Method for measuring and calibrating in-orbit parameters of spatially constrained swing-scan load

Abstract

The application provides a space-restriction-based swing-scan load on-orbit inner parameter measurement and calibration method, S1, obtaining forward and reverse scan images of the same area of a load nadir point through a bidirectional swing-scan imaging system; S2, obtaining same-name image point pairs of the overlapping area of the forward and reverse scan images through extraction of image control points; S3, solving the line-of-sight vectors of the same-name image points in the geocentric fixed coordinate system based on a strict geometric positioning model of the bidirectional swing-scan imaging system through satellite attitude and orbit data; S4, constructing a constraint equation according to the geometric constraint relationship of the same-name image points in the object field, and solving model parameters based on the least square principle to realize on-orbit uncontrolled inner orientation parameter solving. The space-restriction-based swing-scan load on-orbit inner parameter measurement and calibration method of the application breaks the dependence on the strong on-orbit maneuvering capability of a satellite and a high-precision control reference, and realizes on-orbit calibration of the inner orientation parameters of a bidirectional swing-scan photoelectric detection and imaging load.

Description

Technical Field

[0001] This invention relates to the field of spaceborne spectral imaging technology, specifically to a method for on-orbit intrinsic parameter measurement and calibration of space-constrained oscillating payloads. Background Technology

[0002] On-orbit geometric calibration of space-based optoelectronic detection and imaging payloads is one of the key steps to ensure the level of subsequent quantitative application of images. It plays a vital role in civilian and military fields such as space-based remote sensing, photogrammetry, and space target positioning and tracking.

[0003] Currently, the commonly used on-orbit geometric calibration method for space-based optoelectronic detection and imaging payloads mainly uses high-precision spatial references, such as ground geometric calibration fields, reference image control points, and stars, to achieve precise calibration of the sensor's strict geometric imaging model parameters, mainly including interior orientation parameters and exterior orientation parameters, thereby realizing the geometric positioning of on-orbit images. However, this method mainly faces two problems: (1) It is difficult and costly to obtain high-precision spatial references; First, the construction and maintenance costs of geometric calibration fields are high, and they are difficult to achieve immediate results due to the influence of satellite transit time and weather conditions of the calibration field during transit; Second, due to the influence of radiometric-geometric differences, the extraction and accuracy of current image control points are difficult to meet the application requirements of all spectral bands. On-orbit geometric positioning methods based on stars are only applicable to satellites with the ability to respond to star observations. (2) The on-orbit solution method is complex; The on-orbit geometric positioning model parameter solution is mainly based on iterative least squares theory. When the number of control points is large, a lot of computing resources are required, resulting in low efficiency and significant influence from abnormal control point data. Meanwhile, the current on-orbit geometric calibration method without ground control points has the following problems that need to be solved: (1) It is highly dependent on the satellite's on-orbit maneuverability; the uncontrolled positioning method that obtains observation data under different states through attitude maneuver and then corrects system errors is only applicable to ultra-agile satellites such as the French Pleiades, and its attitude control process is prone to introducing larger positioning errors. This method is still in the research stage; (2) It depends on DEM data; the DEM-assisted uncontrolled positioning method needs to obtain a spatial reference through DEM matching. In essence, it is still spatial positioning, and DEM matching introduces new errors, resulting in low efficiency in actual application.

[0004] Therefore, it is urgent to solve the problem that the on-orbit geometric calibration process of actual optoelectronic payloads relies on a large number of high-precision control references, complex calculation methods, and the strong maneuverability of satellites, and to invent a low-cost, simple, and highly reliable on-orbit geometric calibration method for optoelectronic payloads. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating the on-orbit azimuth parameters of a bidirectional oscillating sweep payload based on geometric constraints, in order to meet the high-precision positioning requirements of future space-based optoelectronic detection and imaging payloads in the existing technology, and to meet the needs of practical applications.

[0006] Therefore, the above-mentioned objectives of the present invention are achieved through the following technical solutions:

[0007] A method for on-orbit intrinsic parameter measurement and calibration of space-constrained oscillating loads includes the following steps:

[0008] S1, acquires forward and reverse scan images of the same area at the payload's nadir point through a bidirectional oscillating scanning imaging system;

[0009] S2, obtain the same image point pairs in the overlapping area of ​​the forward and reverse scan images by extracting image control points;

[0010] S3, using satellite attitude and orbit data, calculates the line-of-sight vector of the corresponding image points in the forward and reverse scan images in the geocentric fixed coordinate system based on the rigorous geometric positioning model of the bidirectional oscillating imaging system;

[0011] S4. Based on the geometric constraint relationship of the object space of the same image point, construct the constraint equation, and calculate the model parameters based on the least squares principle to realize the solution of the uncontrolled interior orientation parameters in orbit.

[0012] S5. Based on the interior orientation parameters calculated in step S4, correct the geometric positioning model of the bidirectional oscillating scanning imaging system.

[0013] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0014] As a preferred technical solution of the present invention: In step S1, an imaging system with a bidirectional scanning mode mounted on a low-orbit satellite platform is used to obtain a forward scanning image at the bidirectional scanning payload at time t1; and to obtain a reverse scanning image at the bidirectional scanning payload at time t2.

[0015] As a preferred technical solution of the present invention: in step S2, the image control points are extracted based on the Harris operator to obtain a set of corresponding image points.

[0016]

[0017] Where TPS is the extracted set of images with the same name; and These are the i-th corresponding image points of the forward scan image Fdimg and the reverse scan image Bdimg, respectively.

[0018] As a preferred technical solution of the present invention: in step S2, the corresponding image point pairs in the overlapping area of ​​the obtained forward and reverse scan images are eliminated by the RANSAC algorithm to eliminate the influence of mismatch.

[0019] As a preferred technical solution of the present invention, step S3 includes the following steps:

[0020] S3.1, Construct a rigorous geometric positioning model for the space-based bidirectional oscillating sweep load. The expression for the oscillating sweep positioning model is as follows:

[0021] (1)

[0022] in, Image points in the image pixel coordinate system The direction vector of the object point in the geocentric fixed coordinate system, where, This is the position vector of the satellite projection center in the geocentric fixed coordinate system. It is a scaling factor; Scanning angle of the scanning mirror The corresponding planar reflection matrix; The scanning angle value of the scanning mirror; This represents the transformation relationship between the geocentric inertial coordinate system and the geocentric fixed coordinate system; This is the transformation matrix from the satellite's body coordinate system to the geocentric inertial coordinate system, typically containing the satellite's attitude angles. calculate; The three attitude angles of the satellite are: pitch angle, roll angle, and yaw angle; The bidirectional sweeping imaging system is defined by its calibrated mounting matrix in the satellite's body coordinate system, and the three mounting angles of the mounting matrix are shown. The satellite was precisely calibrated before launch. For the load, there are three mounting angles; The coordinates of the principal point of the bidirectional oscillating scanning imaging system in the pixel coordinate system; This refers to the principal point offset error; The offset error of the image point on the image plane; The dimensions of the pixel in the x and y directions; The main distance of the bidirectional oscillating imaging system; This refers to the principal distance error. Represents the normalized unit vector;

[0023] S3.2, a two-dimensional pointing angle model is used to characterize the outgoing vector in the coordinate system of the bidirectional oscillating imaging system:

[0024]

[0025] in, , To calibrate the parameters for the two-dimensional pointing angle model, (r, c) represents the pixel row and column coordinates. Let it be the exit vector in the coordinate system of its corresponding bidirectional oscillating imaging system. Let be the two-dimensional pointing angle of pixel (r,c) in the x and y directions.

[0026] As a preferred technical solution of the present invention, step S4 includes the following steps:

[0027] S4.1 Calculate the ground coordinates of the corresponding image points. Using the pair of corresponding image points TP1 and TP2 obtained in step S2, and based on the preliminary ground calibration of the interior and exterior orientation elements, as well as the position and attitude data of the on-orbit satellite, calculate the position coordinates of the object point corresponding to the corresponding image point in the geocentric fixed coordinate system. ;

[0028] S4.2, Based on geometric constraints, construct a system of linear equations. According to the strict geometric localization model in step S3, the localization equations for corresponding image points in the forward and reverse scan images are as follows:

[0029] Frontal scan image:

[0030] (3)

[0031] Reverse image:

[0032] (4)

[0033] Wherein, Fi and Bi represent the i-th corresponding image point in the forward and reverse scan images, respectively;

[0034] S4.3, construct geometric constraint relationships based on the consistency of the object direction of the corresponding image points. The required interior orientation parameters should simultaneously satisfy equations (3) and (4) in step S4.2, then we can obtain...

[0035]

[0036] In the formula, , Let be the interior orientation parameter to be solved;

[0037] S4.4, based on the least squares method to solve the internal orientation parameters of the load, the following linear non-homogeneous equation system is obtained:

[0038]

[0039] Right now

[0040]

[0041] in,

[0042] The least squares method can be used to achieve high-precision calculation of the on-orbit orientation parameters of the bidirectional oscillating photoelectric payload:

[0043]

[0044] Where N is the number of image points with the same name.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] This invention presents a spatially constrained method for on-orbit intrinsic parameter measurement and calibration of a swiveling payload. It utilizes a bidirectional swiveling imaging system and the extraction of image control points to obtain corresponding image point pairs from the payload's nadir image. By constructing constraint equations based on the geometric constraint relationship of consistent object space of these corresponding image points, the intrinsic orientation parameters of the bidirectional swiveling imaging system are calculated. This enables on-orbit calibration of the intrinsic orientation parameters of the swiveling payload's rigorous geometric positioning model, solving the problem of dependence on numerous high-precision control references for on-orbit geometric calibration and eliminating reliance on the satellite's strong on-orbit maneuverability and high-precision control references. This spatially constrained method for on-orbit intrinsic parameter measurement and calibration avoids the problems arising in the parameter calculation of on-orbit geometric positioning models based on iterative least squares theory. It provides a simpler on-orbit calibration method for payload intrinsic orientation parameters, with lower dependence on the satellite's strong on-orbit maneuverability and high-precision control references, and higher on-orbit calibration reliability. This invention provides an on-orbit calibration method for the internal orientation parameters of a bidirectional oscillating photoelectric payload based on geometric constraints. This method eliminates the reliance on the satellite's strong on-orbit maneuverability and high-precision control benchmarks, while reducing the cost of on-orbit calibration of photoelectric payloads and improving the reliability of on-orbit calibration. It has great application prospects in the field of high-precision positioning of space-based photoelectric detection and imaging payloads. Attached Figure Description

[0047] Figure 1 Flowchart of the on-orbit intrinsic parameter measurement and calibration method for space-constrained oscillating sweep loads;

[0048] Figure 2 This is a schematic diagram of a space-based two-way oscillating sweep payload imaging system. Detailed Implementation

[0049] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0050] Example 1

[0051] This invention provides a method for on-orbit intrinsic parameter measurement and calibration of oscillating sweep loads based on spatial constraints.

[0052] like Figure 1 As shown, firstly, the bidirectional scanning imaging system acquires front and back scan images of the same area, different positions, and different observation angles of the payload's sub-satellite point. Then, by extracting image control points, pairs of corresponding image points in the overlapping area of ​​the front and back scan images are obtained. Secondly, based on the satellite attitude and orbit data, the line-of-sight vector of the corresponding image points in the geocentric fixed coordinate system is calculated using the rigorous geometric positioning model of the bidirectional scanning imaging system. Finally, constraint equations are constructed based on the consistency of the object space of the corresponding image points, and the model parameters are calculated based on the least squares principle to achieve the calculation of the uncontrolled interior orientation parameters in orbit.

[0053] By extracting corresponding points from forward and reverse scan images of the same area, different orbit positions, and different observation angles of the bidirectional oscillating sweep payload, geometric constraints are constructed to achieve on-orbit calibration of the azimuth parameters within the strict geometric positioning model of the oscillating sweep payload. This solves the problem of on-orbit geometric calibration relying on a large number of high-precision control references, and eliminates the dependence on the satellite's strong on-orbit maneuverability and high-precision control references, thus realizing on-orbit calibration of the azimuth parameters within the bidirectional oscillating sweep photoelectric detection and imaging payload.

[0054] The present invention provides a method for on-orbit intrinsic parameter measurement and calibration of a space-constrained sweeping load, which specifically includes the following steps:

[0055] S1. Obtain bidirectional sweep observation data for the same area:

[0056] like Figure 2 As shown, the bidirectional scanning imaging system is mounted on a low-Earth orbit satellite platform. At time t1, the bidirectional scanning payload is in the forward scanning imaging process (shown by the solid box in the figure); at time t2, the bidirectional scanning payload is in the reverse scanning imaging process (shown by the dashed box in the figure). Figure 2 The shaded area shown is the front and back scan images of the same area at different orbital positions and observation angles acquired by the bidirectional oscillating scanning imaging payload. This data lays the foundation for on-orbit uncontrolled positioning.

[0057] Among them, the bidirectional oscillating scanning imaging system refers to an imaging system that adopts a bidirectional oscillating scanning mode.

[0058] In this invention, "payload" refers to a bidirectional scanning imaging system mounted on a low-Earth orbit satellite platform.

[0059] Step S2. Extraction of corresponding image points from both front and back scan images:

[0060] The Harris corner extraction algorithm is used to obtain uniformly distributed pairs of corresponding image points from the overlapping area of ​​the front and back scan images. The RANSAC algorithm is then used to eliminate the influence of mismatches, ensuring the accuracy of the corresponding image point extraction. The corresponding image point pairs are represented as follows:

[0061]

[0062] Where TPS is the extracted set of images with the same name; and These are the i-th corresponding image points of the forward scan image Fdimg and the reverse scan image Bdimg, respectively.

[0063] In step S3.1, the rigorous geometric positioning model for the bidirectional oscillating sweep load is constructed:

[0064] Based on the geometric imaging principle of the bidirectional oscillating imaging system, a rigorous geometric positioning model for the space-based bidirectional oscillating payload is constructed, and its oscillating positioning model expression is as follows:

[0065] (1)

[0066] in, Image points in the image pixel coordinate system The direction vector of the object point in the geocentric fixed coordinate system;

[0067] This is the position vector of the satellite projection center in the geocentric fixed coordinate system.

[0068] It is a scaling factor;

[0069] Scanning angle of the scanning mirror The corresponding planar reflection matrix;

[0070] The scanning angle value of the scanning mirror;

[0071] This represents the transformation relationship between the geocentric inertial coordinate system and the geocentric fixed coordinate system;

[0072] This is the transformation matrix from the satellite's body coordinate system to the geocentric inertial coordinate system, typically containing the satellite's attitude angles. calculate;

[0073] The three attitude angles of the satellite are: pitch angle, roll angle, and yaw angle;

[0074] The bidirectional scanning imaging system is defined by its calibrated mounting matrix in the satellite's body coordinate system, and the three mounting angles of the mounting matrix are shown. The satellite was precisely calibrated before launch.

[0075] For the load, there are three mounting angles;

[0076] The coordinates of the principal point of the bidirectional oscillating imaging system in the pixel coordinate system;

[0077] This refers to the principal point offset error;

[0078] The offset error of the image point on the image plane;

[0079] The dimensions of the pixel in the x and y directions;

[0080] The main distance of the bidirectional oscillating imaging system;

[0081] This refers to the principal distance error.

[0082] This represents the normalized unit vector.

[0083] As shown in formula (1), the principal point, principal distance, and distortion are internal orientation parameters of the sweeping load, and the installation angle between the bidirectional sweeping imaging system and the satellite platform is the external orientation parameter of the load. On-orbit positioning is achieved by accurately calculating the internal and external orientation parameters to correct the positioning model parameters.

[0084] In step S3.2, a two-dimensional pointing angle model is used to characterize the outgoing vector in the coordinate system of the bidirectional oscillating imaging system:

[0085]

[0086] in, , To calibrate the parameters for the two-dimensional pointing angle model, (r, c) represents the pixel row and column coordinates. Let it be the exit vector in the coordinate system of its corresponding bidirectional oscillating imaging system. Let be the two-dimensional pointing angle of pixel (r,c) in the x and y directions.

[0087] Wherein, the two-dimensional pointing angle model is used to represent the outgoing vector in the coordinate system of the bidirectional oscillating imaging system, then formula (1) can be simplified as follows:

[0088] (2)

[0089] The definitions of each variable are the same as in equation (1) above.

[0090] In step S4.1, the ground coordinates of corresponding image points are calculated based on the principle of forward intersection:

[0091] like Figure 2 As shown, TP1 and TP2 are a pair of image points with the same name obtained in step 2. Based on the preliminary internal and external orientation elements of the ground and the position and attitude data of the satellite in orbit, the position coordinates of the object point corresponding to the image point in the geocentric fixed coordinate system can be calculated based on the forward intersection principle. .

[0092] S4.2, Constructing a system of linear equations based on geometric constraints.

[0093] Based on the rigorous localization model, the localization equations for corresponding image points in both forward and reverse scans are as follows:

[0094] Frontal scan image:

[0095] (3)

[0096] Reverse image:

[0097] (4)

[0098] Wherein, Fi and Bi represent the i-th corresponding image point in the forward and reverse scan images, respectively;

[0099] In the positioning model, all transformation matrices are unit rotation matrices, changing only the vector direction without changing the vector magnitude. Therefore, the above equations can be simplified as follows:

[0100] Localization equations for corresponding image points in forward and reverse scan images:

[0101] (5)

[0102] (6)

[0103] After normalization, we get:

[0104] (7)

[0105] (8)

[0106] Right now

[0107]

[0108] In the above formula, the satellite position at the imaging time corresponding to the corresponding image points, the object-space coordinates of the corresponding image points, and the corresponding rotation matrix are all known quantities. Since TP1 and TP2 are a pair of acquired corresponding image points, that is, they correspond to the same object-space point, the following formula holds:

[0109]

[0110] Therefore, in step S4.3, constraint equations are constructed based on the geometric constraint relationship of consistent object orientation of corresponding image points. The required interior orientation parameters should simultaneously satisfy the above equation, thus yielding the following result.

[0111]

[0112] In the above formula, , This is the interior orientation parameter that we need to solve for.

[0113] In step S4.4, the load orientation parameters are calculated using the least squares method:

[0114] When there are N pairs of identical image points in both forward and reverse scans, the following system of linear non-homogeneous equations can be obtained:

[0115]

[0116] Right now

[0117]

[0118] in,

[0119] The least squares method can be used to achieve high-precision calculation of the on-orbit orientation parameters of the bidirectional oscillating photoelectric payload:

[0120]

[0121] Where N is the number of image points with the same name, and the other quantities are the same as those mentioned above.

[0122] S5. Based on the interior orientation parameters calculated in step S4, the geometric positioning model of the bidirectional oscillating imaging system is corrected. Specifically, the interior orientation parameters of the bidirectional oscillating imaging system are corrected, thus realizing the calibration of the interior orientation parameters of the bidirectional oscillating imaging system.

[0123] This invention proposes a spatially constrained on-orbit intrinsic parameter measurement and calibration method for bidirectional oscillating imaging payloads, taking into account the relatively stable internal geometric relationship of the payload during actual on-orbit operation. Based on the spatial overlap relationship between imaging data of the same area, different orbit positions, and different observation angles acquired by the bidirectional oscillating imaging system, a corresponding image point extraction algorithm is used to obtain a large number of uniformly distributed corresponding image points in the overlapping area of ​​the forward and reverse scan images. The azimuth parameters of the bidirectional oscillating payload are calculated through the geometric constraint relationship between the corresponding image points. This invention does not adopt the traditional method of calibrating the intrinsic parameters of the bidirectional oscillating imaging system based on a large number of high-precision control points, thus eliminating the dependence on high-precision ground calibration fields and high-precision control points, greatly reducing the cost of on-orbit calibration, and improving the reliability of on-orbit calibration.

[0124] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for on-orbit intrinsic parameter measurement and calibration of space-constrained sweeping loads, comprising the following steps: S1, acquires forward and reverse scan images of the same area at the payload's nadir point through a bidirectional oscillating scanning imaging system; S2, obtain the same image point pairs in the overlapping area of ​​the forward and reverse scan images by extracting image control points; S3, using satellite attitude and orbit data, calculates the line-of-sight vector of the corresponding image points in the forward and reverse scan images in the geocentric fixed coordinate system based on the rigorous geometric positioning model of the bidirectional oscillating imaging system; S4. Based on the geometric constraint relationship of the object space of the same image point, construct the constraint equation, and calculate the model parameters based on the least squares principle to realize the solution of the uncontrolled interior orientation parameters in orbit. S5. Based on the interior orientation parameters calculated in step S4, correct the geometric positioning model of the bidirectional oscillating scanning imaging system. Step S3 includes the following steps: S3.1, Construct a rigorous geometric positioning model for the space-based bidirectional oscillating sweep load. The expression for the oscillating sweep positioning model is as follows: （1） in, Image points in the image pixel coordinate system The direction vector of the object point in the geocentric fixed coordinate system, where, This is the position vector of the satellite projection center in the geocentric fixed coordinate system. It is a scaling factor; Scanning angle of the scanning mirror The corresponding planar reflection matrix; The scanning angle value of the scanning mirror; This represents the transformation relationship between the geocentric inertial coordinate system and the geocentric fixed coordinate system; This is the transformation matrix from the satellite's body coordinate system to the geocentric inertial coordinate system, typically containing the satellite's attitude angles. calculate; The three attitude angles of the satellite are: pitch angle, roll angle, and yaw angle; The bidirectional sweeping imaging system is defined by its calibrated mounting matrix in the satellite's body coordinate system, and the three mounting angles of the mounting matrix are... The satellite was precisely calibrated before launch. For the load, there are three mounting angles; The coordinates of the principal point of the bidirectional oscillating scanning imaging system in the pixel coordinate system; This refers to the principal point offset error; The offset error of the image point on the image plane; The dimensions of the pixel in the x and y directions; The main distance of the bidirectional oscillating imaging system; Main distance error; Represents the normalized unit vector; S3.2, a two-dimensional pointing angle model is used to characterize the outgoing vector in the coordinate system of the bidirectional oscillating imaging system: in, , To calibrate the parameters for the two-dimensional pointing angle model, (r, c) represents the pixel row and column coordinates. Let it be the exit vector in the coordinate system of its corresponding bidirectional oscillating imaging system. Let (r, c) be the two-dimensional pointing angle of the pixel (r, c) in the x and y directions; Step S4 includes the following steps: S4.1 Calculate the ground coordinates of the corresponding image points. Using the pair of corresponding image points TP1 and TP2 obtained in step S2, and based on the preliminary ground calibration of the interior and exterior orientation elements, as well as the position and attitude data of the on-orbit satellite, calculate the position coordinates of the object point corresponding to the corresponding image point in the geocentric fixed coordinate system. ; S4.2, Based on geometric constraints, construct a system of linear equations. According to the strict geometric localization model in step S3, the localization equations for corresponding image points in the forward and reverse scan images are as follows: Frontal scan image: （3） Reverse image: （4） Where Fi and Bi represent the i-th corresponding image point in the forward and reverse scan images, respectively; S4.3, based on the geometric constraint relationship that corresponding image points have the same object direction, the required interior orientation parameters should simultaneously satisfy equations (3) and (4) in step S4.2, then we can obtain... In the formula, , Let be the interior orientation parameter to be solved; S4.4, based on the least squares method to solve the internal orientation parameters of the load, the following linear non-homogeneous equation system is obtained: Right now in, The least squares method can be used to achieve high-precision calculation of the on-orbit orientation parameters of the bidirectional oscillating photoelectric payload: Where N is the number of image points with the same name.

2. The method for on-orbit intrinsic parameter measurement and calibration of oscillating sweep load based on spatial constraints as described in claim 1, characterized in that: In step S1, a bidirectional scanning imaging system mounted on a low-Earth orbit satellite platform is used to obtain a forward scanning image at the bidirectional scanning payload at time t1 and a reverse scanning image at the bidirectional scanning payload at time t2.

3. The method for on-orbit intrinsic parameter measurement and calibration of oscillating sweep load based on spatial constraints as described in claim 1, characterized in that: In step S2, image control points are extracted based on the Harris operator to obtain corresponding image points in the overlapping area of ​​the forward and reverse scan images. Where TPS is the extracted set of images with the same name; and These are the i-th corresponding image points of the forward scan image Fdimg and the reverse scan image Bdimg, respectively.

4. The method for on-orbit intrinsic parameter measurement and calibration of oscillating sweep load based on spatial constraints as described in claim 3, characterized in that: In step S2, the corresponding image point pairs in the overlapping area of ​​the obtained forward and reverse scan images are used to eliminate the influence of mismatches through the RANSAC algorithm.

Images