A Fast Convergence Method Applicable to the Star-Switching of Space-Ground RTK

Abstract

The present invention discloses a fast convergence method applicable to satellite-ground RTK when switching satellites, including: when the satellite-ground RTK is operating normally, the low-earth orbit constellation receives the information uploaded from the ground station, and uses the inter-satellite link to achieve relative time synchronization of the low-earth orbit constellation. During the satellite switching period, for stationary users, when fixed using the previous reference station, the position information solved by this reference station can be directly used as a constraint. During the satellite switching period, for low-dynamic users, GNSS speed measurement can be used to extrapolate the user position during the satellite switching period, and the position accuracy can be guaranteed within a short time. Using the extrapolated position information as a constraint, the tropospheric parameters can also follow the results of the previous epoch. During the satellite switching period, in the case of high dynamics, the user terminal carries an IMU device. The accuracy of the displacement amount can be ensured within a short time. The position information is obtained using the INS algorithm of the inertial navigation device. The tropospheric parameters follow the results solved in the previous epoch. The present invention realizes fast ambiguity fixing during satellite switching.

Description

Technical Field

[0001] The present invention belongs to the technical field of navigation and positioning, and particularly relates to a fast convergence method applicable to satellite-to-ground RTK satellite switching. Background Art

[0002] The Global Navigation Satellite System (GNSS) can provide all-weather, high-precision positioning, navigation, and timing (PNT) services to global users, playing an important role in multiple industries such as military and civilian. However, with the expansion of emerging GNSS fields, a large number of mass users have put forward higher requirements for the accuracy and timeliness of location services.

[0003] The Real-time kinematic (RTK) technology is to send the carrier phase data collected by the reference station to the user receiver for real-time differential calculation, so as to quickly solve the coordinates of the measuring station. Due to its simple implementation form and high measurement accuracy, this technology has been widely applied.

[0004] The emergence of Precise Point Positioning (PPP) technology provides a new solution for us to perform large-scale and high-precision dynamic positioning. By using non-differential precise point positioning technology to replace the traditional differential dynamic positioning technology, it can completely get rid of the dependence on ground reference stations for large-scale and long-distance measurements, significantly improve the operation efficiency, and greatly save the user cost.

[0005] However, the traditional RTK technology relies on ground base stations, and it is extremely inconvenient to build stations in remote areas, unable to meet the requirements of full-space coverage and high-quality monitoring. The PPP technology has a long convergence time and does not meet the requirements of real-time positioning. To solve the problems existing in the prior art, a new solution is to combine a large-scale low-earth orbit constellation and use inter-satellite links to broadcast navigation enhancement information to achieve RTK enhanced precise positioning services. This technology meets the requirements of full-space coverage and high-quality monitoring of RTK, and is called satellite-to-ground RTK technology.

[0006] In the satellite-to-ground RTK technology, the user terminal will receive and process the navigation enhancement information and the on-board GNSS observations of the low-earth orbit satellites. However, the visible duration of each low-earth orbit satellite is only a few minutes. When switching the reference satellite, the new low-earth orbit satellite needs a period of time to re-fix the ambiguity, which leads to the interruption of the satellite-to-ground RTK service and has an adverse impact on the user experience of the user terminal. Summary of the Invention

[0007] To solve the above technical problems, the present invention proposes a fast convergence method applicable to satellite-to-ground RTK satellite handover. By using the extrapolation of the user's position and tropospheric delay during satellite handover as constraints and substituting them into the carrier observation equation of low-earth orbit satellites, the ambiguity parameters are directly initialized using the carrier observation equation without relying on the pseudorange observation equation, achieving fast ambiguity fixing during satellite handover.

[0008] To achieve the above object, the present invention provides a fast convergence method applicable to satellite-to-ground RTK satellite handover, including:

[0009] Construct the GNSS observation equations of the user terminal and low-earth orbit satellites, construct an ionosphere-free combination model for low-earth orbit / user single-difference calculation, perform differencing on the observation results of two GNSS satellites to obtain double-difference observation equations, use the low-earth orbit constellation to obtain combined observation equations, solve the combined observation equations using the observation data of multiple navigation satellites, and perform multiple iterations to obtain the least squares optimal solution, thereby determining the position coordinates of the user terminal;

[0010] Construct the double-difference observation equation after eliminating the ionospheric influence from the carrier observation equation; keep the user terminal stationary and use the result solved by the previous reference station for the user position; estimate the tropospheric parameters of the user terminal and use the tropospheric parameters solved in the previous epoch; substitute the user position and the tropospheric parameters into the double-difference observation equation after eliminating the ionospheric influence to complete the initialization of the integer ambiguity;

[0011] Obtain the original Doppler measurement value of receiver r for satellite s at frequency point n; obtain the error equation of the Doppler measurement at frequency point j; perform Doppler measurement on several satellites and convert the error equation into matrix form; integrate the Doppler velocity measurement result to obtain the user position during satellite handover, and substitute the user position and the tropospheric parameters into the double-difference observation equation to complete the initialization of the integer ambiguity;

[0012] Obtain the acceleration of the user in the ecef coordinate system by passing the accelerometer measurement result through the specific force equation; obtain the accelerations in the north-east-down three directions based on the acceleration in the ecef coordinate system; perform integration and calculation on the accelerations in the north-east-down three directions to obtain the user position; substitute the user position and the tropospheric parameters into the double-difference observation equation to complete the initialization of the integer ambiguity.

[0013] Optionally, the method for constructing the GNSS observation equations of the user terminal and low-earth orbit satellites is:

[0014]

[0015] where P and L respectively represent pseudorange and carrier phase observation values, the subscripts g and leo respectively represent the ground station and low-earth orbit satellite, and the superscripts s and j respectively represent different numbered GNSS satellites. and respectively represent the geometric distances between the navigation satellite and the user terminal and the centroid of the low-earth orbit satellite, c is the speed of light in vacuum, and δt g , δt leo , δt s respectively represent the clock biases of the user terminal, the low-earth orbit satellite, and the navigation satellite, λ represents the signal wavelength, respectively represent the ionospheric delays of the user terminal and the low-earth orbit satellite, represents the tropospheric delay of the user terminal, respectively represent the integer ambiguities of the user terminal and the low-earth orbit satellite, and respectively represent the sum of the multipath effects and the observation noises of the pseudorange and the carrier phase.

[0016] Optionally, the method for constructing an ionosphere-free combination model for low-earth orbit / user single-difference calculation and performing differencing on the observation results of two GNSS satellites to obtain a double-difference observation equation is as follows:

[0017]

[0018] where Δ represents the difference between the observed values of two navigation satellites, represents the difference between the observed values of the low-earth orbit and the user, and the subscript IF represents the ionosphere-free combination.

[0019] Optionally, the method for obtaining a combined observation equation using a low-earth orbit constellation is as follows:

[0020]

[0021] where the subscript leo represents the low-earth orbit satellite number, ranging from 1 to m, with a total of m low-earth orbit satellites; the superscripts s1, j1 represent two GNSS satellites, the former represents the reference satellite, and the one with the largest elevation angle among the common-view satellites is selected, and the latter ranges from 1 to n, with a total of n non-reference satellites; Δ(Z HD m hyd ) s1,j1 represents the inter-satellite single difference of the dry delay; represents the inter-satellite single difference of the tropospheric parameter to be estimated.

[0022] Optionally, the method for constructing a double-difference observation equation after eliminating the ionospheric influence in the carrier observation equation is as follows:

[0023]

[0024] where λ represents the signal wavelength, the subscripts g, leo represent the ground station and the low-earth orbit satellite respectively, the subscript IF represents the ionosphere-free combination, the superscripts s, j represent GNSS satellites with different numbers, Δ represents the difference between the observed values of two navigation satellites, It represents the difference between the low-earth orbit and user observations. L is the carrier-phase observation, N represents the integer ambiguity, ρ represents the geometric distance, T represents the tropospheric delay at the user end, and ω represents the sum of the observation noises.

[0025] Optionally, the method for obtaining the raw Doppler measurement of receiver r for satellite s at frequency n is as follows:

[0026]

[0027] where, is the Doppler measurement; is the nominal transmit frequency of satellite s at the nth frequency + the frequency correction term in the navigation information; v s is the satellite's three-dimensional velocity vector; v r is the receiver's three-dimensional velocity vector; e is the direction vector of the satellite pointing to the receiver; df r，n is the receive frequency correction term caused by the receiver clock instability; is the Doppler measurement noise.

[0028] Optionally, the method for obtaining the error equation of the Doppler measurement at frequency j is as follows:

[0029]

[0030] where, is the receiver clock drift, is the theoretical measurement value of the receiver signal frequency, is the sum of the satellite nominal transmit frequency and the frequency correction term in the navigation information.

[0031] Optionally, the method for obtaining the user's acceleration in the ECEF coordinate system by passing the accelerometer measurement results through the specific force equation is as follows:

[0032] where, is the user's motion acceleration, f is the accelerometer measurement value, is the Coriolis acceleration, ω en ×V en is the centripetal acceleration generated by the carrier's rotation relative to the earth, and g is the local gravitational acceleration.

[0033] Optionally, the method for obtaining the acceleration in the northeast-down directions based on the acceleration in the ECEF coordinate system is as follows:

[0034]

[0035] where, V E 、V N 、V U respectively represent the velocities in the northeast-down directions, fE , f N , f U respectively represent the forces (per unit mass) in the three directions of northeast and sky. L represents the local latitude, and R M represents the prime curvature radius of the meridian, and R N represents the prime curvature radius of the prime vertical, and ω ie represents the angular velocity of the Earth's rotation.

[0036] Optionally, the method for obtaining the user's position by integrating and calculating the accelerations in the three directions of northeast and sky is as follows:

[0037]

[0038] Among them, the subscript 0 represents the initial position, and V E , V N , V U respectively represent the velocities in the three directions of northeast and sky. L, λ, and h respectively represent latitude, longitude, and altitude, and R M represents the prime curvature radius of the meridian, and R N represents the prime curvature radius of the prime vertical.

[0039] Technical effects of the present invention: The present invention discloses a fast convergence method applicable to satellite-ground RTK when changing satellites. By performing double-difference calculations using the on-board Beidou / GNSS observations of low-orbit satellites and the Beidou / GNSS observations of user terminals, the problem that traditional RTK technology highly depends on ground base stations is solved, and it can meet the requirements of full-space coverage and high-quality monitoring in some remote areas where it is not easy to establish base stations; taking the user's position and tropospheric parameters as constraints can quickly fix the integer ambiguity when changing satellites in satellite-ground RTK, realizing continuous service of satellite-ground RTK. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings constituting a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0041] Figure 1 is a schematic flow chart of a fast convergence method applicable to satellite-ground RTK when changing satellites according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The following will refer to the drawings and combine the embodiments to detail this application.

[0043] It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. And although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0044] As Figure 1 shown, in this embodiment, a fast convergence method applicable to satellite-ground RTK when changing satellites is provided, including: GNSS constellation, low-earth orbit satellite constellation, user terminal. The specific steps are as follows:

[0045] Step (1) When satellite-ground RTK is operating normally, the low-earth orbit constellation receives the uplink information from the ground station, and uses the inter-satellite link to achieve the relative time synchronization of the low-earth orbit constellation. Generate and broadcast navigation augmentation information and on-board GNSS observations; the user terminal receives and processes the navigation augmentation information and on-board GNSS observations broadcast by the low-earth orbit satellites, and at the same time processes the navigation information, pseudo-range and carrier-phase observations broadcast by the GNSS satellites to obtain an observation file; based on the precise orbit and clock offset information of the low-earth orbit satellites, combined with the regional atmospheric delay model, perform carrier-phase differential least-squares solution on the on-board observations and ground observations to obtain the user position information.

[0046] Step (2) During satellite change, for stationary users, when fixed using the previous reference station, the position information solved by this reference station can be directly used as a constraint. Since the troposphere is highly correlated with the user terminal position, and the low-earth orbit satellites are not affected by tropospheric errors, only the tropospheric parameters of the user terminal need to be estimated. The tropospheric parameters can follow the results of the previous epoch.

[0047] Step (3) During satellite change, for low-dynamic users, the user position during satellite change can be extrapolated using GNSS speed measurement, and the position accuracy can be guaranteed in a short time. Use the extrapolated position information as a constraint. Similarly, the tropospheric parameters can follow the results of the previous epoch.

[0048] Step (4) During satellite change, in the case of high dynamics, the user terminal carries an IMU device. The accuracy of the displacement can be ensured in a short time. Use the INS algorithm of the inertial navigation device to obtain the position information. The tropospheric parameters follow the results solved in the previous epoch.

[0049] Furthermore, the specific manner of step (1) is:

[0050] (101) Taking one low-earth orbit satellite as an example, first establish the GNSS observation equation of the user terminal and the low-earth orbit satellite:

[0051]

[0052] Wherein, P and L respectively represent the pseudorange and carrier phase observations. The subscripts g and leo respectively represent the ground station and the low-earth orbit satellite, and the superscripts s and j respectively represent GNSS satellites with different numbers. and respectively represent the geometric distances between the navigation satellite and the user terminal and the centroid of the low-earth orbit satellite. c is the speed of light in vacuum, and δt g 、δt leo 、δt s respectively represent the clock biases of the user terminal, the low-earth orbit satellite, and the navigation satellite. λ represents the signal wavelength. respectively represent the ionospheric delays of the user terminal and the low-earth orbit satellite. represents the tropospheric delay of the user terminal. respectively represent the integer ambiguities of the user terminal and the low-earth orbit satellite. and respectively represent the sum of the multipath effects and the observation noises of the pseudorange and the carrier phase.

[0053] (102) Construct an ionosphere-free combination model to eliminate the influence of the ionospheric delay, perform the low-earth orbit / user single-difference calculation, and then perform the difference on the observation results of two GNSS satellites to obtain the double-difference observation equation:

[0054]

[0055] Wherein, Δ represents the difference of the observations between two navigation satellites. represents the difference of the observations between the low-earth orbit and the user. The subscript IF represents the ionosphere-free combination.

[0056] (103) The above steps are the calculation process of a single low-earth orbit satellite. Using the low-earth orbit constellation, the following combined observation equation is obtained:

[0057]

[0058] Wherein, the subscript leo represents the number of the low-earth orbit satellite, ranging from 1 to m, with a total of m low-earth orbit satellites; the superscripts s1 and j1 represent two GNSS satellites. The former represents the reference satellite, and the one with the largest elevation angle among the common-view satellites is selected. The latter ranges from 1 to n, with a total of n non-reference satellites; Δ(Z HD m hyd ) s1，j1 represents the inter-satellite single difference of the dry delay. represents the inter-satellite single difference of the tropospheric parameter to be estimated.

[0059] (104) Use the observation data of multiple navigation satellites to solve the observation equation in step (103), and perform multiple iterations to obtain the least squares optimal solution, so as to determine the position coordinates of the user terminal.

[0060] Furthermore, the specific method of step (2) is as follows:

[0061] (201) As known from step (1), the double-difference observation equation after eliminating the ionospheric influence in the carrier observation equation is:

[0062] (202) The user terminal is stationary, so the user position can adopt the result solved by the previous reference station, and the standard deviation is set to 0.1m.

[0063] (203) The low-earth orbit satellite is not affected by the tropospheric error. Only the tropospheric parameters of the user terminal need to be estimated, and the tropospheric parameters solved in the previous epoch can be adopted.

[0064] (204) Substitute the user position and tropospheric parameters into the double-difference observation equation to complete the initialization of the integer ambiguity.

[0065] Furthermore, the specific method of step (3) is as follows:

[0066] (301) For the original Doppler measurement value of satellite s of receiver I at frequency point n is:

[0067]

[0068] where, is the Doppler measurement value, with the unit of Hz; is the nominal emission frequency of satellite s at the nth frequency + the frequency correction term in the navigation information; v s is the three-dimensional velocity vector of the satellite, obtained from the satellite ephemeris; v r is the three-dimensional velocity vector of the receiver, which needs to be estimated; e is the direction vector of the satellite pointing to the receiver; df r，n is the receiving frequency correction term caused by the instability of the receiver clock; is the Doppler measurement noise.

[0069] (302) For the Doppler measurement of frequency point j, there is the following error equation:

[0070]

[0071] where, is the receiver clock drift, is the theoretical measurement value of the receiver signal frequency, is the sum of the nominal emission frequency of the satellite and the frequency correction term in the navigation information.

[0072] (303) Given the Doppler measurements of n satellites, write the above error equation in matrix form:

[0073] E(v) = BX - l

[0074] Among them, Assume the weight matrix is P. According to the least squares criterion, it can be solved that X = (XB T PB) -1 B T Pl.

[0075] (304) Integrate the Doppler velocity measurement results to obtain the user's position during satellite handover, with a standard deviation of 5m. Substitute the user's position and tropospheric parameters into the double-difference observation equation to complete the initialization of the integer ambiguity.

[0076] Furthermore, the specific method of step (4) is as follows:

[0077] (401) Obtain the user's acceleration in the ecef coordinate system from the accelerometer measurement results through the specific force equation:

[0078]

[0079] Among them is the user's motion acceleration, f is the measurement value of the accelerometer, 2ω ie ×V en is the Coriolis acceleration, ω en ×V en is the centripetal acceleration generated by the relative rotation of the carrier to the earth, and g is the local gravitational acceleration.

[0080] (402) Expand the above formula to obtain the accelerations in the northeast and up directions:

[0081]

[0082] (403) The acceleration is integrated to calculate the user's position. Since the integration time is short, the integration cumulative error is small and does not require Kalman filtering for correction:

[0083]

[0084] For high-dynamic users, the standard deviation of their position parameters is 50m.

[0085] (404) Substitute the user's position and tropospheric parameters into the double-difference observation equation to complete the initialization of the integer ambiguity.

[0086] The present invention discloses a fast convergence method applicable to satellite-ground RTK when switching satellites. By performing double-difference calculation using the on-board Beidou / GNSS observations of low-earth orbit satellites and the Beidou / GNSS observations of user terminals, the problem that traditional RTK technology highly depends on ground base stations is solved, and it can meet the requirements of full-space coverage, high-quality monitoring, etc. in some remote areas where it is not easy to establish base stations. Taking the user position and tropospheric parameters as constraints can quickly fix the integer ambiguity when switching satellites in satellite-ground RTK, realizing continuous service of satellite-ground RTK.

[0087] The above are only the preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A fast convergence method suitable for satellite-to-ground RTK satellite switching, characterized in that: include: Construct GNSS observation equations for user terminals and low-orbit satellites, construct an ionosphere-free combined model to perform low-orbit / user single-difference calculations, perform differential calculations on the observation results of two GNSS satellites to obtain double-difference observation equations, use the low-orbit constellation to obtain a combined observation equation, use observation data from multiple navigation satellites to solve the combined observation equation, and iterate multiple times to obtain the least squares optimal solution to determine the user terminal position coordinates; Construct the double difference observation equation after eliminating the influence of ionosphere by carrier observation equation; The user terminal is stationary, and the user position continues to use the result solved by the previous reference station; Estimate the tropospheric parameters of the user terminal, using the tropospheric parameters solved in the previous epoch; substitute the user position and the tropospheric parameters into the double difference observation equation after eliminating the influence of the ionosphere, and complete the initialization of the integer ambiguity; Obtain the original Doppler measurement value of the receiver r satellite s at the frequency point n; obtain the error equation of the Doppler measurement at the frequency point j; perform Doppler measurement on a number of satellites and convert the error square into a matrix form; integrate the Doppler velocity measurement results to obtain the user position during the satellite change, bring the user position and the tropospheric parameters into the double difference observation equation, and complete the initialization of the integer ambiguity; The accelerometer measurement results are passed through the specific force equation to obtain the acceleration of the user in the ecef coordinate system; the acceleration in the three directions of northeast and sky is obtained based on the acceleration in the ecef coordinate system; the acceleration in the three directions of northeast and sky is integrated and extrapolated to obtain the user position; the user position and the tropospheric parameters are substituted into the double difference observation equation to complete the initialization of the integer ambiguity.

2. The fast convergence method for satellite-to-ground RTK satellite switching as claimed in claim 1, characterized in that: The method for constructing the GNSS observation equations for user terminals and low-orbit satellites is: Among them, P and L represent pseudorange and carrier phase observation values, respectively. The subscripts g and leo represent ground stations and low-orbit satellites, respectively. The superscripts s and j represent GNSS satellites with different numbers, respectively. and represents the geometric distance between the navigation satellite and the user terminal and the mass center of the low-orbit satellite, c is the speed of light in vacuum, δt g ,δt leo ,δt s Respectively represent the clock errors of the user terminal, low-orbit satellite, and navigation satellite, λ represents the signal wavelength, Represent the ionospheric delay of the user end and the low-orbit satellite, represents the tropospheric delay at the user end, Represent the integer ambiguity of the user end and the low-orbit satellite, and Represent the sum of multipath effect and observation noise of pseudorange and carrier phase respectively.

3. The fast convergence method for satellite-to-ground RTK satellite switching as claimed in claim 1, characterized in that: The method of constructing an ionosphere-free combined model for low-orbit / user single-difference calculation and performing differential calculation on the observation results of two GNSS satellites to obtain the double-difference observation equation is as follows: Among them, Δ represents the difference between the observation values ​​of two navigation satellites. It indicates the difference between low orbit and user observations, and the subscript IF indicates the ionosphere-free combination.

4. The fast convergence method for satellite-to-ground RTK satellite switching as claimed in claim 1, characterized in that: The method to obtain the combined observation equation using the low-orbit constellation is: Wherein, the subscript leo indicates the low-orbit satellite number, ranging from 1 to m, with a total of m low-orbit satellites; the superscripts s1 and j1 indicate two GNSS satellites, the former indicating the reference satellite, which selects the satellite with the largest elevation angle among the common-view satellites, and the latter ranging from 1 to n, with a total of n non-reference satellites; Δ(Z HD m hyd ) s1,j1 It represents the single difference of the intersatellite delay; Represents the inter-satellite single difference of the tropospheric parameters to be estimated.

5. The fast convergence method for satellite-to-ground RTK satellite switching as claimed in claim 1, characterized in that: The double difference observation equation method after constructing the carrier observation equation to eliminate the influence of the ionosphere is: Among them, λ represents the signal wavelength, subscripts g and leo represent ground stations and low-orbit satellites respectively, subscript IF represents ionosphere-free combination, superscripts s and j represent GNSS satellites with different numbers respectively, and Δ represents the difference between the observation values ​​of two navigation satellites. It represents the difference between the low orbit and user observation values, L is the carrier phase observation value, N represents the integer ambiguity, ρ represents the distance, T represents the tropospheric delay at the user end, and ω represents the sum of the observation noise.

6. The fast convergence method for satellite-to-ground RTK satellite switching as claimed in claim 1, characterized in that: The method to obtain the original Doppler measurement value of satellite s at receiver r at frequency point n is: in, is the Doppler measurement value; is the nominal transmission frequency of satellite s at the nth frequency + the frequency correction term in the navigation information; v s is the satellite's three-dimensional velocity vector; v r is the three-dimensional velocity vector of the receiver; e is the direction vector of the satellite pointing to the receiver; df r，n It is the receiving frequency correction item caused by the instability of the receiver clock; is the Doppler measurement noise.

7. The fast convergence method for satellite-to-ground RTK satellite switching as claimed in claim 1, characterized in that: The method to obtain the error equation of the Doppler measurement at frequency point j is: in, is the receiver clock drift, is the theoretical measured value of the receiver signal frequency, It is the sum of the satellite's nominal transmission frequency and the frequency correction term in the navigation information.

8. The fast convergence method for satellite-to-ground RTK satellite switching as claimed in claim 1, characterized in that: The method of using the accelerometer measurement results through the specific force equation to obtain the user's acceleration in the ecef coordinate system is: in, is the user's motion acceleration, f is the accelerometer's measurement value, 2ω ie ×V en is the Coriolis acceleration, ω en ×V en is the centripetal acceleration caused by the rotation of the carrier relative to the earth, and g is the local gravitational acceleration.

9. The fast convergence method for satellite-to-ground RTK satellite switching as claimed in claim 1, characterized in that: The method for obtaining the acceleration in the three directions of the northeast and the sky based on the acceleration in the ecef coordinate system is: Among them, V E 、V N 、V U Represents the speed in the three directions of northeast sky, f E 、f N 、f U They represent the forces in the three directions of northeast and northeast, L represents the local latitude, R M Represents the principal radius of curvature of the meridian, R N represents the principal radius of curvature of the y-axis circle, ω ie Represents the angular velocity of the Earth's rotation.

10. The fast convergence method for satellite-to-ground RTK satellite switching as claimed in claim 1, characterized in that: The method of integrating and calculating the acceleration in the three directions of the northeast and the sky to obtain the user's position is as follows: Among them, the subscript 0 represents the initial position, V E 、V N 、V U They represent the speed in the three directions of the northeast sky, L, λ, and h represent latitude, longitude, and altitude, respectively. M Represents the principal radius of curvature of the meridian, R N Represents the principal curvature radius of the Maoyou circle.

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