A low earth orbit satellite-based differential positioning method, device and storage medium

Abstract

The application relates to the field of satellite positioning technology, and provides a differential positioning method, device and storage medium based on low-orbit satellites, which comprises the following steps: determining a reference station and a mobile station; determining a differential positioning observation relationship and a differential positioning estimation relationship according to the difference value of the position information of each low-orbit satellite at the starting moment and the ending moment of a Doppler counting period, the position information of the reference station, the real position information of the mobile station and the local oscillator frequency of the reference station and the mobile station; determining the error between the approximate position information of the mobile station and the real position information of the mobile station according to the differential positioning observation relationship and the differential positioning estimation relationship; and correcting the approximate position information of the mobile station according to the error, so that the approximate position information of the mobile station tends to the real position information of the mobile station, thereby realizing the positioning of the mobile station. The scheme can realize the positioning in a single Doppler observation period and can improve the positioning accuracy.

Description

Technical Field

[0001] The present invention relates to the field of satellite positioning technology, and specifically to a differential positioning method, device and storage medium based on low-orbit satellites, and more particularly to a differential positioning method, device and storage medium based on the Doppler frequency of low-orbit satellites. Background Art

[0002] Currently, the number of low-orbit satellites in orbit is exploding, and announced low-orbit satellite constellation plans still have a large number of satellite launches. Against this backdrop, the use of low-orbit satellites for navigation and positioning applications is poised for new breakthroughs. However, the accuracy of navigation and positioning using low-orbit satellites is affected by the influence of satellite clock errors and receiver clock errors.

[0003] Therefore, there is an urgent need to develop a differential positioning method, device and storage medium based on the Doppler frequency of low-orbit satellites, which can achieve positioning in a single Doppler observation cycle and improve the accuracy of positioning. Summary of the Invention

[0004] The purpose of the present invention is to provide a differential positioning method, device and storage medium based on low-orbit satellites, so as to achieve positioning in a single Doppler observation cycle and improve the accuracy of positioning.

[0005] In order to solve the above technical problems, as one aspect of the present invention, a differential positioning method based on low-orbit satellites is provided, which is used to realize differential positioning based on the Doppler frequency of low-orbit satellites, and the number of observations of the low-orbit satellites is n times, and n is a positive integer greater than or equal to 1; the differential positioning method based on low-orbit satellites includes the following steps: determining a reference station and a mobile station; the reference station and the mobile station can simultaneously receive the signal transmitted by each low-orbit satellite in the low-orbit satellites; and the reference station can transmit its own observation information and prior information to the mobile station; obtaining the position information of the reference station; obtaining the approximate coordinates of the mobile station; obtaining the local oscillation frequency of the reference station and the mobile station; and obtaining the number of each low-orbit satellite in the low-orbit satellites; determining the real position information of the mobile station according to the approximate coordinates of the mobile station; according to the number of each low-orbit satellite in the low-orbit satellites, The difference between the position information of each low-orbit satellite at the start and end times of a Doppler counting cycle, the position information of the base station, the true position information of the mobile station, and the local oscillation frequencies of the reference station and the mobile station are used to determine an observation relationship for differential positioning based on the low-orbit satellite Doppler frequency, which is recorded as a differential positioning observation relationship; and an estimation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, which is recorded as a differential positioning estimation relationship; based on the differential positioning observation relationship and the differential positioning estimation relationship, the error between the approximate position information of the mobile station and the true position information of the mobile station is determined; based on the error between the approximate position information of the mobile station and the true position information of the mobile station, the approximate position information of the mobile station is corrected so that the approximate position information of the mobile station approaches the true position information of the mobile station, thereby realizing the positioning of the mobile station.

[0006] According to an exemplary embodiment of the present invention, the real position information of the mobile station is determined according to the approximate coordinates of the mobile station; according to the number of each low-orbit satellite in the low-orbit satellite, the difference between the position information of each low-orbit satellite at the start time and the end time of a Doppler counting cycle, the position information of the base station, the real position information of the mobile station, and the local oscillator frequency of the reference station and the mobile station, the observation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, which is recorded as the differential positioning observation relationship; and the estimation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined. The relationship is recorded as a differential positioning estimation relationship, including: according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, according to the difference in position information of the low-orbit satellite with the number at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the mobile station for the position of the low-orbit satellite with the number in the Doppler counting cycle, determining the observation relationship of the measured distance difference of the mobile station to the low-orbit satellite with the number; according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, according to the difference in position information of the low-orbit satellite with the number at the start time and the end time of a Doppler counting cycle The difference between the position information of the start time and the end time of the Doppler counting cycle and the Doppler count value of the position of the low-orbit satellite with the number at the reference station within the Doppler counting cycle is used to determine the observation relationship of the measured distance difference of the low-orbit satellite with the number at the reference station; according to the number of each low-orbit satellite in the low-orbit satellite, for each numbered low-orbit satellite, according to the observation relationship of the measured distance difference of the low-orbit satellite with the number at the mobile station and the observation relationship of the measured distance difference of the low-orbit satellite with the number at the reference station, after eliminating the satellite clock error, the single difference distance of the low-orbit satellite with the number is obtained. relationship; according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the single-difference distance relationship of low-orbit satellites with different numbers, after eliminating the receiver clock error, the observation relationship for differential positioning based on the low-orbit satellite Doppler frequency is obtained, which is recorded as the differential positioning observation relationship; according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the position information of low-orbit satellites with different numbers at the start time and end time of a Doppler counting cycle, the estimation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, which is recorded as the differential positioning estimation relationship.

[0007] According to an exemplary embodiment of the present invention, according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, according to the difference in position information of the numbered low-orbit satellite at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the mobile station for the position of the numbered low-orbit satellite within the one Doppler counting cycle, determining the observation relationship of the mobile station with respect to the measured distance difference of the numbered low-orbit satellite, including: determining the observation relationship of the mobile station with respect to the measured distance difference of the numbered low-orbit satellite according to formula (1):

[0008]

[0009] In formula (1), j represents the number of the low-orbit satellite; T i = t i -t i-1 represents a Doppler counting period; λ = f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, and C is the speed of light; Δf = f r -f t is the frequency difference, f t represents the transmission signal frequency of the low-orbit satellite j; σt R0 represents the receiver clock difference of the mobile station to the position of the low-orbit satellite j, σt j represents the satellite clock difference; represents the Doppler counting observation value of the mobile station to the low-orbit satellite j; and / or, according to the position information of each low-orbit satellite in the low-orbit satellites at the start time and the end time of a Doppler counting period, and the Doppler counting value of the reference station to the position of the low-orbit satellite in the low-orbit satellites in the one Doppler counting period, the observation relationship of the reference station to the measurement distance difference of the low-orbit satellite is determined according to the number of the low-orbit satellite, for each numbered low-orbit satellite, including: according to formula (2), the observation relationship of the reference station to the measurement distance difference of the low-orbit satellite is determined:

[0010]

[0011] In formula (2), j represents the number of the low-orbit satellite; T i = t i -t i-1 represents a Doppler counting period; λ = f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, and C is the speed of light; Δf = f r -f t is the frequency difference, f t represents the transmission signal frequency of the low-orbit satellite j; σt B0 represents the receiver clock difference of the reference station to the position of the low-orbit satellite j, σt j represents the satellite clock difference; represents the Doppler counting observation value of the reference station to the low-orbit satellite j; represents the measurement distance difference of the reference station to the low-orbit satellite j.

[0012] According to an example embodiment of the present application, according to the observation relation of the measured distance difference of the mobile station to each numbered low-orbit satellite and the observation relation of the measured distance difference of the reference station to each numbered low-orbit satellite, after eliminating the satellite clock error, a single-difference distance relation of each numbered low-orbit satellite is obtained, including: according to the observation relation of the measured distance difference of the mobile station to each numbered low-orbit satellite and the observation relation of the measured distance difference of the reference station to each numbered low-orbit satellite, after eliminating the satellite clock error, a single-difference distance relation of each numbered low-orbit satellite is obtained by making a single-difference between stations; wherein the single-difference distance relation of each numbered low-orbit satellite is as shown in formula (3):

[0013]

[0014] In formula (3), j represents the number of the low-orbit satellite; represents the measured distance difference of the mobile station to the low-orbit satellite j, represents the measured distance difference of the reference station to the low-orbit satellite j; λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, C is the speed of light; σt R0 represents the receiver clock error of the mobile station to the position of the low-orbit satellite j, σt B0 represents the receiver clock error of the reference station to the position of the low-orbit satellite j; represents the Doppler count observation value of the mobile station to the low-orbit satellite j, represents the Doppler count observation value of the reference station to the low-orbit satellite j.

[0015] According to an example embodiment of the present application, according to the single-difference distance relation of different numbered low-orbit satellites, after eliminating the receiver clock error, an observation relation for differential positioning based on the Doppler frequency of the low-orbit satellite is obtained, which is recorded as a differential positioning observation relation, including: according to the single-difference distance relation of different numbered low-orbit satellites, after eliminating the receiver clock error, an observation relation for differential positioning based on the Doppler frequency of the low-orbit satellite is obtained by making a single-difference between stars, which is recorded as a differential positioning observation relation; wherein the differential positioning observation relation is as shown in formula (4):

[0016]

[0017] In formula (4), j and k represent different numbers of the low-orbit satellite; T i =t i -t i-1 , represents a Doppler count period; represents the measured distance difference between the mobile station and the low-orbit satellite j, represents the measured distance difference between the reference station and the low-orbit satellite j; represents the measured distance difference between the mobile station and the low-orbit satellite k, represents the measured distance difference between the base station and the low-orbit satellite k; λ = f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, and C is the speed of light; represents the Doppler count observation value of the mobile station to the low-orbit satellite j, represents the Doppler count observation value of the base station to the low-orbit satellite j, represents the Doppler count observation value of the mobile station to the low-orbit satellite k, It represents the Doppler count observation value of the base station for the low-orbit satellite k.

[0018] According to an exemplary embodiment of the present invention, according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the position information of the low-orbit satellites with different numbers at the start time and the end time of a Doppler counting cycle, an estimation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, which is recorded as a differential positioning estimation relationship, including: recording the error between the approximate position information of the mobile station and the true position information of the mobile station as a coordinate value (ΔX, ΔY, ΔZ), and recording the starting time t of the low-orbit satellite j and the low-orbit satellite k in a Doppler counting cycle. i-1 and end time t i The positions at the time are the coordinate values Coordinate values and coordinate values Coordinate values For formula (4), let ΔL * =Equal to the left side of formula (4), the approximate coordinates of the mobile station R and the sum of the errors (X R1 +ΔX,Y R1 +ΔY,Z R1 +ΔZ), the real coordinates of the base station (X B0 , Y B0 , Z B0 ) and satellites j and k at t i-1 and t i The coordinate value at the time is the approximate coordinate value (X R1 , Y R1 , Z R1 ) is expanded using the Taylor formula to obtain the estimated relationship for differential positioning based on the Doppler frequency of the low-orbit satellite, which is recorded as the differential positioning estimation relationship; wherein, the differential positioning estimation relationship is formula (5):

[0019]

[0020] According to an example embodiment of the present invention, the error between the approximate position information of the mobile station and the actual position information of the mobile station is determined based on the differential positioning observation relationship and the differential positioning estimation relationship, including: subtracting the differential positioning observation relationship and the differential positioning estimation relationship to minimize the sum of squared residuals, and using the least squares method to estimate the estimated value of the error between the approximate position information of the mobile station and the actual position information of the mobile station; when two low-orbit satellites are observed, the error between the approximate position information of the mobile station and the actual position information of the mobile station is determined based on the estimated value of the error between the approximate position information of the mobile station and the actual position information of the mobile station under three Doppler counting cycles.

[0021] According to an example embodiment of the present invention, the approximate location information of the mobile station is corrected according to the error between the approximate location information of the mobile station and the actual location information of the mobile station, so that the approximate location information of the mobile station approaches the actual location information of the mobile station, thereby realizing the positioning of the mobile station, including: correcting the approximate location information of the mobile station according to the error between the approximate location information of the mobile station and the actual location information of the mobile station; re-determining the error between the approximate location information of the mobile station and the actual location information of the mobile station, and correcting the approximate location information of the mobile station according to the error between the re-determined approximate location information of the mobile station and the actual location information of the mobile station; iterating in this manner until the approximate location information of the mobile station approaches the actual location information of the mobile station, thereby realizing the positioning of the mobile station.

[0022] As a second aspect of the present invention, the present invention provides a differential positioning device based on low-orbit satellites, which is used to realize differential positioning based on the Doppler frequency of low-orbit satellites, wherein the number of observations of the low-orbit satellites is n times, and n is a positive integer greater than or equal to 1; the differential positioning device based on low-orbit satellites comprises the following steps: a control unit is configured to determine a base station and a mobile station; the base station and the mobile station can simultaneously receive signals transmitted by each low-orbit satellite in the low-orbit satellites; and the base station can transmit its own observation information and prior information to the mobile station; an acquisition unit is configured to acquire the position information of the base station; acquire the approximate coordinates of the mobile station; acquire the local oscillation frequency of the base station and the mobile station; and acquire the number of each low-orbit satellite in the low-orbit satellites; the control unit is further configured to determine the real position information of the mobile station according to the approximate coordinates of the mobile station; according to the number of each low-orbit satellite in the low-orbit satellites, The method comprises the following steps: determining an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite according to the difference in position information between the starting time and the ending time of a Doppler counting cycle of the low-orbit satellite, the position information of the base station, the real position information of the mobile station, and the local oscillation frequency of the reference station and the mobile station, which is recorded as the differential positioning observation relationship; and determining an estimation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite, which is recorded as the differential positioning estimation relationship; the control unit is further configured to determine the error between the approximate position information of the mobile station and the real position information of the mobile station according to the differential positioning observation relationship and the differential positioning estimation relationship; and the control unit is further configured to correct the approximate position information of the mobile station according to the error between the approximate position information of the mobile station and the real position information of the mobile station, so that the approximate position information of the mobile station approaches the real position information of the mobile station, thereby realizing the positioning of the mobile station.

[0023] According to an exemplary embodiment of the present invention, the control unit determines the real position information of the mobile station based on the approximate coordinates of the mobile station; according to the number of each low-orbit satellite in the low-orbit satellite, according to the difference between the position information of each low-orbit satellite at the start time and the end time of a Doppler counting cycle, the position information of the base station, the real position information of the mobile station, and the local oscillator frequency of the reference station and the mobile station, determines the observation relationship for differential positioning based on the low-orbit satellite Doppler frequency, which is recorded as the differential positioning observation relationship; and determines the observation relationship for differential positioning based on the low-orbit satellite Doppler frequency. The estimated relationship of positioning is recorded as a differential positioning estimation relationship, including: according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, according to the difference in position information of the low-orbit satellite with the number at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the mobile station for the position of the low-orbit satellite with the number within the one Doppler counting cycle, determining the observation relationship of the measured distance difference of the mobile station to the low-orbit satellite with the number; according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, according to the difference in position information of the low-orbit satellite with the number at the start time and the end time of a Doppler counting cycle The difference between the position information of the start time and the end time of the Doppler counting cycle and the Doppler count value of the reference station for the position of the low-orbit satellite with the number in the Doppler counting cycle is used to determine the observation relationship of the measured distance difference of the low-orbit satellite with the number by the reference station; according to the number of each low-orbit satellite in the low-orbit satellite, for each numbered low-orbit satellite, according to the observation relationship of the measured distance difference of the low-orbit satellite with the number by the mobile station and the observation relationship of the measured distance difference of the low-orbit satellite with the number, after eliminating the satellite clock error, the single distance difference of the low-orbit satellite with the number is obtained. According to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the single-difference distance relationship between low-orbit satellites with different numbers, after eliminating the receiver clock error, an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite is obtained, which is recorded as the differential positioning observation relationship; according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the position information of low-orbit satellites with different numbers at the start time and end time of a Doppler counting cycle, an estimation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite is determined, which is recorded as the differential positioning estimation relationship.

[0024] According to an exemplary embodiment of the present invention, the control unit determines, according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, based on the difference in position information of the numbered low-orbit satellite at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the mobile station for the position of the numbered low-orbit satellite within the Doppler counting cycle, the observation relationship of the mobile station to the measured distance difference of the numbered low-orbit satellite, including: determining the observation relationship of the mobile station to the measured distance difference of the numbered low-orbit satellite according to formula (1):

[0025]

[0026] In formula (1), j represents the number of the low-orbit satellite; T i =t i -t i-1 , represents a Doppler counting cycle; λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, C is the speed of light; Δf=f r -f t is the frequency difference, f t represents the transmission signal frequency of low-orbit satellite j; σt R0 represents the receiver clock error of the mobile station relative to the position of low-orbit satellite j, σt j represents the satellite clock error; represents a Doppler count observation value of the mobile station for the low-orbit satellite j; and / or, the control unit, according to the number of each low-orbit satellite, for each numbered low-orbit satellite, according to the difference in position information of the low-orbit satellite with the number at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the position of the low-orbit satellite with the number by the reference station within the one Doppler counting cycle, determines the observation relationship of the reference station for the measured distance difference of the low-orbit satellite with the number, including: determining the observation relationship of the reference station for the measured distance difference of the low-orbit satellite with the number according to formula (2):

[0027]

[0028] In formula (2), j represents the number of the low-orbit satellite; T i =t i -t i-1 , represents a Doppler counting cycle; λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, C is the speed of light; Δf=f r -f t is the frequency difference, f t represents the transmission signal frequency of low-orbit satellite j; σtB0 represents the receiver clock error of the reference station to the position of low-orbit satellite j, σt j represents the satellite clock error; represents the Doppler count observation value of the reference station to the low-orbit satellite j; It represents the distance difference measured by the base station to the low-orbit satellite j.

[0029] According to an example embodiment of the present invention, the control unit, according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, eliminates the satellite clock error based on the observation relationship of the measured distance difference of the mobile station for the numbered low-orbit satellite and the observation relationship of the measured distance difference of the reference station for the numbered low-orbit satellite, and obtains the single-difference distance relationship of the numbered low-orbit satellite. The method includes: according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, performing inter-station single difference on the observation relationship of the measured distance difference of the mobile station for the numbered low-orbit satellite and the observation relationship of the measured distance difference of the reference station for the numbered low-orbit satellite, eliminating the satellite clock error, and obtaining the single-difference distance relationship of the numbered low-orbit satellite. The single-difference distance relationship of each numbered low-orbit satellite is as shown in formula (3):

[0030]

[0031] In formula (3), j represents the number of the low-orbit satellite; represents the measured distance difference between the mobile station and the low-orbit satellite j, represents the measured distance difference between the reference station and the low-orbit satellite j; λ = f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, C is the speed of light; σt R0 represents the receiver clock error of the mobile station relative to the position of low-orbit satellite j, σt B0 represents the receiver clock error of the reference station relative to the position of low-orbit satellite j; represents the Doppler count observation value of the mobile station to the low-orbit satellite j, It represents the Doppler count observation value of the reference station to the low-orbit satellite j.

[0032] According to an exemplary embodiment of the present invention, the control unit, according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the single-difference distance relationship of the low-orbit satellites with different numbers, eliminates the receiver clock error, and obtains an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite, which is recorded as a differential positioning observation relationship. The method includes: according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, performing inter-satellite single difference on the single-difference distance relationship of the low-orbit satellites with different numbers, eliminating the receiver clock error, and obtaining an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite, which is recorded as a differential positioning observation relationship; wherein the differential positioning observation relationship is as shown in formula (4):

[0033]

[0034] In formula (4), j and k represent different numbers of low-orbit satellites; T i =t i -t i-1 , represents a Doppler counting cycle; represents the measured distance difference between the mobile station and the low-orbit satellite j, represents the measured distance difference between the reference station and the low-orbit satellite j; represents the measured distance difference between the mobile station and the low-orbit satellite k, represents the measured distance difference between the base station and the low-orbit satellite k; λ = f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, and C is the speed of light; represents the Doppler count observation value of the mobile station to the low-orbit satellite j, represents the Doppler count observation value of the base station to the low-orbit satellite j, represents the Doppler count observation value of the mobile station to the low-orbit satellite k, It represents the Doppler count observation value of the base station for the low-orbit satellite k.

[0035] According to an exemplary embodiment of the present invention, the control unit determines, according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the position information of low-orbit satellites with different numbers at the start time and the end time of a Doppler counting cycle, an estimated relationship for differential positioning based on the low-orbit satellite Doppler frequency, recorded as a differential positioning estimation relationship, including: recording the error between the approximate position information of the mobile station and the true position information of the mobile station as a coordinate value (ΔX, ΔY, ΔZ), and recording the starting time t of the low-orbit satellite j and the low-orbit satellite k in a Doppler counting cycle. i-1 and end time t i The positions at the time are the coordinate values Coordinate values and coordinate values Coordinate value For formula (4), let ΔL * =Equal to the left side of formula (4), the approximate coordinates of the mobile station R and the sum of the errors (X R1 +ΔX,Y R1 +ΔY,Z R1 +ΔZ), the real coordinates of the base station (X B0 , Y B0 , Z B0 ) and satellites j and k at t i-1 and t i The coordinate value at the time is the approximate coordinate value (X R1 , Y R1 , Z R1 ) is expanded using the Taylor formula to obtain the estimated relationship for differential positioning based on the Doppler frequency of the low-orbit satellite, which is recorded as the differential positioning estimation relationship; wherein, the differential positioning estimation relationship is formula (5):

[0036]

[0037] According to an example embodiment of the present invention, the control unit determines the error between the approximate position information of the mobile station and the actual position information of the mobile station based on the differential positioning observation relationship and the differential positioning estimation relationship, including: subtracting the differential positioning observation relationship and the differential positioning estimation relationship to minimize the sum of squared residuals, and using the least squares method to estimate the estimated value of the error between the approximate position information of the mobile station and the actual position information of the mobile station; when two low-orbit satellites are observed, the error between the approximate position information of the mobile station and the actual position information of the mobile station is determined based on the estimated value of the error between the approximate position information of the mobile station and the actual position information of the mobile station under three Doppler counting cycles.

[0038] According to an example embodiment of the present invention, the control unit corrects the approximate location information of the mobile station according to the error between the approximate location information of the mobile station and the real location information of the mobile station, so that the approximate location information of the mobile station approaches the real location information of the mobile station, thereby realizing positioning of the mobile station, including: correcting the approximate location information of the mobile station according to the error between the approximate location information of the mobile station and the real location information of the mobile station; re-determining the error between the approximate location information of the mobile station and the real location information of the mobile station, and correcting the approximate location information of the mobile station according to the error between the re-determined approximate location information of the mobile station and the real location information of the mobile station; iterating in this manner until the approximate location information of the mobile station approaches the real location information of the mobile station, thereby realizing positioning of the mobile station.

[0039] As a third aspect of the present invention, the present invention provides a storage medium, which includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the above-mentioned differential positioning method based on low-orbit satellites.

[0040] The beneficial effects of the present invention are:

[0041] The solution of the present invention fully considers the influence of satellite clock error and receiver clock error, adopts differential algorithm to eliminate them (i.e. the influence of satellite clock error and receiver clock error), and fully utilizes the advantages of a large number of low-orbit satellites and rapid changes in Doppler frequency. It can achieve positioning in a single Doppler observation period and can improve positioning accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The figure schematically shows the steps of the differential positioning method based on low-orbit satellites.

[0043] Figure 2 The diagram schematically shows the steps of determining the differential positioning observation relationship and the differential positioning estimation relationship in the differential positioning method based on low-orbit satellites.

[0044] Figure 3 The diagram schematically shows the steps for determining the differential positioning estimation relationship in the differential positioning method based on low-orbit satellites.

[0045] Figure 4 The diagram schematically shows the steps of determining the error between the approximate position information of the mobile station and the real position information of the mobile station in the differential positioning method based on low-orbit satellites.

[0046] Figure 5 The diagram schematically shows the steps of making the approximate position information of the mobile station approach the real position information of the mobile station in the differential positioning method based on low-orbit satellites.

[0047] Figure 6 The structure of a differential positioning device based on low-orbit satellites is schematically shown.

[0048] Among them, 102 is an acquisition unit, and 104 is a control unit. DETAILED DESCRIPTION

[0049] The following is a detailed description of embodiments of the present invention, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0050] Considering that compared with traditional GNSS (Global Navigation Satellite System) navigation, the use of low-orbit satellites for navigation and positioning has the following main advantages: (1) the signal-to-noise ratio of the received signal is high, the power is strong, the ionosphere has little influence, and it has strong anti-interference ability; (1-1) the number of low-orbit satellites is large, and the geometric distribution varies greatly, which can improve the properties of the positioning equation and improve the accuracy; (2) the Doppler frequency of low-orbit satellites changes rapidly. By utilizing this property, the real-time performance and accuracy of the Doppler frequency positioning algorithm can be greatly improved.

[0051] In addition, when using low-orbit satellites for navigation and positioning, the accuracy of navigation and positioning using low-orbit satellites will be affected by the influence of satellite clock error and receiver clock error.

[0052] Therefore, the solution of the present invention proposes a differential positioning technology based on the Doppler frequency of low-orbit satellites, which fully considers the influence of satellite clock error and receiver clock error, and adopts a differential algorithm to eliminate them (i.e. the influence of satellite clock error and receiver clock error). It fully utilizes the advantages of the large number of low-orbit satellites and the rapid change of Doppler frequency, can achieve positioning in a single Doppler observation period, and can improve the accuracy of positioning.

[0053] As a first embodiment of the present invention, a differential positioning method based on low-orbit satellites is provided, which is used to achieve differential positioning based on the Doppler frequency of low-orbit satellites. The number of observations of the low-orbit satellites is n times, where n is a positive integer greater than or equal to 1; n represents the number of observations (i.e., Doppler counting cycle), with at least two satellites, and three observations to obtain a positioning result. Figure 1 As shown, the differential positioning method based on low-orbit satellites includes the following steps: Steps S110 to S150. The number of observations can be multiple observations of the same set of satellites, or multiple sets of satellites can be observed at once. Specifically, during differential positioning, Doppler counting observations of visible satellites are performed by the mobile station and the base station to determine the observation equation. Two subtractions are performed solely to eliminate satellite and receiver clock errors. An estimation equation is determined based on the distance difference between the approximate coordinates and the true coordinates. The difference between the two is used to minimize the error.

[0054] In step S110, a reference station and a mobile station are determined. The reference station and the mobile station are capable of simultaneously receiving signals transmitted by each of the low-orbit satellites. Furthermore, the reference station is capable of transmitting its own observation information and a priori information to the mobile station. The a priori information includes the reference station's location coordinates, the local oscillator frequencies fr of the reference station and the mobile station, the satellite signal transmission frequency ft, and the speed of light c, all of which are already known. The observation information includes the Doppler count and satellite position information, which requires real-time observation.

[0055] At step S120, the position information of the reference station is acquired, such as the position information of the reference station being (X B0 , Y B0 , Z B0 ) ; the approximate coordinates of the mobile station are acquired, so as to determine the real position information of the mobile station being (X R0 , Y R0 , Z R0 ) according to the approximate coordinates of the mobile station; the local oscillator frequencies of the reference station and the mobile station are acquired, such as f r ; and the numbers of the low-orbit satellites are acquired, such as the number of the first low-orbit satellite being j, the number of the second low-orbit satellite being k, and so on.

[0056] Specifically, the implementation process of the differential positioning technology based on the low-orbit satellite Doppler frequency according to the scheme of the present application comprises the following steps: step 1, determining the position information (X B0 , Y B0 , Z B0 ) of the reference station and the real position (X R0 , Y R0 , Z R0 ) of the mobile station, determining the local oscillator frequencies f r of the reference station and the mobile station, and determining the numbers j and k of the low-orbit satellites, and then performing step 2 to obtain the observation equation of the Doppler frequency differential positioning and the estimation equation of the Doppler frequency differential positioning.

[0057] In the scheme of the present application, the differential positioning based on the low-orbit satellite Doppler frequency needs a reference station, the position information of which is accurately known and is set as (X B0 , Y B0 , Z B0 ). The position information of the mobile station needs to be estimated, and it is assumed that the real position of the mobile station is (X R0 , Y R0 , Z R0 ) ; the local oscillator frequencies of the reference station and the mobile station are both f r , they simultaneously receive the low-orbit satellite signals, and the reference station can transmit the observation information and the prior information of itself to the mobile station. The numbers of the low-orbit satellites are represented by j and k, the transmission signal frequencies of the low-orbit satellites are f t , and the position information of the low-orbit satellites can be obtained in real time through a TLE (Two-Line Orbital Element) file or an ephemeris file.

[0058] At step S130, the real position information of the mobile station is determined according to the approximate coordinates of the mobile station; according to the number of each low-orbit satellite in the low-orbit satellite, according to the difference in position information of each low-orbit satellite at the start time and the end time of a Doppler counting cycle, the position information of the base station, the real position information of the mobile station, and the local oscillation frequency of the reference station and the mobile station, an observation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, which is recorded as the differential positioning observation relationship; and an estimation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, which is recorded as the differential positioning estimation relationship.

[0059] According to the approximate coordinates of the mobile station, such as the coordinate value (X R1 , Y R1 , Z R1 ), calculate the error (ΔX, ΔY, ΔZ), and then deduct the error to obtain the real position information of the mobile station such as the coordinate value (X R0 , Y R0 , Z R0 ).

[0060] Specifically, the implementation process of a differential positioning technology based on the Doppler frequency of a low-orbit satellite proposed in the solution of the present invention also includes: step 2, determining the observation equation of Doppler frequency differential positioning and the estimation equation of Doppler frequency differential positioning, and then executing step 3 to obtain the approximate coordinates (X R1 , Y R1 , Z R1 ) and the real coordinates (X R0 , Y R0 , Z R0 ) is an estimate of the error (ΔX, ΔY, ΔZ) between .

[0061] In some embodiments, in step S130, the real position information of the mobile station is determined based on the approximate coordinates of the mobile station; according to the number of each low-orbit satellite in the low-orbit satellite, according to the difference in position information of each low-orbit satellite at the start time and the end time of a Doppler counting cycle, the position information of the base station, the real position information of the mobile station, and the local oscillation frequency of the reference station and the mobile station, the observation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, which is recorded as the differential positioning observation relationship; and the estimation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, which is recorded as the differential positioning estimation relationship. For the specific process, please refer to the following exemplary description.

[0062] The following combination Figure 2The flowchart of an embodiment of determining the differential positioning observation relationship and the differential positioning estimation relationship in the method of the present invention further illustrates the specific process of determining the differential positioning observation relationship and the differential positioning estimation relationship in step S130, including: steps S210 to S250.

[0063] Step S210, according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, according to the difference in position information of the low-orbit satellite with the number at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the mobile station for the position of the low-orbit satellite with the number within the one Doppler counting cycle, determine the observation relationship of the mobile station with respect to the measured distance difference of the low-orbit satellite with the number.

[0064] In some embodiments, step S210 determines, according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, based on the difference in position information of the numbered low-orbit satellite at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the mobile station for the position of the numbered low-orbit satellite within the Doppler counting cycle, an observation relationship of the mobile station with respect to the measured distance difference of the numbered low-orbit satellite, including: determining the observation relationship of the mobile station with respect to the measured distance difference of the numbered low-orbit satellite according to formula (1):

[0065]

[0066] In formula (1), j represents the number of the low-orbit satellite; T i =t i -t i-1 , represents a Doppler counting cycle; λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, C is the speed of light; Δf=f r -f t is the frequency difference, f t represents the transmission signal frequency of low-orbit satellite j; σt R0 represents the receiver clock error of the mobile station relative to the position of low-orbit satellite j, σt j represents the satellite clock error; It represents the Doppler count observation value of the mobile station to the low-orbit satellite j.

[0067] Specifically, the implementation process of a differential positioning technology based on low-orbit satellite Doppler frequency proposed in the solution of the present invention also includes: in step 2, specifically including step 21.

[0068] In step 21, for low-orbit satellite j, record the low-orbit satellite j at time t i-1 The position at And remember that low-orbit satellite j is at time t i The position at The mobile station is in this time period (i.e. time t i-1 To time t i The Doppler counting of the position of low-orbit satellite j is performed within the time period (time period), and the observation equation of the measured distance difference between the mobile station and the low-orbit satellite j can be obtained as follows:

[0069]

[0070] In formula (1), T i =t i -t i-1 , represents the Doppler counting period. λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, and C is the speed of light. Δf=f r -f t is the frequency difference, f t Represents the transmission signal frequency of low-orbit satellite j. σt R0 represents the receiver clock error of the mobile station relative to the position of low-orbit satellite j, σt j Indicates the satellite clock error. It represents the Doppler count observation value of the mobile station to the low-orbit satellite j. It represents the measured distance difference between the mobile station and the low-orbit satellite j, that is, the low-orbit satellite j at time t i-1 and time t i The difference in distance from the position to the mobile station at time t can also be expressed as equation (1-1):

[0071]

[0072] In formula (1-1), represents the low-orbit satellite j at time t i-1 The position at the time, represents the low-orbit satellite j at time t i The position at the time (X R0 , Y R0 , Z R0 ) represents the real position of the mobile station, It represents the measured distance difference between the mobile station and the low-orbit satellite j, that is, the low-orbit satellite j at t i-1 and t i The difference in distance from the location to the mobile station at each time.

[0073] Step s220, according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, according to the difference in position information of the low-orbit satellite with this number at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the reference station for the position of the low-orbit satellite with this number within the one Doppler counting cycle, determine the observation relationship of the reference station for the measured distance difference of the low-orbit satellite with this number.

[0074] In some embodiments, step s220 determines, for each numbered LEO satellite, the difference between the position information of the numbered LEO satellite at the start and end times of a Doppler counting cycle, and the Doppler count value of the reference station for the position of the numbered LEO satellite within the Doppler counting cycle, an observation relationship of the reference station on the measured distance difference of the numbered LEO satellite, including: determining the observation relationship of the reference station on the measured distance difference of the numbered LEO satellite according to formula (2):

[0075]

[0076] In formula (2), j represents the number of the low-orbit satellite; T i =t i -t i-1 , represents a Doppler counting cycle; λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, C is the speed of light; Δf=f r -f t is the frequency difference, f t represents the transmission signal frequency of low-orbit satellite j; σt B0 represents the receiver clock error of the reference station to the position of low-orbit satellite j, σt j represents the satellite clock error; represents the Doppler count observation value of the reference station to the low-orbit satellite j; It represents the distance difference measured by the base station to the low-orbit satellite j.

[0077] Specifically, the implementation process of a differential positioning technology based on the Doppler frequency of a low-orbit satellite proposed in the solution of the present invention further includes: in step 21, similar to formulas (1) and (1-1), the measured distance difference equation of the reference station to the low-orbit satellite j is expressed as:

[0078]

[0079] In formula (2), T i =t i -t i-1 , represents the Doppler counting period. λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, and C is the speed of light. Δf=f r -f t is the frequency difference, f t Represents the transmission signal frequency of low-orbit satellite j. σt B0 represents the receiver clock error of the reference station to the position of low-orbit satellite j, σt j Indicates the satellite clock error. It represents the Doppler count observation value of the reference station to the low-orbit satellite j. It represents the distance difference measured by the base station to the low-orbit satellite j.

[0080] Step s230, according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, based on the observation relationship of the measured distance difference of the mobile station for the low-orbit satellite with this number, and the observation relationship of the measured distance difference of the reference station for the low-orbit satellite with this number, after eliminating the satellite clock error, obtain the single difference distance relationship of the low-orbit satellite with this number.

[0081] In some embodiments, in step S230, according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, the satellite clock error is eliminated based on the observation relationship of the measured distance difference of the mobile station with the low-orbit satellite and the observation relationship of the measured distance difference of the reference station with the low-orbit satellite, and the single-difference distance relationship of the low-orbit satellite with the number is obtained, including: according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, the observation relationship of the measured distance difference of the mobile station with the low-orbit satellite and the observation relationship of the measured distance difference of the reference station with the low-orbit satellite are performed as inter-station single differences, and after eliminating the satellite clock error, the single-difference distance relationship of the low-orbit satellite with the number is obtained.

[0082] The single difference distance relationship of each numbered low-orbit satellite is as shown in formula (3). Of course, the single difference distance relationship of each numbered low-orbit satellite can also be as shown in formula (3-1):

[0083]

[0084] In formula (3), j represents the number of the low-orbit satellite; represents the measured distance difference between the mobile station and the low-orbit satellite j, represents the measured distance difference between the reference station and the low-orbit satellite j; λ = f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, C is the speed of light; σt R0 represents the receiver clock error of the mobile station relative to the position of low-orbit satellite j, σt B0 represents the receiver clock error of the reference station relative to the position of low-orbit satellite j; represents the Doppler count observation value of the mobile station to the low-orbit satellite j, It represents the Doppler count observation value of the reference station to the low-orbit satellite j.

[0085] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed in the solution of the present invention also includes: in step 2, specifically also includes step 22.

[0086] In step 22, the observation information of the reference station on the position of the low-orbit satellite j and the observation information of the mobile station on the position of the low-orbit satellite j are single-differenced between the stations. After eliminating the satellite clock errors of the observation information of the reference station and the mobile station on the position of the low-orbit satellite j, equation (3) can be obtained:

[0087]

[0088] In formula (3), represents the measured distance difference between the mobile station and the low-orbit satellite j, Represents the measured distance difference between the reference station and the low-orbit satellite j. λ=f r / C represents the signal wavelength, f r Represents the local oscillator frequency of the mobile station, and C is the speed of light. R0 represents the receiver clock error of the mobile station relative to the position of low-orbit satellite j, σt B0 It represents the receiver clock error of the reference station relative to the position of low-orbit satellite j. represents the Doppler count observation value of the mobile station to the low-orbit satellite j, It represents the Doppler count observation value of the reference station to the low-orbit satellite j.

[0089] Similarly, the single difference distance equation (3-1) of low-orbit satellite k can be obtained:

[0090]

[0091] In formula (3-1), represents the measured distance difference between the mobile station and the low-orbit satellite k, Represents the measured distance difference between the base station and the low-orbit satellite k. λ=f r / C represents the signal wavelength, f r Represents the local oscillator frequency of the mobile station, and C is the speed of light. R0 represents the receiver clock error of the mobile station relative to the position of the low-orbit satellite k, σt B0 It represents the receiver clock error of the reference station relative to the position of low-orbit satellite k. represents the Doppler count observation value of the mobile station to the low-orbit satellite k, It represents the Doppler count observation value of the base station for the low-orbit satellite k.

[0092] In step s240, according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the single-difference distance relationship between low-orbit satellites with different numbers, after eliminating the receiver clock error, an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite is obtained, which is recorded as the differential positioning observation relationship.

[0093] In some embodiments, in step S240, according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the single-difference distance relationship of low-orbit satellites with different numbers, after eliminating the receiver clock error, an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite is obtained, which is recorded as the differential positioning observation relationship, including: according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, the single-difference distance relationship of low-orbit satellites with different numbers is performed as an inter-satellite single difference, and after eliminating the receiver clock error, an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite is obtained, which is recorded as the differential positioning observation relationship.

[0094] The differential positioning observation relationship is as follows:

[0095]

[0096] In formula (4), j and k represent different numbers of low-orbit satellites; T i =t i -t i-1 , represents a Doppler counting cycle; represents the measured distance difference between the mobile station and the low-orbit satellite j, represents the measured distance difference between the reference station and the low-orbit satellite j; represents the measured distance difference between the mobile station and the low-orbit satellite k, represents the measured distance difference between the base station and the low-orbit satellite k; λ = f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, and C is the speed of light; represents the Doppler count observation value of the mobile station to the low-orbit satellite j, represents the Doppler count observation value of the base station to the low-orbit satellite j, represents the Doppler count observation value of the mobile station to the low-orbit satellite k, It represents the Doppler count observation value of the base station for the low-orbit satellite k.

[0097] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed in the solution of the present invention also includes: in step 2, specifically also includes step 23.

[0098] In step 23, after performing inter-satellite single difference on equation (3) and equation (3-1) and eliminating the receiver clock error, the final observation equation (4) for Doppler frequency differential positioning can be obtained:

[0099]

[0100] In equation (4), T i =t i -t i-1 , represents the Doppler counting period. λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, and C is the speed of light. and Is the Doppler count observation value, which is a known quantity, Recorded as

[0101] In step S250, according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the position information of low-orbit satellites with different numbers at the start and end times of a Doppler counting cycle, an estimated relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, which is recorded as the differential positioning estimation relationship.

[0102] In some embodiments, in step S250, according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the position information of low-orbit satellites with different numbers at the start and end times of a Doppler counting cycle, an estimated relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, which is recorded as the specific process of the differential positioning estimation relationship. Please refer to the following exemplary description.

[0103] The following combination Figure 3 The flowchart of an embodiment of determining the differential positioning estimation relationship in the method of the present invention further illustrates the specific process of determining the differential positioning estimation relationship in step S250, including: steps S310 to S320.

[0104] Step s310: record the error between the approximate position information of the mobile station and the real position information of the mobile station as the coordinate value (ΔX, ΔY, ΔZ), and record the starting time t of the low-orbit satellite j and the low-orbit satellite k in a Doppler counting cycle. i-1 and end time t i The positions at the time are the coordinate values Coordinate values and coordinate values Coordinate values

[0105] Step S320: Substitute the above coordinate values ​​into formula (4), and replace the above coordinate values ​​with the coordinate values ​​of the approximate location information of the mobile station (X R1 , Y R1 , Z R1 ) is expanded using Taylor’s formula to obtain the estimated relationship for differential positioning based on the Doppler frequency of low-orbit satellites, which is recorded as the differential positioning estimation relationship.

[0106] The differential positioning estimation relationship is formula (5):

[0107]

[0108] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed in the solution of the present invention also includes: in step 2, specifically also includes step 24.

[0109] In step 24, the Doppler frequency differential positioning estimation equation is given. The approximate coordinates of the mobile station R are (X R1 , Y R1 , Z R1 ), the approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) is (ΔX, ΔY, ΔZ), and the low-orbit satellite j and low-orbit satellite k are at time t i-1 and time t i The positions at and For equation (4), let ΔL * =Equal to the left side of the equation, the approximate coordinates of the mobile station R and the sum of the errors (X R1 +ΔX,Y R1 +ΔY,Z R1 +ΔZ), the real coordinates of the base station (X B0 , Y B0 , Z B0 ) and satellites j and k at t i-1 and t i The coordinate value of the mobile station at the time of the approximate coordinate value is substituted into the left side of equation (4), and the above coordinate value is replaced by (X R1 , Y R1 , Z R1 ) is expanded by Taylor formula and the higher-order terms are omitted. The estimation equation for Doppler frequency difference positioning is:

[0110]

[0111] At step S140, the error between the approximate position information of the mobile station and the true position information of the mobile station is determined based on the differential positioning observation relationship and the differential positioning estimation relationship.

[0112] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed in the solution of the present invention also includes: step 3, determining the approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) between the estimated value of the error (ΔX, ΔY, ΔZ), then perform step 4 to obtain the approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) between the error (ΔX, ΔY, ΔZ). Step 4: Determine the approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) between the error (ΔX, ΔY, ΔZ), then perform step 5 to make the approximate position (X R1 , Y R1 , Z R1 ) approaches the true position (X R0 , Y R0 , Z R0 ), thereby achieving positioning.

[0113] In some embodiments, the specific process of determining the error between the approximate location information of the mobile station and the actual location information of the mobile station based on the differential positioning observation relationship and the differential positioning estimation relationship in step S140 is described in the following exemplary embodiment.

[0114] The following combination Figure 4 The flowchart of an embodiment of determining the error between the approximate location information of the mobile station and the actual location information of the mobile station in the method of the present invention is shown, further illustrating the specific process of determining the error between the approximate location information of the mobile station and the actual location information of the mobile station in step S140, including: steps S410 to S420.

[0115] Step S410: subtract the differential positioning observation relationship from the differential positioning estimation relationship to minimize the residual sum of squares, and use the least squares method to estimate the error between the approximate position information of the mobile station and the true position information of the mobile station.

[0116] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed in the solution of the present invention also includes:

[0117] In step 3, the above formula, The difference between the observation equation (4) and the estimation equation (5) can obtain the residual formula (6):

[0118]

[0119] In the formula, ε q represents the residual of the estimation equation and the observation equation. Each observation can obtain an observation equation, and the unknowns in the above formula (6) are only ΔX, ΔY and ΔZ, which are three, so three observations can obtain the positioning result. In order to better utilize the observation data and suppress the error, according to the least square principle, multiple observations are performed, and the residual sum of squares is minimized. Assuming that the observation number is n, q is the observation number, and the residual sum of squares can be expressed as

[0120] In order to solve ΔX, ΔY and ΔZ, the residual sum of squares The partial derivative of ΔX, ΔY and ΔZ is zero, which can obtain:

[0121]

[0122] The formula (6) is brought into the formula (7), and is expanded, which can obtain:

[0123]

[0124]

[0125]

[0126] In the equation (8), and M are known quantities.

[0127] Step S420, in the case of observing two low-orbit satellites, according to the estimation value of the error between the approximate position information of the mobile station and the true position information of the mobile station under three Doppler count periods, the error between the approximate position information of the mobile station and the true position information of the mobile station is determined.

[0128] Specifically, the implementation process of the differential positioning technology based on low-orbit satellite Doppler frequency proposed by the scheme of the application further includes: in step 4, in the case of observing two stars, three Doppler count periods are required to obtain the approximate coordinates of the mobile station R and the true coordinates (X R0 , Y R0 , Z R0) between the two satellites (ΔX, ΔY, ΔZ). In one Doppler counting cycle, at least three satellites need to be observed to obtain the approximate coordinates of the mobile station R and the true coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) between (ΔX, ΔY, ΔZ).

[0129] At step s150, the approximate location information of the mobile station is corrected according to the error between the approximate location information of the mobile station and the real location information of the mobile station, so that the approximate location information of the mobile station approaches the real location information of the mobile station, thereby realizing the positioning of the mobile station.

[0130] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed in the solution of the present invention also includes: step 5, making the approximate position (X R1 , Y R1 , Z R1 ) approaches the true position (X R0 , Y R0 , Z R0 ), thereby achieving positioning.

[0131] The solution of the present invention proposes a differential positioning technology based on the Doppler frequency of low-orbit satellites. By fully considering the influence of satellite clock error and receiver clock error, a differential algorithm is adopted to eliminate them (i.e. the influence of satellite clock error and receiver clock error). It fully utilizes the advantages of the large number of low-orbit satellites and the rapid change of Doppler frequency, can achieve positioning in a single Doppler observation period, and can improve the accuracy of positioning.

[0132] In some embodiments, in step S150, the approximate location information of the mobile station is corrected based on the error between the approximate location information of the mobile station and the actual location information of the mobile station, so that the approximate location information of the mobile station approaches the actual location information of the mobile station, thereby realizing the specific process of positioning the mobile station. Please refer to the following exemplary description.

[0133] The following combination Figure 5 The flowchart of an embodiment of the method of the present invention for making the approximate location information of the mobile station approach the real location information of the mobile station further illustrates the specific process of making the approximate location information of the mobile station approach the real location information of the mobile station in step S150, including: steps S510 to S530.

[0134] Step s510: correcting the approximate location information of the mobile station according to the error between the approximate location information of the mobile station and the actual location information of the mobile station.

[0135] Step S520: Re-determine the error between the approximate location information of the mobile station and the actual location information of the mobile station, and correct the approximate location information of the mobile station based on the error between the re-determined approximate location information of the mobile station and the actual location information of the mobile station.

[0136] Step S530 is iterated until the approximate location information of the mobile station approaches the real location information of the mobile station, thereby achieving positioning of the mobile station.

[0137] Specifically, the implementation process of a differential positioning technology based on low-orbit satellite Doppler frequency proposed by the solution of the present invention also includes: in step 5, the approximate position (X R1 , Y R1 , Z R1 ) Use the obtained approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) are corrected, and equation (8) is used again to calculate and re-obtain the approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) between the error (ΔX, ΔY, ΔZ), through multiple iterations, the approximate position (X R1 , Y R1 , Z R1 ) approaches the true position (X R0 , Y R0 , Z R0 ), thereby achieving positioning.

[0138] The method of the present invention fully considers the influence of satellite clock error and receiver clock error, adopts differential algorithm to eliminate them (i.e. the influence of satellite clock error and receiver clock error), fully utilizes the advantages of a large number of low-orbit satellites and rapid Doppler frequency changes, can achieve positioning in a single Doppler observation period, and can improve positioning accuracy.

[0139] According to a second embodiment of the present invention, a differential positioning device based on a low-orbit satellite is provided, for implementing differential positioning based on the Doppler frequency of the low-orbit satellite, wherein the number of observations of the low-orbit satellite is n times, where n is a positive integer greater than or equal to 1. Figure 6 As shown, the differential positioning device based on low-orbit satellites includes: an acquisition unit 102 and a control unit 104.

[0140] The control unit 104 is configured to determine a reference station and a mobile station, the reference station and the mobile station can simultaneously receive signals transmitted by each low-orbit satellite, and the reference station can transmit observation information and prior information of itself to the mobile station. The specific functions and processes of the control unit 104 are described in step s110.

[0141] The acquisition unit 102 is configured to acquire position information of the reference station, such as the position information (X B0 , Y B0 , Z B0 ) of the reference station, acquire approximate coordinates of the mobile station, determine real position information (X R0 , Y R0 , Z R0 ) of the mobile station according to the approximate coordinates of the mobile station, acquire local oscillator frequencies (such as f r ) of the reference station and the mobile station, and acquire numbers of each low-orbit satellite, such as the number j of the first low-orbit satellite and the number k of the second low-orbit satellite. The specific functions and processes of the acquisition unit 102 are described in step S120.

[0142] Specifically, the implementation process of the differential positioning technology based on low-orbit satellite Doppler frequency proposed by the scheme of the present application includes: step 1, determining position information (X B0 , Y B0 , Z B0 ) of a reference station and real position (X R0 , Y R0 , Z R0 ) of a mobile station, determining local oscillator frequencies f r of the reference station and the mobile station, determining numbers j and k of low-orbit satellites, and then performing step 2 to obtain an observation equation of Doppler frequency differential positioning and an estimation equation of Doppler frequency differential positioning.

[0143] In the scheme of the present application, the differential positioning based on low-orbit satellite Doppler frequency needs a reference station with accurate known position information, which is set as (X B0 , Y B0 , Z B0 ). The position information of the mobile station needs to be estimated, and it is assumed that the real position of the mobile station is (X R0 , Y R0 , Z R0 ), and the local oscillator frequencies of the reference station and the mobile station are both f r, they receive low-orbit satellite signals at the same time, and the base station can transmit its own observation information and prior information to the mobile station. The low-orbit satellites are numbered with j and k, and the frequency of the low-orbit satellite's transmission signal is f t The position information of low-orbit satellites can be obtained in real time through TLE (Two-Line Orbital Element) files or ephemeris files.

[0144] The control unit 104 is further configured to determine the actual location information of the mobile station based on the approximate coordinates of the mobile station; determine an observation relationship for differential positioning based on the Doppler frequencies of the LEO satellites, denoted as a differential positioning observation relationship, based on the number of each LEO satellite and the difference between the location information of each LEO satellite at the start and end of a Doppler counting cycle, the location information of the base station, the actual location information of the mobile station, and the local oscillator frequencies of the reference station and the mobile station; and determine an estimated relationship for differential positioning based on the Doppler frequencies of the LEO satellites, denoted as a differential positioning estimated relationship. The specific functions and processing of the control unit 104 are further described in step S130.

[0145] According to the approximate coordinates of the mobile station, such as the coordinate value (X R1 , Y R1 , Z R1 ), calculate the error (ΔX, ΔY, ΔZ), and then deduct the error to obtain the real position information of the mobile station such as the coordinate value (X R0 , Y R0 , Z R0 ).

[0146] Specifically, the implementation process of a differential positioning technology based on the Doppler frequency of a low-orbit satellite proposed in the solution of the present invention also includes: step 2, determining the observation equation of Doppler frequency differential positioning and the estimation equation of Doppler frequency differential positioning, and then executing step 3 to obtain the approximate coordinates (X R1 , Y R1 , Z R1 ) and the real coordinates (X R0 , Y R0 , Z R0 ) is an estimate of the error (ΔX, ΔY, ΔZ) between .

[0147] In some embodiments, the control unit 104 determines the real position information of the mobile station based on the approximate coordinates of the mobile station; determines, according to the number of each low-orbit satellite, an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite and a difference between the position information of each low-orbit satellite at the start and end times of a Doppler counting cycle, the position information of the base station, the real position information of the mobile station, and the local oscillator frequencies of the reference station and the mobile station, recorded as a differential positioning observation relationship; and determines an estimated relationship for differential positioning based on the Doppler frequency of the low-orbit satellite, recorded as a differential positioning estimated relationship, including:

[0148] The control unit 104 is further configured to determine, for each LEO satellite number, an observed relationship of the mobile station's measured range difference with respect to each numbered LEO satellite based on the difference in position information of the numbered LEO satellite at the start and end times of a Doppler counting cycle, and the Doppler count value of the mobile station's position of the numbered LEO satellite within the Doppler counting cycle. The specific functions and processing of the control unit 104 are further described in step S210.

[0149] In some embodiments, the control unit 104 determines, according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, based on the difference in position information of the numbered low-orbit satellite at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the mobile station for the position of the numbered low-orbit satellite within the Doppler counting cycle, the observation relationship of the mobile station on the measured distance difference of the numbered low-orbit satellite, including: the control unit 104 is further configured to determine the observation relationship of the mobile station on the measured distance difference of the numbered low-orbit satellite according to formula (1):

[0150]

[0151] In formula (1), j represents the number of the low-orbit satellite; T i =t i -t i-1 , represents a Doppler counting cycle; λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, C is the speed of light; Δf=f r -f t is the frequency difference, f t represents the transmission signal frequency of low-orbit satellite j; σt R0 represents the receiver clock error of the mobile station relative to the position of low-orbit satellite j, σt j represents the satellite clock error; The Doppler count observation value of the mobile station to the low-orbit satellite j.

[0152] Specifically, the scheme of the present application proposes an implementation process of a differential positioning technology based on the Doppler frequency of low-orbit satellites, which further comprises: in step 2, specifically comprising step 21.

[0153] In step 21, for the low-orbit satellite j, the position of the low-orbit satellite j at time t i-1 is recorded as and the position of the low-orbit satellite j at time t i is recorded as The mobile station performs Doppler counting on the position of the low-orbit satellite j within the time period (i.e. the time period from time t i-1 to time t i ), and accordingly, the measured distance difference observation equation of the mobile station to the low-orbit satellite j can be obtained as:

[0154]

[0155] In formula (1), T i = t i -t i-1 , indicating the Doppler counting period. λ = f r / C indicates the signal wavelength, f r indicates the local oscillator frequency of the mobile station, and C is the speed of light. Δf = f r -f t is the frequency difference, f t indicates the transmission signal frequency of the low-orbit satellite j. σt R0 indicates the receiver clock difference of the mobile station to the position of the low-orbit satellite j, and σt j indicates the satellite clock difference. The Doppler count observation value of the mobile station to the low-orbit satellite j. The measured distance difference of the mobile station to the low-orbit satellite j, i.e. the difference between the distances from the positions of the low-orbit satellite j at time t i-1 and time t i to the mobile station, can also be expressed as equation (1-1):

[0156]

[0157] In formula (1-1), indicates the position of the low-orbit satellite j at time t i-1 , indicates the position of the low-orbit satellite j at time t i , (X R0 , Y R0 , Z R0 ) indicates the true position of the mobile station, It represents the measured distance difference between the mobile station and the low-orbit satellite j, that is, the low-orbit satellite j at t i-1 and t i The difference in distance from the location to the mobile station at each time.

[0158] The control unit 104 is further configured to determine, for each LEO satellite number, an observation relationship of the reference station's measured range difference with respect to each LEO satellite number based on the difference in position information of the LEO satellite number at the start and end times of a Doppler counting cycle, and the Doppler count value of the reference station's position of the LEO satellite numbered within the Doppler counting cycle. The specific functions and processing of the control unit 104 are further described in step S220.

[0159] In some embodiments, the control unit 104 determines, according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, based on the difference in position information of the numbered low-orbit satellite at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the reference station for the position of the numbered low-orbit satellite within the one Doppler counting cycle, the observation relationship of the reference station on the measured distance difference of the numbered low-orbit satellite, including: the control unit 104 is further configured to determine the observation relationship of the reference station on the measured distance difference of the numbered low-orbit satellite according to formula (2):

[0160]

[0161] In formula (2), j represents the number of the low-orbit satellite; T i =t i -t i-1 , represents a Doppler counting cycle; λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, C is the speed of light; Δf=f r -f t is the frequency difference, f t represents the transmission signal frequency of low-orbit satellite j; σt B0 represents the receiver clock error of the reference station to the position of low-orbit satellite j, σt j represents the satellite clock error; represents the Doppler count observation value of the reference station to the low-orbit satellite j; It represents the distance difference measured by the base station to the low-orbit satellite j.

[0162] Specifically, the implementation process of a differential positioning technology based on the Doppler frequency of a low-orbit satellite proposed in the solution of the present invention further includes: in step 21, similar to formulas (1) and (1-1), the measured distance difference equation of the reference station to the low-orbit satellite j is expressed as:

[0163]

[0164] In formula (2), T i =t i -t i-1 , represents the Doppler counting period. λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, and C is the speed of light. Δf=f r -f t is the frequency difference, f t Represents the transmission signal frequency of low-orbit satellite j. σt B0 represents the receiver clock error of the reference station to the position of low-orbit satellite j, σt j Indicates the satellite clock error. It represents the Doppler count observation value of the reference station to the low-orbit satellite j. It represents the distance difference measured by the base station to the low-orbit satellite j.

[0165] The control unit 104 is further configured to, based on the number of each LEO satellite, eliminate the satellite clock error based on the observed relationship of the distance difference measured by the mobile station for the LEO satellite with the number and the observed relationship of the distance difference measured by the reference station for the LEO satellite with the number, thereby obtaining a single-difference distance relationship for the LEO satellite with the number. The specific functions and processing of the control unit 104 are further described in step S230.

[0166] In some embodiments, the control unit 104, according to the number of each low-orbit satellite, obtains, for each numbered low-orbit satellite, a single-difference distance relationship of the numbered low-orbit satellite after eliminating the satellite clock error based on an observation relationship of the mobile station's measured distance difference for the numbered low-orbit satellite and an observation relationship of the reference station's measured distance difference for the numbered low-orbit satellite, including:

[0167] The control unit 104 is further configured to perform inter-station single difference on the observation relationship of the mobile station's measured distance difference with the numbered low-orbit satellite and the observation relationship of the reference station's measured distance difference with the numbered low-orbit satellite, according to the number of each low-orbit satellite. After eliminating the satellite clock error, the single difference distance relationship of the low-orbit satellite with the number is obtained.

[0168] The single difference distance relationship of each numbered low-orbit satellite is as shown in formula (3). Of course, the single difference distance relationship of each numbered low-orbit satellite can also be as shown in formula (3-1):

[0169]

[0170] In formula (3), j represents the number of the low-orbit satellite; represents the measured distance difference of the mobile station to the low-orbit satellite j, represents the measured distance difference of the reference station to the low-orbit satellite j; λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, C is the speed of light; σt R0 represents the receiver clock difference of the mobile station to the position of the low-orbit satellite j, σt B0 represents the receiver clock difference of the reference station to the position of the low-orbit satellite j; represents the Doppler count observation value of the mobile station to the low-orbit satellite j, represents the Doppler count observation value of the reference station to the low-orbit satellite j.

[0171] Specifically, the implementation process of the differential positioning technology based on the low-orbit satellite Doppler frequency proposed by the scheme further comprises: in step 2, specifically further comprising step 22.

[0172] In step 22, the observation information of the reference station to the position of the low-orbit satellite j and the observation information of the mobile station to the position of the low-orbit satellite j are processed by inter-station single difference, and after the satellite clock difference of the observation information of the reference station and the mobile station to the position of the low-orbit satellite j is eliminated, equation (3) can be obtained:

[0173]

[0174] In formula (3), represents the measured distance difference of the mobile station to the low-orbit satellite j, represents the measured distance difference of the reference station to the low-orbit satellite j. λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, C is the speed of light. σt R0 represents the receiver clock difference of the mobile station to the position of the low-orbit satellite j, σt B0 represents the receiver clock difference of the reference station to the position of the low-orbit satellite j. represents the Doppler count observation value of the mobile station to the low-orbit satellite j, represents the Doppler count observation value of the reference station to the low-orbit satellite j.

[0175] Similarly, the single difference distance equation (3-1) of the low-orbit satellite k can be obtained:

[0176]

[0177] In formula (3-1), represents the measured distance difference of the mobile station to the low-orbit satellite k, denotes the measured range difference of the reference station to the low earth orbit satellite k. λ = f r / C denotes the signal wavelength, f r denotes the local oscillator frequency of the mobile station, and C is the speed of light. σt R0 denotes the receiver clock error of the mobile station to the position of the low earth orbit satellite k. σt B0 denotes the receiver clock error of the reference station to the position of the low earth orbit satellite k. denotes the Doppler count observation value of the mobile station to the low earth orbit satellite k, denotes the Doppler count observation value of the reference station to the low earth orbit satellite k.

[0178] The control unit 104 is specifically further configured to, according to the single-difference range relationship of different numbered low earth orbit satellites, eliminate the receiver clock error, and obtain an observation relationship based on differential positioning of low earth orbit satellite Doppler frequency, denoted as a differential positioning observation relationship, according to the number of each low earth orbit satellite in the low earth orbit satellites, for different numbered low earth orbit satellites. The specific functions and processes of the control unit 104 also refer to step S240.

[0179] In some embodiments, the control unit 104, according to the single-difference range relationship of different numbered low earth orbit satellites, eliminates the receiver clock error, and obtains an observation relationship based on differential positioning of low earth orbit satellite Doppler frequency, denoted as a differential positioning observation relationship, according to the number of each low earth orbit satellite in the low earth orbit satellites, for different numbered low earth orbit satellites, including: the control unit 104 is specifically further configured to, according to the single-difference range relationship of different numbered low earth orbit satellites, eliminate the receiver clock error, and obtain an observation relationship based on differential positioning of low earth orbit satellite Doppler frequency, denoted as a differential positioning observation relationship, according to the number of each low earth orbit satellite in the low earth orbit satellites, for different numbered low earth orbit satellites.

[0180] The differential positioning observation relationship is as formula (4):

[0181]

[0182] In formula (4), j and k represent different numbers of low earth orbit satellites; T i = t i -t i-1 , which represents a Doppler count period; denotes the measured range difference of the mobile station to the low earth orbit satellite j, denotes the measured range difference of the reference station to the low earth orbit satellite j; denotes the measured range difference of the mobile station to the low earth orbit satellite k, denotes the measured range difference of the reference station to the low earth orbit satellite k; λ = f r / C denotes the signal wavelength, f r denotes the local oscillator frequency of the mobile station, and C is the speed of light. represents the Doppler count observation value of the mobile station to the low-orbit satellite j, represents the Doppler count observation value of the base station to the low-orbit satellite j, represents the Doppler count observation value of the mobile station to the low-orbit satellite k, It represents the Doppler count observation value of the base station for the low-orbit satellite k.

[0183] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed in the solution of the present invention also includes: in step 2, specifically also includes step 23.

[0184] In step 23, after performing inter-satellite single difference on equation (3) and equation (3-1) and eliminating the receiver clock error, the final observation equation (4) for Doppler frequency differential positioning can be obtained:

[0185]

[0186] In equation (4), T i =t i -t i-1 , represents the Doppler counting period. λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, and C is the speed of light. and Is the Doppler count observation value, which is a known quantity, Recorded as

[0187] The control unit 104 is further configured to determine, based on the number of each LEO satellite, an estimated relationship for differential positioning based on the Doppler frequency of each LEO satellite, based on the position information of each LEO satellite at the start and end times of a Doppler counting cycle. The relationship is recorded as a differential positioning estimated relationship. The specific functions and processing of the control unit 104 are further described in step S250.

[0188] In some embodiments, the control unit 104 determines, according to the number of each low-orbit satellite among the low-orbit satellites, for low-orbit satellites with different numbers, based on the position information of the low-orbit satellites with different numbers at the start time and the end time of a Doppler counting cycle, an estimated relationship for differential positioning based on the low-orbit satellite Doppler frequency, recorded as a differential positioning estimated relationship, including:

[0189] The control unit 104 is further configured to record the error between the approximate position information of the mobile station and the real position information of the mobile station as a coordinate value (ΔX, ΔY, ΔZ), and record the starting time t of the low-orbit satellite j and the low-orbit satellite k in a Doppler counting cycle.i-1 and end time t i The positions at the time are the coordinate values Coordinate values and coordinate values Coordinate values The specific functions and processing of the control unit 104 can also be found in step s310.

[0190] The control unit 104 is further configured to substitute the above coordinate values ​​into formula (4), and replace the above coordinate values ​​with the coordinate values ​​of the approximate position information of the mobile station (X R1 , Y R1 , Z R1 ) is expanded using the Taylor formula to obtain an estimated relationship for differential positioning based on the low-orbit satellite Doppler frequency, which is recorded as the differential positioning estimated relationship. The specific functions and processing of the control unit 104 are also shown in step S320.

[0191] The differential positioning estimation relationship is formula (5):

[0192]

[0193] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed in the solution of the present invention also includes: in step 2, specifically also includes step 24.

[0194] In step 24, the Doppler frequency differential positioning estimation equation is given. The approximate coordinates of the mobile station R are (X R1 , Y R1 , Z R1 ), the approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) is (ΔX, ΔY, ΔZ), and the low-orbit satellite j and low-orbit satellite k are at time t i-1 and time t i The positions at and For equation (4), let ΔL * =Equal to the left side of the equation, the approximate coordinates of the mobile station R and the sum of the errors (X R1 +ΔX,T R1 +ΔY,Z R1 +ΔZ), the real coordinates of the base station (X B0 , Y B0 , Z B0 ) and satellites j and k at t i-1 and t i Substitute the above coordinate values ​​into the left side of equation (4) and replace the above coordinate values ​​in (XR1 , Y R1 , Z R1 ) is expanded by Taylor formula and the higher-order terms are omitted. The estimation equation for Doppler frequency difference positioning is:

[0195]

[0196] The control unit 104 is further configured to determine the error between the approximate location information of the mobile station and the actual location information of the mobile station based on the differential positioning observation relationship and the differential positioning estimation relationship. The specific functions and processing of the control unit 104 are also shown in step S140.

[0197] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed in the solution of the present invention also includes: step 3, determining the approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) between the estimated value of the error (ΔX, ΔY, ΔZ), then perform step 4 to obtain the approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) between the error (ΔX, ΔY, ΔZ). Step 4: Determine the approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) between the error (ΔX, ΔY, ΔZ), then perform step 5 to make the approximate position (X R1 , Y R1 , Z R1 ) approaches the true position (X R0 , Y R0 , Z R0 ), thereby achieving positioning.

[0198] In some embodiments, the control unit 104 determines, based on the differential positioning observation relationship and the differential positioning estimation relationship, an error between the approximate position information of the mobile station and the actual position information of the mobile station, including:

[0199] The control unit 104 is further configured to subtract the differential positioning observation relationship from the differential positioning estimation relationship to minimize the residual sum of squares, and to estimate an error between the approximate position information of the mobile station and the actual position information of the mobile station using a least squares method. The specific functions and processing of the control unit 104 are further described in step S410.

[0200] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed in the solution of the present invention also includes:

[0201] In step 3, in the above formula, By subtracting the observed equation (4) from the estimated equation (5), we can obtain the residual formula (6):

[0202]

[0203] Where, ε q Represents the residual between the estimated equation and the observation equation. Each time an observation is made, an observation equation can be obtained. The only unknowns in the above formula (6) are ΔX, ΔY and ΔZ, a total of 3. Therefore, the positioning result can be obtained by making 3 observations. In order to make better use of the observation data and suppress the error, according to the least squares principle, multiple observations are made to minimize the residual square sum. Let the number of observations be n, q be the number of observations, and the residual square sum can be expressed as

[0204] In order to solve for ΔX, ΔY, and ΔZ, the sum of squares of the residuals The partial derivatives at ΔX, ΔY, and ΔZ are zero, and we can get:

[0205]

[0206] Substituting formula (6) into formula (7) and expanding it, we can get:

[0207]

[0208]

[0209]

[0210] In equation (8), and M are known quantities.

[0211] The control unit 104 is further configured to determine, when two low-orbit satellites are observed, an error between the approximate position information of the mobile station and the actual position information of the mobile station based on an estimated value of the error between the approximate position information of the mobile station and the actual position information of the mobile station over three Doppler counting periods. The specific functions and processing of the control unit 104 are further described in step S420.

[0212] Specifically, the implementation process of the differential positioning technology based on the Doppler frequency of the low-orbit satellite according to the scheme of the present application further comprises: in step 4, in the case of observing two stars, three Doppler counting periods are needed to obtain the error (ΔX, ΔY, ΔZ) between the approximate coordinates of the mobile station R and the true coordinates (X R0 , Y R0 , Z R0 ) of the mobile station R by solving the simultaneous equations (8). In one Doppler counting period, at least three satellites are needed to obtain the error (ΔX, ΔY, ΔZ) between the approximate coordinates of the mobile station R and the true coordinates (X R0 , Y R0 , Z R0 ) of the mobile station R.

[0213] The control unit 104 is further configured to correct the approximate position information of the mobile station according to the error between the approximate position information of the mobile station and the true position information of the mobile station, so as to make the approximate position information of the mobile station tend to the true position information of the mobile station, thereby realizing the positioning of the mobile station. The specific functions and processes of the control unit 104 are also described in step S150.

[0214] Specifically, the implementation process of the differential positioning technology based on the Doppler frequency of the low-orbit satellite according to the scheme of the present application further comprises: step 5, making the approximate position (X R1 , Y R1 , Z R1 ) tend to the true position (X XR , Y R0 , Z R0 ), thereby realizing the positioning.

[0215] In some embodiments, the control unit 104 corrects the approximate position information of the mobile station according to the error between the approximate position information of the mobile station and the true position information of the mobile station, so as to make the approximate position information of the mobile station tend to the true position information of the mobile station, thereby realizing the positioning of the mobile station, which comprises:

[0216] The control unit 104 is further configured to correct the approximate position information of the mobile station according to the error between the approximate position information of the mobile station and the true position information of the mobile station. The specific functions and processes of the control unit 104 are also described in step s510.

[0217] The control unit 104 is further configured to re-determine the error between the approximate location information of the mobile station and the actual location information of the mobile station, and correct the approximate location information of the mobile station based on the error between the re-determined approximate location information of the mobile station and the actual location information of the mobile station. The specific functions and processing of the control unit 104 are further described in step S520.

[0218] The control unit 104 is further configured to iterate in this manner until the approximate location information of the mobile station approaches the actual location information of the mobile station, thereby achieving positioning of the mobile station. Specific functions and processing of the control unit 104 are further described in step S530.

[0219] Specifically, the implementation process of a differential positioning technology based on low-orbit satellite Doppler frequency proposed by the solution of the present invention also includes: in step 5, the approximate position (X R1 , Y R1 , Z R1 ) Use the obtained approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) are corrected, and equation (8) is used again to calculate and re-obtain the approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) between the error (ΔX, ΔY, ΔZ), through multiple iterations, the approximate position (X R1 , Y R1 , Z R1 ) approaches the true position (X R0 , Y R0 , Z R0 ), thereby achieving positioning.

[0220] The solution of the present invention proposes a differential positioning technology based on the Doppler frequency of low-orbit satellites. By fully considering the influence of satellite clock error and receiver clock error, a differential algorithm is adopted to eliminate them (i.e. the influence of satellite clock error and receiver clock error). It fully utilizes the advantages of the large number of low-orbit satellites and the rapid change of Doppler frequency, can achieve positioning in a single Doppler observation period, and can improve the accuracy of positioning.

[0221] Since the processing and functions implemented by the device of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for any details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0222] According to a third embodiment of the present invention, a storage medium is provided, which includes a stored program, wherein when the program is run, the device where the storage medium is located is controlled to execute the above-mentioned differential positioning method based on low-orbit satellites.

[0223] Since the processing and functions implemented by the storage medium of this embodiment basically correspond to the embodiments, principles and examples of the aforementioned method, for any details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments and will not be repeated here.

[0224] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A differential positioning method based on low-orbit satellites, characterized in that: The method is used to implement differential positioning based on the Doppler frequency of a low-orbit satellite, wherein the number of observations of the low-orbit satellite is n, where n is a positive integer greater than or equal to 1. The differential positioning method based on the low-orbit satellite comprises the following steps: Determining a reference station and a mobile station; the reference station and the mobile station are capable of simultaneously receiving signals transmitted by each of the low-orbit satellites; and the reference station is capable of transmitting its own observation information and prior information to the mobile station; Obtaining location information of the reference station; Obtaining approximate coordinates of the mobile station; Acquiring local oscillator frequencies of the reference station and the mobile station; And obtain the number of each low-orbit satellite in the low-orbit satellite; determining the real location information of the mobile station according to the approximate coordinates of the mobile station; Determine, according to the number of each low-orbit satellite, an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellites based on the difference in position information of each low-orbit satellite at the start time and the end time of a Doppler counting cycle, the position information of the reference station, the true position information of the mobile station, and the local oscillator frequencies of the reference station and the mobile station, and record it as the differential positioning observation relationship; And determine the estimation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite, which is recorded as the differential positioning estimation relationship; determining an error between the approximate position information of the mobile station and the true position information of the mobile station based on the differential positioning observation relationship and the differential positioning estimation relationship; According to the error between the approximate location information of the mobile station and the real location information of the mobile station, the approximate location information of the mobile station is corrected so that the approximate location information of the mobile station approaches the real location information of the mobile station, thereby realizing the positioning of the mobile station.

2. The differential positioning method based on low-orbit satellites according to claim 1, characterized in that: Determining the true position information of the mobile station according to the approximate coordinates of the mobile station; determining, according to the number of each low-orbit satellite, an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellites and based on the difference between the position information of each low-orbit satellite at the start time and the end time of a Doppler counting cycle, the position information of the reference station, the true position information of the mobile station, and the local oscillator frequencies of the reference station and the mobile station, and recording it as the differential positioning observation relationship; And determine the estimation relationship for differential positioning based on the low-orbit satellite Doppler frequency, recorded as the differential positioning estimation relationship, including: According to the number of each low-orbit satellite, for each numbered low-orbit satellite, based on the difference in position information of the numbered low-orbit satellite at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the mobile station for the position of the numbered low-orbit satellite within the Doppler counting cycle, determining an observation relationship of the mobile station with respect to a measured range difference of the numbered low-orbit satellite; According to the number of each low-orbit satellite, for each numbered low-orbit satellite, based on the difference in position information of the numbered low-orbit satellite at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the reference station for the position of the numbered low-orbit satellite in the Doppler counting cycle, determining an observation relationship of the reference station for the measured range difference of the numbered low-orbit satellite; According to the number of each low-orbit satellite, for each numbered low-orbit satellite, based on the observed relationship of the distance difference measured by the mobile station for the numbered low-orbit satellite and the observed relationship of the distance difference measured by the reference station for the numbered low-orbit satellite, after eliminating the satellite clock error, a single-difference distance relationship of the numbered low-orbit satellite is obtained; According to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the single-difference distance relationship of low-orbit satellites with different numbers, after eliminating the receiver clock error, an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite is obtained, which is recorded as the differential positioning observation relationship; According to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the position information of low-orbit satellites with different numbers at the start and end times of a Doppler counting cycle, an estimation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite is determined, which is recorded as the differential positioning estimation relationship.

3. The differential positioning method based on low-orbit satellites according to claim 2, characterized in that: in, According to the number of each low-orbit satellite among the low-orbit satellites, for each numbered low-orbit satellite, determining, based on a difference in position information of the numbered low-orbit satellite at a start time and an end time of a Doppler counting cycle, and a Doppler count value of the mobile station for the position of the numbered low-orbit satellite within the Doppler counting cycle, an observation relationship of the mobile station with respect to a measured distance difference of the numbered low-orbit satellite is determined, including: According to formula (1), the observation relationship of the mobile station's measured distance difference to the low-orbit satellite with this number is determined: In formula (1), j represents the number of the low-orbit satellite; T i =t i -t i-1 , represents a Doppler counting cycle, t i is the end time of a Doppler counting cycle, t i-1 is the starting time of a Doppler counting cycle; λ=f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, and C is the speed of light; Δf=f r -f t is the frequency difference, f t represents the transmission signal frequency of low-orbit satellite j; σt R0 represents the receiver clock error of the mobile station relative to the position of low-orbit satellite j, σt j represents the satellite clock error; represents the Doppler count observation value of the mobile station to the low-orbit satellite j; and / or, According to the number of each low-orbit satellite among the low-orbit satellites, for each numbered low-orbit satellite, based on the difference in position information of the numbered low-orbit satellite at the start time and the end time of a Doppler counting cycle, and the Doppler count value of the reference station for the position of the numbered low-orbit satellite within the one Doppler counting cycle, determining an observation relationship of the reference station for the measured distance difference of the numbered low-orbit satellite, including: According to formula (2), the observation relationship of the reference station to the measured distance difference of the low-orbit satellite with this number is determined: In formula (2), j represents the number of the low-orbit satellite; T i =t i -t i-1 , represents a Doppler counting cycle, t i is the end time of a Doppler counting cycle, t i-1 is the starting time of a Doppler counting cycle; λ=f r / C represents the signal wavelength, f r Indicates the local oscillator frequency of the mobile station. The local oscillator frequencies of the reference station and the mobile station are both f r , C is the speed of light; Δf=f r -f t is the frequency difference, f t represents the transmission signal frequency of low-orbit satellite j; σt B0 represents the receiver clock error of the reference station to the position of low-orbit satellite j, σt j represents the satellite clock error; represents the Doppler count observation value of the reference station to the low-orbit satellite j; It represents the distance difference measured by the base station to the low-orbit satellite j.

4. The low-orbit satellite-based differential positioning method according to claim 2, wherein: According to the number of each low-orbit satellite among the low-orbit satellites, for each numbered low-orbit satellite, after eliminating the satellite clock error based on the observation relationship of the mobile station's measured distance difference for the numbered low-orbit satellite and the observation relationship of the reference station's measured distance difference for the numbered low-orbit satellite, a single-difference distance relationship of the numbered low-orbit satellite is obtained, including: According to the number of each low-orbit satellite, for each numbered low-orbit satellite, perform inter-station single difference on the observation relationship of the mobile station's measured distance difference with the numbered low-orbit satellite and the observation relationship of the reference station's measured distance difference with the numbered low-orbit satellite, and after eliminating the satellite clock error, obtain the single difference distance relationship of the numbered low-orbit satellite; The single difference distance relationship of each numbered low-orbit satellite is as follows: In formula (3), j represents the number of the low-orbit satellite; represents the measured distance difference between the mobile station and the low-orbit satellite j, represents the measured distance difference between the reference station and the low-orbit satellite j; λ = f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, C is the speed of light; σt R0 represents the receiver clock error of the mobile station relative to the position of low-orbit satellite j, σt B0 represents the receiver clock error of the reference station relative to the position of low-orbit satellite j; represents the Doppler count observation value of the mobile station to the low-orbit satellite j, It represents the Doppler count observation value of the reference station to the low-orbit satellite j.

5. The differential positioning method based on low-orbit satellites according to claim 2, characterized in that: According to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the single-difference distance relationship of low-orbit satellites with different numbers, after eliminating the receiver clock error, the observation relationship for differential positioning based on the low-orbit satellite Doppler frequency is obtained, which is recorded as the differential positioning observation relationship, including: According to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, the single-difference distance relationship of low-orbit satellites with different numbers is performed as an inter-satellite single difference. After eliminating the receiver clock error, the observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite is obtained, which is recorded as the differential positioning observation relationship; The differential positioning observation relationship is as follows: In formula (4), j and k represent different numbers of low-orbit satellites; T i =t i -t i-1 , represents a Doppler counting cycle, t i is the end time of a Doppler counting cycle, t i-1 is the starting moment of a Doppler counting cycle; represents the measured distance difference between the mobile station and the low-orbit satellite j, represents the measured distance difference between the reference station and the low-orbit satellite j; represents the measured distance difference between the mobile station and the low-orbit satellite k, represents the measured distance difference between the base station and the low-orbit satellite k; λ = f r / C represents the signal wavelength, f r represents the local oscillator frequency of the mobile station, and C is the speed of light; represents the Doppler count observation value of the mobile station to the low-orbit satellite j, represents the Doppler count observation value of the base station to the low-orbit satellite j, represents the Doppler count observation value of the mobile station to the low-orbit satellite k, It represents the Doppler count observation value of the base station for the low-orbit satellite k.

6. The low-orbit satellite-based differential positioning method according to claim 5, characterized in that: According to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, according to the position information of the low-orbit satellites with different numbers at the start time and the end time of a Doppler counting cycle, an estimation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, which is recorded as a differential positioning estimation relationship, including: The error between the approximate position information of the mobile station and the real position information of the mobile station is recorded as the coordinate value (ΔX, ΔY, ΔZ), and the starting time t of the low-orbit satellite j and the low-orbit satellite k in a Doppler counting cycle is recorded as i-1 and end time t i The positions at the time are the coordinate values Coordinate value and coordinate values Coordinate value For formula (4), let ΔL * =Equal to the left side of formula (4), the approximate coordinates of the mobile station R and the sum of the errors (X R1 +ΔX,Y R1 +ΔY,Z R1 +ΔZ), the real coordinates of the base station (X B0 ,Y B0 ,Z B0 ) and satellites j and k at t i-1 and t i The coordinate value at the time is the approximate coordinate value (X R1 ,Y R1 ,Z R1 ) is expanded using Taylor's formula to obtain an estimation relationship for differential positioning based on the Doppler frequency of low-orbit satellites, which is recorded as the differential positioning estimation relationship; The differential positioning estimation relationship is formula (5):

7. The differential positioning method based on low-orbit satellites according to claim 1, characterized in that: Determining an error between the approximate position information of the mobile station and the actual position information of the mobile station according to the differential positioning observation relationship and the differential positioning estimation relationship includes: Subtracting the differential positioning observation relationship from the differential positioning estimation relationship to minimize the residual sum of squares, and using a least squares method to estimate an error between the approximate position information of the mobile station and the true position information of the mobile station; When two low-orbit satellites are observed, the error between the approximate position information of the mobile station and the actual position information of the mobile station is determined based on the estimated value of the error between the approximate position information of the mobile station and the actual position information of the mobile station under three Doppler counting cycles.

8. The low-orbit satellite-based differential positioning method according to any one of claims 1 to 7, characterized in that: Correcting the approximate location information of the mobile station according to an error between the approximate location information of the mobile station and the actual location information of the mobile station so that the approximate location information of the mobile station approaches the actual location information of the mobile station, thereby achieving positioning of the mobile station, including: Correcting the approximate location information of the mobile station according to an error between the approximate location information of the mobile station and the actual location information of the mobile station; re-determining an error between the approximate location information of the mobile station and the actual location information of the mobile station, and correcting the approximate location information of the mobile station based on the error between the re-determined approximate location information of the mobile station and the actual location information of the mobile station; This process is repeated until the approximate location information of the mobile station approaches the real location information of the mobile station, thereby achieving the positioning of the mobile station.

9. A differential positioning device based on low-orbit satellites, characterized in that: Used to achieve differential positioning based on the Doppler frequency of low-orbit satellites, the number of observations of the low-orbit satellites is n times, where n is a positive integer greater than or equal to 1; The differential positioning device based on low-orbit satellites includes: a control unit configured to determine a reference station and a mobile station; the reference station and the mobile station being capable of simultaneously receiving a signal transmitted by each of the low-orbit satellites; and the reference station being capable of transmitting its own observation information and prior information to the mobile station; an acquiring unit configured to acquire the location information of the reference station; acquire the approximate coordinates of the mobile station; acquire the local oscillator frequencies of the reference station and the mobile station; and acquire the number of each low-orbit satellite in the low-orbit satellites; The control unit is further configured to determine the real position information of the mobile station based on the approximate coordinates of the mobile station; determine, according to the number of each low-orbit satellite, an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellites and a difference between the position information of each low-orbit satellite at the start and end times of a Doppler counting cycle, the position information of the reference station, the real position information of the mobile station, and the local oscillator frequencies of the reference station and the mobile station, recorded as a differential positioning observation relationship; and determine an estimated relationship for differential positioning based on the Doppler frequency of the low-orbit satellites, recorded as a differential positioning estimated relationship; The control unit is further configured to determine an error between the approximate position information of the mobile station and the true position information of the mobile station based on the differential positioning observation relationship and the differential positioning estimation relationship; The control unit is further configured to correct the approximate location information of the mobile station based on the error between the approximate location information of the mobile station and the actual location information of the mobile station, so that the approximate location information of the mobile station approaches the actual location information of the mobile station, thereby realizing the positioning of the mobile station.

10. A storage medium, characterized in that: The storage medium includes a stored program, wherein when the program is running, the device where the storage medium is located is controlled to execute the differential positioning method based on low-orbit satellites according to any one of claims 1 to 8.

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