A line array swing-scan type optical satellite image geometric correction method and system

Abstract

The present application relates to a kind of line array swing sweep type optical satellite image geometric correction method and system, including according to the imaging geometric mechanism of line array swing sweep type optical satellite, construct the geometric correction model of line array swing sweep type optical satellite image;According to satellite image geometric correction model, using satellite image imaging time parameter, satellite attitude parameter, satellite orbit parameter, satellite camera parameter and digital elevation model, calculate and obtain the longitude and latitude corresponding to each image point on satellite image;Based on the spatial resolution of geometric correction image, the maximum and minimum of the longitude and latitude corresponding to four corner points of satellite image are calculated, the longitude and latitude of the starting point of the upper left of geometric correction image and the width and height of image are determined;According to the gray value and longitude and latitude of image point on satellite image and the starting point longitude and latitude and spatial resolution of geometric correction image, the gray value of each image point on geometric correction image is calculated, and the geometric correction processing of line array swing sweep type optical satellite image is completed.

Description

Technical Field

[0001] This invention belongs to the technical field of optical remote sensing satellite data processing, and in particular relates to a method and system for geometric correction of linear array oscillating optical satellite images. Background Technology

[0002] Linear array scanning optical remote sensing satellites typically mount several linear array imaging devices along a track on the imaging plane of the satellite camera, acquiring ultra-wide-swath optical satellite images by vertically scanning the track. For example, the Atmospheric-1 satellite's wide-swath imager has a spatial resolution of 75 to 600 meters and an imaging swath width of up to 2300 kilometers; the Gaofen-5A satellite's wide-swath thermal infrared imager has a spatial resolution of 100 meters and an imaging swath width of 1500 kilometers. Thanks to their ultra-wide-swath imaging capabilities, linear array scanning imaging satellites are attracting increasing attention from countries and institutions.

[0003] Compared to the ultra-wide swath imaging capability in the vertical orbit direction, the ground coverage area along the orbit direction of linear array sweeping satellites is often smaller. For example, the swath width of a single sweeping image from the Atmospheric-1 satellite's wide-swath imager is only 9 kilometers along the orbit direction, far smaller than the 2300-kilometer swath width in the vertical orbit direction. To obtain satellite image products with ultra-wide swath widths in both the vertical and horizontal orbit directions, geometric correction and geometric stitching of multiple single sweeping images are often required. However, compared to linear array pushbroom satellites, the imaging process of linear array sweeping satellites is more complex, typically requiring rotating scanning mirrors and scanning compensation mirrors to achieve ultra-wide sweeping imaging. Ground target light rays need to be reflected multiple times by the rotating scanning mirrors and scanning compensation mirrors before being imaged on the camera's focal plane, which makes the geometric correction of linear array sweeping satellite images even more complex.

[0004] Traditional satellite image geometric correction methods face two main challenges due to the complex imaging process and ultra-wide imaging swath of linear scan satellites. First, general rational function models struggle to accurately describe the imaging geometry of linear scan satellites. Second, geometric correction methods based on rigorous imaging models suffer from complex projection transformations from ground points to image points. Achieving accurate geometric correction for linear scan satellite images remains a critical issue that urgently needs to be addressed in high-precision geometric processing of these images. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a geometric correction scheme for linear array scanning optical satellite images. Based on the imaging mechanism of linear array scanning satellites, a geometric correction model for satellite images is constructed, and the latitude and longitude of each pixel in the image are calculated. Then, by interpolating four neighboring pixels, the grayscale value of each pixel in the geometrically corrected image is obtained, thereby achieving accurate geometric correction of linear array scanning optical satellite images.

[0006] To achieve the above objectives, the present invention provides a linear array oscillating optical satellite image geometric correction method, comprising the following steps:

[0007] Step 1: Based on the imaging geometry mechanism of linear array sweeping optical satellites, construct a geometric correction model for linear array sweeping optical satellite images;

[0008] Step 2: Based on the satellite image geometric correction model, using the satellite image imaging time parameters, satellite attitude parameters, satellite orbit parameters, satellite camera parameters, and digital elevation model, calculate the latitude and longitude corresponding to each pixel on the satellite image;

[0009] Step 3: Use the spatial resolution of the satellite image's nadir point or the manually specified spatial resolution as the spatial resolution of the geometrically corrected image, and calculate the maximum and minimum values ​​of the latitude and longitude corresponding to the four corner points of the satellite image to determine the latitude and longitude of the upper left starting point of the geometrically corrected image, as well as the width and height of the image.

[0010] Step 4: Based on the grayscale value and latitude and longitude of the image points on the satellite image, as well as the latitude and longitude of the starting point and spatial resolution of the geometrically corrected image, calculate the grayscale value of each image point on the geometrically corrected image to complete the geometric correction processing of the linear array sweeping optical satellite image.

[0011] Step 4.1: For a certain image point A on the satellite image, take the image point A and its right neighboring image point B, right lower neighboring image point C, and lower neighboring image point D as a group of four neighboring image points {A, B, C, D};

[0012] Step 4.2: Construct quadrilateral ABCD based on the latitude and longitude of the four neighboring image points from Step 4.1;

[0013] Step 4.3: Calculate the maximum and minimum values ​​of the latitude and longitude of the four neighboring image points in Step 4.1, and construct quadrilateral abcd;

[0014] Step 4.4: Based on the geographical range of quadrilateral abcd, the latitude and longitude of the starting point of the geometrically corrected image, and the spatial resolution, calculate the image points that fall within quadrilateral abcd on the geometrically corrected image.

[0015] Step 4.5: For each image point that falls within quadrilateral ABCD in Step 4.4, determine whether the image point falls within quadrilateral ABCD. If yes, interpolate the gray value of the image point based on the gray values ​​of its four neighboring image points in Step 4.1; otherwise, continue to determine the next image point.

[0016] Step 4.6: Traverse every pixel on the satellite image and repeat steps 4.1 to 4.5.

[0017] Moreover, the geometric correction model for linear array oscillating optical satellite images constructed in step 1 is shown in equation (1):

[0018]

[0019] In the formula, (X,Y,Z) are the spatial rectangular coordinates of the ground point in the WGS84 coordinate system; (X S ,Y S Z S ) represents the spatial rectangular coordinates 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 orbit coordinate system to the J2000 coordinate system; This is the rotation matrix from the satellite body coordinate system to the satellite orbit coordinate system; This is the rotation matrix from the camera coordinate system to the satellite body coordinate system; This is the rotation matrix from the mirror coordinate system to the camera coordinate system; This represents the pointing angle of the imaging element corresponding to the ground point.

[0020] Moreover, the calculation of image point latitude and longitude in step 2 uses multi-core parallel computing based on OpenMP.

[0021] Moreover, steps 4.1 to 4.5 in step 4 employ multi-core parallel computing based on OpenMP.

[0022] Furthermore, in step 4.5, quadrilateral ABCD can be divided into two triangles, ABC and ACD, and then it can be determined whether a certain image point falls within triangle ABC or ACD. If the image point falls within triangle ABC or ACD, then the image point is considered to fall within quadrilateral ABCD.

[0023] Furthermore, in step 4.5, for a certain image point that falls within quadrilateral ABCD, the gray value of the image point is obtained by using the reciprocal of the spatial distance between the image point and its four neighboring image points as the weight, and by employing a weighted average interpolation method.

[0024] This completes the geometric correction of linear array sweeping optical satellite images.

[0025] Compared with the prior art, the present invention has the following advantages: The present invention constructs a geometric correction model for satellite images based on the imaging mechanism of linear array sweeping satellites, calculates the latitude and longitude of each pixel in the image, and then obtains the gray value of each pixel in the geometrically corrected image by interpolating four neighboring pixels, thereby realizing accurate geometric correction of linear array sweeping optical satellite images, thus providing technical support for the production of high-precision image products of linear array sweeping optical satellites. Attached Figure Description

[0026] Figure 1 This is a flowchart of an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the four-neighbor image point interpolation of the present invention. Detailed Implementation

[0028] This invention provides a method for geometric correction of linear array sweeping optical satellite images. First, a geometric correction model for the satellite image is constructed based on the imaging mechanism of linear array sweeping satellites. Second, the latitude and longitude corresponding to each image point on the satellite image are calculated using an image point coordinate projection transformation method. Then, based on the set spatial resolution and the coverage area of ​​the satellite image, the latitude and longitude of the upper left starting point of the geometrically corrected image, as well as the width and height of the image, are set. Finally, the grayscale value of each image point on the geometrically corrected image is obtained through four-neighbor interpolation, thereby achieving accurate geometric correction of the linear array sweeping optical satellite image.

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] like Figure 1 As shown, the linear array oscillating optical satellite image geometric correction method of this invention includes the following steps:

[0031] Step 1: Based on the imaging geometry mechanism of linear array sweeping optical satellites, construct a geometric correction model for linear array sweeping optical satellite images, as shown below:

[0032]

[0033] In the formula, (X,Y,Z) are the spatial rectangular coordinates of the ground point in the WGS84 coordinate system; (X S ,Y S Z S ) represents the spatial rectangular coordinates 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 orbit coordinate system to the J2000 coordinate system; This is the rotation matrix from the satellite body coordinate system to the satellite orbit coordinate system; This is the rotation matrix from the camera coordinate system to the satellite body coordinate system; This is the rotation matrix from the mirror coordinate system to the camera coordinate system; This represents the pointing angle of the imaging element corresponding to the ground point.

[0034] Step 2: Based on the satellite image geometric correction model, using the satellite image imaging time parameters, satellite attitude parameters, satellite orbit parameters, satellite camera parameters, and digital elevation model, a multi-core parallel computing method based on OpenMP is adopted to calculate the latitude and longitude corresponding to each pixel on the satellite image.

[0035] The specific methods for calculating latitude and longitude can be implemented using existing technologies, which will not be elaborated upon in this invention. A preferred approach is to employ a multi-core parallel computing method based on OpenMP to improve efficiency.

[0036] Step 3: Use the spatial resolution of the satellite image's nadir point or the manually specified spatial resolution as the spatial resolution of the geometrically corrected image, and calculate the maximum and minimum values ​​of the latitude and longitude corresponding to the four corner points of the satellite image to determine the latitude and longitude of the upper left starting point of the geometrically corrected image, as well as the width and height of the image.

[0037] The calculation methods for the specific maximum and minimum values ​​of latitude and longitude can be implemented using existing technologies, and will not be elaborated upon in this invention.

[0038] Step 4: Based on the grayscale value and latitude and longitude of the image points on the satellite image, as well as the latitude and longitude of the starting point and spatial resolution of the geometrically corrected image, the grayscale value of each image point on the geometrically corrected image is calculated by interpolating four neighboring image points one by one, thus completing the geometric correction processing of the linear array sweeping optical satellite image.

[0039] In the embodiment, a further preferred method for obtaining the grayscale value of each pixel in the geometrically corrected image is as follows:

[0040] Step 4.1, as follows Figure 2 As shown, for a certain image point A on a satellite image, the image point A and its right neighboring image point B, right lower neighboring image point C, and lower neighboring image point D are taken as a group of four neighboring image points {A, B, C, D};

[0041] Step 4.2: Construct quadrilateral ABCD based on the latitude and longitude of the four neighboring image points from Step 4.1;

[0042] Step 4.3: Calculate the maximum and minimum values ​​of the latitude and longitude of the four neighboring image points in Step 4.1, and construct quadrilateral abcd;

[0043] In practice, we can set the maximum and minimum longitude values ​​of the four neighboring image points to be Lmax and Lmin, and the maximum and minimum latitude values ​​to be Bmax and Bmin, respectively. Then, let the longitude and latitude coordinates of points a, b, c, and d be (Lmin, Bmax), (Lmax, Bmax), (Lmax, Bmin), and (Lmin, Bmin), respectively. The four points a, b, c, and d can form a quadrilateral abcd.

[0044] Step 4.4: Based on the geographical range of quadrilateral abcd, the latitude and longitude of the starting point of the geometrically corrected image, and the spatial resolution, calculate the image points that fall within quadrilateral abcd on the geometrically corrected image.

[0045] Step 4.5: For each image point that falls within quadrilateral ABCD in Step 4.4, determine whether the image point falls within quadrilateral ABCD. If yes, interpolate the gray value of the image point based on the gray values ​​of its four neighboring image points in Step 4.1; otherwise, continue to determine the next image point.

[0046] In practical implementation, it is preferred to divide quadrilateral ABCD into two triangles, ABC and ACD, and then determine whether a certain image point falls within triangle ABC or ACD. If the image point falls within triangle ABC or ACD, it is considered to fall within quadrilateral ABCD. For an image point falling within quadrilateral ABCD, the gray value of the image point is obtained by weighted average interpolation, using the reciprocal of the spatial distance between the image point and its four neighboring image points as the weight, as shown in the following formula:

[0047]

[0048] In the formula, G A G B G C and G D G represents the gray values ​​of points A, B, C, and D, respectively; G is the gray value of an image point falling within quadrilateral ABCD; and W... A W B W C and W D These are the reciprocals of the spatial distances between the image point and points A, B, C, and D, respectively.

[0049] Step 4.6, in specific implementation, can be carried out by using a multi-core parallel computing method based on OpenMP to traverse every pixel on the satellite image and repeat steps 4.1 to 4.5.

[0050] In practice, if the computer has N cores and the satellite image has M pixels, the M pixels can be divided into [M / N]+1 pixel groups. Then, using the OpenMP-based multi-core parallel computing method, the N pixels in each pixel group are assigned to a computer core, and steps 4.1 to 4.5 are repeated until the calculation of all pixel groups is completed.

[0051] This completes the geometric correction of linear array sweeping optical satellite images.

[0052] 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.

[0053] In some possible embodiments, a linear array oscillating optical satellite image geometric correction system is provided, comprising the following modules:

[0054] The first module is used to construct a geometric correction model for linear array scanning optical satellite images based on the imaging geometry mechanism of linear array scanning optical satellites.

[0055] The second module is used to calculate the latitude and longitude corresponding to each pixel on the satellite image based on the satellite image geometric correction model, using satellite image imaging time parameters, satellite attitude parameters, satellite orbit parameters, satellite camera parameters and digital elevation model;

[0056] The third module is used to calculate the maximum and minimum latitude and longitude values ​​corresponding to the four corner points of the satellite image based on the spatial resolution of the geometrically corrected image, and to determine the latitude and longitude of the upper left starting point of the geometrically corrected image, as well as the width and height of the image.

[0057] The fourth module is used to calculate the gray value of each pixel in the geometrically corrected image based on the gray value and latitude and longitude of the pixel in the satellite image, as well as the latitude and longitude of the starting point and spatial resolution of the geometrically corrected image, thus completing the geometric correction processing of the linear array sweeping optical satellite image.

[0058] In specific implementation, the implementation of each module can refer to the relevant steps above, and will not be elaborated upon in this invention.

[0059] In some possible embodiments, a linear array scanning optical satellite image geometric correction system 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 a linear array scanning optical satellite image geometric correction method as described above.

[0060] In some possible embodiments, a linear array oscillating optical satellite image geometric correction system is provided, including a readable storage medium on which a computer program is stored. When the computer program is executed, it implements a linear array oscillating optical satellite image geometric correction method as described above.

[0061] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A line array swing scan type optical satellite image geometric correction method, characterized by, Comprising the following steps: Step 1, according to the imaging geometry mechanism of linear array swing scan optical satellite, a geometric correction model of linear array swing scan optical satellite image is constructed; Step 2, according to the satellite image geometric correction model, using satellite image imaging time parameters, satellite attitude parameters, satellite orbit parameters, satellite camera parameters and digital elevation model, the corresponding latitude and longitude of each image point on the satellite image is calculated; Step 3, based on the spatial resolution of the geometric correction image, the maximum and minimum values of the latitude and longitude corresponding to the four corner points of the satellite image are calculated, and the latitude and longitude of the starting point of the upper left corner of the geometric correction image and the width and height of the image are determined; Step 4, according to the gray value and latitude and longitude of the image point on the satellite image and the starting point latitude and longitude and spatial resolution of the geometric correction image, the gray value of each image point on the geometric correction image is calculated, the geometric correction processing of the linear array swing scan optical satellite image is completed, and the implementation includes the following substeps, Step 4.1, for a certain image point A on the satellite image, the image point and its right adjacent image point B, right lower adjacent image point C and lower adjacent image point D are taken as a set of four adjacent image points {A, B, C, D}; Step 4.2, according to the latitude and longitude of the four adjacent image points in step 4.1, a quadrilateral ABCD is constructed; Step 4.3, the maximum and minimum values of the latitude and longitude of the four adjacent image points in step 4.1 are calculated, and a quadrilateral abcd is constructed; Step 4.4, according to the geographical range of the quadrilateral abcd, the starting point latitude and longitude and spatial resolution of the geometric correction image, the image points falling into the quadrilateral abcd on the geometric correction image are calculated; Step 4.5, for each image point falling into the quadrilateral abcd in step 4.4, it is judged whether the image point falls into the quadrilateral ABCD, if yes, the gray value of the image point is interpolated according to the gray value of the four adjacent image points in step 4.1; if not, the next image point is judged; Step 4.6, each image point on the satellite image is traversed, and steps 4.1 to 4.5 are repeated.

2. A method for geometric correction of linear array pushbroom satellite images as claimed in claim 1, wherein, In step 1, the geometric correction model of linear array swing scan optical satellite image is constructed as follows, wherein, is the spatial rectangular coordinate of the ground point in the WGS84 coordinate system; is the spatial rectangular coordinate of the GNSS antenna phase center in the WGS84 coordinate system; is the scale factor; is the rotation matrix from the J2000 coordinate system to the WGS84 coordinate system; is the rotation matrix from the satellite orbit coordinate system to the J2000 coordinate system; is the rotation matrix from the satellite body coordinate system to the satellite orbit coordinate system; is the rotation matrix from the camera coordinate system to the satellite body coordinate system; is the rotation matrix from the mirror coordinate system to the camera coordinate system; is the pointing angle of the ground point to the corresponding imaging element.

3. A method for geometric correction of linear array pushbroom satellite images as claimed in claim 1, wherein, In step 2, the calculation of the latitude and longitude of the image point uses multi-core parallel computing based on OpenMP.

4. A method for geometric correction of linear array pushbroom satellite images as claimed in claim 1, wherein, In step 4, steps 4.1 to 4.5 use multi-core parallel computing based on OpenMP.

5. A method for geometric correction of linear array pushbroom satellite images as claimed in claim 1, wherein, In step 4.5, the quadrilateral ABCD is divided into two triangles ABC and ACD, and it is judged whether a certain image point falls into triangle ABC or ACD, if the image point falls into triangle ABC or ACD, it is considered that the image point falls into the quadrilateral ABCD.

6. A method for geometric correction of linear array pushbroom satellite images as claimed in claim 1, wherein, In step 4.5, for a certain image point falling into the quadrilateral ABCD, the reciprocal of the spatial distance between the image point and the four adjacent image points is taken as the weight, and the gray value of the image point is obtained by using the weighted average interpolation method.

7. A linear array pushbroom optical satellite image geometric correction system characterized by: A linear array swing scan optical satellite image geometric correction method for realizing any one of claims 1-6.

8. The line array sweeping optical satellite image geometric correction system according to claim 7, characterized in that: Comprising the following modules, The first module is used for constructing a geometric correction model of linear array swing scan optical satellite image according to the imaging geometry mechanism of linear array swing scan optical satellite; The second module is configured to calculate the longitude and latitude corresponding to each pixel on the satellite image according to a satellite image geometric correction model, satellite image imaging time parameters, satellite attitude parameters, satellite orbit parameters, satellite camera parameters, and a digital elevation model; The third module is configured to calculate the maximum and minimum values of the longitude and latitude corresponding to the four corner points of the satellite image based on the spatial resolution of the geometric correction image, and determine the longitude and latitude of the starting point of the upper left corner of the geometric correction image and the width and height of the image. The fourth module is configured to calculate the gray value of each pixel on the geometric correction image according to the gray value and longitude and latitude of the pixel on the satellite image, and the longitude and latitude and spatial resolution of the starting point of the geometric correction image, and complete the geometric correction processing of the line array swing scanning optical satellite image.

9. An electronic device, comprising: The memory is configured to store program instructions, and the processor is configured to call the stored instructions in the memory to execute the line array swing scanning optical satellite image geometric correction method according to any one of claims 1-6.

10. A readable storage medium, characterized by: The readable storage medium stores a computer program, and the computer program is configured to execute the line array swing scanning optical satellite image geometric correction method according to any one of claims 1-6.

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