Method and system for resolving trajectory of target participating in measurement outside camera

Abstract

The invention discloses a method and system for resolving a trajectory of a target participating in measurement outside a camera, and the method comprises the steps: dividing a plurality of measurement segments in the motion course of the target according to the simulation motion data of the target, and setting a plurality of collinear control points; erecting a plurality of cameras for relay shooting of target motion images; establishing an object space coordinate system in the motion space of the target, and respectively establishing an image space coordinate system by taking the projection center of each camera as a reference point; obtaining object space coordinates of each camera and each control point and image space coordinates of each control point; calculating external parameters of each camera; calculating an object space coordinate calculation formula of the target point and verifying the accuracy; according to an accurate object space coordinate calculation formula of the target point, calculating trajectory data of target motion in the measurement section; and integrating the trajectory data of the target motion in each measurement section. The method can simplify the operation process, reduce the implementation cost and improve the measurement precision during the calculation of the camera external parameters of the high-speed moving target and the measurement of the target trajectory.

Description

Technical Field

[0001] The present invention relates to the technical field of photogrammetry, and in particular to a method and system for calculating the trajectory of a target measured outside a camera. Background Art

[0002] Photogrammetry is widely used in target position measurement, 3D model reconstruction, engineering survey and design, quality control, motion recovery, and other fields. To obtain 3D spatial information about a target, photogrammetry generally requires two or more cameras to intersect and capture the target's 3D position and pose. When performing photogrammetry, the camera's external parameters must be determined.

[0003] Measuring the motion of high-speed targets within a large test field requires measuring the target's trajectory over a range of tens to hundreds of meters, far exceeding the target's altitude of tens to tens of meters. Under these field test conditions, measuring the high-speed camera's external parameters and the target's trajectory data becomes a complex and challenging task.

[0004] Among traditional camera parameter calibration methods, the most common one is the resection-based calibration method. This method obtains the intrinsic and extrinsic parameters of a high-speed camera by setting multiple non-collinear and non-coplanar control points within the test area and solving a set of collinear equations. However, this calibration method is generally only suitable for test scenarios with a small measurement range. Due to the large test range of high-speed target motion and the requirement for good visibility throughout the test area, it is impossible to set up a large number of large, high-altitude physical control points within the test site. In this case, the resection method, which requires a large number of control points and the simultaneous solution of intrinsic and extrinsic parameters, is not suitable.

[0005] Currently, there are two main methods for measuring the external parameters of high-speed cameras. One method involves adding a tracking turntable to the camera to measure the azimuth and pitch angles in real time as the camera rotates, ensuring that the roll angle is zero. This method is relatively simple, but requires the addition of a high-precision tracking turntable, which is relatively expensive and can significantly increase the cost of the test. The other method involves setting up a movable target frame in front of the camera, with a large number of control points located on different planes. The target frame is generally larger, with a minimum length of more than 2 meters on a single side. Compared to the previous method, this method is more cumbersome and requires the design, fabrication, transportation, and setup of a large target frame, which is time-consuming and labor-intensive. Summary of the Invention

[0006] The main purpose of the present invention is to provide a method and system for calculating the trajectory of a target in a camera-less measurement, thereby simplifying the operation process, reducing the implementation cost and improving the measurement accuracy.

[0007] The technical solution adopted by the present invention is: a method for calculating the trajectory of a target measured by an external camera, wherein, based on the simulated motion data of the target, a plurality of measurement segments are divided along the target's motion course and a plurality of collinear control points are set, so that each measurement segment contains at least three control points and adjacent measurement segments contain at least one identical control point; a plurality of cameras are set up on one side of the target's motion course to take relay pictures of the target's motion, so that each camera completely captures at least one measurement segment and each control point is captured by two cameras at the intersection; Establish an object-space coordinate system in the target's motion space, and establish an image-space coordinate system using the projection center of each camera as a reference point. Obtain the object-space coordinates of each camera and each control point, as well as the image-space coordinates of each control point. Select two control points within each measurement segment and calculate the extrinsic parameters of the camera capturing that measurement segment. Take the target point at the same moment in the target motion trajectory of each measurement segment, and solve the object coordinate calculation formula of the target point based on the external parameters of the camera that intersects and photographs the target point; In each measurement segment, control points that are not involved in solving the camera's external parameters are selected to verify the accuracy of the object space coordinate calculation formula of the target point in each measurement segment; if accurate, the trajectory data of the target motion in the measurement segment is solved according to the object space coordinate calculation formula of the target point; otherwise, the control points are reselected to solve the external parameters of the camera shooting the measurement segment until they are accurate; and the trajectory data of the target motion in each measurement segment are integrated.

[0008] According to the above technical solution, the external parameters of the camera include the camera's external azimuth elements and the camera's lens focal length.

[0009] According to the above technical solution, the method of dividing the target's motion direction into multiple measurement segments based on its simulated motion data and setting multiple collinear control points includes: Determine the expected lens focal length of each camera based on the maximum simulated height of the target movement; Calculating the shooting range of each camera in the target movement direction according to the estimated lens focal length of each camera; According to the maximum simulated heading distance of the target movement and the shooting range of each camera in the target movement heading, the measurement segment is divided in the target movement heading and multiple collinear control points are set.

[0010] According to the above technical solution, the object space coordinate system includes an object space coordinate system D-XYZ; the object space coordinate system D-XYZ takes the starting point of the target movement as the origin, the target movement heading as the positive direction of the X axis, the vertical target movement heading upward as the positive direction of the Y axis, and the positive direction of the Z axis is determined by the right-hand rule; The image space coordinate system includes an image plane coordinate system o-xy, an image space coordinate system S-xyz and an image space auxiliary coordinate system S-UVW; the image plane coordinate system o-xy takes the center of the image plane captured by each camera as its origin, the horizontal axis of the image plane as its x-axis, and the vertical axis of the image plane as its y-axis; the image space coordinate system S-xyz takes the projection center of each camera as its origin, and its x-axis and y-axis are parallel to the x-axis and y-axis of the image plane coordinate system respectively; the image space auxiliary coordinate system S-UVW takes the projection center of each camera as its origin, and its U axis, V axis and W axis are parallel to the X axis, Y axis and Z axis of the object space coordinate system D-XYZ respectively.

[0011] According to the above technical solution, the method of selecting two control points in each measurement segment and calculating the external parameters of the camera shooting the measurement segment specifically includes: According to the object space coordinates of the camera and the two selected control points and the image plane coordinates of the two selected control points, a collinear equation group of the two control points is established; Representing the error equation of the collinear equations with a matrix and solving it to obtain correction values ​​for the camera extrinsic parameters; The correction number is iteratively calculated until it converges to an optimal solution, and the optimal solution is the external parameters of the camera that captures the measurement segment.

[0012] According to the above technical solution, the method for solving the object space coordinate calculation formula of the target point in each measurement segment specifically includes: In each measurement section, for the two cameras that intersect and photograph the target point, obtain the relationship between their image space coordinate system S-xyz and the image space auxiliary coordinate system S-UVW, as well as the relationship between the image space auxiliary coordinate system S-UVW and the object space coordinate system D-XYZ. Combine these two relationships to obtain the standard equations for X and Z of the two cameras that intersect and photograph the target point. Establishing a set of equations for intersection calculation based on the image plane coordinates of the target point and the standard equations of the two cameras that intersect and photograph the target point; the image plane coordinates of the target point are taken from the image plane coordinate system o-xy of the two cameras that intersect and photograph the target point; The object space coordinate calculation formula of the target point is solved according to the equation group for intersection calculation and the external parameters of the two cameras that intersect and photograph the target point.

[0013] According to the above technical solution, the method for verifying the accuracy of the object space coordinate calculation formula of the target point in each measurement segment specifically includes: Substitute the image plane coordinates of the control point that does not participate in solving the camera external parameters into the object space coordinate calculation formula of the target point in the measurement segment to obtain the object space coordinate calculation value of the control point; The calculated value is compared with the object space coordinates of the control point; if the error is lower than the preset value, the object space coordinate calculation formula of the target point of the measurement segment is judged to be accurate; otherwise, the object space coordinate calculation formula of the target point of the measurement segment is judged to be inaccurate.

[0014] According to the above technical solution, if the object space coordinate calculation formula of the target point of the measurement segment is inaccurate, and after reselecting the control points to solve the external parameters of the camera shooting the measurement segment, the object space coordinate calculation formula of the target point of the measurement segment is still inaccurate, then it is checked whether the object space coordinates and image plane coordinates of the control points in the measurement segment are accurate.

[0015] Another aspect of the present invention provides a system for calculating the trajectory of a target measured with external camera participation, which executes the above-mentioned method for calculating the trajectory of a target measured with external camera participation.

[0016] Another aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program implements the steps of executing the above method when executed by a processor.

[0017] The beneficial effects of the present invention are as follows: The present invention provides a method and system for calculating camera extrinsic parameters for measuring target trajectory. Multiple collinear control points and multiple cameras are set along the target's motion direction for relaying the target's motion image. Based on the object space coordinates of each camera and each control point and the image plane coordinates of each control point, the extrinsic parameters of each camera are calculated. Ultimately, through intersection calculations performed on the target points using the extrinsic parameters of each camera, the motion trajectory data of the target in each measurement segment is obtained and integrated. Compared with the prior art, the present invention requires simpler field setup and testing equipment for camera extrinsic parameter calculation and target trajectory measurement, and a simpler method flow.

[0018] Furthermore, when solving the camera's external parameters, the present invention uses two control points to solve the camera's external parameters, and uses control points that are not involved in the solution to verify the accuracy, while improving the convenience of control point setting and the reliability of the solution process.

[0019] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1is a flow chart of a method for calculating the trajectory of a target measured outside a camera according to an embodiment of the present invention; Figure 2 is a structural diagram of a system for calculating target trajectory measured outside the camera according to an embodiment of the present invention; Figure 3 Schematic diagram of various coordinate systems established in the method for calculating the trajectory of a target measured outside a camera according to an embodiment of the present invention; Figure 4 is a schematic diagram of cameras and control points in a system for calculating the trajectory of a target measured outside the camera according to an embodiment of the present invention; Figure 5 This is a schematic diagram of another arrangement of cameras and control points in a system for solving the measurement of target trajectory outside the camera according to an embodiment of the present invention; Figure 6 is an Xt curve diagram of the target motion trajectory of an embodiment of the present invention; Figure 7 2 is a Yt and Zt curve diagram of the target motion trajectory according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] It should be noted that the illustrations provided in the embodiments of the present invention are only schematic illustrations of the basic concept of the present invention. Therefore, the drawings only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0024] In the present invention, it should also be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like are used to indicate positions or locations based on those shown in the accompanying drawings. These terms are intended solely to facilitate the description of the present application and to simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present application. Furthermore, the terms "first" and "second" are used solely for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0025] Example 1 This embodiment provides a method for calculating the external parameters of the camera's target trajectory, which is used to test the high-speed target trajectory with large heading displacement, high target height, and small lateral distance, as well as the external parameters of the camera that records the motion trajectory. Figure 1 As shown, the steps include: S1. Based on the simulated motion data of the target, multiple measurement segments are divided in its motion direction and multiple collinear control points are set, and multiple cameras are set up in the motion space of the target.

[0026] S101 : Determine an estimated lens focal length f0 of a single camera according to a maximum simulated height H of target motion.

[0027] S102 : Calculate the shooting range D of the single camera in the target movement direction according to the estimated lens focal length f0 of the single camera.

[0028] S103 , dividing the target movement direction into measurement segments and setting a plurality of collinear control points according to the maximum simulated heading distance L of the target movement and the shooting range D of a single camera in the target movement direction.

[0029] Specifically, the number of divided measurement segments is n, where n=L / D.

[0030] The number of collinear control points set in the target motion direction is N, where N=2n+1.

[0031] The specific setting method of multiple cameras is to set up multiple cameras for relay shooting on one side of the heading of the target movement, in an area that is basically parallel to the heading and convenient for testing.

[0032] Generally, the camera in this embodiment is a high-speed camera.

[0033] The specific method for setting control points is to ensure that each measurement segment contains at least three control points, adjacent measurement segments contain at least one common control point, each camera captures at least one measurement segment, and each control point is captured by two cameras at the intersection. In this embodiment, for ease of implementation, the number of control points set in each measurement segment is three, and adjacent measurement segments contain one common control point.

[0034] Based on the above layout principles, this embodiment can achieve that all measurement segments are fully captured by at least one camera. Preferably, for ease of implementation, the crosshairs of the camera image plane are aligned with the control points in the middle of the image plane, and the images of all control points are set at the bottom of the image plane.

[0035] S2. Establish an object-space coordinate system in the target's motion space and an image-space coordinate system using the projection center of each camera as a reference point. Obtain the object-space coordinates of each camera and each control point, as well as the image-space coordinates of each control point. Select two control points within each measurement segment to calculate the extrinsic parameters of the camera capturing that measurement segment.

[0036] Specifically, if Figure 3 As shown, the object coordinate system includes the object space coordinate system D-XYZ; the object space coordinate system D-XYZ takes the starting point of the target movement as the origin, the target movement heading is the positive direction of the X axis, the vertical target movement heading upward is the positive direction of the Y axis, and the positive direction of the Z axis is determined by the right-hand rule.

[0037] The image space coordinate system includes an image plane coordinate system o-xy, an image space coordinate system S-xyz and an image space auxiliary coordinate system S-UVW; the image plane coordinate system o-xy takes the center of the image plane captured by each camera as its origin, the horizontal axis of the image plane as its x-axis, and the vertical axis of the image plane as its y-axis; the image space coordinate system S-xyz takes the projection center of each camera as its origin, and its x-axis and y-axis are parallel to the x-axis and y-axis of the image plane coordinate system respectively; the image space auxiliary coordinate system S-UVW takes the projection center of each camera as its origin, and its U axis, V axis and W axis are parallel to the X axis, Y axis and Z axis of the object space coordinate system D-XYZ respectively.

[0038] Specifically, the external parameters of the camera include the camera's exterior azimuth angle elements α, β, and γ and the camera's lens focal length f.

[0039] Specifically, the object space coordinates of each camera and each control point are obtained by measuring with a total station measuring instrument. The object space coordinates of each camera are defined as (X S 、Y S , Z S ), the object space coordinates of each control point are (X I 、Y I , Z I ), where the subscript S represents the measurement site and I=1,2,…,n,…2n+1.

[0040] Select two control points within the measurement segment captured by each camera, and calculate the camera's extrinsic parameters based on their object space coordinates and image plane coordinates. Prioritize the control points at both ends of the image plane for calculating the camera's extrinsic parameters.

[0041] According to the object space coordinates of the camera and the two selected control points and the image plane coordinates of the two selected control points, the collinear equations of the two control points are established. The collinear equations are as follows:

[0042] in, ai 、b i 、c i (i=1,2,3) are the elements of the rotation matrix R, which is obtained by rotating the coordinate system S-xyz to the coordinate system S-UVW three times.

[0043] The calculation formula of the rotation matrix R is as follows:

[0044] Among them, R α 、 R β 、R γ They represent the rotation matrices formed by rotating the image space coordinate system S-xyz to the auxiliary space coordinate system S-UVW by rotating γ around the z-axis, β around the y-axis, and α around the x-axis.

[0045] The error equations of the collinear equations are represented by matrices and solved to obtain correction values ​​for the camera's external parameters.

[0046] The error equation is as follows:

[0047] Based on the collinearity condition equations used in photogrammetry, one control point can be used to establish two equations, and two control points can be used to establish four equations. Using two control points in the measurement segment, we can solve for four unknown parameters and achieve spatial positioning of the high-speed camera. Given the object space coordinates (X1, Y1, Z1) and (X2, Y2, Z2) of the two control points and the image point coordinates (x1, y1) and (x2, y2), we can solve for the four unknowns α, β, γ, and f for the camera in the measurement segment.

[0048] The expressions of each matrix in the error equation are as follows:

[0049] Solving the error equation yields:

[0050] X t That is, the correction values ​​Δα, Δβ, Δγ, and Δf of the camera external parameters α, β, γ, and f.

[0051] The corrections are iteratively calculated until convergence to the optimal solution, which becomes the camera's extrinsic parameters. Assuming the initial values ​​of Δα, Δβ, Δγ, and Δf are α0, β0, γ0, and f0, respectively, the camera's extrinsic parameters α, β, γ, and f are derived using the following formula.

[0052]

[0053] S3. Take the target point at the same moment in the target motion trajectory of each measurement segment, and solve the object coordinate calculation formula of the target point based on the external parameters of the camera that intersects and photographs the target point.

[0054] S301. Within each measurement segment, for the two cameras that intersect and photograph the target point, obtain the relationship between their image space coordinate system S-xyz and the image space auxiliary coordinate system S-UVW, as well as the relationship between the image space auxiliary coordinate system S-UVW and the object space coordinate system D-XYZ. Combine these two relationships to obtain the standard equations for X and Z of the two cameras that intersect and photograph the target point.

[0055] Among them, the relationship between the image space coordinate system S-xyz and the image space auxiliary coordinate system S-UVW is:

[0056] The relationship between the image space auxiliary coordinate system S-UVW and the object space coordinate system D-XYZ is:

[0057] Where λ is the scaling factor.

[0058] Combining the two relations, we get:

[0059] Convert the above equation into the standard equation about X and Z:

[0060] The standard form equations for X and Z are further transformed into:

[0061] S302: Establish a set of equations for intersection calculation based on the image plane coordinates of the target point and the standard equations of the two cameras that intersect and capture the target point. The image plane coordinates of the target point are two sets, each taken from the image plane coordinate system o-xy of the two cameras that intersect and capture the target point.

[0062] The image plane coordinates of each intersection point in the two adjacent measurement segments to which it belongs are (x1, y1) and (x2, y2), respectively. Using the standard equations for X and Z obtained in step S301, the following intersection equations are established:

[0063] The coefficients k with subscripts l and r represent the correlation coefficients obtained from the left and right high-speed camera images, respectively.

[0064] S303 , solving a calculation formula for the object space coordinates of the target point according to the equation group for intersection calculation and the external parameters of the two cameras that intersect and photograph the target point.

[0065] By using the elimination method, the intersection equations obtained in step S302 are solved to obtain the spatial coordinates (X, Y, Z) of the target point as follows:

[0066] S4. In each measurement segment, select control points that are not involved in calculating the camera's extrinsic parameters to verify the accuracy of the object-space coordinate calculation formula for the target point in each measurement segment. If accurate, calculate the target's motion trajectory data within that measurement segment using the object-space coordinate calculation formula. Otherwise, reselect control points and calculate the extrinsic parameters of the camera capturing that measurement segment until accuracy is achieved. Integrate the target's motion trajectory data within each measurement segment.

[0067] Specifically, the method for verifying the accuracy of the object space coordinate calculation formula of the target point in each measurement segment includes: Substitute the image plane coordinates of the control point that does not participate in solving the camera external parameters into the object space coordinate calculation formula of the target point in the measurement segment to obtain the calculated object space coordinate value of the control point.

[0068] The calculated object space coordinates of the control points are compared with the object space coordinates obtained through actual measurement, and the displacement between the two is taken as the error.

[0069] Specifically, if the error is less than a preset value, the calculated value differs slightly from the object-space coordinates of the control point, proving that the object-space coordinate calculation formula for the target point can accurately obtain the object-space coordinates using the image plane coordinates of the control point. The object-space coordinate calculation formula for the target point in this measurement segment is accurate. Otherwise, the object-space coordinates obtained using the image plane coordinates of the control point differ significantly from the calculated value, and the object-space coordinate calculation formula for the target point in this measurement segment is inaccurate. In this embodiment, the preset value is 0.1 m.

[0070] Furthermore, if the error is still greater than or equal to the preset value of 0.1 m after reselecting the control points to solve the external parameters of the camera shooting the measurement segment, then the object space coordinates and image plane coordinates of the control points in the measurement segment are checked for accuracy.

[0071] This embodiment also provides a system based on the above-mentioned method for solving the trajectory of the target involved in the measurement outside the camera, including multiple cameras, multiple collinear control points, a moving target, a measuring device and a solving device, the structure of which is as follows: Figure 2 shown.

[0072] Among them, multiple control points are arranged on the heading of the moving target, and multiple cameras are set up on one side of the heading, in an area basically parallel to the heading and convenient for testing, according to the layout rules of intersection shooting and each camera completely shooting a measurement section.

[0073] Figure 4 and Figure 5 A layout method of camera and control points is shown respectively.

[0074] As attached Figure 4 In the layout shown, each measurement section is captured by two cameras, and the number of cameras required is 2n. Figure 5 In the arrangement shown, n cameras for relay shooting are set up in the direction of target motion, which is the same number as the number of measurement segments n. In addition, one camera is set up for intersection shooting. This arrangement requires fewer high-speed cameras, namely (n+1).

[0075] Multiple cameras are connected to the solving device, and the captured target motion images are transmitted to the solving device as imaging data.

[0076] The measuring device is used to measure the position information of multiple collinear control points and multiple cameras.

[0077] The solving device is used to solve the external parameters of the camera and the motion trajectory data of the target based on the imaging data and the position information of the control points and the camera.

[0078] This embodiment also provides a computer-readable storage medium, such as a flash memory, a hard disk, a multimedia card, a card-type memory (e.g., SD or DX memory), a random access memory (RAM), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a programmable read-only memory (PROM), a magnetic storage device, a disk, an optical disk, a server, an app store, etc., storing a computer program that, when executed by a processor, implements corresponding functions. When executed by a processor, the computer-readable storage medium of this embodiment implements the aforementioned method for calculating the trajectory of a target in off-camera participatory measurement.

[0079] Example 2 This embodiment provides a specific application of the method for calculating the target trajectory by external camera participation in measurement described in Embodiment 1. In a high-speed rocket sled test, the trajectory of an experimental target ejected from a rocket sled is measured.

[0080] In this embodiment, multiple cameras are set up on the ground at a vertical distance of about 200m from the straight track, and the setting of the control points can be achieved by setting white foam above the track.

[0081] The method for calculating the target trajectory by external camera participation in the measurement of the target trajectory described in Example 1 was used to conduct the trajectory test of the 1000km / h high-speed rocket sled test target. The Xt curve, Yt curve, and Zt curve are shown as follows: Figure 6 and Figure 7 As shown in the figure, the starting point of the experimental target movement is the origin, the experimental target movement direction is the positive direction of the X axis, the vertical experimental target movement direction is the positive direction of the Y axis, and the positive direction of the Z axis is determined according to the right-hand rule.

[0082] The test results show that the maximum heading displacement of the experimental target reached 336m, the maximum height was 26m, and the maximum lateral displacement was 10m. This demonstrates that the method for calculating target trajectory using camera-assisted external measurement, as described in Example 1, achieves wide-range trajectory measurement of high-speed targets through a simple field setup, test equipment, and measurement method.

[0083] In summary, the present invention provides a method and system for calculating the trajectory of a target in off-camera measurement, which can simplify the operation process, reduce implementation costs, and improve measurement accuracy.

[0084] It should be pointed out that, according to the needs of implementation, the various steps / components described in this application can be split into more steps / components, or two or more steps / components or partial operations of steps / components can be combined into new steps / components to achieve the purpose of the present invention.

[0085] The size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0086] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for calculating the trajectory of a target measured by external camera, characterized in that: include: Based on the simulated motion data of the target, the target's motion direction is divided into multiple measurement segments and multiple collinear control points are set, ensuring that each measurement segment contains at least three control points and adjacent measurement segments contain at least one common control point. Multiple cameras are set up on one side of the target's motion direction to capture the target's motion trajectory in relays, ensuring that each camera completely captures at least one measurement segment and that each control point is captured by two cameras at the intersection. Establish an object-space coordinate system in the target's motion space, and establish an image-space coordinate system using the projection center of each camera as a reference point. Obtain the object-space coordinates of each camera and each control point, as well as the image-space coordinates of each control point. Select two control points within each measurement segment and calculate the extrinsic parameters of the camera capturing each measurement segment. Take the target point at the same moment in the target motion trajectory of each measurement segment, and solve the object coordinate calculation formula of the target point based on the external parameters of the camera that intersects and photographs the target point; In each measurement segment, a control point that is not involved in solving the camera's external parameters is selected to verify the accuracy of the object space coordinate calculation formula of the target point in each measurement segment. If it is accurate, the trajectory data of the target movement in the measurement segment is solved according to the object space coordinate calculation formula of the target point. Otherwise, reselect the control points to solve the external parameters of the camera shooting the measurement segment until they are accurate; integrate the trajectory data of the target movement in each measurement segment.

2. The method for calculating the target trajectory of the camera external measurement according to claim 1, characterized in that: The external parameters of the camera include the camera's exterior azimuth elements and the camera's lens focal length.

3. The method for calculating the target trajectory of the camera external measurement according to claim 1, characterized in that: The method of dividing the target's motion direction into multiple measurement segments based on its simulated motion data and setting multiple collinear control points includes: Determine the expected lens focal length of each camera based on the maximum simulated height of the target movement; Calculating the shooting range of each camera in the target movement direction according to the estimated lens focal length of each camera; According to the maximum simulated heading distance of the target movement and the shooting range of each camera in the target movement heading, the measurement segment is divided in the target movement heading and multiple collinear control points are set.

4. The method for calculating the target trajectory of the camera external measurement according to claim 1, characterized in that: The object coordinate system includes an object space coordinate system D-XYZ; the object space coordinate system D-XYZ takes the starting point of the target movement as the origin, the target movement heading as the positive direction of the X axis, the vertical target movement heading upward as the positive direction of the Y axis, and the positive direction of the Z axis is determined by the right-hand rule; The image space coordinate system includes an image plane coordinate system o-xy, an image space coordinate system S-xyz and an image space auxiliary coordinate system S-UVW; the image plane coordinate system o-xy takes the center of the image plane captured by each camera as its origin, the horizontal axis of the image plane as its x-axis, and the vertical axis of the image plane as its y-axis; the image space coordinate system S-xyz takes the projection center of each camera as its origin, and its x-axis and y-axis are parallel to the x-axis and y-axis of the image plane coordinate system respectively; the image space auxiliary coordinate system S-UVW takes the projection center of each camera as its origin, and its U axis, V axis and W axis are parallel to the X axis, Y axis and Z axis of the object space coordinate system D-XYZ respectively.

5. The method for calculating the target trajectory of the camera external participation measurement according to claim 4, characterized in that: The method of selecting two control points in each measurement segment and calculating the external parameters of the camera shooting the measurement segment specifically includes: According to the object space coordinates of the camera and the two selected control points and the image plane coordinates of the two selected control points, a collinear equation group of the two control points is established; Representing the error equation of the collinear equations with a matrix and solving it to obtain correction values ​​for the camera extrinsic parameters; The correction number is iteratively calculated until it converges to an optimal solution, and the optimal solution is the external parameters of the camera that captures the measurement segment.

6. The method for calculating the target trajectory of the camera external measurement according to claim 4, characterized in that: The method for solving the object space coordinate calculation formula of the target point in each measurement segment specifically includes: In each measurement section, for the two cameras that intersect and photograph the target point, obtain the relationship between their image space coordinate system S-xyz and the image space auxiliary coordinate system S-UVW, as well as the relationship between the image space auxiliary coordinate system S-UVW and the object space coordinate system D-XYZ. Combine these two relationships to obtain the standard equations for X and Z of the two cameras that intersect and photograph the target point. Establishing a set of equations for intersection calculation based on the image plane coordinates of the target point and the standard equations of the two cameras that intersect and photograph the target point; the image plane coordinates of the target point are taken from the image plane coordinate system o-xy of the two cameras that intersect and photograph the target point; The object space coordinate calculation formula of the target point is solved according to the equation group for intersection calculation and the external parameters of the two cameras that intersect and photograph the target point.

7. The method for calculating the target trajectory of the camera external participation measurement according to claim 1, characterized in that: The methods for verifying the accuracy of the object space coordinate calculation formula of the target point in each measurement segment include: Substitute the image plane coordinates of the control point that does not participate in solving the camera external parameters into the object space coordinate calculation formula of the target point in the measurement segment to obtain the object space coordinate calculation value of the control point; The calculated value is compared with the object space coordinates of the control point; if the error is lower than the preset value, the object space coordinate calculation formula of the target point of the measurement segment is judged to be accurate; otherwise, the object space coordinate calculation formula of the target point of the measurement segment is judged to be inaccurate.

8. The method for calculating the target trajectory of the camera external participation measurement according to claim 1, characterized in that: If the object space coordinate calculation formula of the target point of the measurement segment is inaccurate, and the object space coordinate calculation formula of the target point of the measurement segment is still inaccurate after reselecting the control points to solve the external parameters of the camera shooting the measurement segment, then check whether the object space coordinates and image plane coordinates of the control points in the measurement segment are accurate.

9. A system for calculating the trajectory of a target measured outside the camera, characterized in that: The system executes the method for calculating the trajectory of a target measured outside the camera as described in any one of claims 1 to 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for solving the trajectory of a target measured outside the camera are implemented.

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