A multispectral image per-pixel observation geometry reconstruction method and device

Abstract

The application discloses a multispectral image per-pixel observation geometry reconstruction method and device. The method comprises the following steps: acquiring the corner point coordinates of four corner points of a scene corresponding to satellite images, the outer frame lines corresponding to the four corner points, and a first straight line parallel to a first outer frame line in the outer frame lines; acquiring the plane coordinates of a target point of the scene, the intersection of the line connecting the satellite position and the earth center with the ground, the first intersection point of the scene center point along the orbit direction straight line and the first straight line, and the second intersection point of the satellite position and the orbit direction straight line; and performing observation geometry reconstruction on the satellite images according to the straight line equation corresponding to the first straight line, the intersection points, the side frame line equation corresponding to the outer frame line, the first intersection point, the second intersection point and the satellite orbit height. The application can improve the observation geometry precision of per-pixel images.

Description

Technical Field

[0001] This invention relates to the field of remote sensing satellite data processing technology, and in particular to a method and apparatus for geometric reconstruction of multispectral images pixel by pixel. Background Technology

[0002] Currently, all domestically produced land observation satellites except for one geostationary satellite use scanning payloads for their multispectral payloads. Generally, wide-swath multispectral payloads such as HJ1A / B-CCD, GF6-WFV, and CB04A-WFI provide observation geometry information covering the entire scene. Other payloads with relatively narrow swaths only provide the imaging geometry of the scene center, lacking the imaging geometry of other pixels. Many applications require the observation geometry of other pixels. For example, in absolute radiometric calibration, the calibration field does not coincide with the scene center, necessitating the determination of its observation geometry; quantitative inversion requires pixel-by-pixel observation geometry. Users often use the scene center observation geometry to replace the observation geometry of other pixels in the panoramic image. When the image swath is small, the changes in calibration and quantification caused by the observation geometry are negligible. However, as the swath width increases, the changes caused by the observation geometry become significant. Reconstructing the observation geometry of all pixels in the image based on existing conditions becomes a key point for further improving calibration and quantification accuracy.

[0003] The remote sensing image metadata distributed to external parties lacks the precise orbital parameters for the satellite imaging time, making it impossible to calculate the observation geometry for each pixel based on a rigorous physical model. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a method and apparatus for geometric reconstruction of multispectral images pixel by pixel.

[0005] The technical solution of this invention is:

[0006] In a first aspect, embodiments of the present invention provide a pixel-by-pixel observation geometric reconstruction method for multispectral images, including:

[0007] Obtain the corner coordinates of the four corner points of the scene corresponding to the satellite image, the outer border lines corresponding to the four corner points, and the first straight line parallel to the first outer border line among the outer border lines;

[0008] Obtain the planar coordinates of the target point corresponding to the scene, the intersection of the line connecting the satellite position and the Earth's center with the ground, the first intersection of the straight line along the orbital direction of the scene's center point and the first straight line, and the second intersection of the satellite position and the straight line along the orbital direction; the straight line connecting the satellite position and the second intersection point is perpendicular to the straight line along the orbital direction.

[0009] Based on the equation of the line corresponding to the first line, the intersection point, the equation of the boundary frame corresponding to the outer frame, the first intersection point, the second intersection point, and the satellite orbital altitude, the observation geometry of the satellite image is reconstructed.

[0010] Optionally, the step of performing observational geometry reconstruction on the satellite image based on the equation of the line corresponding to the first straight line, the equation of the boundary frame corresponding to the outer frame, the first intersection point, the second intersection point, and the satellite orbital altitude includes:

[0011] Based on the equation of the straight line, the equation of the boundary frame, and the satellite orbital altitude, obtain the first distance between the intersection point and the first intersection point, the second distance between the intersection point and the second intersection point, and the third distance between the first intersection point and the second intersection point;

[0012] Based on the first distance, the second distance, and the third distance, the observation geometry is reconstructed for the observation field of view, observation zenith angle, and observation azimuth angle of the satellite image.

[0013] Optionally, the step of performing observation geometry reconstruction on the observation field of view, observation zenith angle, and observation azimuth angle of the satellite image based on the first distance, the second distance, and the third distance includes:

[0014] Based on the third distance, the coordinates of the intersection point of the second intersection point are calculated;

[0015] Based on the coordinates of the intersection point and the formula for the distance between two points, the fourth distance between the projection point of the satellite and the imaging point corresponding to the satellite image, the fifth distance between the satellite position and the intersection point, and the central angle between the imaging point and the satellite position are calculated.

[0016] The observation field of view of the satellite image is calculated based on the fourth distance and the fifth distance.

[0017] The observation zenith angle of the satellite image is calculated based on the fourth distance, the fifth distance, and the central angle.

[0018] The observation azimuth angle of the satellite image is calculated based on the second distance and the fourth distance.

[0019] Optionally, calculating the observation azimuth angle of the satellite image based on the second distance and the fourth distance includes:

[0020] Based on the second distance and the fourth distance, the first azimuth angle with the first intersection point as the coordinate center is calculated;

[0021] Obtain the second azimuth angle with the imaging point as the coordinate center;

[0022] Obtain the azimuth difference between the first azimuth and the second azimuth;

[0023] The observation azimuth angle of the satellite image is calculated based on the first azimuth angle and the difference between the azimuth angles.

[0024] Secondly, embodiments of the present invention provide a multispectral image pixel-by-pixel observation geometric reconstruction apparatus, comprising:

[0025] The first straight line acquisition module is used to acquire the corner coordinates of the four corner points of the scene corresponding to the satellite image, the outer border line corresponding to the four corner points, and the first straight line parallel to the first outer border line among the outer border lines.

[0026] The intersection point acquisition module is used to acquire the planar coordinates of the target point corresponding to the scene, the intersection of the line connecting the satellite position and the center of the Earth with the ground, the first intersection point of the straight line along the orbit direction of the scene's center point and the first straight line, and the second intersection point of the satellite position and the straight line along the orbit direction; the straight line connecting the satellite position and the second intersection point is perpendicular to the straight line along the orbit direction.

[0027] The observation geometry reconstruction module is used to perform observation geometry reconstruction on the satellite image based on the equation of the line corresponding to the first line, the intersection point, the equation of the boundary frame corresponding to the outer frame, the first intersection point, the second intersection point, and the satellite orbital altitude.

[0028] Optionally, the observation geometry reconstruction module includes:

[0029] The distance acquisition unit is used to acquire, based on the straight line equation, the boundary frame equation, and the satellite orbital altitude, a first distance between the intersection point and the first intersection point, a second distance between the intersection point and the second intersection point, and a third distance between the first intersection point and the second intersection point;

[0030] The observation geometry reconstruction unit is used to perform observation geometry reconstruction on the observation field of view, observation zenith angle and observation azimuth angle of the satellite image based on the first distance, the second distance and the third distance.

[0031] Optionally, the observation geometry reconstruction unit includes:

[0032] The intersection point coordinate calculation subunit is used to calculate the intersection point coordinates of the second intersection point based on the third distance.

[0033] The central angle calculation subunit is used to calculate the fourth distance between the projection point of the satellite and the imaging point corresponding to the satellite image, the fifth distance between the satellite position and the intersection point, and the central angle between the imaging point and the satellite position based on the coordinates of the intersection point and the two-point distance formula.

[0034] The observation field of view calculation subunit is used to calculate the observation field of view of the satellite image based on the fourth distance and the fifth distance;

[0035] The observation zenith angle calculation subunit is used to calculate the observation zenith angle of the satellite image based on the fourth distance, the fifth distance, and the central angle.

[0036] The observation azimuth calculation subunit is used to calculate the observation azimuth of the satellite image based on the second distance and the fourth distance.

[0037] Optionally, the observation azimuth calculation subunit includes:

[0038] The first azimuth calculation subunit is used to calculate the first azimuth angle with the first intersection point as the coordinate center based on the second distance and the fourth distance.

[0039] The second azimuth angle calculation subunit is used to obtain the second azimuth angle with the imaging point as the coordinate center;

[0040] Azimuth difference acquisition subunit is used to acquire the azimuth difference between the first azimuth and the second azimuth;

[0041] The observation azimuth angle acquisition subunit is used to calculate the observation azimuth angle of the satellite image based on the first azimuth angle and the difference between the azimuth angles.

[0042] The advantages of this invention compared to the prior art are:

[0043] Based on the basic parameters of the satellite, such as satellite orbital altitude, scene center observation zenith angle, azimuth angle, etc., this invention performs pixel-by-pixel observation geometry reconstruction of satellite images. Compared with the scene center observation method to replace the scene-by-pixel method, this scheme can greatly improve the observation geometry accuracy of images pixel by pixel, thereby affecting calibration and quantitative applications. Attached Figure Description

[0044] Figure 1 A flowchart illustrating the steps of a pixel-by-pixel observation geometric reconstruction method for multispectral images provided in this embodiment of the invention;

[0045] Figure 2 A schematic diagram of a projection of an equivalent sphere of the Earth provided in an embodiment of the present invention;

[0046] Figure 3 A schematic diagram of four directions provided for an embodiment of the present invention;

[0047] Figure 4 A schematic diagram illustrating the principle of satellite observation zenith angle correction provided in an embodiment of the present invention;

[0048] Figure 5 This is a schematic diagram of a multispectral image pixel-by-pixel observation geometric reconstruction device provided in an embodiment of the present invention. Detailed Implementation

[0049] Example 1

[0050] Reference Figure 1 The flowchart illustrates the steps of a pixel-by-pixel observation geometric reconstruction method for multispectral images provided by an embodiment of the present invention, as follows: Figure 1 As shown, the pixel-by-pixel observation geometric reconstruction method for multispectral images may include the following steps:

[0051] Step 101: Obtain the corner coordinates of the four corner points of the scene corresponding to the satellite image, the outer border lines corresponding to the four corner points, and the first straight line parallel to the first outer border line among the outer border lines.

[0052] In this embodiment, when performing observational geometric reconstruction on satellite images, the corner coordinates of the four corner points of the scene corresponding to the satellite image, the outer border lines corresponding to the four corner points, and the first straight line parallel to the first outer border line in the outer border lines can be obtained.

[0053] After obtaining the corner coordinates of the four corner points of the scene corresponding to the satellite image, the outer border lines corresponding to the four corner points, and the first straight line parallel to the first outer border line, step 102 is executed.

[0054] Step 102: Obtain the planar coordinates of the target point corresponding to the scene, the intersection of the line connecting the satellite position and the Earth's center with the ground, the first intersection of the straight line along the orbital direction of the scene's center point and the first straight line, and the second intersection of the satellite position and the straight line along the orbital direction; the straight line connecting the satellite position and the second intersection point is perpendicular to the straight line along the orbital direction.

[0055] After obtaining the above parameters, the plane coordinates of the target point corresponding to the scene, the intersection of the line connecting the satellite position and the Earth's sphere with the ground, the first intersection of the straight line along the orbit direction of the scene's center point and the first straight line, the second intersection of the satellite position and the straight line along the orbit direction, wherein the straight line connecting the satellite position and the second intersection point is perpendicular to the straight line along the orbit direction.

[0056] Step 103: Perform observation geometry reconstruction on the satellite image based on the equation of the line corresponding to the first line, the intersection point, the equation of the boundary frame corresponding to the outer frame, the first intersection point, the second intersection point, and the satellite orbital altitude.

[0057] After obtaining the equations of the lines, intersection points, outer bounding frames, first intersection point, and second intersection point, observational geometry reconstruction of the satellite imagery can be performed based on the equations of the lines corresponding to the first line, intersection points, outer bounding frames, first intersection point, second intersection point, and satellite orbital altitude. Specifically, based on the equations of the lines, the bounding frame equations, and the satellite orbital altitude, the first distance between the intersection point and the first intersection point, the second distance between the intersection point and the second intersection point, and the third distance between the first intersection point and the second intersection point can be obtained. Then, based on the first, second, and third distances, observational geometry reconstruction of the observation field of view, observation zenith angle, and observation azimuth angle of the satellite imagery can be performed.

[0058] This process can be described in detail in conjunction with the following specific implementation methods.

[0059] In one specific implementation of the present invention, the method for observational geometric reconstruction may include the following steps:

[0060] Step S1: Calculate the coordinates of the intersection point of the second intersection point based on the third distance.

[0061] In this embodiment, after obtaining the third distance, the coordinates of the intersection point of the second intersection point can be calculated based on the third distance.

[0062] After calculating the coordinates of the second intersection point, proceed to step S2.

[0063] Step S2: Based on the coordinates of the intersection point and the two-point distance formula, calculate the fourth distance between the projection point of the satellite and the imaging point corresponding to the satellite image, the fifth distance between the satellite position and the intersection point, and the central angle between the imaging point and the satellite position.

[0064] After calculating the coordinates of the second intersection point, the fourth distance between the satellite's head image and the corresponding imaging point in the satellite image, the fifth distance between the satellite position and the intersection point, and the central angle between the imaging point and the satellite position can be calculated based on the intersection point coordinates and the two-point distance formula.

[0065] Step S3: Calculate the observation field of view of the satellite image based on the fourth distance and the fifth distance.

[0066] After calculating the fourth and fifth distances, the observation field of view of the satellite image can be calculated based on the fourth and fifth distances.

[0067] Step S4: Calculate the observation zenith angle of the satellite image based on the fourth distance, the fifth distance, and the central angle.

[0068] After obtaining the fourth distance, the fifth distance, and the central angle, the observation zenith angle of the satellite image can be calculated based on the fourth distance, the fifth distance, and the central angle.

[0069] Step S5: Calculate the observation azimuth angle of the satellite image based on the second distance and the fourth distance.

[0070] After obtaining the second and fourth distances, the observation azimuth of the satellite image can be calculated based on these distances. Specifically, the first azimuth, centered at the first intersection point, can be calculated using the second and fourth distances, and the second azimuth, centered at the imaging point, can be obtained. After obtaining the first and second azimuths, the azimuth difference between them can be calculated, and then the observation azimuth of the satellite image can be calculated based on the first azimuth and the azimuth difference.

[0071] The specific implementation process of the technical solution of this invention can be combined with... Figures 2-4 The following formula will be described in detail.

[0072] The observation zenith angle of a pixel refers to the angle between the line connecting the satellite sensor and the pixel and the normal to the pixel's ground plane. For example... Figure 2 As shown in the diagram, the circle represents the projection of the Earth's equivalent sphere, point V is the satellite's position, V1 is the intersection of the line connecting the satellite and the Earth's center on the ground (i.e., the satellite's projection point on the ground), point S is the imaging point, and O is the Earth's center. Therefore, ∠z is the observation zenith angle at point S, ∠o is the central angle between point S and the satellite, and ∠z1 is the field of view angle observed by the satellite at point S. From trigonometric relationships, we can know that:

[0073] ∠z=∠o+∠z1 (1)

[0074] Set the satellite orbital altitude to L vv1 The Earth's radius is r e Then we have:

[0075] sin(z)*r e =sin(z1)*(r e +L vv1 (2)

[0076] The observation azimuth of a pixel is calculated by starting from true north and rotating clockwise to the ray projected onto the Earth's surface from the line connecting the satellite and the pixel at a certain moment. The vertex of this ray is the pixel point on the Earth's surface, and the angle of rotation is the azimuth of the pixel. For example... Figure 3As shown in the diagram: LonE / LonW / LatS / LatN represent the four cardinal directions (north, south, east, and west), and V / V1 / S / O represent the four cardinal directions (north, south, east, and west). Figure 2 Similarly, V / S's projections onto the plane are V2 / S1, so the observation azimuth of point S is the angle from due north, clockwise to ray S1V2, which is a.

[0077] set up Figure 4 In the image, ABDE represent the four corner points of the scene: upper left, upper right, lower left, and lower right, respectively. Connecting AB, AD, EB, and ED forms the outer border of the image. Let the line passing through AB be l0, and the line passing through AD be l2. S is the target point, FG is the line l1 parallel to l0 and passing through point S, C is the intersection of the scene center point with the line l3 along the track direction and FG, and the line passing through point C in the north-south direction is HI. V is the satellite's location, V1 is the satellite's projection point on the Earth's surface, and O1 is the intersection of the perpendicular line from satellite V to FG and FG. Connect VO1, VC, and VS.

[0078] The following convention is made: the planar coordinates of each point in the diagram are represented by subscripts, such as the planar coordinates x of point S. s y s And so on.

[0079] The latitude and longitude of each point ABCDE can be obtained from the imagery. The latitude and longitude of the target point are known. The length L of line segment VV1 is... vv1 This represents the satellite's orbital altitude.

[0080] The field of view at the center of the satellite image is z2 = ∠V1VC. The zenith angle and azimuth angle of the center of the image can be obtained from the image's metadata, and z2 can then be calculated.

[0081] Let z1, z, a be the observation field of view, the observation zenith angle, and the observation azimuth angle at point S.

[0082] The key to correcting the zenith angle lies in obtaining the central angle, which essentially involves obtaining the length of the great circle arc between points S and V1. The coordinates of point S are known, while those of point V1 are unknown. This can be calculated using the observation geometry information from the center of the scene.

[0083] The correction methods for the observation zenith angle and observation field of view may include the following steps:

[0084] 1. Transform the spherical latitude and longitude coordinates to kilometer grid coordinates. The original coordinate coefficients of the projection are in the WGS84 coordinate system, and the target coordinate system is in the UTM projected coordinate system. The zone number can be determined according to the latitude and longitude of the target point. Then the plane coordinates of all known points in the map can be obtained.

[0085] 2. Lines l1 and l0 are parallel, meaning they have the same slope. Line l1 can be represented by y = kx + b. Substituting the coordinates of points A and B into the plane, we can find k. Substituting the coordinates of S, we can find b. The angle is θ = arctan(k) / π*180. Let a2 be the angle θ with north as the positive X-axis and east as the positive Y-axis, i.e., a2 = ∠HCG, i.e., a2 = 90 - θ.

[0086] 3. Line l2 is parallel to line l3, where l2 is represented by y = cx + d. Substituting the coordinates of points A and D, we find that c and d are known.

[0087] 4. The line l3 can be expressed as y = cx + d1. Since the line l3 passes through the center of the scene, d1 can be obtained.

[0088] 5. The equations of lines l1 and l3 have been derived; the coordinates of point C can then be determined: x c = (d1-b) / (kc), y c =k*x c +b;

[0089] 6. Based on trigonometric relationships, the distance between any two points V1, C, and O1 can be calculated. First, we can obtain: L v1c =tan(z1)*L v1v Let a3 be the acute angle between the azimuth angle a observed from the center of the scene and the line l1. Then, when a is less than 180°, a3 = a - a2; when a is greater than 180°, a3 = a - a2 - 180°. Then L... v1c =tan(z1)*L v1v , L v1v If z1 is known, then L v1c L v1o1 L co1 All of these can be calculated.

[0090] 7. Calculate the coordinates of point O1. Both point C and point O1 lie on line l1, satisfying y c =k*x c +b, and y at the same time o1 =k*x o1 +b, subtract the two equations, and substitute the result into formula L in step 8. co1 , can be obtained All parameters in the formula are known. When a < 180 degrees, point O1 is to the right of C, i.e., a positive value is taken; otherwise, point O1 is to the left of C, i.e., a negative value is taken; simultaneously, according to y o1 =k*x o1 +b can be used to find the ordinate of point O1.

[0091] 8. If we use the distance formula between two points, we can obtain... Therefore, we can conclude that: Then the central angle ∠o between point S and the satellite satisfies: L v1s / 2 / π / L e =∠o / 360.

[0092] 9. From right-angle trigonometric functions, we know that... L in step 10 v1s With L v1v Substituting into this formula, we can obtain z2, which is the corrected observation field of view. By introducing the central angle from step 8, we can solve for the zenith angle z at point S.

[0093] The correction method for the observed azimuth angle may include the following steps:

[0094] 10. From right-angle trigonometric functions, we know that... L in step 7 v1o1 With L in step 8 so1 Substituting these values ​​into the equation, we can obtain a4.

[0095] 11. Then a2 + a4 is the azimuth angle with point C as the coordinate center. The difference between the azimuth angle centered at point S and the azimuth angle centered at point C is Lon. s -Lon c That is, the azimuth angle of point S is a = a² + a⁴ - (Lon) s -Lon c ).

[0096] To verify the effectiveness of the above solution, the following tests were conducted:

[0097] 1) Basic information about the test data

[0098] Since multispectral imagery does not provide pixel-by-pixel observation geometry, observation geometry data from hyperspectral imagery was used as test data to demonstrate its effectiveness. Three sets of data were used for testing: ZY1F satellite products 131871 and 132005, and GF5B satellite product 87156. These are designated as 1, 2, and 3, respectively.

[0099] 2) Test Method Description

[0100] Taking the maximum point in the image as an example, the zenith angle and azimuth angle of the four corner points in the image OGP file are used as the true values. r The reconstruction result of this patented method is the verification value l. The calculation formula based on its relative error is as follows:

[0101]

[0102] The relative error within 5% is used as the criterion for evaluating the effectiveness of the algorithm.

[0103] 3) Description of the testing process

[0104] The basic information of the scene center in the test data is shown in Table 1 below. This information was obtained from the image metadata.

[0105] Table 1:

[0106] Serial Number longitude latitude Solar zenith angle Sun azimuth Observation zenith angle Observation azimuth 1 122.9429 41.9409 49.9187 158.5045 3.5564 278.4426 2 103.2251 26.3903 35.0591 143.8016 0.0433 193.0071 3 94.7731 42.1601 52.3226 155.9226 0.0648 194.0798

[0107] Theoretically, the four corner points of an image are the points with the largest satellite field of view, i.e., the points with the largest errors. This method uses the four corner points of each image as test items. The coordinates of the four corner points are extracted from the image metadata, and the observed zenith angle and azimuth angle obtained from the satellite's precise orbit data processing are read respectively. The zenith angle and azimuth angle are calculated using the method of this embodiment, and the absolute error and relative error are calculated respectively, as shown in Table 2 below.

[0108] Table 2:

[0109]

[0110] The error analysis results are shown in Table 3 below:

[0111] Table 3:

[0112]

[0113]

[0114] As shown in Table 3 above, the maximum relative error of the zenith angle is 3.68%, and the maximum absolute error is 0.12 degrees. The maximum relative error of the azimuth angle is 4.52%, and the maximum absolute error is 4.92 degrees. Considering the lack of precise orbit data and the approximation of the Earth's sphere, the error of this algorithm is within an acceptable range compared to the precise orbit data. Compared to using the scene center observation method to replace the in-scene pixel-by-pixel method, the scheme provided in this embodiment can greatly improve the geometric accuracy of image pixel-by-pixel observation, thereby affecting calibration and quantitative applications.

[0115] Example 2

[0116] Reference Figure 5 The diagram illustrates a schematic representation of a multispectral image pixel-by-pixel observation geometric reconstruction device provided in an embodiment of the present invention. Figure 5 As shown, the multispectral image pixel-by-pixel observation geometric reconstruction device may include the following modules:

[0117] The first straight line acquisition module 510 is used to acquire the corner coordinates of the four corner points of the scene corresponding to the satellite image, the outer border line corresponding to the four corner points, and the first straight line parallel to the first outer border line among the outer border lines.

[0118] The intersection point acquisition module 520 is used to acquire the planar coordinates of the target point corresponding to the scene, the intersection of the line connecting the satellite position and the center of the Earth with the ground, the first intersection point of the straight line along the orbit direction of the scene's center point and the first straight line, and the second intersection point of the satellite position and the straight line along the orbit direction; the straight line connecting the satellite position and the second intersection point is perpendicular to the straight line along the orbit direction.

[0119] The observation geometry reconstruction module 530 is used to perform observation geometry reconstruction on the satellite image based on the equation of the line corresponding to the first line, the intersection point, the equation of the boundary frame corresponding to the outer frame, the first intersection point, the second intersection point, and the satellite orbital altitude.

[0120] Optionally, the observation geometry reconstruction module includes:

[0121] The distance acquisition unit is used to acquire, based on the straight line equation, the boundary frame equation, and the satellite orbital altitude, a first distance between the intersection point and the first intersection point, a second distance between the intersection point and the second intersection point, and a third distance between the first intersection point and the second intersection point;

[0122] The observation geometry reconstruction unit is used to perform observation geometry reconstruction on the observation field of view, observation zenith angle and observation azimuth angle of the satellite image based on the first distance, the second distance and the third distance.

[0123] Optionally, the observation geometry reconstruction unit includes:

[0124] The intersection point coordinate calculation subunit is used to calculate the intersection point coordinates of the second intersection point based on the third distance.

[0125] The central angle calculation subunit is used to calculate the fourth distance between the projection point of the satellite and the imaging point corresponding to the satellite image, the fifth distance between the satellite position and the intersection point, and the central angle between the imaging point and the satellite position based on the coordinates of the intersection point and the two-point distance formula.

[0126] The observation field of view calculation subunit is used to calculate the observation field of view of the satellite image based on the fourth distance and the fifth distance;

[0127] The observation zenith angle calculation subunit is used to calculate the observation zenith angle of the satellite image based on the fourth distance, the fifth distance, and the central angle.

[0128] The observation azimuth calculation subunit is used to calculate the observation azimuth of the satellite image based on the second distance and the fourth distance.

[0129] Optionally, the observation azimuth calculation subunit includes:

[0130] The first azimuth calculation subunit is used to calculate the first azimuth angle with the first intersection point as the coordinate center based on the second distance and the fourth distance.

[0131] The second azimuth angle calculation subunit is used to obtain the second azimuth angle with the imaging point as the coordinate center;

[0132] Azimuth difference acquisition subunit is used to acquire the azimuth difference between the first azimuth and the second azimuth;

[0133] The observation azimuth angle acquisition subunit is used to calculate the observation azimuth angle of the satellite image based on the first azimuth angle and the difference between the azimuth angles.

[0134] The specific embodiments described in this application are intended to enable those skilled in the art to gain a more comprehensive understanding of this application, but do not limit this application in any way. Therefore, those skilled in the art should understand that modifications or equivalent substitutions can still be made to this application; and all technical solutions and improvements that do not depart from the spirit and technical essence of this application should be covered within the scope of protection of this patent application.

[0135] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A pixel-by-pixel observation geometric reconstruction method for multispectral images, characterized in that, include: Obtain the corner coordinates of the four corner points of the scene corresponding to the satellite image, the outer border lines corresponding to the four corner points, and the first straight line parallel to the first outer border line among the outer border lines; Obtain the planar coordinates of the target point corresponding to the scene, the intersection of the line connecting the satellite position and the Earth's center with the ground, the first intersection of the straight line along the orbital direction of the scene's center point and the first straight line, and the second intersection of the satellite position and the straight line along the orbital direction; the straight line connecting the satellite position and the second intersection point is perpendicular to the straight line along the orbital direction. Based on the equation of the line corresponding to the first straight line, the intersection point, the equation of the border frame corresponding to the outer border line, the first intersection point, the second intersection point, and the satellite orbital altitude, the observation geometry of the satellite image is reconstructed. The step of performing observational geometric reconstruction of the satellite imagery based on the equation of the line corresponding to the first straight line, the equation of the border frame corresponding to the outer border line, the first intersection point, the second intersection point, and the satellite orbital altitude includes: Based on the equation of the straight line, the equation of the boundary frame, and the satellite orbital altitude, obtain the first distance between the intersection point and the first intersection point, the second distance between the intersection point and the second intersection point, and the third distance between the first intersection point and the second intersection point; Based on the first distance, the second distance, and the third distance, the observation geometry is reconstructed for the observation field of view, observation zenith angle, and observation azimuth angle of the satellite image. The observation geometry reconstruction of the satellite image based on the first distance, the second distance, and the third distance includes: Based on the third distance, the coordinates of the intersection point of the second intersection point are calculated; Based on the coordinates of the intersection point and the formula for the distance between two points, the fourth distance between the projection point of the satellite and the imaging point corresponding to the satellite image, the fifth distance between the satellite position and the intersection point, and the central angle between the imaging point and the satellite position are calculated. The observation field of view of the satellite image is calculated based on the fourth distance and the fifth distance. The observation zenith angle of the satellite image is calculated based on the fourth distance, the fifth distance, and the central angle. The observation azimuth angle of the satellite image is calculated based on the second distance and the fourth distance. The step of calculating the observed zenith angle of the satellite image based on the fourth distance, the fifth distance, and the central angle includes: Let point V be the satellite's position, V1 be the satellite's projection point on the ground, and point S be the imaging point. Let S be the observed zenith angle. Let S be the central angle between point S and the satellite. Let S be the field of view angle of the satellite observation point S. From the trigonometric function relationship, we get: Set the satellite orbital altitude to Earth's radius is Then we have: ； The step of calculating the observation azimuth angle of the satellite image based on the second distance and the fourth distance includes: Based on the second distance and the fourth distance, the first azimuth angle with the first intersection point as the coordinate center is calculated; Obtain the second azimuth angle with the imaging point as the coordinate center; Obtain the azimuth difference between the first azimuth and the second azimuth; The observation azimuth angle of the satellite image is calculated based on the first azimuth angle and the difference between the azimuth angles.

2. A multispectral image pixel-by-pixel observation geometric reconstruction device, characterized in that, include: The first straight line acquisition module is used to acquire the corner coordinates of the four corner points of the scene corresponding to the satellite image, the outer border line corresponding to the four corner points, and the first straight line parallel to the first outer border line among the outer border lines. The intersection point acquisition module is used to acquire the planar coordinates of the target point corresponding to the scene, the intersection of the line connecting the satellite position and the center of the Earth with the ground, the first intersection point of the straight line along the orbit direction of the scene's center point and the first straight line, and the second intersection point of the satellite position and the straight line along the orbit direction; the straight line connecting the satellite position and the second intersection point is perpendicular to the straight line along the orbit direction. The observation geometry reconstruction module is used to perform observation geometry reconstruction on the satellite image based on the equation of the line corresponding to the first line, the intersection point, the equation of the edge frame corresponding to the outer frame line, the first intersection point, the second intersection point, and the satellite orbital altitude. The observation geometry reconstruction module includes: The distance acquisition unit is used to acquire, based on the straight line equation, the boundary frame equation, and the satellite orbital altitude, a first distance between the intersection point and the first intersection point, a second distance between the intersection point and the second intersection point, and a third distance between the first intersection point and the second intersection point; An observation geometry reconstruction unit is used to perform observation geometry reconstruction on the observation field of view, observation zenith angle, and observation azimuth angle of the satellite image based on the first distance, the second distance, and the third distance. The observation geometric reconstruction unit includes: The intersection point coordinate calculation subunit is used to calculate the intersection point coordinates of the second intersection point based on the third distance. The central angle calculation subunit is used to calculate the fourth distance between the projection point of the satellite and the imaging point corresponding to the satellite image, the fifth distance between the satellite position and the intersection point, and the central angle between the imaging point and the satellite position based on the coordinates of the intersection point and the two-point distance formula. The observation field of view calculation subunit is used to calculate the observation field of view of the satellite image based on the fourth distance and the fifth distance; The observation zenith angle calculation subunit is used to calculate the observation zenith angle of the satellite image based on the fourth distance, the fifth distance, and the central angle. An observation azimuth calculation subunit is used to calculate the observation azimuth of the satellite image based on the second distance and the fourth distance. The observed zenith angle calculation subunit includes: Let point V be the satellite's position, V1 be the satellite's projection point on the ground, and point S be the imaging point. Let S be the observed zenith angle. Let S be the central angle between point S and the satellite. Let S be the field of view angle of the satellite observation point S. From the trigonometric function relationship, we get: Set the satellite orbital altitude to Earth's radius is Then we have: ； The observation azimuth calculation subunit includes: The first azimuth calculation subunit is used to calculate the first azimuth angle with the first intersection point as the coordinate center based on the second distance and the fourth distance. The second azimuth angle calculation subunit is used to obtain the second azimuth angle with the imaging point as the coordinate center; Azimuth difference acquisition subunit is used to acquire the azimuth difference between the first azimuth and the second azimuth; The observation azimuth angle acquisition subunit is used to calculate the observation azimuth angle of the satellite image based on the first azimuth angle and the difference between the azimuth angles.

Images