CN116540273B - GNSS-R mirror reflection point initial value position determination method and device and electronic equipment - Google Patents

GNSS-R mirror reflection point initial value position determination method and device and electronic equipment Download PDF

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CN116540273B
CN116540273B CN202310812830.3A CN202310812830A CN116540273B CN 116540273 B CN116540273 B CN 116540273B CN 202310812830 A CN202310812830 A CN 202310812830A CN 116540273 B CN116540273 B CN 116540273B
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CN116540273A (en
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郭博峰
武翔
李伟强
南阳
张朝怡
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Tianjin University
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    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
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Abstract

A method, a device and electronic equipment for determining the position of an initial value of a GNSS-R mirror reflection point belong to the field of satellite-borne height measurement, and the method comprises the following steps: establishing a sphere model according to a long half shaft of the WGS84 ellipsoid model and a short half shaft of the WGS84 ellipsoid model, wherein the sphere center of the sphere model is the sphere center O of the WGS84 ellipsoid model; determining a first included angle according to the position T, GNSS of the GNSS satellite-R, the position R of the satellite and the sphere center O of the sphere modelValue ofThe method comprises the steps of carrying out a first treatment on the surface of the According to the first included angleValues of (2)And polynomial function to obtain a second included angleValues of (2)The method comprises the steps of carrying out a first treatment on the surface of the The normal line of the surface where the position T of the spherical center O, GNSS satellite and the position R of the GNSS-R satellite are positioned is taken as a rotation axis, and the straight line where the spherical center O and the position T of the GNSS satellite are positioned rotates around one side of the rotation axis of the GNSS-R satelliteThe intersection point of the rotated straight line and the spherical surface of the spherical model is the position S of the initial value of the GNSS-R specular reflection point 0 。

Description

GNSS-R mirror reflection point initial value position determination method and device and electronic equipment
Technical Field
The invention relates to the field of GNSS reflection technology and satellite-borne height measurement, in particular to a method and a device for determining the position of an initial value of a GNSS-R mirror reflection point and electronic equipment.
Background
With the continuous development of the GNSS technology, hundreds of navigation satellites of the global navigation satellite system can provide gratuitous, accurate and rich signal sources for human beings in the next ten years. Based on the excellent characteristics of GNSS signals, global navigation satellite reflection system measurement technology (Global Navigation Satellite System Reflectometry), abbreviated as GNSS-R, has become a research hotspot in recent years. After receiving GNSS satellite signals reflected by the earth surface, the technology can detect sea surface height, sea surface wind field, sea ice and soil humidity through analyzing physical parameters such as waveform, phase, power and the like. The space-borne GNSS-R has great advantages in space-time resolution, and gradually becomes a new earth observation means. In the processing of satellite-borne GNSS-R signals, the specular reflection point is an important reference point. The area around the specular reflection point, called the scintillation area, may be divided according to different time delays and doppler delays around the specular reflection point and form a Delay-doppler Map (DDM) for short. The ocean remote sensing product can be further obtained by processing the DDM, so that the position of the initial value of the specular reflection point is related to the accuracy of the final remote sensing product. Because the calculation resources on the satellite are limited, the position of the initial value of the specular reflection point is calculated quickly and efficiently, and the method has very important significance for saving the operation space and prolonging the service life of the satellite.
Disclosure of Invention
Aiming at the problems, the invention provides a method and a device for determining the position of the initial value of the GNSS-R mirror reflection point and electronic equipment, so as to realize the rapid calculation of the position of the initial value of the GNSS-R mirror reflection point.
As a first aspect of the present invention, there is provided a position determining method of an initial value of a GNSS-R specular reflection point, including:
establishing a sphere model according to a long half shaft of the WGS84 ellipsoid model and a short half shaft of the WGS84 ellipsoid model, wherein the sphere center of the sphere model is the sphere center O of the WGS84 ellipsoid model, the radius of the sphere model is equal to the average value of the long half shaft of the WGS84 ellipsoid model and the short half shaft of the WGS84 ellipsoid model, and the rotation angular velocity of the sphere model is the same as that of the WGS84 ellipsoid model;
determining a first included angle according to the position T, GNSS of the GNSS satellite-R, the position R of the satellite and the sphere center O of the sphere modelValue of->；
According to the first included angleValue of->And a polynomial function to obtain a second angle +.>Values of (2)Wherein S is 0 Representing the position of the initial value of the GNSS-R specular reflection point, S 0 The spherical surface of the spherical model;
the normal line of the surface where the position T of the spherical center O, GNSS satellite and the position R of the GNSS-R satellite are positioned is taken as a rotation axis, and the straight line where the spherical center O and the position T of the GNSS satellite are positioned rotates around one side of the rotation axis of the GNSS-R satelliteThe intersection point of the rotated straight line and the spherical surface of the spherical model is the position S of the initial value of the GNSS-R specular reflection point 0 。
According to an embodiment of the present invention, the polynomial function is expressed as follows:
；
wherein p is 0 、p 1 、p 2 The coefficients of the polynomial are represented by,representing the residual.
According to an embodiment of the present invention, a method for acquiring coefficients of a polynomial includes:
acquiring a sample set comprising a plurality of sets of sample data, each set of sample data comprising a position of a GNSS satelliteAnd (2) and (4) position>Position of corresponding GNSS-R satellite +.>；
From the position of GNSS satellitesAnd (2) and (4) position>Position of corresponding GNSS-R satellite +.>Position of initial value of GNSS-R specular reflection point is obtained +.>；
From the position of GNSS satellitesAnd->Position of corresponding GNSS-R satellite +.>And position of the initial value of the GNSS-R specular reflection point +.>Obtaining a third included angle->Value of->And a fourth included angle->Value of->；
According to the third included angleValue of->And a fourth included angle->Value of->Coefficients of the polynomial are obtained.
According to an embodiment of the present invention, the position of the GNSS satellites is determinedAnd->Position of corresponding GNSS-R satellite +.>Position of initial value of GNSS-R specular reflection point is obtained +.>Comprising the following steps:
based on constraint conditions, according to the position of GNSS satellitesAnd->Position of GNSS-R satellite with corresponding position ∈>Position of initial value of GNSS-R specular reflection point is obtained +.>Wherein, position->And position->Characterizing direct signal vector emitted by GNSS satellite>Position->And position->Representing the reflected signal vector received by the GNSS-R satellite>；
The constraint conditions include: position of initial value of GNSS-R specular reflection pointOn the sphere of the sphere model, the direct signal vector emitted by the GNSS satellite is +.>Reflected signal vector received by GNSS-R satellite>First value position of specular reflection point +.>Normal vector at the position is coplanar, the incident angle is the same as the reflection angle, and the incident angle is direct signal vector +.>A straight line and a straight line with normal vectorIncluded angle, reflection angle is reflection signal vector +.>The included angle between the straight line and the straight line with the normal vector.
According to an embodiment of the invention, the position of the initial value of the GNSS-R specular reflection pointThe positions on the sphere of the sphere model are expressed as follows:
；
wherein x, y, z represent positionA represents the radius of the sphere model;
direct signal vector from GNSS satelliteAnd reflected signal vector received by GNSS-R satellite +.>Position on the spheronization model +.>The normal vector of (2) are coplanar and expressed as follows:
；
wherein t is 1 、t 2 、t 3 Representing the positionCoordinates r of (2) 1 、r 2 、r 3 Representation of the position->Coordinates of (c);
the incident angle of the direct signal sent by the GNSS satellite is the same as the reflected angle of the reflected signal received by the GNSS-R satellite, and the incident angle is expressed as follows:
。
according to an embodiment of the invention, the first angle is determined based on the position T, GNSS of the GNSS satellite-R of the satellite and the spherical center O of the spherical modelValue of->Comprising the following steps:
position vector based on position T of GNSS satellite relative to sphere center O of sphere modelAnd a position vector of the position R of the GNSS-R satellite with respect to the sphere center O of the sphere model +.>Obtain the position vector +.>And position vector->The value of the first included angle between +.>。
According to an embodiment of the present invention, the position of the GNSS satellites is determinedAnd->Position of GNSS-R satellite with corresponding position ∈>And position of the initial value of the GNSS-R specular reflection point +.>Obtaining a third included angle->Value of->And a fourth included angle->Value of->Comprising:
from the position of GNSS satellitesPosition vector relative to the sphere center O of the sphere model +.>Position of GNSS-R satellite>Position vector relative to the sphere center O of the sphere model +.>And position of the initial value of the GNSS-R specular reflection point +.>Position vector relative to the sphere center O of the sphere model +.>Obtain the position vector +.>And position vector->The value of the third included angle between +.>Andposition vector->And position vector->The value of the fourth included angle between +.>。
As a second aspect of the present invention, there is also provided a position determining device for determining an initial value of a GNSS-R specular reflection point, for implementing the above method, the device comprising:
the building module is used for building a sphere model according to a long half shaft A of the WGS84 ellipsoid model and a short half shaft B of the WGS84 ellipsoid model, wherein the sphere center of the sphere model is the sphere center O of the WGS84 ellipsoid model, the radius of the sphere model is equal to the average value of the long half shaft A of the WGS84 ellipsoid model and the short half shaft B of the WGS84 ellipsoid model, and the rotation angular velocity of the sphere model is the same as that of the WGS84 ellipsoid model;
a first obtaining module adapted to determine a first included angle according to the position T, GNSS-R of the GNSS satellite, the position R of the satellite and the sphere center O of the sphere modelValue of->；
A second obtaining module adapted to obtain a first angleValue of->And a polynomial function to obtain a second angle +.>Wherein S is 0 Representing the position of the initial value of the GNSS-R specular reflection point, S 0 Is positioned on the sphere model;
the rotating module is suitable for the spherical center O, GNSThe normal line of the surface where the position T of the S satellite and the position R of the GNSS-R satellite are located is used as a rotation axisRotating a straight line where the spherical center O and the position T of the GNSS satellite are positioned around one side of the GNSS-R satellite in the rotating axial direction, wherein the intersection point of the rotated straight line and the spherical model is the position S of the initial value of the GNSS-R specular reflection point 0 。
As a third aspect of the present invention, there is also provided an electronic apparatus comprising:
one or more processors;
storage means for storing one or more programs,
wherein the one or more programs, when executed by the one or more processors, cause the one or more processors to perform the method described above.
As a fourth aspect of the present invention, there is also provided a computer readable storage medium having stored thereon executable instructions which, when executed by a processor, cause the processor to perform the above-described method.
According to an embodiment of the invention, the position S of the initial value of the GNSS-R specular reflection point, from the position T of the GNSS satellite, the centre of sphere O of the spherical model, and the position T of the GNSS-R specular reflection point is determined by using a polynomial function 0 The value of the second included angleThen, the position S of the initial value of the GNSS-R specular reflection point on the spherical model is determined by rotating the straight line where the spherical center O and the position T of the GNSS satellite are located 0 The position determination method provided by the embodiment of the invention has the advantages that the iteration times are small, and particularly compared with a conventional method (a projection point method), the iteration times in the iteration process are obviously reduced, but the accuracy is the same as that of the conventional method.
Drawings
FIG. 1 is a schematic diagram illustrating a method for determining the initial position of a GNSS-R specular reflection point according to an embodiment of the present invention;
FIG. 2 is a flowchart of a method for determining the initial value of a GNSS-R specular reflection point according to an embodiment of the present invention;
FIG. 3 illustrates the number of iterations of obtaining GNSS-R specular reflection points using different methods provided in accordance with an embodiment of the present invention;
FIG. 4 shows the accuracy of the GNSS-R specular reflection point truth values obtained using the two methods of FIG. 3.
Detailed Description
The present invention will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present invention more apparent.
Fig. 1 is a schematic geometric diagram of a method for determining a position of an initial value of a GNSS-R specular reflection point according to an embodiment of the present invention.
Referring to fig. 1, the method for determining the position of the initial value of the gnss-R specular reflection point includes operations S110-S140.
In operation S110, a sphere model is built according to the long half axis of the WGS84 ellipsoid model and the short half axis of the WGS84 ellipsoid model, the sphere center of the sphere model is the sphere center O of the WGS84 ellipsoid model, the radius of the sphere model is equal to the average value of the long half axis of the WGS84 ellipsoid model and the short half axis of the WGS84 ellipsoid model, and the rotational angular velocity of the sphere model is the same as that of the WGS84 ellipsoid model.
In operation S120, a first included angle is determined according to the position T, GNSS of the GNSS satellite-R of the satellite and the spherical center O of the spherical modelValue of->。
In operation S130, according to the first included angleValue of->And polynomial function to obtain a second included angleValue of->Wherein S is 0 Representing the position of the initial value of the GNSS-R specular reflection point, S 0 Is positioned on the spherical surface of the spherical model.
In operation S140, the line between the spherical center O and the position T of the GNSS satellite is rotated around the rotation axis to one side of the GNSS-R satellite by using the normal line of the plane between the position T of the spherical center O, GNSS satellite and the position R of the GNSS-R satellite as the rotation axisThe intersection point of the rotated straight line and the spherical surface of the spherical model is the position S of the initial value of the GNSS-R specular reflection point 0 。
According to an embodiment of the invention, the value of the second angle obtained from the position T of the GNSS satellite, the sphere center O of the spherical model and the position of the initial value of the GNSS-R specular reflection point is determined by using a polynomial functionThen, the position S of the initial value of the GNSS-R specular reflection point on the spherical model is determined by rotating the straight line where the spherical center O and the position T of the GNSS satellite are located 0 The position determination method provided by the embodiment of the invention has the advantages that the iteration times are small, and particularly compared with a conventional method (a projection point method), the iteration times in the iteration process are obviously reduced, but the accuracy is the same as that of the conventional method.
According to an embodiment of the invention, the radius is selected to beSince the sphere of the sphere model is easier to calculate in the calculation process, and the radius is given by considering the influence of the initial value of the specular reflection point on the iteration numberThe compatibility of the spherical surface of the (E) and the WGS84 ellipsoidal surface is better, and the phenomenon that the iteration times are too many and even can not be converged can not occur.
According to embodiments of the present invention, the choice of the rotational angular velocity for the spherical model and the WGS84 ellipsoidal model is the same without regard to the problem of relative positional variation between the spherical and ellipsoidal surfaces.
According to an embodiment of the invention, the first angle is determined based on the position T, GNSS of the GNSS satellite-R of the satellite and the spherical center O of the spherical modelValue of->Comprising the following steps:
position vector based on position T of GNSS satellite relative to sphere center O of sphere modelAnd a position vector of the position R of the GNSS-R satellite with respect to the sphere center O of the sphere model +.>Obtain the position vector +.>And position vector->The value of the first included angle between +.>。
According to an embodiment of the present invention, the polynomial function is expressed as follows:
（1）
in formula (1), p 0 、p 1 、p 2 The coefficients of the polynomial are represented by,representing the residual.
According to an embodiment of the present invention, the coefficient acquisition method of the polynomial includes operation S210-operation S240.
In operationS210, acquiring a sample set, wherein the sample set comprises a plurality of groups of sample data, and each group of sample data comprises the position of a GNSS satelliteAnd (2) and (4) position>Position of corresponding GNSS-R satellite +.>。
In operation S220, according to the position of the GNSS satelliteAnd (2) and (4) position>Position of corresponding GNSS-R satellite +.>Position of initial value of GNSS-R specular reflection point is obtained +.>。
In operation S230, according to the position of the GNSS satelliteAnd->Position of corresponding GNSS-R satellite +.>And position of the initial value of the GNSS-R specular reflection point +.>Obtaining a third included angle->Value of->And a fourth included angleValue of->。
In operation S240, according to the third included angleValue of->And a fourth included angle->Values of (2)Coefficients of the polynomial are obtained.
According to an embodiment of the present invention, in operation S220, the position of the GNSS satellites is determinedAnd->The position R' of the corresponding GNSS-R satellite obtains the position of the initial value of the GNSS-R specular reflection point +.>Comprising the following steps:
based on constraint conditions, according to the position of GNSS satellitesAnd (2) and (4) position>Position of corresponding GNSS-R satellite +.>Position of initial value of GNSS-R specular reflection point is obtained +.>Wherein, position->And position->Characterizing direct signal vector emitted by GNSS satellite>Position->And position->Representing the reflected signal vector received by the GNSS-R satellite>。
The constraint conditions include: position of initial value of GNSS-R specular reflection pointOn the sphere of the sphere model, the direct signal vector emitted by the GNSS satellite is +.>Reflected signal vector received by GNSS-R satellite>First value position of specular reflection point +.>Normal vector at the position is coplanar, the incident angle is the same as the reflection angle, and the incident angle is direct signal vector +.>The angle between the straight line and the straight line with normal vector is the reflection angle is the reflection signal vector +.>Straight line and normal vectorThe included angle of the straight line.
According to an embodiment of the invention, the position of the initial value of the GNSS-R specular reflection pointThe positions on the sphere of the sphere model are expressed as follows:
（2）；
wherein x, y, z represent positionA represents the radius of the sphere model, < +.>；
Direct signal vector from GNSS satelliteAnd reflected signal vector received by GNSS-R satellite +.>Position on the spheronization model +.>The normal vector of (2) are coplanar and expressed as follows:
（3）
wherein t is 1 、t 2 、t 3 Representing the positionCoordinates r of (2) 1 、r 2 、r 3 Representation of the position->Coordinates of (c);
the incident angle of the direct signal emitted by the GNSS satellite and the reflected angle of the reflected signal received by the GNSS-R satellite are the same as shown below:
（4）
according to an embodiment of the present invention, the position of the GNSS satellites is determinedAnd (2) and (4) position>Position of corresponding GNSS-R satellite +.>And position of the initial value of the GNSS-R specular reflection point +.>Obtaining a third included angle->Value of->And a fourth included angle->Value of->Comprising:
from the position of GNSS satellitesPosition vector relative to the sphere center O of the sphere model +.>Position of GNSS-R satellite>Position vector relative to the sphere center O of the sphere model +.>And position of the initial value of the GNSS-R specular reflection point +.>Position vector relative to the sphere center O of the sphere model +.>Obtain the position vector +.>And position vector->The value of the third included angle between +.>Position vector +.>And position vector->The value of the fourth included angle between +.>。
According to an embodiment of the present invention, in operation S240, the value of the third included anglePosition vector +.>And position vector->Fourth included angle->Value of->The following relationship is satisfied:
（5）
in the formula (5), by using plural sets of sample data, the coefficient p of the polynomial in the formula (5) can be determined 0 、p 1 、p 2 Is a value of (2).
According to an embodiment of the present invention, there is further provided a device for determining a position of an initial value of a GNSS-R specular reflection point, for implementing the above method, where the device includes an establishing module, a first obtaining module, a second obtaining module, and a rotating module.
The building module is used for building a sphere model according to a long half shaft A of the WGS84 ellipsoid model and a short half shaft B of the WGS84 ellipsoid model, wherein the sphere center of the sphere model is the sphere center O of the WGS84 ellipsoid model, the radius of the sphere model is equal to the average value of the long half shaft A of the WGS84 ellipsoid model and the short half shaft B of the WGS84 ellipsoid model, and the rotation angular velocity of the sphere model is the same as that of the WGS84 ellipsoid model;
a first obtaining module adapted to determine a first included angle according to the position T, GNSS-R of the GNSS satellite, the position R of the satellite and the sphere center O of the sphere modelValue of->；
A second obtaining module adapted to obtain a first angleValue of->And a polynomial function to obtain a second angle +.>Wherein S is 0 Representing the position of the initial value of the GNSS-R specular reflection point, S 0 Is positioned on the sphere model;
the rotation module is suitable for taking the normal line of the surface where the sphere center O, the position T of the GNSS satellite and the position R of the GNSS-R satellite are positioned as rotationThe rotating shaft rotates the straight line where the sphere center O and the position T of the GNSS satellite are positioned around one side of the rotating shaft to the GNSS-R satelliteThe intersection point of the rotated straight line and the spherical model is the position S of the initial value of the GNSS-R specular reflection point 0 。
According to an embodiment of the present invention, there is also provided an electronic apparatus including:
one or more processors;
storage means for storing one or more programs,
wherein the one or more programs, when executed by the one or more processors, cause the one or more processors to perform the method described above.
There is also provided, in accordance with an embodiment of the present invention, a computer-readable storage medium having stored thereon executable instructions that, when executed by a processor, cause the processor to perform the method described above.
The following describes a method for determining the initial value of the GNSS-R specular reflection point according to the present invention in detail by using specific examples.
Fig. 2 is a flowchart of a method for determining a position of an initial value of a GNSS-R specular reflection point according to an embodiment of the present invention.
As shown in fig. 2, the determining method specifically includes the following steps:
step A: firstly, constructing a spherical model, so that the sphere center of the spherical model is the same as the sphere center O of a WGS84 ellipsoidal model, and the radius of the spherical model is equal to the average value of a long half axis A of the WGS84 ellipsoidal model and a short half axis B of the WGS84 ellipsoidal modelThe rotation angular velocity of the spherical model is the same as that of the WGS84 ellipsoidal model, and the half axis is longShort half shaft->。
And (B) step (B): from the position of GNSS satellitesAnd->Position of corresponding GNSS-R satellite +.>Position of the initial value of the GNSS-R specular reflection point is obtained +.>。
Step C: constructing a plurality of groups of spherical centers O with starting points of spherical models and end points of spherical centers O respectivelyAnd->Corresponding->Is->Position vector +.>、/>、/>And calculate +.>Value of->And->Values of (2)。
Step D: multiple sets of sample data (each sample data includesValue of->And corresponding toValue of->) Carrying out a polynomial fitting based on a minimum variance to the formula (5) to obtain a coefficient p of a polynomial 0 、p 1 、p 2 Is a value of (2); coefficients p according to polynomials 0 、p 1 、p 2 Is comprised of +.>Values of (2)And corresponding->Value of->The residual +.>According to the coefficient p of the polynomial 0 、p 1 、p 2 Is the value of (2) and the residual->Is a polynomial function, i.e., expression (1). Determining a position vector->Position vector/>Position vector +.>Aiming at calculating a third included angle->Values of (2)And a fourth included angle->Value of->And then making a mat for polynomial fitting.
Step E: determining a first included angle according to the position T, GNSS of the GNSS satellite-R, the position R of the satellite and the sphere center O of the sphere modelValue of->According to the first included angle->Value of->And polynomial function to obtain a second included angleValue of->。
Step F: the normal line of the surface where the position T of the spherical center O, GNSS satellite and the position R of the GNSS-R satellite are positioned is taken as a rotation axis, and the straight line where the spherical center O and the position T of the GNSS satellite are positioned rotates around one side of the rotation axis of the GNSS-R satelliteThe intersection point of the rotated straight line and the spherical surface of the spherical model is the position S of the initial value of the GNSS-R specular reflection point 0 。
FIG. 3 illustrates the number of iterations of obtaining GNSS-R specular reflection points using different methods provided in accordance with an embodiment of the present invention.
As shown in fig. 3, the upper solid line is the iteration number of calculating the true value of the specular reflection point by using the projected point of the GNSS-R satellite on the ellipsoid as the initial value of the GNSS-R specular reflection point in the conventional calculation method (i.e., the projective point method), and the lower solid line is the iteration number of calculating the specular reflection point by using the initial value of the GNSS-R specular reflection point obtained by the method provided by the embodiment of the present invention. Comparing the results of the two, the iteration number of the method provided by the embodiment of the invention is 4, and the iteration number of the method taking the projection of the GNSS-R satellite on the WGS84 ellipsoid as the initial value of the GNSS-R specular reflection point is 8. The iteration times of the method provided by the embodiment of the invention are obviously reduced.
According to an embodiment of the invention, the data of fig. 3 is from a whirlwind global satellite navigation system (The Cyclone Global Navigation Satellite System), abbreviated as CYGNSS. The system consists of 8 low-orbit satellites with orbit height of about 500km, can detect sea wind by using GNSS signals and reflected signals, and selects one day of CYGNSS detection data according to the data of FIG. 3.
The initial values of the specular reflection points calculated by the method and the conventional method (projection point method) are respectively substituted into the specular reflection point calculation to respectively obtain the positions of the specular reflection points on the ellipsoid, which are calculated by the method and the conventional method (projection point method) in the embodiment of the invention, in the directions X, Y, Z.
And respectively calculating difference values of the specular reflection point positions on the ellipsoid calculated by the method and the conventional method and the specular reflection point data of the CYGNSS data source, thereby obtaining the accuracy of the GNSS-R specular reflection point positions calculated by the method and the conventional method (projection point method) in the three directions X, Y, Z.
FIG. 4 shows the accuracy of the GNSS-R specular reflection point truth values obtained using the two methods of FIG. 3.
As shown in fig. 4, X, Y, Z represents three coordinate axes, and as can be seen from fig. 4, the initial values calculated by the method according to the embodiment of the present invention and the conventional method (projective point method) are respectively substituted into the calculation of the specular reflection point, and the accuracy level of the specular reflection point on the ellipsoid obtained by the two methods (in the X, Y, Z direction) is the same, and the obtained accuracy levels of the two methods are shown in fig. 4. Therefore, the method provided by the embodiment of the invention is effective, and the iteration process for calculating the true value of the GNSS-R specular reflection point can be quickened.
The data of fig. 4 is from a cyclone global satellite navigation system (The Cyclone Global Navigation Satellite System), abbreviated as CYGNSS, according to an embodiment of the invention. The system consists of 8 low-orbit satellites with orbit height of about 500km, can detect sea wind by using GNSS signals and reflected signals, and selects one day of CYGNSS detection data according to the data of FIG. 4.
According to the method for determining the position of the initial value of the GNSS-R specular reflection point provided by the embodiment of the invention, the initial value of the GNSS-R specular reflection point is close to the true value S (shown in figure 1) of the specular reflection point on the WGS84 ellipsoid model, and the iteration times are smaller. Therefore, the method can effectively reduce the iteration times in the calculation process of the specular reflection point.
The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the invention, and is not meant to limit the invention thereto, but to limit the invention thereto, and any modifications, equivalents, improvements and equivalents thereof may be made without departing from the spirit and principles of the invention.

Claims (9)

1. A method for determining the position of an initial value of a GNSS-R specular reflection point, comprising:
establishing a sphere model according to a long half shaft of the WGS84 ellipsoid model and a short half shaft of the WGS84 ellipsoid model, wherein the sphere center of the sphere model is the sphere center O of the WGS84 ellipsoid model, the radius of the sphere model is equal to the average value of the long half shaft of the WGS84 ellipsoid model and the short half shaft of the WGS84 ellipsoid model, and the rotation angular velocity of the sphere model is the same as that of the WGS84 ellipsoid model;
determining a first included angle according to the position T, GNSS of the GNSS satellite-R, the position R of the satellite and the sphere center O of the sphere modelValue of->；
According to the first included angleValue of->And a polynomial function to obtain a second angle +.>Values of (2)Wherein S is 0 Representing the position of the initial value of the GNSS-R specular reflection point, said S 0 The spherical surface of the spherical model is positioned on the spherical surface of the spherical model;
taking the normal line of the surface where the spherical center O, the position T of the GNSS satellite and the position R of the GNSS-R satellite are positioned as rotation shafts, and rotating the straight line where the spherical center O and the position T of the GNSS satellite are positioned around the rotation shafts to one side of the GNSS-R satelliteThe intersection point of the rotated straight line and the spherical surface of the spherical model is the position S of the initial value of the GNSS-R specular reflection point 0 ；
Wherein the polynomial function is expressed as follows:
；
wherein p is 0 、p 1 、p 2 The coefficients of the polynomial are represented by,representing the residual.
2. The method according to claim 1, wherein the method for obtaining coefficients of the polynomial comprises:
acquiring a sample set comprising a plurality of sets of sample data, each set of sample data comprising a position of a GNSS satelliteAnd +.>Position ∈of the corresponding GNSS-R satellite>；
Based on the position of the GNSS satellitesAnd +.>Position ∈of the corresponding GNSS-R satellite>Position of initial value of GNSS-R specular reflection point is obtained +.>；
Based on the position of the GNSS satellitesAnd->Position ∈of the corresponding GNSS-R satellite>And position of the initial value of the GNSS-R specular reflection point +.>Obtaining a third included angle->Value of->And a fourth included angle->Values of (2)；
According to the third included angleValue of->And said fourth angle->Value of->Obtaining coefficients of the polynomial.
3. The method of claim 2, wherein the position of the GNSS satellites is determinedAnd->Position ∈of the corresponding GNSS-R satellite>Position of initial value of GNSS-R specular reflection point is obtained +.>Comprising the following steps:
based on constraint conditions, according to the position of the GNSS satelliteAnd +.>Position ∈of the corresponding GNSS-R satellite>Position of initial value of GNSS-R specular reflection point is obtained +.>Wherein the position->And said position->Characterizing direct signal vector emitted by said GNSS satellite>Said location->And said position->Representing the reflected signal vector received by said GNSS-R satellite>；
The constraint conditions include: the position of the initial value of the GNSS-R specular reflection pointOn the sphere of the sphere model, the direct signal vector emitted by the GNSS satellite is +.>Reflection signal vector received by the GNSS-R satellite>Passing the initial value position of the specular reflection point +.>Normal vectors at the position are coplanar, the incident angle is the same as the reflection angle, and the incident angle is the direct signal vector +.>The angle between the straight line and the straight line with the normal vector is the reflection angle which is the reflection signal vector +.>And an included angle between the straight line and the straight line of the normal vector.
4. The method of claim 3, wherein the step of,
the position of the initial value of the GNSS-R specular reflection pointThe spherical surface of the sphere model is represented as follows:
；
wherein x, y, z represent the positionA represents the radius of the sphere model;
direct signal vector emitted by the GNSS satelliteAnd a reflected signal vector received by the GNSS-R satellitePassing the position on the sphere model +.>The normal vector of (c) is expressed as follows:
；
wherein t is 1 、t 2 、t 3 Representing the positionCoordinates r of (2) 1 、r 2 、r 3 Representing said position +.>Coordinates of (c);
the incident angle of the direct signal sent by the GNSS satellite and the reflected angle of the reflected signal received by the GNSS-R satellite are the same as shown in the following table:
。
5. the method of claim 1, wherein the first angle is determined based on the position of the GNSS satellite T, GNSS-R satellite position R and the spherical center O of the spherical modelValue of->Comprising the following steps:
position vector based on the position T of GNSS satellites relative to the sphere center O of the sphere modelAnd a position vector of the position R of the GNSS-R satellite with respect to the sphere center O of the spherical model>Obtaining said position vector->And the position vectorThe value of the first included angle between +.>。
6. The method of claim 2, wherein the position of the GNSS satellites is determinedAnd to the locationPosition ∈of the corresponding GNSS-R satellite>And position of the initial value of the GNSS-R specular reflection point +.>Obtaining a third included angleValue of->And a fourth included angle->Value of->Comprising:
based on the position of the GNSS satellitesPosition vector relative to the sphere center O of the sphere model +.>Position of the GNSS-R satellite>Position vector relative to the sphere center O of the sphere model +.>The position of the initial value of the GNSS-R mirror reflection point +.>Position vector relative to the sphere center O of the sphere model +.>Obtaining said position vector->And the position vector->The value of the third included angle between +.>Said position vector +.>And the position vector->The value of the fourth included angle between +.>。
7. A device for determining a position of an initial value of a GNSS-R specular reflection point, for implementing the method according to any of claims 1 to 6, said device comprising:
the building module is used for building a sphere model according to a long half shaft A of the WGS84 ellipsoid model and a short half shaft B of the WGS84 ellipsoid model, wherein the sphere center of the sphere model is the sphere center O of the WGS84 ellipsoid model, the radius of the sphere model is equal to the average value of the long half shaft A of the WGS84 ellipsoid model and the short half shaft B of the WGS84 ellipsoid model, and the rotation angular velocity of the sphere model is the same as that of the WGS84 ellipsoid model;
a first obtaining module adapted to determine a first included angle according to the position T, GNSS-R of the GNSS satellite, the position R of the satellite and the sphere center O of the sphere modelValue of->；
A second obtaining module adapted to obtain a first angleValue of->And a polynomial function to obtain a second angle +.>Wherein S is 0 Representing the position of the initial value of the GNSS-R specular reflection point, said S 0 Is positioned on the sphere model;
the rotating module is suitable for rotating the line where the spherical center O and the position T of the GNSS satellite are located around the rotating shaft to one side of the GNSS-R satellite by taking the normal line of the surface where the spherical center O and the position T of the GNSS-R satellite are located as the rotating shaftAnd the intersection point of the rotated straight line and the spherical model is the position of the initial value of the GNSS-R specular reflection point.
8. An electronic device, comprising:
one or more processors;
storage means for storing one or more programs,
wherein the one or more programs, when executed by the one or more processors, cause the one or more processors to perform the method of any of claims 1-6.
9. A computer readable storage medium having stored thereon executable instructions which, when executed by a processor, cause the processor to perform the method according to any of claims 1-6.
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