Beidou / Roland fusion positioning time service method

Abstract

The invention relates to a Beidou / Rowland fusion positioning time service method, and belongs to the technical field of communication. Comprising the steps that if it is detected that the number of available satellites is not less than four, positioning time service is carried out in the mode that the available satellites and a Rowland station are fused, and only the satellites and Rowland are used for standby application during calculation at the moment; if it is detected that the number of available satellites is less than four, but there are three satellites, four satellites are supplemented by Roland to carry out positioning time service; and if no available satellite is detected, independent Roland positioning time service is carried out. According to the method, backup can be added for a single Beidou system, the situation that once a satellite is unavailable, calculation can also be carried out through Rowland is avoided, and the risk that the service of a positioning time service system is stopped due to sudden failure of the satellite is avoided; the anti-interference capability of the positioning time service system is improved, and the stability of the positioning time service system is improved.

Description

Technical Field

[0001] The invention belongs to the field of communication technology, and in particular relates to a Beidou / Loran fusion positioning and timing method. Background Art

[0002] The BeiDou Navigation Satellite System is a global satellite navigation system independently developed and operated by China. It is part of the global satellite navigation system. The BeiDou-3 system provides navigation services with global coverage. It can not only provide high-precision services to users in China and surrounding areas, but also provide diversified navigation services to users around the world. At present, the BeiDou system has high performance and plays an important role in transportation, logistics management, agricultural automation, emergency rescue, public safety and national defense.

[0003] Although the BeiDou system has made remarkable achievements in positioning, navigation and timing services, there are still some shortcomings and challenges. In terms of security, the BeiDou system faces various security threats, including interference, spoofing attacks and cyber attacks. These attacks may lead to misleading positioning information, which will have a serious impact on transportation, military and other key applications. In addition, garbage, aircraft wreckage, meteorites, etc. in space will threaten the safety of satellites. In addition, modern society is highly dependent on the BeiDou system. Once the system fails or is attacked, it may have a major impact on key infrastructure such as transportation, communications, and finance.

[0004] It is widely believed that the Loran system is the most suitable backup system for satellite-based navigation and timing systems. It is necessary to build a long-wave system as a backup for satellite navigation systems to cope with signal anomalies. However, using the Loran system as a simple backup cannot completely solve the problem. In order to improve the availability of the navigation, positioning and timing system, it is possible to consider fusing the Beidou signal with the Loran signal and use the fused signal for positioning and timing.

[0005] The prior art proposes the use of the Beidou system and a single Loran station for combined positioning, and proposes a correction-fusion combined positioning algorithm to correct the Loran C system error. This method realizes the fusion positioning of three or more satellites and one Loran station. This method only realizes the fusion of three Beidou satellites and one Loran station, and in reality there are still situations where the number of Beidou satellites is less than three. Therefore, this method cannot meet the needs of fusion positioning and timing of the Beidou system and the Loran system in all cases. Summary of the invention

[0006] The technical problems to be solved by the present invention are:

[0007] In order to avoid the problem that a single satellite system fails and causes failures in the fields of transportation, communication, finance, etc., and to improve the availability of the system, the present invention proposes a Beidou / Loran fusion positioning and timing method for solving the Beidou system / Loran system fusion when the number of available satellites is different.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] A Loran pseudo-range timing positioning method based on Vincenty formula is characterized in that positioning and timing are performed by integrating satellites and Loran stations. The formula is as follows:

[0010]

[0011] Among them, ρ 1 -ρ n is the n satellite pseudoranges measured by the receiver, n ≥ 4, ρ l1 -ρ lm is the pseudorange of m Loran stations measured by the receiver, m>0; (x 1 ,y 1 ,z 1 )-(x n ,y n ,z n ) represents the location of the Beidou satellite launch station, (x l1 ,y l1 ,z l1 )-(x lm ,y lm ,z lm ) represents the location of the Loran system transmitter; Δt represents the receiver clock error; x r ,y r ,z r represents the receiver coordinates; c is the speed of light; ε 1 -ε n , ε l1 -ε lm is other error;

[0012] The corresponding number of Lorans is selected according to the number of available satellites detected, so that the sum of the number of satellites and the number of Lorans is at least equal to 4; and the equations of the above equation group are adjusted according to the number of satellites and the number of Lorans.

[0013] A further technical solution of the present invention is to adjust the equations of the above equations according to the number of satellites and Loran, including:

[0014] If only three available satellites are detected, the three satellites are integrated with Loran for positioning and timing. The formula is as follows:

[0015]

[0016] If only two available satellites are detected, the two satellites are combined with Loran to perform positioning and timing. The formula is as follows:

[0017]

[0018] If no available satellites are detected, individual Loran station positioning and timing will be performed.

[0019] A further technical solution of the present invention is that the independent Loran station positioning and timing adopts a Loran pseudo-range timing and positioning method based on the Vincenty formula, comprising:

[0020] Select a Loran station chain whose broadcast signal range includes the receiver location, and obtain the longitude and latitude coordinates of a main station and two secondary stations in the Loran station chain;

[0021] Use a receiver to measure the arrival time of the signals transmitted by the three stations to the receiver;

[0022] According to the latitude and longitude coordinates of the three stations, the arrival time and the initial coordinates of the receiver, the new receiver coordinates and time are calculated based on the Vincenty ranging formula;

[0023] The coordinates of the new receiver are converted from the ellipsoid reference surface to the latitude and longitude of the actual earth surface to obtain the receiver coordinates and time.

[0024] A further technical solution of the present invention is: the method of calculating new coordinates and time based on the Vincenty ranging formula according to the latitude and longitude coordinates of the three stations, the arrival time and the initial coordinates of the receiver; comprising:

[0025] Get the initial coordinates of the receiver;

[0026] The latitude and longitude coordinates of the three stations are used to express the Vincenty ranging formula, and a differential equation system is constructed based on the Vincenty ranging formula;

[0027] Perform first-order Taylor expansion of the differential equations at the initial coordinates to obtain a partial differential equation system;

[0028] The iterative convergence threshold is set, and the partial differential equations are iteratively solved to obtain the receiver position and time.

[0029] A further technical solution of the present invention: the differential equation group is specifically:

[0030]

[0031] Among them, ρ i represents the pseudorange measured by the receiver, represents the Vincenty distance formula, ti represents the receiver time difference, δ i represents other error terms, and c is the speed of light.

[0032] A further technical solution of the present invention: the partial differential equation system is specifically:

[0033]

[0034] Among them, D i is the true distance, is the product of the arrival time and the speed of light, ρ i0 is the pseudorange from the Loran station to the receiver, For ρ The partial derivatives of λ and t in ρ i0 The value of Δλ, Δt are The change of λ and t.

[0035] A computer system, characterized in that it comprises: one or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned method.

[0036] A computer-readable storage medium, characterized in that it stores computer-executable instructions, which are used to implement the above method when executed.

[0037] A computer program product, characterized by comprising computer executable instructions, wherein the instructions are used to implement the above method when executed.

[0038] The beneficial effects of the present invention are:

[0039] The present invention provides a Beidou / Loran fusion positioning and timing method, which solves the problem of Beidou system / Loran system fusion when the number of available satellites is different. When the number of available satellites is not less than four, only three, only two or one, or no available satellite, a method of using the Loran system to enhance the Beidou system is proposed, that is, a method of fusing three satellites with Loran and a method of fusing two / one satellite with Loran.

[0040] The present invention also proposes a method for converting from an Earth-centered Earth-fixed coordinate system to a rectangular coordinate system. Only with this coordinate conversion can the satellite and Loran be combined for pseudo-range ground solution.

[0041] The method of the present invention can add a backup for a single Beidou system to avoid the situation where once a satellite is unavailable, Loran can also be used for calculation, thereby solving the risk of stopping the positioning and timing system service due to sudden failure of the satellite; improving the anti-interference ability of the positioning and timing system and improving its stability; and being an important requirement for maintaining national defense security. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0043] Figure 1 Flowchart of the Beidou / Loran fusion positioning and timing method of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] Considering the failure of the satellite system, which causes some or all satellite signals to be unavailable, the integration methods of the BeiDou system and the Loran system can be divided into the following four strategies:

[0046] 1) Loran system enhances satellite resilience: no less than four available satellites;

[0047] 2) Single station and satellite fusion of Loran system: there are only three available satellites;

[0048] 3) Loran system and satellite fusion pseudo-range solution: only one or two satellites are available;

[0049] 4) Independent solution of Loran system: No satellites available.

[0050] The coordinate system used by the BeiDou system for pseudo-range positioning and timing is a spatial rectangular coordinate system, while the coordinate system used by the Loran system for pseudo-range positioning and timing is an Earth-centered Earth-fixed coordinate system. In order to achieve fusion pseudo-range solution, the coordinate system needs to be unified first.

[0051] The pseudo-range positioning method requires the distance between the receiver and the transmitter to be measured. The Loran system uses the geodetic distance measurement method. When calculating the geodetic distance, the equivalent spherical calculation is generally used. It is necessary to convert the geodetic longitude and latitude into spherical longitude and latitude. If the latitude, longitude, and elevation of a point on the earth's surface are (B, L′, h), the corresponding spherical longitude and latitude are

[0052]

[0053] Then convert it into the coordinates in the rectangular coordinate system (x, y, z):

[0054]

[0055] Where f is the flattening of the reference ellipsoid, N is the radius of curvature of the ellipsoid, and e is 2 is the eccentricity of the ellipsoid; N and e 2 The calculation method is:

[0056]

[0057] Among them, a is the major axis of the earth, and b is the minor axis of the earth.

[0058] The Loran pseudo-range measurement formula can be written as:

[0059] ρ=A·(σ-Δσ)=L(x,y,z) (5)

[0060] Where ρ is the Loran pseudorange, A, σ, and Δσ represent the parameters required to solve the Loran pseudorange in the Earth-centered Earth-fixed coordinate system, and L represents the function for solving the Loran pseudorange in the direct coordinate system.

[0061] The fusion positioning equations of strategy 2) can be written as:

[0062]

[0063] Among them, ρ 1 , 2 , 3 are the three satellite pseudoranges measured by the receiver, ρ 4 is the pseudorange of the Loran system; (x 1 ,y 1 ,z 1 )、(x 2 ,y 2 ,z 2 )、(x 3 ,y 3 ,z 3 ) represents the location of the Beidou satellite launch station, (x 4 ,y 4 ,z 4 ) represents the location of the Loran system transmitter; Δt represents the receiver clock error; c is the speed of light; ε 1 , ε 2 , ε 3 , ε 4 is other error, x r ,y r ,z rIndicates the receiver coordinates.

[0064] Substituting equation (6) for x r ,y r 、z r By taking partial derivatives, we can obtain the differential equation system:

[0065]

[0066] Among them, r i is the distance between two points in space, i = 1, 2, 3. Solve L for x r ,y r 、z r Partial derivative of:

[0067]

[0068] Solving for ρ The method of partial derivative of λ can refer to strategy 4).

[0069] Solve Now λ vs x r ,y r 、z r The partial derivative of :

[0070]

[0071] in,

[0072]

[0073] Substituting formulas (9)-(13) into (8), the iterative method can be used to solve the positioning problem and obtain x r ,y r ,z r and Δt.

[0074] Strategy 1) can be realized by expanding the equation set of strategy 2) to no less than four satellites and one or more Loran stations whose signals can be received by the receiver.

[0075] The fusion positioning and timing equations of strategy 1) are written as:

[0076]

[0077] Among them, ρ 1 -ρ n is the n satellite pseudoranges (n≥4) measured by the receiver, ρ l1 -ρ lm is the pseudorange of m Loran stations measured by the receiver (m>0). The meanings of the remaining terms are consistent with those in equation (6). l1 ,y l1 ,zl1 ) is the position of the first transmitter, (x lm ,y lm ,z lm ) is the position of the mth transmitter. 1 -ε n , ε l1 -ε lm For other errors.

[0078] Strategy 3) Use the BeiDou system to calculate the receiver's position in advance and consider it as the real position. Calculate the distance between the receiver's position and the Loran system transmitter as a pseudorange. Since the Loran system transmitter is fixed on the surface of the earth, it does not move relative to the receiver like non-geostationary satellites. Therefore, when the receiver is stationary or has only a slight displacement, it can maintain positioning and timing by measuring only the positions of the two satellites and the pseudorange.

[0079] The pseudorange equations at this time are written as:

[0080]

[0081] Among them, ρ 1 -ρ 2 is the pseudorange of two satellites measured by the receiver, ρ l1 -ρ lm is the pseudorange of m Loran stations measured by the receiver (m ≥ 2). The meanings of the remaining terms are consistent with those in equation (14).

[0082] When there are no available satellites, strategy 4) will be used, using the Loran system entirely for positioning and timing.

[0083] The method for positioning and timing using the Loran system includes the following steps:

[0084] Step 1: Positioning and timing calculation process:

[0085] First, select a Loran station chain whose broadcast signal range includes the receiver location, and obtain the longitude and latitude coordinates of a main station and two secondary stations in the station chain; if stations in different stations are selected, time synchronization must be completed; then use the Loran receiver to measure the signal arrival time from each station to the receiver, input the coordinates of the three stations and the corresponding arrival time into the solution program, input the initial value of the receiver, and set the convergence threshold, then the longitude and latitude of the receiver location and the time of the solution moment can be solved;

[0086] Step 2: Solution method:

[0087] Define the latitude of the reference ellipsoid containing the unknown The differential equations for longitude λ and time t are:

[0088]

[0089] Among them, ρ i represents the pseudorange measured by the receiver, represents the Vincenty distance formula, t i represents the receiver time difference, δ i Represents other error terms. t=t 0 Performing a first-order Taylor expansion at , we get the partial differential equations:

[0090]

[0091] Among them, D i is the true distance, that is, the measurement value after eliminating the error term. The system of equations is expressed in matrix form:

[0092] B=A·X (18)

[0093]

[0094] in,

[0095]

[0096] Next, each partial differential term will be calculated.

[0097] To calculate σ The partial derivative of λ, let u = sinσ, v = cosσ,

[0098]

[0099]

[0100] in,

[0101]

[0102] Find A and B pairs Partial derivative of λ:

[0103]

[0104]

[0105] in,

[0106]

[0107] Find the Δσ pair Partial derivative of λ:

[0108] make:

[0109]

[0110]

[0111] in,

[0112]

[0113] Substituting formulas (17)-(40) into formula (16), and iterating through formula (41), the receiver position and time can be solved.

[0114] The initial value selection method of step one is:

[0115] Use the hyperbolic positioning method to obtain the initial value of the receiver, and set the convergence threshold of the longitude and latitude of the hyperbolic positioning method to no more than ±10 degrees.

[0116] The convergence threshold setting method for step 1 is:

[0117] Set the iteration convergence threshold to less than 10 -6 (radians), that is Δλ<10 -6 At this time, the corresponding latitude and longitude distance error is less than 7 meters. Note that you can continue to reduce the convergence threshold, but this will increase the number of iterations.

[0118] In order to enable those skilled in the art to better understand the present invention, the present invention is described in detail below in conjunction with specific embodiments.

[0119] like Figure 1 As shown in the process, when the Beidou-Loran fusion positioning and timing system is working, it will first detect the number of available satellites.

[0120] (1) If the number of available satellites detected is not less than four, the system will use the method of formula (14), that is, the method of integrating not less than four satellites with the Loran station to perform positioning and timing;

[0121] (2) If it is detected that the number of available satellites is less than four, but there are three, then the method of formula (6) is used to perform fusion positioning and timing of the three satellites and the Loran station;

[0122] (3) If it is detected that the number of available satellites is less than three, but there are two or one, then the method of formula (15) is used to perform fusion positioning and timing of two or one satellites and the Loran station;

[0123] (4) If no available satellite is detected, a separate Loran positioning and timing will be performed.

[0124] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be included in the protection scope of the present invention.

Claims

1. A Loran pseudo-range timing positioning method based on Vincenty formula, characterized in that: The positioning and timing are performed by integrating satellite and Loran stations. The formula is as follows: Among them, ρ1-ρ n is the n satellite pseudoranges measured by the receiver, n ≥ 4, ρ l1 -ρ lm is the pseudorange of m Loran stations measured by the receiver, m>0; (x1,y1,z1)-(x n ,y n ,z n ) represents the location of the Beidou satellite launch station, (x l1 ,y l1 ,z l1 )-(x lm ,y lm ,z lm ) represents the location of the Loran system transmitter; Δt represents the receiver clock error; x r ,y r ,z r represents the receiver coordinates; c is the speed of light; ε1-ε n , ε l1 -ε lm is other error; The corresponding number of Lorans is selected according to the number of available satellites detected, so that the sum of the number of satellites and the number of Lorans is at least equal to 4; and the equations of the above equation group are adjusted according to the number of satellites and the number of Lorans.

2. According to claim 1, a Loran pseudo-range timing positioning method based on Vincenty formula is characterized in that: The equations of the above set of equations are adjusted according to the number of satellites and Loran, including: If only three available satellites are detected, the three satellites are integrated with Loran for positioning and timing. The formula is as follows: If only two available satellites are detected, the two satellites are combined with Loran to perform positioning and timing. The formula is as follows: If no available satellites are detected, individual Loran station positioning and timing will be performed.

3. According to claim 2, a Loran pseudo-range timing positioning method based on Vincenty formula is characterized in that: The independent Loran station positioning and timing adopts the Loran pseudo-range timing and positioning method based on the Vincenty formula, including: Select a Loran station chain whose broadcast signal range includes the receiver location, and obtain the longitude and latitude coordinates of a main station and two secondary stations in the Loran station chain; Use a receiver to measure the arrival time of the signals transmitted by the three stations to the receiver; According to the latitude and longitude coordinates of the three stations, the arrival time and the initial coordinates of the receiver, the new receiver coordinates and time are calculated based on the Vincenty ranging formula; The coordinates of the new receiver are converted from the ellipsoid reference surface to the latitude and longitude of the actual earth surface to obtain the receiver coordinates and time.

4. According to claim 3, a Loran pseudo-range timing positioning method based on Vincenty formula is characterized in that: The method of calculating new coordinates and time based on the Vincenty ranging formula according to the latitude and longitude coordinates of the three stations, the arrival time and the initial coordinates of the receiver includes: Get the initial coordinates of the receiver; The latitude and longitude coordinates of the three stations are used to express the Vincenty ranging formula, and a differential equation system is constructed based on the Vincenty ranging formula; Perform first-order Taylor expansion of the differential equations at the initial coordinates to obtain a partial differential equation system; The iterative convergence threshold is set, and the partial differential equations are iteratively solved to obtain the receiver position and time.

5. According to claim 4, a Loran pseudo-range timing positioning method based on Vincenty formula is characterized in that: The differential equation group is specifically: Among them, ρ i represents the pseudorange measured by the receiver, represents the Vincenty distance formula, t i represents the receiver time difference, δ i represents other error terms, and c is the speed of light.

6. The Loran pseudo-range timing positioning method based on the Vincenty formula according to claim 5, characterized in that: The partial differential equations are specifically: Among them, D i is the true distance, is the product of the arrival time and the speed of light, ρ i0 is the pseudorange from the Loran station to the receiver, For ρ The partial derivatives of λ and t in ρ i0 The value of Δλ, Δt are The change of λ and t.

7. A computer system, characterized in that include: One or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors are enabled to implement the method of claim 1.

8. A computer-readable storage medium, characterized in that Computer executable instructions are stored, and when the instructions are executed, they are used to implement the method of claim 1.

9. A computer program product, characterized in that The invention comprises computer executable instructions, which are used to implement the method of claim 1 when being executed.

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