Method and system for converting detection signals of satellite-borne rain detection radar in three-dimensional coordinate system

Abstract

The invention provides a method and a system for converting detection signals of a satellite-borne rain detection radar in a three-dimensional coordinate system. The method comprises the following steps: calculating to obtain satellite position, speed and attitude information at a radar detection moment and a radar detection beam visual vector; based on information such as satellite position, speed and attitude, position information of radar detection ground sampling points is calculated; calculating the position from the first echo of the radar to the earth surface in the distance direction, and further determining the distance library number of the earth surface layer; radar echo reflectivity factor distribution in the distance direction is obtained through calculation; calculating a local zenith angle of the earth sampling point, and calculating to obtain radar echo reflectivity factor distribution at a corresponding height in a vertical direction; and calculating to obtain radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction. According to the invention, satellite-borne microwave rain radar detection signals are realized, i.e., conversion of radar echo reflectivity factors from a distance direction to a vertical direction is realized, and distribution characteristics of the rain radar detection signals in a three-dimensional space are obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of meteorological satellite active microwave radar remote sensing data processing. Specifically, it relates to a method and system for converting radar detection signals in a three-dimensional coordinate system. More specifically, it is a method and system for converting detection signals of spaceborne microwave rain radar in a three-dimensional coordinate system. Background Art

[0002] Precipitation is an important part of the global water cycle process and has always been a hot research topic in the atmospheric science community. In the precipitation system, the latent heat energy released during the phase change process will change the large-scale circulation movement, affect the atmospheric energy cycle and the balance of the earth's radiation budget. The differences in the microphysical characteristics in precipitation clouds determine the precipitation properties, and the climate changes of different types of precipitation characteristics often reveal the climate changes of weather systems and cloud microphysical characteristics.

[0003] In order to obtain the characteristics of large-scale precipitation systems, it is necessary to network multiple ground-based rain radars for detection. During the detection process, the standardization degree of measurement instruments and data quality will directly affect the precipitation detection results. However, spaceborne detection instruments can make up for this defect and obtain the precipitation characteristics of large-scale regions, especially areas where people rarely go.

[0004] Due to the inherent characteristics of the detection band, spaceborne visible light / infrared instruments are difficult to have the ability to penetrate precipitation cloud systems and can only obtain remote sensing information on the top of precipitation clouds and a very limited depth in the lower part. In contrast, spaceborne microwave detection instruments can perform all-weather remote sensing detection due to their longer wavelengths, have the ability to penetrate precipitation cloud bodies, and thus obtain cloud body characteristic information. Spaceborne microwave active detection instruments can obtain detection resolution in the range direction compared with passive detection instruments, and can obtain the three-dimensional structure characteristic distribution of precipitation systems.

[0005] Therefore, using the active remote sensing detection data of spaceborne microwave rain radar can obtain the climate distribution characteristics of the three-dimensional structure of precipitation in tropical and subtropical regions, which is of great significance for research fields such as climate change and disaster prevention and mitigation.

[0006] The process of determining the three-dimensional spatial distribution of the detection signals of spaceborne rain radar can be basically divided into two steps, namely, determining the position of the ground sampling points of the rain radar on the earth's surface and the distribution of the radar echo reflectivity factor of the ground sampling points in the vertical direction. However, based on the original detection signals of the rain radar, only the distribution of the radar echo reflectivity factor in the range direction can be given, and the physical meaning of the parameters is often not clear, which is not convenient for direct use in scientific calculations and research work. Therefore, when processing the detection signals of the rain radar, it involves the conversion from the range direction to the vertical direction to obtain the three-dimensional distribution characteristics of the radar echo reflectivity factor that can be conveniently used and has a clear physical meaning.

[0007] At present, for the processing technology of rain-measuring radar data in three-dimensional space, a common method is to establish a new three-dimensional grid and resample it separately in the horizontal and vertical directions. Obviously, the resampling process will lead to the loss of the original detection signal. At the same time, during the detection period of the rain-measuring radar, due to the influence of the undulation of the surface elevation, there are differences in the distribution height of the surface, resulting in a certain degree of loss of information in the vertical direction of the pre-established new grid. The loss of the original detection signal in three-dimensional space will ultimately lead to a lack of ability to depict the detailed characteristics of the cloud precipitation system.

[0008] Determine the position information of the ground sampling points according to the intersection points of the detection beam view vectors of the rain-measuring radar and the Earth's surface. The determination of the three-dimensional distribution of the original detection signal in the range direction can maximize the retention of the characteristics of the radar echo information. Conduct the detection signal of the ground sampling points, that is, convert the radar echo reflectivity factor from the range direction, that is, the number of layers corresponding to the range bins, to the vertical direction, that is, the height corresponding to the number of layers, which can improve the blurring phenomenon of detection details caused by the resampling process in the previous processing methods.

[0009] Patent document CN117075113A discloses a method for calculating the hail diameter based on the vertical profile of radar echoes. The scheme includes radar base data coordinate conversion, linear interpolation of radar intensity echo dBZ(x, y, z), establishing the vertical profile of the echo, calculating the flux value of the hail kinetic energy E, calculating the weight function of the temperature, and the severe hail index, and finally making a forecast of the maximum expected hail size. This scheme improves the existing hail diameter algorithm, abandons the storm cell SCIT algorithm, and directly applies the vertical profile of the echo to calculate the hail diameter, making the calculation of the hail diameter more accurate and convenient, and being very important for hail forecasting, warning, identification, and tracking. However, this scheme does not solve the determination of the three-dimensional distribution of the original detection signal. This problem urgently needs to be solved. Summary of the Invention

[0010] Aiming at the defects in the prior art, the purpose of the present invention is to provide a method and system for converting the detection signal of a spaceborne rain-measuring radar in a three-dimensional coordinate system.

[0011] According to a method for converting the detection signal of a spaceborne rain-measuring radar in a three-dimensional coordinate system provided by the present invention, it includes:

[0012] Step S1: Collect and obtain the satellite parameters and the radar detection beam view vectors at the detection moment of the rain-measuring radar based on the satellite parameters and radar parameters;

[0013] Step S2: Calculate the position information of the radar detection ground sampling points based on the satellite parameters at the detection moment of the rain-measuring radar according to the intersection points of the radar detection beam view vectors and the Earth's surface;

[0014] Step S3: Calculate the position of the first echo of the radar from the ground surface in the range direction, and then determine the range bin number of the surface layer; based on the position information, calculate and obtain the radar echo reflectivity factor distribution in the range direction;

[0015] Step S4: Based on the position information and the satellite position, calculate the local zenith angle of the ground sampling point, and then based on the local zenith angle and the radar echo reflectivity factor distribution in the range direction, calculate and obtain the radar echo reflectivity factor distribution at the corresponding height in the vertical direction;

[0016] Step S5: Based on the radar echo reflectivity factor distribution at the corresponding height in the vertical direction, obtain the radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction.

[0017] Preferably, in the step S1, the satellite parameters include: satellite position, satellite speed and satellite attitude; the radar parameters include: radar scanning angle, number of radar scanning wave positions and radar echo power;

[0018] The radar is a rain-measuring radar.

[0019] Preferably, in the step S3, according to the original detection interval of the radar in the range direction, determine the range bin number of the surface layer, and the mathematical expression of the range bin number is:

[0020]

[0021] where, Rangebin Surf represents the range bin number of the surface layer, T_receive represents the first radar signal reception time in the range direction, T_send represents the first radar signal transmission time in the range direction, c represents the speed of light, dl represents the original detection interval of the radar in the range direction; fix represents the rounding function;

[0022] The range bin number takes an integer;

[0023] The radar echo reflectivity factor distribution in the range direction, the mathematical expression is:

[0024]

[0025] where, P r represents the rain-measuring radar received echo power, a represents a constant term, which is determined by parameters such as radar parameters and complex refractive index, P t represents the rain-measuring radar transmitted power, r represents the distance between the radar and the sampling point, and Z represents the radar echo reflectivity factor.

[0026] Preferably, in the step S4, the local zenith angle of the ground sampling point has the following mathematical expression:

[0027]

[0028] where θ represents the local zenith angle of the ground sampling point of the rain-measuring radar, θ d represents the detection angle of the rain-measuring radar, H represents the satellite altitude, and R e represents the radius of the earth.

[0029] Preferably, in the step S5, the sampling interval in the vertical direction is subjected to inverse distance weighted interpolation to obtain the radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction, that is, the conversion of the radar echo reflectivity factor from the distance direction, that is, the number of layers corresponding to the range bins, to the vertical direction, that is, the height corresponding to the number of layers, has the following mathematical expression:

[0030]

[0031] where represents the radar echo reflectivity factor at the height corresponding to the Nth sampling interval in the vertical direction after inverse distance weighted interpolation when the Mth range bin in the distance direction of the ground sampling point is converted to the vertical direction, Z M represents the radar echo reflectivity factor of the Mth range bin in the distance direction of the ground sampling point, Z M+1 represents the radar echo reflectivity factor of the (M + 1)th range bin in the distance direction of the ground sampling point, Δl M represents the difference between the height corresponding to the Nth sampling interval in the vertical direction when the Mth range bin in the distance direction is converted to the vertical direction, Δl M+1 represents the difference between the height corresponding to the Nth sampling interval in the vertical direction when the (M + 1)th range bin is converted to the vertical direction; where M and N are both constants;

[0032] The value of the sampling interval is 50 m.

[0033] According to a conversion system of the detection signal of a spaceborne rain-measuring radar in a three-dimensional coordinate system provided by the present invention, it includes:

[0034] Module M1: Collect and obtain the satellite parameters and the radar detection beam view vector at the detection moment of the rain-measuring radar based on the satellite parameters and the radar parameters;

[0035] Module M2: Calculate the position information of the radar detection ground sampling point based on the satellite parameters at the detection moment of the rain-measuring radar according to the intersection point of the radar detection beam view vector and the earth's surface;

[0036] Module M3: Calculate the position of the first echo of the radar from the ground surface in the range direction, and then determine the range bin number of the surface layer; Based on the position information, calculate and obtain the radar echo reflectivity factor distribution in the range direction;

[0037] Module M4: Based on the position information and the satellite position, calculate the local zenith angle of the ground sampling point, and then based on the local zenith angle and the radar echo reflectivity factor distribution in the range direction, calculate and obtain the radar echo reflectivity factor distribution at the corresponding height in the vertical direction;

[0038] Module M5: Based on the radar echo reflectivity factor distribution at the corresponding height in the vertical direction, obtain the radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction.

[0039] Preferably, in the M1, the satellite parameters include: satellite position, satellite velocity and satellite attitude; The radar parameters include: radar scanning angle, number of radar scanning wave positions and radar echo power;

[0040] The radar is a rain-measuring radar.

[0041] Preferably, in the module M3, according to the original detection interval of the radar in the range direction, determine the range bin number of the surface layer, and the mathematical expression of the range bin number is:

[0042]

[0043] where, Rangebin Surf represents the range bin number of the surface layer, T_receive represents the first radar signal reception time in the range direction, T_send represents the first radar signal transmission time in the range direction, c represents the speed of light, dl represents the original detection interval of the radar in the range direction; fix represents the integer function;

[0044] The range bin number takes an integer;

[0045] The radar echo reflectivity factor distribution in the range direction, the mathematical expression is:

[0046]

[0047] where, P r represents the rain-measuring radar received echo power, a represents a constant term, which is determined by parameters such as radar parameters and complex refractive index, P t represents the rain-measuring radar transmitted power, r represents the distance between the radar and the sampling point, and Z represents the radar echo reflectivity factor.

[0048] Preferably, in the module M4, the local zenith angle of the ground sampling point has the following mathematical expression:

[0049]

[0050] where θ represents the local zenith angle of the ground sampling point of the rain-measuring radar, θ d represents the detection angle of the rain-measuring radar, H represents the satellite altitude, and R e represents the radius of the earth.

[0051] Preferably, in the module M5, the sampling interval in the vertical direction is subjected to inverse distance weighting interpolation to obtain the radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction, that is, the conversion of the radar echo reflectivity factor in the range direction, that is, the number of layers corresponding to the range bins, to the vertical direction, that is, the height corresponding to the number of layers, has the following mathematical expression:

[0052]

[0053] where represents the radar echo reflectivity factor at the height corresponding to the Nth sampling interval in the vertical direction after inverse distance weighting interpolation when the Mth range bin in the range direction of the ground sampling point is converted to the vertical direction, Z M represents the radar echo reflectivity factor of the Mth range bin in the range direction of the ground sampling point, Z M+1 represents the radar echo reflectivity factor of the (M + 1)th range bin in the range direction of the ground sampling point, Δl M represents the difference between the height corresponding to the Nth sampling interval in the vertical direction when the Mth range bin in the range direction is converted to the vertical direction, Δl M+1 represents the difference between the height corresponding to the Nth sampling interval in the vertical direction when the (M + 1)th range bin is converted to the vertical direction; where M and N are both constants;

[0054] The value of the sampling interval is 50 m.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. The present invention realizes the conversion of the detection signal of the spaceborne microwave rain-measuring radar, that is, the radar echo reflectivity factor in the range direction, that is, the number of layers corresponding to the range bins, to the vertical direction, that is, the height corresponding to the number of layers, and obtains the distribution characteristics of the detection signal of the rain-measuring radar in the three-dimensional space.

[0057] 2. The present invention can be used in the research field of the processing of the detection signal of the spaceborne rain-measuring radar and is an effective and important technical means for obtaining the three-dimensional space distribution characteristics of the detection signal of the rain-measuring radar.

[0058] 3. In the present invention, the position information of the ground sampling points is determined according to the intersection points of the detection beam visual vectors of the rain-measuring radar and the earth's surface, and the three-dimensional distribution of the radar echo power is determined according to the original sampling interval in the distance direction. This can retain the original information characteristics to the greatest extent, and perform the conversion from the distance direction at each sampling point, that is, the number of layers corresponding to the range bins, to the vertical direction, that is, the height corresponding to the number of layers, which can improve the blurring phenomenon of detection details caused by the loss of radar detection signals during the resampling process.

[0059] 4. The present invention ensures the processing data accuracy of the rain-measuring radar detection signals in three-dimensional space, and provides effective technical support and data support for the detection of the three-dimensional structural characteristics of cloud precipitation by spaceborne rain-measuring radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] By reading the following detailed description of the non-restrictive embodiments with reference to the accompanying drawings, other features, objects, and advantages of the present invention will become more apparent:

[0061] Figure 1 It is a schematic flowchart of the working method provided by the present invention;

[0062] Figure 2 It is a schematic diagram of the ground sampling process of the rain-measuring radar provided by the present invention;

[0063] Figure 3 It is a schematic diagram of the conversion of the rain-measuring radar detection signal from the distance direction, that is, the number of layers corresponding to the range bins, to the vertical direction, that is, the height corresponding to the number of layers, provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0064] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those of ordinary skill in the art can make several changes and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0065] In the existing methods for processing rain-measuring radar detection data, new three-dimensional grids are mostly established manually, and resampling is performed separately on the earth's surface and in the vertical direction. The original detection signals are averaged to a certain extent, resulting in the loss of detection information and weakening the ability of the rain-measuring radar to depict the detailed characteristics of the cloud precipitation system. There are also technical solutions that use the radar detection signals in the distance direction to supplement the three-dimensional space distribution, resulting in unclear physical meanings of the parameters and being inconvenient for direct use in scientific calculations and research work. The present invention fills the gap in the above-mentioned existing technologies.

[0066] A method and system for converting the detection signal of a spaceborne microwave rain radar in a three-dimensional coordinate system according to the present invention ensure the accuracy of the processed data of the detection signal of the rain radar in three-dimensional space, providing effective technical support and data support for detecting the three-dimensional structural characteristics of cloud precipitation by the spaceborne rain radar.

[0067] The present invention is used in the research field of processing the detection signal of a spaceborne rain radar and is an effective and important technical means for obtaining the three-dimensional spatial distribution characteristics of the detection signal of the rain radar.

[0068] Specifically, the present invention provides a method and system for converting the detection signal of a spaceborne microwave rain radar in a three-dimensional coordinate system, including obtaining parameters such as the satellite position, velocity, and attitude through the working state of the satellite platform, obtaining parameters such as the radar scanning angle, the number of radar scanning wave positions, and the radar echo power through the working state of the rain radar, calculating the satellite position, velocity, attitude, and the radar detection beam view vector at the detection moment of the rain radar; extracting the effective detection signal from the original radar echo power; calculating the position information of the radar detection ground sampling point according to the intersection point of the radar detection beam view vector and the earth's surface; calculating the position of the first echo in the range direction of the rain radar from the ground surface and determining the range bin number of the surface layer; calculating the radar echo reflectivity factor distribution in the range direction according to the radar meteorological equation; calculating the local zenith angle of the ground sampling point according to the ground sampling point and the position of the satellite in the WGS84 coordinate system; calculating the radar echo reflectivity factor distribution at the corresponding height in the vertical direction of the ground sampling point according to the distribution of the radar echo reflectivity factor in the range direction and the local zenith angle; performing inverse distance weighted interpolation on the radar echo reflectivity factor in the vertical direction to obtain the radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction;

[0069] A method for converting the detection signal of a spaceborne microwave rain radar in a three-dimensional coordinate system according to the present invention, as Figure 1 shown, includes the following steps:

[0070] Step S1: Obtain parameters such as the satellite position, velocity, and attitude through the working state of the satellite platform, obtain the radar scanning angle, the number of radar scanning wave positions, and the radar echo power through the working state of the rain radar, and calculate the satellite position, velocity, attitude, and the radar detection beam view vector at the detection moment of the rain radar;

[0071] Specifically, the working states of the satellite platform and the rain-measuring radar can be obtained from the payload remote sensing data packet, including parameters such as satellite speed, satellite position, and satellite attitude, and parameters such as radar scanning angle, number of radar scanning wave positions, and radar echo power. When the rain-measuring radar scans the ground, the initial detection visual axis of the radar is converted to the detection wave position visual axis through a transformation matrix to obtain the detection wave position visual vector; by interpolating the satellite speed, satellite position, and satellite attitude over multiple periods, the satellite position, satellite speed, and satellite attitude at the radar detection moment are obtained.

[0072] Specifically, the purpose of interpolating the satellite speed, satellite position, and satellite attitude over multiple periods is that for the same scanning period, there are multiple radar ground observation moments. By interpolating the satellite speed, position, and attitude over multiple scanning periods, the satellite state at each radar ground detection moment can be obtained, and subsequent step calculations can then be performed.

[0073] Step S2: Extract the effective detection signal from the original radar echo power; the effective detection signal is obtained by removing the invalid signals from the original radar echo power; only the effective detection signal is processed in the subsequent steps, reducing invalid operations and improving the efficiency of the algorithm.

[0074] Specifically, at each detection wave position within the detection period, there is a fixed number of layers of radar echo power distribution in the range direction. The non-zero values in the radar echo power are identified as effective detection signals, and the remaining values are set to default values and not processed in the subsequent steps.

[0075] Step S3: Calculate the position information of the radar detection ground sampling point according to the intersection point of the detection beam visual vector of the rain-measuring radar and the Earth's surface;

[0076] Specifically, using the satellite position, speed, and attitude at the radar detection moment, combined with the detection beam visual vector, calculate the intersection point of the beam visual vector and the Earth's surface at the rain-measuring radar detection moment, and obtain the position information of the ground sampling point.

[0077] Step S4: Calculate the position of the first echo from the rain-measuring radar in the range direction from the ground surface, and determine the range bin number of the surface layer; the range bin number is translated from the English "rangebin", and rangebin is the range bin; number the range bin to obtain the range bin number.

[0078] Specifically, use the time difference between the first radar signal transmission and reception in the range direction of the rain-measuring radar to calculate the position of the first radar echo from the ground surface. According to the original detection interval of the rain-measuring radar in the range direction, determine the range bin number of the surface layer. The calculation formula is as follows:

[0079]

[0080] Among them, Rangebin Surf represents the range bin number of the surface layer. T_receive represents the first radar signal reception time in the range direction, T_send represents the first radar signal transmission time in the range direction, c represents the speed of light, and dl represents the original detection interval in the radar range direction. Round the result to obtain the range bin number of the surface layer; fix represents the rounding function.

[0081] Step S5: Calculate the radar echo reflectivity factor distribution in the range direction according to the radar meteorological equation;

[0082] Specifically, use the position information of the ground sampling points of the rain gauge radar, the radar echo power distribution in the range direction, etc., and calculate the radar echo reflectivity factor distribution in the range direction according to the radar meteorological equation. The calculation formula is as follows:

[0083]

[0084] Among them, P r represents the received echo power of the rain gauge radar. a represents a constant term, which is determined by parameters such as radar parameters and complex refractive index. P t represents the transmitted power of the rain gauge radar, r represents the distance between the radar and the sampling point, and Z represents the radar echo reflectivity factor.

[0085] Step S6: Calculate the local zenith angle of the ground sampling point according to the positions of the ground sampling point and the satellite in the WGS84 coordinate system.

[0086] Specifically, use the positions of the satellite and the ground sampling point at the detection moment in the WGS84 coordinate system, and use the sine theorem to calculate the local zenith angle of the ground sampling point. The calculation formula is as follows:

[0087]

[0088] Among them, θ represents the local zenith angle of the ground sampling point of the rain gauge radar, θ d represents the detection angle of the rain gauge radar, H represents the satellite altitude, and R e represents the radius of the earth.

[0089] Step S7: Calculate the radar echo reflectivity factor distribution at the corresponding height in the vertical direction of the ground sampling point according to the distribution of the radar echo reflectivity factor in the range direction and the local zenith angle.

[0090] Specifically, using the distribution of the radar echo reflectivity factor in the range direction, and projecting it using the local zenith angle of the corresponding sampling point, the range direction distribution is converted into a vertical direction distribution, and the radar echo reflectivity factor distribution at the corresponding height in the vertical direction for the ground sampling point is calculated. For the ground sampling point, in the three-dimensional coordinates of its detection signal, that is, the radar echo reflectivity factor, the first two dimensions represent the position on the Earth's surface, and the third dimension represents its distribution in space, converted from the number of layers corresponding in the range direction to the height corresponding in the vertical direction. The calculation formula is as follows:

[0091] h M =(Rangebin Surf -Rangebin M )×dl×cosθ

[0092] Where h M represents the height in the vertical direction corresponding to the Mth range bin in the range direction of the ground sampling point, Rangebin Surf represents the range bin number of the surface layer, Rangebin M represents the range bin number of the Mth layer, dl represents the original detection interval in the radar range direction, and θ represents the local zenith angle of the ground sampling point.

[0093] Step S8: The radar echo reflectivity factor in the vertical direction is interpolated with inverse distance weighting according to the sampling interval in the vertical direction to obtain the radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction, realizing the conversion of the spaceborne rain radar detection signal, that is, the radar echo reflectivity factor, from the range direction, that is, the number of layers corresponding to the range bin, to the vertical direction, that is, the height corresponding to the number of layers. The calculation formula is as follows:

[0094]

[0095] Where represents the radar echo reflectivity factor at the height corresponding to the Nth sampling interval in the vertical direction after inverse distance weighting interpolation for the Mth range bin in the range direction of the ground sampling point, Z M represents the radar echo reflectivity factor of the Mth range bin in the range direction of the ground sampling point, Z M+1 represents the radar echo reflectivity factor of the (M + 1)th range bin in the range direction of the ground sampling point, Δl M represents the difference between the height corresponding to the Nth sampling interval in the vertical direction after conversion from the Mth range bin in the range direction, Δl M+1 represents the difference between the height corresponding to the Nth sampling interval in the vertical direction after conversion from the (M + 1)th range bin.

[0096] Specifically, inverse distance weighted interpolation is performed according to the sampling interval in the vertical direction. The reason is that according to the original distribution of the radar in the range direction, if it is converted to the vertical direction, the information in the original signal should be retained to the greatest extent. Therefore, by interpolating the original signal according to the inverse distance weighted method and using the position distance as the weight for signal conversion, the conversion result can be made more accurate.

[0097] Further, in conjunction with Appendix Figures 1 to 3 , the method for converting the detection signal of the spaceborne microwave rain radar of the present invention in a three-dimensional coordinate system is specifically described as follows:

[0098] Obtain parameters such as the satellite position, velocity, and attitude through the working state of the satellite platform, and obtain parameters such as the radar scanning angle, the number of radar scanning wave positions, and the radar echo power through the working state of the rain radar. Calculate the satellite position, velocity, attitude, and the radar detection beam viewing vector at the detection moment of the rain radar. The working state of the satellite platform and the working state of the rain radar can be obtained from the payload remote sensing data packet, including parameters such as satellite velocity, satellite position, and satellite attitude, and parameters such as radar scanning angle, the number of radar scanning wave positions, and radar echo power. When the rain radar scans the ground, the initial detection axis of the radar is converted to the detection wave position axis through a transformation matrix to obtain the detection wave position viewing vector; by interpolating the satellite velocity, satellite position, and satellite attitude for multiple periods, the satellite position, velocity, and attitude at the radar detection moment are obtained.

[0099] Extract the effective detection signal from the original radar echo power. At each detection wave position within the detection period, there is a fixed number of layers of radar echo power distribution in the range direction. The non-zero values in the radar echo power are identified as effective detection signals, and the remaining values are set as default values and not processed in subsequent steps.

[0100] Calculate the position information of the radar detection ground sampling point according to the intersection of the radar detection beam viewing vector and the Earth's surface. Utilize the satellite position, velocity, and attitude at the radar detection moment, in combination with the detection beam viewing vector. Calculate the intersection of the beam viewing vector at the radar detection moment and the Earth's surface, and obtain the position information of the ground sampling point.

[0101] Calculate the position of the first echo from the rain radar to the ground in the range direction and determine the range bin number of the surface layer. Utilize the time difference between the first radar signal transmission and reception of the rain radar in the range direction to calculate the position of the first radar echo from the ground. According to the original detection interval of the rain radar in the range direction, determine the range bin number of the surface layer. The calculation formula is as follows:

[0102]

[0103] Where RangebinSurf It represents the distance bin number of the surface layer. T_receive represents the first radar signal reception time in the distance direction, T_send represents the first radar signal transmission time in the distance direction, c represents the speed of light, and dl represents the original detection interval in the radar distance direction. Round the result to obtain the distance bin number of the surface layer. The distribution of the detection signals of the rain gauge radar in the distance direction is as Figure 2 shown.

[0104] According to the radar meteorological equation, calculate the distribution of the radar echo reflectivity factor in the distance direction. Using the position information of the ground sampling points of the rain gauge radar, the radar echo power distribution in the distance direction, etc., according to the radar meteorological equation, calculate the distribution of the radar echo reflectivity factor in the distance direction. The calculation formula is as follows:

[0105]

[0106] where, P r represents the received echo power of the rain gauge radar, a represents a constant term, which is determined by parameters such as radar parameters and complex refractive index, P t represents the transmitted power of the rain gauge radar, r represents the distance between the radar and the sampling point, and Z represents the radar echo reflectivity factor.

[0107] According to the positions of the ground sampling points and the satellite in the WGS84 coordinate system, calculate the local zenith angle of the ground sampling points. Using the positions of the satellite and the ground sampling points of the rain gauge radar at the detection moment in the WGS84 coordinate system, and using the sine theorem, calculate the local zenith angle of the ground sampling points. The calculation formula is as follows:

[0108]

[0109] where, θ represents the local zenith angle of the ground sampling points of the rain gauge radar, θ d represents the detection angle of the rain gauge radar, H represents the satellite altitude, and R e represents the radius of the earth. The distance and angle relationship between the satellite and the ground sampling points of the rain gauge radar is as Figure 3 shown.

[0110] Calculate the radar echo reflectivity factor distribution at the corresponding height in the vertical direction for the ground sampling points based on the distribution of the radar echo reflectivity factor in the range direction and the local zenith angle. Using the distribution of the radar echo reflectivity factor in the range direction, project it using the local zenith angle of the corresponding sampling point to convert the range direction distribution to the vertical direction distribution, and calculate the radar echo reflectivity factor distribution at the corresponding height in the vertical direction for the ground sampling points. For the ground sampling points, in the three-dimensional coordinates of its detection signal, that is, the radar echo reflectivity factor, the first two dimensions represent the position on the Earth's surface, and the third dimension represents its distribution in space. It is converted from the number of layers corresponding in the range direction to the height corresponding in the vertical direction. The calculation formula is as follows:

[0111] h M =(Rangebin Surf -Rangebin M )×dl×cosθ

[0112] Where h M represents the height in the vertical direction corresponding to the Mth range bin in the range direction for the ground sampling points, Rangebin Surf represents the range bin number of the surface layer, Rangebin M represents the range bin number of the Mth layer, dl represents the original detection interval in the radar range direction, and θ represents the local zenith angle of the ground sampling points. The corresponding relationship between the range bin number in the range direction of the rain measuring radar and the height in the vertical direction is as Figure 2 shown.

[0113] For the radar echo reflectivity factor in the vertical direction, perform inverse distance weighted interpolation according to the sampling interval in the vertical direction to obtain the radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction, realizing the conversion of the detection signal of the spaceborne rain measuring radar, that is, the radar echo reflectivity factor, from the range direction, that is, the number of layers corresponding to the range bins, to the vertical direction, that is, the height corresponding to the layers. The calculation formula is as follows:

[0114]

[0115] Where represents the radar echo reflectivity factor at the height corresponding to the Nth sampling interval in the vertical direction after inverse distance weighted interpolation when the Mth range bin in the range direction of the ground sampling points is converted to the vertical direction, Z M represents the radar echo reflectivity factor of the Mth range bin in the range direction of the ground sampling points, Z M+1 represents the radar echo reflectivity factor of the (M + 1)th range bin in the range direction of the ground sampling points, Δl M represents the difference between the height corresponding to the Nth sampling interval in the vertical direction when the Mth range bin in the range direction is converted to the vertical direction, ΔlM+1 It represents the difference between the height corresponding to the vertical direction of the conversion of the (M + 1)-th range bin and the N-th sampling interval; where both M and N are constants.

[0116] The present invention also provides a conversion system for on-board microwave rain radar detection signals in a three-dimensional coordinate system. The conversion system for on-board microwave rain radar detection signals in a three-dimensional coordinate system can be implemented by executing the process steps of the conversion method for on-board microwave rain radar detection signals in a three-dimensional coordinate system. That is, those skilled in the art can understand the conversion method for on-board microwave rain radar detection signals in a three-dimensional coordinate system as a preferred implementation manner of the conversion system for on-board microwave rain radar detection signals in a three-dimensional coordinate system.

[0117] According to the conversion system for on-board microwave rain radar detection signals in a three-dimensional coordinate system provided by the present invention, it includes:

[0118] Module M1: Obtain parameters such as the satellite position, velocity, and attitude through the working state of the satellite platform, and obtain parameters such as the radar scanning angle, the number of radar scanning wave positions, and the radar echo power through the working state of the rain radar. Calculate the satellite position, velocity, attitude, and the radar detection beam view vector at the detection moment of the rain radar. The working state of the satellite platform and the working state of the rain radar can be obtained from the payload remote sensing data packet, including parameters such as the satellite velocity, satellite position, and satellite attitude, and parameters such as the radar scanning angle, the number of radar scanning wave positions, and the radar echo power. When the rain radar scans the ground, the initial detection visual axis of the radar is converted to the detection wave position visual axis through a conversion matrix to obtain the detection wave position view vector; the satellite position, velocity, and attitude at the radar detection moment are obtained by interpolating the satellite velocity, satellite position, and satellite attitude of multiple periods.

[0119] Module M2: Extract the effective detection signals from the original radar echo power. At each detection wave position within the detection period, there is a fixed number of layers of radar echo power distribution in the range direction. The non-zero values in the radar echo power are identified as effective detection signals, and the remaining values are set as default values and not processed in subsequent steps.

[0120] Module M3: Calculate the position information of the radar detection ground sampling points according to the intersection point of the radar detection beam view vector and the earth's surface. Utilize the satellite position, velocity, and attitude at the radar detection moment, combined with the detection beam view vector. Calculate the intersection point of the beam view vector and the earth's surface at the radar detection moment, and obtain the position information of the ground sampling points.

[0121] Module M4: Calculate the position of the first echo from the rain gauge radar in the range direction relative to the ground surface and determine the range bin number of the surface layer. Calculate the position of the first radar echo from the ground surface using the time difference between the first radar signal transmission and reception in the range direction of the rain gauge radar. Determine the range bin number of the surface layer according to the original detection interval of the rain gauge radar in the range direction. The calculation formula is as follows:

[0122]

[0123] where Rangebin Surf represents the range bin number of the surface layer, T_receive represents the reception time of the first radar signal in the range direction, T_send represents the transmission time of the first radar signal in the range direction, c represents the speed of light, and dl represents the original detection interval of the radar in the range direction. Round the result to obtain the range bin number of the surface layer.

[0124] Module M5: Calculate the radar echo reflectivity factor distribution in the range direction according to the radar meteorological equation. Use the position information of the ground sampling points of the rain gauge radar, the radar echo power distribution in the range direction, etc., and calculate the radar echo reflectivity factor distribution in the range direction according to the radar meteorological equation. The calculation formula is as follows:

[0125]

[0126] where P r represents the received echo power of the rain gauge radar, a represents a constant term determined by parameters such as radar parameters and complex refractive index, P t represents the transmitted power of the rain gauge radar, r represents the distance between the radar and the sampling point, and Z represents the radar echo reflectivity factor.

[0127] Module M6: Calculate the local zenith angle of the ground sampling point according to the positions of the ground sampling point and the satellite in the WGS84 coordinate system. Use the positions of the satellite and the ground sampling point at the detection moment in the WGS84 coordinate system and use the sine theorem to calculate the local zenith angle of the ground sampling point. The calculation formula is as follows:

[0128]

[0129] where θ represents the local zenith angle of the ground sampling point of the rain gauge radar, θ d represents the detection angle of the rain gauge radar, H represents the satellite altitude, and R e represents the radius of the earth.

[0130] Module M7: Calculate the distribution of the radar echo reflectivity factor at the corresponding height in the vertical direction for the ground sampling points based on the distribution of the radar echo reflectivity factor in the range direction and the local zenith angle. Using the distribution of the radar echo reflectivity factor in the range direction, project it using the local zenith angle of the corresponding sampling point to convert the range direction distribution to the vertical direction distribution, and calculate the distribution of the radar echo reflectivity factor at the corresponding height in the vertical direction for the ground sampling points. For the ground sampling points, in the three-dimensional coordinates of their detection signals (radar echo reflectivity factor), the first two dimensions represent the positions on the Earth's surface, and the third dimension represents its distribution in space. Convert from the number of layers corresponding in the range direction to the height corresponding in the vertical direction. The calculation formula is as follows:

[0131] h M =(Rangebin Surf -Rangebin M )×dl×cosθ

[0132] where h M represents the height in the vertical direction corresponding to the M-th range bin in the range direction for the ground sampling points. Rangebin Surf represents the range bin number of the surface layer. Rangebin M represents the range bin number of the M-th layer. dl represents the original detection interval in the radar range direction, and θ represents the local zenith angle of the ground sampling points.

[0133] Module M8: For the radar echo reflectivity factor in the vertical direction, perform inverse distance weighted interpolation according to the sampling interval in the vertical direction to obtain the distribution of the radar echo reflectivity factor with a fixed sampling interval in the vertical direction, realizing the conversion of the spaceborne rain radar detection signal, that is, the radar echo reflectivity factor from the range direction, that is, the number of layers corresponding to the range bins, to the vertical direction, that is, the height corresponding to the layers. The calculation formula is as follows:

[0134]

[0135] where represents the radar echo reflectivity factor at the height corresponding to the N-th sampling interval in the vertical direction after inverse distance weighted interpolation when the M-th range bin in the range direction for the ground sampling points is converted to the vertical direction. Z M represents the radar echo reflectivity factor of the M-th range bin in the range direction for the ground sampling points. Z M+1 represents the radar echo reflectivity factor of the (M + 1)-th range bin in the range direction for the ground sampling points. Δl M represents the difference between the height corresponding to the conversion of the M-th range bin in the range direction to the vertical direction and the height corresponding to the N-th sampling interval. Δl M+1It represents the difference in height corresponding to the vertical direction of the (M + 1)-th range bin and the N-th sampling interval, where both M and N are constants.

[0136] According to a computer-readable storage medium storing a computer program provided by the present invention, when the computer program is executed by a processor, it implements the steps of the method for converting the on-board microwave rain radar detection signal in a three-dimensional coordinate system.

[0137] According to an electronic device provided by the present invention, it includes a memory, a processor, and a computer program stored on the memory and executable on the processor. When the computer program is executed by the processor, it implements the steps of the method for converting the on-board microwave rain radar detection signal in a three-dimensional coordinate system.

[0138] The present invention also provides a conversion system for the on-board rain radar detection signal in a three-dimensional coordinate system. The conversion system for the on-board rain radar detection signal in a three-dimensional coordinate system can be implemented by executing the process steps of the method for converting the on-board rain radar detection signal in a three-dimensional coordinate system. That is, those skilled in the art can understand the method for converting the on-board rain radar detection signal in a three-dimensional coordinate system as a preferred implementation manner of the conversion system for the on-board rain radar detection signal in a three-dimensional coordinate system.

[0139] According to a conversion system for the on-board rain radar detection signal in a three-dimensional coordinate system provided by the present invention, it includes:

[0140] Module M1: Collect and calculate, based on satellite parameters and radar parameters, the satellite position, satellite velocity, satellite attitude, and radar detection beam view vector at the detection moment of the rain radar.

[0141] Module M2: Based on the satellite position, satellite velocity, and satellite attitude at the detection moment of the rain radar, calculate the position information of the radar detection ground sampling point according to the intersection point of the radar detection beam view vector and the Earth's surface.

[0142] Module M3: Calculate the position of the first echo from the radar in the range direction above the ground surface, and then determine the range bin number of the surface layer. Based on the position information, calculate and obtain the radar echo reflectivity factor distribution in the range direction.

[0143] Module M4: Based on the position information and the satellite position, calculate the local zenith angle of the ground sampling point, and then based on the local zenith angle and the radar echo reflectivity factor distribution in the range direction, calculate and obtain the radar echo reflectivity factor distribution at the corresponding height in the vertical direction.

[0144] Module M5: Based on the radar echo reflectivity factor distribution corresponding to the height in the vertical direction, obtain the radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction.

[0145] Those skilled in the art know that in addition to implementing the system and its various devices, modules, and units provided by the present invention in the form of pure computer-readable program code, the method steps can be logically programmed to enable the system and its various devices, modules, and units provided by the present invention to be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers, etc. to achieve the same functions. Therefore, the system and its various devices, modules, and units provided by the present invention can be regarded as a kind of hardware component, and the devices, modules, and units included therein for implementing various functions can also be regarded as the structures within the hardware component; the devices, modules, and units for implementing various functions can also be regarded as either software modules for implementing the method or structures within the hardware component.

[0146] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. Without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A method for converting the detection signal of a spaceborne rain radar in a three-dimensional coordinate system, characterized in that, Including: Step S1: Collect and obtain the satellite parameters and the radar detection beam view vector at the detection moment of the rain gauge radar based on the satellite parameters and the radar parameters; Step S2: Based on the satellite parameters at the detection moment of the rain gauge radar, calculate the position information of the ground sampling points of the radar detection according to the intersection point of the radar detection beam view vector and the Earth's surface; Step S3: Calculate the position of the first echo of the radar from the ground in the range direction, and then determine the range bin number of the surface layer; Based on the position information, calculate and obtain the radar echo reflectivity factor distribution in the range direction; Step S4: Based on the position information and the satellite position, calculate the local zenith angle of the ground sampling point, and then based on the local zenith angle and the radar echo reflectivity factor distribution in the range direction, calculate and obtain the radar echo reflectivity factor distribution at the corresponding height in the vertical direction; Step S5: Based on the radar echo reflectivity factor distribution at the corresponding height in the vertical direction, obtain the radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction.

2. The conversion method of the spaceborne rain radar detection signal in a three-dimensional coordinate system according to claim 1, characterized in that In the step S1, the satellite parameters include: satellite position, satellite velocity, and satellite attitude; the radar parameters include: radar scanning angle, number of radar scanning wave positions, and radar echo power; Judging one by one whether the radar echo power is a non-zero value. If the result is yes, let the non-zero value be the effective detection signal of the radar echo power; if the result is no, set it to the default value and do not process it.

3. The conversion method of the detection signal of the spaceborne rain radar in a three-dimensional coordinate system according to claim 2, characterized in that, In the step S3, according to the original detection interval of the radar in the range direction, determine the range bin number of the surface layer. The mathematical expression of the range bin number is: Among them, Rangebin Surf represents the range bin number of the surface layer. T_receive represents the reception time of the first radar signal in the range direction. T_send represents the transmission time of the first radar signal in the range direction. c represents the speed of light. dl represents the original detection interval in the radar range direction. fix represents the rounding function; The range bin number takes an integer; The mathematical expression of the radar echo reflectivity factor distribution in the range direction is: Among them, P r represents the received echo power of the rain gauge radar, a represents the constant term, which is determined by parameters such as radar parameters and complex refractive index, P t represents the transmitted power of the rain gauge radar, r represents the distance between the radar and the sampling point, and Z represents the radar echo reflectivity factor.

4. The method for converting the detection signal of the spaceborne rain radar in a three-dimensional coordinate system according to claim 3, wherein, In the step S4, the mathematical expression of the local zenith angle of the ground sampling point is: where θ represents the local zenith angle of the ground sampling point of the rain gauge radar, θ d represents the detection angle of the rain gauge radar, H represents the satellite altitude, and R e represents the radius of the Earth.

5. The method for converting the detection signal of the spaceborne rain radar in a three-dimensional coordinate system according to claim 4, characterized in that, In the step S5, for the sampling interval in the vertical direction, perform inverse distance weighted interpolation to obtain the radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction, that is, realize the conversion of the radar echo reflectivity factor from the range direction, that is, the number of layers corresponding to the range bins, to the vertical direction, that is, the height corresponding to the number of layers. The mathematical expression is: Among them, represents the radar echo reflectivity factor Z at the height corresponding to the Nth sampling interval in the vertical direction after inverse distance weighted interpolation when the Mth range bin in the distance direction of the ground sampling point is converted to the vertical direction; M represents the radar echo reflectivity factor Z of the Mth range bin in the distance direction of the ground sampling point; M+1 represents the radar echo reflectivity factor of the (M + 1)th range bin in the distance direction of the ground sampling point, Δl; M represents the difference in height between the height corresponding to the Nth sampling interval when the Mth range bin in the distance direction is converted to the vertical direction, Δl; M+1 represents the difference in height between the height corresponding to the Nth sampling interval when the (M + 1)th range bin is converted to the vertical direction; where both M and N are constants. The value of the sampling interval is 50m.

6. A conversion system for on-orbit rain radar detection signals in a three-dimensional coordinate system, characterized in that, Including: Module M1: Collect and obtain the satellite parameters and the radar detection beam view vector at the detection moment of the rain gauge radar based on the satellite parameters and the radar parameters; Module M2: Based on the satellite parameters at the detection moment of the rain gauge radar, calculate the position information of the ground sampling points of the radar detection according to the intersection point of the radar detection beam view vector and the Earth's surface; Module M3: Calculate the position of the first echo of the radar from the ground in the range direction, and then determine the range bin number of the surface layer; Based on the position information, calculate and obtain the radar echo reflectivity factor distribution in the range direction; Module M4: Calculate the local zenith angle of the ground sampling point based on the position information and the satellite position, and then calculate and obtain the radar echo reflectivity factor distribution at the corresponding height in the vertical direction based on the local zenith angle and the radar echo reflectivity factor distribution in the distance direction; Module M5: Obtain the radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction based on the radar echo reflectivity factor distribution at the corresponding height in the vertical direction.

7. The conversion system of the spaceborne rain radar detection signal in the three-dimensional coordinate system according to claim 6, wherein In M1, the satellite positioning information includes: satellite position, satellite velocity, and satellite attitude; the radar parameters include: radar scanning angle, number of radar scanning wave positions, and radar echo power; Judging one by one whether the radar echo power is a non-zero value. If the result is yes, let the non-zero value be the effective detection signal of the radar echo power; if the result is no, set it to the default value and do not process it.

8. The conversion system of the spaceborne rain radar detection signal in a three-dimensional coordinate system according to claim 7, wherein In module M3, determine the distance bin number of the surface layer according to the original detection interval of the radar in the distance direction. The mathematical expression of the distance bin number is: Among them, Rangebin Surf represents the range bin number of the surface layer. T_receive represents the first radar signal reception time in the range direction, T_send represents the first radar signal transmission time in the range direction, c represents the speed of light, dl represents the original detection interval in the radar range direction; fix represents the rounding function; The distance bin number takes an integer; The mathematical expression of the radar echo reflectivity factor distribution in the distance direction is: Among them, P r represents the received echo power of the rain gauge radar, a represents the constant term, which is determined by parameters such as radar parameters and complex refractive index, and P t represents the transmitted power of the rain gauge radar, r represents the distance between the radar and the sampling point, and Z represents the radar echo reflectivity factor.

9. The conversion system of the spaceborne rain radar detection signal in a three-dimensional coordinate system according to claim 8, characterized in that, In module M4, the mathematical expression of the local zenith angle of the ground sampling point is: Among them, θ represents the local zenith angle of the ground sampling point of the rain-measuring radar, and θ d represents the detection angle of the rain-measuring radar, H represents the satellite altitude, and R e represents the radius of the Earth.

10. The conversion system of the spaceborne rain radar detection signal in a three-dimensional coordinate system according to claim 9, characterized in that, In module M5, the sampling interval in the vertical direction is subjected to inverse distance weighting interpolation to obtain the radar echo reflectivity factor distribution with a fixed sampling interval in the vertical direction, that is, the conversion of the radar echo reflectivity factor from the distance direction, that is, the number of layers corresponding to the distance bin, to the vertical direction, that is, the height corresponding to the number of layers, is realized. The mathematical expression is: Among them, represents the radar echo reflectivity factor Z at the height corresponding to the Nth sampling interval in the vertical direction after inverse distance weight interpolation when the Mth range bin in the distance direction of the ground sampling point is converted to the vertical direction; M represents the radar echo reflectivity factor Z of the Mth range bin in the distance direction of the ground sampling point; M+1 represents the radar echo reflectivity factor of the (M + 1)th range bin in the distance direction of the ground sampling point, Δl; M represents the difference in height between the height corresponding to the Nth sampling interval when the Mth range bin in the distance direction is converted to the vertical direction, Δl; M+1 represents the difference in height between the height corresponding to the Nth sampling interval when the (M + 1)th range bin is converted to the vertical direction; where both M and N are constants. The value of the sampling interval is 50m.

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