Airborne sounding laser radar system structure error calibration method and device based on cone-like scanning

Abstract

The invention provides an airborne sounding laser radar system structure error calibration method and device based on similar cone scanning. The method comprises the following steps: establishing a structure error calibration field; establishing a global control coordinate system, and acquiring coordinates of a global control point, a measurement station point, a local control point and the center of a reflector of the airborne sounding laser radar by using a total station; acquiring a slope distance from the center of a reflector to a laser foot point on a laser reflection sticker and a rotation angle of a driving motor based on a laser radar, and acquiring coordinates of the laser foot point by utilizing a total station; based on the displacement and rotation geometrical relationship between the laser scanning reference coordinate system and the global control coordinate system, an error equation is constructed according to the slope distance, the rotation angle of the driving motor and the laser foot point coordinates; and iteratively solving the error equation based on a least square indirect adjustment principle to obtain a structure error value of the airborne depth sounding laser radar system. According to the invention, the measurement quality and reliability of the whole depth sounding system can be significantly improved by accurately obtaining the structure error value of the cone-like scanning type airborne depth sounding laser radar.

Description

Technical Field

[0001] The present invention belongs to the technical field of airborne depth sounding laser radar systems, and in particular relates to a method and device for calibrating structural errors of an airborne depth sounding laser radar system based on quasi-conical scanning. Background Art

[0002] The airborne bathymetric lidar system is an advanced shallow water measurement technology that realizes high-resolution joint measurement of water and land by emitting blue-green band laser pulses and receiving echo signals. The system integrates airborne bathymetric lidar, global navigation satellite system (GNSS) and inertial navigation system (INS), and can quickly obtain high-precision three-dimensional water and land terrain data under complex terrain conditions. It can be widely used in shallow water area topography, environmental monitoring and water conservancy projects. However, as a complex multi-sensor integrated system, the measurement accuracy of the airborne bathymetric lidar system is easily affected by various errors, among which structural error is one of the key factors affecting the overall measurement accuracy of the system. Structural errors mainly come from the processing and assembly deviations of the internal components of the lidar, which will cause distortion of the measurement data and thus affect the accuracy of the water depth calculation. Therefore, effective correction of structural errors is a key step to improve the accuracy of the system, which can not only significantly improve the accuracy of the three-dimensional coordinates of the laser foot points, but also further improve the measurement quality and reliability of the entire bathymetric system.

[0003] In the existing patent literature, most studies focus on the calibration of the system installation angle error. For example, "Geometric correction method and device for installation error of unmanned aerial vehicle radar" (CN114859326A, 2022), "A method for correcting installation angle error based on airborne laser depth sounding system" (CN116299369A, 2023), "Theory and Method of Airborne LiDAR Measurement Technology" (Zhang Xiaohong, 2007, Wuhan University Press), "Calibration method of airborne LiDAR point cloud data without calibration field" (Chen Jie et al., 2015, Remote Sensing of Land and Resources), "Design and verification of airborne LiDAR installation angle calibration calibrator" (Xiao Kai et al., 2017, Journal of Surveying and Mapping Science and Technology), "Research on self-calibration method of domestic spiral scanning laser radar system" (Yang Shujuan et al., 2018, Journal of Electronics and Information), "Calibration method of light and small unmanned aerial vehicle laser radar measurement system" (Tian Lulin et al., 2024, Journal of Information Engineering University).

[0004] In addition, some literatures have discussed the influence of structural errors on measurement accuracy, but they mainly focus on the calibration of system installation angle errors, and lack effective structural error calibration schemes. For example, "Theory and Method of Airborne LiDAR Data Error Processing" (Wang Liying, 2013, Surveying and Mapping Press), "Positioning Model and Accuracy Evaluation of Fixed-angle Conical Scanning Airborne Laser Bathymetry System" (Li Kai et al., 2016, Acta Geodaetica et Cartographica Sinica), "Positioning Model and Simulation Analysis of Circular Scanning Airborne Laser Bathymetry System" (Shen Erhua et al., 2016, China Laser), "Calibration Model and Simulation Analysis of Circular Scanning Airborne Laser Bathymetry System" (Shen Erhua et al., 2016, Acta Geodaetica et Cartographica Sinica), "Research on Structural Error and Positioning Accuracy of Airborne Dual-frequency LiDAR" (Lv Deliang et al., 2018, Progress in Laser and Optoelectronics), "Positioning Model and Analysis of the Influence of Line of Sight Axis Error of Airborne LiDAR Bathymetry System" (Yu Jiayong et al., 2019, Infrared and Laser Engineering).

[0005] At present, among the patents involving structural error calibration, some only calibrate the measured coordinates, and do not clearly give the specific structural error values, such as "Scanning platform coordinate system error correction method based on airborne laser radar system" (CN116990787A, 2023). In addition, although some patents involve the calibration of structural error values, the error values ​​provided are incomplete or not applicable to conical scanning airborne laser radars, such as "A calibration method for the ranging accuracy of airborne laser radar based on circular scanning" (CN111123245A, 2020) and "A method for testing the maximum ranging capability and angular measurement accuracy of airborne laser radar based on circular scanning" (CN111123246A, 2020).

[0006] In summary, the existing patents and research are mostly focused on the calibration of system installation angle errors, while for structural error calibration, especially in the application of conical scanning airborne depth-sounding lidar, the existing calibration schemes fail to effectively solve the calibration problem of structural error values. Summary of the invention

[0007] The purpose of the present invention is to provide a method and device for calibrating the structural error of an airborne depth-sounding lidar system based on quasi-conical scanning, in order to solve the problem of calibrating the structural error value of the quasi-conical scanning airborne depth-sounding lidar, in view of the above-mentioned deficiencies in the prior art.

[0008] To achieve the above object, according to a first aspect of the present invention, the present invention provides a method for calibrating the structural error of an airborne depth-sounding laser radar system based on quasi-conical scanning, comprising:

[0009] Arrange a plurality of global control points, local control points and laser reflective stickers in a target plane of a calibration field, and arrange two measuring stations in the calibration field;

[0010] Establishing a global control coordinate system, and using a total station to obtain the coordinates of the global control point in the global control coordinate system;

[0011] Based on the coordinates of the global control point in the global control coordinate system, the coordinates of the measuring station in the global control coordinate system are obtained by using the resection method and the trigonometric height measurement method;

[0012] Based on the coordinates of the measuring station in the global control coordinate system, the coordinates of the local control point and the center of the airborne depth laser radar reflector in the global control coordinate system are obtained by using the forward intersection method and the trigonometric height measurement method;

[0013] Based on the laser radar, the slant distance from the center of the reflector to the laser foot point on the laser reflector and the rotation angle of the driving motor are obtained;

[0014] Based on the coordinates of the local control point in the global control coordinate system, using a total station to obtain the coordinates of the laser foot point in the global control coordinate system;

[0015] Based on the displacement and rotation geometric relationship between the laser scanning reference coordinate system and the global control coordinate system, an error equation is constructed according to the slant distance, the drive motor angle and the coordinates of the laser foot point in the global control coordinate system;

[0016] Based on the least squares indirect adjustment principle, the error equation is iteratively solved to obtain the structural error value of the airborne bathymetric lidar system.

[0017] In the calibration method of the structural error of the airborne depth-sounding laser radar system based on quasi-conical scanning, a plurality of global control points, local control points and laser reflection stickers are arranged in the target plane of the calibration field, and two measuring stations are arranged in the calibration field, including:

[0018] The target plane of the calibration field is vertical. A point is selected in the target plane to arrange the global control point, which is marked as G0. Multiple global control points (greater than 1) are evenly arranged in the surrounding direction. Multiple rectangular laser reflective stickers (greater than 7) are evenly arranged in the direction around the global control point. A local control point is arranged at the lower left corner and the lower right corner of each laser reflective sticker. A measuring station is arranged on the left and right sides of the horizontal ground in front of the target plane of the calibration field.

[0019] In the method for calibrating the structural error of an airborne depth-sounding laser radar system based on quasi-conical scanning, the establishment of a global control coordinate system and the use of a total station to obtain the coordinates of a global control point in the global control coordinate system include:

[0020] With G0 as the coordinate origin, the horizontal direction as the X axis, the vertical direction as the Y axis, and the Z axis, the X axis, and the Y axis forming a right-handed system, the global control coordinate system is established;

[0021] Mark the first global control point as G1, set up the total station in an open and unobstructed place, mark the center point of the total station as O after leveling, rotate the total station to aim at point G0 for observation, record the horizontal distance S1 and height difference H1 of OG0, set the horizontal circle of the total station to zero, rotate the total station to aim at point G1 for observation, record the horizontal distance S2 of OG1, height difference H2 and the horizontal angle α of G0OG1, and calculate the coordinates of point G1 in the global control coordinate system:

[0022] ;

[0023] The sign depends on G i The position in the global control coordinate system, for example, when G i When in the first quadrant, all values ​​are positive. i When it is in the second quadrant, the x-coordinate takes a negative value and the y-coordinate takes a positive value;

[0024] Similarly, rotate the total station to aim at the other global control points in turn, obtain the horizontal distance, height difference and horizontal angle of each global control point in turn, and substitute them into the above formulas to calculate the coordinates of each global control point in the global control coordinate system.

[0025] In the method for calibrating the structural error of an airborne depth-sounding laser radar system based on quasi-conical scanning, the coordinates of the laser foot points in the global control coordinate system are obtained by using a total station based on the coordinates of the local control points in the global control coordinate system, including:

[0026] Assume that the laser foot point falls on the i-th laser reflector sticker and mark the laser foot point as P i The local control points marking the lower left corner and the lower right corner of the laser reflective sticker are G i1 and G i2 , with G i1 is the origin, G i1 G i2 The X-axis is the direction, and the Y-axis is the direction perpendicular to the X-axis to establish a plane rectangular coordinate system;

[0027] Set up the total station in an open and unobstructed place, level it, mark the center point of the total station as O, turn the total station to aim at G i1 Point observation, record OG i1 Set the horizontal disc of the total station to zero, rotate the total station to aim at P i1 Point observation, record OP i The horizontal distance S2, height difference H2 and Gi1 OP i The horizontal angle α1 is set, and the total station is rotated again to aim at G i2 Point observation, record OG i2 The horizontal distance S3, height difference H3 and G i1 OG i2 The horizontal angle α2;

[0028] Calculate G i1 G i2 distance:

[0029] ;

[0030] Among them, (x Gi1, y Gi1 ) and (x Gi2, y Gi2 ) are G i1 and G i2 x, y coordinates in the global control coordinate system;

[0031] Calculate G i1 P i distance:

[0032] ;

[0033] Calculate P i G i2 distance:

[0034] ;

[0035] according to , and calculate P i G i1 G i2 :

[0036] ;

[0037] according to P i G i1 G i2 Calculate the coordinates of the laser foot point in the plane rectangular coordinate system:

[0038] ;

[0039] Convert the coordinates of the laser foot point in the plane rectangular coordinate system to the global control coordinate system:

[0040] ;

[0041] in, .

[0042] In the method for calibrating the structural error of an airborne depth-sounding laser radar system based on quasi-conical scanning, the displacement and rotation geometric relationship between the laser scanning reference coordinate system and the global control coordinate system is based on the slant distance, the drive motor angle and the coordinates of the laser foot point in the global control coordinate system to construct an error equation, including:

[0043] With the center of the reflector as the origin, the carrier flying direction is the Y-axis direction, the Z-axis is vertically upward, and the X-axis, Y-axis, and Z-axis form a right-hand system, a laser scanning reference coordinate system is established. In theory, the incident laser and the drive motor shaft are in the same plane (XZ plane) and are horizontally incident to the center of the reflector along the negative direction of the X-axis. The laser radar is rotated so that the X, Y, and Z-axis directions of the laser scanning reference coordinate system are the same as the X, Y, and Z-axis directions of the global control coordinate system;

[0044] Let the slant distance of the laser foot point be S, the rotation angle of the drive motor be θ, and the coordinate calculation formula of the laser foot point in the laser reference coordinate system is:

[0045] ;

[0046] Among them, f x 、f y and f z are respectively the calculation formulas of the positioning model of the airborne depth-measuring laser radar taking into account the errors about the x, y and z coordinates, (μ, Δω, Δη, ΔS, Δθ) are structural error parameters, representing respectively the angle between the horizontal incident light and the X-axis, the angle error between the incident light and the drive motor shaft, the angle error between the normal line of the reflector and the drive motor shaft, the laser ranging error and the drive motor angle error;

[0047] Let the coordinates of the center of the reflector in the global control coordinate system be (ΔX, ΔY, ΔZ), and the coordinates of the laser foot point in the global control coordinate system be

[0048] ;

[0049] Where F is the calibration model, with a total of 8 unknown parameters (μ, Δω, Δη, ΔS, Δθ, α, β, γ), R (α, β, γ) is the rotation matrix from the laser scanning reference coordinate system to the global control coordinate system, and the calculation formula is:

[0050] ;

[0051] Among them, (α, β, γ) are the rotation angles around the Y, X, and Z axes respectively;

[0052] The error equation is obtained by linearizing the calibration model:

[0053] ;

[0054] Among them, (X G , Y G , Z G ) is the coordinate of the laser foot point in the global control coordinate system measured by the total station, ((X G ), (Y G ), (Z G )) is the coordinates of the laser foot point in the global control coordinate system obtained by substituting the slant distance, the drive motor angle and the approximate values ​​of the unknown parameters into the calibration model.

[0055] In the error equation constructed based on the displacement and rotation geometric relationship between the laser scanning reference coordinate system and the global control coordinate system, according to the slant distance, the drive motor angle and the coordinates of the laser foot point in the global control coordinate system, the positioning model of the airborne depth laser radar taking into account the error includes:

[0056] Considering that the incident light is horizontally and obliquely incident on the center of the reflector, the direction vector of the incident light in the laser scanning reference coordinate system is

[0057] ;

[0058] Define the angle between the incident light and the drive motor shaft as ω. Considering the angle error between the incident light and the drive motor shaft, rotate the laser scanning reference coordinate system counterclockwise along the Y axis by ω + Δω so that the Z axis coincides with the drive motor shaft, and establish a laser scanning auxiliary coordinate system. The direction vector of the incident light in the laser scanning auxiliary coordinate system is

[0059] ;

[0060] Define the angle between the normal line of the reflector and the rotating shaft of the drive motor as η. Considering the angle error between the normal line of the reflector and the rotating shaft of the drive motor and the zeroing error of the rotating angle of the drive motor, the direction vector of the normal line of the reflector in the laser scanning auxiliary coordinate system is

[0061] ;

[0062] A in By rotating 180° around N in the opposite direction, the direction vector of the reflected light in the laser scanning auxiliary coordinate system can be obtained:

[0063] ;

[0064] A out Rotate ω + Δω clockwise along the Y axis to obtain the direction vector of the reflected light in the laser scanning reference coordinate system:

[0065] ;

[0066] The propagation speed of light in the air is defined as c, and the propagation time from the laser to the center of the reflector to the laser foot point obtained by waveform detection is Δt. Considering the laser ranging error, the propagation slant distance of the laser in the air is:

[0067] ;

[0068] In summary, the coordinates of the laser foot point in the laser scanning reference coordinate system are:

[0069] ;

[0070] In the method for calibrating the structural error of an airborne bathymetric laser radar system based on quasi-conical scanning, the error equation is iteratively solved based on the least squares indirect adjustment principle to obtain the structural error value of the airborne bathymetric laser radar system, including:

[0071] The error equation is written in matrix form:

[0072] ;

[0073] in, ;

[0074] Assuming there are n laser foot points, then

[0075] ;

[0076] Among them, i represents the i-th laser foot point, and for each laser foot point, there is

[0077] ;

[0078] ;

[0079] ;

[0080] Based on the least squares indirect adjustment principle, the normal equation of the error equation is listed as follows:

[0081] ;

[0082] Solving the above formula we get:

[0083] ;

[0084] The coordinates (X) of the laser foot point measured by the total station in the global control coordinate system G , Y G , Z G ), the slant distance S, the driving motor rotation angle θ, and the approximate values ​​of the parameters to be determined (μ, Δω, Δη, ΔS, Δθ, α, β, γ) are substituted into the above formula to calculate the correction number of each parameter to be determined ( );

[0085] according to( ), update the pending parameters:

[0086] ;

[0087] ;

[0088] ;

[0089] ;

[0090] ;

[0091] ;

[0092] ;

[0093] ;

[0094] The coordinates (X G ), (Y G ), (Z G )), then recalculate B and L, and then solve the error equation based on the least squares indirect adjustment principle to obtain the correction number of each of the unknown parameters ( ), and then update each of the pending parameters again, and repeat this step until the absolute values ​​of the correction numbers of all the pending parameters are less than 0.001.

[0095] The present invention also provides a device for calibrating the structural error of an airborne depth-sounding laser radar system based on quasi-conical scanning, comprising:

[0096] A first layout module is used to layout a plurality of global control points, local control points and laser reflective stickers in a target plane of a calibration field, and to layout two measuring stations in the calibration field;

[0097] A second deployment module is used to deploy an airborne depth-measuring laser radar and a total station in the calibration field;

[0098] A first acquisition module, used to acquire the coordinates of the global control point in the global control coordinate system;

[0099] A second acquisition module is used to acquire the coordinates of the measuring station in the global control coordinate system;

[0100] A third acquisition module is used to obtain the coordinates of the local control point and the center of the laser radar reflector in the global control coordinate system;

[0101] A fourth acquisition module is used to obtain the slant distance from the center of the laser radar reflector to the laser foot point on the laser reflector and the driving motor rotation angle;

[0102] A fifth acquisition module, used to acquire the coordinates of the laser foot point in the global control coordinate system;

[0103] Building blocks for building error equations;

[0104] The calculation module is used to solve the error equation to obtain the structural error value of the airborne depth sounding laser radar system.

[0105] Compared with the prior art, the present invention has the following beneficial effects: First, the present invention proposes a calibration field construction scheme suitable for structural error calibration, including multiple global control points, local control points, laser reflective stickers and two measuring stations. Secondly, the present invention proposes a cone-scanning airborne depth-sounding laser radar positioning model that takes into account errors. The model comprehensively considers five types of key structural errors, including the deflection angle error of the incident light, the angle error between the incident light and the drive motor shaft, the angle error between the normal of the reflector and the drive motor shaft, the laser ranging error and the drive motor angle error, and derives an accurate calibration model based on this, and then constructs an error equation. Finally, the least squares indirect adjustment is used to iteratively solve the error equation to accurately obtain the structural error value. By effectively correcting these structural errors, the accuracy of the three-dimensional coordinates of the laser foot point can be significantly improved, thereby improving the measurement quality and reliability of the entire depth-sounding system. BRIEF DESCRIPTION OF THE DRAWINGS

[0106] Figure 1 It is a technical flow chart of the method of the present invention;

[0107] Figure 2 This is a schematic diagram of the inspection and calibration field;

[0108] Figure 3 It is a schematic diagram of the global control coordinate system;

[0109] Figure 4 is the coordinate distribution map of local control points;

[0110] Figure 5 It is a schematic diagram of a plane rectangular coordinate system;

[0111] Figure 6 It is a diagram of the iterative solution process of the error equation;

[0112] Figure 7 This is the coordinate distribution diagram of the laser foot points before and after structural error correction;

[0113] Figure 8 Coordinate error diagram before and after structural error correction;

[0114] Fig. 9 It is a schematic diagram of the device of the present invention. DETAILED DESCRIPTION

[0115] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0116] The measurement errors of airborne bathymetric lidar systems are mainly divided into system integration errors and single-machine errors. System integration errors mainly include the placement angle errors of airborne bathymetric lidar and INS, and the eccentricity errors of lidar and GNSS. Single-machine errors mainly refer to the errors of lidar, INS, and GNSS themselves. Among them, the structural errors caused by the processing and assembly deviations of internal components of lidar are the main source of single-machine errors. System integration errors can be corrected through flight calibration, while structural errors cannot be eliminated through flight dynamic calibration and must be ground statically calibrated before flight. Calibration of structural errors can not only evaluate the quality of the equipment, but also correct system errors in subsequent data processing, significantly improving the accuracy of the three-dimensional coordinates of the laser foot points, thereby improving the measurement quality and reliability of the entire bathymetric system.

[0117] Embodiment 1:

[0118] Combination Figure 1 The present invention provides a method for calibrating the structural error of an airborne depth-sounding laser radar system based on quasi-conical scanning, which includes:

[0119] S1: Multiple global control points, local control points and laser reflectors are arranged in the target plane of the calibration field, and two measuring stations are arranged in the calibration field;

[0120] S2: Establish a global control coordinate system and use the total station to obtain the coordinates of the global control points in the global control coordinate system;

[0121] S3: Based on the coordinates of the global control points in the global control coordinate system, the coordinates of the measuring station in the global control coordinate system are obtained by using the back intersection method and the trigonometric height measurement method;

[0122] S4: Based on the coordinates of the measuring station in the global control coordinate system, the coordinates of the local control point and the center of the airborne depth laser radar reflector in the global control coordinate system are obtained by using the forward intersection method and trigonometric height measurement method;

[0123] S5: Obtain the slant distance from the center of the reflector to the laser foot point on the laser reflector sticker and the driving motor rotation angle based on the laser radar;

[0124] S6: Based on the coordinates of the local control points in the global control coordinate system, the coordinates of the laser foot points in the global control coordinate system are obtained using the total station;

[0125] S7: Based on the displacement and rotation geometric relationship between the laser scanning reference coordinate system and the global control coordinate system, the error equation is constructed according to the slant distance, the drive motor angle and the coordinates of the laser foot point in the global control coordinate system;

[0126] S8: Based on the principle of least squares indirect adjustment, the error equation is iteratively solved to obtain the structural error value of the airborne bathymetric lidar system.

[0127] S1 specifically includes:

[0128] Combination Figure 2Explain the calibration field. There is a vertical target plane in the calibration field. A global control point is selected in the target plane and marked as G0. Multiple global control points (greater than 1) are evenly arranged in the direction around it. A total station reflector is posted on each global control point. Multiple rectangular laser reflectors (greater than 7) are evenly arranged in the direction around the global control point. A local control point is arranged at the lower left corner and the lower right corner of each laser reflector. A total station reflector is posted on each local control point. A measuring station is arranged on the left and right sides of the horizontal ground in front of the target plane of the calibration field to place the total station. The number of global control points should be more than 2 to ensure the accuracy of the rear intersection. The error equation has 8 undetermined parameters and more than 7 equations need to be listed. Therefore, the number of laser reflectors should be greater than 7 to obtain more than 7 laser foot point data. Since the scanning mode of the laser radar is quasi-conical scanning and the scanning trajectory is quasi-elliptical, the layout of the laser reflector should be close to the quasi-ellipse so that the laser scanning trajectory falls evenly on the laser reflector.

[0129] For example, the calibration field constructed in this embodiment is equipped with 5 global control points, 14 laser reflectors, 28 local control points and 2 measuring stations.

[0130] S2 specifically includes:

[0131] With G0 as the coordinate origin, the horizontal direction as the X axis, the vertical direction as the Y axis, and the Z axis forming a right-hand system with the X and Y axes, a global control coordinate system is established. Mark the first global control point as G1, set up the total station in an open and unobstructed place, mark the center point of the total station as O after leveling, rotate the total station to aim at point G0 for observation, record the horizontal distance S1 and height difference H1 of OG0, set the horizontal disk of the total station to zero, rotate the total station to aim at point G1 for observation, record the horizontal distance S2 of OG1, height difference H2 and the horizontal angle α of G0OG1, and calculate the coordinates of point G1 in the global control coordinate system:

[0132] ;

[0133] The sign depends on G i The position in the global control coordinate system, for example, when G i When in the first quadrant, all values ​​are positive. i When in the second quadrant, the x-coordinate takes a negative value and the y-coordinate takes a positive value.

[0134] Similarly, rotate the total station to aim at other global control points in turn, obtain the horizontal distance, height difference and horizontal angle of each global control point in turn, and substitute them into the above formulas to calculate the coordinates of each global control point in the global control coordinate system.

[0135] For example, combined with Figure 3The global control coordinate system established in this embodiment is described, where the X-axis is horizontal to the left, the Y-axis is vertically downward, and the Z-axis is perpendicular to the target plane and forward. The coordinates of each global control point are shown in Table 1.

[0136] Table 1 (Unit: m)

[0137] Serial number x y z <![CDATA[G0]]> 0 0 0 <![CDATA[G1]]> -0.962 -0.010 0 <![CDATA[G2]]> 0 0.652 0 <![CDATA[G3]]> 0.963 -0.013 0 <![CDATA[G4]]> 0 -0.661 0

[0138] S3 specifically includes:

[0139] First, set up the total station at the Z1 position of the survey station. After centering and leveling, based on the x and z coordinates of the global control point in the global control coordinate system, use the back intersection method to obtain the plane coordinates (x and z coordinates) of the Z1 survey station in the global control coordinate system. Then, based on the y coordinate of the global control point G0, use the trigonometric height measurement method to obtain the y coordinate of the Z1 survey station in the global control coordinate system. Similarly, obtain the coordinates of the Z2 survey station in the global control coordinate system.

[0140] For example, the coordinates of each station point in this embodiment are shown in Table 2.

[0141] Table 2 (Unit: m)

[0142] Serial number x y z <![CDATA[Z1]]> -2.296 1.916 5.271 <![CDATA[Z2]]> 2.737 1.892 5.317

[0143] S4 specifically includes:

[0144] First, based on the x and z coordinates of the measuring stations Z1 and Z2 in the global control coordinate system, the x and z coordinates of the local control points and the center of the airborne depth-sounding laser radar reflector in the global control coordinate system are obtained in turn by the forward intersection method. Then, based on the y coordinate of the measuring station Z2, the y coordinates of the local control points and the center of the laser radar reflector in the global control coordinate system are obtained in turn by the trigonometric height measurement method.

[0145] For example, combined with Figure 4 The coordinate distribution of the local control points in this embodiment is described. There are 28 local control points in total, and their overall distribution is elliptical.

[0146] S5 specifically includes:

[0147] Turn off the laser radar's transceiver and mirror scanning device, manually rotate the reflector, and turn on the transceiver when the laser foot point falls on the laser reflector sticker, collect waveform data and perform waveform detection to obtain the laser propagation slant distance. At the same time, record the drive motor angle and mark the position of the laser foot point. Continue to rotate the reflector so that the laser foot point falls on each laser reflector sticker in turn, obtain the slant distance and drive motor angle of each laser foot point in turn, and mark them.

[0148] S6 specifically includes:

[0149] Assume that the laser foot point falls on the i-th laser reflector sticker and mark the laser foot point as P i The local control points of the lower left and lower right corners of the laser reflective sticker are G i1 and G i2 . Combined Figure 5 Describe the plane rectangular coordinate system, with G i1 is the origin, G i1 G i2 The X-axis is the direction, and the Y-axis is the direction perpendicular to the X-axis to establish a plane rectangular coordinate system.

[0150] Set up the total station in an open and unobstructed place, level it, mark the center point of the total station as O, turn the total station to aim at G i1 Point observation, record OG i1 Set the horizontal disc of the total station to zero, rotate the total station to aim at P i1 Point observation, record OP i The horizontal distance S2, height difference H2 and G i1 OP i The horizontal angle α1 is set, and the total station is rotated again to aim at G i2 Point observation, record OG i2 The horizontal distance S3, height difference H3 and G i1 OG i2 The horizontal angle α2.

[0151] Calculate G i1 G i2 distance:

[0152] ;

[0153] Among them, (x Gi1, y Gi1 ) and (x Gi2, y Gi2 ) are G i1 and G i2 The x, y coordinates in the global control coordinate system.

[0154] Calculate G i1 P i distance:

[0155] .

[0156] Calculate P i G i2 distance:

[0157] .

[0158] according to , and Calculate ∠Pi G i1 G i2 :

[0159] .

[0160] According to ∠P i G i1 G i2 Calculate the coordinates of the laser foot point in the plane rectangular coordinate system:

[0161] .

[0162] Convert the coordinates of the laser foot point in the plane rectangular coordinate system to the global control coordinate system:

[0163] ;

[0164] in, .

[0165] S7 specifically includes:

[0166] With the center of the reflector as the origin, the carrier flying direction is the Y-axis direction, the Z-axis is vertically upward, and the X-axis, Y-axis and Z-axis form a right-hand system to establish a laser scanning reference coordinate system. In theory, the incident laser and the drive motor shaft are in the same plane (XZ plane) and are horizontally incident to the center of the reflector along the negative direction of the X-axis. The laser radar is rotated so that the X, Y, and Z-axis directions of the laser scanning reference coordinate system are the same as the X, Y, and Z-axis directions of the global control coordinate system.

[0167] Let the slant distance of the laser foot point be S, the rotation angle of the drive motor be θ, (μ, Δω, Δη, ΔS, Δθ) are the structural error parameters, representing the angle between the horizontal incident light and the X-axis, the angle error between the incident light and the drive motor shaft, the angle error between the normal of the reflector and the drive motor shaft, the laser ranging error and the drive motor angle error. Considering that the incident light is horizontally incident at an angle to the center of the reflector, the direction vector of the incident light in the laser scanning reference coordinate system is

[0168] .

[0169] Define the angle between the incident light and the drive motor shaft as ω. Considering the angle error between the incident light and the drive motor shaft, rotate the laser scanning reference coordinate system counterclockwise along the Y axis by ω + Δω so that the Z axis coincides with the drive motor shaft. Establish the laser scanning auxiliary coordinate system. The direction vector of the incident light in the laser scanning auxiliary coordinate system is

[0170] .

[0171] Define the angle between the normal line of the reflector and the rotating shaft of the drive motor as η. Considering the angle error between the normal line of the reflector and the rotating shaft of the drive motor and the zero error of the rotating angle of the drive motor, the direction vector of the normal line of the reflector in the laser scanning auxiliary coordinate system is

[0172] .

[0173] A in By rotating 180° around N in the opposite direction, we can get the direction vector of the reflected light in the laser scanning auxiliary coordinate system:

[0174] .

[0175] A out Rotate ω + Δω clockwise along the Y axis to obtain the direction vector of the reflected light in the laser scanning reference coordinate system:

[0176] .

[0177] Define the propagation speed of light in the air as c, and the propagation time from the laser to the center of the reflector to the laser foot point obtained by waveform detection as Δt. Considering the laser ranging error, the propagation slant distance of the laser in the air is:

[0178] .

[0179] In summary, the coordinates of the laser foot point in the laser scanning reference coordinate system are:

[0180] .

[0181] Among them, f x 、f y and f z They are the calculation formulas for the x, y and z coordinates of the positioning model taking into account the errors of the airborne bathymetric lidar.

[0182] Let the coordinates of the center of the reflector in the global control coordinate system be (ΔX, ΔY, ΔZ), and the coordinates of the laser foot point in the global control coordinate system be

[0183] ;

[0184] Where F is the calibration model, with a total of 8 unknown parameters (μ, Δω, Δη, ΔS, Δθ, α, β, γ), and R (α, β, γ) is the rotation matrix from the laser scanning reference coordinate system to the global control coordinate system, and the calculation formula is:

[0185] ;

[0186] Among them, (α, β, γ) are the rotation angles around the Y, X, and Z axes respectively.

[0187] Linearizing the calibration model yields the error equation:

[0188] ;

[0189] Among them, (X G , Y G , Z G ) is the coordinate of the laser foot point measured by the total station in the global control coordinate system, ((X G ), (Y G ), (Z G )) is the coordinate of the laser foot point in the global control coordinate system obtained by substituting the approximate values ​​of the slant distance, the driving motor angle and each unknown parameter into the calibration model.

[0190] S8 specifically includes:

[0191] The error equation can be written in matrix form:

[0192] ;

[0193] in, .

[0194] Assuming there are n laser foot points, then

[0195] ;

[0196] Among them, i represents the i-th laser foot point, and for each laser foot point,

[0197] ;

[0198] ;

[0199] .

[0200] Based on the principle of least squares indirect adjustment, the normal equation of the error equation is listed:

[0201] .

[0202] Solving the above formula we get:

[0203] .

[0204] The coordinates (X G , Y G , Z G), the slant distance S, the drive motor angle θ, and the approximate values ​​of the unknown parameters (μ, Δω, Δη, ΔS, Δθ, α, β, γ) are substituted into the above formula to calculate the correction number of each unknown parameter ( ).

[0205] according to( ), update the pending parameters:

[0206] ;

[0207] ;

[0208] ;

[0209] ;

[0210] ;

[0211] ;

[0212] ;

[0213] .

[0214] Recalculate the coordinates of the laser foot point in the global control coordinate system ((X G ), (Y G ), (Z G )), then recalculate B and L, and then solve the error equation based on the least squares indirect adjustment principle to obtain the correction number of each unknown parameter ( ), and then update each pending parameter again, and repeat this step until the absolute values ​​of the correction numbers of all pending parameters are less than 0.001.

[0215] For example, combined with Figure 6 The iterative solution process of the error equation is described. After 17 iterations, the absolute values ​​of the correction numbers of each undetermined parameter have converged to less than 0.001. The initial and final values ​​of each undetermined parameter are shown in Table 3. Figure 7 and Figure 8 The structural error calibration results show that the laser foot point coordinates obtained by the lidar measurement after calibration are closer to the coordinates obtained by the total station measurement (real laser foot point coordinates) than before calibration, and the calculation errors of the x, y, and z coordinates are significantly reduced. The average absolute errors before and after calibration are 0.144 m and 0.025 m, respectively, and the error decreases by 82.814%.

[0216] Table 3

[0217] parameter μ Δω Δη ΔS Initial Value 0° 0° 0° 0 m Final Value 0.076° -0.7475° -0.311° 0.088 m parameter Δθ α β γ Initial Value 0° -3.500° 2.500° 0° Final Value -1.865° -3.678° 2.565° 0.332°

[0218] Embodiment 2:

[0219] Combination Fig. 9 The present invention provides a device for calibrating the structural error of an airborne depth-measuring laser radar system based on quasi-conical scanning, comprising:

[0220] M1: The first layout module is used to layout multiple global control points, local control points and laser reflective stickers in the target plane of the calibration field, and to layout two measuring stations in the calibration field;

[0221] M2: The second deployment module is used to deploy airborne bathymetric lidar and total station in the calibration field;

[0222] M3: a first acquisition module, used to obtain the coordinates of the global control point in the global control coordinate system;

[0223] M4: The second acquisition module is used to obtain the coordinates of the measuring station in the global control coordinate system;

[0224] M5: The third acquisition module is used to obtain the coordinates of the local control point and the center of the laser radar reflector in the global control coordinate system;

[0225] M6: The fourth acquisition module is used to obtain the slant distance from the center of the laser radar reflector to the laser foot point on the laser reflector sticker and the driving motor angle;

[0226] M7: The fifth acquisition module is used to obtain the coordinates of the laser foot point in the global control coordinate system;

[0227] M8: building module, used to build the error equation;

[0228] M9: Calculation module, used to solve the error equation and obtain the structural error value of the airborne depth-sounding lidar system.

[0229] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in this application should be included in the protection scope of the present invention.

Claims

1. A method for calibrating the structural error of an airborne depth-sounding laser radar system based on quasi-conical scanning, characterized in that: The method comprises: Arrange a plurality of global control points, local control points and laser reflective stickers in a target plane of a calibration field, and arrange two measuring stations in the calibration field; Establishing a global control coordinate system, and using a total station to obtain the coordinates of the global control point in the global control coordinate system; Based on the coordinates of the global control point in the global control coordinate system, the coordinates of the measuring station in the global control coordinate system are obtained by using the resection method and the trigonometric height measurement method; Based on the coordinates of the measuring station in the global control coordinate system, the coordinates of the local control point and the center of the airborne depth laser radar reflector in the global control coordinate system are obtained by using the forward intersection method and the trigonometric height measurement method; Based on the laser radar, the slant distance from the center of the reflector to the laser foot point on the laser reflector and the rotation angle of the driving motor are obtained; Based on the coordinates of the local control point in the global control coordinate system, using a total station to obtain the coordinates of the laser foot point in the global control coordinate system; Based on the displacement and rotation geometric relationship between the laser scanning reference coordinate system and the global control coordinate system, an error equation is constructed according to the slant distance, the drive motor angle and the coordinates of the laser foot point in the global control coordinate system; Based on the least squares indirect adjustment principle, the error equation is iteratively solved to obtain the structural error value of the airborne bathymetric lidar system.

2. The method for calibrating the structural error of an airborne depth-sounding laser radar system based on quasi-conical scanning according to claim 1, characterized in that: The method comprises: arranging a plurality of global control points, local control points and laser reflective stickers in the target plane of the calibration field, and arranging two measuring stations in the calibration field, including: The target plane of the calibration field is vertical. A point is selected in the target plane to arrange the global control point, which is marked as G0. Multiple global control points (greater than 1) are evenly arranged in the surrounding direction. Multiple rectangular laser reflective stickers (greater than 7) are evenly arranged in the direction around the global control point. A local control point is arranged at the lower left corner and the lower right corner of each laser reflective sticker. A measuring station is arranged on the left and right sides of the horizontal ground in front of the target plane of the calibration field.

3. The method for calibrating the structural error of an airborne depth-sounding laser radar system based on quasi-conical scanning according to claim 1, characterized in that: The step of establishing a global control coordinate system and obtaining the coordinates of the global control points in the global control coordinate system by using a total station includes: With G0 as the coordinate origin, the horizontal direction as the X axis, the vertical direction as the Y axis, and the Z axis, the X axis, and the Y axis forming a right-hand system, the global control coordinate system is established; Mark the first global control point as G1, set up the total station in an open and unobstructed place, mark the center point of the total station as O after leveling, rotate the total station to aim at point G0 for observation, record the horizontal distance S1 and height difference H1 of OG0, set the horizontal circle of the total station to zero, rotate the total station to aim at point G1 for observation, record the horizontal distance S2 of OG1, height difference H2 and the horizontal angle α of G0OG1, and calculate the coordinates of point G1 in the global control coordinate system: ； The sign depends on G i The position in the global control coordinate system, for example, when G i When it is in the first quadrant, it takes positive values. i When it is in the second quadrant, the x-coordinate takes a negative value and the y-coordinate takes a positive value; Similarly, rotate the total station to aim at the other global control points in turn, obtain the horizontal distance, height difference and horizontal angle of each global control point in turn, and substitute them into the above formulas to calculate the coordinates of each global control point in the global control coordinate system.

4. The method for calibrating the structural error of an airborne depth-sounding laser radar system based on quasi-conical scanning according to claim 1, characterized in that: The method of acquiring the coordinates of the laser foot point in the global control coordinate system by using a total station based on the coordinates of the local control point in the global control coordinate system comprises: Assume that the laser foot point falls on the i-th laser reflector sticker and mark the laser foot point as P i The local control points marking the lower left corner and the lower right corner of the laser reflective sticker are G i1 and G i2 , with G i1 is the origin, G i1 G i2 The X-axis is the direction, and the Y-axis is the direction perpendicular to the X-axis to establish a plane rectangular coordinate system; Set up the total station in an open and unobstructed place, level it, mark the center point of the total station as O, turn the total station to aim at G i1 Point observation, record OG i1 Set the horizontal disc of the total station to zero, rotate the total station to aim at P i1 Point observation, record OP i The horizontal distance S2, height difference H2 and G i1 OP i The horizontal angle α1 is set, and the total station is rotated again to aim at G i2 Point observation, record OG i2 The horizontal distance S3, height difference H3 and G i1 OG i2 The horizontal angle α2; Calculate G i1 G i2 distance: ； Among them, (x Gi1, y Gi1 ) and (x Gi2, y Gi2 ) are G i1 and G i2 x, y coordinates in the global control coordinate system; Calculate G i1 P i distance: ； Calculate P i G i2 distance: ； according to , and Calculate ∠P i G i1 G i2 : ； According to ∠P i G i1 G i2 Calculate the coordinates of the laser foot point in the plane rectangular coordinate system: ； Convert the coordinates of the laser foot point in the plane rectangular coordinate system to the global control coordinate system: ； in, .

5. The method for calibrating the structural error of an airborne depth-sounding laser radar system based on quasi-conical scanning according to claim 1, characterized in that: The method of constructing an error equation based on the displacement and rotation geometric relationship between the laser scanning reference coordinate system and the global control coordinate system according to the slant distance, the drive motor angle and the coordinates of the laser foot point in the global control coordinate system includes: With the center of the reflector as the origin, the carrier flying direction is the Y-axis direction, the Z-axis is vertically upward, and the X-axis, Y-axis, and Z-axis form a right-hand system, a laser scanning reference coordinate system is established. In theory, the incident laser and the drive motor shaft are in the same plane (XZ plane) and are horizontally incident to the center of the reflector along the negative direction of the X-axis. The laser radar is rotated so that the X, Y, and Z-axis directions of the laser scanning reference coordinate system are the same as the X, Y, and Z-axis directions of the global control coordinate system; Let the slant distance of the laser foot point be S, the rotation angle of the drive motor be θ, and the coordinate calculation formula of the laser foot point in the laser reference coordinate system is: ； Among them, f x 、f y and f z are respectively the calculation formulas of the positioning model of the airborne depth-measuring laser radar taking into account the errors about the x, y and z coordinates, (μ, Δω, Δη, ΔS, Δθ) are structural error parameters, representing respectively the angle between the horizontal incident light and the X-axis, the angle error between the incident light and the drive motor shaft, the angle error between the normal line of the reflector and the drive motor shaft, the laser ranging error and the drive motor angle error; Let the coordinates of the center of the reflector in the global control coordinate system be (ΔX, ΔY, ΔZ), and the coordinates of the laser foot point in the global control coordinate system be ； Where F is the calibration model, with a total of 8 undetermined parameters (μ, Δω, Δη, ΔS, Δθ, α, β, γ), R (α, β, γ) is the rotation matrix from the laser scanning reference coordinate system to the global control coordinate system, and the calculation formula is: ； Among them, (α, β, γ) are the rotation angles around the Y, X, and Z axes respectively; The error equation is obtained by linearizing the calibration model: ； Among them, (X G , Y G , Z G ) is the coordinate of the laser foot point in the global control coordinate system measured by the total station, ((X G ), (Y G ), (Z G )) is the coordinates of the laser foot point in the global control coordinate system obtained by substituting the slant distance, the drive motor angle and the approximate values ​​of the unknown parameters into the calibration model.

6. The method according to claim 5, based on the displacement and rotation geometric relationship between the laser scanning reference coordinate system and the global control coordinate system, constructs an error equation according to the slant distance, the drive motor angle and the coordinates of the laser foot point in the global control coordinate system, characterized in that: The error-taking positioning model of the airborne bathymetric laser radar includes: Considering that the incident light is horizontally and obliquely incident on the center of the reflector, the direction vector of the incident light in the laser scanning reference coordinate system is ； Define the angle between the incident light and the drive motor shaft as ω. Considering the angle error between the incident light and the drive motor shaft, rotate the laser scanning reference coordinate system counterclockwise along the Y axis by ω + Δω so that the Z axis coincides with the drive motor shaft, and establish a laser scanning auxiliary coordinate system. The direction vector of the incident light in the laser scanning auxiliary coordinate system is ； Define the angle between the normal line of the reflector and the rotating shaft of the drive motor as η. Considering the angle error between the normal line of the reflector and the rotating shaft of the drive motor and the zeroing error of the rotating angle of the drive motor, the direction vector of the normal line of the reflector in the laser scanning auxiliary coordinate system is ； A in By rotating 180° around N in the opposite direction, the direction vector of the reflected light in the laser scanning auxiliary coordinate system can be obtained: ； A out Rotate ω + Δω clockwise along the Y axis to obtain the direction vector of the reflected light in the laser scanning reference coordinate system: ； The propagation speed of light in the air is defined as c, and the propagation time from the laser to the center of the reflector to the laser foot point obtained by waveform detection is Δt. Considering the laser ranging error, the propagation slant distance of the laser in the air is: ； In summary, the coordinates of the laser foot point in the laser scanning reference coordinate system are: 。 7. The method for calibrating the structural error of an airborne depth-sounding laser radar system based on quasi-conical scanning according to claim 1, characterized in that: The error equation is iteratively solved based on the least squares indirect adjustment principle to obtain the structural error value of the airborne bathymetric laser radar system, including: The error equation is written in matrix form: ； in, ; Assuming there are n laser foot points, then ； Among them, i represents the i-th laser foot point, and for each laser foot point, there is ； ； ； Based on the least squares indirect adjustment principle, the normal equation of the error equation is listed as follows: ； Solving the above formula we get: ； The coordinates (X) of the laser foot point measured by the total station in the global control coordinate system G , Y G , Z G ), the slant distance S, the driving motor rotation angle θ, and the approximate values ​​of the parameters to be determined (μ, Δω, Δη, ΔS, Δθ, α, β, γ) are substituted into the above formula to calculate the correction number of each parameter to be determined ( ); according to( ), update the pending parameters: ； ； ； ； ； ； ； ； The coordinates (X G ), (Y G ), (Z G )), then recalculate B and L, and then solve the error equation based on the least squares indirect adjustment principle to obtain the correction number of each of the unknown parameters ( ), and then update each of the pending parameters again, and repeat this step until the absolute values ​​of the correction numbers of all the pending parameters are less than 0.

001.

8. A calibration device for structural errors of an airborne depth-sounding laser radar system based on quasi-conical scanning, characterized in that: The device comprises: A first layout module is used to layout a plurality of global control points, local control points and laser reflective stickers in a target plane of a calibration field, and to layout two measuring stations in the calibration field; A second deployment module is used to deploy an airborne depth-measuring laser radar and a total station in the calibration field; A first acquisition module, used to acquire the coordinates of the global control point in the global control coordinate system; A second acquisition module is used to acquire the coordinates of the measuring station in the global control coordinate system; A third acquisition module is used to obtain the coordinates of the local control point and the center of the laser radar reflector in the global control coordinate system; A fourth acquisition module is used to obtain the slant distance from the center of the laser radar reflector to the laser foot point on the laser reflector and the driving motor rotation angle; A fifth acquisition module, used to acquire the coordinates of the laser foot point in the global control coordinate system; Building blocks for building error equations; The calculation module is used to solve the error equation to obtain the structural error value of the airborne depth sounding laser radar system.

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