Method and system for correcting three-dimensional positioning accuracy of rain measuring radar in orbit by using DEM

Abstract

This invention provides a method and system for correcting the three-dimensional spatial positioning accuracy of a rainfall radar in orbit using a DEM (Diagram of Earth's Imagery). The method includes: calculating the latitude and longitude of the satellite nadir point and the detection point to be corrected on the Earth's surface; calculating the satellite zenith angle at the detection point to be corrected; calculating the correction distance based on the DEM of the detection point; constructing a spherical triangle based on the projection relationship of the detection point in the range direction, and calculating the latitude and longitude of an auxiliary point; constructing a similar triangle using the auxiliary point, the detection point to be corrected, and the actual detection point, and calculating the corrected detection point position; and using the corrected detection point's position in the range direction to perform range correction on the radar echo signal, thus completing the correction of the three-dimensional spatial positioning accuracy of the rainfall radar. This invention can accurately distinguish between near-surface rainfall signals and ground clutter signals, effectively eliminating invalid surface and subsurface echo interference, and is an important prerequisite and technical guarantee for the refined application of three-dimensional signals from rainfall radar in orbit.

Description

Technical Field

[0001] This invention relates to the field of research on on-orbit correction of microwave rain measurement radar echo signals, specifically, to a method and system for on-orbit correction of three-dimensional spatial positioning accuracy of rain measurement radar using DEM. Background Technology

[0002] In the field of meteorological observation, spaceborne precipitation measurement radar is the core payload for acquiring three-dimensional structure information of precipitation in tropical and subtropical regions. As an active microwave sounding instrument, its detection accuracy directly affects the intensity, spatial distribution, and accuracy of numerical forecasting models of precipitation. Considering that precipitation information from precipitation radar exhibits spatial distribution characteristics based on the location of the surface detection point (two-dimensional coordinate system) and the range position (third-dimensional coordinate system) as reference coordinate systems, the accuracy of three-dimensional spatial positioning is a crucial step in the preprocessing of precipitation radar data. Generally, when determining the location of the ground detection point, the Earth is approximated as an ellipsoidal model, but the actual Earth's surface has topographic relief, i.e., elevation differences. It is precisely because of the diverse underlying surface types of the Earth, such as mountains, plains, cliffs, and oceans, that neglecting elevation information during the positioning process will introduce positioning errors into both the location of the surface detection point and the range position.

[0003] Digital Elevation Models (DEMs), as a global high-precision terrain data source, provide a stable reference for surface elevation. Methods for correcting the positioning accuracy of ground detection points on precipitation radars typically fall into two categories. One method first determines the elevation distribution of the nadir point and then uses a lookup table based on the offsets of other detection points relative to the nadir point to quickly determine its elevation value and complete the correction. However, this method usually has low positioning accuracy. Another method iteratively approximates the DEM distribution using the satellite line-of-sight vector to obtain the optimal elevation distribution of the detection point and complete the positioning accuracy correction. However, this method requires subjective selection of key parameters such as the number of iterations and involves cumbersome calculations, making it unsuitable for on-board processing. Therefore, it is necessary to propose a method and system for on-orbit correction of the three-dimensional spatial positioning accuracy of precipitation radars using DEMs. This involves calculating an on-orbit spatial positioning accuracy correction method suitable for the engineering parameters of precipitation radars through a finite number of steps, laying a solid foundation for obtaining refined three-dimensional precipitation structure distribution characteristics of the observation area on-orbit.

[0004] Patent CN113325422A discloses a method and system for target positioning and three-dimensional processing of rainfall information using a space-based rainfall measurement radar. It measures the position and velocity of a satellite platform in the WGS-84 Earth-Fixed Coordinate System using GPS or BeiDou systems, establishes slant range equations, cosine equations, and orthogonal equations, solves the system of equations to calculate the location information of the rainfall observation area, and establishes a three-dimensional grid array for three-dimensional processing and display of rainfall information. However, it does not disclose the specific method for calculating the corrected distance for the radar line-of-sight direction based on the DEM elevation value of the detection point, using a high-precision digital elevation model (DEM) as the core input parameter integrated into the on-orbit positioning correction process of the space-based rainfall measurement radar.

[0005] In summary, given the problems of the existing technologies, researching a method and system for on-orbit correction of the three-dimensional spatial positioning accuracy of rain-measuring radar using DEM has become a critical task that urgently needs to be addressed. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method and system for on-orbit correction of the three-dimensional spatial positioning accuracy of rain-measuring radar using a DEM.

[0007] The present invention provides a method for correcting the three-dimensional spatial positioning accuracy of a rain-measuring radar in orbit using a DEM, which specifically includes the following steps:

[0008] Step S1: Calculate the latitude and longitude positions of the satellite nadir point and the detection point to be corrected on the Earth's surface; Step S2: Calculate the satellite zenith angle at the detection point to be corrected; Step S3: Calculate the correction distance based on the DEM of the detection point to be corrected; Step S4: Construct a spherical triangle based on the projection relationship of the detection point to be corrected in the distance direction, and calculate the latitude and longitude of the auxiliary point; Step S5: Construct similar triangles using the auxiliary points, the detection points to be corrected, and the actual detection point positions, and calculate the corrected detection point positions; Step S6: Use the corrected position of the detection point in the range direction to perform range correction on the radar echo signal, thus completing the correction of the three-dimensional spatial positioning accuracy of the rain measurement radar.

[0009] Preferably, in step S1, calculating the latitude and longitude positions of the satellite nadir point and the detection point to be corrected on the Earth's surface includes: using the satellite's position, velocity, and attitude at the detection time, combined with the line-of-sight vector of the rain-measuring radar nadir point beam and the line-of-sight vector of the detection beam, calculating the intersection of the line-of-sight vector with the Earth's surface, and obtaining the position information of the satellite nadir point and the detection point to be corrected, wherein the position information is latitude and longitude information in the WGS84 coordinate system.

[0010] Preferably, in step S2, calculating the satellite zenith angle at the detection point to be corrected includes: Based on the satellite's position information at the specified detection time and the location of the detection point to be corrected, the zenith angle of the satellite at the detection point to be corrected is calculated using the sine theorem. The calculation formula is as follows:

[0011] in, This indicates the zenith angle of the satellite at the detection point to be corrected. Indicates the detection angle of the rain-measuring radar. Indicates satellite altitude. This represents the Earth's radius.

[0012] Preferably, in step S3, calculating the correction distance based on the DEM of the detection point to be corrected includes: constructing a concentric spherical shell geometric model of the Earth, wherein... For satellite position, For the Earth's core, The location of the detection point to be corrected. Define a spatial auxiliary point located on a concentric spherical shell. for The intersection of the line and the Earth's surface, i.e. for The vertical projection point on the Earth's surface; the correction distance is the distance the detection point to be corrected and the auxiliary point move on the Earth's surface, i.e., the arc length. Based on the preset condition that the maximum surface elevation is much smaller than the satellite-to-ground distance, the corrected distance is approximated as:

[0013] in, For the satellite zenith angle, The DEM elevation value of the detection point to be corrected is given.

[0014] Preferably, in step S4, constructing a spherical triangle based on the projection relationship of the detection point to be corrected in the distance direction and calculating the latitude and longitude of the auxiliary point includes: constructing a spherical triangle and ,in, The Earth's North Pole, The satellite's nadir point, The detection point is to be corrected. As auxiliary ground projection points; set The latitude and longitude coordinates of the point are , The latitude and longitude coordinates of the point are , The latitude and longitude coordinates of the point are ; Calculate the satellite's nadir point using the cosine theorem for spherical triangles. With the detection point to be corrected The surface arc length between :

[0015]

[0016] Calculate spherical angles :

[0017] calculate latitude :

[0018] in, ,in The DEM elevation value of the detection point to be corrected. The zenith angle of the satellite; calculate longitude :

[0019] Through the above calculations, we obtain latitude and longitude coordinates , that is, auxiliary point Its latitude and longitude location.

[0020] Preferably, in step S5, constructing a similar triangle using the auxiliary point, the detection point to be corrected, and the actual detection point location, and calculating the corrected detection point location includes: constructing a similar triangle model based on height projection relationships, wherein, a definition is provided. The detection point to be corrected has the following elevation: , for The projection point on the Earth's surface, Let the auxiliary point be located on the concentric spherical shell, and its elevation be... , for The projection point on the Earth's surface, The projection of the auxiliary point onto the DEM surface has the following elevation: , The corrected actual detection point has the following elevation: Based on the preset condition that the elevation fluctuations are small within the moving distance between the detection point to be corrected and the auxiliary point, the calculation is performed using the proportional relationship of similar triangles:

[0021] Substituting the elevation data, we get:

[0022] in, express and The vertical distance between them express elevation , express and The distance between them express and The distance between them express elevation , express and The distance between them express and The total distance between them; By combining the above formulas, the elevation of the detection point after calculation and correction can be obtained. for:

[0023] Based on the corrected elevation of the detection points The corresponding latitude and longitude coordinates are found in reverse along the detection beam path to determine the corrected detection point. The final position.

[0024] Preferably, in step S6, the radar echo signal is corrected in the range direction using the corrected position of the detection point to complete the three-dimensional spatial positioning accuracy correction of the rain-measuring radar. This includes: calculating the distance between the two points using the latitude and longitude positions of the corrected detection point and the latitude and longitude positions of the detection point to be corrected, denoted as... Determine the range database number of the surface layer in the radar echo signal, denoted as . ;set up For the rain-measuring radar at fixed intervals in each layer of the range direction, calculate the corrected range database number of the detection point. The calculation formula is as follows:

[0025] in, This represents the floor function; Based on the original distribution of radar echo signals in the range direction, and combined with the corrected location of the detection points in the range direction, the range database number is set in... The following signals are marked as invalid signals. After eliminating invalid signals, the three-dimensional spatial positioning accuracy of the rain-measuring radar is finally corrected.

[0026] This invention also provides a system for correcting the three-dimensional spatial positioning accuracy of a rainfall radar using a DEM in orbit. This system can be implemented by executing the steps of the method for correcting the three-dimensional spatial positioning accuracy of a rainfall radar using a DEM in orbit. That is, those skilled in the art can understand the method for correcting the three-dimensional spatial positioning accuracy of a rainfall radar using a DEM in orbit as a preferred embodiment of the system for correcting the three-dimensional spatial positioning accuracy of a rainfall radar using a DEM in orbit. The system includes: The coordinate calculation module is used to calculate the latitude and longitude positions of the satellite nadir point and the detection point to be corrected on the Earth's surface; Angle calculation module, used to calculate the satellite zenith angle at the detection point to be corrected; The distance correction module is used to calculate the correction distance based on the DEM of the detection point to be corrected. The auxiliary point calculation module is used to construct a spherical triangle based on the projection relationship of the detection point to be corrected in the distance direction, and calculate the latitude and longitude of the auxiliary point; The position correction module is used to construct a similar triangle using the auxiliary point, the detection point to be corrected, and the actual detection point position, and to calculate the corrected detection point position. The data correction module is used to perform range correction on the radar echo signal by using the corrected position of the detection point in the range direction, thereby completing the correction of the three-dimensional spatial positioning accuracy of the rain measurement radar.

[0027] The present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the method for on-orbit correction of the three-dimensional spatial positioning accuracy of rain measuring radar using DEM.

[0028] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, it implements the steps of the method for correcting the three-dimensional spatial positioning accuracy of rain measuring radar using DEM in orbit.

[0029] Compared with the prior art, the present invention has the following beneficial effects: In existing technologies, while lookup-based correction methods are fast, their positioning accuracy is low. Methods based on iterative approximation using view vectors and DEMs offer higher accuracy, but the number of iterations depends on subjective human selection, resulting in a cumbersome and lengthy computation process that fails to meet the stringent real-time and resource consumption requirements of onboard processors. This invention innovatively proposes a deterministic computational model based on geometric analysis, utilizing the projection relationship of the detection point to be corrected onto the range direction of the rain-measuring radar. By constructing a spherical triangle to calculate the position of auxiliary points, and then based on the positional relationships of the auxiliary points, the detection point to be corrected, and the corrected detection point, the on-orbit correction of the three-dimensional spatial positioning accuracy of the rain-measuring radar is achieved in a finite number of steps. This method eliminates the need for setting iteration thresholds or manual parameters, significantly reducing computational complexity and filling the technological gap between high accuracy and low computational cost. It is particularly suitable for real-time on-orbit signal processing on satellites with limited computational resources.

[0030] Furthermore, this invention constructs a concentric spherical shell geometric model of the Earth, utilizes spherical trigonometry to accurately calculate the spatial relationship between auxiliary points and points to be corrected, and combines DEM data to correct parallax using similar triangles, fully considering the impact of Earth's curvature and terrain undulations on side-looking radar observations. This method can accurately correct radar echo position offsets caused by surface undulations such as mountains and plateaus, achieving precise positioning of rainfall radar echo signals in three-dimensional space. Based on the corrected high-precision three-dimensional spatial position, this invention can more accurately calculate the specific layer of the Earth's surface in the radar range direction, accurately distinguish near-surface rainfall signals from ground clutter signals, and effectively eliminate invalid surface and subsurface echo interference. This is an important prerequisite and technical guarantee for the refined application of three-dimensional rainfall radar signals in orbit. Attached Figure Description

[0031] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 The flowchart illustrates a method for on-orbit correction of the three-dimensional spatial positioning accuracy of a rain-measuring radar using a DEM, as provided by this invention.

[0032] Figure 2 This is a schematic diagram showing the location distribution of the detection points to be corrected and the auxiliary points in an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of a spherical triangle in an embodiment of the present invention.

[0034] Figure 4 This is a schematic diagram of the local relationship of the spherical triangle in an embodiment of the present invention.

[0035] Figure 5 This is a schematic diagram showing the location distribution of the detection point to be corrected, the auxiliary point, and the corrected detection point in an embodiment of the present invention. Detailed Implementation

[0036] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0037] This invention provides a method for correcting the three-dimensional spatial positioning accuracy of a rain-measuring radar using a DEM in orbit, such as... Figure 1 As shown, it includes the following steps: Step 1: Calculate the latitude and longitude of the satellite nadir point and the detection point to be corrected on the Earth's surface.

[0038] Specifically, by utilizing the satellite's position, velocity, and attitude at the time of detection, combined with the beam pointing geometry of the rain-measuring radar, the positional information of the satellite's nadir point and the detection point to be corrected is obtained, i.e., the latitude and longitude information in the WGS84 coordinate system. The intersection point of the satellite nadir point beam line-of-sight vector and the Earth's reference ellipsoid is calculated and denoted as the satellite nadir point. Its latitude and longitude coordinates are as follows Calculate the intersection point of the rain-measuring radar detection beam line vector and the Earth's reference ellipsoid, and denote it as the detection point to be corrected. Its latitude and longitude coordinates are as follows .

[0039] Step 2: Calculate the satellite zenith angle at the detection point to be corrected.

[0040] Specifically, using the positions of the satellite and the probe point to be corrected in the WGS84 coordinate system at the time of detection, combined with the satellite's geometric relationship at the time of detection, the zenith angle of the probe point to be corrected is calculated using the sine theorem. The calculation formula is as follows:

[0041] in, This indicates the zenith angle of the satellite at the detection point to be corrected. Indicates the detection angle of the rain-measuring radar. Indicates satellite altitude. This represents the Earth's radius.

[0042] Step 3: Calculate the correction distance based on the DEM of the detection point to be corrected. The correction distance refers to the distance the detection point to be corrected and the auxiliary point move on the Earth's surface, taking into account the influence of elevation.

[0043] like Figure 2 As shown, a concentric spherical shell geometric model of the Earth is constructed. The solid black line represents the Earth's surface, the black curve represents the DEM distribution, and the dashed black line represents the concentric spherical shell with the D0 elevation as the standard. For satellite position, For the Earth's core, The location of the detection point to be corrected. For the spatial correction point located on the concentric spherical shell, for The intersection of the line with the Earth's surface, in this embodiment, will be... As auxiliary points for calculating the target; The correction distance is defined as the distance traveled on the Earth's surface by the probe point to be corrected and the auxiliary point, i.e., the arc length. Considering that the maximum surface elevation (less than 9 km) is much smaller than the Earth-space distance (greater than 400 km), therefore For small quantities, approximate calculations can be used:

[0044] in, For the satellite zenith angle, The DEM elevation values ​​of the detection points to be corrected are shown.

[0045] Step 4: Construct a spherical triangle based on the projection relationship of the detection point to be corrected in the distance direction, and calculate the latitude and longitude of the auxiliary point.

[0046] like Figure 3 As shown, and For the Earth's North and South Poles, For the center of the ball, The satellite's nadir position is given by the following coordinates: , The location of the detection point to be corrected is marked with latitude and longitude coordinates as follows: , For the auxiliary point location, its coordinates (latitude and longitude) to be determined are: ,in , and All are Earth radius R e .right Figure 3 The gray area is magnified locally, such as... Figure 4 As shown, , and It is a spherical triangle. In spherical geometry, , , .

[0047] In a spherical triangle In the middle, the satellite's nadir point is calculated using the cosine theorem for spherical triangles. With the detection point to be corrected The surface arc length between :

[0048]

[0049] Calculate spherical angles :

[0050] Based on the corrected distance calculated in step 3, we obtain ; In a spherical triangle In the middle, according to the cosine theorem of spherical triangles, calculate the sides. :

[0051] because ,calculate latitude :

[0052] In a spherical triangle In the middle, according to the cosine theorem of spherical triangles, calculate :

[0053] according to ,calculate longitude :

[0054] Through the above calculations, we obtain latitude and longitude coordinates , that is, auxiliary point Its latitude and longitude location.

[0055] Step 5: Construct similar triangles using auxiliary points, the detection point to be corrected, and the actual detection point positions, and calculate the corrected detection point positions.

[0056] like Figure 5 As shown, the solid black line represents the Earth's surface, the black curve represents the DEM distribution, and the black dashed line represents the area below the surface. The elevation is a standard concentric spherical shell. The elevation is The elevation at point C2 is , The location of the detection point to be corrected. for The projection point, For auxiliary point positions, for The projection point, For the projection points of auxiliary points on the DEM, To correct the location of the detection point, The elevation is The calculation formula is as follows: If the elevation fluctuations are small within the moving distance between the detection point to be corrected and the auxiliary point, then:

[0057] Substituting the elevation data, we get:

[0058] By combining the above formulas, the elevation of the detection point after calculation and correction can be obtained. for:

[0059] Based on the corrected elevation of the detection points The corresponding latitude and longitude coordinates are found in reverse along the detection beam path to determine the corrected detection point. The final position.

[0060] Step 6: Use the corrected position of the detection point in the range direction to perform range correction on the radar echo signal, thus completing the correction of the three-dimensional spatial positioning accuracy of the rain measurement radar.

[0061] Specifically, based on the corrected latitude and longitude positions of the detection point and the latitude and longitude positions of the detection point to be corrected, the distance between the two points is calculated and denoted as... This allows us to determine the corrected probe point's position in the distance direction, and the surface layer is then numbered as follows. The corrected layer number is: ,in, For each layer in the range direction, a fixed interval is used; based on the original distribution of radar echo signals in the range direction, combined with the corrected position of the detection points in the range direction, the points are numbered... The following signals are marked as invalid signals. After eliminating invalid signals, the three-dimensional spatial positioning accuracy of the rain-measuring radar is finally corrected.

[0062] Through the above specific implementation steps, by determining the position of the auxiliary point in the distance upward of the detection point to be corrected, and combining the positional relationship between the detection point to be corrected and the corrected detection point, the on-orbit three-dimensional spatial positioning accuracy correction of the rain measuring radar is completed. Under the premise of avoiding tedious and lengthy iterative calculations, the positioning accuracy of the ground detection point and the distance upward is guaranteed. This is an important prerequisite and technical guarantee for the refined application of three-dimensional signals of rain measuring radar in orbit.

[0063] This invention also provides a system for correcting the three-dimensional spatial positioning accuracy of a rainfall radar using a DEM in orbit. This system can be implemented by executing the steps of the method for correcting the three-dimensional spatial positioning accuracy of a rainfall radar using a DEM in orbit. That is, those skilled in the art can understand the method for correcting the three-dimensional spatial positioning accuracy of a rainfall radar using a DEM in orbit as a preferred embodiment of the system for correcting the three-dimensional spatial positioning accuracy of a rainfall radar using a DEM in orbit. The system includes: The coordinate calculation module is used to calculate the latitude and longitude positions of the satellite nadir point and the detection point to be corrected on the Earth's surface; Angle calculation module, used to calculate the satellite zenith angle at the detection point to be corrected; The distance correction module is used to calculate the correction distance based on the DEM of the detection point to be corrected; The auxiliary point calculation module is used to construct a spherical triangle based on the projection relationship of the detection point to be corrected in the distance direction, and calculate the latitude and longitude of the auxiliary point; The position correction module is used to construct similar triangles using auxiliary points, the detection point to be corrected, and the actual detection point positions, and to calculate the corrected detection point positions. The data correction module is used to perform range correction on the radar echo signal by using the corrected position of the detection point in the range direction, thereby completing the correction of the three-dimensional spatial positioning accuracy of the rain measurement radar.

[0064] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0065] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for on-orbit correction of the three-dimensional spatial positioning accuracy of a rain-measuring radar using a DEM, characterized in that, include: Step S1: Calculate the latitude and longitude positions of the satellite nadir point and the detection point to be corrected on the Earth's surface; Step S2: Calculate the satellite zenith angle at the detection point to be corrected; Step S3: Calculate the correction distance based on the DEM of the detection point to be corrected; Step S4: Construct a spherical triangle based on the projection relationship of the detection point to be corrected in the distance direction, and calculate the latitude and longitude of the auxiliary point; Step S5: Construct similar triangles using the auxiliary points, the detection points to be corrected, and the actual detection point positions, and calculate the corrected detection point positions; Step S6: Use the corrected position of the detection point in the range direction to perform range correction on the radar echo signal, thus completing the correction of the three-dimensional spatial positioning accuracy of the rain measurement radar.

2. The method for on-orbit correction of three-dimensional spatial positioning accuracy of rain-measuring radar using DEM according to claim 1, characterized in that, In step S1, calculating the latitude and longitude positions of the satellite nadir point and the detection point to be corrected on the Earth's surface includes: By utilizing the satellite's position, velocity, and attitude at the time of detection, and combining the line-of-sight vector of the rain-measuring radar's nadir point beam and the line-of-sight vector of the detection beam, the intersection of the line-of-sight vector with the Earth's surface is calculated, thereby obtaining the position information of the satellite's nadir point and the detection point to be corrected. The position information is latitude and longitude information in the WGS84 coordinate system.

3. The method for on-orbit correction of three-dimensional spatial positioning accuracy of rain-measuring radar using DEM according to claim 1, characterized in that, In step S2, calculating the satellite zenith angle at the detection point to be corrected includes: Based on the satellite's position information at the specified detection time and the location of the detection point to be corrected, the zenith angle of the satellite at the detection point to be corrected is calculated using the sine theorem. The calculation formula is as follows: in, This indicates the zenith angle of the satellite at the detection point to be corrected. Indicates the detection angle of the rain-measuring radar. For satellite altitude, This represents the Earth's radius.

4. The method for on-orbit correction of three-dimensional spatial positioning accuracy of rain-measuring radar using DEM according to claim 1, characterized in that, In step S3, calculating the correction distance based on the DEM of the detection point to be corrected includes: Construct a geometric model of the Earth's concentric spherical shell, in which, For satellite position, For the Earth's core, The location of the detection point to be corrected. Define a spatial auxiliary point located on a concentric spherical shell. for The intersection of the line and the Earth's surface, i.e. for The vertical projection point on the Earth's surface; The correction distance is the distance the detection point to be corrected and the auxiliary point move on the Earth's surface, i.e., the arc length. ; Based on the preset condition that the maximum surface elevation is much smaller than the satellite-to-ground distance, the corrected distance is approximated as: in, The zenith angle of the satellite. The DEM elevation value of the detection point to be corrected is given.

5. The method for on-orbit correction of three-dimensional spatial positioning accuracy of rain-measuring radar using DEM according to claim 1, characterized in that, In step S4, a spherical triangle is constructed based on the projection relationship of the detection point to be corrected in the distance direction, and the latitude and longitude of the auxiliary point are calculated, including: Construct a spherical triangle and ,in, The Earth's North Pole, The satellite's nadir point, The detection point is to be corrected. For auxiliary points, refer to the ground projection points; set up The latitude and longitude coordinates of the point are , The latitude and longitude coordinates of the point are , The latitude and longitude coordinates of the point are ; Calculate the satellite's nadir point using the cosine theorem for spherical triangles. With the detection point to be corrected Surface arc length between : Calculate spherical angles : calculate latitude : in, ,in The DEM elevation value of the detection point to be corrected. The zenith angle of the satellite; calculate longitude : Through the above calculations, we obtain latitude and longitude coordinates , that is, auxiliary point Its latitude and longitude location.

6. The method for on-orbit correction of three-dimensional spatial positioning accuracy of rain-measuring radar using DEM according to claim 1, characterized in that, In step S5, a similar triangle is constructed using the auxiliary point, the detection point to be corrected, and the actual detection point position, and the corrected detection point position is calculated, including: Construct a similar triangle model based on height projection relationship, where, define The detection point to be corrected has the following elevation: , for The projection point on the Earth's surface, Let the auxiliary point be located on the concentric spherical shell, and its elevation be... , for The projection point on the Earth's surface, The projection of the auxiliary point onto the DEM surface has the following elevation: , The corrected actual detection point has the following elevation: ; Based on the pre-set condition that the elevation fluctuation changes little within the moving distance between the detection point to be corrected and the auxiliary point, the calculation is performed using the proportional relationship of similar triangles: Substituting the elevation data, we get: in, express and The vertical distance between them express elevation , express and The distance between them express and The distance between them express elevation , express and The distance between them express and The total distance between them; By combining the above formulas, the elevation of the detection point after calculation and correction can be obtained. for: Based on the corrected elevation of the detection points The corresponding latitude and longitude coordinates are found in reverse along the detection beam path to determine the corrected detection point. The final position.

7. The method for on-orbit correction of three-dimensional spatial positioning accuracy of rain-measuring radar using DEM according to claim 1, characterized in that, In step S6, the radar echo signal is corrected in the range direction using the corrected position of the detection point in the range direction, thus completing the correction of the three-dimensional spatial positioning accuracy of the rain-measuring radar, including: Using the corrected latitude and longitude positions of the detection point and the detection point to be corrected, the distance between the two points is calculated and denoted as . ; The range database number of the surface layer in the radar echo signal is determined and denoted as . ; set up For the rain-measuring radar at fixed intervals in each layer of the range direction, calculate the corrected range database number of the detection point. The calculation formula is as follows: in, This represents the floor function; Based on the original distribution of radar echo signals in the range direction, and combined with the corrected location of the detection points in the range direction, the range database number is set in... The following signals are marked as invalid signals. After eliminating invalid signals, the three-dimensional spatial positioning accuracy of the rain-measuring radar is finally corrected.

8. A system for on-orbit correction of the three-dimensional spatial positioning accuracy of a rainfall radar using a DEM, characterized in that, include: The coordinate calculation module is used to calculate the latitude and longitude positions of the satellite nadir point and the detection point to be corrected on the Earth's surface; Angle calculation module, used to calculate the satellite zenith angle at the detection point to be corrected; The distance correction module is used to calculate the correction distance based on the DEM of the detection point to be corrected. The auxiliary point calculation module is used to construct a spherical triangle based on the projection relationship of the detection point to be corrected in the distance direction, and calculate the latitude and longitude of the auxiliary point; The position correction module is used to construct a similar triangle using the auxiliary point, the detection point to be corrected, and the actual detection point position, and to calculate the corrected detection point position. The data correction module is used to perform range correction on the radar echo signal by using the corrected position of the detection point in the range direction, thereby completing the correction of the three-dimensional spatial positioning accuracy of the rain measurement radar.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for correcting the three-dimensional spatial positioning accuracy of rain measuring radar using DEM in orbit, as described in any one of claims 1 to 7.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for correcting the three-dimensional spatial positioning accuracy of rain measuring radar using DEM in orbit, as described in any one of claims 1 to 7.

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