PPP positioning method and system, computer equipment and medium

Abstract

The invention belongs to the technical field of PPP positioning, and discloses a PPP positioning method and system, computer equipment and a medium. According to the method, the PPP-B2b service satellite clock error constant deviation is considered, the PPP mathematical model based on the PPP-B2b service is constructed, the B2b satellite clock error correction constant deviation characteristics are fully considered, the satellite clock error constant deviation is subjected to parameter estimation, a piecewise constant estimation strategy is adopted, the constant deviation is separated, the influence of the satellite clock error constant deviation on other to-be-estimated parameters of the PPP is weakened, and the PPP-B2b service satellite clock error correction constant deviation is obtained. The PPP convergence time can be effectively shortened, and the PPP positioning performance is improved. In addition, the method is simple, reliable and convenient to implement in real time. Compared with a conventional B2b signal satellite clock error correction constant deviation processing method, the strategy for conducting piecewise constant estimation on the satellite clock error constant deviation does not need to provide extra deviation products externally, the algorithm is simple and easy to achieve, and real-time application is convenient.

Description

Technical Field

[0001] The present invention belongs to the technical field of PPP positioning, and particularly relates to a PPP positioning method, system, computer device, and medium. The PPP positioning method takes into account the satellite clock bias constant deviation of the PPP-B2b service. Background Art

[0002] Precise Point Positioning (PPP) technology can obtain high-precision position, atmospheric delay, clock bias, etc. information globally, and has been widely used in fields such as precise time service, water vapor monitoring, earthquake monitoring, and precise orbit determination. PPP uses the GNSS observations of a single receiver and precise ephemeris for data processing, and the positioning accuracy can reach the decimeter level or even the centimeter level. The International GNSS Service organization provides precise satellite orbits and clock products to global users via the Internet to meet the needs of real-time precise positioning. However, if the network communication service is interrupted, users will not be able to receive corrections, thus affecting the PPP performance.

[0003] Since 2020, the BeiDou Navigation Satellite System version 3 (BDS-3) has broadcast precise orbit, clock bias and other correction information to the Asia-Pacific and surrounding regions through the downlink signal of the geostationary satellite B2b, providing regional PPP services (referred to as PPP-B2b). PPP-B2b only provides regional services. In the satellite clock bias estimation, pseudorange observations are required to provide a relative reference at the beginning of a new satellite arc segment, so there are differences in the clock bias constants included in different arc segments in the satellite clock bias estimation results. This bias will be absorbed by the pseudorange residuals during the PPP solution, thus affecting the PPP convergence speed.

[0004] Currently, some studies estimate and correct the satellite clock bias constant deviation and signal distortion deviation existing in the PPP-B2b clock products together to the observations, which greatly improves the PPP convergence speed. However, due to the different satellite clock bias constants in different arc segments, the extracted clock bias constants are not applicable to all arc segments, so it is particularly difficult to apply this method in real-time PPP. In addition, some studies use multiple reference stations to jointly estimate the constant deviation and broadcast the constant deviation through the network for user real-time positioning. Nevertheless, the application of this method is significantly limited in areas with insufficient network coverage in remote regions.

[0005] Therefore, how to effectively reduce the impact of the clock bias constant deviation on real-time PPP positioning is of great value for promoting the popularization of PPP-B2b services and improving precise navigation, positioning and timing services. Summary of the Invention

[0006] The object of the present invention is to propose a PPP positioning method that takes into account the satellite clock offset constant deviation of the PPP-B2b service. By constructing a PPP mathematical model based on the PPP-B2b service, fully considering the characteristics of the B2b satellite clock offset correction constant deviation, parameter estimating the clock offset constant deviation and adopting a piecewise constant estimation strategy to separate the constant deviation, so as to weaken the influence of the clock offset constant deviation existing in the PPP-B2b clock offset correction on PPP positioning, shorten the PPP convergence time, and improve the PPP positioning performance.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A PPP positioning method, comprising the following steps: Step 1. Obtain satellite phase observations, pseudorange observation data, broadcast ephemeris, various corrections broadcast by the B2b signal, and antenna phase center products at the station. Step 2. Use the broadcast ephemeris to perform data quality inspection and gross error rejection on the observations, delete satellite data without satellite ephemeris or with incomplete observations, and delete satellites without B2b signal corrections or with abnormal B2b signal corrections according to the validity period of the B2b signal correction information and the user ranging accuracy index; at the same time, judge whether the satellite clock offset corrections of the satellites with normal B2b signal corrections in the current epoch are continuous and mark them. Step 3. Error correction; Step 4. Consider the satellite clock offset constant deviation in the B2b signal clock offset correction , and establish a PPP mathematical model considering the satellite constant deviation, including a PPP observation equation and a stochastic model; Step 5. According to the satellite ephemeris continuity mark in Step 2, adopt a piecewise constant estimation strategy; Step 6. Perform Kalman filter estimation according to the mathematical model established in Step 4 and the parameter estimation strategy determined in Step 5 to obtain the three-dimensional position of the receiver, , tropospheric zenith wet delay, ambiguity, and receiver clock offset parameters.

[0008] In addition, on the basis of the above PPP positioning method that takes into account the satellite clock offset constant deviation of the PPP-B2b service, the present invention also proposes a corresponding PPP positioning system, which adopts the following technical solutions: A PPP positioning system, comprising the following modules: A data acquisition module, used to obtain satellite phase observations, pseudorange observation data, broadcast ephemeris, various corrections broadcast by the B2b signal, and antenna phase center products at the station; A preprocessing module for performing data quality inspection and gross error rejection on the observations using broadcast ephemeris, deleting satellite data without satellite ephemeris or with incomplete observations, and deleting satellites without B2b signal correction numbers or with abnormal correction numbers according to the validity period of the B2b signal correction information and the user ranging accuracy index; meanwhile, determining whether the satellite clock corrections of the satellites with normal B2b signal correction numbers in the current epoch are continuous and making marks. An error correction module for performing error correction. A PPP mathematical model establishment module for considering the satellite clock constant deviation in the B2b signal clock correction and establishing a PPP mathematical model considering satellite constant deviation, including PPP observation equations and stochastic models. A parameter estimation strategy determination module for, according to the continuous marking of the satellite ephemeris, adopting a piecewise constant estimation strategy. And a parameter estimation module for performing Kalman filter estimation according to the established mathematical model and the determined parameter estimation strategy to obtain the three-dimensional position of the receiver, , tropospheric zenith wet delay, ambiguity, and receiver clock parameters.

[0009] In addition, based on the above PPP positioning method, the present invention also proposes a computer device, which includes a memory and one or more processors. Executable code is stored in the memory, and when the processor executes the executable code, it is used to implement the steps of the above-mentioned PPP positioning method.

[0010] In addition, based on the above PPP positioning method, the present invention also proposes a computer-readable storage medium, on which a program is stored. When the program is executed by a processor, it is used to implement the steps of the above-mentioned PPP positioning method.

[0011] The present invention has the following advantages: As described above, the present invention describes a PPP positioning method considering the satellite clock constant deviation of PPP-B2b service, which effectively weakens the error influence and improves the positioning performance. Specifically, the present invention constructs a PPP mathematical model based on PPP-B2b service, fully considering the characteristics of the B2b satellite clock correction constant deviation, performing parameter estimation on the clock constant deviation and adopting a piecewise constant estimation strategy to separate the constant deviation to weaken its influence on other PPP parameters to be estimated, which can effectively shorten the PPP convergence time and improve the PPP positioning performance. In addition, the method of the present invention is simple and reliable and convenient for real-time implementation. Compared with the conventional method for processing the B2b signal satellite clock correction constant deviation, the strategy of performing piecewise constant estimation on the clock constant deviation proposed by the present invention does not require external provision of additional deviation products, the algorithm is simple and easy to implement, and it is convenient for real-time application. Description of the Drawings

[0012] Figure 1 This is a flowchart of the PPP positioning method considering the satellite clock bias constant deviation of the PPP - B2b service in the embodiments of the present invention. Detailed Implementation Modes

[0013] The present invention will be further described in detail below with reference to the drawings and specific implementation modes: Embodiment 1 As Figure 1 shown, in order to improve the performance of the PPP - B2b service, Embodiment 1 of the present invention describes a PPP positioning method considering the satellite clock bias constant deviation of the PPP - B2b service. The PPP positioning method includes the following steps: Step 1. Data acquisition.

[0014] Obtain the satellite phase observations, pseudorange observation data, and products required for data processing (i.e., PPP positioning) at the station, including broadcast ephemeris, various corrections broadcast by the B2b signal, and antenna phase center products, etc.

[0015] Step 2. Data pre - processing.

[0016] Using the broadcast ephemeris, conduct data quality inspection and gross error rejection on the observations obtained in Step 1, delete satellite data without satellite ephemeris or with incomplete observations, and delete satellites without B2b signal corrections or with abnormal B2b signal corrections according to the validity period of the B2b signal correction information and the user's ranging accuracy index. The purpose is to provide data reliability guarantee, filter out invalid data in advance, reduce unnecessary computational workload, and prevent divergence of iterative calculations caused by data quality problems.

[0017] Meanwhile, determine whether the satellite clock corrections of the satellites with normal B2b signal corrections in the current epoch are continuous and mark them. The process of determining whether the satellite clock corrections of the satellites with normal B2b signal corrections in the current epoch are continuous is as follows: If the satellite clock corrections are not continuously broadcast or the B2b signal clock corrections received by the user exceed the data validity period (e.g., 12s), it is considered that the satellite clock corrections of the satellites with normal B2b signal corrections in the current epoch are not continuous.

[0018] Here, the purpose of determining whether the satellite clock corrections are continuous is that within a continuous arc segment, the constant deviation included in the satellite clock corrections is consistent, and constant estimation is used in the solution, which determines the solution strategy for the constant deviation.

[0019] Step 3. Error correction.

[0020] Based on the clock error correction parameters and orbit correction parameters provided by the B2b signal, correct the broadcast ephemeris clock error and orbit respectively; use the inter-code bias correction parameters provided by the B2b signal to correct the pseudorange observation values.

[0021] At the same time, correct the tropospheric delay, relativistic effect, tide, antenna phase center, and earth rotation error.

[0022] Step 4. Establish the PPP mathematical model.

[0023] Taking the dual-frequency ionosphere-free combined PPP positioning as an example, construct the ionosphere-free combined observation values. Considering that the constant deviation of the B2b signal clock error product will be absorbed by the pseudorange residual during the PPP solution, thus affecting the PPP convergence speed, and comprehensively considering the PPP model strength, establish the PPP observation equation considering the satellite constant deviation as shown in the following formula (1): of the PPP observation equation: (1) In the formula, and respectively represent the receiver and satellite numbers; represents the ionosphere-free combined pseudorange observation value, represents the ionosphere-free combined carrier phase observation value; represents the geometric distance from the satellite at the signal emission time to the receiver at the reception time.

[0024] represents the receiver clock error after absorbing the receiver pseudorange hardware delay deviation; represents the satellite clock error; represents the speed of light; represents the projection function from the tropospheric zenith direction of the station to the inclined direction between the station and the satellite.

[0025] represents the wet component delay in the tropospheric zenith direction; represents the wavelength of the ionosphere-free combined ambiguity.

[0026] is the ambiguity parameter, representing the ionosphere-free combined ambiguity that absorbs the B2b signal satellite clock error correction constant deviation, satellite phase hardware delay, receiver phase hardware delay, and receiver pseudorange hardware delay.

[0027] and respectively represent the pseudorange and carrier observation value noises.

[0028] It can be seen from the expression of formula (1) that the ambiguity parameter The satellite clock error correction constant deviation of the B2b signal is absorbed. By introducing the clock error constant deviation parameter in formula (1), it is beneficial to analyze the influence of the constant deviation on the positioning result.

[0029] The present invention constructs a PPP mathematical model based on the PPP-B2b service, fully considering the characteristics of the constant deviation of the B2b satellite clock error correction number, that is, there is a constant deviation in the satellite clock error correction number, but this deviation is the same in continuous arcs and different in different arcs. The satellite clock constant deviation is estimated parametrically, and a piecewise constant estimation strategy is adopted to separate the constant deviation (introducing a constant deviation parameter for estimation, and the piecewise estimation is because the constant deviation is different in different arcs), so as to weaken its influence on other PPP parameters to be estimated, which can effectively shorten the PPP convergence time and improve the PPP positioning performance.

[0030] Calculate the elevation angle of the satellite according to the satellite position and the approximate position of the station, and determine the corresponding stochastic model according to the satellite elevation angle, as shown in formula (2).

[0031] (2) In the formula, represents the variance of the observation value, represents the satellite elevation angle. Errors such as the antenna phase offset and change between the satellite and the receiving antenna, the earth's rotation, the antenna phase winding, the tidal correction, and the relativistic effect are corrected by corresponding models.

[0032] Step 5. Determine the parameter estimation strategy.

[0033] Since the clock error correction number provided by the B2b signal has a satellite-related clock error constant deviation and the deviation is inconsistent in different arcs, according to the satellite ephemeris continuity mark in the data preprocessing in step 2, for adopt the following piecewise constant estimation strategy.

[0034] When the satellite is available and the satellite clock error correction number is continuous, the satellite-related clock error constant deviation remains unchanged. It is necessary to first initialize the satellite constant deviation and then adopt a constant estimation strategy for the satellite constant deviation regard the satellite constant deviation as a constant for estimation, separate the constant deviation, and weaken its influence on the PPP parameters to be estimated.

[0035] When the satellite is unavailable, retain the value and its variance obtained from the last solution when the satellite was available, and when the satellite signal is available again, judge whether the satellite clock error correction number of the currently available satellite is continuously marked.

[0036] If the satellite clock error correction number is continuous, use the Value and its variance are used to estimate the constant bias of the satellite clock error; otherwise, if the satellite clock error correction is discontinuous, then re-initialize, and no longer use the value and its variance retained by the filter. In addition, since the ambiguity parameter absorbs the constant bias of the satellite clock error, the ambiguity parameter also needs to be re-estimated.

[0037] It should be noted here that when the satellite observation value is unavailable, the signal-to-noise ratio of the satellite observation value is lower than the preset signal-to-noise ratio threshold, or the elevation angle is lower than the preset satellite cut-off elevation angle, it indicates that the satellite is unavailable.

[0038] According to the characteristics of the satellite clock error correction, the present invention adopts a piecewise constant estimation processing strategy for the satellite clock error correction in different arcs, which is beneficial to separating the constant bias faster to weaken its influence on other parameters to be estimated in PPP, and can effectively shorten the PPP convergence time and improve the PPP positioning performance.

[0039] Step 6. Parameter estimation.

[0040] Perform Kalman filter estimation according to the mathematical model established in step 4 and the parameter estimation strategy determined in step 5 to obtain the three-dimensional position of the receiver, , tropospheric zenith wet delay, ambiguity, and receiver clock error parameters.

[0041] Embodiment 2 This Embodiment 2 describes a PPP positioning system, which is based on the same inventive concept as the PPP positioning method in the above Embodiment 1. Specifically, the PPP positioning system in this embodiment includes the following modules: Data acquisition module, which is used to acquire satellite phase observation values, pseudorange observation data, broadcast ephemeris, various corrections broadcast by the B2b signal, and antenna phase center products at the measurement station; Preprocessing module, which is used to perform data quality inspection and gross error rejection on the observation values using the broadcast ephemeris, delete satellite data without satellite ephemeris or incomplete observation values, and delete satellites without B2b signal corrections or with abnormal corrections according to the validity period of the B2b signal correction information and the user range accuracy index; at the same time, judge whether the satellite clock error corrections of the satellites with normal B2b signal corrections in the current epoch are continuous and mark them; Error correction module, which is used to perform error correction; PPP mathematical model establishment module, which is used to consider the satellite clock constant bias in the B2b signal clock error correction , establish a PPP mathematical model considering the satellite constant bias, including PPP observation equations and stochastic models; Parameter estimation strategy determination module, which is used to, according to the satellite ephemeris continuity mark, for Adopt a piecewise constant estimation strategy; And a parameter estimation module, which is used to perform Kalman filter estimation according to the established mathematical model and the determined parameter estimation strategy, and obtain the three-dimensional position of the receiver, , tropospheric zenith wet delay, ambiguity, and receiver clock offset parameters.

[0042] It should be noted that in the PPP positioning system of this embodiment, the implementation processes of the functions and roles of each functional module are specifically described in the implementation processes of the corresponding steps in the method in Embodiment 1 above, and will not be elaborated here.

[0043] Embodiment 3 This Embodiment 3 describes a computer device, which includes a memory and one or more processors. An executable code is stored in the memory, and when the processor executes the executable code, it is used to implement the steps of the PPP positioning method in Embodiment 1 above.

[0044] In this embodiment, the computer device is any device or apparatus with data processing capabilities, which will not be elaborated here.

[0045] Embodiment 4 This Embodiment 4 describes a computer-readable storage medium, on which a program is stored. When the program is executed by a processor, it is used to implement the steps of the PPP positioning method in Embodiment 1 above.

[0046] The computer-readable storage medium can be an internal storage unit of any device or apparatus with data processing capabilities, such as a hard disk or memory, or an external storage device of any device with data processing capabilities, such as a plug-in hard disk, a Smart Media Card (SMC), an SD card, a Flash Card, etc. equipped on the device.

[0047] Of course, the above description is only a preferred embodiment of the present invention. The present invention is not limited to listing the above embodiments. It should be noted that all equivalent substitutions and obvious deformation forms made by any person skilled in the art under the teaching of this specification fall within the substantial scope of this specification and should be protected by the present invention.

Claims

1. A PPP positioning method, characterized in that: The steps include: Step 1. Obtain satellite phase observation values, pseudorange observation data, broadcast ephemeris, various correction numbers broadcast by B2b signals, and antenna phase center products at the station; Step 2. Use broadcast ephemeris to check the data quality and remove gross errors of the observations, delete satellite data without satellite ephemeris or with incomplete observations, and delete satellites without B2b signal corrections or with abnormal B2b signal corrections according to the validity period of B2b signal correction information and user ranging accuracy index; at the same time, determine whether the clock corrections of satellites with normal B2b signal corrections in the current epoch are continuous and mark them; Step 3. Error correction; Step 4. Consider the satellite clock constant bias in the B2b signal clock correction , establish a PPP mathematical model that takes into account satellite constant bias, including the PPP observation equation and the stochastic model; Step 5. According to whether the satellite ephemeris is continuously marked in step 2, Adopt piecewise constant estimation strategy; Step 6. Perform Kalman filter estimation based on the mathematical model established in step 4 and the parameter estimation strategy determined in step 5 to obtain the three-dimensional position of the receiver, , tropospheric zenith wet delay, ambiguity and receiver clock error parameters.

2. The PPP positioning method according to claim 1, characterized in that: In step 2, if the satellite clock correction number is not broadcast continuously or the B2b signal clock correction number received by the user exceeds the data validity period, it is considered that the satellite clock correction number of the normal B2b signal correction number in the current epoch is discontinuous.

3. The PPP positioning method according to claim 1, characterized in that: In step 3, the error correction process is as follows: The broadcast ephemeris clock error and orbit correction are made according to the clock error correction parameters and orbit correction parameters provided by the B2b signal; the pseudorange observation value is corrected using the inter-code deviation correction parameters provided by the B2b signal; At the same time, corrections are made for tropospheric delay, relativistic effects, tides, antenna phase center, and earth rotation errors.

4. The PPP positioning method according to claim 1, characterized in that: In step 4, the satellite constant bias is established The PPP observation equation is shown in formula (1): (1) In the formula, and Represent the receiver and satellite number respectively; represents the ionospheric-free combined pseudorange observation value, represents the ionospheric carrier phase observation value; Indicates the geometric distance from the satellite at the time of signal transmission to the receiver at the time of reception; It represents the receiver clock error after absorbing the receiver pseudorange hardware delay bias; represents the satellite clock error; represents the speed of light; Represents the projection function from the tropospheric zenith direction of the station to the inclination direction of the station and the satellite; It represents the delay of the wet component in the tropospheric zenith direction; The wavelength representing the ionospheric combined ambiguity; is the ambiguity parameter, which represents the ionospheric-free combined ambiguity of the satellite clock correction constant bias, satellite phase hardware delay, receiver phase hardware delay and receiver pseudorange hardware delay of the absorbed B2b signal; and represent the pseudorange and carrier observation noise respectively; The satellite elevation angle is calculated according to the satellite position and the approximate position of the measuring station, and the random model corresponding to the satellite elevation angle is determined according to the satellite elevation angle, as shown in formula (2); (2) In the formula, represents the variance of the observations, Indicates the satellite altitude angle.

5. The PPP positioning method according to claim 1, characterized in that: In step 5, the satellite clock error constant deviation , adopt the following piecewise constant estimation strategy: When the satellite is available and the satellite clock correction number is continuous, the clock error constant deviation associated with the satellite remains unchanged. First, the satellite constant deviation Initialize and then adjust the satellite constant deviation Using the constant estimation strategy, the satellite constant deviation Treat it as a constant for estimation and separate the constant deviation to reduce its impact on the PPP parameters to be estimated; When the satellite is unavailable, keep the last solution when the satellite is available value and its variance, and when the satellite signal is available again, determine whether the satellite clock correction number of the currently available satellite is continuously marked; If the satellite clock correction number is continuous, use the satellite's retained The value and its variance estimate the satellite clock error constant bias; otherwise, Reinitialize and no longer use the retained The values ​​and their variances are calculated and the ambiguity parameters are also re-estimated.

6. The PPP positioning method according to claim 5, characterized in that: In step 5, when the satellite observation value is unavailable, the noise ratio of the satellite observation value is lower than a preset signal-to-noise ratio threshold, or the altitude angle is lower than a preset satellite cutoff altitude angle, it indicates that the satellite is unavailable.

7. A PPP positioning system, characterized in that: Includes the following modules: Data acquisition module, used to obtain satellite phase observation values, pseudorange observation data, broadcast ephemeris, various correction numbers broadcast by B2b signals, and antenna phase center products at the station; The preprocessing module is used to use the broadcast ephemeris to check the data quality of the observations, eliminate gross errors, delete satellite data without satellite ephemeris or with incomplete observations, and delete satellites without B2b signal corrections or with abnormal corrections according to the validity period of the B2b signal correction information and the user ranging accuracy index; at the same time, it is determined whether the clock corrections of satellites with normal B2b signal corrections in the current epoch are continuous and marked; An error correction module, used for performing error correction; PPP mathematical model building module, used to consider the satellite clock error constant deviation in the B2b signal clock error correction number , establish a PPP mathematical model that takes into account satellite constant bias, including the PPP observation equation and the stochastic model; The parameter estimation strategy determination module is used to determine whether the satellite ephemeris is continuously marked. Adopt piecewise constant estimation strategy; and a parameter estimation module, which is used to perform Kalman filter estimation according to the established mathematical model and the determined parameter estimation strategy to obtain the three-dimensional position of the receiver, , stratosphere zenith wet delay, ambiguity and receiver clock error parameters.

8. A computer device comprising a memory and one or more processors, wherein the memory stores executable code, characterized in that: When the processor executes the executable code, the steps of the PPP positioning method according to any one of claims 1 to 6 are implemented.

9. A computer-readable storage medium having a program stored thereon, characterized in that: When the program is executed by a processor, it is used to implement the steps of the PPP positioning method as described in any one of claims 1 to 6.

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