A method and device for calibrating structural errors of an airborne bathymetric laser radar system based on quasi-conical scanning

Abstract

The application provides a kind of based on quasi-cone scanning's airborne depth laser radar system structure error's calibration method and device, comprising: establishing structure error calibration field;Global control coordinate system is established, and the coordinates of global control point, survey station, local control point and airborne depth laser radar mirror center are obtained using total station;Based on laser radar, the slant range from mirror center to laser reflection is obtained, and the laser foot point is pasted, and the laser foot point coordinates are obtained using total station;Based on the displacement and rotation geometric relationship between laser scanning reference coordinate system and global control coordinate system, error equation is constructed according to slant range, drive motor rotation angle and laser foot point coordinates;Based on the least square indirect adjustment principle, error equation is solved iteratively, and the structure error value of airborne depth laser radar system is obtained.The application can accurately obtain the structure error value of quasi-cone scanning airborne depth laser radar, and significantly improve the measurement quality and reliability of the whole depth measurement system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of airborne bathymetric laser radar systems, and particularly relates to a method and device for calibrating structural errors of an airborne bathymetric laser radar system based on a quasi-conical scan. BACKGROUND

[0002] An airborne bathymetric laser radar 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 return signals. This system integrates airborne bathymetric laser radar, global navigation satellite system (GNSS) and inertial navigation system (INS), and can quickly obtain high-precision three-dimensional water and land topographic data under complex terrain conditions. It can be widely used in topographic mapping, environmental monitoring and water conservancy engineering in shallow water areas. However, as a complex multi-sensor integrated system, the measurement accuracy of the airborne bathymetric laser radar system is easily affected by various errors, among which structural errors are one of the key factors affecting the overall measurement accuracy of the system. Structural errors mainly come from the machining and assembly deviations of internal components of the laser radar, which can cause distortion of measurement data and affect the accuracy of water depth calculation. Therefore, effective correction of structural errors is a key step to improve system accuracy, which not only significantly improves the accuracy of laser foot point three-dimensional coordinates, but also further improves the measurement quality and reliability of the entire bathymetric system.

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

[0004] In addition, some documents discuss the influence of structural errors on measurement accuracy, but mainly focus on the calibration of system installation angle errors, and lack effective structural error calibration schemes. For example, "Airborne LiDAR Data Error Processing Theory and Method" (Wang Liying, 2013, Surveying and Mapping Press), "Positioning Model and Precision Evaluation of Fixed Angle Conical Scanning Airborne Laser Depth System" (Li Kai et al., 2016, Journal of Surveying and Mapping), "Positioning Model and Simulation Analysis of Circular Scanning Airborne Laser Depth System" (Shen Erhua et al., 2016, China Laser), "Calibration Model and Simulation Analysis of Circular Scanning Airborne Laser Depth System" (Shen Erhua et al., 2016, Journal of Surveying and Mapping), "Research on Structural Error and Positioning Accuracy of Airborne Dual-frequency Laser Radar" (Lü Deliang et al., 2018, Laser and Optoelectronics Progress), "Positioning Model of Airborne Laser Radar Depth System and Influence Analysis of Collimation Axis Error" (Yu Jiayong et al., 2019, Infrared and Laser Engineering).

[0005] At present, in the patents related to structural error calibration, some only correct the measurement coordinates, without explicitly giving the specific structural error values, such as "Scanning Platform Coordinate System Error Correction Method Based on Airborne Laser Radar System" (CN116990787A, 2023). In addition, some patents involve the calibration of structural error values, but the error values provided are incomplete or not applicable to the class conical scanning airborne laser radar, such as "Calibration Method for Ranging Accuracy of Airborne Laser Radar Based on Circular Scanning" (CN111123245A, 2020) and "Test Method for Maximum Ranging Capability and Angular Accuracy of Airborne Laser Radar Based on Circular Scanning" (CN111123246A, 2020).

[0006] In summary, the existing patents and researches mostly focus on the calibration of system installation angle errors, while the existing calibration schemes fail to effectively solve the problem of calibrating structural error values in the application of class conical scanning airborne depth laser radar. SUMMARY

[0007] The present application aims to provide a calibration method and device for structural errors of airborne depth laser radar system based on class conical scanning, to solve the problem of calibrating structural error values of class conical scanning airborne depth laser radar.

[0008] To achieve the above-mentioned purpose, according to the first aspect of the present application, a calibration method for structural errors of airborne depth laser radar system based on class conical scanning is provided, which comprises:

[0009] 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 surveying points are arranged in the calibration field.

[0010] establishing a global control coordinate system, and obtaining coordinates of the global control points in the global control coordinate system by using a total station;

[0011] obtaining coordinates of the surveying station points in the global control coordinate system by using resection and trigonometric leveling based on the coordinates of the global control points in the global control coordinate system;

[0012] obtaining coordinates of the local control points and the center of the reflector of the airborne bathymetric laser radar in the global control coordinate system by using forward intersection and trigonometric leveling based on the coordinates of the surveying station points in the global control coordinate system;

[0013] obtaining the slant range from the center of the reflector to the laser reflection patch and the rotation angle of the driving motor of the laser radar based on the laser radar;

[0014] obtaining coordinates of the laser reflection patch in the global control coordinate system by using a total station based on the coordinates of the local control points in the global control coordinate system;

[0015] constructing an error equation according to the slant range, the rotation angle of the driving motor and the coordinates of the laser reflection patch 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;

[0016] iteratively solving the error equation to obtain the structural error value of the airborne bathymetric laser radar system based on the least square indirect adjustment principle.

[0017] In the method for calibrating the structural error of the airborne bathymetric laser radar system based on the quasi-conical scanning, the global control points, the local control points and the laser reflection patches are arranged in the target plane of the calibration field, and two surveying station points are arranged in the calibration field, which comprises:

[0018] The target plane of the calibration field is vertical, one global control point is arranged in the target plane, and is marked as G0, a plurality of global control points (more than one) are uniformly arranged around G0, a plurality of rectangular laser reflection patches (more than seven) are uniformly arranged around the global control points, one local control point is arranged at the lower left corner and the lower right corner of each laser reflection patch, and one surveying station point is arranged on the horizontal ground in front of the target plane of the calibration field.

[0019] In the method for calibrating the structural error of the airborne bathymetric laser radar system based on the quasi-conical scanning, the global control coordinate system is established, and the coordinates of the global control points in the global control coordinate system are obtained by using a total station, which comprises:

[0020] Taking G0 as a coordinate origin, a horizontal direction as an X axis, a vertical direction as a Y axis, and a Z axis as a right-hand system with the X and Y axes, a global control coordinate system is established;

[0021] Marking the first global control point as G1, erecting the total station in an open and unobstructed place, marking the total station center point as O after leveling, observing by rotating the total station to aim at G0 point, recording the horizontal distance S1 and the height difference H1 of OG0, setting the total station horizontal level to zero, observing by rotating the total station to aim at G1 point, recording the horizontal distance S2, the height difference H2 of OG1 and the horizontal angle a of G0OG1, and calculating the coordinates of the G1 point in the global control coordinate system:

[0022] ;

[0023] Wherein, the positive and negative signs depend on the position of G i in the global control coordinate system, for example, when G i is located in the first quadrant, both x and y coordinates take positive values, when G i is located in the second quadrant, the x coordinate takes negative value and the y coordinate takes positive value.

[0024] Similarly, the total station is rotated to aim at other global control points in turn, and the horizontal distance, the height difference and the horizontal angle of each global control point are obtained in turn, which are substituted into the above formula to calculate the coordinates of each global control point in the global control coordinate system.

[0025] In the structure error calibration method of the airborne depth measuring laser radar system based on the conical scanning, the coordinates of the laser foot point in the global control coordinate system are obtained by using the total station, and the method comprises the following steps:

[0026] Supposing that the laser foot point falls on the i-th laser reflection patch, the laser foot point is marked as P i , the left lower corner and the right lower corner of the laser reflection patch are marked as G i1 and G i2 respectively, a plane rectangular coordinate system is established with G i1 as the origin, G i1 G i2 as the X axis direction, and the vertical X axis as the Y axis direction;

[0027] Erecting the total station in an open and unobstructed place, marking the total station center point as O after leveling, observing by rotating the total station to aim at G i1 point, recording the horizontal distance S1 and the height difference H1 of OG i1 , setting the total station horizontal level to zero, observing by rotating the total station to aim at P i1 point, recording the horizontal distance S2, the height difference H2 of OP i and Gi1 OP i the horizontal angle a1, again rotate the total station to aim at G i2 point observation, record OG i2 the horizontal distance S3, the height difference H3 and G i1 OG i2 the horizontal angle a2;

[0028] calculate G i1 G i2 distance:

[0029] ;

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

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

[0038] ;

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

[0040] ;

[0041] wherein, .

[0042] In the one kind based on the structure error calibration method of airborne depth laser radar system of conical scanning, the displacement and rotation geometry between the laser scanning reference coordinate system and the global control coordinate system, according to the slant range, the driving motor rotation angle and the coordinates of the laser foot point in the global control coordinate system, error equation is constructed, including:

[0043] The laser scanning reference coordinate system is established with the mirror center as the origin, the carrier flight direction as the Y axis direction, the Z axis vertically upward, and the X axis and Y, Z axis forming a right-handed system. In theory, the incident laser and the driving motor shaft are in the same plane (XZ plane) and horizontally incident to the mirror center along the negative direction of the X axis. Rotate the laser radar to make the X, Y, Z axis direction of the laser scanning reference coordinate system the same as the X, Y, Z axis direction of the global control coordinate system.

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

[0045] ;

[0046] wherein, f x , f y and f z are the calculation formulas of the positioning model of the airborne depth laser radar considering errors about x, y and z coordinates, respectively, (μ, Δω, Δη, ΔS, Δθ) are structure error parameters, representing the angle between the horizontal incident light and the X axis, the angle error between the incident light and the driving motor shaft, the angle error between the mirror normal and the driving motor shaft, the laser ranging error and the driving motor rotation angle error;

[0047] Let the coordinates of the mirror center 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] Wherein, F is the calibration model, there are 8 undetermined parameters (μ, Δω, Δη, ΔS, Δθ, α, β, γ), R(α, β, γ) is the rotation matrix of the laser scanning reference coordinate system to the global control coordinate system, and the calculation formula is

[0050] ;

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

[0052] Linearization of the calibration model gives error equation:

[0053] ;

[0054] Where (X G , Y G , Z G ) is the coordinates 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 driving motor angle and the approximate value of each to-be-determined parameter into the calibration model.

[0055] In 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 driving motor angle and the coordinates of the laser foot point in the global control coordinate system, an error-considered positioning model of the airborne depth laser radar is constructed, including:

[0056] Considering that the incident light is horizontally inclined to 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 driving motor axis as ω, considering that there is an angle error between the incident light and the driving motor axis, rotate the laser scanning reference coordinate system along the Y axis counterclockwise by ω + Δω, so that the Z axis direction coincides with the driving motor axis, 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 mirror normal and the driving motor axis as η, considering that there is an angle error between the mirror normal and the driving motor axis and there is a zero error in the driving motor angle, the direction vector of the mirror normal in the laser scanning auxiliary coordinate system is

[0061] ;

[0062] Substitute A in Reverse and re-wind N by 180°, the direction vector of the reflected light in the laser scanning auxiliary coordinate system can be obtained:

[0063] ;

[0064] A out The direction vector of the reflected light ray in the laser scanning reference coordinate system is obtained by rotating the Y axis clockwise by ω + Δω:

[0065] ;

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

[0067] ;

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

[0069] ;

[0070] In the structure error calibration method of the airborne depth measuring laser radar system based on the conical scanning, the least squares indirect adjustment principle is used to iteratively solve the error equation to obtain the structure error value of the airborne depth measuring laser radar system, including:

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

[0072] ;

[0073] Wherein, ;

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

[0075] ;

[0076] Wherein, i represents the i-th laser foot point, and for each laser foot point,

[0077] ;

[0078] ;

[0079] ;

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

[0081] ;

[0082] Solving the above equation, we get:

[0083] ;

[0084] The coordinates (X, X) of the laser foot point measured by the total station in the global control coordinate system are... G Y G Z G The correction values ​​for each of the undetermined parameters are calculated by substituting the slant distance S, the drive motor rotation angle θ, and the approximate values ​​(μ, Δω, Δη, ΔS, Δθ, α, β, γ) into the above formula. );

[0085] according to( Update the pending parameters as described above:

[0086] ;

[0087] ;

[0088] ;

[0089] ;

[0090] ;

[0091] ;

[0092] ;

[0093] ;

[0094] Based on the updated undetermined parameters (μ, Δω, Δη, ΔS, Δθ, α, β, γ), the coordinates of the laser footpoint in the global control coordinate system are recalculated ((X... G ), (Y G ), (Z G Then, B and L are recalculated, and the corrections for each of the undetermined parameters are obtained by solving the normal equation of the error equation based on the least squares indirect adjustment principle. Then, update each of the undetermined parameters again, and repeat this step until the absolute value of the correction number of all the undetermined parameters is less than 0.001.

[0095] The present invention also provides a device for detecting and calibrating structural errors in an airborne depth sounding lidar system based on quasi-conical scanning, comprising:

[0096] The first layout module is used for laying out a plurality of global control points, local control points and laser reflection stickers in a target plane of a calibration field, and laying out two surveying points in the calibration field;

[0097] The second layout module is used for laying out an airborne depth laser radar and a total station in the calibration field;

[0098] The first acquisition module is used for acquiring coordinates of the global control points in a global control coordinate system;

[0099] The second acquisition module is used for acquiring coordinates of the surveying points in the global control coordinate system;

[0100] The third acquisition module is used for acquiring coordinates of the local control points and the center of the laser radar reflector in the global control coordinate system;

[0101] The fourth acquisition module is used for acquiring the slant range of the center of the laser radar reflector to the laser foot point on the laser reflection sticker and the rotation angle of the driving motor;

[0102] The fifth acquisition module is used for acquiring coordinates of the laser foot point in the global control coordinate system;

[0103] The construction module is used for constructing an error equation;

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

[0105] Compared with the prior art, the present application has the following beneficial effects: first, the present application proposes a calibration field construction scheme suitable for structural error calibration, including a plurality of global control points, local control points, laser reflection stickers and two surveying points. Secondly, the present application proposes an error-considered conical-scan-like airborne depth laser radar positioning model, which comprehensively considers five types of key structural errors, i.e., incident light deflection angle error, incident light and driving motor shaft angle error, reflector normal and driving motor shaft angle error, laser ranging error and driving motor rotation angle error, and deduces an accurate calibration model based on this, and further constructs an error equation. Finally, the error equation is iteratively solved by using least squares indirect adjustment, so as 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, and the measurement quality and reliability of the entire depth measurement system can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0106] Figure 1 The present application is a method technical flow chart;

[0107] Figure 2 The present application is a calibration field schematic diagram;

[0108] Figure 3 Figure 1 is a schematic diagram of a global control coordinate system;

[0109] Figure 4 Figure 2 is a coordinate distribution diagram of a local control point;

[0110] Figure 5 Figure 3 is a schematic diagram of a plane rectangular coordinate system;

[0111] Figure 6 Figure 4 is a process diagram of iterative solution of an error equation;

[0112] Figure 7 Figure 5 is a coordinate distribution diagram of laser foot points before and after correction of a structural error;

[0113] Figure 8 Figure 6 is a coordinate error diagram before and after correction of a structural error;

[0114] Figure 9 Figure 7 is a schematic diagram of an apparatus of the present application. DETAILED DESCRIPTION

[0115] To make the objectives, technical solutions and advantages of the present application clearer, further detailed description will be made to the present application with reference to the embodiments and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0116] The measurement error of the airborne depth laser radar system mainly includes system integration error and single machine error. The system integration error mainly includes the installation angle error of the airborne depth laser radar and INS, and the eccentric distance error of the laser radar and GNSS. The single machine error mainly refers to the error of the laser radar, INS and GNSS themselves, wherein the structural error of the laser radar due to the processing and assembly deviation of internal components is the main source of the single machine error. The system integration error can be corrected by flight calibration, while the structural error cannot be eliminated by flight dynamic calibration and must be calibrated on the ground before flight. Calibrating the structural error not only can evaluate the equipment quality, but also can correct the system error in subsequent data processing, significantly improve the precision of the three-dimensional coordinates of the laser foot points, and further improve the measurement quality and reliability of the entire depth measurement system.

[0117] Embodiment 1:

[0118] In combination with Figure 1 It is explained that the present application provides a technical process of calibrating the structural error of an airborne depth laser radar system based on a quasi-cone scanning, which comprises the following steps:

[0119] S1: multiple global control points, local control points and laser reflection stickers are arranged in the target plane of the calibration field, and two surveying station points are arranged in the calibration field;

[0120] S2: a global control coordinate system is established, and the coordinates of the global control points in the global control coordinate system are obtained by using the total station;

[0121] S3: based on the coordinates of the global control points in the global control coordinate system, the coordinates of the surveying station points in the global control coordinate system are obtained by using the resection method and the trigonometric leveling method;

[0122] S4: based on the coordinates of the surveying station points in the global control coordinate system, the coordinates of the local control points 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 leveling method;

[0123] S5: based on the laser radar, the slant range from the reflector center to the laser foot point on the laser reflection sticker and the driving motor rotation angle are obtained;

[0124] S6: based on the coordinates of the local control points in the global control coordinate system, the coordinates of the laser foot point in the global control coordinate system are obtained by 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 range, the driving motor rotation angle and the coordinates of the laser foot point in the global control coordinate system;

[0126] S8: based on the least square indirect adjustment principle, the error equation is iteratively solved to obtain the structural error value of the airborne depth laser radar system.

[0127] S1 specifically includes:

[0128] In combination Figure 2The calibration field is illustrated, and a vertical target plane is arranged in the calibration field. A global control point is selected at a point in the target plane, marked as G0, and a plurality of global control points (more than 1) are uniformly arranged around the point. A total station reflector plate is pasted on each global control point. A plurality of rectangular laser reflectors (more than 7) are uniformly arranged around the global control point, and a local control point is arranged at the lower left corner and the lower right corner of each laser reflector. A total station reflector plate is pasted on each local control point. A measuring station is arranged on the horizontal ground in front of the target plane of the calibration field, and a total station is arranged at the measuring station. The number of global control points should be more than 2 to ensure the accuracy of the resection. There are 8 undetermined parameters in the error equation, and more than 7 equations are needed to be listed, so the number of laser reflectors should be more than 7 to obtain more than 7 laser foot point data. Since the scanning mode of the laser radar is a conical scanning mode, the scanning track is an ellipse, and therefore the layout of the laser reflectors should be close to an ellipse, so that the laser scanning track falls uniformly on the laser reflectors.

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

[0130] S2 specifically comprises:

[0131] Taking G0 as the coordinate origin, the horizontal direction as the X axis, and the vertical direction as the Y axis, a global control coordinate system is established. The first global control point is marked as G1. The total station is erected in an open and unobstructed place, and the center point of the total station is marked as O after leveling. The total station is turned to sight G0, and the horizontal distance S1 and the height difference H1 of OG0 are recorded. The horizontal level of the total station is set to zero, the total station is turned to sight G1, and the horizontal distance S2, the height difference H2 and the horizontal angle a of G0OG1 are recorded. The coordinates of G1 in the global control coordinate system are calculated as follows:

[0132] ;

[0133] Wherein, the signs depend on the positions of G i in the global control coordinate system. For example, when G i is located in the first quadrant, both x and y coordinates take positive values, when G i is located in the second quadrant, the x coordinate takes a negative value and the y coordinate takes a positive value.

[0134] Similarly, the total station is turned to sight other global control points in turn, and the horizontal distance, the height difference and the horizontal angle of each global control point are obtained in turn. The coordinates of each global control point in the global control coordinate system are calculated by substituting the values into the above formula.

[0135] For example, in combination with Figure 3The global control coordinate system established in this embodiment is illustrated, wherein the X axis is horizontal leftward, the Y axis is vertical downward, and the Z axis is perpendicular to the target plane forwardly, and the coordinates of the global control points are shown in Table 1.

[0136] Table 1 (unit: m)

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

[0138] S3 specifically includes:

[0139] First, the total station is erected at the position of the station point Z1, and after centering and leveling, the plane coordinates (x, z coordinates) of the station point Z1 in the global control coordinate system are obtained by using the resection method based on the x and z coordinates of the global control points in the global control coordinate system. Then, the y coordinate of the station point Z1 in the global control coordinate system is obtained by using the trigonometric leveling method based on the y coordinate of the global control point G0. Similarly, the coordinates of the station point Z2 in the global control coordinate system are obtained.

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

[0141] Table 2 (unit: m)

[0142] Serial number x y z ​ -2.296 1.916 5.271 ​ 2.737 1.892 5.317

[0143] S4 specifically includes:

[0144] First, the x and z coordinates of the local control points and the center of the airborne bathymetric laser radar reflector in the global control coordinate system are sequentially obtained by using the forward intersection method based on the x and z coordinates of the station points Z1 and Z2 in the global control coordinate system. Then, the y coordinates of the local control points and the center of the laser radar reflector in the global control coordinate system are sequentially obtained by using the trigonometric leveling method based on the y coordinate of the station point Z2.

[0145] For example, in combination with Figure 4 The coordinate distribution of the local control points in this embodiment is illustrated, and there are 28 local control points, which are distributed in an elliptical shape as a whole.

[0146] S5 specifically includes:

[0147] The transmitting and receiving device and the rotating mirror scanning device of the laser radar are turned off, the reflector is manually rotated, the transmitting and receiving device is turned on when the laser foot point falls on the laser reflection sticker, the waveform data is collected and waveform detection is performed to obtain the laser propagation slant range, at the same time, the driving motor rotation angle is recorded and the position of the laser foot point is marked. Continue to rotate the reflector, so that the laser foot point falls on each laser reflection sticker in turn, and the slant range and driving motor rotation angle of each laser foot point are obtained in turn and marked.

[0148] S6 specifically includes:

[0149] Let P be the laser foot point that falls on the i-th laser reflector. i The local control points at the lower left and lower right corners of the laser reflective patch are marked as G. i1 and G i2 Combining Figure 5 Describe the Cartesian coordinate system, with G as the base. i1 With the origin as the origin, G i1 G i2 Establish a Cartesian coordinate system with the X-axis as the direction and the Y-axis as the direction perpendicular to the X-axis upwards.

[0150] Set up the total station in an open, unobstructed area. After leveling the ground, mark the center point of the total station as O. Rotate the total station to aim at G. i1 Point observation, recording OG i1 Given the horizontal distance S1 and elevation difference H1, set the total station's horizontal circle to zero, and rotate the total station to aim at P. i1 Point observation, recording OP i Horizontal distance S2, elevation difference H2 and G i1 OP i Horizontal angle α1, rotate the total station again to aim at G. i2 Point observation, recording OG i2 Horizontal distance S3, elevation 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 respectively G i1 and G i2 The x and 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 The coordinates of the laser foot point in the plane rectangular coordinate system are calculated:

[0161] .

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

[0163] ;

[0164] Wherein, .

[0165] S7 specifically comprises:

[0166] The laser scanning reference coordinate system is established with the mirror center as the origin, the carrier flight direction as the Y-axis direction, the Z-axis vertically upward, and the X-axis and Y-axis and Z-axis forming a right-handed system. In theory, the incident laser and the driving motor shaft are in the same plane (XZ plane) and horizontally incident to the mirror center along the negative direction of the X-axis. The laser radar is rotated to make the X, Y, and Z axes of the laser scanning reference coordinate system the same as the X, Y, and Z axes of the global control coordinate system.

[0167] Let the slant distance of the laser foot point be S, the driving motor rotation angle be θ, and (μ, Δω, Δη, ΔS, Δθ) be the structural error parameters, respectively representing the angle between the horizontal incident light and the X-axis, the angle error between the incident light and the driving motor shaft, the angle error between the mirror normal and the driving motor shaft, the laser ranging error, and the driving motor rotation error. Considering that the incident light is horizontally inclined to the mirror center, 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 driving motor shaft as ω. Considering that there is an angle error between the incident light and the driving motor shaft, the laser scanning reference coordinate system is counterclockwise rotated along the Y-axis by ω + Δω, so that the Z-axis direction coincides with the driving motor shaft. The laser scanning auxiliary coordinate system is established, and the direction vector of the incident light in the laser scanning auxiliary coordinate system is

[0170] .

[0171] Define the angle between the mirror normal and the rotation axis of the driving motor as η. Considering the angle error between the mirror normal and the rotation axis of the driving motor and the zero error of the driving motor rotation angle, the direction vector of the mirror normal in the laser scanning auxiliary coordinate system is

[0172] .

[0173] A in After reversing and rewinding N by 180°, the direction vector of the reflected light in the laser scanning auxiliary coordinate system is obtained:

[0174] .

[0175] A out After rotating clockwise along the Y axis by ω + Δω, the direction vector of the reflected light in the laser scanning reference coordinate system is obtained:

[0176] .

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

[0178] .

[0179] Based on the above, the coordinates of the laser foot point in the laser scanning reference coordinate system are:

[0180] .

[0181] where f x , f y and f z are the calculation formulas of the positioning model of the airborne depth sounding laser radar considering errors about x, y and z coordinates, respectively.

[0182] Let the coordinates of the mirror center 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, and there are 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

[0185] ;

[0186] where (a, b, g) are the rotation angles around Y, X, Z axes respectively.

[0187] The error equation is obtained by linearizing the calibration model:

[0188] ;

[0189] where (X G , Y G , Z G ) are the coordinates of the laser foot point in the global control coordinate system measured by the total station, ((X G ), (Y G ), (Z G )) are the coordinates of the laser foot point in the global control coordinate system obtained by substituting the slant distance, the driving motor angle and the approximate values of the undetermined parameters into the calibration model.

[0190] S8 specifically comprises:

[0191] The error equation is written in matrix form:

[0192] ;

[0193] where, .

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

[0195] ;

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

[0197] ;

[0198] ;

[0199] .

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

[0201] .

[0202] Solving the above equation gives:

[0203] .

[0204] Substitute the coordinates (X G , Y G , Z GSubstituting the slant distance S, the drive motor rotation angle θ, and the approximate values ​​of each undetermined parameter (μ, Δω, Δη, ΔS, Δθ, α, β, γ) into the above formula, we can calculate the correction value for each undetermined parameter. ).

[0205] according to( Update all pending parameters:

[0206] ;

[0207] ;

[0208] ;

[0209] ;

[0210] ;

[0211] ;

[0212] ;

[0213] .

[0214] Based on the updated undetermined parameters (μ, Δω, Δη, ΔS, Δθ, α, β, γ), recalculate the coordinates of the laser footpoint in the global control coordinate system ((X... G ), (Y G ), (Z G Then, B and L are recalculated, and the corrections for each undetermined parameter are obtained by solving the normal equation of the error equation based on the least squares indirect adjustment principle. Then update each undetermined parameter again, repeating this step until the absolute value of the correction of all undetermined parameters is less than 0.001.

[0215] For example, combining Figure 6 The iterative solution process of the error equation is explained. After 17 iterations, the absolute values ​​of the corrections for 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, compared with the original calibration, the coordinates of the laser foot points obtained by the lidar measurement after calibration are closer to the coordinates obtained by the total station measurement (the actual laser foot point coordinates). 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, with an error reduction of 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] In combination Figure 9 The present application provides a kind of based on the structure error calibration device of airborne depth laser radar system of conical scanning, comprising:

[0220] M1: first layout module, for being laid out multiple global control points, local control points and laser reflection stickers in calibration field target plane, two surveying points are laid out in calibration field;

[0221] M2: second layout module, for being laid out airborne depth laser radar and total station in calibration field;

[0222] M3: first acquisition module, for acquiring the coordinates of global control point in global control coordinate system;

[0223] M4: second acquisition module, for acquiring the coordinates of surveying point in global control coordinate system;

[0224] M5: third acquisition module, for acquiring the coordinates of local control point and laser radar mirror center in global control coordinate system;

[0225] M6: fourth acquisition module, for acquiring the slant range of laser radar mirror center to laser reflection sticker and the rotation angle of driving motor;

[0226] M7: fifth acquisition module, for acquiring the coordinates of laser foot point in global control coordinate system;

[0227] M8: construction module, for constructing error equation;

[0228] M9: calculation module, for solving error equation, and the structural error value of airborne depth laser radar system is obtained.

[0229] The above-described specific embodiments, the purpose, technical scheme and beneficial effects of the present application are further described in detail, it should be understood that, above-mentioned only for the specific embodiments of the present application, and not for limiting the present application, any skilled in the art in the technical range disclosed in the present application, any modification, equivalent replacement, improvement, etc. that can be easily thought of, should be included in the protection scope of the present application.

Claims

1. A method for calibrating the structure error of an airborne bathymetric laser radar system based on quasi-conical scanning, characterized in that, The method comprises: a plurality of global control points, local control points and laser reflection stickers are arranged in a target plane of a calibration field, two surveying station points are arranged in the calibration field; a global control coordinate system is established, and coordinates of the global control points in the global control coordinate system are obtained by using a total station; coordinates of the surveying station points in the global control coordinate system are obtained by using resection and trigonometric leveling based on the coordinates of the global control points in the global control coordinate system; coordinates of the local control points and a center of a reflector of an airborne bathymetric laser radar in the global control coordinate system are obtained by using intersection and trigonometric leveling based on the coordinates of the surveying station points in the global control coordinate system; a slant range from the center of the reflector to a laser foot point on the laser reflection sticker and a driving motor rotation angle are obtained based on the laser radar; coordinates of the laser foot point in the global control coordinate system are obtained by using the total station based on the coordinates of the local control points in the global control coordinate system; an error equation is constructed according to the slant range, the driving motor rotation angle and the coordinates of the laser foot point in the global control coordinate system based on a displacement and a rotation geometric relationship between a laser scanning reference coordinate system and the global control coordinate system, comprising: a laser scanning reference coordinate system is established with the center of the reflector as an origin, a carrier flight direction as a Y-axis direction, a Z-axis vertically upward, and an X-axis forming a right-hand system with the Y-axis and the Z-axis, in theory, incident laser light and a driving motor rotation shaft are horizontally incident to the center of the reflector in an XZ plane and along a negative direction of the X-axis, and the laser radar is rotated so that directions of X, Y and Z axes of the laser scanning reference coordinate system are the same as directions of X, Y and Z axes of the global control coordinate system; the slant range of the laser foot point is S, the driving motor rotation angle is θ, and a coordinate calculation formula of the laser foot point in the laser reference coordinate system is ； wherein f x , f y and f z are the calculation formulas of the positioning model of the airborne laser depth sounder with error consideration with respect to x, y and z coordinates, respectively, (μ, Δω, Δη, ΔS, Δθ) are the structural error parameters, representing the angle between the horizontal incident light and the X axis, the error between the incident light and the driving motor shaft, the error between the mirror normal and the driving motor shaft, the laser ranging error and the driving motor angle error, respectively; coordinates of the center of the reflector in the global control coordinate system are (ΔX, ΔY, ΔZ), and coordinates of the laser foot point in the global control coordinate system are ； wherein F is a calibration model, there are eight undetermined parameters (μ, Δω, Δη, ΔS, Δθ, α, β, γ), R(α, β, γ) is a rotation matrix of the laser scanning reference coordinate system to the global control coordinate system, and a calculation formula is ； wherein (α, β, γ) are rotation angles around Y, X and Z axes, respectively; an error equation is obtained by linearizing the calibration model: ； wherein (X G , Y G , Z G ) are coordinates of the laser foot point in the global control coordinate system obtained by total station measurement, and ((X G ), (Y G ), (Z G )) are coordinates of the laser foot point in the global control coordinate system obtained by substituting the slant distance, the driving motor rotation angle, and the approximate values of various to-be-determined parameters into the calibration model for solving. indirect least squares adjustment principle is used to iteratively solve the error equation, and a structural error value of the airborne bathymetric laser radar system is obtained.

2. The method according to claim 1, wherein the method is characterized by, the plurality of global control points, local control points and laser reflection stickers are arranged in a target plane of a calibration field, and the two surveying station points are arranged in the calibration field, comprising: The calibration field target plane is vertical, a point in the target plane is selected to arrange the global control point, marked as G0, and a plurality of global control points are uniformly arranged around it, a plurality of laser reflection stickers are uniformly arranged around the global control points, one local control point is arranged at the lower left corner and the lower right corner of each laser reflection sticker, and one surveying station point is arranged on the horizontal ground in front of the calibration field target plane.

3. The method according to claim 1, wherein the method is characterized by, The global control coordinate system is established, and the coordinates of the global control points in the global control coordinate system are obtained by using the total station, including: Taking 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, the global control coordinate system is established; The first global control point is marked as G1, the total station is erected in an open and unobstructed place, the center point of the total station is marked as O after leveling, the total station is rotated to aim at G0 point observation, the horizontal distance S1 and the height difference H1 of OG0 are recorded, the horizontal level of the total station is set to zero, the total station is rotated to aim at G1 point observation, the horizontal distance S2, the height difference H2 and the horizontal angle a of G0OG1 are recorded, and the coordinates of G1 point in the global control coordinate system are calculated: ； where the sign depends on G i the position in the global control coordinate system, when G i is in the first quadrant, both take positive values, when G i is in the second quadrant, the x coordinate takes negative value and the y coordinate takes positive value; Similarly, the total station is rotated to aim at other global control points in turn, and the horizontal distance, the height difference and the horizontal angle of each global control point are obtained in turn, which are substituted into the above formula to calculate the coordinates of each global control point in the global control coordinate system.

4. The method of calibrating the structure error of an airborne bathymetric laser radar system based on a conical scanning-like scan according to claim 1, wherein, 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 by using the total station, including: If the laser foot point falls on the i-th laser reflective patch, mark the laser foot point as P i , mark the local control points of the lower left corner and the lower right corner of the laser reflective patch as G i1 and G i2 respectively, establish a plane rectangular coordinate system with G i1 as the origin, G i1 G i2 as the X-axis direction, and the vertical X-axis upward as the Y-axis direction; Set up the total station in an open place without shelter, mark the center point of the total station as O after leveling, and rotate the total station to aim at G i1 Point observation, record OG i1 The horizontal distance S1 and the height difference H1, set the horizontal level of the total station to zero, and rotate the total station to aim at P i1 Point observation, record OP i The horizontal distance S2, the height difference H2 and G i1 OP i The horizontal angle α1, rotate the total station to aim at G again i2 Point observation, record OG i2 The horizontal distance S3, the height difference H3 and G i1 OG i2 The horizontal angle α2; Compute G i1 G i2 Distance: ； wherein (x Gi1, y Gi1 ) and (x Gi2, y Gi2 ) are the x, y coordinates in the global control coordinate system; and i1 G i2 is the global control coordinate system. Compute G i1 P i Distance: ； Compute 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: ； The coordinates of the laser foot points in the plane rectangular coordinate system are converted to the global control coordinate system: ； wherein .

5. The laser scanning based on the displacement and rotation geometry relationship between the reference coordinate system and the global control coordinate system according to claim 1, the error equation is constructed according to the slant distance, the driving motor rotation angle and the coordinates of the laser foot point in the global control coordinate system, characterized in that, The positioning model of the airborne depth laser radar considering errors includes: Considering that the incident light is horizontally inclined to 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 driving motor shaft as ω, considering that there is an angle error between the incident light and the driving motor shaft, rotate the laser scanning reference coordinate system along the Y axis counterclockwise by ω + Δω, so that the Z axis direction coincides with the driving 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 reflector normal and the driving motor shaft as η, considering that there is an angle error between the reflector normal and the driving motor shaft and a zero error of the driving motor angle, the direction vector of the reflector normal in the laser scanning auxiliary coordinate system is ； A in After reversing the winding N by 180°, the direction vector of the reflected light in the laser scanning auxiliary coordinate system can be obtained. ； A out A clockwise rotation of ω + Δω along the Y-axis gives the direction vector of the reflected light ray in the laser scanning reference frame: ； Define the propagation speed of light in air as c, the propagation time of the laser from the center of the reflector to the laser foot point as Δt, and considering the laser ranging error, the propagation slant distance of laser in air is: ； Based on the above, the coordinates of the laser foot point in the laser scanning reference coordinate system are: 。 6. The method of calibrating the structure error of an airborne bathymetric laser radar system based on a conicoid-like scanning according to claim 1, wherein, Based on the least squares indirect adjustment principle, the error equation is iteratively solved to obtain the structural error value of the airborne depth laser radar system, including: The error equation is written in matrix form as follows: ； wherein ; Suppose that there are n laser foot points in total, then ； where i represents the i-th laser foot point, and for each laser foot point ； ； ； Based on the least square indirect adjustment principle, the normal equation of the error equation is listed as follows: ； Solving the above equation gives ； The coordinates (X, X) of the laser foot point measured by the total station in the global control coordinate system are... G , Y G Z G The correction values ​​for each of the undetermined parameters are calculated by substituting the slant distance S, the drive motor rotation angle θ, and the approximate values ​​(μ, Δω, Δη, ΔS, Δθ, α, β, γ) into the above formula. ); according to( Update the pending parameters as described above: ； ； ； ； ； ； ； ； Based on the updated undetermined parameters (μ, Δω, Δη, ΔS, Δθ, α, β, γ), the coordinates of the laser footpoint in the global control coordinate system are recalculated ((X... G ), (Y G ), (Z G Then, B and L are recalculated, and the corrections for each of the undetermined parameters are obtained by solving the normal equation of the error equation based on the least squares indirect adjustment principle. Then, update each of the undetermined parameters again, and repeat this step until the absolute value of the correction number of all the undetermined parameters is less than 0.

001.

7. A device for calibrating the structure error of an airborne bathymetric laser radar system based on quasi-conical scanning, for implementing the calibration method according to any one of claims 1 to 6, characterized in that, The device comprises: A first layout module for laying out a plurality of global control points, local control points and laser reflection stickers in a target plane of a calibration field, and laying out two surveying points in the calibration field; A second layout module for laying out an airborne depth measuring laser radar and a total station in the calibration field; A first acquisition module for acquiring coordinates of the global control points in a global control coordinate system; A second acquisition module for acquiring coordinates of the surveying points in the global control coordinate system; A third acquisition module for acquiring coordinates of the local control points and the center of the laser radar reflector in the global control coordinate system; A fourth acquisition module for acquiring the slant range from the center of the laser radar reflector to the laser foot point on the laser reflection sticker and the rotation angle of the driving motor; A fifth acquisition module for acquiring coordinates of the laser foot point in the global control coordinate system; A construction module for constructing an error equation; A calculation module for solving the error equation to obtain a structural error value of the airborne depth measuring laser radar system.

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