact, complete coverage and deformation monitoring suitable for high-rise complex tower body scenes, establishes a geometric reference with structure meaning based on overall three-dimensional space data, and comprehensively evaluates the stable, quantifiable and reproducible deformation state of the tower body.

Description

Technical Field

[0001] This invention relates to the field of tower deformation monitoring technology, and in particular to a method and system for monitoring tower deformation using UAV photogrammetry with structural hierarchy constraints. Background Technology

[0002] Towers are an important part of architectural cultural heritage, typically characterized by repetitive layers, regular facades, prominent eaves, and complex local components. Due to factors such as age, material degradation, foundation changes, natural erosion, and human disturbance, some towers may undergo morphological changes over long periods, including overall tilting, interlayer torsion, local bulging, crack expansion, or component displacement, potentially posing stability risks. Therefore, accurately assessing the deformation state of towers is crucial for conducting preservation status assessments, risk identification, conservation and restoration, and long-term digital archiving.

[0003] Traditional methods for monitoring tower deformation rely heavily on manual inspections, total stations, levels, theodolites, and GNSS. These methods require setting up measuring stations on-site, selecting characteristic points, or installing monitoring markers, and judging the tower's deformation based on the coordinate changes of a small number of measuring points. While these methods can achieve high measurement accuracy at local points, they are highly dependent on personnel experience, station setup, and line-of-sight conditions, resulting in low fieldwork efficiency. The placement of monitoring points or markers may disturb the artifact itself, and subsequent re-measurements cannot guarantee observations at the same points. For the upper part of tall towers, eaves, spires, as well as windows, corners, and obstructed areas, close-range and stable observations are difficult, posing operational safety risks and insufficient observation coverage. Furthermore, these methods cannot cover the overall spatial morphology of the tower, and discrete measuring points cannot reflect the continuous spatial morphology of the tower, making it difficult to comprehensively express complex deformation characteristics such as overall tilt, inter-layer torsion, and local bulging.

[0004] 3D laser scanning point cloud analysis typically involves directly acquiring high-density 3D point clouds of the tower surface using a terrestrial laser scanner or mobile scanning equipment. It heavily relies on the spatial coordinate accuracy and density of the point cloud to perform registration, segmentation, cross-section extraction, wall deviation analysis, or centerline estimation of the tower surface, thereby evaluating the tower's geometry and local deformation. Close-range or UAV photogrammetric 3D reconstruction analysis primarily obtains point clouds or mesh models with texture information through multi-view image matching and 3D reconstruction. Its advantages include flexible data acquisition, large coverage, and relatively low cost, making it particularly suitable for image acquisition of tall structures and complex facades. Subsequent tasks typically involve surface measurement, feature point extraction, cross-section analysis, tilt assessment, or comparison of models from different phases based on the reconstructed model.

[0005] While 3D laser scanning and photogrammetry can acquire relatively complete 3D data, providing a data foundation for digital recording and deformation monitoring of the tower, data integrity, model quality, registration accuracy, and post-processing stability are easily affected in complex scenarios such as overhanging eaves, recessed window openings, local damage, obstructions, surface texture differences, and limited high-altitude viewing angles. This can consequently impact the reliability of subsequent geometric analysis results. Furthermore, these methods typically evaluate a specific type of data or local geometric feature, such as point changes, local surface deviations, cross-sectional changes, centerline trends, model differences, or overall tilt, often making it difficult to comprehensively assess the overall tower morphology, local anomalies, and changes between different height segments. Additionally, different methods vary significantly in benchmark establishment, feature selection, data processing workflows, and result expression methods. Existing results are difficult to retest and compare on a unified scale, leading to insufficient comparability and retest stability of multi-period monitoring results, making it difficult to directly serve long-term tower monitoring, risk identification, and protection and repair decisions. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for monitoring tower deformation using UAV photogrammetry with structural hierarchy constraints. This method addresses the shortcomings of existing technologies for monitoring the deformation of tall and complex towers, such as incomplete data coverage, insufficient stability in the analysis of complex structural areas, lack of overall correlation in deformation evaluation, and weak comparability of results from different periods. By establishing a stable and structurally meaningful analytical benchmark, this invention incorporates the overall shape of the tower, local morphological anomalies, and spatial variation relationships between different heights into a unified evaluation framework. This results in intuitive, quantitative, and repeatable deformation monitoring results, providing reliable technical support for long-term tower monitoring, risk identification, and protection and repair decisions.

[0007] In a first aspect, the present invention provides a method for monitoring the deformation of a UAV photogrammetric tower under structural hierarchy constraints, comprising the following steps: UAV oblique photogrammetry images of the tower to be monitored and its surrounding environment are collected to construct a complete three-dimensional model of the tower, including multiple layers. Based on the detection of the interlayer boundary of the complete tower body three-dimensional model, the boundary between two adjacent structural layers is defined as a structural layer, and the main wall band of each structural layer is determined. By performing robust facade fitting on the main wall strips of each structural layer, the position of each floor facade is constrained based on the corner position; For each structural layer, extract the local axial section and structural center; Establish a unified offset benchmark, and calculate and output multi-dimensional deformation indices based on the unified offset benchmark.

[0008] According to the UAV photogrammetry tower deformation monitoring method based on structural hierarchy constraints provided by the present invention, the method for detecting interlayer boundaries based on a complete three-dimensional model of the tower includes any one of the following methods: normal change, curvature change, shared edge of wall and eaves panels, and manual calibration.

[0009] According to the structural hierarchy constraint-based UAV photogrammetry tower deformation monitoring method provided by the present invention, the method for detecting inter-layer boundaries based on a complete three-dimensional model of the tower includes: When using the normal change detection method to detect interlayer boundaries, the inner product of the unit normal and height direction of each triangular facet of the complete tower body three-dimensional model is calculated as the wall eaves discrimination value; facets with discrimination values ​​less than a preset threshold are marked as wall candidate facets, and facets with discrimination values ​​greater than the preset threshold are marked as eaves candidate facets; Search for shared edges between candidate wall panels and candidate eaves panels in the grid topology. Based on the included angle between the two panels on the shared edge, eliminate transition edges with insignificant geometric changes and retain shared edges with significant geometric changes as candidate inter-layer boundaries. A weighted height distribution curve is established based on the midpoint elevation of the candidate edges of the inter-layer boundary. The weight of the candidate edge is determined by the edge length and the difference in wall eaves discrimination value. The longer the edge length and the greater the difference in wall eaves discrimination value, the greater the weight. After smoothing the height distribution curve, significant peak values ​​are extracted. The height corresponding to the peak value is the detected height of the inter-layer boundary of the structural layer, that is, the inter-layer boundary is detected.

[0010] According to the UAV photogrammetry tower deformation monitoring method with structural hierarchy constraints provided by the present invention, the method for determining the main wall band of each structural layer includes: Within each structural layer, non-main wall areas near the interlayer boundary are first removed, and wall areas with continuous geometric shape and gentle normal changes are retained as the main wall zone of that structural layer.

[0011] The method for monitoring tower deformation by UAV photogrammetry with structural hierarchy constraints according to the present invention includes the following steps: robust facade fitting of the main wall sections of each structural layer. Based on the tower's plan shape and the main wall bands of each structural layer, each structural layer is divided into several facade support areas. For the facades of each structural layer, a facade model that varies with height is established, and robust facade fitting is performed using the support points in the main wall bands to determine the facade's direction and position. During the fitting process, the weights of window openings, local depressions, damaged areas, and outliers are reduced, so that the main exterior wall faces play a dominant role in facade estimation.

[0012] The method for monitoring tower deformation by UAV photogrammetry with structural hierarchy constraints according to the present invention includes the following steps: Constraining the position of each floor facade based on the corner position. Angle lines are derived from the spatial intersection lines of adjacent facades. During joint optimization, the distance from a facade point to the corresponding facade, the distance from a section corner point to the intersection line of adjacent facades, and the prior facade parameters are all incorporated into the objective function. This allows for the joint estimation of facade orientation, facade position, and angle line position, so that the facade orientation and position can be corrected based on the angle line position.

[0013] According to the UAV photogrammetry tower deformation monitoring method with structural hierarchy constraints provided by the present invention, the step of extracting a local axial section for each structural layer includes the following steps: The local axial direction of each structural layer is estimated based on the spatial orientation of multiple facades, and multiple local axial sections are arranged with the local axial direction as the normal direction of the section.

[0014] According to the structural hierarchy constraint-based UAV photogrammetry tower deformation monitoring method provided by the present invention, the establishment of a unified offset benchmark includes the following steps: Based on the bottom structural layer, an offset calculation benchmark is established. Each facade of the bottom structural layer is extended to the fitted ground to form a polygonal outline at the ground. The center of the polygonal outline is used as the origin of the plane offset. At the same time, the normal of the fitted ground is used as the height direction to establish a unified tower coordinate system. Based on the established tower coordinate system, the cumulative plane offset and relative height of the structural center of each structural layer and the tower tip relative to the origin of the plane offset are calculated.

[0015] The method for monitoring tower deformation based on structural hierarchy constraints provided by the present invention, wherein the calculation and output of multi-dimensional deformation indices based on a unified offset datum includes the following steps: The overall offset and tilt state of the tower are evaluated based on the offset relationship between the structural center of each structural layer and the offset origin of the tower tip relative to the plane.

[0016] Secondly, the present invention also provides a UAV photogrammetry tower deformation monitoring system with structural hierarchy constraints, comprising: The data acquisition module is used to acquire UAV oblique photogrammetric images of the tower to be monitored and its surrounding environment in order to construct a complete three-dimensional model of the tower, including multiple layers. The interlayer boundary detection and main wall zone determination module is used to detect interlayer boundaries based on the complete tower 3D model, define the space between the interlayer boundaries of two adjacent structural layers as a structural layer, and determine the main wall zone of each structural layer. The facade fitting and corner position constraint module is used to perform robust facade fitting on the main wall strips of each structural layer and constrain the position of each floor facade based on the corner position. The local axial section and structural center extraction module is used to extract the local axial section and structural center for each structural layer. The deformation index calculation module is used to establish a unified offset benchmark, and calculate and output multi-dimensional deformation indices based on the unified offset benchmark.

[0017] Thirdly, the present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the UAV photogrammetry tower deformation monitoring method with structural hierarchy constraints as described above.

[0018] Fourthly, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the UAV photogrammetry tower deformation monitoring method with structural hierarchy constraints as described above.

[0019] The present invention also provides a computer program product, including a computer program that, when executed by a processor, implements a UAV photogrammetry tower deformation monitoring method with structural hierarchy constraints as described above.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a method and system for monitoring tower deformation using UAV photogrammetry with structural hierarchy constraints. By using structural hierarchy constraints centered on inter-layer boundaries, main wall bands, facades, and corners, the complex surfaces in the three-dimensional model of the tower are transformed into geometric benchmarks with structural meaning, reducing the impact of eaves, window openings, obstructions, local damage, and reconstruction noise on feature extraction. Through local axial sections and multi-section center averaging mechanisms, the stability of structural center extraction is improved, avoiding stretching or offset of a single horizontal section in an inclined tower. By jointly expressing multiple indicators such as facade residuals, cumulative offset, tilt, inter-layer torsion, and section stability, the system can simultaneously reflect the overall tilt, continuous torsion, and local morphological anomalies of the tower, elevating the monitoring results from discrete point changes to an overall spatial morphological evaluation. Through a unified offset benchmark and a repeatable geometric extraction process, the system provides a stable technical foundation for comparing multi-period UAV oblique photogrammetry data, establishing long-term monitoring archives, and making protection and repair decisions. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a flowchart illustrating a method for monitoring tower deformation using UAV photogrammetry with structural hierarchy constraints, provided by the present invention. Figure 2 This is a schematic diagram of extracting the center of the tower structure and calculating the offset using a UAV photogrammetry tower deformation monitoring method with structural hierarchy constraints provided by the present invention; Figure 3 This is a schematic diagram of the structure of the electronic device provided by the present invention. Detailed Implementation

[0023] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0024] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] like Figure 1 As shown in the embodiment of the present invention, the method for monitoring the deformation of a UAV photogrammetric tower under structural hierarchy constraints includes the following steps: S1. Collect UAV oblique photogrammetry images of the tower to be monitored and its surrounding environment to construct a complete three-dimensional model of the tower, including multiple layers. S2. Based on the complete three-dimensional model of the tower, detect the inter-layer boundary, define the boundary between two adjacent structural layers as a structural layer, and determine the main wall band of each structural layer; S3. By performing robust facade fitting on the main wall strips of each structural layer, the position of each floor facade is constrained according to the corner position; S4. For each structural layer, extract the local axial section and structural center; S5. Establish a unified offset benchmark, and calculate and output multi-dimensional deformation indices based on the unified offset benchmark.

[0027] This invention utilizes unmanned aerial vehicle (UAV) photogrammetry technology to address existing challenges in deformation monitoring of tall, complex towers, including incomplete data coverage, low fieldwork efficiency, potential disturbance to the artifact during monitoring point or marker placement, and difficulties in ensuring identical observation locations during subsequent re-measurements. Furthermore, for the upper part of tall towers, eaves, spires, windows, corners, and obstructed areas, close-range and stable manual observation is challenging, posing safety risks and insufficient coverage. The invention achieves non-contact, comprehensive, repeatable deformation monitoring applicable to tall, complex tower scenarios.

[0028] Compared to the existing axis-driven method that "first fits the global central axis of the entire tower, and then performs structural layering and tilt evaluation based on this central axis," this invention adopts a structural layer-driven approach: first, it identifies and reconstructs the true structural layers of the tower; then, using the main facades and corners of each layer as constraints, it constructs local geometric benchmarks with structural meaning; finally, it evaluates the deformation of each layer in a unified coordinate system. This method does not require a pre-fitted global central axis of the entire tower as a prerequisite for structural layering, center positioning, and deformation evaluation, nor is it limited by the assumption of a continuous and smooth global central axis. Therefore, it can more stably characterize and identify complex deformations such as interlayer slippage, local abrupt changes, continuous torsion, and surface bulging.

[0029] Leveraging the tower's clear hierarchical structure, repetitive facades, and relatively regular planar shape, inter-layer boundaries, main wall bands, and geometric units of each layer are extracted from the UAV oblique photogrammetry 3D model. This establishes a structured geometric benchmark for the overall morphological analysis of the tower, solving the problem that traditional discrete measurement point or local analysis methods are insufficient to express the overall spatial morphology of the tower. It can reduce the impact of eaves, window openings, obstructions, local damage, and reconstruction noise on feature extraction and improve the stability of analysis in complex structural areas.

[0030] By using a unified offset benchmark and structural center expression, the deformation characteristics of the tower, such as overall offset, tilt state, inter-layer torsion, local surface deviation, and cross-sectional stability, can be comprehensively calculated and expressed. This solves the shortcomings of existing technologies, such as the lack of overall correlation in deformation evaluation and the weak comparability of results from multiple periods. It enables the inclusion of the overall shape of the tower, local anomalies, and the relationship between changes in different heights into the same evaluation system, forming intuitive, quantitative, and repeatable tower deformation monitoring results.

[0031] In step S1 of this embodiment of the invention, oblique photogrammetric images of the tower to be monitored and its surrounding environment are acquired by UAV. The acquisition range of the UAV oblique photogrammetric images includes a planar flight path around the tower and a close-range circling flight path around the tower body, so that the images cover the entire tower, the main facade, the eaves, the spire, and the surrounding ground reference area. After the photogrammetric images are acquired, aerial triangulation, multi-view image matching, and 3D model generation are performed using photogrammetric 3D reconstruction software to obtain a point cloud or triangular mesh model of the tower and its surrounding area. The reconstruction results are then subjected to coordinate unification, tile merging, abnormal surface patch trimming, and local redundancy cleanup to form a complete 3D model of the tower for subsequent geometric analysis.

[0032] In step S2 of this embodiment of the invention, the method for detecting interlayer boundaries based on the complete three-dimensional model of the tower body includes any one of the following: abrupt change in normal direction, abrupt change in curvature, shared edge of wall and eaves panels, and manual calibration.

[0033] Taking the detection of interlayer boundaries using normal mutation as an example, the steps include: After constructing the complete 3D model of the tower, the inner product between the unit normal of each triangular facet of the complete 3D model and the height direction of the complete 3D model is calculated and used as the wall eaves discrimination value; facets with discrimination values ​​less than a preset threshold are marked as wall candidate facets, and facets with discrimination values ​​greater than the preset threshold are marked as eaves candidate facets; Search for shared edges between candidate wall panels and candidate eaves panels in the grid topology. Based on the included angle between the two panels on the shared edge, eliminate transition edges with insignificant geometric changes and retain shared edges with significant geometric changes as candidate inter-layer boundaries. Actual roof eaves are typically distributed continuously at similar heights, resulting in a significant peak in the height statistics of candidate inter-story boundary edges. A weighted height distribution curve is established using the midpoint elevation of these candidate edges. The weight of each candidate edge is determined by its side length and the difference in wall / eave discriminant values; the longer the edge and the greater the difference in wall / eave discriminant values, the greater the weight. After smoothing the height distribution curve, significant peak values ​​are extracted. The height corresponding to these peak values ​​is the detected height of the structural inter-story boundary, indicating that an inter-story boundary has been detected.

[0034] In this embodiment of the invention, a threshold method is used to classify triangular facets. In fact, there is no limitation on the classification method of triangular facets, and clustering or statistical quantile methods can also be used to determine the classification boundary.

[0035] In step S2 of this embodiment of the invention, the method for determining the main wall surface strip of each structural layer includes: A structural layer is defined as the boundary between two adjacent structural layers. Since the upper and lower ends of a structural layer are usually adjacent to eaves, tapering transitions, or other protruding components, and window recesses, local damage, and model noise can cause abrupt changes in surface normals, discontinuous point-surface distributions, or increased local residuals, directly using the entire layer's data for facade fitting can easily lead to fitting results that deviate from the true geometry of the main exterior wall. Within each structural layer, non-main wall areas near the inter-layer boundary are first removed, retaining wall areas with continuous geometry and gentle normal changes. These are designated as the main wall area of ​​that structural layer for subsequent facade fitting, corner constraints, and structural center extraction.

[0036] In this embodiment of the invention, the normal mutation method is used to detect the interlayer boundary. In fact, this is not limited. Curvature mutation, shared edge of wall eaves, or manual calibration can also be used to detect the interlayer boundary.

[0037] In this invention, the layering does not depend on a pre-obtained central axis, which can reduce the propagation of central axis estimation errors to the layering results and reduce interference from eaves, window openings, defects, and uneven point density.

[0038] In step S3 of this embodiment of the invention, robust facade fitting is performed on the main wall strip of each structural layer, and the position of each facade is constrained according to the corner position. Based on the tower's plan shape and the main wall bands of each structural layer, each structural layer is divided into several facade support areas. For the facades of each structural layer, a facade model that varies with height is established, and robust facade fitting is performed using the support points in the main wall bands to determine the facade's direction and position. During the fitting process, the weights of window openings, local depressions, damaged areas, and outliers are reduced, so that the main exterior wall faces play a dominant role in facade estimation.

[0039] Robust facade fitting methods can employ robust least squares, RANSAC, M-estimation, or other outlier-resistant optimization algorithms.

[0040] To improve geometric consistency between adjacent facades, corner lines are not extracted as isolated line segments. Instead, they are derived from the spatial intersection lines of adjacent facades. During joint optimization, the distances from facade points to corresponding facades, the distances from section corner points to the intersection lines of adjacent facades, and prior facade parameters are all incorporated into the objective function. This allows for joint estimation of facade orientation, facade position, and corner line positions, enabling the correction of facade orientation and position based on corner line positions. This process reduces the impact of local noise and component defects on facade orientation and corner positions.

[0041] By leveraging the tower's clear hierarchical structure, repetitive facades, and relatively regular planar shape, we extract inter-layer boundaries, main wall bands, and geometric units of each layer from the UAV oblique photogrammetry 3D model. This establishes a structured geometric benchmark for the overall morphological analysis of the tower, solving the problem that traditional discrete measurement points or local analysis methods are insufficient to express the overall spatial morphology of the tower.

[0042] In step S4 of this embodiment of the invention, for each structural layer, a local axial section and structural center are extracted. After fitting the facades of each floor, structural sections are constructed using adjacent facades and their intersections. For towers with overall tilt or local torsion, directly using horizontal sections may result in stretching or skew in the section shape due to the tower's tilt. Therefore, the local axial direction of each floor is estimated based on the spatial orientation of multiple facades, ensuring that the local axial direction is as consistent as possible with the orientation of each facade of that floor, and multiple local axial sections are arranged using this local axial direction as the normal to the section.

[0043] Each local axial section intersects with each facade to form a corner point. The center of the section can be calculated from the midpoint of the diagonal point or the geometric center of the section. To reduce the possibility of a single section being affected by local structures, occlusion, or model noise, multiple local axial sections are arranged within the same structural layer, and the average result of the centers of multiple local axial sections is taken as the structural center of that layer. By independently estimating the local axis in each layer, the center of the section is calculated using the intersection points of multiple local axial sections with the facade, and the average value is taken as the structural center of the structural layer. This approach does not rely on the assumption of a globally smooth axis, and can better preserve discontinuous deformations such as inter-layer torsion and abrupt displacement, while reducing the center deviation caused by single sections, sparse top point clouds, and local defects.

[0044] The position of the tower tip can be robustly extracted based on points or patches within a certain range at the top of the complete grid.

[0045] By deriving angles and local section centers from the geometric relationships between adjacent facades, the extraction of key geometric features of the tower no longer depends on a single measuring point or local section. This reduces the impact of window openings, eaves, obstructions, local damage, and model noise on the structural feature extraction results, and improves the stability of the deformation analysis benchmark in complex tower scenarios.

[0046] In this embodiment of the invention, an octagonal brick tower is used as an example. The structural center of the structural layer is calculated based on the center of the local axial section. This is an example for illustration. In fact, this is not limited. Equivalent substitutions can be made according to the planar shape of the tower. For quadrilateral, hexagonal or octagonal sections, the intersection of the centroid of the vertex of the section, the center of the area, the midpoint of the line connecting the opposite corner points or the midpoint of the opposite side can be used as the center of the section. For near-circular sections, the center of the section can be obtained by fitting a circle or cylinder. For sections with obvious symmetry, the structural center can be determined by the intersection of the axis of symmetry or the plane of symmetry.

[0047] In step S5 of this embodiment of the invention, a unified offset benchmark is established, and multi-dimensional deformation indexes are calculated and output based on the unified offset benchmark.

[0048] To ensure a unified reference for the deformation results of each structural layer and the tower tip, in this embodiment of the invention, an offset calculation benchmark is established based on the bottom structural layer. Specifically, each facade of the bottom structural layer is extended to the fitted ground surface, forming a polygonal outline at the ground level, with the center of the polygonal outline serving as the origin of the plane offset. Simultaneously, a unified tower coordinate system is established, using the fitted ground normal as the height direction. Based on this established tower coordinate system, the cumulative plane offset and relative height of the structural center of each structural layer and the tower tip relative to the plane offset origin are calculated, and the overall tilt state of the tower is evaluated accordingly.

[0049] Under a unified benchmark, multiple deformation indices are further calculated: the signed distance from the tower body point to the corresponding facade is calculated based on the fitted facade to express local bulging, concavity, and surface morphology deviations; the rotation trend between different height segments is evaluated based on the change of the corner direction of each layer with height; the overall offset and tilt state of the tower is evaluated based on the offset relationship between the structural center of each structural layer and the tower tip relative to the plane offset origin; and the stability of the structural center extraction results is evaluated based on the consistency of the centers of multiple local sections in the same structural layer.

[0050] By using a unified fitting ground benchmark and structural center expression, the deformation characteristics of the tower, such as overall offset, tilt state, inter-layer torsion, local surface deviation and cross-sectional stability, are comprehensively calculated and expressed. The overall shape of the tower, local anomalies and the relationship between different height parts are incorporated into the same evaluation system, forming intuitive, quantitative and repeatable tower deformation monitoring results.

[0051] Deformation evaluation indicators such as curvature, radial deviation, local component displacement, crack spatial location, or multi-stage differential change rate can be added according to actual protection needs.

[0052] Based on the aforementioned structured geometric benchmarks and deformation indices, the monitoring results of the overall tilt, continuous torsion, local surface anomalies, and structural center stability of the tower are output. These results are used to determine the spatial distribution of tower deformation, its main development direction, and the connections between different height segments.

[0053] In the embodiment of the Wenfeng Pagoda in Fenyang, a total of 13 structural layers were extracted using the method disclosed in the embodiments of the present invention. Each layer is described by multiple facades and their derived corner lines, and the spire is robustly extracted from the top area of ​​the model. Figure 2 As shown, the structural center of the tower is extracted using the UAV photogrammetry tower deformation monitoring method with structural hierarchy constraints provided in this embodiment of the invention, and based on the established tower coordinate system ( Figure 2The offset of the structure layer by layer was calculated using the uvz coordinate system. The calculation results show that the tower has complex deformation characteristics such as overall tilt, continuous torsion and abnormal local morphology in the upper part. The cumulative offset of the tower tip is about 1.94m and the tilt is about 1.298°, which is on the same order of magnitude as the existing survey results. This shows that the method can provide effective technical support for tower deformation monitoring and risk identification.

[0054] The structural hierarchy constraint UAV photogrammetry tower deformation monitoring system provided by the present invention will be described below. The structural hierarchy constraint UAV photogrammetry tower deformation monitoring system described below can be referred to in correspondence with the structural hierarchy constraint UAV photogrammetry tower deformation monitoring method described above.

[0055] The structural hierarchy constraint-based UAV photogrammetry tower deformation monitoring system provided by this invention includes: The data acquisition module is used to collect UAV oblique photogrammetric images of the tower to be monitored and its surrounding environment in order to construct a complete three-dimensional model of the tower. The interlayer boundary detection and main wall zone determination module is used to detect interlayer boundaries based on the complete tower 3D model, define the space between the interlayer boundaries of two adjacent structural layers as a structural layer, and determine the main wall zone of each structural layer. The facade fitting and corner position constraint module is used to perform robust facade fitting on the main wall strips of each structural layer and constrain the position of each floor facade based on the corner position. The local axial section and structural center extraction module is used to extract the local axial section and structural center for each structural layer. The deformation index calculation module is used to establish a unified offset benchmark in order to calculate and output the deformation index.

[0056] Figure 3 An example is a schematic diagram of the physical structure of an electronic device, such as... Figure 3 As shown, the electronic device may include: a processor 810, a communication interface 820, a memory 830, and a communication bus 840, wherein the processor 810, the communication interface 820, and the memory 830 communicate with each other via the communication bus 840. The processor 810 can call logical instructions in the memory 830 to execute a UAV photogrammetry tower deformation monitoring method with structural hierarchy constraints, the method including: S1. Collect UAV oblique photogrammetry images of the tower to be monitored and its surrounding environment to construct a complete three-dimensional model of the tower, including multiple layers. S2. Based on the complete three-dimensional model of the tower, detect the inter-layer boundary, define the boundary between two adjacent structural layers as a structural layer, and determine the main wall band of each structural layer; S3. By performing robust facade fitting on the main wall strips of each structural layer, the position of each floor facade is constrained according to the corner position; S4. For each structural layer, extract the local axial section and structural center; S5. Establish a unified offset benchmark, and calculate and output multi-dimensional deformation indices based on the unified offset benchmark.

[0057] Furthermore, the logical instructions in the aforementioned memory 830 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, essentially, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes: USB flash drive, portable hard drive, read-only memory (ROM), etc. Various media that can store program code, such as only memory, random access memory (RAM), magnetic disks or optical disks.

[0058] On the other hand, the present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer is able to execute the UAV photogrammetry tower deformation monitoring method with structural hierarchy constraints provided by the above methods. The method includes: S1. Collect UAV oblique photogrammetry images of the tower to be monitored and its surrounding environment to construct a complete three-dimensional model of the tower, including multiple layers. S2. Based on the complete three-dimensional model of the tower, detect the inter-layer boundary, define the boundary between two adjacent structural layers as a structural layer, and determine the main wall band of each structural layer; S3. By performing robust facade fitting on the main wall strips of each structural layer, the position of each floor facade is constrained according to the corner position; S4. For each structural layer, extract the local axial section and structural center; S5. Establish a unified offset benchmark, and calculate and output multi-dimensional deformation indices based on the unified offset benchmark.

[0059] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a UAV photogrammetry tower deformation monitoring method for performing the structural hierarchy constraints provided by the methods described above, the method comprising: S1. Collect UAV oblique photogrammetry images of the tower to be monitored and its surrounding environment to construct a complete three-dimensional model of the tower, including multiple layers. S2. Based on the complete three-dimensional model of the tower, detect the inter-layer boundary, define the boundary between two adjacent structural layers as a structural layer, and determine the main wall band of each structural layer; S3. By performing robust facade fitting on the main wall strips of each structural layer, the position of each floor facade is constrained according to the corner position; S4. For each structural layer, extract the local axial section and structural center; S5. Establish a unified offset benchmark, and calculate and output multi-dimensional deformation indices based on the unified offset benchmark.

[0060] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0061] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for monitoring the deformation of a UAV photogrammetric tower under structural hierarchy constraints, characterized in that, Includes the following steps: UAV oblique photogrammetry images of the tower to be monitored and its surrounding environment are collected to construct a complete three-dimensional model of the tower, including its multi-layered structure. Based on the detection of the interlayer boundary of the complete tower body three-dimensional model, the boundary between two adjacent structural layers is defined as a structural layer, and the main wall band of each structural layer is determined. By performing robust facade fitting on the main wall strips of each structural layer, the position of each floor facade is constrained based on the corner position; For each structural layer, extract the local axial section and structural center; Establish a unified offset benchmark, and calculate and output multi-dimensional deformation indices based on the unified offset benchmark; The method for detecting interlayer boundaries based on a complete three-dimensional model of the tower includes: When using the normal change detection method to detect interlayer boundaries, the inner product of the unit normal and height direction of each triangular facet of the complete tower body three-dimensional model is calculated and used as the wall eaves discrimination value; Patches with a discrimination value less than a preset threshold are marked as candidate wall patches, and patches with a discrimination value greater than the preset threshold are marked as candidate eaves patches; Search for shared edges between candidate wall panels and candidate eaves panels in the grid topology. Based on the included angle between the two panels on the shared edge, eliminate transition edges with insignificant geometric changes and retain shared edges with significant geometric changes as candidate inter-layer boundaries. A weighted height distribution curve is established based on the midpoint elevation of the candidate edges of the inter-layer boundary. The weight of the candidate edge is determined by the edge length and the difference in wall eaves discrimination value. The longer the edge length and the greater the difference in wall eaves discrimination value, the greater the weight. After smoothing the height distribution curve, significant peak values ​​are extracted. The height corresponding to the peak value is the detected height of the inter-layer boundary of the structural layer, that is, the inter-layer boundary is detected.

2. The method for monitoring the deformation of a UAV photogrammetric tower under structural hierarchy constraints according to claim 1, characterized in that: The method for determining the main wall surface band of each structural layer includes: Within each structural layer, non-main wall areas near the interlayer boundary are first removed, and wall areas with continuous geometric shape and gentle normal changes are retained as the main wall zone of that structural layer.

3. The method for monitoring the deformation of a UAV photogrammetric tower under structural hierarchy constraints according to claim 2, characterized in that: The process of robustly fitting the main wall surfaces of each structural layer includes the following steps: Based on the tower's plan shape and the main wall bands of each structural layer, each structural layer is divided into several facade support areas. For the facades of each structural layer, a facade model that varies with height is established, and robust facade fitting is performed using the support points in the main wall bands to determine the facade's direction and position. During the fitting process, the weights of window openings, local depressions, damaged areas, and outliers are reduced, so that the main exterior wall faces play a dominant role in facade estimation.

4. The method for monitoring the deformation of a UAV photogrammetric tower under structural hierarchy constraints according to claim 3, characterized in that: The method of constraining the position of each floor facade based on the corner position includes the following steps: Angle lines are derived from the spatial intersection lines of adjacent facades. During joint optimization, the distance from a facade point to the corresponding facade, the distance from a section corner point to the intersection line of adjacent facades, and the prior facade parameters are all incorporated into the objective function. This allows for the joint estimation of facade orientation, facade position, and angle line position, so that the facade orientation and position can be corrected based on the angle line position.

5. The method for monitoring the deformation of a UAV photogrammetric tower under structural hierarchy constraints according to claim 4, characterized in that: The step of extracting a local axial section for each structural layer includes the following steps: The local axial direction of each structural layer is estimated based on the spatial orientation of multiple facades, and multiple local axial sections are arranged with the local axial direction as the normal direction of the section.

6. The method for monitoring the deformation of a UAV photogrammetric tower under structural hierarchy constraints according to claim 5, characterized in that: The establishment of a unified offset benchmark includes the following steps: Based on the bottom structural layer, an offset calculation benchmark is established. Each facade of the bottom structural layer is extended to the fitted ground to form a polygonal outline at the ground. The center of the polygonal outline is used as the origin of the plane offset. At the same time, the normal of the fitted ground is used as the height direction to establish a unified tower coordinate system. Based on the established tower coordinate system, the cumulative plane offset and relative height of the structural center of each structural layer and the tower tip relative to the origin of the plane offset are calculated.

7. The method for monitoring the deformation of a UAV photogrammetric tower under structural hierarchy constraints according to claim 6, characterized in that: The calculation and output of multi-dimensional deformation indices based on a unified offset benchmark includes the following steps: The overall offset and tilt state of the tower are evaluated based on the offset relationship between the structural center of each structural layer and the offset origin of the tower tip relative to the plane.

8. A UAV photogrammetry tower deformation monitoring system with structural hierarchy constraints, characterized in that, A UAV photogrammetry tower deformation monitoring method for implementing structural hierarchy constraints as described in any one of claims 1-7, comprising: The data acquisition module is used to acquire UAV oblique photogrammetric images of the tower to be monitored and its surrounding environment in order to construct a complete three-dimensional model of the tower, including multiple layers. The interlayer boundary detection and main wall zone determination module is used to detect interlayer boundaries based on the complete tower 3D model, define the space between the interlayer boundaries of two adjacent structural layers as a structural layer, and determine the main wall zone of each structural layer. The facade fitting and corner position constraint module is used to perform robust facade fitting on the main wall strips of each structural layer and constrain the position of each floor facade based on the corner position. The local axial section and structural center extraction module is used to extract the local axial section and structural center for each structural layer. The deformation index calculation module is used to establish a unified offset benchmark, and calculate and output multi-dimensional deformation indices based on the unified offset benchmark.

Images