Differential positioning method and device based on low earth orbit satellite and storage medium

Abstract

The invention relates to the technical field of satellite positioning, and provides a differential positioning method and device based on a low earth orbit satellite and a storage medium, and the method comprises the steps: determining a reference station and a mobile station; determining a differential positioning observation relation and a differential positioning estimation relation according to the difference value of the position information of each low-orbit satellite at the starting moment and the ending moment of one Doppler counting period, the position information of the base station, the real position information of the mobile station and the local oscillation frequencies of the base station and the mobile station; determining an 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 relation and the differential positioning estimation relation; 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, and the positioning of the mobile station is realized. According to the scheme, positioning can be realized in a single Doppler observation period, and the positioning accuracy can be improved.

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 in particular 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 has increased explosively, and the announced low-orbit satellite constellation plan still has a large number of satellite launch plans. Against this background, the use of low-orbit satellites for navigation and positioning applications will usher in new breakthroughs. However, 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 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 period and improve the accuracy of positioning.

[0005] 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, 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 method based on low-orbit satellites comprises 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 oscillator frequencies 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 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 frequencies of the reference station and the mobile station are used to determine the observation relationship for differential positioning based on the low-orbit satellite Doppler frequency, 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; according to the differential positioning observation relationship and the differential positioning estimation relationship, the error between the approximate position information of the mobile station and the real position information of the mobile station is determined; according to the error between the approximate position information of the mobile station and the real 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 real 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, 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, 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 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 in the Doppler counting cycle, determining the observation relationship of the measured distance difference of the mobile station to the numbered low-orbit satellite; 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 in the Doppler counting cycle, determining the observation relationship of the measured distance difference of the mobile station to the numbered low-orbit satellite 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 numbered low-orbit satellite by the reference station 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 by 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 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, the 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.

[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 in the one Doppler counting cycle, the observation relationship of the mobile station to the measured distance difference of the numbered low-orbit satellite is determined, including: according to formula (1), determining the observation relationship of the mobile station to the measured distance difference of the numbered low-orbit satellite:

[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 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 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 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 reference station for the position of the numbered low-orbit satellite in the one Doppler counting cycle, determining the observation relationship of the reference station to the measured distance difference of the numbered low-orbit satellite, including: determining the observation relationship of the reference station to the measured distance difference of the numbered low-orbit satellite according to formula (2):

[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 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 base station to the low-orbit satellite j; Represents the measured distance difference of the base station to the low-orbit satellite j.

[0012] 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 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, after eliminating the satellite clock error, a single difference distance relationship of the numbered low-orbit satellite is obtained, including: 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; wherein the single difference distance relationship 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 between the mobile station and the low-orbit satellite j, represents the measured distance difference between the base 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 to the position of low-orbit satellite j, σt B0 represents the receiver clock error of the reference station 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 base station to the low-orbit satellite j.

[0015] 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 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 a 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 a differential positioning observation relationship; wherein the differential positioning observation relationship is as shown in formula (4):

[0016]

[0017] 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 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; represents the measured distance difference of the mobile station to 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 to 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 real position information of the mobile station as a coordinate value (ΔX, ΔY, ΔZ), and recording the start time t of the low-orbit satellite j and the low-orbit satellite k in a Doppler counting cycle i-1 and the end time t i The positions at Coordinate value and coordinate values Coordinate value For formula (4), let ΔL * =The left side of formula (4) is equal to 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 an estimation relationship for differential positioning based on the Doppler frequency of low-orbit satellites, 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 according to 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 residual sum of squares, 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 according to 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 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, 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 way until 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.

[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 satellite 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 reference station and a mobile station; the reference station and the mobile station can simultaneously receive signals 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; an acquisition unit is configured to acquire the position 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 also 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 satellite, The difference between the position information of the low-orbit satellites 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 are used to determine the observation relationship for differential positioning based on the low-orbit satellite Doppler frequency, 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; the control unit is also 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; the control unit is also 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 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 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 estimated 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 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 in the one Doppler counting cycle, determining the observation relationship of the measured distance difference of the mobile station to the numbered low-orbit satellite; 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 in the one 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 numbered low-orbit satellite within the Doppler counting cycle is used to determine the observation relationship of the reference station for the measured distance difference of the low-orbit satellite with this number; 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 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, after eliminating the satellite clock error, the single distance difference of the low-orbit satellite with this 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 the 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, 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 in the one Doppler counting cycle, determines 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 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, the control unit, 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 reference station for the position of the numbered low-orbit satellite in the one Doppler counting cycle, determines the observation relationship of the reference station to the measured distance difference of the numbered low-orbit satellite, including: determining the observation relationship of the reference station to the measured distance difference of the numbered low-orbit satellite 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 base station to the low-orbit satellite j; Represents the measured distance difference of the base station to the low-orbit satellite j.

[0029] 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 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, including: 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, and eliminating the satellite clock error to obtain the single-difference distance relationship of the numbered low-orbit satellite; wherein 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 of the mobile station to the low-orbit satellite j, represents the measured distance difference between the base 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 to the position of low-orbit satellite j, σt B0 represents the receiver clock error of the reference station 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 base 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 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 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; 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 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; represents the measured distance difference of the mobile station to 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 to 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 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: recording 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 recording the start time t of the low-orbit satellite j and the low-orbit satellite k in a Doppler counting cycle i-1 and the end time t i The positions at Coordinate value and coordinate values Coordinate value For formula (4), let ΔL * = The left side of formula (4) is equal to 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 an estimation relationship for differential positioning based on the Doppler frequency of low-orbit satellites, 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 residual sum of squares, 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 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 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 way until 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.

[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 a fast change in Doppler frequency. It can achieve positioning in a single Doppler observation period and can improve the accuracy of positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The diagram schematically shows the steps of a 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 of 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 location information of the mobile station approach the real location 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] Compared with traditional GNSS (Global Navigation Satellite System) navigation, the use of low-orbit satellites for navigation and positioning has the following advantages: (1) The received signal has a high signal-to-noise ratio, strong power, and little ionospheric influence, and has strong anti-interference ability; (1-1) The number of low-orbit satellites is large, and their geometric distribution varies greatly, which can improve the properties of the positioning equation and increase accuracy; (2) The Doppler frequency of low-orbit satellites changes rapidly. By utilizing this property, the real-time 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 a large number of low-orbit satellites and a fast change in Doppler frequency, can achieve positioning in a single Doppler observation cycle, 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 implement 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 the positioning result. Figure 1 As shown, the differential positioning method based on low-orbit satellites includes the following steps: step S110 to step S150. The number of observations can be multiple observations of the same group of satellites, or multiple groups of satellites can be observed at one time. When differential positioning is performed, Doppler counting observations are performed on visible satellites by the mobile station and the base station to determine the observation equation; two differences are performed only to eliminate the satellite clock error and the receiver clock error; the estimation equation is determined by the approximate coordinates and the real coordinates according to the distance difference; the difference between the two is made to minimize the error.

[0054] At step S110, a reference station and a mobile station are determined; the reference station and the mobile station can simultaneously receive signals transmitted by each low-orbit satellite; and the reference station can transmit its own observation information and prior information to the mobile station. Prior information: the reference station position coordinates, the local oscillator frequency fr of the reference station and the mobile station, the satellite signal transmission frequency ft, and the speed of light c, which are already known. Observation information: Doppler counts, satellite position information, which need to be observed in real time.

[0055] In step S120, the location information of the reference station is obtained. For example, the location information of the reference station is (X B0 , Y B0 , Z B0 ); obtaining the approximate coordinates of the mobile station, so as to determine the real location information of the mobile station according to the approximate coordinates of the mobile station as (X R0 , Y R0 , Z R0 ); obtain the local oscillator frequency of the reference station and the mobile station (such as f r ); and obtain the number of each low-orbit satellite in the low-orbit satellites, such as the first low-orbit satellite in the low-orbit satellites is numbered j, the second low-orbit satellite in the low-orbit satellites is numbered k, and so on.

[0056] Specifically, the implementation process of a differential positioning technology based on low-orbit satellite Doppler frequency proposed in the solution of the present invention includes: step 1, determining the location information (X) of the reference station B0 , Y B0 , Z B0 ), and the real position of the mobile station (X R0 , Y R0 , Z R0 ), determine the local oscillator frequency f of the reference station and the mobile station r , determine the numbers j and k of the low-orbit satellites, and then execute step 2 to obtain the observation equation of Doppler frequency difference positioning and the estimation equation of Doppler frequency difference positioning.

[0057] In the solution of the present invention, a reference station is required to realize differential positioning based on the Doppler frequency of low-orbit satellites. The position information of the reference station is accurately known and is set as (X B0 , Y B0 , Z B0 The location information of the mobile station needs to be estimated. Assume that the real location of the mobile station is (X R0 , Y R0 , Z R0 );The local oscillator frequencies of the base 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 transmission signal frequency of the low-orbit satellite is f t The position information of low-orbit satellites can be obtained in real time through TLE (Two-Line Orbital Element, two-line orbital data) files or ephemeris files.

[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 oscillator 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, recorded as the differential positioning observation relationship; and an estimation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, 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 ), find 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 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 oscillator frequency of the base station and the mobile station, the observation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, recorded as the differential positioning observation relationship; and the estimation relationship for differential positioning based on the low-orbit satellite Doppler frequency is determined, recorded as the specific process of the differential positioning estimation relationship, see the following exemplary description.

[0062] Combine the following 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 is shown, which 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 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, 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, the observation relationship of the mobile station to the measured distance difference of the low-orbit satellite with the number is determined in step S210, including: determining the observation relationship of the mobile station to the measured distance difference of the low-orbit satellite with the number 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 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 a low-orbit satellite j, record the time t of the low-orbit satellite j 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 count of the position of low-orbit satellite j is performed within the time period (time period), and the observed 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 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. 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 each time 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 represents the low-orbit satellite j at time t i The position at (X R0 , Y R0 , Z R0 ) represents the real position of the mobile station, 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 respective positions to the mobile station.

[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 base 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 with respect to the measured distance difference of the low-orbit satellite with this number.

[0074] In some embodiments, in 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 the 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 the number in the Doppler counting cycle, the observation relationship of the reference station to the measured distance difference of the low-orbit satellite with the number is determined, including: determining the observation relationship of the reference station to the measured distance difference of the low-orbit satellite with the number 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 base station to the low-orbit satellite j; Represents the measured distance difference of 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 also 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 Represents the satellite clock error. It represents the Doppler count observation value of the base station to the low-orbit satellite j. Represents the measured distance difference of 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 base station for the low-orbit satellite with this number, after eliminating the satellite clock error, the single difference distance relationship of the low-orbit satellite with this number is obtained.

[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, based on the observation relationship of the measured distance difference of the mobile station for the low-orbit satellite with the number and the observation relationship of the measured distance difference of the reference station for the low-orbit satellite with the number, after eliminating the satellite clock error, 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 for the low-orbit satellite with the number and the observation relationship of the measured distance difference of the reference station for the low-orbit satellite with the number are performed as inter-station single difference, and after eliminating the satellite clock error, the single-difference distance relationship of the low-orbit satellite with the number is obtained.

[0082] Among them, 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 base 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 to the position of low-orbit satellite j, σt B0 represents the receiver clock error of the reference station 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 base 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 base 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 subjected to inter-station single difference. After the satellite clock error of the observation information of the base station and the mobile station on the position of the low-orbit satellite j is eliminated, 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, It represents the measured distance difference between the base station and the low-orbit satellite j. 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 to the position of low-orbit satellite j, σt B0 Represents the receiver clock error of the reference station 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 base 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 of the mobile station to the low-orbit satellite k, It represents the measured distance difference between the base station and the low-orbit satellite k. 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 to the position of the low-orbit satellite k, σt B0 Represents the receiver clock error of the reference station 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 to the low-orbit satellite k.

[0092] 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 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, 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 between 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 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; represents the measured distance difference of the mobile station to 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 to 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] 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 time and end time of a Doppler counting cycle, determine the estimated relationship for differential positioning based on the low-orbit satellite Doppler frequency, 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 the 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] Combine the following Figure 3 The flowchart of an embodiment of determining the differential positioning estimation relationship in the method of the present invention is shown, which further illustrates the specific process of determining the differential positioning estimation relationship in step S250, including: step S310 to step 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 the end time t i The positions at Coordinate value and coordinate values Coordinate value

[0105] Step S320, substitute the above coordinate value into formula (4), and replace the above coordinate value with the coordinate value 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 as follows:

[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 Substitute the approximate coordinate value of the mobile station into the left side of equation (4), and replace the above coordinate value in (X R1 , Y R1 , Z R1 ) is expanded by Taylor formula and the high-order terms are ignored, and the estimation equation for Doppler frequency differential positioning is obtained as follows:

[0110]

[0111] At step S140, the error between the approximate location information of the mobile station and the real location information of the mobile station is determined according to 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 ), and then execute 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 approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ), then execute step 5 to make the approximate position (X R1 , Y R1 , Z R1 ) approaches the true position (X R0 , Y R0 , Z R0 ) to achieve positioning.

[0113] In some implementations, 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 according to the differential positioning observation relationship and the differential positioning estimation relationship in step S140 is described in the following exemplary embodiment.

[0114] Combine the following 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, subtracting the differential positioning observation relationship from the differential positioning estimation relationship to minimize the residual sum of squares, and using the least squares method to estimate the error between the approximate location information of the mobile station and the actual location information of the mobile station.

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

[0117] In step 3, in the above formula, By subtracting the observed equation (4) from the estimated equation (5), we can get the residual formula (6):

[0118]

[0119] In the formula, 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 equation (6) are ΔX, ΔY and ΔZ, so the positioning result can be obtained by making three 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 sum of squares. Let the number of observations be n, q be the number of observations, and the residual sum of squares can be expressed as

[0120] To solve for ΔX, ΔY, and ΔZ, the residual sum of squares is The partial derivatives at ΔX, ΔY, and ΔZ are zero, and we can get:

[0121]

[0122] Substituting formula (6) into formula (7) and expanding it, we can get:

[0123]

[0124]

[0125]

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

[0127] Step S420, when two low-orbit satellites are observed, determine the error between the approximate position information of the mobile station and the actual position information of the mobile station 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.

[0128] 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: in step 4, when two stars are observed, three Doppler counting cycles are required 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 two satellites. 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 real 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 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.

[0130] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed by 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 ) to achieve 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), and the advantages of a large number of low-orbit satellites and a fast change in Doppler frequency are fully utilized. Positioning can be achieved in a single Doppler observation period and the accuracy of positioning can be improved.

[0132] In some embodiments, in 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 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] Combine the following Figure 5 The flowchart of an embodiment of making the approximate location information of the mobile station approach the real location information of the mobile station in the method of the present invention 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 real 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 according to 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 the positioning of the mobile station.

[0137] 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: 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 ) is corrected, and equation (8) is used again to calculate and obtain the approximate coordinates of mobile station R and the real coordinates of 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 ) to achieve 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 fast Doppler frequency changes, can achieve positioning in a single Doppler observation period, and can improve the accuracy of positioning.

[0139] According to a second embodiment of the present invention, a differential positioning device based on a low-orbit satellite is provided, which is used to implement 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, and n is a positive integer greater than or equal to 1. Figure 6 As shown, the differential positioning device based on low-orbit satellite 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 its own observation information and prior information to the mobile station. The specific functions and processing of the control unit 104 refer to step s110.

[0141] The acquisition unit 102 is configured to acquire the location information of the reference station, such as the location information of the reference station is (X B0 , Y B0 , Z B0 ); obtaining the approximate coordinates of the mobile station, so as to determine the real location information of the mobile station according to the approximate coordinates of the mobile station as (X R0 , Y R0 ), Z R0 ); obtain the local oscillator frequency of the reference station and the mobile station (such as f r ); and obtain the number of each low-orbit satellite in the low-orbit satellites, such as the first low-orbit satellite in the low-orbit satellites is numbered j, the second low-orbit satellite in the low-orbit satellites is numbered k, and so on. The specific function and processing of the acquisition unit 102 refer to step S120.

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

[0143] In the solution of the present invention, a reference station is required to realize differential positioning based on the Doppler frequency of low-orbit satellites. The position information of the reference station is accurately known and is set as (X B0 , Y B0 , Z B0 The location information of the mobile station needs to be estimated. Assume that the real location of the mobile station is (X R0 , Y R0 , Z R0 );The local oscillator frequencies of the base station and the mobile station are both f rThey 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 transmission signal frequency of the low-orbit satellite is f t The position information of low-orbit satellites can be obtained in real time through TLE (Two-Line Orbital Element, two-line orbital data) files or ephemeris files.

[0144] The control unit 104 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 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 oscillator frequency of the reference station and the mobile station, determine the observation relationship of differential positioning based on the low-orbit satellite Doppler frequency, recorded as the differential positioning observation relationship; and determine the estimation relationship of differential positioning based on the low-orbit satellite Doppler frequency, recorded as the differential positioning estimation relationship. The specific functions and processing of the control unit 104 are also shown in step S130.

[0145] According to the approximate coordinates of the mobile station, such as the coordinate value (X R1 , Y R1 , Z R1 ), find 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 according to the approximate coordinates of the mobile station; determines the observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite 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, recorded as the differential positioning observation relationship; and determines the estimation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite, recorded as the differential positioning estimation relationship, including:

[0148] The control unit 104 is further configured to determine, 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 in the Doppler counting cycle, the observation relationship of the mobile station to the measured distance difference of the numbered low-orbit satellite. The specific functions and processing of the control unit 104 are also shown 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, 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 Doppler counting cycle, the observation relationship of the mobile station to 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 to 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 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.

[0152] 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.

[0153] In step 21, for a low-orbit satellite j, record the time t of the low-orbit satellite j 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 count of the position of low-orbit satellite j is performed within the time period (time period), and the observed distance difference between the mobile station and the low-orbit satellite j can be obtained as follows:

[0154]

[0155] 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 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. 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 each time can also be expressed as equation (1-1):

[0156]

[0157] In formula (1-1), represents the low-orbit satellite j at time t i-1 The position at represents the low-orbit satellite j at time t i The position at (X R0 , Y R0 , Z R0 ) represents the real position of the mobile station, 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 respective positions to the mobile station.

[0158] The control unit 104 is further configured to determine, according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, 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, the observation relationship of the reference station to the measured distance difference of the numbered low-orbit satellite. The specific functions and processing of the control unit 104 are also shown 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, 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 reference station for the position of the numbered low-orbit satellite in the Doppler counting cycle, the observation relationship of the reference station to 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 to 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 base station to the low-orbit satellite j; Represents the measured distance difference of 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 also 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 Represents the satellite clock error. It represents the Doppler count observation value of the base station to the low-orbit satellite j. Represents the measured distance difference of the base station to the low-orbit satellite j.

[0165] The control unit 104 is further configured to obtain the single difference distance relationship of the numbered low-orbit satellite according to the number of each low-orbit satellite in the low-orbit satellites, for each numbered low-orbit satellite, after eliminating the satellite clock error according to the observed relationship of the measured distance difference of the numbered low-orbit satellite by the mobile station and the observed relationship of the measured distance difference of the numbered low-orbit satellite by the reference station. The specific functions and processing of the control unit 104 are also shown in step S230.

[0166] In some implementations, the control unit 104, 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 observed relationship of the measured distance difference of the mobile station with the numbered low-orbit satellite and the observed relationship of the measured distance difference of the reference station with the numbered low-orbit satellite, to obtain the single difference distance relationship of the numbered low-orbit satellite, including:

[0167] The control unit 104 is further specifically configured to perform inter-station single difference on the observation relationship of the mobile station with respect to the low-orbit satellite with the number, and the observation relationship of the reference station with respect to the low-orbit satellite with the number, according to the number of each low-orbit satellite in the low-orbit satellites, and after eliminating the satellite clock error, obtain the single difference distance relationship of the low-orbit satellite with the number.

[0168] Among them, 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 between the base 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 to the position of low-orbit satellite j, σt B0 represents the receiver clock error of the reference station 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 base station to the low-orbit satellite j.

[0171] 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.

[0172] In step 22, the observation information of the base 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 subjected to inter-station single difference. After the satellite clock error of the observation information of the base station and the mobile station on 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, It represents the measured distance difference between the base station and the low-orbit satellite j. 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 to the position of low-orbit satellite j, σt B0 Represents the receiver clock error of the reference station 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 base station to the low-orbit satellite j.

[0175] Similarly, the single difference distance equation (3-1) of 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, It represents the measured distance difference between the base station and the low-orbit satellite k. 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 to the position of the low-orbit satellite k, σt B0 Represents the receiver clock error of the reference station 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 to the low-orbit satellite k.

[0178] The control unit 104 is further configured to obtain an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite after eliminating the receiver clock error according to the single difference distance relationship between the low-orbit satellites with different numbers according to the number of each low-orbit satellite in the low-orbit satellite, and record it as the differential positioning observation relationship. The specific functions and processing of the control unit 104 are also shown in step S240.

[0179] In some embodiments, the control unit 104, according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, performs inter-satellite single difference on the single-difference distance relationship between low-orbit satellites with different numbers, eliminates the receiver clock error, and obtains the observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite, which is recorded as the differential positioning observation relationship, including: the control unit 104 is further specifically configured to, according to the number of each low-orbit satellite in the low-orbit satellites, for low-orbit satellites with different numbers, perform inter-satellite single difference on the single-difference distance relationship between low-orbit satellites with different numbers, eliminate the receiver clock error, and obtain the observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite, which is recorded as the differential positioning observation relationship.

[0180] The differential positioning observation relationship is as follows:

[0181]

[0182] 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 of the reference station to the low-orbit satellite j; represents the measured distance difference of the mobile station to 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 to 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, according to the number of each low-orbit satellite in the low-orbit satellite, an estimated relationship for differential positioning based on the low-orbit satellite Doppler frequency 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, and record it as a differential positioning estimated relationship. The specific functions and processing of the control unit 104 are also shown in step S250.

[0188] In some embodiments, the control unit 104 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 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, recorded as a differential positioning estimation 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 cyclei-1 and the end time t i The positions at Coordinate value and coordinate values Coordinate value The specific functions and processing of the control unit 104 also refer to step s310.

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

[0191] The differential positioning estimation relationship is as follows:

[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 high-order terms are ignored, and the estimation equation for Doppler frequency differential positioning is obtained as follows:

[0195]

[0196] The control unit 104 is further configured to determine the error between the approximate location information of the mobile station and the real location information of the mobile station according to 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 ), and then execute 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 approximate coordinates of the mobile station R and the real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ), then execute step 5 to make the approximate position (X R1 , Y R1 , Z R1 ) approaches the true position (X R0 , Y R0 , Z R0 ) to achieve positioning.

[0198] In some implementations, the control unit 104 determines the error between the approximate location information of the mobile station and the actual location information of the mobile station according to the differential positioning observation relationship and the differential positioning estimation relationship, including:

[0199] The control unit 104 is further configured to perform a difference between the differential positioning observation relationship and the differential positioning estimation relationship, minimize the residual square sum, and use the least square method to estimate the error between the approximate location information of the mobile station and the real location information of the mobile station. The specific functions and processing of the control unit 104 are also referred to step S410.

[0200] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed by 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 get the residual formula (6):

[0202]

[0203] In the formula, 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 equation (6) are ΔX, ΔY and ΔZ, so the positioning result can be obtained by making three 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 sum of squares. Let the number of observations be n, q be the number of observations, and the residual sum of squares can be expressed as

[0204] To solve for ΔX, ΔY, and ΔZ, the residual sum of squares is 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 both known quantities.

[0211] The control unit 104 is further configured to determine the error between the approximate location information of the mobile station and the real location information of the mobile station according to the estimated value of the error between the approximate location information of the mobile station and the real location information of the mobile station in three Doppler counting cycles when two low-orbit satellites are observed. The specific functions and processing of the control unit 104 are also shown in step S420.

[0212] 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: in step 4, when two stars are observed, three Doppler counting cycles are required 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 two satellites. 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 real coordinates of the mobile station R (X R0 , Y R0 , Z R0 ) between (ΔX, ΔY, ΔZ).

[0213] The control unit 104 is further configured to correct 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 tends to the real location information of the mobile station, thereby realizing the positioning of the mobile station. The specific functions and processing of the control unit 104 are also referred to step S150.

[0214] Specifically, the implementation process of a differential positioning technology based on the low-orbit satellite Doppler frequency proposed by the solution of the present invention also includes: step 5, making the approximate position (X R1 , Y R1 , Z R1 ) approaches the true position ( XR 0, Y R0 , Z R0 ) to achieve positioning.

[0215] In some implementations, the control unit 104 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:

[0216] The control unit 104 is further configured to correct 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. The specific functions and processing of the control unit 104 are also shown 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 real location information of the mobile station, and correct 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. The specific functions and processing of the control unit 104 are also shown in step S520.

[0218] The control unit 104 is further configured to iterate in this way until 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. The specific functions and processing of the control unit 104 are also shown in step S530.

[0219] 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: 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 ) is corrected, and equation (8) is used again to calculate and obtain the approximate coordinates of mobile station R and the real coordinates of 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 ) to achieve 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), and the advantages of a large number of low-orbit satellites and a fast change in Doppler frequency are fully utilized. Positioning can be achieved in a single Doppler observation period and the accuracy of positioning can be improved.

[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 the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0222] According to a third embodiment of the present invention, a storage medium is provided, wherein the storage medium includes a stored program, wherein when the program is executed, 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 the details not fully described in this embodiment, please refer to the relevant descriptions in the aforementioned embodiments, and no further elaboration will be made here.

[0224] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A differential positioning method based on low-orbit satellites, characterized in that: Used to realize differential positioning based on the Doppler frequency of low-orbit satellites, 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: Determine a reference station and a mobile station; the reference station and the mobile station can simultaneously receive a signal transmitted by each low-orbit satellite; and the reference station can transmit its own observation information and prior information to the mobile station; Acquiring 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 serial 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; According to the number of each low-orbit satellite in the low-orbit satellites, 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 oscillator frequency of the reference station and the mobile station, an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite is determined, which is recorded as the differential positioning observation relationship; And determine the estimation relationship for differential positioning based on the low-orbit satellite Doppler frequency, which is recorded as the differential positioning estimation relationship; Determining an error between the approximate location information of the mobile station and the actual location information of the mobile station according to 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 satellite according to claim 1, characterized in that: According to the approximate coordinates of the mobile station, the real position information of the mobile station is determined; 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, an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite is determined, which is recorded 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 in the low-orbit satellites, for each low-orbit satellite with a number, 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, determine the observation relationship of the mobile station for the measured distance difference of the low-orbit satellite with the number; According to the number of each low-orbit satellite in the low-orbit satellites, for each low-orbit satellite with a number, 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 reference station for the position of the low-orbit satellite with the number in the Doppler counting cycle, determining the observation relationship of the reference station for the measured distance difference of the low-orbit satellite with the number; According to the number of each low-orbit satellite in the low-orbit satellites, for each low-orbit satellite with a number, according to the observation relationship of the mobile station on the measured distance difference of the low-orbit satellite with the number and the observation relationship of the reference station on the measured distance difference of the low-orbit satellite with the number, after eliminating the satellite clock error, a single difference distance relationship 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 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 satellite count, 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 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 satellite according to claim 2, characterized in that: in, According to the number of each low-orbit satellite in the low-orbit satellites, for each low-orbit satellite with a number, according to the difference in position information of the low-orbit satellite with the number at a start time and an 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 an observation relationship of the mobile station with respect to the measured distance difference of the low-orbit satellite with the number, including: According to formula (1), the observation relationship of the mobile station to the measured distance difference of the numbered low-orbit satellite 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; 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 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 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 reference station for the position of the numbered low-orbit satellite in the one Doppler counting cycle, determining the observation relationship of the reference station to 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; 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 base station to the low-orbit satellite j; Represents the measured distance difference of the base station to the low-orbit satellite j.

4. The differential positioning method based on low-orbit satellite according to claim 2, characterized in that: According to the number of each low-orbit satellite in the low-orbit satellites, for each low-orbit satellite with a number, according to the observation relationship of the mobile station's measured distance difference for the low-orbit satellite with the number, and the observation relationship of the reference station's measured distance difference for the low-orbit satellite with the number, after eliminating the satellite clock error, a 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, perform inter-station single difference 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, 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 of the mobile station to the low-orbit satellite j, represents the measured distance difference between the base 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 to the position of low-orbit satellite j, σt B0 represents the receiver clock error of the reference station 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 base station to the low-orbit satellite j.

5. The differential positioning method based on low-orbit satellite according to claim 2, characterized in that: According to the number of each low-orbit satellite in the low-orbit satellite, 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 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 made into inter-satellite single difference, and 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; represents the measured distance difference between the mobile station and the low-orbit satellite j, represents the measured distance difference of the reference station to the low-orbit satellite j; represents the measured distance difference of the mobile station to 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 to the low-orbit satellite k.

6. The differential positioning method based on low-orbit satellite 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 Doppler frequency of the low-orbit satellite 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 the end time t i The positions at Coordinate value and coordinate values Coordinate value For formula (4), let ΔL * =The left side of formula (4) is equal to 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 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 differential positioning estimation relationship is as follows:

7. The differential positioning method based on low-orbit satellite according to claim 1, characterized in that: Determining the error between the approximate location information of the mobile station and the real location 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 the least squares method to estimate an estimated value of the error between the approximate location information of the mobile station and the true location 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 differential positioning method based on low-orbit satellite according to any one of claims 1 to 7, characterized in that: 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, 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 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; This iteration is performed 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 a low-orbit satellite, characterized in that: Used to realize differential positioning based on the Doppler frequency of low-orbit satellites, 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 includes the following steps: A control unit is configured to determine a reference station and a mobile station; the reference station and the mobile station are capable of simultaneously receiving a signal 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; an acquiring unit, configured to acquire the location information of the reference station; Obtaining the approximate coordinates of the mobile station; obtaining the local oscillator frequencies of the reference station and the mobile station; And obtain the serial number of each low-orbit satellite in the low-orbit satellite; The control unit is further configured to determine the real location 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 satellites, 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 oscillator frequency of the reference station and the mobile station, an observation relationship for differential positioning based on the Doppler frequency of the low-orbit satellite is determined, which is recorded as the differential positioning observation relationship; And determine the estimation relationship for differential positioning based on the low-orbit satellite Doppler frequency, which is recorded as the differential positioning estimation relationship; The control unit is further configured to determine an error between the approximate location information of the mobile station and the real location information of the mobile station according to 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 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.

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 as described in any one of claims 1 to 8.

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