In-orbit geometric calibration method for line array scanning optical satellite based on equivalent plane array

Abstract

The present application relates to a kind of linear array swing scan type optical satellite on-orbit geometric calibration method based on equivalent surface array, comprising the following steps: step 1, by image matching or artificial measurement method, from high-precision digital orthophoto map and digital elevation model, obtain the ground control point on the single pendulum satellite image;Step 2, according to the geometric relationship between the rotating scanning mirror, motion compensation mirror and linear array CCD in satellite imager and its imaging process, construct linear array swing scan type optical satellite geometric calibration model based on equivalent surface array;Step 3, using ground control point, solve linear array swing scan type optical satellite geometric calibration parameter.The present application can realize linear array swing scan type optical satellite high-precision on-orbit geometric calibration, thereby providing support for linear array swing scan type optical satellite image high-precision geometric processing.

Description

Technical Field

[0001] This invention belongs to the technical field of optical satellite data processing, and in particular relates to an on-orbit geometric calibration method for linear array sweeping optical satellites based on equivalent area arrays. Background Technology

[0002] Linear array sweeping optical imaging satellites typically mount several linear CCD arrays along the orbital direction of the satellite imager's focal plane, and achieve ultra-wide swath imaging of the Earth's surface by means of rotating scanning mirrors and motion compensation mirrors. Compared to linear array pushbroom optical satellites, linear array sweeping satellites can significantly increase the imaging swath width of satellite images while maintaining image spatial resolution.

[0003] To fully leverage the application capabilities of linear array pushbroom optical satellite imagery, the first step is to address the issue of high-precision geometric positioning of satellite imagery. Image positioning accuracy directly determines the geometric quality of satellite image products, including inter-array stitching accuracy and intra-image accuracy. Compared to pushbroom optical satellites, linear array pushbroom optical satellites have more complex physical device structures and imaging geometry processes. High-precision geometric positioning of the imagery requires more comprehensive imaging parameters, primarily including satellite position and attitude, image imaging time, imager installation parameters, imager principal point and principal distance, imager lens distortion, rotating scanning mirror installation and rotation parameters, and motion compensation mirror installation and rotation parameters.

[0004] In-orbit geometric calibration is a common and effective method for accurately acquiring satellite imaging parameters. It can effectively eliminate the impact of satellite imaging parameter errors on image positioning accuracy and has been successfully applied in linear pushbroom optical satellites and area array imaging satellites. However, research on in-orbit geometric calibration for linear pushbroom optical satellites is still relatively limited. How to resolve the strong correlation between imaging parameters of linear pushbroom optical satellites and achieve high-precision in-orbit geometric calibration remains one of the key problems that urgently need to be solved in the high-precision geometric processing of linear pushbroom optical satellite images.

[0005] The inventors' previous patent application CN115164938A disclosed an on-orbit geometric calibration method for linear array sweeping optical remote sensing satellites, including the following steps: Step 1, obtaining ground control points on the linear array sweeping optical remote sensing satellite image from high-precision reference data through image matching or manual measurement; Step 2, constructing an on-orbit geometric calibration model for the linear array sweeping optical satellite based on its imaging geometry; Step 3, using the ground control points and a step-by-step solution strategy to solve for the imaging geometry parameters of the linear array sweeping optical satellite. This invention can achieve accurate solution of the imaging geometry parameters of linear array sweeping optical satellites, thus providing support for high-precision geometric processing of linear array sweeping optical satellite images. However, subsequent research revealed that this invention requires solving for three types of unknown parameters: the satellite camera mounting angle, the initial swing angle and swing angle step size of the swing mirror, and the detector pointing angle of the linear array imaging device. However, these three types of unknown parameters are highly correlated, making the solution process quite complex. To address this deficiency, this invention, based on the physical structure and imaging mechanism of linear array sweeping optical satellite imaging equipment, equates the sweeping imaging of linear array devices to instantaneous imaging of area array devices, and reduces three types of unknown parameters to one type of unknown parameters. This simplifies the calibration process of linear array sweeping optical satellites and significantly reduces the complexity of the calibration process. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an on-orbit geometric calibration method for linear array sweeping optical satellites based on an equivalent area array. Based on the geometric relationships between the rotating scanning mirror, motion compensation mirror, and linear array CCD in the satellite imager, and their imaging process, a geometric calibration model for linear array sweeping optical satellites based on an equivalent area array is constructed. Ground control points are then used to solve for the geometric calibration parameters of the linear array sweeping optical satellites.

[0007] To achieve the above objectives, the technical solution provided by this invention is an on-orbit geometric calibration method for linear array sweeping optical satellites based on equivalent area arrays, comprising the following steps:

[0008] Ground control points on pendulum satellite imagery are obtained from high-precision digital orthophotos and digital elevation models;

[0009] Based on the geometric relationship between the rotating scanning mirror, motion compensation mirror, and linear CCD in the satellite imager and its imaging process, a geometric calibration model for a linear array-based oscillating optical satellite is constructed. This is achieved by equating the rotational motion of the rotating scanning mirror and motion compensation mirror in the satellite imager to the rotational motion of the linear CCD, thus constructing an on-orbit geometric calibration model for a linear array-based oscillating optical satellite. The curved surface formed by the rotation of the equivalent linear CCD is used as the equivalent linear CCD, and based on the on-orbit geometric calibration model based on the equivalent linear array, a geometric calibration model for a linear array-based oscillating optical satellite is constructed.

[0010] Using ground control points, the geometric calibration parameters of a linear array sweeping optical satellite are determined.

[0011] Furthermore, an on-orbit geometric calibration model for a linear array-sweeping optical satellite based on an equivalent linear array is constructed, as shown in equation (1):

[0012]

[0013] In the formula, P g P is the position vector of a ground point in the WGS84 coordinate system. S λ is the position vector of the GNSS antenna phase center in the WGS84 coordinate system; λ is the scaling factor. This is the rotation matrix from the J2000 coordinate system to the WGS84 coordinate system; This is the rotation matrix from the satellite body coordinate system to the J2000 coordinate system; This is the rotation matrix from the imager coordinate system to the satellite body coordinate system; is the rotation matrix from the mirror coordinate system to the imager coordinate system; t is the position vector of the imaging element corresponding to the ground point in the mirror coordinate system.

[0014] Furthermore, a geometric calibration model for a linear array-sweeping optical satellite based on an equivalent surface array is constructed, as shown in equation (2):

[0015]

[0016] In the formula, Let f be the position vector of the equivalent array imaging element corresponding to the ground point in the satellite body coordinate system, where f is the equivalent principal distance of the imager. The pointing angle of the equivalent array imaging element in the satellite body coordinate system is given by equation (3):

[0017]

[0018] In the formula, α=[α0 α1 α2 α3 α4 α5 α6 α7 α8 α9] and β=[β0 β1 β2 β3 β4 β5 β6 β7 β8 β9] are the equivalent matrix orientation parameters, i.e., geometric calibration parameters; H=[1 sl sl s 2 l 2 s 2 l sl 2 s 3 l 3 ] is a vector consisting of pixel coordinates (s, l); the superscript T indicates transpose.

[0019] Furthermore, the method for solving the geometric calibration parameters of a linear array sweeping optical satellite using ground control points is as follows:

[0020] Based on the satellite orbit and attitude parameters during satellite imaging, orbit and attitude models are constructed respectively, and the satellite position and attitude at each ground control point at the corresponding imaging time are obtained by interpolation.

[0021] Transforming equations (2) and (3) into:

[0022]

[0023] In the formula, intermediate parameters intermediate parameter U T =P g -P S ;(F x ,F y () represents the virtual observation value of the control point.

[0024] For each ground control point, an error equation is established according to equation (4);

[0025] Based on the principle of least squares adjustment, the unknowns are solved, thereby obtaining the geometric calibration parameters of the linear array sweeping optical satellite, and realizing high-precision on-orbit geometric calibration processing of the linear array sweeping optical satellite.

[0026] On the other hand, embodiments of the present invention provide an on-orbit geometric calibration system for linear array sweeping optical satellites based on equivalent area arrays, used to implement the on-orbit geometric calibration method for linear array sweeping optical satellites based on equivalent area arrays as described above.

[0027] Moreover, it includes the following modules,

[0028] The first module is used to obtain ground control points on the pendulum satellite image from high-precision digital orthophotos and digital elevation models;

[0029] The second module is used to construct a geometric calibration model of a linear array-based optical satellite based on the geometric relationship between the rotating scanning mirror, motion compensation mirror, and linear CCD in the satellite imager and its imaging process. The implementation method is to equate the rotational motion of the rotating scanning mirror and motion compensation mirror in the satellite imager to the rotational motion of the linear CCD, and construct an on-orbit geometric calibration model of a linear array-based optical satellite based on the equivalent linear array. The curved surface formed by the rotation of the equivalent linear CCD is used as the equivalent linear CCD, and a linear array-based geometric calibration model of an optical satellite based on the equivalent linear array is constructed on the basis of the on-orbit geometric calibration model based on the equivalent linear array.

[0030] The third module is used to solve for the geometric calibration parameters of linear array sweeping optical satellites using ground control points.

[0031] Alternatively, it may include a processor and a memory, the memory being used to store program instructions, and the processor being used to call the stored instructions in the memory to execute an on-orbit geometric calibration method for a linear array-based optical satellite based on an equivalent area array, as described above.

[0032] Alternatively, it may include a readable storage medium storing a computer program that, when executed, implements an on-orbit geometric calibration method for a linear array-based optical satellite based on an equivalent area array, as described above.

[0033] Compared with existing technologies, the present invention has the following advantages: First, the present invention equates the rotational motion of the rotating scanning mirror and motion compensation mirror in the satellite imager to the rotational motion of the linear array CCD, and constructs an on-orbit geometric calibration model of the linear array sweeping optical satellite based on the equivalent linear array; then, the curved surface formed by the rotation of the equivalent linear array CCD is used as the equivalent area array CCD, and based on the on-orbit geometric calibration model based on the equivalent linear array, a geometric calibration model of the linear array sweeping optical satellite based on the equivalent area array is constructed; then, the geometric calibration parameters are solved using ground control points to achieve high-precision on-orbit geometric calibration of the linear array sweeping optical satellite, thereby providing support for accurate geometric processing of linear array sweeping optical satellite images. Attached Figure Description

[0034] Figure 1 This is a flowchart of an embodiment of the present invention.

[0035] Figure 2 This is a schematic diagram of the equivalent linear array and equivalent area array of the present invention. Detailed Implementation

[0036] This invention provides an on-orbit geometric calibration method for a linear array oscillating optical satellite based on an equivalent area array. First, ground control points on the single-pendulum satellite image are obtained from high-precision digital orthophotos and digital elevation models using image matching or manual measurement methods. Second, based on the geometric relationships between the rotating scanning mirror, motion compensation mirror, and linear CCD in the satellite imager and their imaging process, a geometric calibration model for the linear array oscillating optical satellite based on an equivalent area array is constructed. Then, using the ground control points, the geometric calibration parameters of the linear array oscillating optical satellite are solved to achieve high-precision geometric calibration.

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0038] like Figure 1 As shown in the figure, the embodiment of the present invention provides an on-orbit geometric calibration method for linear array sweeping optical satellites based on equivalent area arrays. The implementation process includes the following steps:

[0039] Step 1: Obtain ground control points on the pendulum satellite image from high-precision digital orthophotos and digital elevation models by image matching or manual measurement methods.

[0040] Step 2: Based on the geometric relationship between the rotating scanning mirror, motion compensation mirror and linear CCD in the satellite imager and its imaging process, construct a linear array oscillating optical satellite geometric calibration model based on an equivalent area array.

[0041] Furthermore, the present invention preferably proposes the following implementation method for step 2:

[0042] Step 2.1, as follows Figure 2 As shown, o-xy is the focal plane coordinate system, OX I Y I Z I Let OX be the imager coordinate system. B Y B Z B Using the satellite body coordinate system, the rotational motion of the rotating scanning mirror and motion compensation mirror in the satellite imager is equivalent to the rotational motion of the linear array CCD. A linear array oscillating optical satellite on-orbit geometric calibration model based on the equivalent linear array is constructed, as shown in Equation (1):

[0043]

[0044] In the formula, P g P is the position vector of a ground point in the WGS84 coordinate system. S λ is the position vector of the GNSS antenna phase center in the WGS84 coordinate system; λ is the scaling factor. This is the rotation matrix from the J2000 coordinate system to the WGS84 coordinate system; This is the rotation matrix from the satellite body coordinate system to the J2000 coordinate system; This is the rotation matrix from the imager coordinate system to the satellite body coordinate system; is the rotation matrix from the mirror coordinate system to the imager coordinate system; t is the position vector of the imaging element corresponding to the ground point in the mirror coordinate system;

[0045] Step 2.2, as follows Figure 2 As shown, the curved surface formed by rotating the equivalent linear CCD is used as the equivalent area CCD. Based on the on-orbit geometric calibration model based on the equivalent linear array, a linear array sweeping optical satellite geometric calibration model based on the equivalent area array is constructed, as shown in Equation (2):

[0046]

[0047] In the formula, Let f be the position vector of the equivalent array imaging element corresponding to the ground point in the satellite body coordinate system, where f is the equivalent principal distance of the imager. The pointing angle of the equivalent array imaging element in the satellite body coordinate system is given by equation (3):

[0048]

[0049] In the formula, α=[α0 α1 α2 α3 α4 α5 α6 α7 α8 α9] and β=[β0 β1 β2 β3 β4 β5 β6 β7 β8 β9] are the equivalent matrix orientation parameters, i.e., geometric calibration parameters; H=[1 sl sl s 2 l 2 s 2 l sl 2 s 3 l 3 ] is a vector consisting of pixel coordinates (s, l); the superscript T indicates transpose.

[0050] Step 3: Using ground control points, solve for the geometric calibration parameters of the linear array sweeping optical satellite.

[0051] Step 3.1: Based on the satellite orbit and attitude parameters during satellite imaging, construct orbit and attitude models respectively, and interpolate to obtain the satellite position and attitude at the imaging time corresponding to each ground control point;

[0052] Step 3.2, transform equations (2) and (3) into:

[0053]

[0054] In the formula, intermediate parameters intermediate parameter U T =P g -P S ;(F x ,F y () represents the virtual observation value of the control point.

[0055] Step 3.3: For each ground control point, establish the error equation according to equation (4):

[0056] V = AX - L (5)

[0057] In the formula, The residual matrix of virtual observations for control points; It is a matrix of unknowns; It is a matrix of constant terms; The design matrix is ​​composed of the partial derivatives of the unknowns; where the subscript i represents the i-th ground control point; The residuals of virtual observations at control points; The initial values ​​for the virtual observations of the control points. This indicates the calculation of partial derivatives.

[0058] Step 3.4, solve for the unknown X using the least squares adjustment principle:

[0059] X = (A T A) -1 A T L (6)

[0060] This yields the geometric calibration parameters for the linear array sweeping optical satellite, enabling high-precision on-orbit geometric calibration of the linear array sweeping optical satellite. The on-orbit geometric calibration of the linear array sweeping optical satellite is now complete.

[0061] In specific implementation, the method proposed in the technical solution of this invention can be automatically executed by those skilled in the art using computer software technology. System devices for implementing the method, such as computer-readable storage media storing the corresponding computer program of the technical solution of this invention and computer equipment including the computer program running the corresponding computer program, should also be within the protection scope of this invention.

[0062] In some possible embodiments, an on-orbit geometric calibration system for linear array-based optical satellites using an equivalent area array is provided, comprising the following modules:

[0063] The first module is used to obtain ground control points on the pendulum satellite image from high-precision digital orthophotos and digital elevation models;

[0064] The second module is used to construct a geometric calibration model of a linear array-based optical satellite based on the geometric relationship between the rotating scanning mirror, motion compensation mirror, and linear CCD in the satellite imager and its imaging process. The implementation method is to equate the rotational motion of the rotating scanning mirror and motion compensation mirror in the satellite imager to the rotational motion of the linear CCD, and construct an on-orbit geometric calibration model of a linear array-based optical satellite based on the equivalent linear array. The curved surface formed by the rotation of the equivalent linear CCD is used as the equivalent linear CCD, and a linear array-based geometric calibration model of an optical satellite based on the equivalent linear array is constructed on the basis of the on-orbit geometric calibration model based on the equivalent linear array.

[0065] The third module is used to solve for the geometric calibration parameters of linear array sweeping optical satellites using ground control points.

[0066] In some possible embodiments, an on-orbit geometric calibration system for a linear array-based optical satellite using an equivalent area array is provided, including a processor and a memory. The memory is used to store program instructions, and the processor is used to call the stored instructions in the memory to execute the on-orbit geometric calibration method for a linear array-based optical satellite using an equivalent area array as described above.

[0067] In some possible embodiments, an on-orbit geometric calibration system for a linear array-based optical satellite using an equivalent area array is provided, comprising a readable storage medium storing a computer program. When the computer program is executed, it implements the on-orbit geometric calibration method for a linear array-based optical satellite using an equivalent area array as described above.

[0068] In practice, the above process can be automated using computer software technology. The specific embodiments described herein are merely illustrative examples of the spirit of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for on-orbit geometric calibration of linear array-based glide sweep optical satellites based on equivalent area arrays, characterized in that, Includes the following steps: Ground control points on pendulum satellite imagery are obtained from high-precision digital orthophotos and digital elevation models; Based on the geometric relationship between the rotating scanning mirror, motion compensation mirror, and linear CCD in the satellite imager and its imaging process, a geometric calibration model for a linear array-based oscillating optical satellite is constructed. This is achieved by equating the rotational motion of the rotating scanning mirror and motion compensation mirror in the satellite imager to the rotational motion of the linear CCD, thus constructing an on-orbit geometric calibration model for a linear array-based oscillating optical satellite. The curved surface formed by the rotation of the equivalent linear CCD is used as the equivalent linear CCD, and based on the on-orbit geometric calibration model based on the equivalent linear array, a geometric calibration model for a linear array-based oscillating optical satellite is constructed. Using ground control points, the geometric calibration parameters of a linear array sweeping optical satellite are determined.

2. The on-orbit geometric calibration method for a linear array-based swept optical satellite based on an equivalent area array as described in claim 1, characterized in that: An on-orbit geometric calibration model for a linear array-sweeping optical satellite based on an equivalent linear array is constructed, as shown in Equation (1): In the formula, P g P is the position vector of a ground point in the WGS84 coordinate system. S λ is the position vector of the GNSS antenna phase center in the WGS84 coordinate system; λ is the scaling factor. This is the rotation matrix from the J2000 coordinate system to the WGS84 coordinate system; This is the rotation matrix from the satellite body coordinate system to the J2000 coordinate system; This is the rotation matrix from the imager coordinate system to the satellite body coordinate system; is the rotation matrix from the mirror coordinate system to the imager coordinate system; t is the position vector of the imaging element corresponding to the ground point in the mirror coordinate system.

3. The on-orbit geometric calibration method for a linear array-based, swept-array optical satellite as described in claim 2, characterized in that: A geometric calibration model for a linear array-sweeping optical satellite based on an equivalent surface array is constructed, as shown in equation (2): In the formula, Let f be the position vector of the equivalent array imaging element corresponding to the ground point in the satellite body coordinate system, where f is the equivalent principal distance of the imager. The pointing angle of the equivalent array imaging element in the satellite body coordinate system is given by equation (3): In the formula, α=[α0 α1 α2 α3 α4 α5 α6 α7 α8 α9] and β=[β0 β1 β2 β3 β4 β5 β6 β7 β8 β9] are the equivalent matrix orientation parameters, i.e., geometric calibration parameters; H=[1 sl sl s 2 l 2 s 2 l sl 2 s 3 l 3 ] is a vector consisting of pixel coordinates (s, l); the superscript T indicates transpose.

4. The on-orbit geometric calibration method for a linear array-based swept optical satellite based on an equivalent area array as described in claim 3, characterized in that: The method for solving the geometric calibration parameters of a linear array sweeping optical satellite using ground control points is as follows: Based on the satellite orbit and attitude parameters during satellite imaging, orbit and attitude models are constructed respectively, and the satellite position and attitude at each ground control point at the corresponding imaging time are obtained by interpolation. Transforming equations (2) and (3) into: In the formula, intermediate parameters intermediate parameter U T =P g -P S ;(F x F y () represents the virtual observation value of the control point; For each ground control point, an error equation is established according to equation (4); Based on the principle of least squares adjustment, the unknowns are solved, thereby obtaining the geometric calibration parameters of the linear array sweeping optical satellite, and realizing high-precision on-orbit geometric calibration processing of the linear array sweeping optical satellite.

5. An on-orbit geometric calibration system for linear array-based optical satellites using an equivalent area array, characterized in that: This method is used to implement the on-orbit geometric calibration method for linear array sweeping optical satellites based on an equivalent area array, as described in any one of claims 1-4.

6. The on-orbit geometric calibration system for linear array-based optical satellites using an equivalent area array as described in claim 5, characterized in that: Includes the following modules, The first module is used to obtain ground control points on the pendulum satellite image from high-precision digital orthophotos and digital elevation models; The second module is used to construct a geometric calibration model of a linear array-based optical satellite based on the geometric relationship between the rotating scanning mirror, motion compensation mirror, and linear CCD in the satellite imager and its imaging process. The implementation method is to equate the rotational motion of the rotating scanning mirror and motion compensation mirror in the satellite imager to the rotational motion of the linear CCD, and construct an on-orbit geometric calibration model of a linear array-based optical satellite based on the equivalent linear array. The curved surface formed by the rotation of the equivalent linear CCD is used as the equivalent linear CCD, and a linear array-based geometric calibration model of an optical satellite based on the equivalent linear array is constructed on the basis of the on-orbit geometric calibration model based on the equivalent linear array. The third module is used to solve for the geometric calibration parameters of linear array sweeping optical satellites using ground control points.

7. The on-orbit geometric calibration system for linear array-based optical satellites using an equivalent area array as described in claim 5, characterized in that: It includes a processor and a memory, the memory being used to store program instructions, and the processor being used to call the stored instructions in the memory to execute the on-orbit geometric calibration method for a linear array sweeping optical satellite based on an equivalent area array as described in any one of claims 1-4.

8. The on-orbit geometric calibration system for linear array-based optical satellites using an equivalent area array as described in claim 5, characterized in that: It includes a readable storage medium on which a computer program is stored, and when the computer program is executed, it implements the on-orbit geometric calibration method for a linear array sweeping optical satellite based on an equivalent area array as described in any one of claims 1-4.

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