Real-time positioning service stability improving method and system based on GNSS

Abstract

The invention provides a GNSS-based real-time positioning service stability improving method and system, and belongs to the field of satellite navigation and positioning services. According to the method, abnormal identification and elimination are carried out on monitoring receiver data with pseudo-range hopping and pseudo codes inconsistent with carriers, multiple receivers synchronous with a time reference are adopted to participate in clock correction calculation, the effectiveness of precise orbit determination and clock correction calculation is judged and identified, and meanwhile the consistency of calculation results is judged and repaired; estimating a satellite initial position vector and kinetic parameters, and forecasting a satellite orbit and a satellite clock error; and when the precise orbit determination solution and clock correction solution processing process is interrupted, the satellite orbit forecast result and the clock correction forecast result are output as a precise orbit and a clock correction, and the output robustness is guaranteed. According to the invention, the algorithm software of the system end is compensated, so that the calculation and storage burden of the user terminal is reduced, and the availability, continuity and stability of the real-time precise positioning service of the satellite navigation system are improved.

Description

Technical Field

[0001] The present invention belongs to the field of satellite navigation and positioning services, and in particular relates to a method and system for improving the stability of real-time positioning services based on GNSS. Background Art

[0002] Real-time precise positioning service is one of the important services of satellite navigation system. This service supports users to carry out real-time precise single-point positioning processing by broadcasting high-precision satellite orbit and clock products to users, and obtain position and clock parameters at decimeter to centimeter levels. Using real-time observation data from ground monitoring stations and generating and outputting high-precision satellite orbit and clock products in real time, robustly and continuously is an important prerequisite for achieving the goal of precise positioning service. Therefore, it is necessary to continuously improve the stability of real-time positioning services.

[0003] However, due to abnormal conditions such as abnormal observation data quality, data transmission link interruption, and computing and storage resource failure, the generation and output of high-precision satellite orbits and clock error products will experience various abnormal conditions, including but not limited to process interruption, reduced product accuracy, and no effective product broadcast, resulting in reduced accuracy of users' precise positioning results, unreliable positioning results, and even inability to perform real-time precise positioning.

[0004] In the prior art, the real-time positioning service based on the Global Navigation Satellite System (GNSS) can improve the stability of the service by optimizing the calculation of precise single-point positioning. For example, the Chinese patent with application number 202311036378.2 discloses a real-time precise single-point positioning method and system for IGS GNSS real-time service interruption. The method determines the IGS RTS service clock difference variation characteristics of the user end, constructs a real-time GNSS satellite clock difference extrapolation function model; determines that the satellite clock difference fitting sequence length used when the extrapolation accuracy is the highest is the shortest clock difference length that the user needs to save; calculates the fitting GNSS satellite clock difference extrapolation function coefficients when the real-time service is interrupted and extrapolates the real-time satellite clock difference; and performs precise single-point positioning calculations when the IGS GNSS real-time service communication is interrupted. Although the method reduces the impact of GNSS satellite clock error real-time service communication interruption on GNSS users' continuous, high-precision positioning, and establishes a user precise positioning algorithm under the interruption failure scenario of IGS real-time service information, its defect is that it only targets IGS real-time products and only describes the measures that user terminals should take. It cannot be applied to other precise positioning services and is not universal. Summary of the invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, the present invention aims to provide a method and system for improving the stability of real-time positioning services based on GNSS. The abnormal identification of the original observation data takes into account common fault conditions of the monitoring receiver, such as abnormal wild values ​​(jumps) of the pseudorange of the monitoring receiver, abnormal consistency of the pseudocode and the carrier, and failure to return the observation data of the time reference receiver. The possible abnormal conditions of the precise orbit determination processing and clock error solution processing results are monitored from multiple angles to avoid the output of abnormal business processing results. A jump compensation mechanism for satellite clock error products is established to ensure the consistency of the output orbit and clock error products in multiple dimensions. At the same time, the personalized prediction of satellite orbit and clock error is realized by combining the satellite orbit characteristics and the performance characteristics of the on-board atomic clock. After the business processing abnormality occurs, the predicted satellite orbit and clock error are output to the user as precise positioning service products, thereby ensuring the continuity and availability of the precise positioning service and improving the stability of the service.

[0006] In order to achieve the above purpose, the embodiment of the present invention adopts the following technical solution:

[0007] In a first aspect, an embodiment of the present invention provides a method for improving the stability of a real-time positioning service based on GNSS, the method comprising the following steps:

[0008] Step S1, setting at least two monitoring receivers synchronized with the time reference as reference receivers to participate in satellite clock error resolution; when the data of the main reference receiver is interrupted, the satellite clock error resolution is referenced to another reference receiver synchronized with the time reference;

[0009] Step S2, obtaining pseudorange data received by at least three monitoring receivers, identifying and removing jump values ​​in the pseudorange data;

[0010] Step S3, for the pseudorange data with the jump value removed, identify the pseudorange data inconsistent with the carrier data through cycle slip identification and ambiguity calculation, and remove the identified inconsistent pseudorange data and carrier data; perform precise orbit determination solution to obtain orbit determination results and satellite clock error solution results based on the pseudorange data and carrier data after the abnormal data are removed;

[0011] Step S4, judging and identifying the validity of the satellite orbit determination result; if the satellite orbit determination result is determined to be valid, performing orbit prediction based on the satellite position, velocity parameters and dynamic parameters at the initial moment in the satellite orbit determination result; if the satellite orbit determination result is determined to be invalid, using the satellite orbit prediction result of the previous epoch as the predicted orbit of the current epoch and issuing it;

[0012] Step S5, judging and identifying the validity of the clock error solution result; if it is judged to be valid, outputting the satellite clock error parameters of the clock error solution result of the current epoch, and predicting the satellite clock error according to the satellite clock error parameters of the clock error solution result of the current epoch; if it is judged to be invalid, outputting the predicted satellite clock error parameters of the last successfully solved epoch;

[0013] Step S6: Assume that the satellite clock error parameter calculated and sent in the previous epoch i-1 is clk(t i-1 ), the satellite clock error parameter calculated at the current epoch i is clk′(t i ), calculate the difference between the two dclk'(t i ), as the jump value:

[0014] dclk(t i )=clk′(t i )-clk(t i-1 ) (2)

[0015] If the jump value dclk(t i ) is greater than the set fifth threshold, then the jump value dclk(t i ) corrects the satellite clock error parameters calculated at the current epoch i and obtains the value clk(t i ),for:

[0016] clk(t i )=clk′(t i )-dclk(t i ) (3).

[0017] As a preferred embodiment of the present invention, identifying the jump value in the pseudorange data in step S2 specifically includes the following steps:

[0018] Step S21, using a priori satellite orbits, satellite dynamic parameters, satellite clock errors, station positions, station clock errors and other information to calculate the residual values ​​of all pseudorange data at epoch i;

[0019] Step S22, counting the median of all satellite residual values ​​of receiver j at epoch i, and calculating the difference between each satellite residual value and the median;

[0020] Step S23, set a first threshold value to determine whether the difference between each satellite residual value and the median is greater than the first threshold value; if so, identify the satellite pseudorange data with the largest difference as the jump value; epoch value i = i + 1, go to step S21; if not, it is considered that the receiver j of the epoch i has normal pseudorange data for all satellites.

[0021] As a preferred embodiment of the present invention, in step S3, the pseudorange data inconsistent with the carrier data is identified by cycle slip identification and ambiguity calculation, which specifically includes the following steps:

[0022] Step S31, removing repeated pseudorange data and carrier data;

[0023] Step S32, calculating the difference between the ionosphere-free combination of pseudorange data and the ionosphere-free combination of carrier data;

[0024] Step S33, setting a second threshold, judging whether the change amount of the ionosphere-free combination difference of the pseudorange data and the carrier data between two consecutive epochs is greater than the second threshold, if so, the current pseudorange data and the carrier data are regarded as large gross error data and are eliminated; judging whether the change amount of the ionosphere-free combination difference of the pseudorange data and the carrier data between one epoch is greater than the second threshold, if so, the current pseudorange data and the carrier data are identified as large cycle slip data;

[0025] Step S34, dividing the remaining pseudorange data and carrier data into large areas according to the large cycle slip data, and counting the observation data in each large area, and recursively determining the small cycle slip data in each large area; dividing each large area into small areas according to the small cycle slip data, and counting the number of observations in each small area;

[0026] Step S35, setting a third threshold, judging whether the number of observations in the small area is less than the third threshold; if so, marking the pseudorange data and carrier data in the current small area as gross error data, marking the current small area as a gross error small area, and proceeding to step S36; if not, proceeding to step S37;

[0027] Step S36, determining whether the blurriness of the two small areas before and after the gross error small area is consistent, if consistent, the gross error small area is eliminated and the two small areas before and after are merged into one small area, and then proceeding to step S35;

[0028] Step S37, counting the number of observations and ambiguity in the small area, and performing iterative processing of orbit determination solution to calculate the orbit determination residual;

[0029] Step S38, set the fourth threshold value to determine whether the orbit determination residual is greater than the fourth threshold value; if so, remove the pseudorange data and carrier data corresponding to the current orbit determination residual, and return to step S32; if not, it is considered that the inconsistent pseudorange data and carrier data have been removed, and perform precise orbit determination solution to obtain the satellite orbit determination result and satellite clock error solution result.

[0030] As a preferred embodiment of the present invention, the specific process of judging and identifying the validity of the satellite orbit determination result in step S4 is as follows:

[0031] Determine whether the effective epoch number of the satellite numerical orbit is 0; or,

[0032] Determine whether the start and end times of the satellite numerical orbit are invalid; or,

[0033] Determine whether the satellite orbit determination residual is greater than the residual threshold; or,

[0034] Determine whether the data elimination rate is greater than the elimination rate threshold;

[0035] If yes, the satellite orbit determination result is judged to be invalid.

[0036] As a preferred embodiment of the present invention, the orbit determination residual includes an orbit determination pseudorange residual and an orbit determination phase residual; the residual threshold of the orbit determination pseudorange residual is set to 5m, and the residual threshold of the phase residual is set to 5cm.

[0037] As a preferred embodiment of the present invention, the data rejection rate includes a pseudorange rejection rate and a phase rejection rate; and the rejection rate thresholds of the pseudorange and phase data are 40% respectively.

[0038] As a preferred embodiment of the present invention, the specific process of judging and identifying the validity of the clock error solution result in step S5 is as follows:

[0039] Determine whether the pseudorange residual is greater than the pseudorange residual threshold; or

[0040] Determine whether the phase residual is greater than a phase residual threshold; or

[0041] Determine whether the data elimination rate is greater than the elimination rate threshold; or

[0042] Determine whether the clock error solution result has not been observed by more than or equal to two monitoring receivers;

[0043] If so, the satellite clock error solution result of the current epoch is determined to be invalid.

[0044] As a preferred embodiment of the present invention, step S5 performs satellite clock error prediction by constructing a precise clock error model. The precise clock error model is specifically expressed as:

[0045] clk i =a0+a1(t i -t0)(i=1,2,3,…) (1)

[0046] In formula (1), clk i Yes i The satellite clock error parameters at time t0 are the reference time of the satellite clock error parameters, and t i represents the epoch time corresponding to epoch i; the estimated parameters a0 and a1 represent the clock error and clock speed of the reference time t0 respectively.

[0047] As a preferred embodiment of the present invention, when there are at least two known clock error data, the least squares estimation method is used to fit the estimated parameters a0 and a1; after fitting the clock error parameters a0 and a1, formula (1) is used to predict any epoch i or any time t i The satellite clock error parameters.

[0048] In a second aspect, an embodiment of the present invention further provides a GNSS-based real-time positioning service stability improvement system, the system comprising: a reference receiver setting module, a pseudorange jump value identification module, a consistency processing module, an orbit determination validity determination and orbit prediction module, a clock error validity determination and clock error prediction module and a clock error parameter correction module; wherein,

[0049] The reference receiver setting module is used to set at least two monitoring receivers synchronized with the time reference as reference receivers to participate in the satellite clock error solution; when the data of the main reference receiver is interrupted, the satellite clock error solution is referenced to another reference receiver synchronized with the time reference;

[0050] The pseudorange jump value identification module is used to obtain pseudorange data received by at least three monitoring receivers, identify jump values ​​in the pseudorange data and remove them;

[0051] The consistency processing module is used to identify the pseudorange data that is inconsistent with the carrier data through cycle slip identification and ambiguity calculation for the pseudorange data from which the jump value is removed, and to remove the identified inconsistent pseudorange data and carrier data; based on the pseudorange data and carrier data from which the abnormal data is removed, perform precise orbit determination to obtain orbit determination results and satellite clock error solution results;

[0052] The orbit determination validity judgment and orbit prediction module is used to judge and identify the validity of the satellite orbit determination result; if the satellite orbit determination result is determined to be valid, the orbit prediction is performed based on the satellite position, velocity parameters and dynamic parameters at the initial time in the satellite orbit determination result; if the satellite orbit determination result is determined to be invalid, the satellite orbit prediction result of the previous epoch is used as the predicted orbit of the current epoch and issued;

[0053] The clock error validity judgment and clock error prediction module is used to judge and identify the validity of the clock error solution result; if it is judged to be valid, the satellite clock error parameters of the clock error solution result of the current epoch are output, and the satellite clock error is predicted based on the satellite clock error parameters of the clock error solution result of the current epoch; if it is judged to be invalid, the predicted satellite clock error parameters of the last successfully solved epoch are output;

[0054] The clock error parameter correction module is used to set the satellite clock error parameter calculated and sent in the previous epoch i-1 as clk(t i-1 ), the satellite clock error parameter calculated at the current epoch i is clk′(ti ), calculate the difference dclk'(t i ), as the jump value: dclk(t i )=clk′(t i )-clk(t i-1 ); if the jump value dclk(t i ) is greater than the set fifth threshold, then the jump value dclk(t i ) corrects the satellite clock error parameters calculated at the current epoch i and obtains the value clk(t i ), is: clk(t i )=clk′(t i )-dclk(t i ).

[0055] The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0056] The method and system for improving the stability of real-time positioning services based on GNSS provided in the embodiments of the present invention establish a complete set of robust output solutions for precise orbit and clock error products from the satellite navigation precise positioning service system end, rather than just compensation through the user terminal, which greatly reduces the computational storage burden of the user terminal; the established robust output solution for satellite orbit and clock error is applicable not only to IGS real-time precise services, but also to all similar real-time services for precise satellite navigation positioning. This application involves a comprehensive, multi-link robust output solution for satellite orbit and clock error products, including the identification and control of anomalies in key input data for the generation of precise orbit and clock error products for precise positioning services, monitoring and screening of core business processing results, and forecasting of precise orbit and clock error products, which is of great significance to the improvement of the availability and continuity of real-time precise positioning services of satellite navigation systems and the upgrading of corresponding industries.

[0057] Of course, it is not necessary to achieve all of the advantages described above at the same time to implement any product or method of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments 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 creative work.

[0059] Figure 1 It is a flow chart of a method for improving stability of a real-time positioning service based on GNSS according to an embodiment of the present invention. DETAILED DESCRIPTION

[0060] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. The components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations. It should be noted that the embodiments of the present invention and the features in the embodiments can also be combined with each other without conflict.

[0061] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In the description of the present invention, the terms "first", "second", "third", "fourth", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0062] In view of the problems of poor stability and low universality of the real-time positioning service based on GNSS in the prior art, the present invention proposes a method and system for improving the stability of real-time positioning service based on GNSS to solve the following specific problems: (1) Establishing all-round and full-link monitoring and guarantee for the output stability of high-precision satellite orbit and clock error products from three perspectives: observation data anomaly detection and adaptive processing, satellite precise orbit determination and clock error solution processing result quality monitoring and control, and high-precision prediction of satellite orbit and clock error products, so as to fundamentally avoid the serious reduction in the accuracy of satellite orbit and clock error products or even interruption of service caused by various anomalies such as observation data anomaly, data transmission link interruption, precise orbit determination processing anomaly, clock error solution processing anomaly, business processing calculation and storage resource anomaly; (2) Monitoring the ground receiver pseudorange abnormal wild value (jump), pseudocode and carrier consistency anomaly, time reference receiver abnormality, etc. (1) Detect anomalies in the original observation data input for business processing from multiple angles such as the failure of observation data to be returned, and establish corresponding applicable disposal strategies to ensure that anomalies in observation data do not enter the core processing processes such as precise orbit determination and clock error solution, and avoid affecting the output of satellite orbit and clock error products; (2) Establish a quality control plan for satellite precise orbit determination results from the angles of orbit determination residuals, data removal amount, overlapping arc segments, and orbit result consistency; and establish a quality control plan for satellite clock error results from the angles of real-time clock error estimation residuals, data removal amount, and clock error result consistency to avoid serious accuracy degradation and invalid product output, repair product jumps, and ensure service continuity; (3) Establish a satellite orbit and clock error prediction method, as well as a robust output mechanism for orbit and clock error products for precise positioning services based on orbit prediction results and clock error prediction results, to ensure the continuity and availability of precise positioning services under abnormal circumstances.

[0063] like Figure 1 As shown, the method for improving the stability of a real-time positioning service based on GNSS provided in an embodiment of the present invention comprises the following steps:

[0064] Step S1, set at least two monitoring receivers synchronized with the time reference as reference receivers to participate in satellite clock error solution; when the data of the main reference receiver is interrupted, the satellite clock error solution is referenced to another reference receiver synchronized with the time reference.

[0065] In this step, considering that the data return delay of the reference receiver connected to the time reference is too large, which will cause the satellite clock error solution result to jump, it is proposed that multiple receivers synchronized with the time reference participate in the clock error solution, so as to overcome the problem of excessive delay of the time reference receiver and effectively control the jump of the satellite clock error.

[0066] Step S2, obtaining pseudo-range data received by at least three monitoring receivers, identifying and removing jump values ​​in the pseudo-range data.

[0067] This step is one of the processes for anomaly identification and detection of input data for precise orbit determination and clock error solution services. The input data that need to be identified for anomalies here include monitoring receiver pseudorange jumps, pseudocode carrier inconsistencies, time reference receiver return delays, etc. The ultimate goal of data anomaly identification is to identify the above data anomalies as accurately and quickly as possible, and avoid their impact on business processing as much as possible.

[0068] In this step, the jump value in the pseudorange data is identified by using a multi-station data consistency analysis method based on the median of the prior residual value. The principle is to use the median to judge and identify the jump value in the pseudorange data. The jump value is insensitive to the jump of the median. Specifically, the following steps are included:

[0069] Step S21, using a priori satellite orbits, satellite dynamic parameters, satellite clock errors, station positions, station clock errors and other information to calculate the residual values ​​of all pseudorange data at epoch i;

[0070] Step S22, counting the median of all satellite residual values ​​of receiver j at epoch i, and calculating the difference between each satellite residual value and the median;

[0071] Step S23, set a first threshold value to determine whether the difference between each satellite residual value and the median is greater than the first threshold value; if so, identify the satellite pseudorange data with the largest difference as the jump value; epoch value i = i + 1, go to step S21; if not, it is considered that the receiver j of the epoch i has normal pseudorange data for all satellites.

[0072] In step S22, the setting of the size of the first threshold needs to take into account the effect of data elimination and the risk of misoperation. If the first threshold is set too large, gross errors cannot be completely eliminated, and if the first threshold is set too small, too much normal data will be eliminated. The first threshold is reasonably selected based on repeated analysis and testing. By introducing a priori orbital dynamics parameters, the first threshold takes a smaller value.

[0073] Step S3, for the pseudorange data with jump values ​​removed, the pseudorange data inconsistent with the carrier data are identified through cycle slip identification and ambiguity calculation, and the identified inconsistent pseudorange data and carrier data are removed; based on the pseudorange data and carrier data after the abnormal data are removed, precise orbit determination solution is performed to obtain the orbit determination result and the satellite clock error solution result.

[0074] In this step, cycle slip identification and ambiguity calculation are important prerequisites for using GNSS carrier phase data to achieve precise orbit determination and clock error resolution. Therefore, cycle slip identification and ambiguity calculation can be used to identify pseudorange data that is inconsistent with carrier data. When performing the identification, it includes preliminary preprocessing and orbit determination preprocessing, which specifically includes the following steps:

[0075] Step S31, removing repeated pseudorange data and carrier data;

[0076] Step S32, calculating the difference between the ionosphere-free combination of pseudorange data and the ionosphere-free combination of carrier data;

[0077] Step S33, setting a second threshold, judging whether the change amount of the ionosphere-free combination difference of the pseudorange data and the carrier data between two consecutive epochs is greater than the second threshold, if so, the current pseudorange data and the carrier data are regarded as large gross error data and are eliminated; judging whether the change amount of the ionosphere-free combination difference of the pseudorange data and the carrier data between one epoch is greater than the second threshold, if so, the current pseudorange data and the carrier data are identified as large cycle slip data;

[0078] Step S34, dividing the remaining pseudorange data and carrier data into large areas according to the large cycle slip data, and counting the observation data in each large area, and recursively determining the small cycle slip data in each large area; dividing each large area into small areas according to the small cycle slip data, and counting the number of observations in each small area;

[0079] Step S35, setting a third threshold, judging whether the number of observations in the small area is less than the third threshold; if so, marking the pseudorange data and carrier data in the current small area as gross error data, marking the current small area as a gross error small area, and proceeding to step S36; if not, proceeding to step S37;

[0080] Step S36, determining whether the blurriness of the two small areas before and after the gross error small area is consistent, if consistent, the gross error small area is eliminated and the two small areas before and after are merged into one small area, and then proceeding to step S35;

[0081] Step S37, counting the number of observations and ambiguity in the small area, and performing iterative processing of orbit determination solution to calculate the orbit determination residual;

[0082] Step S38, set the fourth threshold value to determine whether the orbit determination residual is greater than the fourth threshold value; if so, remove the pseudorange data and carrier data corresponding to the current orbit determination residual, and return to step S32; if not, it is considered that the inconsistent pseudorange data and carrier data have been removed, and perform precise orbit determination solution to obtain the satellite orbit determination result and satellite clock error solution result.

[0083] In steps S1 to S3, this embodiment proposes monitoring and response strategies for common failure conditions of monitoring receivers in the process of generating precise positioning service orbit and clock error products, such as abnormal wild values ​​(jumps) of pseudoranges of monitoring receivers, abnormal consistency between pseudocodes and carriers, and failure to return observation data of time reference receivers, and effectively improves the accuracy and stability of the output.

[0084] Step S4, judging and identifying the validity of the satellite orbit determination result; if the satellite orbit determination result is judged to be valid, an orbit prediction is performed based on the satellite position, velocity parameters and dynamic parameters at the initial moment in the satellite orbit determination result; if the satellite orbit determination result is judged to be invalid, the satellite orbit prediction result of the previous epoch is used as the predicted orbit of the current epoch and issued.

[0085] In this step, the mechanism for judging the output of the satellite orbit determination process is enhanced to address the orbit determination failure caused by the failure to detect abnormal observation data and abnormal orbit determination input in a timely manner. The satellite orbit determination process software has a mechanism to control the output of poor orbit determination results to the memory by means of residuals, data removal amount, and overlapping arc segment judgment. On this basis, the judgment of the integrity and validity of the orbit determination output results is added. If the following situations occur, it is judged that the satellite values ​​will not be sent to the shared memory, but the last orbit determination result will be continued.

[0086] The specific process of judging and identifying the validity of the satellite orbit determination result is as follows:

[0087] Determine whether the effective epoch number of the satellite numerical orbit is 0; or,

[0088] Determine whether the start and end times of the satellite numerical orbit are invalid; or,

[0089] Determine whether the satellite orbit determination residual is greater than the residual threshold; or,

[0090] Determine whether the data elimination rate is greater than the elimination rate threshold;

[0091] If yes, the satellite orbit determination result is judged to be invalid.

[0092] The orbit determination residual includes the orbit determination pseudorange residual and the orbit determination phase residual. For example, the orbit determination pseudorange residual is greater than 5m, and the phase residual is greater than 5cm.

[0093] The data rejection rate includes a pseudo-range rejection rate and a phase rejection rate. For example, the rejection rate thresholds of pseudo-range and phase data are 40% respectively.

[0094] Step S5, judge and identify the validity of the clock error solution result; if it is judged to be valid, output the satellite clock error parameters of the clock error solution result of the current epoch, and predict the satellite clock error based on the satellite clock error parameters of the clock error solution result of the current epoch; if it is judged to be invalid, output the predicted satellite clock error parameters of the last successfully solved epoch.

[0095] In this step, the validity of the satellite clock error solution result is judged. Preferably, the specific process of judging and identifying the validity of the clock error solution result is as follows:

[0096] Determine whether the pseudorange residual is greater than the pseudorange residual threshold, such as 5m; or

[0097] Determine whether the phase residual is greater than a phase residual threshold, such as 0.2m; or

[0098] Determine whether the data rejection rate is greater than a rejection rate threshold, such as 60%; or

[0099] Determine whether the clock error solution result has not been observed by more than or equal to two monitoring receivers;

[0100] If so, the satellite clock error solution result of the current epoch is determined to be invalid.

[0101] In this step, by setting the judgment condition of "determining whether the clock error solution result has not been observed by more than or equal to two monitoring receivers", the data that cannot be observed by at least two monitoring receivers will be used as data for generating invalid results, thereby improving the accuracy and precision of the solution.

[0102] In this step, the satellite clock error prediction is performed by constructing a precise clock error model. When predicting, the satellite clock error parameters of the clock error solution result of the current epoch are used as input, and the precise clock error model outputs the predicted satellite clock error parameters of the subsequent epochs. There is no limit on the number of subsequent epochs here. According to the physical properties of the onboard atomic clock, when constructing a precise clock error model, a quadratic polynomial model containing the phase (clock error), frequency (clock speed), and frequency drift rate (clock drift) that characterize the time-frequency characteristics of the satellite clock is usually used, or a linear polynomial model containing only the phase (clock error) and frequency (clock speed). Taking into account that the arc segment of the satellite clock error data used for clock error parameter fitting is relatively short, a linear polynomial model is used to fit the clock error parameters, and its specific expression is:

[0103] clk i =a0+a1(t i -t0)(i=1,2,3,…) (1)

[0104] In formula (1), clk i Yes i The satellite clock error parameters at time t0 are the reference time of the satellite clock error parameters, and t i represents the epoch time corresponding to epoch i; the estimated parameters a0 and a1 represent the clock error and clock speed of the reference time t0 respectively; when there are at least two known clock error data, the least squares estimation method can be used to fit the estimated parameters a0 and a1. After fitting the clock error parameters a0 and a1, formula (1) can be used to predict any epoch i or any time t i The satellite clock error parameters.

[0105] Step S6: Assume that the satellite clock error parameter calculated and sent in the previous epoch i-1 is clk(t i-1 ), the satellite clock error parameter calculated at the current epoch i is clk′(t i ), calculate the difference dclk'(t i ), as the jump value:

[0106] dclk(t i )=clk′(t i )-clk(t i-1 ) (2)

[0107] If the jump value dclk(t i ) is greater than the set fifth threshold, then the jump value dclk(t i ) corrects the satellite clock error parameters calculated at the current epoch i and obtains the value clk(t i ),for:

[0108] clk(t i )=clk′(t i)-dclk(t i ) (3).

[0109] In step S4 to step S6, this embodiment monitors abnormal conditions in the satellite precise orbit determination process and the clock error solution process, and establishes a targeted handling strategy.

[0110] Based on the same idea, an embodiment of the present invention also provides a GNSS-based real-time positioning service stability improvement system, which includes: a reference receiver setting module, a pseudorange jump value identification module, a consistency processing module, an orbit determination validity judgment and orbit prediction module, a clock difference validity judgment and clock difference prediction module and a clock difference parameter correction module.

[0111] The reference receiver setting module is used to set at least two monitoring receivers synchronized with the time reference as reference receivers to participate in the satellite clock error solution; when the data of the main reference receiver is interrupted, the satellite clock error solution is referenced to another reference receiver synchronized with the time reference;

[0112] The pseudorange jump value identification module is used to obtain pseudorange data received by at least three monitoring receivers, identify jump values ​​in the pseudorange data and remove them;

[0113] The consistency processing module is used to identify the pseudorange data that is inconsistent with the carrier data through cycle slip identification and ambiguity calculation for the pseudorange data from which the jump value is removed, and to remove the identified inconsistent pseudorange data and carrier data; based on the pseudorange data and carrier data from which the abnormal data is removed, perform precise orbit determination to obtain orbit determination results and satellite clock error solution results;

[0114] The orbit determination validity judgment and orbit prediction module is used to judge and identify the validity of the satellite orbit determination result; if the satellite orbit determination result is determined to be valid, the orbit prediction is performed based on the satellite position, velocity parameters and dynamic parameters at the initial time in the satellite orbit determination result; if the satellite orbit determination result is determined to be invalid, the satellite orbit prediction result of the previous epoch is used as the predicted orbit of the current epoch and issued;

[0115] The clock error validity judgment and clock error prediction module is used to judge and identify the validity of the clock error solution result; if it is judged to be valid, the satellite clock error parameters of the clock error solution result of the current epoch are output, and the satellite clock error is predicted based on the satellite clock error parameters of the clock error solution result of the current epoch; if it is judged to be invalid, the predicted satellite clock error parameters of the last successfully solved epoch are output;

[0116] The clock error parameter correction module is used to set the satellite clock error parameter calculated and sent in the previous epoch i-1 as clk(t i-1 ), the satellite clock error parameter calculated at the current epoch i is clk′(t i), calculate the difference between the two dclk'(t i ), as the jump value: dclk(t i )=clk′(t i )-clk(t i-1 ); if the jump value dclk(t i ) is greater than the set fifth threshold, then the jump value dclk(t i ) corrects the satellite clock error parameters calculated at the current epoch i and obtains the value clk(t i ), is: clk(t i )=clk′(t i )-dclk(t i ).

[0117] In this embodiment, each module is implemented by a processor, and a memory is appropriately added when storage is required. Among them, the processor can be but is not limited to a microprocessor MPU, a central processing unit (CPU), a network processor (NP), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), other programmable logic devices, discrete gates, transistor logic devices, discrete hardware components, etc. The memory can include a random access memory (RAM) and can also include a non-volatile memory (NVM), such as at least one disk storage. Optionally, the memory can also be at least one storage device located away from the aforementioned processor.

[0118] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions can be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center.

[0119] It should also be noted that the GNSS-based real-time positioning service stability improvement system described in this embodiment corresponds to the GNSS-based real-time positioning service stability improvement method, and the description and limitation of the method are also applicable to the system and will not be repeated here.

[0120] It can be seen from the above technical solutions that the method and system for improving the stability of real-time positioning services based on GNSS provided in the embodiments of the present invention establish a complete set of robust output solutions for precise orbit and clock error products from the satellite navigation precise positioning service system end, rather than just compensation through the user terminal, which greatly reduces the computational storage burden of the user terminal; not only for IGS real-time precise services, the established robust output solution for satellite orbit and clock error is applicable to all similar real-time services for satellite navigation precise positioning. The present application involves a comprehensive, multi-link robust output solution for satellite orbit and clock error products, including the identification and control of anomalies in key input data for the generation of precise orbit and clock error products for precise positioning services, monitoring and screening of core business processing results, and forecasting of precise orbit and clock error products, which is of great significance to the availability and continuity improvement of real-time precise positioning services of satellite navigation systems and the corresponding industrial upgrading.

[0121] The above description is only a preferred embodiment of the present invention and an explanation of the technical principles used. It is not intended to limit the scope of the invention claimed for protection, but only represents the preferred embodiment of the present invention. Those skilled in the art should understand that the scope of the invention involved in the present invention is not limited to the technical solution formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

Claims

1. A method for improving the stability of real-time positioning services based on GNSS, characterized in that: The method comprises the following steps: Step S1, setting at least two monitoring receivers synchronized with the time reference as reference receivers to participate in satellite clock error resolution; when the data of the main reference receiver is interrupted, the satellite clock error resolution is referenced to another reference receiver synchronized with the time reference; Step S2, obtaining pseudorange data received by at least three monitoring receivers, identifying and removing jump values ​​in the pseudorange data; Step S3, for the pseudorange data from which the jump value is removed, identifying the pseudorange data that is inconsistent with the carrier data through cycle slip identification and ambiguity calculation, and removing the inconsistent pseudorange data and carrier data; Based on the pseudorange data and carrier data after eliminating abnormal data, precise orbit determination is performed to obtain orbit determination results and satellite clock error solution results; Step S4, judging and identifying the validity of the satellite orbit determination result; If the satellite orbit determination result is determined to be valid, the orbit prediction is performed based on the satellite position, velocity parameters and dynamic parameters at the initial moment in the satellite orbit determination result; If the satellite orbit determination result is judged to be invalid, the satellite orbit prediction result of the previous epoch will be used as the predicted orbit of the current epoch and issued; Step S5, judging and identifying the validity of the clock error solution result; If it is determined to be valid, the satellite clock error parameters of the clock error solution result of the current epoch are output, and the satellite clock error is predicted according to the satellite clock error parameters of the clock error solution result of the current epoch; If it is judged to be invalid, the predicted satellite clock error parameters of the last successfully solved epoch are output; Step S6: Assume that the satellite clock error parameter calculated and sent in the previous epoch i-1 is clk(t i-1 ), the satellite clock error parameter calculated at the current epoch i is clk′(t i ), calculate the difference between the two dclk'(t i ), as the jump value: dclk(t i )=clk′(t i )-clk(t i-1 ) (2) If the jump value dclk(t i ) is greater than the set fifth threshold, then the jump value dclk(t i ) corrects the satellite clock error parameters calculated at the current epoch i and obtains the value clk(t i ),for: clk(t i )=clk′(t i )-dclk(t i ) (3)。 2. The method for improving the stability of a real-time positioning service based on GNSS according to claim 1, characterized in that: In step S2, the jump value in the pseudorange data is identified, which specifically includes the following steps: Step S21, using a priori satellite orbits, satellite dynamic parameters, satellite clock errors, station positions, station clock errors and other information to calculate the residual values ​​of all pseudorange data at epoch i; Step S22, counting the median of all satellite residual values ​​of receiver j at epoch i, and calculating the difference between each satellite residual value and the median; Step S23, setting a first threshold value, and determining whether the difference between each satellite residual value and the median is greater than the first threshold value; If yes, the satellite pseudorange data with the largest difference is identified as the jump value; the epoch value i=i+1, and the process goes to step S21; If not, it is considered that the pseudorange data of all satellites for receiver j at epoch i are normal.

3. The method for improving the stability of a real-time positioning service based on GNSS according to claim 1, characterized in that: In step S3, the pseudorange data inconsistent with the carrier data is identified by cycle slip identification and ambiguity calculation, which specifically includes the following steps: Step S31, removing repeated pseudorange data and carrier data; Step S32, calculating the difference between the ionosphere-free combination of pseudorange data and the ionosphere-free combination of carrier data; Step S33, setting a second threshold, judging whether the change amount of the ionosphere-free combination difference of the pseudorange data and the carrier data between two consecutive epochs is greater than the second threshold, if so, the current pseudorange data and the carrier data are regarded as large gross error data and are eliminated; judging whether the change amount of the ionosphere-free combination difference of the pseudorange data and the carrier data between one epoch is greater than the second threshold, if so, the current pseudorange data and the carrier data are identified as large cycle slip data; Step S34, dividing the remaining pseudorange data and carrier data into large areas according to the large cycle slip data, and performing statistics on the observation data in each large area, and determining the small cycle slip data in each large area in a recursive manner; Divide each large area into small areas according to the small cycle slip data, and count the number of observations in each small area; Step S35, setting a third threshold, judging whether the number of observations in the small area is less than the third threshold; if so, marking the pseudorange data and carrier data in the current small area as gross error data, marking the current small area as a gross error small area, and proceeding to step S36; if not, proceeding to step S37; Step S36, determining whether the blurriness of the two small areas before and after the gross error small area is consistent, if consistent, the gross error small area is eliminated and the two small areas before and after are merged into one small area, and then proceeding to step S35; Step S37, counting the number of observations and ambiguity in the small area, and performing iterative processing of orbit determination solution to calculate the orbit determination residual; Step S38, set the fourth threshold value to determine whether the orbit determination residual is greater than the fourth threshold value; if so, remove the pseudorange data and carrier data corresponding to the current orbit determination residual, and return to step S32; if not, it is considered that the inconsistent pseudorange data and carrier data have been removed, and perform precise orbit determination solution to obtain the satellite orbit determination result and satellite clock error solution result.

4. The method for improving the stability of a real-time positioning service based on GNSS according to claim 1, characterized in that: The specific process of judging and identifying the validity of the satellite orbit determination result in step S4 is as follows: Determine whether the effective epoch number of the satellite numerical orbit is 0; or, Determine whether the start and end times of the satellite numerical orbit are invalid; or, Determine whether the satellite orbit determination residual is greater than the residual threshold; or, Determine whether the data elimination rate is greater than the elimination rate threshold; If yes, the satellite orbit determination result is judged to be invalid.

5. The method for improving the stability of real-time positioning service based on GNSS according to claim 4, characterized in that: The orbit determination residuals include orbit determination pseudorange residuals and orbit determination phase residuals; the residual threshold of the orbit determination pseudorange residuals is set to 5m, and the residual threshold of the phase residuals is set to 5cm.

6. The method for improving the stability of a real-time positioning service based on GNSS according to claim 4, characterized in that: The data rejection rate includes a pseudorange rejection rate and a phase rejection rate; and the rejection rate thresholds of pseudorange and phase data are 40% respectively.

7. The method for improving the stability of real-time positioning service based on GNSS according to claim 1, characterized in that: The specific process of judging and identifying the validity of the clock error solution result in step S5 is as follows: Determine whether the pseudorange residual is greater than the pseudorange residual threshold; or Determine whether the phase residual is greater than a phase residual threshold; or Determine whether the data elimination rate is greater than the elimination rate threshold; or Determine whether the clock error solution result has not been observed by more than or equal to two monitoring receivers; If so, the satellite clock error solution result of the current epoch is determined to be invalid.

8. The method for improving the stability of real-time positioning service based on GNSS according to claim 1, characterized in that: Step S5 performs satellite clock error prediction by constructing a precise clock error model. The precise clock error model is specifically expressed as: clk i =a0+a1(t i -t0)(i=1,2,3,…) (1) In formula (1), clk i Yes i The satellite clock error parameters at time t0 are the reference time of the satellite clock error parameters, and t i represents the epoch time corresponding to epoch i; the estimated parameters a0 and a1 represent the clock error and clock speed of the reference time t0 respectively.

9. The method for improving the stability of a real-time positioning service based on GNSS according to claim 8, characterized in that: When there are at least two known clock error data, the least squares estimation method is used to fit the estimated parameters a0 and a1. After fitting the clock error parameters a0 and a1, equation (1) is used to predict any epoch i or any time t i The satellite clock error parameters.

10. A GNSS-based real-time positioning service stability improvement system, characterized in that: The system comprises: a reference receiver setting module, a pseudorange jump value identification module, a consistency processing module, an orbit determination validity determination and orbit prediction module, a clock error validity determination and clock error prediction module and a clock error parameter correction module; wherein, The reference receiver setting module is used to set at least two monitoring receivers synchronized with the time reference as reference receivers to participate in the satellite clock error solution; when the data of the main reference receiver is interrupted, the satellite clock error solution is referenced to another reference receiver synchronized with the time reference; The pseudorange jump value identification module is used to obtain pseudorange data received by at least three monitoring receivers, identify jump values ​​in the pseudorange data and remove them; The consistency processing module is used to identify the pseudorange data that is inconsistent with the carrier data through cycle slip identification and ambiguity calculation for the pseudorange data from which the jump value is removed, and to remove the identified inconsistent pseudorange data and carrier data; based on the pseudorange data and carrier data from which the abnormal data is removed, perform precise orbit determination to obtain orbit determination results and satellite clock error solution results; The orbit determination validity judgment and orbit prediction module is used to judge and identify the validity of the satellite orbit determination result; if the satellite orbit determination result is determined to be valid, the orbit prediction is performed based on the satellite position, velocity parameters and dynamic parameters at the initial time in the satellite orbit determination result; if the satellite orbit determination result is determined to be invalid, the satellite orbit prediction result of the previous epoch is used as the predicted orbit of the current epoch and issued; The clock error validity judgment and clock error prediction module is used to judge and identify the validity of the clock error solution result; if it is judged to be valid, the satellite clock error parameters of the clock error solution result of the current epoch are output, and the satellite clock error is predicted based on the satellite clock error parameters of the clock error solution result of the current epoch; if it is judged to be invalid, the predicted satellite clock error parameters of the last successfully solved epoch are output; The clock error parameter correction module is used to set the satellite clock error parameter calculated and sent in the previous epoch i-1 as clk(t i-1 ), the satellite clock error parameter calculated at the current epoch i is clk′(t i ), calculate the difference between the two dclk'(t i ), as the jump value: dclk(t i )=clk′(t i )-clk(t i-1 ); if the jump value dclk(t i ) is greater than the set fifth threshold, then the jump value dclk(t i ) corrects the satellite clock error parameters calculated at the current epoch i and obtains the value clk(t i ), is: clk(t i )=clk′(t i )-dclk(t i ).

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