High-rise pier column center point measurement method and system based on laser pose correction

Abstract

This invention provides a method and system for measuring the center point of a tall pier based on laser pose correction, belonging to the field of UAV measurement technology. The method includes: a UAV equipped with three non-collinear laser emitters projecting light spots onto the ground; an industrial camera capturing and extracting the center coordinates of the light spots in real time; based on the light spot coordinates and the geometric layout of the emitters on the UAV, constructing and solving a system of equations to calculate the UAV's six-degree-of-freedom pose parameters; using the real-time pose to perform coordinate transformation and Kalman filtering correction on the original measurement values; acquiring multiple height section edge points of the pier and calculating the three-dimensional coordinates of the pier's center point; and pushing the pose parameters and center point coordinates to a tablet for three-dimensional visualization. The system includes a UAV, a ground laser detection device, and a pose calculation and correction module. This invention achieves millimeter-level real-time pose correction at extremely low cost by constructing an external absolute measurement benchmark.

Description

Technical Field

[0001] This invention relates to the field of unmanned aerial vehicle (UAV) measurement technology, specifically to a method and system for measuring the center point of a tall pier based on laser pose correction. Background Technology

[0002] In the construction and operation and maintenance of infrastructure such as bridges, high-speed railways, and highways, tall piers, as core load-bearing components, directly affect the quality of construction, structural safety, and subsequent operation and maintenance decisions through the accuracy of their three-dimensional coordinate measurement. Tall piers are generally characterized by their height (usually exceeding 10 meters), large cross-sectional dimensions, and limited surrounding working space. Traditional manual measurement methods require the erection of scaffolding or the use of climbing equipment, which is not only inefficient and labor-intensive but also poses significant safety hazards for working at heights. Furthermore, the measurement accuracy is easily affected by human error.

[0003] With the development of UAV technology, UAV surveying has gradually replaced traditional manual surveying and become the mainstream method for measuring the center point of tall piers due to its advantages such as convenient operation, high work efficiency, and no need for climbing. However, in existing technologies, UAVs are easily affected by airflow disturbances such as gusts and turbulence when operating at high altitudes, resulting in attitude shifts in three-axis translation (X, Y, Z directions) and three-axis rotation (roll, pitch, yaw). Existing UAV surveying systems lack real-time, accurate attitude correction mechanisms, and these attitude shifts are directly transmitted to the measurement data, causing the measurement error of the pier center point to exceed the allowable range for engineering projects, thus failing to meet the requirements for high-precision measurement.

[0004] Therefore, there is an urgent need for a method and system for measuring the center point of tall piers using unmanned aerial vehicles (UAVs) that can solve the problem of pose deviation caused by high-altitude airflow disturbance, reduce system costs, improve measurement real-time performance and data synchronization, and is easy to operate and can be directly applied to engineering sites. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a method and system for measuring the center point of tall piers based on laser pose correction. This solves the technical problems of pose deviation and large measurement error caused by high-altitude airflow disturbance when measuring the center point of tall piers using existing UAVs. It achieves high-precision, low-cost and real-time measurement of the center point of tall piers, while supporting multi-terminal data synchronization and collaborative operation.

[0006] The solution provided by this invention is a method for measuring the center point of a tall pier based on laser pose correction, which includes: measuring pier data at multiple points in the air using a UAV, acquiring UAV measurement information in real time through a ground calibration device, and fitting and calculating the three-dimensional coordinates of the pier center point.

[0007] Preferably, the UAV is equipped with no fewer than three non-collinear laser emitters, and the UAV's measurement attitude is captured in real time by a ground calibration device. Specifically, this includes: capturing the image of the light spot projected by the laser emitter on the UAV in real time by the ground calibration device, extracting the center coordinates of each light spot, and calculating the UAV's six-degree-of-freedom measurement attitude based on the center coordinates of the light spots.

[0008] Preferably, there are three or more laser emitters, which are rigidly fixed to the drone body, and no three laser emitters are collinear;

[0009] The spacing between adjacent laser emitters is a fixed value. The mounting plane of the laser emitter is parallel to the horizontal plane of the UAV body, and the geometric center of the laser emitter coincides with the center of gravity of the UAV. When there are three, they are distributed in an isosceles triangle; when there are four, they are distributed in a rectangle; when there are five, they are distributed in a regular pentagon; and when there are six, they are distributed in a regular hexagon.

[0010] Preferably, the six-degree-of-freedom measurement attitude of the UAV is calculated based on the coordinates of the light spot center, specifically as follows: Based on the preset fixed coordinates of the laser emitter in the UAV body coordinate system, combined with the real-time coordinates of the laser spot center in the geodetic coordinate system; When there are three laser emitters, the rotation matrix and translation vector between the body coordinate system and the geodetic coordinate system are solved by the least squares method. The rotation matrix is ​​decomposed into roll angle, pitch angle and yaw angle. The three-axis components of the translation vector are the three-axis translation displacements of the UAV. The six-degree-of-freedom pose parameters of the UAV are calculated. The calculation of the parameters satisfies the following coordinate transformation relationship: the ground projection coordinates are equal to the sum of the products of the three-axis translation, the rotation matrix and the preset constant vector of the laser emitter's position in the body, and then superimposed on the product of the projection distance scalar and the laser emission direction vector. Among them, the preset position constant vector of the laser emitter within the machine body is the preset fixed coordinate of the laser emitter in the machine body coordinate system, the three-axis translation is the three-axis displacement component of the origin of the machine body coordinate system relative to the origin of the geodetic coordinate system, the rotation matrix is ​​the rotation transformation parameter of the machine body coordinate system relative to the geodetic coordinate system, the laser emission direction vector is the direction vector of the laser beam emitted by the laser emitter, the projection distance scalar is the straight-line distance from the laser emitter to the ground projection point calculated by the camera's inverse perspective projection, and the ground projection coordinates are the real-time coordinates of the laser spot in the geodetic coordinate system; When the number of laser emitters is greater than three, an overdetermined system of equations is constructed, and the rotation matrix and translation vector are solved by singular value decomposition or Gauss-Newton iteration method. The optimal solution is then sought in the full set of observation points. The optimal solution is to minimize the sum of squared residuals between the calculated ground projection coordinates of all laser emitters and the actual extracted ground projection coordinates. When tall pillars or other obstacles partially block the laser beam, accurate calculation of six degrees of freedom pose can be achieved using only three points.

[0011] Preferably, after the UAV measures the pier data at multiple points in the air, the measurement error correction step is also included: Based on the real-time captured UAV measurement attitude, coordinate system transformation is performed on the original measurement data of the pier column. The installation offset and angle parameters of the airborne measurement module relative to the center of the UAV body are read, and the original measurement data is transformed from the polar coordinate system of the airborne measurement module to the UAV body coordinate system. Combined with the real-time calculated rotation matrix and translation vector, the measurement data in the body coordinate system is transformed to the geodetic coordinate system through the coordinate transformation formula. The Kalman filter algorithm is used to make the optimal estimate of the converted measurement data. The state equation and observation equation of the Kalman filter are initialized, and the estimated value of the pose calculation and the converted measurement data are input in real time. The Kalman gain is calculated and the optimal state estimate is updated to obtain the corrected three-dimensional coordinates of the edge points on the pier surface, thus eliminating the measurement deviation of the UAV pose fluctuation.

[0012] Preferably, the fitting calculation of the three-dimensional coordinates of the center point of the pier column specifically includes: collecting the three-dimensional coordinates of the edge points of the pier column surface from multiple sections of different heights of the same pier column, eliminating measurement gross errors using the 3σ criterion, fitting the center coordinates of each section using the least squares method, and performing mean filtering on the center coordinates of multiple sections to obtain the three-dimensional coordinates of the overall center point of the pier column.

[0013] Preferably, after obtaining the three-dimensional coordinates of the pier center point through fitting, the real-time measured attitude parameters of the UAV and the three-dimensional coordinates of the pier center point are encapsulated into a JSON data packet with millisecond-level timestamps, and transmitted in real time to the ground display terminal through a wireless communication link for three-dimensional visualization and data archiving.

[0014] This invention provides a system for measuring the center point of a tall pier based on laser pose correction, comprising: The drone is rigidly equipped with multiple non-collinearly arranged laser emitters and an airborne measurement module for collecting geometric information of the pier surface. The ground calibration device is set up at a reference position with known geodetic coordinates to capture the image of the light spot projected by the laser emitter in real time, extract the center coordinates of the light spot, and calculate the real-time measurement attitude of the UAV. The coordinate correction and calculation module is connected to the ground calibration device and the airborne measurement module respectively. It is used to correct the pier measurement data based on the real-time attitude measurement of the UAV and to fit and calculate the three-dimensional coordinates of the pier center point. The data communication and display terminal is connected to the coordinate correction and calculation module to receive and display the real-time pose of the UAV and the three-dimensional coordinates of the center point of the pier.

[0015] Preferably, the ground calibration device includes a highly reflective laser receiving plate, a high-definition industrial camera, a signal processing unit, and a data transmission unit; The center of the high-reflectivity laser receiving plate coincides with the ground projection of the center point of the bottom of the pier. A high-definition industrial camera is used to capture laser spot images in real time. The signal processing unit is used to preprocess the spot images and extract the center coordinates of the spot. The data transmission unit is used to transmit the pose monitoring data to the coordinate correction and calculation module in real time.

[0016] The data communication and display control terminal includes at least two tablet devices, one for controlling the drone and the other for data observation and coordinate verification. The visualization software interface includes at least the drone's flight status, real-time curves of pose parameters, three-dimensional coordinates of the pier center point, and three-dimensional model annotations.

[0017] Beneficial effects of this invention: 1. High-precision real-time pose correction: This invention constructs an external absolute measurement benchmark through three rigidly fixed and non-collinear laser emitting ends. The ground device captures the absolute positions of these three laser spots in real time, and directly and in real-time calculates the six-degree-of-freedom pose of the UAV in the geodetic coordinate system through spatial geometric relationships.

[0018] 2. Lightweight algorithm architecture: Unlike the massive point cloud acquisition, storage, and registration processing of LiDAR, this invention only needs to process the two-dimensional coordinates of three discrete laser spots and single-point ranging values, resulting in extremely small data volume. Pose calculation employs analytical methods based on SVD or least squares, ensuring a stable and fast solution process. The three non-collinear points form a plane, providing sufficient geometric constraints for solving the rotation matrix. This allows the system to maintain pose calculation even if a single laser spot is briefly occluded, as long as three spots are still captured, demonstrating extremely high robustness.

[0019] 3. Multi-section fusion strategy: This invention employs multi-height section sampling and mean filtering. Edge points are collected at multiple heights of the pier, and the center of each section is independently fitted. Finally, the overall center point of the pier is obtained through coordinate arithmetic averaging. This strategy not only improves the robustness of the measurement results but also effectively suppresses the interference of local bulges, formwork misalignment, or construction defects on the center positioning.

[0020] 4. End-to-end visualization and multi-terminal collaboration: This invention encapsulates the real-time pose of the UAV, the laser spot trajectory, and the coordinates of the pier center point in JSON format under the same spatiotemporal reference, and pushes them to multiple tablet terminals via a dual-mode WiFi 6 / 5G link. The visualization interface simultaneously renders the UAV's 3D attitude, six-DOF pose curves, and pier BIM model annotations, enabling a parallel operation mode of "pilot control + surveyor verification." All data is appended with millisecond-level timestamps and archived in the cloud, making the measurement process traceable and auditable. Attached Figure Description

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a structural diagram of the measurement method of the present invention; Figure 2 This is a flowchart of the pose calculation and measurement error correction process of the present invention; Figure 3 This is a diagram showing the position structure of the measurement system of the present invention. Detailed Implementation

[0022] To better understand the purpose, system architecture, and functional implementation of this embodiment, the embodiments and features in the embodiments of this application can be combined with each other without conflict. The exemplary embodiments disclosed in this application will be described below with reference to the accompanying drawings, which include specific technical details disclosed in this embodiment to aid understanding; however, these details should be considered exemplary rather than restrictive.

[0023] Example 1 like Figure 1 As shown, the present invention provides a laser pose correction-based method for measuring the center point of a tall bridge pier. This method is applied to the three-dimensional coordinate measurement of the center point of a tall bridge pier 1 (20 meters high, circular cross-section, 1.5 meters in diameter). Specifically, it includes steps S110-S150: S110, three-point laser pose monitoring, industrial camera captures laser spot image, image preprocessing, and uses centroid method to extract the center coordinates of the spot; S120, real-time pose calculation, establish the body coordinate system, and calculate the six degrees of freedom parameters of UAV 2 by receiving the light spot in the geodetic coordinate system and using the least squares method. S130, Measurement error correction: The original measurement data is corrected using the Kalman filter algorithm; S140. Accurate calculation of center points: Through noise reduction, fitting, multi-point sampling and mean processing, the coordinates of the center points of the four heights are finally obtained. S150, data transmission and visualization: Packs data into JSON format and adds a timestamp, then transmits it to a handheld tablet via a soldier's interface to achieve data visualization.

[0024] According to an embodiment of the present invention, in step S110, a six-rotor multi-rotor UAV 2 is selected as the measurement carrier. Three laser emitters are fixedly installed on the belly of the UAV 2. The laser emitters are 532nm green laser emitters with a power of 8mW and a laser spot diameter of 2.5mm. The three laser emitters are arranged in an isosceles triangle, with their installation plane parallel to the horizontal plane of the UAV 2 body and their geometric center coinciding with the center of gravity of the UAV 2. This non-collinear arrangement of the three points ensures that the ground device can capture at least three light spots under any flight attitude, providing the necessary geometric constraints for subsequent pose calculation. A 1m×1m white highly reflective laser receiving plate is laid on the flat ground of the measurement area, with the center of the laser receiving plate coinciding with the projection of the center point of the bottom of the pier 1 onto the ground. Upon activating the ground system, the visual recognition module employs a high-definition industrial camera with a resolution of 1920×1080, coupled with a supplementary lighting module, to capture in real-time images of laser spots projected onto the laser receiving plate from multiple laser emitters. The signal processing module performs grayscale and binarization processing on the laser spot images, extracts the center coordinates of the laser spots using the centroid method, and converts them into real-time projected coordinates in the geodetic coordinate system. The geodetic coordinate system O-XYZ includes an X-axis pointing due north, a Y-axis pointing due east, and a Z-axis perpendicular to the ground and pointing upwards. Simultaneously, it monitors the position and attitude changes of the plane formed by multiple laser spots, generating laser pose monitoring data, which is transmitted in real-time to the pose calculation and coordinate correction algorithm module via the data transmission unit.

[0025] According to an embodiment of the present invention, in step S120, the initial coordinates of the three laser emitters in the UAV 2 body coordinate system O'-X'Y'Z' are rigidly fixed as an isosceles triangle. The origin O' of the UAV 2 body coordinate system coincides with the center of gravity of the UAV 2. The X' axis is parallel to the UAV 2 body forward, the Y' axis is parallel to the UAV 2 body to the right, and the Z' axis is perpendicular to the horizontal surface of the UAV 2 body upward. The pose calculation unit receives the laser pose monitoring data transmitted in step S1 and obtains the real-time projection coordinates A' of the three laser spots in the geodetic coordinate system. B' C' Based on the coordinate transformation relationship, a rotation matrix R and a translation vector T are established between the UAV 2 body coordinate system and the geodetic coordinate system. Since the three points are not collinear, the system of equations has a unique solution. The rotation matrix R and translation vector T are solved using the least squares method. The rotation matrix R describes the three-axis rotational attitude of UAV 2, and the translation vector T describes the three-axis translational displacement of UAV 2. The rotation matrix R is decomposed into roll angle α, pitch angle β, and yaw angle γ. The three components of the translation vector T are the translational displacements in the X, Y, and Z directions, thus obtaining the six-degree-of-freedom pose parameters of UAV 2. The pose calculation frequency is 12Hz, and the real-time pose data is transmitted to the error correction unit.

[0026] According to an embodiment of the present invention, in step S130, the measuring device mounted on the nose of the UAV 2 is activated. The BeiDou / GPS dual-mode positioning module acquires the initial three-dimensional coordinates of the UAV 2 itself, and the laser rangefinder measures the distance and angle between the UAV 2 and the feature points on the surface of the pier 1. Combined with the initial three-dimensional coordinates of the UAV 2, the original measurement data of the feature points on the surface of the pier 1 is calculated using trigonometric functions. The error correction unit receives the real-time pose data output by the pose calculation unit and the original measurement data output by the measuring device, and uses the Kalman filter algorithm for error correction. The state equation and observation equation of the Kalman filter are initialized, and the state equation is shown in equation (1) below: (1); in, Let k be the state vector at time k, containing the three-axis position and three-axis velocity of UAV 2 in the geodetic coordinate system. Here is the state transition matrix. To control the input, This is process noise.

[0027] The observation equation is shown in equation (2) below: (2); in, The original measurement data at time k. For the observation matrix, For measuring noise.

[0028] The Kalman gain is calculated using the real-time input of the estimated value obtained from the pose calculation and the original measurement data, as shown in equation (3) below: (3); in, Let be the covariance matrix at time k-1. To measure the noise variance, The optimal state estimate is updated as shown in equation (4) by transposing the observation matrix: (4); This is the corrected, accurate measurement data, which is used to offset measurement errors caused by upper-level airflow disturbances.

[0029] According to an embodiment of the present invention, in step S140, the center point calculation unit receives the corrected and accurate measurement data output in step S3, and uses the 3σ criterion to filter and denoise the data, removing data points with deviations greater than three times the standard deviation. Since the cross-section of pier 1 is circular, the least squares circular fitting algorithm is used to fit the center coordinates of the circular cross-section based on the corrected feature point coordinates on the surface of pier 1, which are the center point coordinates of pier 1 at that height. The UAV 2 is controlled to collect feature point data at four heights of 5 meters, 10 meters, 15 meters, and 20 meters of pier 1, and the above process is repeated to obtain the center point coordinates at the four heights. The center point coordinates at the four heights are then subjected to mean filtering, and the average values ​​of the X, Y, and Z components are calculated respectively to obtain the final three-dimensional coordinates of the center point of pier 1, which meet the engineering allowable error requirements.

[0030] According to an embodiment of the present invention, in step S150, the pose calculation and coordinate correction algorithm module packages the final three-dimensional coordinates of the center point of pier 1, real-time pose data, corrected precise measurement data, and original measurement data, adds a millisecond-level timestamp, and stores it in the cache unit of the system interface in JSON format. The operator establishes a WiFi 6 communication connection between two tablets and the system interface. The system interface transmits the packaged data to the two tablets in real time via the WiFi 6 communication link, with a transmission delay of 35ms. The visualization software on the tablets parses the received data, displaying in real time the flight trajectory of UAV 2, the changes in laser spot during the measurement process, the real-time curves of the six-degree-of-freedom pose parameters, the three-dimensional coordinate values ​​of the center point of pier 1, and the annotations of the three-dimensional model. One tablet is used to control UAV 2, and the other tablet is used to observe the data and verify the coordinates. Simultaneously, the system interface synchronously transmits all data to the server for data backup, facilitating subsequent querying and traceability.

[0031] Example 2 like Figure 2 As shown, the system is divided into two parallel branches, left and right. The left branch is for pose calculation, which determines the position and attitude of the UAV 2 in space. The right branch is for measurement data conversion, which processes the raw data of the pier 1 obtained by the sensor. It receives the coordinates of at least three laser projection points obtained by the ground vision capture algorithm, presets the constant vector of the laser emitter's position within the UAV, and uses a non-collinear multi-point layout to ensure the uniqueness of the rotation matrix solution.

[0032] When there are three laser emitters, the calculation of the geometric center of the three points during the calculation of the centroid and decentroid coordinates can simplify the separate calculation of the translation vector and rotation matrix. The translation vector and six-degree-of-freedom pose output are calculated by solving the projection equation, as shown in Equation (5) below: (5); in, As a preset constant vector for the position of the laser emitter within the machine body, This refers to the three-axis translation. For rotation matrix, Let be the laser emission direction vector. The projection distance scalar is calculated using inverse perspective projection from the camera. The coordinates are the ground projection coordinates. The above nonlinear equations are solved iteratively using the least squares method. Since the multiple emitted laser points are not collinear, when UAV 2 experiences high-frequency flutter due to airflow disturbances, the non-collinear distribution of these multiple points can be spatially smoothed using geometric constraints to address observation noise, allowing the system to be uniquely determined. Multiple independent angle variables and translation vectors in The horizontal displacement is calculated to achieve accurate calculation of the six-degree-of-freedom pose.

[0033] When the number of laser emitters is expanded to four or more, symmetrical geometric shapes such as rectangles (four points), regular pentagons (five points), or regular hexagons (six points) can be used for distribution. At this time, the number of observation equations exceeds the six degrees of freedom parameters to be solved, forming an overdetermined system of equations. In the transformation between the geodetic coordinate system and the body coordinate system, the number of observation equations exceeds the six degrees of freedom parameters to be solved. Using singular value decomposition (SVD) or the Gauss-Newton iteration method, the optimal solution is sought in the full set of observation points. The objective function is shown in the following equation (6): (6); When the pier 1 or other obstacles partially block the laser beam, accurate six-degree-of-freedom pose calculation can be achieved with only three points. When the number of light spots captured by the ground device is ≥3, the system can still maintain complete pose calculation, avoiding measurement interruption. By least-squares fitting of multi-point observations, random errors caused by laser scattering or camera lens distortion can be effectively offset, further improving the accuracy of single-point pose calculation.

[0034] The right branch performs error correction and calculation through raw data preprocessing. It receives raw data from airborne sensors such as infrared rangefinders. The raw data acquired by the sensors is initially established in the polar coordinates or local coordinate system of the sensors themselves. It reads the physical offset and angle installation parameters of the measurement sensor relative to the center of the UAV2 body and transforms the points in the rangefinder coordinate system to the UAV2 body coordinate system. Combined with the real-time pose data output by the left branch, the body coordinates are transformed into a unified ground geodetic coordinate system using the correction formula, as shown in the following formula (7): (7); in, The original data, This refers to the change in height at multiple points. The pitch angle, The roll angle is calculated by using a multi-point fitting algorithm combined with Kalman filtering smoothing of the corrected vector data to determine the coordinates of the center point of pier 1. The coordinates are then pushed to a tablet terminal in real time for 3D visualization via a 4G / 5G dual-mode communication module or data transmission unit.

[0035] Example 3 This invention provides a laser pose correction-based system for measuring the center point of a tall pier, including a pier 1, a drone 2, and a ground calibration device 3. The ground processing host also includes a pose calculation and coordinate correction algorithm module that communicates with a display control terminal via WiFi 6 or 4G / 5G dual-mode communication links to achieve real-time data transmission and collaborative work. The display terminal also includes a fault alarm module for fault monitoring and alarm.

[0036] The UAV 2 comprises a fuselage, flight control module, power module, multiple laser emitters, and measuring equipment. The fuselage is a six-rotor multi-rotor made of carbon fiber, which is lightweight yet strong, ensuring high-altitude flight stability. The flight control module uses an STM32H743 main control chip, supporting automatic hovering and auto-cruise functions, and can precisely control the UAV 2's flight trajectory, speed, and attitude. The power module uses a 20000mAh lithium battery pack, supporting continuous power supply for 2.5 hours, meeting the needs of long-term operation on engineering sites. Multiple laser emitters are fixedly mounted on the fuselage using bolt connections for easy disassembly and maintenance. The laser emitters are arranged in an isosceles triangle, with the mounting plane parallel to the fuselage's horizontal plane and their geometric center coinciding with the UAV 2's center of gravity. The laser emitters are 532nm green lasers with an emission power of 8mW and a laser spot diameter of 2.5mm, used to project laser beams onto the ground. The measuring equipment is fixedly installed on the machine head, with a distance of 30cm from the laser emitter to avoid laser interference. The measuring equipment includes a Beidou / GPS dual-mode positioning module and a laser rangefinder. The positioning accuracy of the Beidou / GPS dual-mode positioning module is ±2.5mm, and the ranging accuracy of the laser rangefinder is ±0.8mm. The ranging range is 0.5-100 meters, and it is used to obtain the original measurement data of feature points on the surface of the pier.

[0037] The ground calibration device 3 includes a laser receiving board, a visual recognition module, a signal processing module, and a data transmission unit. The laser receiving board is a 1m x 1m white high-reflectivity flat plate made of PVC, with a high-reflectivity coating to enhance the contrast of the laser spot and facilitate capture by the visual recognition module. The bottom of the laser receiving board has anti-slip pads for stable placement. Figure 3 As shown, during the operation of the pier 1, the drone 2 and the ground calibration device 3, because the lower piers in different directions will block part of the laser, at least three laser spots from the multiple laser emitters on the drone 2 are collected on the ground calibration device 3.

[0038] The visual recognition module employs a high-definition industrial camera with a resolution of 1920×1080, paired with an LED supplementary lighting module. The supplementary lighting brightness is adjustable, adapting to different environments such as strong and weak light. The sampling frequency is 12Hz, used for real-time capture of laser spot images. The signal processing module uses an FPGA chip, offering high processing speed. It can quickly perform grayscale and binarization processing on the laser spot images, extract the center coordinates of the laser spot using the centroid method, and convert them into projected coordinates in the geodetic coordinate system. Simultaneously, it monitors the position and attitude changes of a plane formed by at least three laser spots, generating laser pose monitoring data. The data transmission unit uses a WiFi 6 communication module, offering high transmission rate and low latency, used to transmit the laser pose monitoring data to the pose calculation and coordinate correction algorithm module in real time.

[0039] The pose calculation and coordinate correction algorithm module is integrated into the ground processing host, which uses an Intel Core i7 processor, 16GB of memory, and a 512GB hard drive, providing high processing speed to meet real-time data processing requirements. The pose calculation and coordinate correction algorithm module includes a pose calculation unit, an error correction unit, and a center point calculation unit. The pose calculation unit employs a planar feature-based pose calculation algorithm, capable of receiving laser pose monitoring data transmitted from the ground calibration device 3 and calculating the six-degree-of-freedom pose parameters of the UAV 2 in real time. The error correction unit uses a Kalman filter algorithm, capable of receiving real-time pose data output from the pose calculation unit and raw measurement data transmitted from the measurement equipment, correcting the raw measurement data in real time to compensate for errors caused by airflow disturbances. The center point calculation unit can filter and denoise the corrected measurement data (3σ criterion), calculate the three-dimensional coordinates of the pier center point using the least squares circular fitting algorithm, and perform mean filtering on the center point coordinates of multiple heights to obtain the final three-dimensional coordinates of the center point. The pose calculation and coordinate correction algorithm module also has a caching function to temporarily store various types of data to ensure the continuity of data processing.

[0040] The data communication and display control terminal includes a communication module, a server, a display control terminal, and a system interface. The communication module adopts a dual-mode communication module with WiFi 6 and 4G / 5G support, automatically switching communication modes. WiFi 6 communication is used for short-range operations within 500 meters, while 4G / 5G dual-mode communication is used for long-range operations, with a transmission latency of no more than 100ms, ensuring real-time and stable data transmission. The server stores all measurement data, supports data backup, query, and traceability, and can connect to multiple terminal devices simultaneously. The display control terminal uses a 10.5-inch high-definition screen and is equipped with dedicated visualization software. The visualization interface includes a UAV flight status display area, a pose parameter curve display area, a center point coordinate display area, and a 3D model display area. It supports simultaneous connection of multiple tablets, enabling collaborative work by multiple operators. The system interface is a standardized USB 3.0 data interface, supporting data packaging, caching, and transmission, and can connect to external devices for easy data export and report generation.

[0041] The fault alarm module is integrated into the ground processing host and display control terminal, including an audible and visual alarm unit and a fault display unit. When the laser emitter malfunctions, the visual recognition module fails to capture the laser spot, data transmission is interrupted, or the measurement error exceeds the preset range, the fault alarm module issues an audible and visual alarm signal, the alarm light flashes red, and the fault type and location are displayed on the display control terminal, facilitating timely troubleshooting by the operator and ensuring the normal operation of the measurement work.

[0042] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this disclosure can be achieved, and this is not limited herein.

[0043] The specific embodiments described above do not constitute a limitation on the scope of protection of this disclosure. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A method for measuring the center point of a high-rise pier based on laser pose correction, characterized in that, include: The drone (2) measures the data of the pier (1) from multiple points in the air; The UAV (2) is equipped with at least three non-collinear laser emitters. The UAV (2) is measured in real time by a ground calibration device (3) located at a known absolute coordinate position on the ground. The ground calibration device (3) captures the laser spots projected onto the ground by each laser emitter on the UAV (2) in real time, and extracts the center coordinates of each spot in the geodetic coordinate system. Based on the center coordinates of each light spot in the geodetic coordinate system and the preset fixed coordinates of each laser emitter in the UAV (2) body coordinate system, the coordinate transformation equations between the body coordinate system and the geodetic coordinate system are established and solved, and the six-degree-of-freedom pose parameters of the UAV (2) are directly calculated. Using the six-degree-of-freedom pose parameters calculated in real time, the measurement data of the multi-point pier (1) of the UAV (2) are corrected in real time; The three-dimensional coordinates of the center point of the pier (1) were calculated by fitting.

2. The method according to claim 1, wherein the method is characterized in that, include: The UAV (2) acquires relative measurement data between itself and multiple measurement points on the surface of the pier (1); Read the installation offset and angle parameters of the laser emitter at the center of the UAV (2) body, and convert the relative measurement data from the polar coordinate system of the airborne measurement module to the coordinate system of the UAV (2) body; By combining the rotation matrix and translation vector calculated in real time, the measurement data in the body coordinate system is transformed to the geodetic coordinate system through coordinate transformation, and the geodetic coordinate data of multiple measurement points on the surface of the pier (1) after pose correction is obtained.

3. The method according to claim 1, wherein the method is characterized by, The number of laser emitters is three or more, which are rigidly fixed on the body of the UAV (2), and any three laser emitters are not collinear; The distance between adjacent laser emitters is a fixed value. The mounting plane of the laser emitter is parallel to the horizontal plane of the UAV (2) body, and the geometric center of the laser emitter coincides with the center of gravity of the UAV (2). When there are three, they are distributed in an isosceles triangle; when there are four, they are distributed in a rectangle; when there are five, they are distributed in a regular pentagon; and when there are six, they are distributed in a regular hexagon.

4. The method according to claim 1, wherein the method is characterized in that, The six-degree-of-freedom attitude measurement of the UAV (2) is calculated based on the coordinates of the light spot center, specifically as follows: Based on the preset fixed coordinates of the laser emitter in the UAV (2) body coordinate system, combined with the real-time coordinates of the laser spot center in the geodetic coordinate system; When there are three laser emitters, the rotation matrix and translation vector between the body coordinate system and the geodetic coordinate system are solved by the least squares method. The translation vector and the six-degree-of-freedom pose output are calculated by solving the projection equation, as shown in Equation (1) below: (1)； wherein, is a position vector of a preset laser emitting end in the body, is a three-axis translation amount, is a rotation matrix, is a laser emission direction vector, is a projection distance scalar calculated by inverse perspective projection of the camera, is a ground projection coordinate; When the number of laser emitters is greater than three, an overdetermined system of equations is constructed, and the rotation matrix and translation vector are solved by singular value decomposition or Gauss-Newton iteration method. The optimal solution is sought in the full set of observation points. The objective function is shown in equation (2) below: (2)； When the pier (1) or other obstacles partially block the laser beam, the accurate calculation of the six-degree-of-freedom pose can be achieved with only three points.

5. The method according to claim 1, wherein the method is characterized in that, Pose correction includes: using the Kalman filter algorithm to make the optimal estimate of the converted measurement data, initializing the state equation and observation equation of the Kalman filter, inputting the estimated value of pose calculation and the converted measurement data in real time, calculating the Kalman gain and updating the optimal state estimate, obtaining the corrected three-dimensional coordinates of the edge points on the surface of the pier (1), and eliminating the measurement deviation of the pose fluctuation of the UAV (2).

6. The method for measuring the center point of a high-rise pier column based on laser pose correction according to claim 1, characterized in that, The fitting calculation of the three-dimensional coordinates of the center point of the pier (1) includes: collecting the three-dimensional coordinates of the edge points of the surface of the pier (1) for multiple sections of different heights of the same pier (1), eliminating measurement gross errors using the 3σ criterion, fitting the center coordinates of each section using the least squares method, and converting the body coordinates into a unified geodetic coordinate system on the ground using the correction formula, as shown in the following formula (3): (3)； wherein, is the original data, is the multi-point height variation, is the pitch angle, is the roll angle, the center point coordinates of the pier column (1) are calculated by a multi-point fitting algorithm combined with the corrected vector data for Kalman filter smoothing processing.

7. The method according to claim 1, wherein the method is characterized in that, After fitting the three-dimensional coordinates of the center point of the pier (1), the attitude parameters measured by the UAV (2) in real time and the three-dimensional coordinates of the center point of the pier (1) are encapsulated into a JSON data packet with millisecond-level timestamps and transmitted to the ground display terminal in real time through the wireless communication link for three-dimensional visualization and data archiving.

8. A high-rise pylon center point measurement system based on laser pose correction, for performing the measurement method of any one of claims 1-7, characterized in that, include: The drone (2) has multiple non-collinearly arranged laser emitting ends rigidly fixed on it, as well as an airborne measurement module for collecting geometric information of the surface of the pier (1); The ground calibration device (3) is set up at the reference position with known geodetic coordinates to capture the spot image projected by the laser transmitter in real time, extract the center coordinates of the spot, and calculate the real-time measurement attitude of the UAV (2). The coordinate correction and calculation module is connected to the ground calibration device (3) and the airborne measurement module respectively. It is used to measure the attitude correction data of the pier (1) based on the UAV (2) in real time and to fit and calculate the three-dimensional coordinates of the center point of the pier (1). The data communication and display terminal is connected to the coordinate correction and calculation module to receive and display the real-time pose of the UAV (2) and the three-dimensional coordinates of the center point of the pier (1).

9. The system for measuring the center point of a high-rise pier according to claim 8, wherein the system further comprises a laser pointer. The data communication and display control terminal includes at least two tablet devices, one of which is used to control the UAV (2) and the other is used for data observation and coordinate verification. The visualization software interface includes at least the UAV (2) flight status, real-time curve of pose parameters, three-dimensional coordinates of the center point of the pier (1) and three-dimensional model annotation.

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