A GNSS terminal positioning data processing method

Abstract

The present invention relates to a GNSS terminal positioning data processing method, and belongs to the field of GNSS positioning data processing technology. The present invention starts from the consistency of SSR and OSR theories, and integrates the two correction numbers of SSR and OSR; when the OSR correction number is used for error correction, no secondary difference is made, and only a single difference is made between the user observation data and the OSR correction number, so that the error information contained in the OSR can be used for error correction while retaining its ability to form non-difference observation equations; in the equation formation stage, non-difference observation equations are formed for SSR and OSR at the same time, and no double-difference observation equations are contained, and they can be solved at the same time. The present invention can realize the fusion of the two correction numbers of SSR and OSR, and at the same time has the advantages of SSR's wide range of use and OSR's fast convergence speed, thereby improving positioning accuracy and reliability, and can adaptively and seamlessly switch between the two positioning modes of SSR and OSR.

Description

Technical Field

[0001] The present invention relates to a GNSS terminal positioning data processing method, and belongs to the technical field of GNSS positioning data processing. Background Art

[0002] In the GNSS positioning process, the known conditions are the position coordinates of the satellite (S1-S4) and the geometric distance from the receiver to the satellite measured by the ground receiver (R1), such as Figure 1 As shown, the unknowns are the receiver coordinates and the systematic time difference between the receiver and the satellites, the latter of which is referred to as the receiver clock error. The basic positioning principle is that when a receiver simultaneously observes four or more satellites, the unknowns are solved using equations derived from the known conditions based on the range intersection principle.

[0003] In GNSS positioning, the primary factors affecting positioning accuracy are various error terms. To improve positioning accuracy and mitigate the impact of these error terms, additional augmentation services independent of the GNSS system have emerged. Currently, there are two mainstream forms of GNSS augmentation services: SSR and OSR. SSR stands for State-Space Augmentation Service, and OSR stands for Observation-Space Augmentation Service. Both incorporate information about the various errors involved in GNSS positioning. By applying SSR or OSR corrections, the user end can eliminate the vast majority of GNSS positioning errors, achieving high-precision positioning. Wide-area augmentation systems and satellite-based augmentation systems fall under the State-Space Augmentation Service (SSR), and their corresponding terminal data processing technology is Precise Point Positioning (PPP). Differential systems, local-area augmentation systems, and ground-based augmentation systems fall under the Observation-Space Augmentation Service (OSR), and their corresponding terminal data processing technology is Real-Time Kinematic (RTK).

[0004] Figure 2 This is a schematic diagram of SSR and OSR correction numbers. There are two receivers R1 and R2 placed on the ground which are relatively close to each other (within 30 kilometers). R1 ​​is the base station for OSR services, and R2 is the positioning terminal that receives SSR and OSR services. The satellite in the sky is marked with S. SR1 and SR2 are the signal propagation paths from the satellite to the receiver, respectively. As can be seen from the figure, the sources of errors that affect the accuracy of GNSS positioning are mainly divided into two categories, namely, errors related to satellites and errors in the process of satellite signal propagation. Among them, the errors related to satellites are orbital errors, satellite clock errors, and signal deviations, and the errors related to the satellite signal propagation process are ionospheric delay and tropospheric delay. From Figure 2The difference between SSR and OSR corrections can also be seen. SSR is a direct correction, used directly by the user during positioning to eliminate various satellite-related and signal propagation-related errors. OSR is an indirect correction, essentially based on the reference station observations that contain various error information. Because the user station (R2) and the reference station (R1) are required to be close together, the aforementioned error terms that affect positioning accuracy are minimal between the user and reference stations and can be considered equal.

[0005] Because SSR broadcasts absolute error corrections to users, users can directly obtain globally unified positioning results after using SSR corrections, which we call absolute positioning. In contrast, OSR broadcasts base station observations containing error information to users. During use, users need to subtract the OSR observation data broadcast by the base station from the data observed by their own receiver. Therefore, the positioning result obtained by users using OSR corrections is the position of the user station relative to the base station, that is, the coordinate difference of R2 relative to R1, which is called relative positioning. OSR corrections also include the station coordinates of base station R1. By adding the coordinate difference of R2 relative to R1 to the coordinates of base station R1, the absolute coordinates of R2 can also be obtained.

[0006] Table 1 shows the main differences between SSR and OSR services. It's important to note that the atmospheric corrections in SSR, namely the ionospheric and tropospheric delays, are spatially localized and can only be considered stable over a small area. Therefore, SSR only provides atmospheric corrections within a relatively close range (250 km) of the service's base station. However, this does not affect the range of the SSR service or the positioning accuracy of the user terminal. When atmospheric corrections are present, the user-side algorithm can initialize quickly (1-3 minutes). Without atmospheric corrections, SSR terminal users will need approximately 15-30 minutes for the algorithm to complete initialization.

[0007] Table 1

[0008]

[0009]

[0010] As can be seen from Table 1, the advantages of the SSR service are wide coverage and no user limit. Simplex communication is conducive to ensuring the security of users' local data. The disadvantage is that without atmospheric information such as ionospheric delay and tropospheric delay, it requires a long initialization time (15-30 minutes). This time is called convergence time. The advantage of the OSR service is fast convergence speed, only 30 seconds. The disadvantage is large communication traffic, dependence on the network, and duplex communication has a user limit, which also threatens user data privacy.

[0011] The existing SSR and OSR terminal positioning data processing process is as follows: Figure 3 As shown, from Figure 3 As can be seen in the figure, the entire data processing process can be divided into three parts: error correction, equation formation, and equation solution. Due to the differences between SSR and OSR, the processing details of these three parts differ. In the error correction stage, the SSR correction method directly applies the corrections to the observation data to correct for errors such as satellite orbit, satellite clock error, and signal bias. The corrections result in error-free absolute observation data. The OSR correction method uses a differential between the user's observation data and the OSR corrections. This eliminates the common error between the two, resulting in relative observation values ​​for the user station relative to the OSR reference station. In the equation formation stage, SSR corrections produce absolute observation data, and the SSR method constructs undifferenced observation equations. However, OSR corrections produce relative observation data, and the OSR method constructs double-differenced observation equations. Finally, the equations are solved, and the SSR terminal obtains the user's absolute coordinates, while the OSR terminal obtains the user's relative coordinates relative to the OSR reference station.

[0012] Therefore, the current data processing methods for SSR and OSR are independent. The non-difference observation equation is constructed through SSR, and the double-difference observation equation is constructed through OSR. The respective equations are solved separately to obtain absolute coordinates and relative coordinates respectively. The two correction numbers are not truly integrated, and the advantages of the two correction numbers cannot be fully utilized, which in turn affects the final positioning accuracy and reliability. Summary of the Invention

[0013] The purpose of the present invention is to provide a GNSS terminal positioning data processing method to solve the problem of low positioning accuracy caused by poor fusion when two correction numbers are currently used for processing.

[0014] In order to solve the above technical problems, the present invention provides a GNSS terminal positioning data processing method, which includes the following steps:

[0015] 1) Obtain user station observation data, SSR corrections, and OSR corrections;

[0016] 2) Perform a difference process on the user station observation data and the OSR correction number to achieve error correction of the user station observation data; modify the satellite orbit error, satellite clock error, signal bias, ionospheric delay and tropospheric delay of the user station observation data based on the obtained SSR correction number;

[0017] 3) Establishing a first undifferenced observation equation based on the modified satellite orbit error, satellite clock error, signal bias, ionospheric delay, and tropospheric delay data; establishing a second undifferenced observation equation based on the first-order difference processing result of the obtained user station observation data and the OSR correction number;

[0018] 4) The first undifferenced observation equation and the second undifferenced observation equation are solved simultaneously to achieve positioning of the user station.

[0019] The present invention, starting from the consistency of SSR and OSR theories, integrates the two correction numbers of SSR and OSR; when using the OSR correction number for error correction, no secondary difference is performed, and only a single difference is performed between the user observation data and the OSR correction number. While using the error information contained in the OSR for error correction, the ability to form a non-difference observation equation is retained; in the equation formation stage, non-difference observation equations are formed for SSR and OSR at the same time, no double-difference observation equations are contained, and they can be solved simultaneously. The present invention can realize the integration of the two correction numbers of SSR and OSR, and has the advantages of both SSR, such as the wide range of use and the fast convergence speed of OSR, thereby improving positioning accuracy and reliability.

[0020] Furthermore, the second non-difference observation equation established in step 3) is:

[0021]

[0022]

[0023] Where the subscript i represents the user station receiver i, and the superscript k represents the satellite k. represents the pseudorange observation of satellite k obtained by user station receiver i; is the geometric distance from the user station receiver to the satellite; dx i ,dy i 、dz i are the coordinate parameters of the user station receiver respectively; is the coefficient of the linearized user station receiver coordinate parameter; c is the speed of light in vacuum; dt i and δt k are the receiver clock error and satellite clock error respectively; is the carrier phase integer ambiguity between user station receiver i and satellite k; dB i is the receiver carrier signal deviation; ε R is the pseudorange gross error; ε P is the carrier error; λ is the wavelength of the carrier signal; is the carrier observation quantity; It is the geometric distance from the user station receiver to the satellite after correction by the satellite orbit product.

[0024] Furthermore, the first non-difference observation equation established in step 3) is:

[0025]

[0026]

[0027] Where the subscript i represents the user station receiver i, and the superscript k represents the satellite k. represents the pseudorange observation of satellite k obtained by user station receiver i; is the geometric distance from the user station receiver to the satellite; dx i ,dy i 、dz i are the coordinate parameters of the user station receiver respectively; is the coefficient of the linearized user station receiver coordinate parameter; c is the speed of light in vacuum; dt i and δt k are the receiver clock error and satellite clock error respectively; is the carrier phase integer ambiguity between user station receiver i and satellite k; dB i is the receiver carrier signal deviation; ε R is the pseudorange gross error; ε P is the carrier error; λ is the wavelength of the carrier signal; is the carrier observation quantity; It is the geometric distance from the user station receiver to the satellite after correction by the satellite orbit product.

[0028] Furthermore, when the correction numbers obtained in step 1) are only SSR correction numbers, the SSR correction numbers are used to correct the user station observation data to establish a first non-difference observation equation, and the first non-difference observation equation is solved to obtain the position information of the user station.

[0029] Furthermore, when the correction numbers obtained in step 1) are only OSR correction numbers, an inter-station difference processing is performed using the OSR correction numbers and the user station observation data to establish a second non-difference observation equation, and the second non-difference observation equation is solved to obtain the position information of the user station.

[0030] The present invention can unify the two correction number processing algorithms by fusing the two correction numbers, and can achieve seamless switching between the two correction number processing methods. When there are only SSR or only OSR correction numbers, the terminal can also work normally, further improving the robustness of the algorithm.

[0031] Furthermore, the establishment process of the second undifferenced observation equation is:

[0032] Determine the linearized user station GNSS observation equation based on the user station observation data, including the user station pseudorange observation equation and the user station carrier observation equation;

[0033] The observation equation of the reference station is established based on the observation value of the reference station receiver on the same satellite at the same epoch within the set range of the user station, including the reference station pseudorange observation equation and the reference station carrier observation equation;

[0034] The pseudorange observation equation of the user station is subtracted from the pseudorange observation equation of the reference station, and the carrier observation equation of the user station is subtracted from the carrier observation equation of the reference station. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the basic principles of GNSS positioning;

[0036] Figure 2 This is a schematic diagram of the principles of the two correction numbers SSR and OSR;

[0037] Figure 3 This is a flow chart of an existing GNSS terminal positioning data processing method;

[0038] Figure 4 It is a flow chart of the GNSS terminal positioning data processing method of the present invention. DETAILED DESCRIPTION

[0039] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0040] The present invention realizes error correction of user station observation data by performing a difference processing on the user station observation data and the OSR correction number; and modifies the satellite orbit error, satellite clock error, signal deviation, ionospheric delay and tropospheric delay of the user station observation data according to the obtained SSR correction number; then, a first non-differenced observation equation is formed based on the modified satellite orbit error, satellite clock error, signal deviation, ionospheric delay and tropospheric delay data; a second non-differenced observation equation is formed based on the result of the difference processing of the user station observation data and the OSR correction number; finally, the first non-differenced observation equation and the second non-differenced observation equation are solved simultaneously to realize the positioning of the user station. The specific implementation process of this method is as follows: Figure 4 As shown, the process is described in detail below.

[0041] The present invention is different from the existing GNSS terminal positioning data processing method (such as Figure 3 Compared with the previous one, there are two main improvements: first, in the error correction stage using OSR corrections, instead of making a secondary difference, only a single difference is made between the user observation data and the OSR corrections. The purpose of this approach is to retain its ability to construct non-differenced observation equations while using the error information contained in OSR for error correction; second, in the equation construction stage, non-differenced observation equations are constructed for SSR and OSR at the same time and solved at the same time to achieve an organic fusion of the two corrections.

[0042] 1. Obtain user station observation data, SSR corrections, and OSR corrections.

[0043] This embodiment obtains user station observation data through the user station receiver. The user station observation data here mainly includes pseudorange data and carrier data. The SSR broadcasts absolute error correction numbers to the user station, and the OSR broadcasts reference station observation values ​​containing error information to the user.

[0044] 2. Use the acquired user station observation data, SSR corrections and OSR corrections to perform error correction.

[0045] In the error correction process, SSR corrections are directly applied to the satellite orbit error, satellite clock error, signal bias, ionospheric delay, and tropospheric delay of the observation data. The corrections result in absolute observation data free of errors. OSR corrections are used to differentiate the user's observation data from the OSR corrections. This eliminates the common error between the two, resulting in relative observation values ​​of the user station relative to the OSR reference station, resulting in error-free relative observation data.

[0046] 3. Based on the error correction results, the first non-difference observation equation and the second non-difference observation equation are respectively established.

[0047] The linearized user-side GNSS observation equation is:

[0048]

[0049]

[0050] Formula (1) is the pseudorange observation equation at the user end, where the subscript i represents the user station receiver i and the superscript k represents the satellite k; represents the pseudorange observation of satellite k obtained by user station receiver i; is the geometric distance from the receiver to the satellite; dx i ,dy i 、dz i are the receiver coordinate parameters, is the coefficient of the linearized receiver coordinate parameter, which can be calculated from the satellite coordinates and the initial receiver coordinates and can be regarded as a constant; c is the speed of light in vacuum; dt i and δt k are the receiver clock error and satellite clock error respectively; δ ion is the ionospheric delay error; δ trop is the tropospheric delay error; δb k is the pseudorange signal deviation of satellite k; ε R is the pseudorange gross error.

[0051] Formula (2) is the user station carrier observation equation, λ is the carrier signal wavelength, is the carrier observation quantity, is the carrier phase integer ambiguity between receiver i and satellite k, δB k is the satellite carrier signal deviation, dB i is the receiver carrier signal deviation, ε P is the carrier coarse error. Other than that, the meanings of the other items are the same as those in formula (1).

[0052] SSR contains satellite orbit products, satellite clock products, satellite signal bias products, ionospheric delay products, and tropospheric delay products, among which satellite orbit products are used to correct Satellite clock error products are used to eliminate δt k , the satellite signal bias product is used to eliminate δb k and δB k , the ionospheric delay product is used to eliminate δ ion , the tropospheric delay product is used to eliminate δ trop .

[0053] The observation equation of the user station after correction by the SSR product is the first undifferenced observation equation, as shown in equations (3) and (4):

[0054]

[0055]

[0056] In formula (3) and (4), is the geometric distance from the receiver to the satellite after correction by the satellite orbit product. The quantities on the left side of the equal sign are known and can be calculated. The quantities on the right side of the equal sign are unknown parameters and their linearized coefficients. From this point on, we can directly formulate non-difference equations to solve for the unknown parameters.

[0057] OSR is essentially the observation value of the base station receiver near the user on the same satellite at the same epoch. Equations (5) and (6) are the linearized observation equations of base station receiver j, where the subscript j represents base station receiver j, and the rest of the meanings are the same as those of equations (1) and (2). Since the OSR correction number contains the exact coordinates of receiver j, its observation equation does not contain dx j ,dy j 、dz j These three parameters are unknown.

[0058]

[0059]

[0060] The OSR corrections are used by difference, specifically by subtracting (5) from (1) and (6) from (2). This method of differencing the observation equations for the same satellite between different receivers is called inter-station single difference.

[0061] The user-side observation equations after single difference between OSR product stations are shown in Equations (7) and (8):

[0062]

[0063]

[0064] After the inter-station single difference, the error term with subscript k and only related to the satellite is eliminated. At the same time, since the user receiver is close to the base station receiver, the ionospheric delay and tropospheric delay of the two receivers can be considered to be the same, so δ ion and δ trop It is also eliminated after the inter-station difference.

[0065] Equations (7) and (8) are the second undifference observation equations.

[0066] 4. The first undifferenced observation equation and the second undifferenced observation equation are solved simultaneously to achieve positioning of the user station.

[0067] As can be seen from the above equations, the first undifferenced observation equation (Equation (3) and Equation (4)) and the second undifferenced observation equation (Equation (7) and Equation (8)) have the same form. Therefore, they can be constructed together to form the undifferenced equations and then jointly solve for the unknown parameters, i.e., the coordinates of user station i.

[0068] Through the above process, the present invention integrates the SSR correction number and the OSR correction number, and can simultaneously possess the advantages of the SSR wide range of use and the OSR fast convergence speed, and the non-difference observation equations established based on these two correction numbers are all non-difference observation equations, which can be solved at the same time. In addition, the present invention can not only process both SSR and OSR correction numbers at the same time, but also when there are only SSR or only OSR correction numbers, the terminal can also work normally, so that the robustness of the terminal is improved. The above method can also be set as a computer program on the GNSS terminal. In addition, it can also adaptively and seamlessly switch between the two positioning modes of SSR and OSR to further improve positioning accuracy.

Claims

1. A GNSS terminal positioning data processing method, characterized in that: The method comprises the following steps: 1) Obtain user station observation data, SSR corrections, and OSR corrections; 2) Perform a difference process on the user station observation data and the OSR correction number to achieve error correction of the user station observation data; modify the satellite orbit error, satellite clock error, signal bias, ionospheric delay and tropospheric delay of the user station observation data based on the obtained SSR correction number; 3) establishing a first undifferenced observation equation based on the modified satellite orbit error, satellite clock error, signal bias, ionospheric delay, and tropospheric delay data; determining a user station pseudorange observation equation and a user station carrier observation equation based on the user station observation data, establishing a reference station pseudorange observation equation and a reference station carrier observation equation based on observations of the same satellite by a reference station receiver within a set range of the user station at the same epoch, subtracting the reference station pseudorange observation equation from the user station pseudorange observation equation, and subtracting the reference station carrier observation equation from the user station carrier observation equation to establish a second undifferenced observation equation; 4) simultaneously solving the first undifferenced observation equation and the second undifferenced observation equation to achieve positioning of the user station; The first undifferenced observation equation is: The second undifferenced observation equation is: Where the subscript i represents the user station receiver i, and the superscript k represents the satellite k. represents the pseudorange observation of satellite k obtained by user station receiver i; is the geometric distance from the user station receiver to the satellite; dx i ,dy i 、dz i are the coordinate parameters of the user station receiver respectively; is the coefficient of the linearized user station receiver coordinate parameter; c is the speed of light in vacuum; dt i and δt k are the receiver clock error and satellite clock error respectively; is the carrier phase integer ambiguity between user station receiver i and satellite k; dB i is the receiver carrier signal deviation; ε R is the pseudorange gross error; ε P is the carrier error; λ is the wavelength of the carrier signal; is the carrier observation quantity; It is the geometric distance from the user station receiver to the satellite after correction by the satellite orbit product.

2. The GNSS terminal positioning data processing method according to claim 1, characterized in that: When the correction numbers obtained in step 1) are only SSR correction numbers, the SSR correction numbers are used to correct the user station observation data to establish a first non-difference observation equation, and the first non-difference observation equation is solved to obtain the position information of the user station.

3. The GNSS terminal positioning data processing method according to claim 1, characterized in that: When the only corrections obtained in step 1) are OSR corrections, an inter-station difference process is performed using the OSR corrections and the user station observation data to establish a second undifferenced observation equation. The second undifferenced observation equation is solved to obtain the position information of the user station.

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