Method for correcting the boresight error of an airborne laser radar with an oval scan trajectory

Abstract

The application discloses an on-board laser radar collimation axis error correction method of an oval scanning track, belongs to the technical field of error correction, and is used for collimation axis error correction. The method comprises the following steps: correcting points of the oval scanning track and correcting a mirror normal vector; using a laser radar to perform forward fixed-point scanning on a to-be-measured object to obtain a forward oval scanning track, performing backward fixed-point scanning to obtain a backward oval scanning track, and obtaining the points of the corrected oval scanning track; calculating a scaling factor, correcting the mirror normal vector, and completing collimation axis error correction. The application does not need external auxiliary equipment, does not depend on ground control points or regular ground object information, is suitable for complex application scenes such as no control and no overlapping area, and improves the adaptability, correction accuracy and engineering practicability of the system. The practicability in a complex outdoor environment is significantly improved, and the application is suitable for no control area and single flight. The application has the track scale distortion correction capability and enhances the spatial consistency of the depth point cloud.

Description

TECHNICAL FIELD

[0001] The application discloses an on-board laser radar boresight error correction method of an oval scanning track and belongs to the technical field of error correction. BACKGROUND

[0002] An on-board laser radar depth measurement system usually adopts an off-axis mirror structure to form an oval scanning track, and the measurement precision of the on-board laser radar depth measurement system is highly dependent on the accuracy of system geometric parameters. As one of core error sources, a boresight error significantly affects the spatial positioning precision of a laser foot point, and further reduces the effectiveness and stability of the entire depth measurement system. The boresight error usually refers to the actual deviation of an ideal angle between a laser emission axis and a rotating axis of a scanning system, and reflects the inaccuracy in the collimation adjustment process of the system. In a laser scanning coordinate system, the boresight error of the on-board laser radar depth measurement system is the error of an angle between a mirror normal line and a motor rotating shaft and the error of an angle between an incident light and the motor rotating shaft. In a system adopting an off-axis elliptical scanning structure, the error will directly cause the overall deflection, rotation or deformation of the scanning track in space, and further cause systematical deviation of point cloud data in the vertical elevation direction and the horizontal position direction. The existence of the angle error between the mirror normal line and the motor rotating shaft will affect the shape of the oval scanning track, that is, when the angle is greater than a design value, the oval scanning track becomes larger, and when the angle is less than the design value, the oval scanning track becomes smaller and affects the coordinates of the laser foot point. The existence of the error of the angle between the incident light and the motor rotating shaft will make the scanning plane of the laser radar not parallel to the actual scanning plane, and make the scanning plane be twisted in space.

[0003] Due to the characteristics of strong directionality, uneven scale, complex propagation path and the like of the error, once the error is not corrected, an overall error band will be caused in the laser depth measurement result, especially in a sea state environment with a large flight height or strong fluctuation, the error amplification effect is more obvious, and the sea bottom topography measurement precision is seriously affected.

[0004] There are three main methods for correcting the boresight error of airborne laser radar systems in the prior art. One is a point cloud registration method based on the overlapping area of the flight strip, which uses the iterative closest point (ICP) algorithm to register the point cloud of the adjacent flight strip overlapping area, minimizes the spatial deviation of the point cloud of the overlapping area of different flight lines to solve the boresight error, but this method depends on the overlapping of the flight strip and is difficult to apply to single flight line or uncontrolled scenes. The second is a calibration method based on feature surface matching, which uses building facades and other planar features to construct a point-to-surface residual function to minimize the boresight error, which is suitable for urban scenes but fails in ocean or wilderness areas without typical ground features. The third is an error modeling method based on scan trajectory structure, which analyzes the trajectory distortion to reverse the platform coordinate system error, which has a certain universality, but does not achieve decoupled modeling of the boresight error source. Compared with the above three methods, the Chinese invention patent application with publication number CN119291658A proposes to subdivide the boresight error into the angle error between the mirror normal and the rotation axis and the angle error between the incident light and the rotation axis, and to construct a least squares error model with six segment lengths by measuring points A, B, C and D to independently solve the two types of errors, which has higher geometric accuracy and theoretical closeness, but relies on auxiliary equipment such as total station, which is not suitable for field unmanned deployment. SUMMARY

[0005] The purpose of the present application is to provide an airborne laser radar boresight error correction method for oval scan trajectory, to solve the problem of boresight error correction in the prior art.

[0006] The airborne laser radar boresight error correction method for oval scan trajectory comprises correcting the points of the oval scan trajectory and correcting the mirror normal vector.

[0007] The laser radar is used to perform forward fixed-point scanning on the object to be measured to obtain a forward oval scan trajectory, and to perform backward fixed-point scanning to obtain a backward oval scan trajectory. The laser radar outputs the measured rotation angle of the rotating mirror. The single-turn oval scan trajectory is extracted, the major and minor axis directions are determined, the angle of rotation of the uncorrected scan coordinate system around the Y axis to the actual coordinate system is calculated, the angle of rotation of the uncorrected scan coordinate system around the X axis to the actual coordinate system is calculated, the angle of rotation of the uncorrected scan coordinate system around the Z axis to the actual coordinate system is calculated, and the points of the corrected oval scan trajectory are obtained.

[0008] The scaling factor is calculated, the mirror normal vector is corrected, and the boresight error correction is completed.

[0009] Determining the major and minor axis directions comprises projecting the oval scan trajectory onto a two-dimensional plane, and then extracting the oval scan trajectory as a two-dimensional point set.

[0010] ;

[0011] In the formula, is the two-dimensional point set of a single circle oval scan trajectory, there are two-dimensional points in total, and denote the th two-dimensional point coordinate;

[0012] calculate the two-dimensional mean vector of the two-dimensional point set :

[0013] ;

[0014] calculate the center point coordinate of the two-dimensional point set :

[0015] ;

[0016] construct the two-dimensional covariance matrix of the two-dimensional point set :

[0017] ;

[0018] wherein, , , , are four elements of the covariance matrix.

[0019] determining the long and short axis directions includes performing eigenvalue decomposition on to obtain two eigenvalues of , the eigenvector corresponding to the largest eigenvalue is the direction of the long axis of the oval scan trajectory, and the eigenvector corresponding to the second largest eigenvalue is the direction of the short axis of the oval scan trajectory.

[0020] search for the two end points farthest from the center point in the oval scan trajectory along the long axis and short axis directions respectively, as the long axis and short axis vertex coordinates of the single circle oval scan trajectory, the forward oval scan trajectory long axis vertex coordinates are marked as , , the forward oval scan trajectory short axis vertex coordinates are , , the backward oval scan trajectory long axis vertex coordinates are marked as , , and the backward oval scan trajectory short axis vertex coordinates are , .

[0021] calculating the angle of rotation of the uncorrected scan coordinate system around the Y axis to the actual coordinate system includes extracting a plurality of single circle oval scan trajectories, projecting the single circle oval scan trajectory onto the XOZ plane and ignoring the Y axis influence, the forward short axis vertex coordinates are and , the back short axis vertex coordinates are and ;

[0022] Construct the short axis vector:

[0023] ;

[0024] ;

[0025] In the formula, is the forward scanning vector, is the back scanning vector, the projection of the two scanning vectors in the XOZ plane is:

[0026] ;

[0027] ;

[0028] In the formula, is the projection in the XOZ plane, is the projection in the XOZ plane, , is the direction component of the forward projection in the X-axis and Z-axis directions, , is the direction component of the back projection in the X-axis and Z-axis directions;

[0029] Calculate the angle of rotation of the uncorrected scanning coordinate system to the actual coordinate system around the Y-axis :

[0030] .

[0031] Calculate the angle of rotation of the uncorrected scanning coordinate system to the actual coordinate system around the X-axis, including extracting a plurality of single-turn oval scanning trajectories, projecting the single-turn oval scanning trajectories to the YOZ plane and ignoring the X-axis influence, the forward long axis vertex coordinates are and , the back long axis vertex coordinates are and ;

[0032] Construct the long axis vector:

[0033] ;

[0034] ;

[0035] The projection of the two scanning vectors in the YOZ plane is:

[0036] ;

[0037] ;

[0038] wherein, is the projection in the YOZ plane, is the projection in the YOZ plane, is the directional component of the forward projection in the Y axis direction, is the directional component of the backward projection in the Y axis direction;

[0039] Calculate the angle of rotation of the uncorrected scanning coordinate system around the X axis to the actual coordinate system :

[0040] .

[0041] Calculate the angle of rotation of the uncorrected scanning coordinate system around the Z axis to the actual coordinate system includes extracting a plurality of single-turn oval scanning trajectories, projecting the single-turn oval scanning trajectory to the XOY plane and ignoring the Z axis effect, the forward long axis vertex coordinates are and , and the backward long axis vertex coordinates are and ;

[0042] Construct the long axis vector:

[0043] ;

[0044] ;

[0045] The projection of the two scanning vectors in the XOY plane is:

[0046] ;

[0047] ;

[0048] wherein, is the projection in the XOY plane, is the projection in the XOY plane;

[0049] Calculate the angle of rotation of the uncorrected scanning coordinate system around the X axis to the actual coordinate system :

[0050] .

[0051] Obtain the points of the new oval scanning trajectory including a three-dimensional rotation matrix :

[0052] ;

[0053] ;

[0054] ;

[0055] ;

[0056] wherein, , , are the average values of , , ; , , are three known matrices;

[0057] Applying to the forward and backward oval scan trajectories, the points of each oval scan trajectory are pose compensated to obtain the points of the corrected oval scan trajectories:

[0058] .

[0059] The scaling factor is calculated including that the design major axis vertex is , the uncorrected major axis vertex is , and the horizontal coordinate values of the two major axis vertices are:

[0060] ;

[0061] ;

[0062] ;

[0063] wherein, is the uncorrected actual major axis vertex value of the th circle with the design major axis vertex , is the design major axis vertex value of the th circle with the design major axis vertex , is the maximum value of , is the rotation angle of the mirror, is the scaling factor.

[0064] The correction of the mirror normal vector includes that the correction angle of the mirror normal vector is:

[0065] ;

[0066] Where, is the angle between the normal line of the reflector and the motor shaft;

[0067] Corrected mirror normal vector for:

[0068] .

[0069] 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

[0070] Figure 1 This is a simplified diagram of the LiDAR scanning system;

[0071] Figure 2 It is the projection of the minor axis on the XOZ plane;

[0072] Figure 3 It is the projection of the long axis on the YOZ plane;

[0073] Figure 4 It is the projection of the long axis on the XOY plane;

[0074] Figure 5 It is the forward oval scanning trajectory diagram;

[0075] Figure 6 A comparison diagram of the forward oval scanning trajectory and the oval scanning trajectory of a single circle;

[0076] Figure 7 The projection in the XOZ plane and the comparison of the major and minor axes in the front and back directions;

[0077] Figure 8 This is the calculation result diagram of the XOZ plane;

[0078] Figure 9 The projection in the YOZ plane and the comparison of the major and minor axes in the forward and backward directions;

[0079] Figure 10 This is the calculation result diagram of the YOZ plane;

[0080] 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;

[0081] Figure 12 The result figure for XOY plane is calculated;

[0082] Figure 13 The contrast figure for the corrected forward oval scan trajectory and the oval scan trajectory is calculated;

[0083] Figure 14 The contrast figure for the scan value and the design value is calculated;

[0084] Figure 15 The result figure for the scaling factor and the correction angle is calculated;

[0085] Figure 16 The result figure for the oval scan trajectory after the correction of the introduced scaling factor is calculated. DETAILED DESCRIPTION

[0086] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application are described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than 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.

[0087] The on-board laser radar boresight error correction method for the oval scan trajectory comprises correcting the points of the oval scan trajectory and correcting the mirror normal vector;

[0088] The forward oval scan trajectory is obtained by using the laser radar to perform forward fixed-point scanning on the object to be measured, and the backward oval scan trajectory is obtained by performing backward fixed-point scanning. The laser radar outputs the measured rotating angle of the rotating mirror. The single-turn oval scan trajectory is extracted, the long-short axis direction is determined, the angle of rotation of the uncorrected scan coordinate system around the Y axis to the actual coordinate system is calculated, the angle of rotation of the uncorrected scan coordinate system around the X axis to the actual coordinate system is calculated, the angle of rotation of the uncorrected scan coordinate system around the Z axis to the actual coordinate system is calculated, and the points of the corrected oval scan trajectory are obtained.

[0089] The scaling factor is calculated, the mirror normal vector is corrected, and the boresight error correction is completed.

[0090] The determination of the long-short axis direction comprises projecting the oval scan trajectory to a two-dimensional plane, and then extracting the oval scan trajectory as a two-dimensional point set:

[0091]

[0092] In the formula, is the two-dimensional point set of the mth oval scan trajectory, and there are m×n two-dimensional points.​ and represent the th two-dimensional point coordinate;

[0093] calculating a two-dimensional mean vector of the two-dimensional point set

[0094]

[0095] calculating a center point coordinate of the two-dimensional point set

[0096]

[0097] constructing a two-dimensional covariance matrix of the two-dimensional point set

[0098]

[0099] wherein are four elements of the covariance matrix.

[0100] determining the long and short axis directions includes performing eigenvalue decomposition on to obtain two eigenvalues of , the eigenvector corresponding to the largest eigenvalue is the direction of the long axis of the oval scan trajectory, and the eigenvector corresponding to the second largest eigenvalue is the direction of the short axis of the oval scan trajectory.

[0101] searching for two end points farthest from the center point in the oval scan trajectory along the long axis and the short axis directions respectively, as the long axis and the short axis vertex coordinates of the single-turn oval scan trajectory, the forward oval scan trajectory long axis vertex coordinates are marked as , the forward oval scan trajectory short axis vertex coordinates are , the backward oval scan trajectory long axis vertex coordinates are marked as , and the backward oval scan trajectory short axis vertex coordinates are .

[0102] calculating the angle of rotation of the uncorrected scan coordinate system around the Y axis to the actual coordinate system includes extracting a plurality of single-turn oval scan trajectories, projecting the single-turn oval scan trajectories onto the XOZ plane and ignoring the Y axis influence, the forward short axis vertex coordinates are and , and the backward short axis vertex coordinates are and .​​​​​​​​​​​​​

[0103] Construct the short axis vector:

[0104] ;

[0105] ;

[0106] wherein, is the forward scanning vector, is the backward scanning vector, the projection of the two scanning vectors in XOZ plane is:

[0107] ;

[0108] ;

[0109] wherein, is the projection in XOZ plane, is the projection in XOZ plane, , is the direction component of the forward projection in X axis and Z axis direction, , is the direction component of the backward projection in X axis and Z axis direction;

[0110] Calculate the angle of rotation of the uncorrected scanning coordinate system around Y axis to the actual coordinate system :

[0111] .

[0112] The calculation of the angle of rotation of the uncorrected scanning coordinate system around X axis to the actual coordinate system includes extracting a plurality of single-turn oval scanning trajectories, projecting the single-turn oval scanning trajectories to YOZ plane and ignoring the influence of X axis, the forward long axis vertex coordinates are and , and the backward long axis vertex coordinates are and ;

[0113] Construct the long axis vector:

[0114] ;

[0115] ;

[0116] The projection of the two scanning vectors in YOZ plane is:

[0117] ;

[0118] ;

[0119] wherein, is the projection in YOZ plane, is the projection in YOZ plane, is the forward direction component in Y axis direction, is the backward direction component in Y axis direction;

[0120] calculating the angle of rotation of the uncorrected scanning coordinate system around the X axis to the actual coordinate system :

[0121] .

[0122] calculating the angle of rotation of the uncorrected scanning coordinate system around the Z axis to the actual coordinate system includes extracting a plurality of single-turn oval scanning trajectories, projecting the single-turn oval scanning trajectories to the XOY plane and ignoring the Z axis effect, the forward long axis vertex coordinates are and , and the backward long axis vertex coordinates are and ;

[0123] constructing a long axis vector:

[0124] ;

[0125] ;

[0126] the projection of the two scanning vectors in the XOY plane is:

[0127] ;

[0128] ;

[0129] wherein, is the projection in XOY plane, is the projection in XOY plane;

[0130] calculating the angle of rotation of the uncorrected scanning coordinate system around the X axis to the actual coordinate system :

[0131] .

[0132] obtaining the points of the new oval scanning trajectory includes a three-dimensional rotation matrix :

[0133] ;

[0134] ;

[0135] ;

[0136] ;

[0137] wherein, , , are respectively , , the average value of , , are three known matrices;

[0138] applying to the forward and backward oval scan trajectories, the points of each oval scan trajectory are pose compensated to obtain the points of the corrected oval scan trajectories:

[0139] .

[0140] The calculation of the scaling factor includes that the design long axis vertex is , the uncorrected long axis vertex is , and the horizontal coordinate values of the two long axis vertices are:

[0141] ;

[0142] ;

[0143] ;

[0144] wherein, is the uncorrected actual long axis vertex value of the th circle with the long axis vertex being , is the design long axis vertex value of the th circle with the long axis vertex being , is the maximum value of , is the rotation angle of the mirror, is the scaling factor.

[0145] The correction of the mirror normal vector includes that the correction angle of the mirror normal vector is:

[0146] ;

[0147] wherein, The angle between the mirror normal and the motor rotation axis;

[0148] The corrected mirror normal vector The angle between the mirror normal and the motor rotation axis is:

[0149] .

[0150] The laser radar scanning system is shown in Figure 1 The short axis is projected in the XOZ plane as shown in Figure 2 The long axis is projected in the YOZ plane as shown in Figure 3 The long axis is projected in the XOY plane as shown in Figure 4 The present application carries out the on-board laser radar collimation axis error calibration test, places the laser radar horizontally, places three high-precision infrared laser range finders at the same horizontal position above and left and right of the laser radar equipment respectively, ensures that the laser scanning plane is parallel to the wall surface through the consistency of the three infrared laser ranging; after determining the plane parallel to the wall surface, uses the laser radar to carry out the circle scanning experiment, the laser radar system records the distance data, angle, position and attitude data, uses the laser point cloud coordinate reduction program to calculate the laser foot point coordinates, the forward oval circular scanning trajectory is shown in Figure 5 The single-circle forward oval circular scanning trajectory and the oval circular scanning trajectory are compared as shown in Figure 6 .

[0151] The XOZ plane projection and the forward-backward long-short axis comparison are shown in Figure 7 The XOZ plane calculation result is shown in Figure 8 Finally, the calculation result is = 3.905 °; the YOZ plane projection and the forward-backward long-short axis comparison are shown in Figure 9 The YOZ plane calculation result is shown in Figure 10 Finally, the calculation result is = 3.599 °; the XOY plane projection and the forward-backward long-short axis comparison are shown in Figure 11 The XOY plane calculation result is shown in Figure 12 Finally, the calculation result is = 1.885 °.

[0152] The five calculation results of the XOZ plane are shown in Table 1.

[0153] Table 1, the five calculation results of the XOZ plane

[0154] .

[0155] The five calculation results of the YOZ plane are shown in Table 2.

[0156] Table 2, the five calculation results of the YOZ plane

[0157] .

[0158] The five calculation results of the XOY plane are shown in Table 3.

[0159] Table 3. Five calculation results of XOY plane

[0160] .

[0161] for:

[0162] .

[0163] 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.

[0164] 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; 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; 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; 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: 。 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 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.

3. The method for correcting the sighting axis error of an airborne laser radar with an oval scanning trajectory according to claim 2, wherein: 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 、 .

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: 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 : 。 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 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 : 。 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 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 : 。 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: 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 : 。

Images