CN110376623B - Satellite-borne GNSS-R mirror reflection point ocean tide correction positioning method and system - Google Patents

Satellite-borne GNSS-R mirror reflection point ocean tide correction positioning method and system Download PDF

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CN110376623B
CN110376623B CN201910610654.9A CN201910610654A CN110376623B CN 110376623 B CN110376623 B CN 110376623B CN 201910610654 A CN201910610654 A CN 201910610654A CN 110376623 B CN110376623 B CN 110376623B
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郑伟
吴凡
李钊伟
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China Academy of Space Technology CAST
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/40—Correcting position, velocity or attitude
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
    • G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/42—Determining position

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Abstract

The invention discloses a satellite-borne GNSS-R mirror reflection point ocean tide correction positioning method and a system, wherein the method comprises the following steps: acquiring space position information of a navigation satellite and a receiver; determining a mirror reflection point S on a reference ellipsoid according to the acquired space position information of the navigation satellite and the receiver; acquiring a static elevation correction amount and a time-varying elevation correction amount; according to the static elevation correction quantity and the time-varying elevation correction quantity, static correction and time-varying correction are carried out on the specular reflection point S on the reference ellipsoid, and a specular reflection point S' on the ocean tidal surface is obtained; and carrying out normal correction on the specular reflection point S ' on the ocean tidal plane to obtain the position S ' of the specular reflection point S ' on the ocean tidal plane on the normal vertical plane of the ocean tidal plane. The method improves the sea surface positioning precision of the satellite-borne GNSS-R mirror reflection point.

Description

Satellite-borne GNSS-R mirror reflection point ocean tide correction positioning method and system
Technical Field
The invention belongs to the cross technical field of satellite altimetry, ocean gravimetry, ocean tides and the like, and particularly relates to a satellite-borne GNSS-R mirror reflection point ocean tide correction positioning method and system.
Background
The global navigation satellite signal reflection technology (GNSS-R) is used as a new generation sea surface height measurement technology, and the principle is that the height measurement is realized by utilizing the path difference between GNSS sea surface reflection signals and direct signals reaching a receiver. Compared with the traditional satellite altimeter for height measurement, the GNSS-R height measurement has the advantages of rich signal sources, low effective load cost, all weather, all-time, low power consumption and the like, a plurality of sea surface reflection signals can be obtained at the same time based on a multi-channel receiver, the global sea surface height measurement with high spatial resolution can be realized by combining a plurality of GNSS-R satellite networks, and then the global sea gravity field reference map with high spatial resolution can be obtained, so that support is provided for underwater gravity matching navigation.
The underwater gravity matching navigation is an effective means for carrying out necessary correction on drift errors of the submersible inertial navigation system, and the establishment of a global marine gravity reference map with global and high spatial resolution and high precision is a key for determining the underwater gravity matching navigation precision. At present, the conventional means for acquiring the global ocean gravity field is to convert the sea level height acquired by a satellite radar altimeter into gravity anomaly.
The high-resolution advantage of the GNSS-R satellite sea surface height measurement is brought into play, the application of the GNSS-R satellite sea surface height measurement in inverting the high-spatial resolution and high-precision ocean gravitational field is realized, and the precision needs to reach the cm level. As one of main error sources of height measurement, the positioning error of the mirror reflection point is a main factor for restricting the improvement of the height measurement precision. The specular reflection point is a point on the reflection surface which enables the GNSS satellite signal to reach the receiver by the minimum distance through reflection, and is a reference point of the GNSS-R signal reflection geometrical relation and a reference center of related parameters, and the sea surface height measurement accuracy directly related to the distance error is influenced on the reference point by the positioning error of the specular reflection point. The GNSS-R sea surface height measurement signal reflection surface is an instantaneous sea surface, but the reflection reference surfaces which are selected by the current mirror reflection point geometric positioning method and are closest to the actual sea surface are all earth ellipsoids, and the Sea Surface Height (SSH) which is the height difference between the ellipsoids and the instantaneous sea surface is not considered, so that the mirror reflection point positioning error is large.
Disclosure of Invention
The technical problem of the invention is solved: the defects of the prior art are overcome, the satellite-borne GNSS-R mirror reflection point ocean tide correction positioning method and the satellite-borne GNSS-R mirror reflection point ocean tide correction positioning system are provided, and the sea surface positioning accuracy of the satellite-borne GNSS-R mirror reflection point is improved.
In order to solve the technical problem, the invention discloses a satellite-borne GNSS-R mirror reflection point ocean tide correction positioning method, which comprises the following steps:
acquiring space position information of a navigation satellite and a receiver;
determining a mirror reflection point S on a reference ellipsoid according to the acquired space position information of the navigation satellite and the receiver;
acquiring a static elevation correction amount and a time-varying elevation correction amount;
according to the static elevation correction quantity and the time-varying elevation correction quantity, static correction and time-varying correction are carried out on the specular reflection point S on the reference ellipsoid, and a specular reflection point S' on the ocean tidal surface is obtained;
and carrying out normal correction on the specular reflection point S ' on the ocean tidal plane to obtain the position S ' of the specular reflection point S ' on the ocean tidal plane on the normal vertical plane of the ocean tidal plane.
In the satellite-borne GNSS-R specular reflection point ocean tide correction positioning method, determining a specular reflection point S on a reference ellipsoid according to the acquired spatial position information of the navigation satellite and the receiver includes:
according to the obtained space position information of the navigation satellite and the receiver, the position vectors of the navigation satellite T, the receiver R and the specular reflection point S on the reference ellipsoid are respectively expressed as:
Figure BDA0002122254020000021
and
Figure BDA0002122254020000022
then there are:
Figure BDA0002122254020000023
wherein HRAnd HTRespectively represent
Figure BDA0002122254020000024
And
Figure BDA0002122254020000025
relative to the geodesic difference of the ellipsoid,
Figure BDA0002122254020000026
the position vector of an intermediate variable M point is represented, the M point is the intersection point of the extension line of the OS connecting line and the TR connecting line, O represents the center of the earth sphere, and the longitude and latitude of the specular reflection point S are the same as those of the M point;
resolving the formula (1) to obtain the coordinates of the specular reflection point S:
Figure BDA0002122254020000027
wherein the content of the first and second substances,
Figure BDA0002122254020000028
(X, Y, Z) represents a specular reflection pointSB and l respectively represent the initial latitude and initial longitude corresponding to the specular reflection point S on the reference ellipsoid, a represents the major radius of the WGS-84 ellipsoid, and e represents the first eccentricity of the WGS-84 ellipsoid.
In the above method for correcting and positioning marine tide using satellite-borne GNSS-R specular reflection points, according to the static elevation correction amount and the time-varying elevation correction amount, static correction and time-varying correction are performed on the specular reflection point S on the reference ellipsoid to obtain a specular reflection point S' on the marine tide surface, including:
correcting quantity H according to the static elevationGSum time varying elevation correction HTAnd (3) carrying out static correction and time-varying correction on the formula (2) to obtain the coordinates of the specular reflection point S' on the ocean tidal surface:
Figure BDA0002122254020000031
wherein (X ', Y', Z ') represents the coordinate of the specular reflection point S' (. epsilon.)x,εy,εz) Indicating static elevation correction amount HGThree correction components in the x, y and z directions; (sigma)x,σy,σz) Represents the time-varying elevation correction amount HTThree correction components in the x, y and z directions.
In the satellite-borne GNSS-R mirror reflection point ocean tide correction positioning method, acquiring a time-varying elevation correction quantity includes:
extracting harmonic constant prediction tide from a positive pressure tide elevation solution of the TPXO8 model;
carrying out tide inversion on the extracted harmonic constant prediction tide to obtain an expression of the tide division h of a single component i with an angular rate of w:
Figure BDA0002122254020000032
where t denotes the time of each iteration, b 'and l' denote the latitude and longitude of each iteration, respectively, and fuThe intersection factor, f, representing the horizontal direction of each iterationhThe intersection factor, V (t), representing the vertical direction of each iteration0) Representing the initial time t of an iteration0The astronomical phase angle of (c);
from equation (4), an expression for the harmonic constant amplitude a and phase K is determined:
A＝|h|···(5)
K＝arc tan|{-Im[h]/Re[h]}|···(6)
according to the formulas (4) - (6), harmonic analysis is carried out, the total tidal height is predicted, and the time-varying elevation correction quantity H is obtainedTExpression (c):
Figure BDA0002122254020000041
wherein M represents the average sea level height, n represents the number of partial tides, the subscript j represents the j th partial tide, fjThe intersection factor, V, representing the j-th partial tidej(t) denotes the astronomical phase angle at time t of the j-th tide, AjDenotes the amplitude of the harmonic constant, K, corresponding to the j-th partial tidejIndicating the phase corresponding to the j-th tide.
In the satellite-borne GNSS-R mirror reflection point ocean tide correction positioning method, the time-varying elevation correction component (sigma) is obtained by calculation through the following stepsx,σy,σz)：
Determining a time-varying elevation correction component (σ) for each iteration based on equations (3) and (7)x,σy,σz) Expression (c):
Figure BDA0002122254020000042
after iterative correction for m times, the total time-varying elevation correction component (omega) satisfying the cut-off threshold valuex,ωy,ωz) The following were used:
Figure BDA0002122254020000043
in the satellite-borne GNSS-R mirror reflection point ocean tide correction positioning method, the mirror reflection point S ' on the ocean tide surface is corrected in the normal direction to obtain the position S ' of the mirror reflection point S ' on the ocean tide surface on the normal vertical plane of the ocean tide surface
And according to the deviation correction quantity of the perpendicular line of the mirror reflection point, carrying out normal iterative correction on the reflection path to the normal direction of the ground level, and carrying out normal iterative correction on the mirror reflection point S ' to obtain the position S ' of the mirror reflection point S ' on the normal perpendicular plane of the ocean tidal plane.
The invention also discloses a satellite-borne GNSS-R mirror reflection point ocean tide correction positioning system, which comprises:
the first acquisition module is used for acquiring the spatial position information of a navigation satellite and a receiver;
the determining module is used for determining a mirror reflection point S on the reference ellipsoid according to the acquired space position information of the navigation satellite and the receiver;
the second acquisition module is used for acquiring a static elevation correction amount and a time-varying elevation correction amount;
the first correction module is used for performing static correction and time-varying correction on the specular reflection point S on the reference ellipsoid according to the static elevation correction and the time-varying elevation correction to obtain a specular reflection point S' on the ocean tidal surface;
and the second correction module is used for performing normal correction on the specular reflection point S ' on the ocean tidal plane to obtain the position S ' of the specular reflection point S ' on the ocean tidal plane on the normal vertical plane of the ocean tidal plane.
The invention has the following advantages:
the invention applies the ocean tide which is the main parameter for determining the real-time change of the sea surface height to construct the ocean tide time-varying elevation correction positioning method, and the positioning accuracy of the ocean tide time-varying elevation correction positioning method is tested based on the comparison of the reflection geometric relation and the reference surface accuracy; the method corrects the mirror reflection point from the ground level surface to the sea tide surface by applying the sea tide time-varying elevation correction positioning method, reduces the positioning error caused by the time-varying elevation difference of the reflection reference surface, further improves the positioning precision on the basis of static elevation correction positioning, and quantifies the improvement of the precision.
In addition, the invention aims at the characteristic that the ocean tides have different high gradients in offshore and deep sea, and verifies the different influences of the tides in two sea areas on the gradient of the positioning precision improvement amount. According to research results, the precision of the ground level positioning is improved by about 0.31m by the ocean tide time-varying elevation correction positioning method. The improvement of the positioning precision has better correlation with the tide heights of different amplitude and phase combinations. In the offshore area, the tide height gradient is larger than that in the deep open sea, and the gradient of the tide height positioning correction quantity has better response to the tide height gradient; in the deep open sea, the gradient of the tidal height positioning modifier is less sensitive to the response of the tidal height gradient change than in the offshore region.
Drawings
FIG. 1 is a flowchart illustrating steps of a method for calibrating and positioning marine tide based on satellite-borne GNSS-R mirror reflection points according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a position of a specular reflection point according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the geometric relationship of a specular reflection point in an embodiment of the present invention;
FIG. 4 is a schematic diagram illustrating a simulation of tidal height and corresponding tidal elevation positioning corrections for each track in an embodiment of the present invention;
FIG. 5 is a schematic diagram of a simulation of the tidal height of each track and the corresponding tidal elevation positioning corrections and a fit of the two in an embodiment of the present invention;
FIG. 6 is a schematic diagram illustrating a simulation of a deep sea-offshore trajectory tidal height model and its gradient, in accordance with an embodiment of the present invention;
FIG. 7 is a schematic diagram of a simulation of the gradient of the offshore tidal height mode and the corresponding tidal positioning correction gradient, in accordance with an embodiment of the present invention;
FIG. 8 is a schematic diagram illustrating a simulation of the gradient of the tidal height model of the open and deep sea and the corresponding gradient of the tidal elevation calibration correction amount according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of a simulation of the tidal height mode gradient and the corresponding tidal positioning modifier gradient and the fitting of the two in an offshore segment and a deep and open sea segment, in accordance with an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in fig. 1, in this embodiment, the method for positioning marine tide by satellite-borne GNSS-R specular reflection point includes:
step 101, acquiring spatial position information of a navigation satellite and a receiver.
And 102, determining a mirror reflection point S on the reference ellipsoid according to the acquired space position information of the navigation satellite and the receiver.
In the present embodiment, as shown in fig. 2 and fig. 3, the position vectors of the navigation satellite T, the receiver R, and the specular reflection point S on the reference ellipsoid can be respectively expressed as:
Figure BDA0002122254020000071
and
Figure BDA0002122254020000072
then there are:
Figure BDA0002122254020000073
wherein HRAnd HTRespectively represent
Figure BDA0002122254020000074
And
Figure BDA0002122254020000075
relative to the geodesic difference of the ellipsoid,
Figure BDA0002122254020000076
and the position vector of the M point of the intermediate variable is represented, the M point is the intersection point of the extension line of the OS connecting line and the TR connecting line, the O represents the center of the earth sphere, and the longitude and latitude of the specular reflection point S are the same as those of the M point.
Solving the formula (1) to obtain the coordinates of the specular reflection point S on the reference ellipsoid:
Figure BDA0002122254020000077
wherein the content of the first and second substances,
Figure BDA0002122254020000078
(X, Y, Z) represents a specular reflection pointSB and l respectively represent the initial latitude and initial longitude corresponding to the specular reflection point S on the reference ellipsoid, a represents the major radius of the WGS-84 ellipsoid, and e represents the first eccentricity of the WGS-84 ellipsoid.
Step 103, obtaining static elevation correction and time-varying elevation correction.
And 104, performing static correction and time-varying correction on the specular reflection point S on the reference ellipsoid according to the static elevation correction amount and the time-varying elevation correction amount to obtain a specular reflection point S' on the ocean tidal surface.
In this embodiment, the static elevation correction amount H may be based on the static elevation correction amountGSum time varying elevation correction HTAnd (3) carrying out static correction and time-varying correction on the formula (2) to obtain the coordinates of the specular reflection point S' on the ocean tidal surface:
Figure BDA0002122254020000079
wherein (X ', Y', Z ') represents the coordinate of the specular reflection point S' (. epsilon.)x,εy,εz) Indicating static elevation correction amount HGThree correction components in the x, y and z directions; (sigma)x,σy,σz) Represents the time-varying elevation correction amount HTThree correction components in the x, y and z directions.
And 105, performing normal correction on the specular reflection point S ' on the ocean tidal plane to obtain a position S ' of the specular reflection point S ' on the ocean tidal plane on a normal vertical plane of the ocean tidal plane.
In this embodiment, the steps 101-104 are based on the assumption that the normal direction and the radial direction of the specular reflection point are consistent, and there is a certain difference between the two, which may cause a positioning error, so that the specular reflection point S' needs to be further corrected to the normal vertical plane of the ocean tide plane. By applying an approximate normal projection correction method and directly solving the space geometric relationship between the projection of the normal direction on a plane and a reflection path, the mirror reflection point S' is corrected to the normal vertical plane of the ocean tidal plane, so that the positioning error caused by the radial-normal difference is reduced, the influence of approximate substitution on normal correction is reduced, and the positioning precision is further improved towards the normal direction.
It should be noted that, as described above, the sea surface height is decomposed into a static elevation and a time-varying elevation: 1) the static elevation is the height difference (geoid difference) between the geoid and the reference ellipsoid determined by the gravity of the earth, and the time variation is low; 2) the time-varying elevation is the real-time change of the sea surface height of the instantaneous sea surface distance to the ground level surface caused by various external power such as tide, wind, ground current, mesoscale vortex, circulation, tsunami and the like, namely the sea surface dynamic terrain, and has strong time-varying property.
Introducing static elevation correction quantity HGThe mirror reflection point can be corrected to the geoid from the reference ellipsoid, but the geoid still has a time-varying elevation error from the actual sea surface, and the time-varying elevation correction quantity H needs to be further determinedTAnd further correcting the mirror reflection point from the ground level surface to the ocean tide surface.
Preferably, the static elevation correction amount HGThe acquisition mode of (1) may be as follows: calculating to obtain a static elevation correction quantity H through an EGM2008 model according to b and lG。
Further, a time-varying elevation correction amount H for a specified position and timeTThe prediction of (a) requires a tidal analysis based on a tidal model. Tidal analysis refers to the separation or estimation of tidal parameters based on actual observations, and the forecasting of tides at any location and time based on these parameters. To facilitate the prediction of tidal changes, the tide is broken down into a superposition of a plurality of sinusoids of different periods and amplitudes, each representing a different partial tide, all of which form a time-varying tide. The main method of modern tide analysis and forecast is harmonic analysis, which is to estimate the amplitude and phase of a specific tide in a specified period, i.e. to solve the harmonic constant of each tide according to a tide height expression and actual observation data, so as to obtain the total tide height. Wherein the time-varying elevation correction amount HTThe specific acquisition mode of (2) may be as follows:
extracting harmonic constant prediction tide from a positive pressure tide elevation solution of the TPXO8 model;
carrying out tide inversion on the extracted harmonic constant prediction tide to obtain an expression of the tide division h of a single component i with an angular rate of w:
h(b′,l′,t)＝fu(b′,l′,t)Re[h(b′,l′)exp{i[w(t-t0)+V(t0)+fh(b′,l′,t)]}]···(4)
where t denotes the time of each iteration, b 'and l' denote the latitude and longitude of each iteration, respectively, and fuThe intersection factor, f, representing the horizontal direction of each iterationhThe intersection factor, V (t), representing the vertical direction of each iteration0) Representing the initial time t of an iteration0The astronomical phase angle of (c);
from equation (4), an expression for the harmonic constant amplitude a and phase K is determined:
A＝|h|···(5)
K＝arctan|{-Im[h]/Re[h]}|···(6)
according to the formulas (4) - (6), harmonic analysis is carried out, the total tidal height is predicted, and the time-varying elevation correction quantity H is obtainedTExpression (c):
Figure BDA0002122254020000091
wherein M represents the average sea level height, n represents the number of partial tides, the subscript j represents the j th partial tide, fjThe intersection factor, V, representing the j-th partial tidej(t) denotes the astronomical phase angle at time t of the j-th tide, AjDenotes the amplitude of the harmonic constant, K, corresponding to the j-th partial tidejIndicating the phase corresponding to the j-th tide.
Further, the time-varying elevation correction component (σ) may be solved by the following stepsx,σy,σz)：
Determining a time-varying elevation correction component (σ) for each iteration based on equations (3) and (7)x,σy,σz) Expression (c):
Figure BDA0002122254020000101
after iterative correction for m times, the total time-varying elevation correction component (omega) satisfying the cut-off threshold valuex,ωy,ωz) The following were used:
Figure BDA0002122254020000102
from the above, the improvement of the positioning accuracy of the mirror reflection point on the reference ellipsoid by the ocean tide time-varying elevation correction positioning method is the spatial distance C between the mirror reflection point on the ocean tide surface and the mirror reflection point on the reference ellipsoidT：
Figure BDA0002122254020000103
Similarly, the static elevation correction iteration satisfies the cut-off threshold value after g times, and the total static elevation correction component (delta)x,δy,δz) The following were used:
Figure BDA0002122254020000104
the improvement of the positioning accuracy of the specular reflection point on the reference ellipsoid by the static elevation correction is the spatial distance C between the specular reflection point on the geodesic surface and the specular reflection point on the reference ellipsoidG：
Figure BDA0002122254020000105
Improvement of positioning precision of mirror reflection points on ground level surface by ocean tide time-varying elevation correction positioning method C isTAnd CGThe vector difference of (2):
Figure BDA0002122254020000111
furthermore, the average value R of the gradient modes of the tidal time-varying elevation positioning correction quantity including the locus (or segment) of the u specular reflection points is:
Figure BDA0002122254020000112
wherein, CSAnd CS+1Representing two adjacent specular reflection points on the same track.
According to the formulas (7) - (14), the mode of the tide time-varying elevation positioning correction gradient is affected by the combination of the tidal height and the large ground level difference, wherein the former is different according to the time and the geographical distribution of the offshore/open sea and the like, and the latter is determined by the gravity anomaly of the position of the specular reflection point.
In conclusion, the invention takes the reference ellipsoid as an elevation starting point, corrects the static elevation error of the foundation based on the difference of the geoid and the level, predicts the tidal height of the time and the position of the mirror reflection point based on the ocean tide model on the basis of the elevation error as the time-varying elevation correction quantity, iteratively corrects and positions the mirror reflection point, and finally corrects the mirror reflection point in the non-approximate normal direction.
The embodiment of the invention adopts the following main data sources:
TDS-1(TechDemosat-1) satellite data
The invention uses the positions of the GPS satellite and the receiver in the TDS-1 satellite data to position the mirror reflection point, and compares the position with the position of the mirror reflection point in the data, so as to avoid introducing errors of orbit simulation and facilitate comparison. The TDS-1-carried GNSS-R payload includes an antenna for receiving direct and reflected GPS signals and a remote sensing receiver. The receiver records the integrated midpoint time of the available reflected signal and the spatial coordinates of the corresponding GPS satellite, receiver and specular reflection points, which are contained in the L1b level metadata of TDS-1. The position of a specular reflection point in TDS-1 data is calculated by mapping transformation of a coordinate System based on Fresnel reflection law by taking a WGS-84(World Geodetic System 1984) ellipsoid as a reflection reference surface, and the specular reflection point is used as valuable space-based GNSS-R business data to be applied. The invention uses 14768 reflection signals of 43-orbit data of 31-4 1-3.2018, the tracks of the specular reflection points have global distribution, and the invention has better coverage on the amplitude, phase and geographical distribution of tides.
EGM2008(Earth graphical Model 2008) Model
The EGM2008 model order is complete to 2159, corresponding to a spatial resolution of the model of about 5 'x 5' with a height anomaly/ground level wave propagation standard deviation of 10.925 cm. The invention uses the highest spatial resolution model interpolated to 1 'multiplied by 1' grid to calculate the height of the ground level surface, and the interpolation error is not more than +/-1 mm.
TOXO8(TOPEX/Poseido global inversion solution 8) model
The TPXO8 model is a global tide model established by Egbert and eroreena at oregon state university, usa, providing 8 main tides, 2 long-period tides, and 3 nonlinear tides. The invention discusses the influence of tidal height change of offshore shallow water regions on tidal height correction, which needs to be supported by tidal prediction with high precision and high spatial resolution at offshore sites with complex tidal change, and the TPXO8 model reinforces the precision and the spatial resolution of the regions in two aspects: 1) the TPXO8 performs orbital harmonic analysis on height measurement data such as T/P and Jason1/2, and the like, adds Envisat, ERS and tide station data in a shallow water area, and considers nonlinear 1/4-day tide so as to improve the precision of the offshore shallow water area. 2) TPXO8 developed and added 33 1/30 ° high resolution regional assimilation models based on the open boundary drive using 1/6 ° global model calculations, mainly including closed and semi-closed oceans and most continental shelf coastal areas, and using high resolution ocean depth table (GEBCO) 1' depth data in available offshore areas to improve accuracy and spatial resolution.
The simulation verification result is as follows:
the main result of the invention is based on the comparison of the ocean tide time-varying elevation correction positioning and the positioning results of other reflection reference surfaces. The SC-Wu method, as an early excellent specular reflection point positioning method, positions a specular reflection point on a reference ellipsoid; the TDS-1 method is used as a satellite service positioning method, and a mapping method is applied to position the mirror reflection point on a reference ellipsoid; then, as the first step of the series research of the actual sea surface correction positioning method, the gravitational field-normal projection combined correction positioning method corrects a static elevation error which is a basic error source of a reflection reference surface, and corrects a specular reflection point to a ground level surface from a reference ellipsoid for the first time. As another important component of the actual sea surface correction positioning, the invention firstly considers the correction of the time varying elevation positioning error on the basis of the static elevation positioning error correction, provides a marine tide time varying elevation correction positioning method, and corrects the mirror reflection point from the ground level surface to the marine tide surface. In order to compare the difference of the precision of the tide correction positioning method relative to the precision of the reference ellipsoid and the geodetic plane positioning method, the reflection relations determined by the methods are compared, and then the improvement of the positioning precision is quantified and analyzed by the ocean tide time-varying elevation correction positioning method.
Comparison of precision of ocean tide time-varying elevation correction positioning method
The evaluation standard of the invention for the positioning accuracy of the reflecting point of the mirror surface is based on Fresnel reflection law. When the positions of the transmitter and the receiver and the reflection reference surface are determined, the incident angle, the emergent angle and the reflection normal direction of signal reflection are determined by the positions of the specular reflection points, and the standard for judging the accurate positioning of the specular reflection points according to the Fresnel reflection law is as follows: 1) the exit angle is equal to the incident angle; 2) the reflection normal is perpendicular to the reflection reference plane. Because the actual calculation precision is limited, the standard can not be completely met, and the invention considers that the smaller the difference between the exit angle and the incident angle and the difference between the reflection normal direction and the reflection reference surface normal direction, the more accurate the reflection geometric relationship and the higher the positioning precision of the mirror reflection point.
The accuracy of the specular reflection point positioning method is compared based on the evaluation criteria of the positioning accuracy. And respectively calculating the difference between the incident angle and the emergent angle of the transmitter and the receiver and the positions of the specular reflection points of the transmitter and the receiver in the TDS-1 data and the positions of the specular reflection points calculated by applying the marine tide time-varying elevation correction positioning method. Compared with the TDS-1 method, the difference between the incident angle and the emergent angle of the marine tide time-varying elevation correction positioning method is 6 orders of magnitude smaller, and the standard deviation of the angle difference is 5 orders of magnitude smaller, namely the precision of the reflection geometric relation determined by the mirror reflection point of the tide correction method is higher than that of the TDS-1 method, and the positioning precision is higher. Compared with TDS-1 method, the incident angle of the tide correcting method is smaller by about 0.04rad, the standard deviation is smaller by about 0.05rad, the reflection angle is smaller by about 0.04rad, and the standard deviation is smaller by about 0.03 rad. The variation of the incident angle of the TDS-1 method is larger than the emergence angle, presumably due to the difference in satellite orbital height (GPS 20200km, TDS-1635km), the distance of the GPS satellite to the specular reflection point is much larger than the distance of the TDS-1 satellite to the specular reflection point, so that the specular reflection point positioning error is amplified in the incident direction compared to the emergence direction. Whereas the incident and emergent angles of the tidal method are closer and more stable than TDS-1, the magnification effect of the specular reflection point positioning error increases with satellite orbit height is better controlled. The difference of the marine tide time-varying elevation correction positioning method relative to TDS-1 positioning shows that the precision of the mirror reflection point positioned on the marine tide surface relative to the positioning of a service satellite on a reference ellipsoid surface is improved through static and time-varying elevation correction. Calculating the mean value of the module and space distance (Euclidean distance) of the difference between the geodetic coordinates and the space coordinates of the positioning results of the two methods and the corresponding standard deviation according to the track, and averaging the track mean value. In a space coordinate system, the positioning accuracy is improved by about 55km, in the X, Y, Z direction by-30 km, -15 km and-40 km respectively, and in a geodetic coordinate system, the positioning accuracy is improved by-0.6 degrees and-1.3 degrees respectively in the longitude and latitude directions.
Although the precision of the reflection geometrical relationship of the ocean tide correction positioning method and the SC-Wu method on the respective reflection reference surfaces is very similar to that of the TDS-1 method by adopting the same iteration cut-off threshold value, the positioning precision of the tide correction positioning method is higher than that of the SC-Wu method on the basis of the ocean tide surface closer to the actual sea surface, and the improvement of the positioning precision is the difference of the positioning results of the ocean tide correction positioning method and the SC-Wu method. The difference between the positioning results of the geohorizon correction positioning method and the S-C Wu method reflects the improvement of the positioning precision by only correcting the basic static elevation error of the reflection reference surface. The difference between the ocean tide correction positioning method and the SC-Wu method is the positioning difference between an ocean tide surface and a reference ellipsoid, and reflects the improvement of further correcting time-varying elevation errors on the positioning accuracy on the basis of static elevation error correction. In a space coordinate system, the positioning precision is improved by 36.62m, improved by 17m, 13m and 25m respectively in X, Y, Z directions, and improved by 9 multiplied by 10 respectively in longitude and latitude directions in a geodetic coordinate system-5Sum of ° 1.9 × 10-4°。
Improvement of positioning precision by ocean tide time-varying elevation correction positioning method
The improvement of positioning accuracy by introducing tide time-varying elevation correction on the basis of static elevation correction is the difference between ocean tide time-varying elevation correction positioning and geoid correction positioning, namely the correction of the position of a mirror reflection point on the geoid. Calculating the mean value of the module and the space distance (Euclidean distance) of the difference between the geodetic coordinates and the space coordinates of the positioning results of the two methods and the corresponding standard deviation and variance according to the track, and averaging the track mean value. On the basis of the correction and positioning of the ground level surface, the positioning accuracy is improved by about 0.31m by the ocean tide time-varying elevation correction positioning method in a space coordinate system, the accuracy in the X, Y, Z direction is respectively improved by-0.137 m, -0.078 m and-0.220 m, and the positioning accuracy in the longitude and latitude directions is respectively improved by-6 multiplied by 10 in the ground coordinate system-7Sum of ° 1 × 10-6Degree. Compared with other methods, the ocean tide correction positioning method has the advantages that the precision of the ocean tide correction positioning method in each direction of the space coordinate system is improved, and the standard deviation is Z>X>The longitude increases in the geodetic coordinate system by about 2 times the latitude. In order to further study the relationship between the improvement of the positioning accuracy and the tidal height, the tidal height corresponding to the specular reflection point is used as a comparison, and the average value of the tidal height module is about 0.28m, and the standard deviation thereof is about 0.16m, which is very close to the positioning correction amount and the standard deviation thereof. The mirror reflection points of each rail are distributed all over the world in space, the corresponding tide amplitude and phase distribution is different with the time and the place of each rail, and the positioning correction quantity and the tide height mode of each rail are shown in figures 4 and 5. The two are very close to each other in different amplitudes and phases, the correlation coefficient is 0.998, the good positive correlation is realized, and the correlation is not obviously reduced along with the increase of a tidal height mode. The slope of a fitting straight line of the tidal height module and the tidal positioning correction quantity is 1.071 +/-0.019, and the sum variance of the fitting straight line is 9.382 multiplied by 10-3Root mean square error of 1.513 × 10-2The error is smaller, the fitting accuracy is higher, canConsider that for a GPS-R mirror reflection point on the ocean tidal plane where time and location are determined, the tidal elevation positioning correction C is about 1.07 times the tidal height mode:
C＝1.07|HT|+λ
wherein λ is the intercept of the fitted straight line (2.569 + -7.1) × 10-3m。
In summary, the main results are as follows: the first method is that the positioning precision of the ground level surface is improved by about 0.31m, the positioning precision of the ground level surface is improved by 0.08-0.22 m in each direction of the space, and the positioning precision of the ground level surface is improved by 6-10 multiplied by 10 in the longitude and latitude directions of a ground coordinate system-7Degree. Secondly, the positioning accuracy improvement amount has better correlation with the corresponding tide height of different amplitude and phase combinations, and the improvement amount is 1.07 times of the tide height. Thirdly, the precision of the marine tide time-varying elevation correction positioning method is higher than that of the TDS-1 method, the amplification effect that the positioning error of a mirror reflection point is increased along with the height of a satellite orbit is better controlled, the positioning precision of the TDS-1 method is improved by about 55km, the positioning precision of the TDS-1 method is improved by 15-40 km in each direction of a space, and the positioning precision of the TDS-1 method is improved by 0.6-1.2 degrees in the longitude and latitude directions of a geodetic coordinate system. The ocean tide time-varying elevation correction positioning method improves the SC-Wu positioning accuracy by 36.62m, improves the SC-Wu positioning accuracy by 13-25 m in each direction of space, and improves the SC-Wu positioning accuracy by 9-19 multiplied by 10 in the longitude and latitude directions of a geodetic coordinate system-5Degree. Improvement of precision of other methods in all directions of space coordinate system by ocean tide time-varying elevation correction positioning method and standard deviation thereof are Z>X>Y, the improvement in the longitude direction of the geodetic coordinate system is about 2 times in the latitude direction.
In addition to having important characteristics of time-varying nature, ocean tides also have spatially varying characteristics offshore and in the deep open sea. Since tidal range is affected by induced tidal forces, terrain, and other conditions, which vary with time and location, it is larger offshore than deep open sea. Due to the non-linearity of tidal power in the offshore, additional partial tides such as double tides or compound tides can be formed. These partial tides have the complexity of being non-linear, of small amplitude and of short wavelength, and interact with other major partial tides (e.g. the most active M4 partial tides interact with M2 partial tides), with amplitudes up to a significant range (M4 partial tides reach amplitudes up to 1cm in certain sea areas in the atlantic ocean), which has a non-negligible effect on the tide height and its variations. Furthermore, the propagation of the tidal wave is more complex than in the deep and open sea, as the depth of the offshore water becomes shallower than in the deep and open sea, the friction of the wave against the seabed changes the propagation process. Furthermore, due to the diversity of the shapes of straits and bays in the offshore region (long straits, semi-enclosed wide bays, narrow and long semi-enclosed bays, etc.), the types and characteristics of tidal waves and tidal ranges are different, and the tidal ranges are more complex than those of deep and far seas. Offshore, on the other hand, is a critical area for the research of sea level altimetry and underwater navigation applications, where the navigation activities of the submersible are more frequent than those of deep open sea, and where the underwater topography and gravity anomaly changes are more complex. Gravity-matched navigation ensures that the course is accurate and safe to navigate needs to be based on accurate marine gravity and underwater topography data, which requires accurate offshore sea level altimetry support. Therefore, considering the requirements of offshore sea area underwater navigation on the accuracy and safety of gravity matching navigation and the requirement of GNSS-R sea surface height measurement cm-level accuracy, the influence of the offshore tide height change characteristic on the positioning accuracy of the specular reflection point needs to be taken into consideration. The distribution of the global offshore tide splitting amplitude can be well calculated through a TPXO8 sea tide model which integrates altimeter assimilation data and enhances the precision and the resolution in the offshore area. Aiming at the problem, the invention separates the offshore part and the deep open sea part in the track of the specular reflection point, and compares the tidal height variation difference in the two areas and the different influence of the tidal height variation difference on the tidal height positioning correction quantity.
Offshore and deep offshore segment division
The significant difference between ocean tides offshore and deep open sea is reflected in tidal height gradients. The gradient mode of tidal positioning corrections is influenced by the combination of tidal height, which varies according to time and geographic offshore/open sea distribution, and by the difference in geodetic gravity anomaly. Therefore, a significant difference in the high gradient of the offshore and deep sea tides can have different effects on the gradient mode of the tidal alignment correction, and reflect to some extent the difference between the two sea areas of the latter. Due to the continuity and equidistant spacing of GNSS-R specular reflection points on the surface trajectory (considering that the sampling output interval of TDS-1 satellites is 1s, the spacing between adjacent specular reflection points on the trajectory is about 7km), the tidal height gradient along the trajectory is also a sequence of equally spaced samples. FIG. 6 is a plot of the tidal height and its gradient over a specular reflection point trajectory that includes an offshore section and a deep open sea section. The tidal height along the track changes smoothly and nearly linearly in the deep and deep sea part (points 1 to 300 of the curve in fig. 6), while the change amplitude of the tidal height is obviously increased in the offshore part (point 300 of the curve in fig. 6), and the increase and decrease of the tidal height have larger randomness, and the offshore track segment length with the characteristic ranges from several kilometers to several hundred kilometers. Furthermore, the periodic black body correction of the noise reference by TDS-1 causes periodic jumps in the positioning of the specular reflection points. Wu (2019) discusses the effect of the jump of TDS-1 data on the positioning accuracy, and although the jump has little effect on the positioning accuracy of the modified positioning method, the jump of the tide height along the track (fig. 6 curve jump) causes the tide height gradient to generate periodic miscellaneous peaks (fig. 6). The gradient peak of the tide height jump is generally equivalent to the magnitude of the gradient peak of the tide height jump in the offshore area, so that the influence on the tide height gradient and the correction gradient in the offshore area can be ignored, but the tide height gradient and the correction gradient in the deep and far sea area with gentle change can cause remarkable influence, and the tide height gradient and the correction gradient are eliminated in the analysis. The positions and the moments of the mirror reflection points on the same track are different, so the tide phases of all the points are different, but because the duration time and the space length (according to the track average length and the track average duration time) of the track are smaller than the cycle and the space change of the main partial tide and the half tide, the tide height difference caused by the tide phase difference of different mirror reflection points on the same track can be ignored.
The invention divides and compares and analyzes the offshore area and the deep and far sea on the track according to the change of the tide height gradient of each track, and the specific method is as follows.
1) Screening the tracks across sea and land.
Of the 43 tracks, 28 cross-sea-land tracks were taken, and the ocean parts in these tracks were extracted.
2) Calculating the tide height gradient of each track mirror reflection point and the corresponding tide positioning correction quantity gradient, trending and averaging the gradient sequence, and then taking a model.
3) And dividing the offshore section into a deep and open sea section.
Due to repeated crossing of part of the offshore trajectory over the sea-land, or over islands, peninsulas, etc., the same trajectory is often divided into multiple sub-trajectories by the land, and each sub-trajectory mostly contains the offshore segment. Furthermore, due to the complexity of the characteristics (length, direction, arc, distribution, etc.) of the global coastline and trajectory, the position of the offshore segment in the trajectory is also complex, mainly classified into four cases, where the offshore portion is at one end of the trajectory, at both ends of the trajectory, in the middle of the trajectory (the middle of the trajectory is near the land), or the entire segment is offshore (generally a shorter trajectory). Points in each trajectory (or sub-trajectory) where the tidal height gradient is greater than 3 times the standard deviation σ of the tidal height gradient of the trajectory are extracted, and the offshore segment and the deep and far offshore segment are divided by these points according to the four specific cases described above. The selection of the multiple of sigma ignores the tidal height gradient mutation point of a part of inshore, so that the inshore section can not be completely extracted; if the multiple is too small, some high frequency peaks will be misjudged as offshore tidal height gradient discontinuities. In addition, determining the continuously changing characteristics of the tidal height gradient requires that the track segment reach a certain length, and track segments with more than 10 continuous points (about 70km) are selected.
4) Eliminating tidal height gradient jump points
And eliminating points with the tide height gradient larger than 3 sigma in the deep and far sea section, and removing tide height gradient jump peaks and miscellaneous peaks caused by TDS-1 data jump more thoroughly.
Screening and dividing according to the method to obtain 67 offshore track sections, wherein the 67 offshore track sections comprise 2476 specular reflection points, each track section has about 37 points on average, and the average length is about 260 km; and 54 deep and far sea trajectory segments comprising 5716 specular reflection points, each trajectory segment having an average of about 106 points and an average length of about 740 km.
High gradient of offshore and deep sea tide and tide positioning correction gradient
The average value and the standard deviation of the tidal height gradient and tidal position correction gradient of the offshore section and the deep sea section are shown in fig. 7, fig. 8 and fig. 9. The tidal height gradient and the standard deviation thereof at the offshore section are obviously higher than those at the deep and far offshore sections, the gradient is about 2.5 times, and the standard deviation is about 3.5 times. The near sea tide height changes more dramatically than the deep and far sea and the gradient of the tide height varies more from segment to segment (different location and time). Compared with the larger difference of the tidal height gradient between the offshore section and the deep and far sea section, the change of the positioning correction amount gradient is closer in the two sea areas, and the offshore section gradient and the standard difference thereof are respectively 1.2 times and 2 times of the deep and far sea section. Offshore tidal height gradients have a high positive correlation with the fixed-position modifier gradient (fig. 9). Each offshore segment tidal height gradient and tidal positioning modifier gradient are very similar, and the difference between the two gradients does not increase significantly as the gradient increases (FIG. 7). This indicates that the change of the offshore tide height is increased, the change of the time-varying elevation positioning correction quantity of the mirror reflection point caused by tide is also increased, and the elevation positioning correction quantity gradient has better response to the tide height gradient. However, the difference is larger in the deep open sea, and the difference increases significantly with increasing gradient, directly because the gradient of tidal positioning corrections is higher in the deep open sea section than the tidal height gradient, and does not decrease accordingly due to the decreasing tidal height gradient (fig. 8). It is considered that the change of the tidal height positioning correction amount is more consistent in the offshore region where the change of the tidal height is larger, and the change of the tidal height tends to be gentle in the deep and distant sea, but the change of the tidal height positioning correction amount is not greatly reduced, and the sensitivity of the tidal height positioning correction amount to the response of the tidal height change is reduced compared with that in the offshore region. Presumably, the change of the underwater topography and the gravity anomaly in the deep and open sea is more severe than that in the offshore of the continental shelf with gentle water, so that the difference of the ground level and the total height positioning correction amount are more varied, which may contribute to the reduction of the sensitivity of the tidal height positioning correction amount gradient to the response of the tidal height gradient change in the deep and open sea and the maintenance of the high gradient, and also accord with the representation form that the positioning correction amount is affected by the combined action of the gravity anomaly and the tidal height.
In conclusion, in the offshore area, the tide height gradient is larger than that in the deep open sea, and the gradient of the tidal time-varying elevation positioning correction quantity of the mirror reflection point has better response to the tide height gradient; in the deep open sea, the gradient of the tidal height positioning correction does not significantly decrease with the decrease of the tidal height gradient, and the sensitivity of the tidal height gradient change response is reduced compared with that in the offshore region, presumably due to the fact that the underwater topography and gravity anomaly of the deep open sea are more severe than that in the offshore region.
Conclusion
The invention is based on the GNSS-R reflection reference surface elevation correction principle, and applies a main parameter-ocean tide for determining real-time change of sea surface elevation to construct an ocean tide time-varying elevation correction positioning method. Based on the comparison of the reflection geometric relationship and the reference surface precision, the positioning precision of the ocean tide time-varying elevation correction positioning method is tested. The method corrects the mirror reflection point from the ground level surface to the sea tide surface by applying the sea tide time-varying elevation correction positioning method, reduces the positioning error caused by the time-varying elevation difference of the reflection reference surface, further improves the positioning precision on the basis of static elevation correction positioning, and quantifies the improvement of the precision. In addition, the invention is directed to the characteristic that the height gradient of ocean tides in offshore and deep sea is different, and the different influences of the tides in the two sea areas on the positioning precision improvement amount gradient are discussed. According to research results, the precision of the ground level positioning is improved by about 0.31m by the ocean tide time-varying elevation correction positioning method. The improvement of the positioning precision has better correlation with the tide heights of different amplitude and phase combinations. In the offshore area, the tide height gradient is larger than that in the deep open sea, and the gradient of the tide height positioning correction quantity has better response to the tide height gradient; in the deep open sea, the gradient of the tidal height positioning modifier is less sensitive to the response of the tidal height gradient change than in the offshore region.
On the basis of the above embodiment, the present invention also discloses a satellite-borne GNSS-R mirror reflection point ocean tide correction positioning system, which includes: the first acquisition module is used for acquiring the spatial position information of a navigation satellite and a receiver; the determining module is used for determining a mirror reflection point S on the reference ellipsoid according to the acquired space position information of the navigation satellite and the receiver; the second acquisition module is used for acquiring a static elevation correction amount and a time-varying elevation correction amount; the first correction module is used for performing static correction and time-varying correction on the specular reflection point S on the reference ellipsoid according to the static elevation correction and the time-varying elevation correction to obtain a specular reflection point S' on the ocean tidal surface; and the second correction module is used for performing normal correction on the specular reflection point S ' on the ocean tidal plane to obtain the position S ' of the specular reflection point S ' on the ocean tidal plane on the normal vertical plane of the ocean tidal plane.
For the system embodiment, since it corresponds to the method embodiment, the description is relatively simple, and for the relevant points, refer to the description of the method embodiment section.
The embodiments in the present description are all described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The above description is only for the best mode of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Those skilled in the art will appreciate that the invention may be practiced without these specific details.

Claims (4)

1. A satellite-borne GNSS-R mirror reflection point ocean tide correction positioning method is characterized by comprising the following steps:
acquiring space position information of a navigation satellite and a receiver;
determining a mirror reflection point S on a reference ellipsoid according to the acquired space position information of the navigation satellite and the receiver;
acquiring a static elevation correction amount and a time-varying elevation correction amount; wherein the static elevation correction is calculated through an EGM2008 model; obtaining the time-varying elevation correction quantity of the specified position and time by carrying out tidal analysis on the basis of a tidal model;
according to the static elevation correction quantity and the time-varying elevation correction quantity, static correction and time-varying correction are carried out on the specular reflection point S on the reference ellipsoid, and a specular reflection point S' on the ocean tidal surface is obtained; the method comprises the following steps: correction quantity H according to static elevationGSum time varying elevation correction HTTo the reflection point of the mirror surfaceS, carrying out static correction and time-varying correction to obtain the coordinates of a mirror reflection point S' on the ocean tidal surface:
Figure FDA0003126763680000011
wherein (X, Y, Z) represents the coordinate of the specular reflection point S, and (X ', Y', Z ') represents the coordinate of the specular reflection point S' (. epsilon.)x,εy,εz) Indicating static elevation correction amount HGThree correction components in the x, y and z directions (σ)x,σy,σz) Represents the time-varying elevation correction amount HTThree correction components in the x, y and z directions, b and l respectively represent the initial latitude and initial longitude corresponding to the specular reflection point S on the reference ellipsoid, a represents the major radius of the WGS-84 ellipsoid, e represents the first eccentricity of the WGS-84 ellipsoid,
Figure FDA0003126763680000012
carrying out normal correction on the specular reflection point S ' on the ocean tidal plane to obtain the position S ' of the specular reflection point S ' on the ocean tidal plane on the normal vertical plane of the ocean tidal plane;
wherein:
obtaining a time-varying elevation correction quantity, comprising:
extracting harmonic constant prediction tide from a positive pressure tide elevation solution of the TPXO8 model;
carrying out tide inversion on the extracted harmonic constant prediction tide to obtain an expression of a single-component tide h (b ', l') with an angular rate of w:
h(b′,l′,t)＝fu(b′,l′,t)Re[h(b′,l′)exp{i[w(t-t0)+V(t0)+fh(b′,l′,t)]}]…(4)
where t denotes the time of each iteration, b 'and l' denote the latitude and longitude of each iteration, respectively, and fuThe intersection factor, f, representing the horizontal direction of each iterationhThe intersection factor, V (t), representing the vertical direction of each iteration0) Representing the initial time t of an iteration0The astronomical phase angle of (c);
from equation (4), an expression for the harmonic constant amplitude a and phase K is determined:
A＝|h(b′,l′)|…(5)
K＝arctan|{-Im[h(b′,l′)]/Re[h(b′,l′)]}|…(6)
according to the formulas (4) - (6), harmonic analysis is carried out, the total tidal height is predicted, and the time-varying elevation correction quantity H is obtainedTExpression (c):
Figure FDA0003126763680000021
wherein M represents the average sea level height, n represents the number of partial tides, the subscript j represents the j th partial tide, fjThe intersection factor, V, representing the j-th partial tidej(t) denotes the astronomical phase angle at time t of the j-th tide, Aj(b ', l', t) denotes the amplitude of the harmonic constant corresponding to the j-th partial tide, Kj(b ', l', t) denotes the phase corresponding to the j-th partial tide, wjRepresents the angular rate of the j-th partial tide, hj(b ', l') is an expression of the j-th tide;
calculating time-varying elevation correction component (sigma)x,σy,σz)：
Determining a time-varying elevation correction component (σ) for each iteration based on equations (3) and (7)x,σy,σz) Expression (c):
Figure FDA0003126763680000031
after iterative correction for m times, the total time-varying elevation correction component (omega) satisfying the cut-off threshold valuex,ωy,ωz) The following were used:
Figure FDA0003126763680000032
2. the on-board GNSS-R specular reflection point ocean tide correction positioning method of claim 1, wherein determining the specular reflection point S on the reference ellipsoid according to the acquired spatial location information of the navigation satellite and the receiver comprises:
according to the obtained space position information of the navigation satellite and the receiver, the position vectors of the navigation satellite T, the receiver R and the specular reflection point S on the reference ellipsoid are respectively expressed as:
Figure FDA0003126763680000033
and
Figure FDA0003126763680000034
then there are:
Figure FDA0003126763680000035
wherein HRAnd HTRespectively represent
Figure FDA0003126763680000036
And
Figure FDA0003126763680000037
relative to the geodesic difference of the ellipsoid,
Figure FDA0003126763680000038
the position vector of an intermediate variable M point is represented, the M point is the intersection point of the extension line of the OS connecting line and the TR connecting line, O represents the center of the earth sphere, and the longitude and latitude of the specular reflection point S are the same as those of the M point;
resolving the formula (1) to obtain the coordinates of the specular reflection point S:
Figure FDA0003126763680000041
3. the method for correcting and positioning ocean tide according to satellite-borne GNSS-R specular reflection point of claim 1, wherein the normal correction of the specular reflection point S ' on the ocean tide surface to obtain the position S ' of the specular reflection point S ' on the ocean tide surface on the normal vertical plane of the ocean tide surface comprises:
and according to the deviation correction quantity of the perpendicular line of the mirror reflection point, carrying out normal iterative correction on the reflection path to the normal direction of the ground level, and carrying out normal iterative correction on the mirror reflection point S ' to obtain the position S ' of the mirror reflection point S ' on the normal perpendicular plane of the ocean tidal plane.
4. A satellite-borne GNSS-R mirror reflection point ocean tide correction positioning system is characterized by comprising:
the first acquisition module is used for acquiring the spatial position information of a navigation satellite and a receiver;
the determining module is used for determining a mirror reflection point S on the reference ellipsoid according to the acquired space position information of the navigation satellite and the receiver;
the second acquisition module is used for acquiring a static elevation correction amount and a time-varying elevation correction amount; wherein the static elevation correction is calculated through an EGM2008 model; obtaining the time-varying elevation correction quantity of the specified position and time by carrying out tidal analysis on the basis of a tidal model;
the first correction module is used for performing static correction and time-varying correction on the specular reflection point S on the reference ellipsoid according to the static elevation correction and the time-varying elevation correction to obtain a specular reflection point S' on the ocean tidal surface; the method specifically comprises the following steps:
correction quantity H according to static elevationGSum time varying elevation correction HTAnd carrying out static correction and time-varying correction on the specular reflection point S to obtain the coordinates of the specular reflection point S' on the ocean tide surface:
Figure FDA0003126763680000042
wherein (X, Y, Z) represents the coordinate of the specular reflection point S, and (X ', Y', Z ') represents the coordinate of the specular reflection point S' (. epsilon.)x,εy,εz) Indicating static elevation correction amount HGThree correction components in the x, y and z directions (σ)x,σy,σz) Represents the time-varying elevation correction amount HTThree correction components in the x, y and z directions, b and l respectively represent the initial latitude and initial longitude corresponding to the specular reflection point S on the reference ellipsoid, a represents the major radius of the WGS-84 ellipsoid, e represents the first eccentricity of the WGS-84 ellipsoid,
Figure FDA0003126763680000051
the second correction module is used for carrying out normal correction on the specular reflection point S ' on the ocean tidal plane to obtain a position S ' of the specular reflection point S ' on the ocean tidal plane on a normal vertical plane of the ocean tidal plane;
wherein:
the second acquisition module acquires the time-varying elevation correction quantity by the following method:
extracting harmonic constant prediction tide from a positive pressure tide elevation solution of the TPXO8 model;
carrying out tide inversion on the extracted harmonic constant prediction tide to obtain an expression of a single-component tide h (b ', l') with an angular rate of w:
h(b′,l′,t)＝fu(b′,l′,t)Re[h(b′,l′)exp{i[w(t-t0)+V(t0)+fh(b′,l′,t)]}]…(4)
where t denotes the time of each iteration, b 'and l' denote the latitude and longitude of each iteration, respectively, and fuThe intersection factor, f, representing the horizontal direction of each iterationhThe intersection factor, V (t), representing the vertical direction of each iteration0) Representing the initial time t of an iteration0The astronomical phase angle of (c);
from equation (4), an expression for the harmonic constant amplitude a and phase K is determined:
A＝|h(b′,l′)|…(5)
K＝arctan|{-Im[h(b′,l′)]/Re[h(b′,l′)]}|…(6)
according to the formulas (4) - (6), harmonic analysis is carried out, the total tidal height is predicted, and the time-varying elevation correction quantity H is obtainedTExpression (c):
Figure FDA0003126763680000052
wherein M represents the average sea level height, n represents the number of partial tides, the subscript j represents the j th partial tide, fjThe intersection factor, V, representing the j-th partial tidej(t) denotes the astronomical phase angle at time t of the j-th tide, Aj(b ', l', t) denotes the amplitude of the harmonic constant corresponding to the j-th partial tide, Kj(b ', l', t) denotes the phase corresponding to the j-th partial tide, wjRepresents the angular rate of the j-th partial tide, hj(b ', l') is an expression of the j-th tide;
the second acquisition module is used for calculating and obtaining a time-varying elevation correction component (sigma) in the following wayx,σy,σz)：
Determining a time-varying elevation correction component (σ) for each iteration based on equations (3) and (7)x,σy,σz) Expression (c):
Figure FDA0003126763680000061
after iterative correction for m times, the total time-varying elevation correction component (omega) satisfying the cut-off threshold valuex,ωy,ωz) The following were used:
Figure FDA0003126763680000062
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