Positioning satellite selection method of Beidou satellite navigation system

Abstract

The invention relates to the technical field of satellite navigation, in particular to a positioning satellite selection method of a Beidou satellite navigation system. The method comprises the following steps: receiving a Beidou satellite navigation signal, carrying out baseband signal processing to capture and track a satellite signal, and calculating a signal carrier intensity weight coefficient of each satellite according to the carrier intensity of the satellite signal, a new azimuth and intensity G matrix containing Beidou satellite space azimuth information and satellite signal energy information is constructed, the new azimuth and intensity G matrix is combined with a navigation message and a ranging code to carry out positioning calculation so as to determine the position of a receiver, and the satellite carrier signal intensity is considered to optimize the satellite selection process. According to the technical scheme, the positioning precision of the Beidou satellite navigation system in a complex environment can be remarkably improved, and rapid and continuous high-precision positioning service is provided for customers.

Description

Technical Field

[0001] The present invention relates to the field of satellite navigation technology, and in particular to a positioning and star selection method for a Beidou satellite navigation system. Background Art

[0002] As one of the four major satellite navigation systems in the world, the accuracy and reliability of the Beidou satellite navigation system's positioning services are crucial for various application scenarios. However, in actual applications, especially in complex environments such as urban canyons, forests, and tall buildings, satellite signals may be affected by obstruction, reflection, and refraction, resulting in a decrease in signal quality, thereby affecting positioning accuracy.

[0003] The existing Beidou satellite navigation system positioning method mainly relies on the spatial position information of the satellite, captures and tracks the satellite signal through the receiver, and then uses the satellite's ephemeris data and navigation message to perform positioning and solution. This method works well in an open environment, but in a complex environment, due to the instability of the satellite signal and the influence of the multipath effect, the positioning accuracy often cannot meet the requirements. The present invention aims to provide a Beidou satellite navigation system positioning and star selection method, which introduces the satellite carrier signal strength as a weight to optimize the star selection process, thereby improving the positioning accuracy. Summary of the invention

[0004] The purpose of the present invention is to provide a Beidou satellite navigation system positioning and star selection method to solve the problem of insufficient accuracy of traditional positioning and star selection methods in complex environments, and to improve the accuracy of positioning solutions by incorporating satellite carrier signal strength into star selection considerations.

[0005] A Beidou satellite navigation system positioning and star selection method comprises the following steps:

[0006] S1: Receive signals from the Beidou satellite navigation system, including navigation messages and ranging codes;

[0007] S2: Select multiple satellites based on the information provided by the navigation message, and calculate the pseudo-range between the receiver and the selected satellites through the ranging code;

[0008] S3: Calculate the angle of the satellite relative to the geocentric coordinate axis and construct an orientation G matrix;

[0009] S4: measure the satellite carrier signal strength, and construct a diagonal matrix X using the satellite carrier signal strength as a diagonal element;

[0010] S5: multiply the azimuth G matrix by the diagonal matrix X satellite carrier signal strength as the weight, modify the azimuth G matrix, and obtain a new azimuth and strength G matrix G′;

[0011] S6: Use the G′ matrix to perform receiver positioning solution.

[0012] Preferably, in S4, the new orientation and intensity G matrix G′ is:

[0013]

[0014] Among them, (A1, A2, ..., A N denote the carrier signal strength of satellites A, B, ..., N, respectively, cos(α1), cos(α2), ..., cos(α N ); cos(β1), cos(β2),…, cos(β N ); cos(γ1), cos(γ2),…, cos(γ N ) represent the cosine values ​​of the angles between the A, B, ..., N satellites and the geocentric coordinate axes x, y, and z, respectively.

[0015] Preferably, the angle of the satellite relative to the geocentric coordinate axis in step S3 is calculated by measuring the elevation angle φ and the azimuth angle ψ of the satellite constellation:

[0016]

[0017] Preferably, the navigation message described in S1 is divided into two types, D1 and D2. The content of the D1 navigation message is basic information such as the satellite's health level, satellite ephemeris, clock correction, and counting. The message rate is 50bps, and it takes 12 minutes to broadcast the entire D1 navigation message. The content of the D2 navigation message is basic navigation information and enhanced service information, namely, user differential distance error index, grid point ionospheric vertical delay parameters, Beidou system integrity and other information. The message rate is 500bps, and it takes 6 minutes to broadcast the entire D2 navigation message.

[0018] Preferably, four satellites are selected each time in step S2 to calculate the G matrix; in step S2, a pseudorange is obtained by measuring the ranging code by a Beidou positioning system receiver, and the pseudorange is the distance from the Beidou satellite to the user receiver, which is as follows:

[0019] S201: The satellite sends a ranging code and records the sending timestamp T 发射 ;

[0020] S202: When the receiver receives the ranging code, it records the received timestamp T 接收 ;

[0021] S203: Calculate the time difference ΔT between the time when the receiver receives the ranging code and the time when the satellite sends the ranging code: ΔT = T 接收 -T 发射

[0022] S204: Calculate the pseudorange P using the chip rate and time delay of the ranging code s :

[0023]

[0024] Preferably, in S4, the measurement of the satellite carrier signal strength is achieved through a CDMA spread spectrum method.

[0025] Preferably, step S6 includes selecting a suitable G′ matrix to complete positioning, and the steps are as follows:

[0026] S601: Collect information of all visible satellites;

[0027] S602: Calculate the geometric precision factor, i.e., DOP value, of the G′ matrix formed by different satellite combinations;

[0028] S603: Evaluate the G' matrices of different satellite combinations and select the satellite combination with the lowest DOP value.

[0029] Preferably, in step S6, the G′ matrix is ​​used to complete the positioning solution, as follows:

[0030] S61: using the G' matrix and pseudorange to establish an observation equation, the observation equation is expressed as: G'x = P, where x is the unknown receiver position vector and P is the pseudorange vector;

[0031] S62: Use the least squares method to solve the observation equation and obtain the receiver position vector x, which is:

[0032] x=(G′ T G′) -1 G′ T P

[0033] where G′ T is the transpose of the G' matrix, (G' T G′) -1 is G′ T The inverse matrix of the G′ matrix;

[0034] S63: Use the obtained position vector as the estimated position of the receiver.

[0035] Preferably, in step S3, the satellite constellation elevation angle φ and azimuth angle ψ are calculated using satellite ephemeris provided by the satellite navigation message.

[0036] A receiver using any of the above-mentioned Beidou satellite navigation system positioning and star selection methods, characterized in that the receiver comprises:

[0037] A signal receiving unit, used to receive signals from the Beidou satellite navigation system;

[0038] The signal processing unit is used to perform baseband processing on the signal, including rapid signal acquisition and tracking, and positioning and solving of received information;

[0039] The carrier signal strength measurement unit is used to measure the carrier signal strength of the visible satellites and obtain the signal strength value of each satellite;

[0040] The azimuth and intensity G matrix construction unit is used to construct the azimuth and intensity G matrix, and select satellites for positioning solution according to the constructed azimuth and intensity matrix.

[0041] It can be seen from the above technical solutions that 1. the present invention combines signal strength with positioning accuracy, takes into account the strength of satellite carrier signals, and adds them as weights to the azimuth G matrix, thereby improving the accuracy of positioning solution. In harsh environments, the strength of the signal directly affects the accuracy of positioning. Through this combination, a relatively reliable positioning result can be obtained even in poor signal conditions;

[0042] 2. The present invention uses satellite signal strength as a factor in satellite selection, thereby improving the adaptability in complex environments with obstructions such as urban canyons and forests, and improving the reliability and robustness of positioning;

[0043] 3. The present invention calculates the geometric precision factor of the matrix formed by different satellite combinations, selects the satellite combination with the lowest DOP value, optimizes the satellite selection process, and further improves the positioning accuracy;

[0044] 4. The present invention records the timestamp of the ranging code sent by the satellite and the timestamp received by the receiver, calculates the time difference, and uses the chip rate and time delay of the ranging code to calculate the pseudorange, thereby providing accurate distance measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 It is a flow chart of a Beidou satellite navigation system positioning and star selection method of the present invention;

[0047] Figure 2 is a diagram showing the relationship between the satellite angle to the earth and its elevation angle φ and azimuth angle ψ of the present invention; DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] An embodiment of the present invention provides a method for positioning and selecting stars for a Beidou satellite navigation system, which is described in detail below.

[0050] Example 1

[0051] See also Figure 1 , a Beidou satellite navigation system positioning and star selection method, comprising the following steps:

[0052] S1: Receive signals from the Beidou satellite navigation system; the signal receiving unit of the receiver starts working to receive signals from Beidou satellites, which include navigation messages and ranging codes;

[0053] Navigation messages are divided into two types: D1 and D2. D1 contains basic information about the satellite, such as health level, ephemeris, clock correction, etc., with a rate of 50bps and a complete broadcast taking 12 minutes. D2 contains basic navigation information and enhanced service information, with a rate of 500bps and a complete broadcast taking 6 minutes.

[0054] The ranging code is also called pseudo-random code, or pseudo-code for short. The pseudo-code is equivalent to the satellite identifier. Different satellites have different pseudo-codes, which means that the pseudo-code is unique. The pseudo-code has two functions in satellite signals: First, the strong autocorrelation characteristics of the pseudo-code are used to calculate the number of the satellite to which the information received by the receiver belongs. Because the pseudo-code is unique, only when the local pseudo-code and the pseudo-code in the satellite signal are the same, a maximum correlation value will be obtained. By traversing and finding the corresponding satellite using this maximum correlation value, the satellite number can be known. This strong autocorrelation is one of the foundations of satellite navigation system signal processing; second, the pseudo-code is used to measure the transmission distance between the satellite and the signal receiver;

[0055] S2: Select satellites and calculate pseudoranges; the signal processing unit of the receiver selects multiple satellites based on the information provided by the navigation message, and calculates the pseudoranges between the receiver and the selected satellites through ranging codes, as follows:

[0056] S201: The satellite sends a ranging code and records the sending timestamp T 发射 ;

[0057] S202: When the receiver receives the ranging code, it records the received timestamp T 接收 ;

[0058] S203: Calculate the time difference ΔT between the time when the receiver receives the ranging code and the time when the satellite sends the ranging code: ΔT = T 接收 -T 发射

[0059] S204: Calculate the pseudorange P using the chip rate and time delay of the ranging code s :

[0060]

[0061] S3: Construct the azimuth G matrix, calculate the angle between the satellite and the geocentric coordinate axis, and measure the elevation angle of the satellite constellation. and azimuth angle ψ to calculate; construct an azimuth G matrix, in which each row element is the direction cosine value of the angle between each satellite observable in space and the geocentric coordinate axis x, y, z;

[0062] S4: measuring the satellite carrier signal strength. The receiver carrier signal strength measurement unit measures the carrier signal strength of the visible satellite, obtains the signal strength value of each satellite, and constructs a diagonal matrix X using the carrier signal strength of each satellite as a diagonal element.

[0063] S5: modify the azimuth G matrix, multiply the azimuth G matrix by the diagonal matrix X on the left, use the satellite carrier signal strength as the weight, modify the azimuth G matrix, and obtain a new azimuth and strength G matrix G′;

[0064] S6: Use the matrix to solve the receiver positioning; collect information of all visible satellites; calculate the geometric precision factor (DOP) of the matrix formed by different satellite combinations; evaluate the G' matrix of different satellite combinations and select the satellite combination with the lowest DOP value; use the G' matrix and pseudorange to establish the observation equation, expressed as: G'x = P, where x is the unknown receiver position vector and P is the pseudorange vector; use the least squares method to solve the observation equation and obtain the receiver position vector x, specifically:

[0065] x=(G′ T G′) -1 G′ T P

[0066] where G′ T is the transpose of the G' matrix, (G' T G′) -1 is G′ T The inverse matrix of the G′ matrix; the obtained position vector is used as the estimated position of the receiver.

[0067] Embodiment 2

[0068] See also Figure 2, the satellite ephemeris provided by the satellite navigation message is used to calculate the satellite constellation elevation angle φ and azimuth angle ψ, and the angle of the satellite relative to the geocentric coordinate axis is calculated:

[0069]

[0070] The new position and intensity matrix G′ is calculated using the angle between the satellite and the geocentric coordinate axis:

[0071]

[0072] Among them, A1, A2, ..., A N denote the carrier signal strength of satellites A, B, ..., N, respectively, cos(α1), cos(α2), ..., cos(α N ); cos(β1), cos(β2),…, cos(β N ); cos(γ1), cos(γ2),…, cos(γ N ) represent the cosine values ​​of the angles between the A, B, ..., N satellites and the geocentric coordinate axes x, y, and z, respectively.

[0073] Embodiment 3

[0074] A receiver using any of the above-mentioned Beidou satellite navigation system positioning and star selection methods, the receiver comprising:

[0075] A signal receiving unit, used to receive signals from the Beidou satellite navigation system;

[0076] The signal processing unit is used to perform baseband processing on the signal, including rapid signal acquisition and tracking, and positioning and solving of received information;

[0077] The carrier signal strength measurement unit is used to measure the carrier signal strength of the visible satellites and obtain the signal strength value of each satellite;

[0078] The azimuth and intensity G matrix construction unit is used to construct the azimuth and intensity G matrix, and select satellites for positioning solution according to the constructed azimuth and intensity matrix.

Claims

1. A method for positioning and selecting stars for a Beidou satellite navigation system, characterized in that: The following steps are involved: S1: Receive signals from the Beidou satellite navigation system, including navigation messages and ranging codes; S2: Select multiple satellites based on the information provided by the navigation message, and calculate the pseudo-range between the receiver and the selected satellites through the ranging code; S3: Calculate the angle of the satellite relative to the geocentric coordinate axis and construct an orientation G matrix; S4: measure the satellite carrier signal strength, and construct a diagonal matrix X using the satellite carrier signal strength as a diagonal element; S5: multiply the azimuth G matrix by the diagonal matrix X satellite carrier signal strength as the weight, modify the azimuth G matrix, and obtain a new azimuth and strength G matrix G′; S6: Use the G′ matrix to perform receiver positioning solution.

2. A Beidou satellite navigation system positioning and star selection method according to claim 1, characterized in that: In S4, the new orientation and intensity G matrix G′ is: Among them, A1, A2, ..., A N denote the carrier signal strength of satellites A, B, ..., N, respectively, cos(α1), cos(α2), ..., cos(α N ); cos(β1), cos(β2),…, cos(β N ); cos(γ1), cos(γ2),…, cos(γ N ) represent the cosine values ​​of the angles between the A, B, ..., N satellites and the geocentric coordinate axes x, y, and z, respectively.

3. A Beidou satellite navigation system positioning and star selection method according to claim 1, characterized in that: The angle between the satellite and the geocentric coordinate axis in step S3 is calculated by measuring the elevation angle φ and the azimuth angle ψ of the satellite constellation:

4. The Beidou satellite navigation system positioning and star selection method according to claim 1, characterized in that: The navigation message described in S1 is divided into two types: D1 and D2. The content of D1 navigation message is basic information of satellite health level, satellite ephemeris, clock correction and counting. The message rate is 50bps. It takes 12 minutes to broadcast the entire D1 navigation message. The content of the D2 navigation message is basic navigation information and enhanced service information, namely, user differential range error index, grid point ionospheric vertical delay parameters, Beidou system integrity and other information. The message rate is 500bps, and it takes 6 minutes to broadcast the entire D2 navigation message.

5. The method for positioning and selecting stars for the Beidou satellite navigation system according to claim 1, characterized in that: In step S2, four satellites are selected each time to calculate the G matrix; in step S2, the pseudorange is obtained by measuring the ranging code by the Beidou positioning system receiver. The pseudorange is the distance from the Beidou satellite to the user receiver, as follows: S201: The satellite sends a ranging code and records the sending timestamp T 发射 ; S202: When the receiver receives the ranging code, it records the received timestamp T 接收 ; S203: Calculate the time difference ΔT between the time when the receiver receives the ranging code and the time when the satellite sends the ranging code: ΔT = T 接收 -T 发射 S204: Calculate the pseudorange P using the chip rate and time delay of the ranging code s :

6. The Beidou satellite navigation system positioning and star selection method according to claim 1, characterized in that: In S4, the measurement of the satellite carrier signal strength is achieved through the CDMA spread spectrum method.

7. The method for positioning and selecting stars for the Beidou satellite navigation system according to claim 1, characterized in that: Step S6 includes selecting a suitable G′ matrix to complete positioning, and the steps are as follows: S601: Collect information of all visible satellites; S602: Calculate the geometric precision factor, i.e., DOP value, of the G′ matrix formed by different satellite combinations; S603: Evaluate the G' matrices of different satellite combinations and select the satellite combination with the lowest DOP value.

8. A Beidou satellite navigation system positioning and star selection method according to claim 1, characterized in that: In step S6, the G′ matrix is ​​used to complete the positioning solution, as follows: S61: using the G' matrix and pseudorange to establish an observation equation, the observation equation is expressed as: G'x = P, where x is the unknown receiver position vector and P is the pseudorange vector; S62: Use the least squares method to solve the observation equation and obtain the receiver position vector x, which is: x=(G′ T G′) -1 G′ T P where G′ T is the transpose of the G' matrix, (G' T G′) -1 is G′ T The inverse matrix of the G′ matrix; S63: Use the obtained position vector as the estimated position of the receiver.

9. The Beidou satellite navigation system positioning and star selection method according to claim 1 or 3, characterized in that: In step S3, the satellite constellation elevation angle φ and azimuth angle ψ are calculated using the satellite ephemeris provided by the satellite navigation message.

10. A receiver using a Beidou satellite navigation system positioning and star selection method as claimed in any one of claims 1 to 8, characterized in that: The receiver includes: A signal receiving unit, used to receive signals from the Beidou satellite navigation system; The signal processing unit is used to perform baseband processing on the signal, including rapid signal acquisition and tracking, and positioning and solving of received information; The carrier signal strength measurement unit is used to measure the carrier signal strength of the visible satellites and obtain the signal strength value of each satellite; The azimuth and intensity G matrix construction unit is used to construct the azimuth and intensity G matrix, and select satellites for positioning solution according to the constructed azimuth and intensity matrix.

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