Error correction method for collimation axis of airborne laser radar of oval scanning track

Abstract

The invention discloses an airborne laser radar collimation axis error correction method based on an oval scanning track, belongs to the technical field of error correction, is used for collimation axis error correction, and comprises the following steps: correcting points of the oval scanning track and correcting a normal vector of a reflector; performing forward fixed-point scanning on an object to be measured by using the laser radar to obtain a forward oval scanning track, performing backward fixed-point scanning to obtain a backward oval scanning track, and obtaining points of the corrected oval scanning track; and calculating a scaling factor, and correcting the normal vector of the reflector to complete collimation axis error correction. The method does not need external auxiliary equipment, does not depend on ground control points or regular ground feature information, is suitable for complex application scenes without deployment and control, without overlapping areas and the like, and improves the adaptability, correction precision and engineering practicability of the system; the practicability in a field complex environment is remarkably improved, and the method is suitable for single-route flight in an uncontrolled area; the method has a trajectory scale distortion correction capability, and enhances the spatial consistency of sounding point clouds.

Description

Technical Field

[0001] The invention discloses a method for correcting the sight axis error of an airborne laser radar with an oval scanning trajectory, and belongs to the technical field of error correction. Background Art

[0002] Airborne LiDAR bathymetric systems often use an off-axis circular mirror structure to form an oval scanning trajectory, and their measurement accuracy is highly dependent on the accuracy of the system's geometric parameters. As one of the core error sources, the line of sight error significantly affects the spatial positioning accuracy of the laser footpoint, thereby reducing the effectiveness and stability of the entire bathymetric system. The line of sight error generally refers to the actual deviation from the ideal angle between the laser emission optical axis and the scanning system's rotation axis, reflecting the inaccuracy in the system's alignment and adjustment process. In the laser scanning coordinate system, the line of sight error of the airborne LiDAR bathymetric system is the error between the angle between the normal of the reflector and the motor shaft, and the error between the angle between the incident light and the motor shaft. In a system using an off-axis elliptical scanning structure, this error will directly cause the scanning trajectory to be skewed, rotated, or deformed overall in space, resulting in systematic offsets of the point cloud data in both the vertical elevation and horizontal position directions. The existence of the error between the normal line and the angle of the reflector will affect the shape of the oval scanning trajectory. That is, when this angle is greater than the design value, the oval scanning trajectory becomes larger; conversely, when this angle is less than the design value, the oval scanning trajectory becomes smaller and affects the coordinates of the laser foot point; the existence of the error between the incident light and the angle between the motor shaft will make the lidar scanning plane not parallel to the actual scanning plane, causing the scanning plane to be distorted in space.

[0003] Since this type of error has the characteristics of strong directionality, uneven scale, and complex propagation path, if it is not corrected, it will cause an overall error band in the laser depth measurement results. Especially in an environment with high flight altitude or strong fluctuations in sea conditions, the error amplification effect is more obvious, seriously affecting the accuracy of seabed topography measurement.

[0004] There are three main methods for correcting the line-of-sight error of airborne lidar systems in the existing technology. One is a point cloud registration method based on the overlapping areas of flight strips. The iterative closest point (ICP) algorithm is used to perform point cloud registration on the overlapping areas of adjacent flight strips. The line-of-sight error is solved by minimizing the spatial deviation by registering the point clouds of the overlapping areas of different routes. However, this method relies on the overlap of flight strips and is difficult to apply to single routes or uncontrolled scenarios. The second is a calibration method based on feature surface matching. It uses planar features such as building facades to construct a point-to-surface residual function to minimize the line-of-sight error. This method is suitable for urban scenarios, but fails in areas without typical landforms such as oceans or wilderness. The third is an error modeling method based on the scanning trajectory structure. It infers the platform coordinate system error by analyzing the trajectory distortion. It has a certain universality, but does not achieve decoupling modeling of the line-of-sight error source. Compared with the above three methods, the Chinese invention patent application with publication number CN119291658A proposes to subdivide the sighting axis error into two parts: the error of the angle between the normal line of the reflector and the rotation axis, and the error of the angle between the incident light and the rotation axis. By measuring the A, B, C, and D foot points, a least squares error model of the six side lengths is constructed to independently solve the two types of errors. It has higher geometric accuracy and theoretical closure, but relies on auxiliary equipment such as total stations and is not suitable for unmanned deployment in the field. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for correcting the sighting axis error of an airborne laser radar with an oval scanning trajectory, so as to solve the problem in the prior art that the sighting axis error is difficult to correct.

[0006] A method for correcting the sight axis error of an airborne laser radar with an oval scanning trajectory, comprising correcting points of the oval scanning trajectory and correcting a normal vector of a reflector; A laser radar is used to perform a forward fixed-point scan of the object to be measured to obtain a forward oval scanning trajectory, and a backward fixed-point scan is performed to obtain a backward oval scanning trajectory. The laser radar outputs the measured rotation angle of the rotating mirror, extracts the single-circle oval scanning trajectory, determines the directions of the major and minor axes, calculates the angle of rotation of the uncorrected scanning coordinate system to the actual coordinate system around the Y axis, calculates the angle of rotation of the uncorrected scanning coordinate system to the actual coordinate system around the X axis, and calculates the angle of rotation of the uncorrected scanning coordinate system to the actual coordinate system around the Z axis, and obtains the points of the corrected oval scanning trajectory; Calculate the scaling factor, correct the normal vector of the reflector, and complete the collimation axis error correction.

[0007] Determining the major and minor axis directions involves projecting the oval scanning trajectory onto a two-dimensional plane and extracting the oval scanning trajectory as a two-dimensional point set: ; Where, It is The two-dimensional point set of the oval scanning trajectory has a total of A two-dimensional point, and Indicates the Two-dimensional point coordinates; Compute the 2D mean vector of a 2D set of points : ; Calculate the coordinates of the center point of a two-dimensional point set : ; Construct a two-dimensional covariance matrix of a two-dimensional point set : ; Where, 、 、 、 are the four elements of the covariance matrix.

[0008] Determining the major and minor axis directions includes Perform eigenvalue decomposition and get The two eigenvalues ​​of The eigenvector corresponding to the largest eigenvalue is in the direction of the long axis of the oval scanning trajectory, and the eigenvector corresponding to the second largest eigenvalue is in the direction of the short axis of the oval scanning trajectory.

[0009] Search for the two endpoints farthest from the center point in the oval scanning trajectory along the long axis and short axis directions respectively, as the long axis and short axis vertex coordinates of the single circle oval scanning trajectory. The long axis vertex coordinate of the forward oval scanning trajectory is marked as 、 , the coordinates of the short axis vertex of the forward oval scanning trajectory are 、 , the coordinate of the long axis vertex of the backward oval scanning trajectory is marked as 、 , the coordinates of the minor axis vertex of the backward oval scanning trajectory are 、 .

[0010] Calculating the rotation angle of the uncorrected scanning coordinate system to the actual coordinate system around the Y axis includes extracting multiple single-circle oval scanning trajectories, projecting the single-circle oval scanning trajectories onto the XOZ plane and ignoring the influence of the Y axis. The forward short axis vertex coordinate is and , the coordinates of the vertex of the backward short axis are and ; Construct the minor axis vector: ; ; Where, is the forward scan vector, is the backward scanning vector, and the projection of the two scanning vectors on the XOZ plane is: ; ; Where, yes Projection on the XOZ plane, yes Projection on the XOZ plane, 、 are the directional components of the forward projection in the X-axis and Z-axis directions, 、 are the directional components of the back projection in the X-axis and Z-axis directions; Calculate the rotation angle around the Y axis of the uncorrected scan coordinate system to the actual coordinate system : .

[0011] Calculating the rotation angle of the uncorrected scanning coordinate system to the actual coordinate system around the X-axis includes extracting multiple single-circle oval scanning trajectories, projecting the single-circle oval scanning trajectories onto the YOZ plane and ignoring the influence of the X-axis. The forward long axis vertex coordinate is and , the coordinates of the vertex of the posterior major axis are and ; Construct the major axis vector: ; ; The projection of the two scan vectors on the YOZ plane is: ; ; Where, yes Projection on the YOZ plane, yes Projection on the YOZ plane, is the directional component of the forward projection in the Y-axis direction, is the directional component of the back projection in the Y-axis direction; Calculate the rotation angle around the X axis of the uncorrected scan coordinate system to the actual coordinate system : .

[0012] Calculating the rotation angle of the uncorrected scanning coordinate system to the actual coordinate system around the Z axis includes extracting multiple single-circle oval scanning trajectories, projecting the single-circle oval scanning trajectories onto the XOY plane and ignoring the influence of the Z axis. The forward long axis vertex coordinate is and , the coordinates of the vertex of the posterior major axis are and ; Construct the major axis vector: ; ; The projection of the two scan vectors on the XOY plane is: ; ; Where, yes Projection on the XOY plane, yes Projection on the XOY plane; Calculate the rotation angle around the X axis of the uncorrected scan coordinate system to the actual coordinate system : .

[0013] The points of the new oval scanning trajectory include the three-dimensional rotation matrix for: ; ; ; ; Where, 、 、 They are 、 、 The average value of 、 、 are three known matrices; Will Applied to the forward oval scanning trajectory and the backward oval scanning trajectory, for each point of the oval scanning trajectory Perform posture compensation to obtain the corrected oval scanning trajectory points : .

[0014] Calculating the scaling factor involves designing the major axis vertex to be , the uncorrected major axis vertex is , the horizontal coordinate values ​​of the two major axis vertices are: ; ; ; Where, The major axis vertex is No. The uncorrected actual major axis vertex value of the circle, The major axis vertex is No. The design long axis vertex value of the circle, yes The maximum value of is the mirror rotation angle, is the scaling factor.

[0015] Correcting the normal vector of the reflector includes the correction angle of the normal vector of the reflector for: ; Where, is the angle between the normal line of the reflector and the motor shaft; Corrected mirror normal vector for: .

[0016] Compared with the existing technology, the present invention has the following beneficial effects: the present invention does not require external auxiliary equipment, does not rely on ground control points or regular ground feature information, is suitable for complex application scenarios such as uncontrolled and non-overlapping areas, and improves the system's adaptability, correction accuracy and engineering practicality; significantly improves the practicality in complex outdoor environments and is suitable for uncontrolled areas and single-route flights; adopts three-axis joint correction to improve accuracy and consistency, and realizes joint high-precision correction of X, Y, and Z axis errors without sacrificing efficiency; has the ability to correct trajectory scale distortion, and enhances the spatial consistency of the sounding point cloud. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a simplified diagram of the LiDAR scanning system; Figure 2 It is the projection of the minor axis on the XOZ plane; Figure 3 It is the projection of the long axis on the YOZ plane; Figure 4 It is the projection of the long axis on the XOY plane; Figure 5 It is the forward oval scanning trajectory diagram; Figure 6A comparison diagram of the forward oval scanning trajectory and the oval scanning trajectory of a single circle; Figure 7 The projection in the XOZ plane and the comparison of the major and minor axes in the front and back directions; Figure 8 This is the calculation result diagram of the XOZ plane; Figure 9 The projection in the YOZ plane and the comparison of the major and minor axes in the forward and backward directions; Figure 10 This is the calculation result diagram of the YOZ plane; Figure 11 It is the projection in the XOY plane and the comparison diagram of the long and short axes in the front and back directions; Figure 12 This is the calculation result diagram of the XOY plane; Figure 13 This is a comparison diagram of the corrected forward oval scanning trajectory and the oval scanning trajectory; Figure 14 This is a comparison chart between the scanned value and the designed value; Figure 15 This is the calculation result diagram of the scaling factor and the correction angle; Figure 16 The oval scanning trajectory result diagram after introducing the scaling factor correction. DETAILED DESCRIPTION

[0018] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0019] A method for correcting the sight axis error of an airborne laser radar with an oval scanning trajectory, comprising correcting points of the oval scanning trajectory and correcting a normal vector of a reflector; A laser radar is used to perform a forward fixed-point scan of the object to be measured to obtain a forward oval scanning trajectory, and a backward fixed-point scan is performed to obtain a backward oval scanning trajectory. The laser radar outputs the measured rotation angle of the rotating mirror, extracts the single-circle oval scanning trajectory, determines the directions of the major and minor axes, calculates the angle of rotation of the uncorrected scanning coordinate system to the actual coordinate system around the Y axis, calculates the angle of rotation of the uncorrected scanning coordinate system to the actual coordinate system around the X axis, and calculates the angle of rotation of the uncorrected scanning coordinate system to the actual coordinate system around the Z axis, and obtains the points of the corrected oval scanning trajectory; Calculate the scaling factor, correct the normal vector of the reflector, and complete the collimation axis error correction.

[0020] Determining the major and minor axis directions involves projecting the oval scanning trajectory onto a two-dimensional plane and extracting the oval scanning trajectory as a two-dimensional point set: ; Where, It is The two-dimensional point set of the oval scanning trajectory has a total of A two-dimensional point, and Indicates the Two-dimensional point coordinates; Compute the 2D mean vector of a 2D set of points : ; Calculate the coordinates of the center point of a two-dimensional point set : ; Construct a two-dimensional covariance matrix of a two-dimensional point set : ; Where, 、 、 、 are the four elements of the covariance matrix.

[0021] Determining the major and minor axis directions includes Perform eigenvalue decomposition and get The two eigenvalues ​​of The eigenvector corresponding to the largest eigenvalue is in the direction of the long axis of the oval scanning trajectory, and the eigenvector corresponding to the second largest eigenvalue is in the direction of the short axis of the oval scanning trajectory.

[0022] Search for the two endpoints farthest from the center point in the oval scanning trajectory along the long axis and short axis directions respectively, as the long axis and short axis vertex coordinates of the single circle oval scanning trajectory. The long axis vertex coordinate of the forward oval scanning trajectory is marked as 、 , the coordinates of the short axis vertex of the forward oval scanning trajectory are 、 , the coordinate of the long axis vertex of the backward oval scanning trajectory is marked as 、 , the coordinates of the minor axis vertex of the backward oval scanning trajectory are 、 .

[0023] Calculating the rotation angle of the uncorrected scanning coordinate system to the actual coordinate system around the Y axis includes extracting multiple single-circle oval scanning trajectories, projecting the single-circle oval scanning trajectories onto the XOZ plane and ignoring the influence of the Y axis. The forward short axis vertex coordinate is and , the coordinates of the vertex of the backward short axis are and ; Construct the minor axis vector: ; ; Where, is the forward scan vector, is the backward scanning vector, and the projection of the two scanning vectors on the XOZ plane is: ; ; Where, yes Projection on the XOZ plane, yes Projection on the XOZ plane, 、 are the directional components of the forward projection in the X-axis and Z-axis directions, 、 are the directional components of the back projection in the X-axis and Z-axis directions; Calculate the rotation angle around the Y axis of the uncorrected scan coordinate system to the actual coordinate system : .

[0024] Calculating the rotation angle of the uncorrected scanning coordinate system to the actual coordinate system around the X-axis includes extracting multiple single-circle oval scanning trajectories, projecting the single-circle oval scanning trajectories onto the YOZ plane and ignoring the influence of the X-axis. The forward long axis vertex coordinate is and , the coordinates of the vertex of the posterior major axis are and ; Construct the major axis vector: ; ; The projection of the two scan vectors on the YOZ plane is: ; ; Where, yes Projection on the YOZ plane, yes Projection on the YOZ plane, is the directional component of the forward projection in the Y-axis direction, is the directional component of the back projection in the Y-axis direction; Calculate the rotation angle around the X axis of the uncorrected scan coordinate system to the actual coordinate system : .

[0025] Calculating the rotation angle of the uncorrected scanning coordinate system to the actual coordinate system around the Z axis includes extracting multiple single-circle oval scanning trajectories, projecting the single-circle oval scanning trajectories onto the XOY plane and ignoring the influence of the Z axis. The forward long axis vertex coordinate is and , the coordinates of the vertex of the posterior major axis are and ; Construct the major axis vector: ; ; The projection of the two scan vectors on the XOY plane is: ; ; Where, yes Projection on the XOY plane, yes Projection on the XOY plane; Calculate the rotation angle around the X axis of the uncorrected scan coordinate system to the actual coordinate system : .

[0026] The points of the new oval scanning trajectory include the three-dimensional rotation matrix for: ; ; ; ; Where, 、 、 They are 、 、 The average value of 、 、 are three known matrices; Will Applied to the forward oval scanning trajectory and the backward oval scanning trajectory, for each point of the oval scanning trajectory Perform posture compensation to obtain the corrected oval scanning trajectory points : .

[0027] Calculating the scaling factor involves designing the major axis vertex to be , the uncorrected major axis vertex is , the horizontal coordinate values ​​of the two major axis vertices are: ; ; ; Where, The major axis vertex is No. The uncorrected actual major axis vertex value of the circle, The major axis vertex is No. The design long axis vertex value of the circle, yes The maximum value of is the mirror rotation angle, is the scaling factor.

[0028] Correcting the normal vector of the reflector includes the correction angle of the normal vector of the reflector for: ; Where, is the angle between the normal line of the reflector and the motor shaft; Corrected mirror normal vector for: .

[0029] LiDAR scanning system Figure 1 As shown, the projection of the short axis on the XOZ plane is as follows Figure 2 As shown, the major axis is projected on the YOZ plane as Figure 3 As shown, the projection of the major axis on the XOY plane is as follows Figure 4 The present invention conducts an airborne laser radar sighting axis error calibration test. The laser radar is placed horizontally, and three high-precision infrared laser rangefinders are placed above the laser radar device and at the same horizontal position on the left and right sides. The consistency of the three infrared laser rangefinders ensures that the laser scanning plane is parallel to the wall. After determining the plane parallel to the wall, the laser radar is used to perform a circle scanning experiment. The laser radar system records distance data, angle, position and posture data. The laser point cloud coordinate reduction program is used to calculate the laser foot point coordinates. The forward oval scanning trajectory is shown as follows. Figure 5 As shown, the single-circle forward oval scanning trajectory and the oval scanning trajectory are compared. Figure 6shown.

[0030] The projection in the XOZ plane and the comparison of the major and minor axes in the front and back directions are as follows: Figure 7 As shown, the XOZ plane calculation results are as follows Figure 8 As shown, the final calculation is =3.905°; the projection in the YOZ plane and the comparison of the major and minor axes in the forward and backward directions are Figure 9 As shown, the YOZ plane calculation results are as follows Figure 10 As shown, the final calculation is =3.599°; the projection in the XOY plane and the comparison of the major and minor axes in the front and back directions are Figure 11 As shown, the calculation results of XOY plane are as follows Figure 12 As shown, the final calculation is =1.885°.

[0031] The five calculation results of the XOZ plane are shown in Table 1.

[0032] Table 1. Five calculation results of XOZ plane .

[0033] The five calculation results of the YOZ plane are shown in Table 2.

[0034] Table 2. Five calculation results of YOZ plane .

[0035] The five calculation results of the XOY plane are shown in Table 3.

[0036] Table 3. Five calculation results of XOY plane .

[0037] for: .

[0038] The comparison between the corrected forward oval scanning trajectory and the oval scanning trajectory is as follows: Figure 13 As shown in the figure, it can be seen that the point cloud scanning trajectory after correction by the deflection angle correction matrix is ​​parallel to the XOY plane that the laser radar needs to scan. Although the scanning trajectory after correction by the deflection angle correction matrix is ​​parallel to the XOY plane scanned by the laser radar, the size of the oval scanning trajectory still does not meet the design value of the oval size. Therefore, the scaling factor is calculated below to correct the size of the oval scanning trajectory. The laser scanning trajectory point cloud of the design value and the actual value is shown as follows Figure 14 As shown in the figure, it can be seen that the scan value is greater than the design value, so a scaling factor needs to be added for correction. The scaling factor is obtained by calculation. =1.0651972008521895, the correction angle of the normal vector of the reflector is calculated based on the relationship between the scaling factor and the angle proposed in the patent The calculated result is shown in Figure 15. The outer circle is the actual value and the inner circle is the design value. The oval scanning trajectory after the scaling factor is introduced is shown in Figure 15. Figure 16 As shown in the figure, it can be seen that the size of the point cloud trajectory after adding the reflector correction angle correction is the same as the design value point cloud trajectory size.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for correcting the sight axis error of an airborne laser radar with an oval scanning trajectory, characterized in that: Including the points of correcting the oval scanning trajectory and correcting the normal vector of the reflector; A laser radar is used to perform a forward fixed-point scan of the object to be measured to obtain a forward oval scanning trajectory, and a backward fixed-point scan is performed to obtain a backward oval scanning trajectory. The laser radar outputs the measured rotation angle of the rotating mirror, extracts the single-circle oval scanning trajectory, determines the directions of the major and minor axes, calculates the angle of rotation of the uncorrected scanning coordinate system to the actual coordinate system around the Y axis, calculates the angle of rotation of the uncorrected scanning coordinate system to the actual coordinate system around the X axis, and calculates the angle of rotation of the uncorrected scanning coordinate system to the actual coordinate system around the Z axis, and obtains the points of the corrected oval scanning trajectory; Calculate the scaling factor, correct the normal vector of the reflector, and complete the collimation axis error correction.

2. The method for correcting the sight axis error of an airborne laser radar with an oval scanning trajectory according to claim 1, wherein: Determining the major and minor axis directions involves projecting the oval scanning trajectory onto a two-dimensional plane and extracting the oval scanning trajectory as a two-dimensional point set: ； Where, It is The two-dimensional point set of the oval scanning trajectory has a total of A two-dimensional point, and Indicates the Two-dimensional point coordinates; Compute the 2D mean vector of a 2D set of points : ； Calculate the coordinates of the center point of a two-dimensional point set : ； Construct a two-dimensional covariance matrix of a two-dimensional point set : ； Where, 、 、 、 are the four elements of the covariance matrix.

3. The method for correcting the sighting axis error of an airborne laser radar with an oval scanning trajectory according to claim 2, wherein: Determining the major and minor axis directions includes Perform eigenvalue decomposition and get The two eigenvalues ​​of The eigenvector corresponding to the largest eigenvalue is in the direction of the long axis of the oval scanning trajectory, and the eigenvector corresponding to the second largest eigenvalue is in the direction of the short axis of the oval scanning trajectory.

4. The method for correcting the sighting axis error of an airborne laser radar with an oval scanning trajectory according to claim 3, characterized in that: Search for the two endpoints farthest from the center point in the oval scanning trajectory along the long axis and short axis directions respectively, as the long axis and short axis vertex coordinates of the single circle oval scanning trajectory. The long axis vertex coordinate of the forward oval scanning trajectory is marked as 、 , the coordinates of the short axis vertex of the forward oval scanning trajectory are 、 , the coordinate of the long axis vertex of the backward oval scanning trajectory is marked as 、 , the coordinates of the minor axis vertex of the backward oval scanning trajectory are 、 .

5. The method for correcting the sighting axis error of an airborne laser radar with an oval scanning trajectory according to claim 4, characterized in that: Calculating the rotation angle of the uncorrected scanning coordinate system to the actual coordinate system around the Y axis includes extracting multiple single-circle oval scanning trajectories, projecting the single-circle oval scanning trajectories onto the XOZ plane and ignoring the influence of the Y axis. The forward short axis vertex coordinate is and , the coordinates of the vertex of the backward short axis are and ; Construct the minor axis vector: ； ； Where, is the forward scan vector, is the backward scanning vector, and the projection of the two scanning vectors on the XOZ plane is: ； ； Where, yes Projection on the XOZ plane, yes Projection on the XOZ plane, 、 are the directional components of the forward projection in the X-axis and Z-axis directions, 、 are the directional components of the back projection in the X-axis and Z-axis directions; Calculate the rotation angle around the Y axis of the uncorrected scan coordinate system to the actual coordinate system : 。 6. The method for correcting the sighting axis error of an airborne laser radar with an oval scanning trajectory according to claim 5, characterized in that: Calculating the rotation angle of the uncorrected scanning coordinate system to the actual coordinate system around the X-axis includes extracting multiple single-circle oval scanning trajectories, projecting the single-circle oval scanning trajectories onto the YOZ plane and ignoring the influence of the X-axis. The forward long axis vertex coordinate is and , the coordinates of the vertex of the posterior major axis are and ; Construct the major axis vector: ； ； The projection of the two scan vectors on the YOZ plane is: ； ； Where, yes Projection on the YOZ plane, yes Projection on the YOZ plane, is the directional component of the forward projection in the Y-axis direction, is the directional component of the back projection in the Y-axis direction; Calculate the rotation angle around the X axis of the uncorrected scan coordinate system to the actual coordinate system : 。 7. The method for correcting the sighting axis error of an airborne laser radar with an oval scanning trajectory according to claim 6, characterized in that: Calculating the rotation angle of the uncorrected scanning coordinate system to the actual coordinate system around the Z axis includes extracting multiple single-circle oval scanning trajectories, projecting the single-circle oval scanning trajectories onto the XOY plane and ignoring the influence of the Z axis. The forward long axis vertex coordinate is and , the coordinates of the vertex of the posterior major axis are and ; Construct the major axis vector: ； ； The projection of the two scan vectors on the XOY plane is: ； ； Where, yes Projection on the XOY plane, yes Projection on the XOY plane; Calculate the rotation angle around the X axis of the uncorrected scan coordinate system to the actual coordinate system : 。 8. The method for correcting the sighting axis error of an airborne laser radar with an oval scanning trajectory according to claim 7, characterized in that: The points of the new oval scanning trajectory include the three-dimensional rotation matrix for: ； ； ； ； Where, 、 、 They are 、 、 The average value of 、 、 are three known matrices; Will Applied to the forward oval scanning trajectory and the backward oval scanning trajectory, for each point of the oval scanning trajectory Perform posture compensation to obtain the corrected oval scanning trajectory points : 。 9. The method for correcting the sighting axis error of an airborne laser radar with an oval scanning trajectory according to claim 8, characterized in that: Calculating the scaling factor involves designing the major axis vertex to be , the uncorrected major axis vertex is , the horizontal coordinate values ​​of the two major axis vertices are: ； ； ； Where, The major axis vertex is No. The uncorrected actual major axis vertex value of the circle, The major axis vertex is No. The design long axis vertex value of the circle, yes The maximum value of is the mirror rotation angle, is the scaling factor.

10. The method for correcting the sighting axis error of an airborne laser radar with an oval scanning trajectory according to claim 9, characterized in that: Correcting the normal vector of the reflector includes the correction angle of the normal vector of the reflector for: ； Where, is the angle between the normal line of the reflector and the motor shaft; Corrected mirror normal vector for: 。

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