A method for real-time pseudorange quality control of the BeiDou satellite-based augmentation system

Abstract

This invention proposes a method for real-time pseudorange quality control in the BeiDou satellite-based augmentation system, comprising: calculating n pseudorange residuals at time t; determining whether the number of original pseudorange residuals n is greater than or equal to a preset parameter; subtracting the mean residual from the original pseudorange residual of each satellite; dividing the centered pseudorange residual of each satellite by the dual-frequency pseudorange noise; calculating the test statistic X; determining whether the test statistic X is less than the 95th quantile of the chi-square distribution with n-4 degrees of freedom; removing the satellite with the largest absolute value of the normalized pseudorange residual; completing the removal of pseudorange outliers; and obtaining the current pseudorange residual. This invention is real-time, meeting the high real-time requirements of differential integrity processing in the BeiDou satellite-based augmentation system. The embodiments of this invention can identify and remove small abnormal pseudoranges in the BeiDou interplanetary augmentation system, achieving good pseudorange quality control.

Description

Technical Field

[0001] This invention relates to the field of BeiDou satellite-based augmentation technology, and in particular to a method for real-time pseudorange quality control of BeiDou satellite-based augmentation systems. Background Technology

[0002] The BeiDou Satellite Based Augmentation System (BDSBAS) is a satellite-based augmentation system independently constructed by my country in accordance with international standards. Through monitoring stations distributed throughout China, it receives real-time observation data such as pseudorange and carrier phase from GNSS satellites over my country, performs differential and integrity processing, and compiles the data into standard messages. These BDSBAS messages are then widely broadcast via geosynchronous Earth Orbit (GEO) satellites, thereby improving the positioning accuracy and ensuring the integrity of users' positioning.

[0003] Because navigation satellite signals are susceptible to environmental influences, the raw pseudorange data received by the monitoring receiver contains outliers, gross errors, and other abnormal data. If these abnormal data points cannot be removed, it will lead to errors in subsequent BDSBAS differential and integrity processing calculations. Incorrect differential corrections and integrity parameters will degrade or cause malfunctions in BDSBAS service performance. Obtaining "clean" pseudorange residuals through real-time data quality control of pseudorange measurements from BDSBAS monitoring stations is fundamental to the performance of BDSBAS differential corrections and integrity parameters. However, there is currently no publicly available method suitable for real-time pseudorange quality control in BDSBAS. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that there is a current need for a method for real-time pseudorange quality control of BDSBAS. In view of this, the present invention provides a method for real-time pseudorange quality control of the BeiDou satellite-based augmentation system.

[0005] The technical solution adopted in this invention is the method for real-time pseudorange quality control of the BeiDou satellite-based augmentation system, comprising:

[0006] Step 1: Solve for the n pseudorange residuals at time t. If n satellites are observed at the current time, n pseudorange residuals will be obtained accordingly.

[0007] Step 2: Determine whether the number of pseudorange residuals at solution time t is greater than or equal to a preset parameter. If n is greater than or equal to the preset parameter, proceed to step 3; otherwise, proceed to step 9.

[0008] Step 3: Based on the pseudorange residuals of each satellite, determine the mean residual, and subtract the mean residual from the pseudorange residuals of each satellite to obtain the centered pseudorange residual value;

[0009] Step 4: Divide the centered pseudorange residual by the variance of the dual-frequency pseudorange noise to obtain the normalized pseudorange residual measurement.

[0010] Step 5: Sum the squares of the n normalized pseudorange residuals to obtain the test statistic X;

[0011] Step 6: Determine whether the test statistic X is less than the 95th quantile of the chi-square distribution with n-4 degrees of freedom, in order to determine whether there are pseudo-range outliers among the n pseudo-range residuals. If there are no pseudo-range outliers, proceed to step 8; otherwise, proceed to step 7.

[0012] Step 7: Among the n normalized pseudo-range residuals, remove the pseudo-range residual corresponding to the normalized pseudo-range residual with the largest absolute value. The remaining pseudo-range residuals corresponding to the normalized pseudo-range residuals are used as the current set to enter step 2. The removed pseudo-range residuals are pseudo-range outliers.

[0013] Step 8: Repeat steps 2 to 7 above until all pseudorange outliers are removed;

[0014] Step 9: Obtain the current pseudorange residual.

[0015] In one implementation, the preset parameter in step 2 is 5.

[0016] In one implementation, in step 4, the variance of the dual-frequency pseudorange noise is 5.

[0017] In one implementation, determining whether the test statistic X is less than the 95th quantile of the chi-square distribution with n-4 degrees of freedom, in order to determine whether there are pseudorange outliers among the n pseudorange residuals, includes:

[0018] Using the configured quantile correspondence table, the corresponding 95th quantile T is determined according to the value of n-4 in the quantile correspondence table. The test statistic X is compared with T. If X is less than or equal to T, there are no abnormal pseudo-range values ​​in the n pseudo-range residuals, and the process proceeds to step eight. If X is greater than T, there are abnormal pseudo-range values ​​in the n pseudo-range residuals.

[0019] Another aspect of the present invention provides an electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the steps of the method for real-time pseudorange quality control of the BeiDou satellite-based augmentation system as described in any of the preceding claims.

[0020] Another aspect of the present invention provides a computer storage medium storing a computer program that, when executed by a processor, implements the steps of the method for real-time pseudorange quality control of the BeiDou satellite-based augmentation system as described in any of the preceding claims.

[0021] Current pseudorange quality control methods are mostly only applicable to post-processing data and are not suitable for the actual engineering needs of real-time BDSBAS processing. Furthermore, they are ineffective at identifying and removing small pseudorange outliers that frequently occur in BDSBAS. The purpose of this invention is to enable real-time identification and removal of small pseudorange outliers in practical BDSBAS engineering applications. Attached Figure Description

[0022] Figure 1 This is a flowchart of a method for real-time pseudorange quality control of the BeiDou satellite-based augmentation system according to an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of the electronic device structure according to an embodiment of the present invention. Detailed Implementation

[0024] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0025] In the accompanying drawings, the thickness, size, and shape of the objects have been slightly exaggerated for ease of illustration. The drawings are for illustrative purposes only and are not drawn to scale.

[0026] It should also be understood that the terms "comprising," "including," "having," "containing," and / or "comprising," when used in this specification, indicate the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or combinations thereof. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed feature, not individual elements in the list. Additionally, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to an example or illustration.

[0027] As used herein, the terms “basically,” “approximately,” and similar terms are used as terms of approximation rather than terms of degree, and are intended to describe inherent biases in measured or calculated values ​​that will be recognized by those skilled in the art.

[0028] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formal sense unless expressly so specified herein.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] The steps described in the specification and the flowcharts in the accompanying drawings of this invention are not necessarily to be strictly followed according to the step numbers; the execution order of the steps can be changed. Furthermore, certain steps can be omitted, multiple steps can be combined into one step, and / or one step can be broken down into multiple steps.

[0031] Before performing real-time pseudorange quality control using BDSBAS, it is necessary to calculate the pseudorange residuals.

[0032] Using the ionospheric-free pseudorange of the B1C and B2a frequencies of BeiDou Navigation Satellite System (BDS) satellite j, the formula is as follows:

[0033]

[0034] In formula (1) The pseudorange measurement value of satellite j is a combination of dual-frequency ionospheric pseudorange. and These are pseudorange measurements at satellite frequencies jB1Cp and B2ap, respectively; T GDB1Cp and T GDB2ap These are the group delay errors B1Cp and B2ap, respectively, which can be obtained from the BDS B1C and B2a navigation messages. These are the combination coefficients.

[0035] After eliminating ionospheric delay error, and then eliminating station-to-satellite distance, satellite clock error, tropospheric delay error, and relativistic error, the pseudorange residual of satellite j can be obtained, as shown in the following formula:

[0036]

[0037] In equation (2), Δp j The pseudorange residual measurement value for satellite j; x is the distance from the monitoring station to the satellite. nav y nav and z nav x represents the three-dimensional coordinates of the satellite under the ECEF coordinates obtained from the navigation message. site y site z site The precise and known three-dimensional coordinates of the monitoring station in the ECEF coordinate system; This refers to the satellite clock error calculated from the navigation message. This refers to the relativistic error calculated from the model. denoted as t0, where t is the tropospheric delay error calculated using a model; c is the speed of light in a vacuum.

[0038] After the satellite pseudorange residual calculation is completed, real-time pseudorange quality control can be performed to identify and eliminate abnormal pseudorange measurements.

[0039] The first embodiment of the present invention provides a method for real-time pseudorange quality control of the BeiDou satellite-based augmentation system, such as... Figure 1 As shown, the specific steps include the following:

[0040] Step S1: Solve for n pseudorange residuals at time t. If n satellites are observed at the current time, n pseudorange residuals are calculated accordingly.

[0041] Step S2: Determine whether the number of pseudorange residuals at solution time t is greater than or equal to a preset parameter. If n is greater than or equal to the preset parameter, proceed to step S3; otherwise, proceed to step S9.

[0042] Step S3: Based on the pseudorange residuals of each satellite, determine the mean residual and subtract the mean residual from the pseudorange residuals of each satellite to obtain the centered pseudorange residual value.

[0043] Step S4: Divide the centered pseudorange residual by the variance of the dual-frequency pseudorange noise to obtain the normalized pseudorange residual measurement.

[0044] Step S5: Sum the squares of the n normalized pseudorange residuals to obtain the test statistic X;

[0045] Step S6: Determine whether the test statistic X is less than the 95th quantile of the chi-square distribution with n-4 degrees of freedom, in order to determine whether there are pseudo-range outliers among the n pseudo-range residuals. If there are no pseudo-range outliers, proceed to step S8; otherwise, proceed to step S7.

[0046] Step S7: Among the n normalized pseudo-range residuals, remove the pseudo-range residual corresponding to the normalized pseudo-range residual with the largest absolute value. The pseudo-range residual corresponding to the remaining normalized pseudo-range residuals is used as the current set and enters step S2. The removed pseudo-range residuals are the pseudo-range outliers.

[0047] Step S8: Repeat steps S2 to S7 until all pseudorange outliers are removed.

[0048] Step S9: Obtain the current pseudorange residual.

[0049] For example, in step 2, the preset parameter is 5.

[0050] Similarly, in step 4, the variance of the dual-frequency pseudorange noise is 5.

[0051] Specifically, determining whether the test statistic X is less than the 95th quantile of the chi-square distribution with n-4 degrees of freedom is to determine whether there are pseudorange outliers among the n pseudorange residuals. This may include, for example:

[0052] Using the configured quantile correspondence table, the corresponding 95th quantile T is determined according to the value of n-4 in the quantile correspondence table. The test statistic X is compared with T. If X is less than or equal to T, there are no abnormal pseudo-range values ​​in the n pseudo-range residuals, and the process proceeds to step S8; if X is greater than T, there are abnormal pseudo-range values ​​in the n pseudo-range residuals.

[0053] It is understood that the values ​​of some parameters in this invention are not limited to those shown above. In practical applications, those skilled in the art can make reasonable adjustments or modifications to the relevant content and parameters based on the above, and this article will not limit them further.

[0054] Compared with the prior art, the present invention has at least the following advantages:

[0055] 1) It has real-time performance, meeting the high real-time requirements of differential integrity processing in the BeiDou satellite-based augmentation system;

[0056] 2) It can identify and eliminate small abnormal pseudoranges in the BeiDou interplanetary augmentation system, and the pseudorange quality control effect is good.

[0057] 3) The method is simple to implement and requires little engineering work.

[0058] The second embodiment of the present invention is an application example of the present invention, based on the above embodiments.

[0059] Step 1: Calculate the n pseudorange residuals at time t;

[0060] The solution time t is the second within the BDS cycle of the current solution epoch. If n BDS satellites are observed at the current time, n pseudorange residuals can be calculated.

[0061] Step 2: Determine if the number of original pseudorange residuals n is greater than or equal to 5;

[0062] Determine if the number of pseudorange residuals at time t is greater than or equal to 5. If n is greater than or equal to 5, proceed to step three; otherwise, proceed to step nine.

[0063] Step 3: Subtract the mean residual from the original pseudorange residual for each satellite;

[0064] The original pseudorange residuals for each satellite are subtracted from the mean residuals. The formula for calculating the mean pseudorange residuals is as follows:

[0065]

[0066] In the above formula, ΔP mean The mean of the pseudorange residuals; ΔP j Let be the original pseudorange residual of satellite j; n is the total number of pseudorange residuals.

[0067] The centered pseudorange residual value is obtained by subtracting the mean residual value from satellite j, as shown in the following formula:

[0068]

[0069] In the above formula, The pseudorange residual measurement value is centered on satellite j.

[0070] Proceed to step four.

[0071] Step 4: Divide the pseudorange residual centered on each satellite by the dual-frequency pseudorange noise;

[0072] The pseudorange residual centered on each satellite is divided by the dual-frequency pseudorange noise and then normalized. The calculation formula is as follows:

[0073]

[0074] In the above formula, The pseudorange residual measurement value is the normalized value for satellite j. This represents the noise variance for dual-frequency pseudorange measurements.

[0075] Proceed to step five.

[0076] Step 5: Calculate the test statistic X;

[0077] To obtain the test statistic X, sum the squared residuals of the n normalized pseudoranges. The formula is as follows:

[0078]

[0079] In the above formula, the test statistic X is a parameter used to determine whether there are any anomalies among the n pseudorange measurements.

[0080] Proceed to step six.

[0081] Step 6: Test whether the test statistic X is less than the 95th quantile of the chi-square distribution with n-4 degrees of freedom;

[0082] In the absence of faults, the original pseudorange residuals of n (n≥5) satellites are generally considered to follow independent mean ΔP. mean The variance is The normal distribution can be normalized to obtain n independent standard normal distributions. According to statistical distribution theory, the sum of squares of the statistical variables of the n standard normal distributions follows a chi-square distribution of n-4 (χ²). 2 (n-4)). Therefore, we can determine whether the test statistic X conforms to a chi-square distribution with n-4 degrees of freedom (χ²). 2 (n-4)) can be used to determine whether there are pseudo-range outliers among the n pseudo-range residuals.

[0083] χ 2 (1) to χ 2 The 95% score of (100) is shown in Table 1.

[0084] Table 1 χ 2 (1) to χ 2 (100) 95% of the data are divided into tables.

[0085]

[0086]

[0087] Based on the value of n-4, search for the corresponding 95th percentile T in the table above, and compare the test statistic X with T. If X is less than or equal to T, there are no outlier pseudorange values ​​among the n pseudorange residuals, and proceed to step eight; if X is greater than T, there are outlier pseudorange values ​​among the n pseudorange residuals.

[0088] Proceed to step seven.

[0089] Step 7: Remove satellites with the largest absolute value of normalized pseudorange residuals;

[0090] Among the n normalized pseudorange residuals, find the satellite with the largest absolute value, remove it, and include the original pseudorange set of the remaining satellites in step two.

[0091] Step 8: Pseudorange outlier removal complete;

[0092] Step Nine: End.

[0093] End pseudorange quality control to obtain pseudorange residuals that can be used for subsequent BDSBAS differential and integrity processing.

[0094] A third embodiment of the present invention provides an electronic device, such as... Figure 2 As shown, it can be understood as a physical device, including a processor and a memory storing processor-executable instructions, which, when executed by the processor, perform the following operations:

[0095] Step 1: Solve for the n pseudorange residuals at time t. If n satellites are observed at the current time, n pseudorange residuals will be obtained accordingly.

[0096] Step 2: Determine if the number of pseudorange residuals at time t is greater than or equal to a preset parameter. If n is greater than or equal to the preset parameter, proceed to Step 3; otherwise, proceed to Step 9.

[0097] Step 3: Based on the pseudorange residuals of each satellite, determine the mean residual, and subtract the mean residual from the pseudorange residuals of each satellite to obtain the centered pseudorange residual value.

[0098] Step 4: Divide the centered pseudorange residual by the variance of the dual-frequency pseudorange noise to obtain the normalized pseudorange residual measurement.

[0099] Step 5: Sum the squares of the n normalized pseudorange residuals to obtain the test statistic X;

[0100] Step 6: Determine whether the test statistic X is less than the 95th quantile of the chi-square distribution with n-4 degrees of freedom, in order to determine whether there are pseudo-range outliers among the n pseudo-range residuals. If there are no pseudo-range outliers, proceed to step 8; otherwise, proceed to step 7.

[0101] Step 7: Among the n normalized pseudo-range residuals, remove the pseudo-range residual corresponding to the normalized pseudo-range residual with the largest absolute value. The pseudo-range residual corresponding to the remaining normalized pseudo-range residuals is used as the current set to enter step 2. The removed pseudo-range residuals are the pseudo-range outliers.

[0102] Step 8: Repeat steps 2 to 7 above until all pseudorange outliers are removed;

[0103] Step 9: The method ends; obtain the current pseudorange residual.

[0104] In the fourth embodiment of the present invention, the process of the method for real-time pseudorange quality control of the BeiDou satellite-based augmentation system is the same as that of the first, second, or third embodiments. The difference lies in the engineering implementation: this embodiment can be implemented using software plus necessary general-purpose hardware platforms. While hardware implementation is also possible, the former is often a better approach. Based on this understanding, the method of the present invention can be embodied in the form of a computer software product stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), including several instructions to cause a device to execute the method described in the embodiments of the present invention.

[0105] Through the description of specific embodiments, a more in-depth and specific understanding should be gained of the technical means and effects adopted by the present invention to achieve the intended purpose. However, the accompanying drawings are only provided for reference and illustration and are not intended to limit the present invention.

Claims

1. A method for real-time pseudorange quality control of a Beidou satellite-based augmentation system, characterized in that, The method comprises the following steps: Step 1, calculating n pseudo-range residuals at time t, wherein if n satellites are observed at the current time, n pseudo-range residuals are calculated; Step 2, determining whether the number of pseudo-range residuals at time t is greater than or equal to a preset parameter; if n is greater than or equal to the preset parameter, step 3 is entered; otherwise, step 9 is entered; Step 3, determining a residual mean value based on the pseudo-range residuals of each satellite, and subtracting the residual mean value from the pseudo-range residuals of each satellite to obtain a centralized pseudo-range residual value; Step 4, dividing the centralized pseudo-range residual by the variance of the double-frequency pseudo-range noise to obtain a normalized pseudo-range residual measurement value; Step 5, summing the squares of the n normalized pseudo-range residuals to obtain a test statistic X; Step 6, determining whether the test statistic X is less than the 95% quantile of the chi-square distribution with n-4 degrees of freedom to determine whether there is a pseudo-range outlier in the n pseudo-range residuals; if there is no pseudo-range outlier, step 8 is entered; otherwise, step 7 is entered; Step 7, removing the pseudo-range residual corresponding to the normalized pseudo-range residual with the largest absolute value from the n normalized pseudo-range residuals, and taking the pseudo-range residuals corresponding to the remaining normalized pseudo-range residuals as the current set to enter step 2; the removed pseudo-range residual is the pseudo-range outlier; Step 8, repeating steps 2 to 7 until all pseudo-range outliers are removed; Step 9, obtaining the current pseudo-range residual; The determination of whether the test statistic X is less than the 95% quantile of the chi-square distribution with n-4 degrees of freedom to determine whether there is a pseudo-range outlier in the n pseudo-range residuals comprises: determining the corresponding 95% quantile T in the quantile correspondence table according to the value of n-4, comparing the test statistic X with T, if X is less than or equal to T, there is no abnormal pseudo-range value in the n pseudo-range residuals, and step 8 is entered; if X is greater than T, there is an abnormal pseudo-range value in the n pseudo-range residuals; Before step 1, the method further comprises: using the ionosphere-free combined pseudo-range of the B1C and B2a frequency points of the BDS satellite j, and the formula is as follows: wherein, is a dual-frequency ionosphere-free combination pseudorange measurement for satellite j; and are pseudorange measurements for satellite j at B1Cp and B2ap frequencies, respectively; GDB1Cp and GDB2ap are B1Cp and B2ap group delay errors, respectively, and are parsed from BDS B1C and B2a navigation messages; is a combination coefficient; after eliminating the ionosphere delay error, the station-satellite distance, satellite clock error, troposphere delay error, and relativistic error are eliminated to obtain the pseudo-range residual of the satellite j, and the formula is as follows: wherein ΔP j is the pseudo-range residual measurement value of satellite j; is the distance from the monitoring station to the satellite, wherein x nav , y nav and z nav are three-dimensional coordinates of the satellite in the ECEF coordinates solved from the navigation message, x site , y site , z site are three-dimensional coordinates of the monitoring station in the ECEF coordinate system; is the satellite clock error solved from the navigation message; is the relativistic error calculated from the model; is the tropospheric delay error calculated from the model; and c is the speed of light in vacuum.

2. The method for real-time pseudorange quality control of a Beidou satellite-based augmentation system according to claim 1, characterized in that, In step 2, the preset parameter is 5.

3. The method for real-time pseudorange quality control of a Beidou satellite-based augmentation system according to claim 1, characterized in that, In step 4, the variance of the double-frequency pseudo-range noise is 5.

4. An electronic device, comprising: The electronic device comprises a memory, a processor, and a computer program stored on the memory and executable on the processor, and the computer program is executed by the processor to implement the steps of the method for real-time pseudo-range quality control of the Beidou satellite-based augmentation system according to any one of claims 1 to 3.

5. A computer storage medium, the computer storage medium storing a computer program, the computer program being executed by a processor to implement the steps of the method for real-time pseudo-range quality control of the Beidou satellite-based augmentation system according to any one of claims 1 to 3.

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