A method for monitoring the integrity of satellite correction services

Abstract

The present invention discloses a method for monitoring the integrity of satellite correction services, which relates to the field of satellite positioning and navigation technology. The method comprises: obtaining the position of the satellite at the current time i and the correction parameter group p of the clock i k , calculate the position and clock error s sat,i ; Get the correction parameter group p at the current time i i k Extrapolated values ​​#imgabs0# calculate position and clock error s sat,i Extrapolated value #imgabs1# calculates the error vector δs sat,i , the error vector δs sat,i Substitute the test statistic calculation formula to obtain the test statistic d, and modify the parameter group p i k The test threshold value T is calculated based on the Gaussian statistical distribution characteristics of the inter-day deviation; the test statistic d is compared with the test threshold value T, and the integrity of the correction service is tested based on the comparison result. The present invention tests the integrity of the correction service by calculating the test statistic d and the test threshold value T, and comparing the two. In this process, there is no need to establish auxiliary measurement information of monitoring stations, so that the real-time correction service of precision satellite clocks and orbits can meet the requirements of integrity risk and continuity risk under boundary constraints.

Description

Technical Field

[0001] The present invention relates to the field of satellite positioning and navigation technology, and in particular to a method for monitoring the integrity of satellite correction services. Background Art

[0002] Precise Point Positioning (PPP) provides a cost-effective solution for high-precision global positioning by utilizing precise satellite orbit and clock corrections and incorporating precise corrections into various error models. The reliability of real-time PPP relies on the quality of the precise satellite clock and orbit correction products broadcast by the service. Therefore, to meet the navigation performance requirements of such applications, it is crucial to establish an integrity monitoring system for the real-time correction service to ensure the high accuracy and reliability of user positioning results.

[0003] To accurately monitor the quality of precision satellite orbit correction products, existing systems primarily monitor their integrity in the measurement domain. This involves verifying carrier phase residuals at multiple monitoring stations to ensure the reliability of RTX real-time correction products. This involves a two-step integrity monitoring process: pre-broadcast and post-broadcast. This process detects and flags correction information that exceeds limits, providing prompt alerts to users.

[0004] The defects of the above-mentioned existing technology are: using the measurement domain monitoring method to monitor the integrity of the modified product requires the use of multiple monitoring stations to form a monitoring network, the implementation process is complicated, and it is easy to introduce additional integrity risk sources, resulting in increased integrity risks. Summary of the Invention

[0005] Based on this, it is necessary to provide a method for monitoring the integrity of satellite correction services in response to the above technical issues.

[0006] An embodiment of the present invention provides a method for monitoring the integrity of a satellite correction service, comprising:

[0007] Get the satellite's current position i and clock correction parameter group p i k , the modified parameter group p i k Substitute into the satellite clock orbit calculation formula to obtain the position and clock error s sat,i ;

[0008] Get the correction parameter group p at the current time i i k Extrapolated value The modified parameter group p i k Extrapolated value Substitute into the satellite clock orbit calculation formula to calculate the position and clock error ssat,i Extrapolated value

[0009] The error s between the current position i and the clock sat,i Error s from position and clock sat,i Extrapolated value The error vector δs is obtained by subtraction sat,i , the error vector δs sat,i Substitute into the test statistic calculation formula to obtain the test statistic d;

[0010] By modifying the parameter set p i k The Gaussian statistical distribution characteristics of the day-to-day deviation are used to calculate the test threshold value T;

[0011] The test statistic d is compared with the test threshold value T, and the integrity of the satellite correction service is tested based on the comparison result.

[0012] In addition, the satellite position and clock correction parameter group p i k for:

[0013]

[0014] Among them, δO r ,δO a ,δO c 、 are the correction parameters and change rates of the radial, tangential and normal positions respectively; C0, C1 and C2 are the clock error correction number, clock speed correction number and clock rate correction number respectively.

[0015] In addition, the position and clock error s sat,i for;

[0016]

[0017] Among them, X orbit is the satellite position vector in the earth-fixed coordinate system after satellite orbit correction, Clk is the satellite clock error after clock error correction, T is the transpose, and sat is the satellite number.

[0018] In addition, the satellite position vector X orbit for:

[0019]

[0020] Among them, X broadcast is the satellite position vector in the Earth-centered Earth-fixed coordinate system calculated from the broadcast ephemeris parameters, δX is the satellite position correction vector in the Earth-fixed coordinate system, and e r 、e a、e c are radial, tangential, and normal direction vectors respectively, t is the current epoch time, and t0 is the reference time for the correction parameters;

[0021] The satellite clock error Clk is:

[0022]

[0023] Among them, Clk broadcast is the satellite clock error calculated from the broadcast ephemeris, and δC is the clock error correction calculated from the precise clock error correction information.

[0024] In addition, the extrapolated value of the correction parameter group at the current time i Equal to the correction parameter group p at the same time of the previous day i k-1 .

[0025] In addition, the test statistic calculation formula is:

[0026]

[0027] Among them, s sat,i are satellite position and clock errors, is the extrapolated value of satellite position and clock error, δs sat,i is the error vector, Q δs is the covariance matrix, d is the test statistic, and K is the ideal inflation factor.

[0028] In addition, the calculation test threshold value T is:

[0029]

[0030] Among them, v is the degree of freedom, t is the threshold variable, Γ is the gamma function, T is the test threshold, P ffa The false alarm rate requirement of the server.

[0031] In addition, the comparing the test statistic d with the test threshold value T and detecting the corrected service integrity according to the comparison result includes:

[0032] If the test statistic d is greater than the test threshold T, an alarm is issued and the current moment correction service integrity anomaly is marked;

[0033] If the test statistic d is less than the test threshold value T, the current minimum detectable deviation MDE is calculated, and the alarm limit AL is obtained by analyzing the minimum detectable deviation MDE of the long-term historical prior parameters;

[0034] Compare the minimum detectable deviation MDE with the alarm limit AL: if the current minimum detectable deviation MDE is less than the alarm limit AL, the test passes;

[0035] If the current minimum detectable deviation MDE is greater than the alarm limit AL, an alarm is issued and the current moment of correction of service integrity anomaly is marked.

[0036] In addition, the current minimum detectable deviation MDE is calculated as:

[0037]

[0038] Where λ is the noncentral parameter of the noncentral chi-square distribution under the fault hypothesis, P md is the missed detection rate requirement of the server, MDE is the current minimum detectable deviation, and T is the detection threshold.

[0039] The above-mentioned satellite correction service integrity monitoring method provided by the embodiment of the present invention has the following beneficial effects compared with the prior art:

[0040] The satellite's current position and clock error s at time i sat,i Its extrapolated value The error vector δs is obtained by subtraction sat,i , the error vector δs sat,i Substitute the test statistic calculation formula to obtain the test statistic d, and modify the parameter group p i k Calculate the test threshold value based on the Gaussian statistical distribution characteristics of the day-to-day deviation T , the test statistic d is compared with the test threshold value T, and the correction of the precise satellite clock orbit is monitored for anomalies based on the comparison results; in this process, only historical prior parameters need to be obtained, and there is no need to establish auxiliary measurement information of monitoring stations, so that the precise satellite clock orbit real-time correction service can meet the needs of integrity risk and continuity risk at the same time under boundary constraints. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The present invention is a flowchart of a method for monitoring the integrity of satellite correction services provided in one embodiment. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0043] In one embodiment, a method for monitoring the integrity of a satellite correction service is provided, such as Figure 1 As shown, the method includes:

[0044] Step 1: Based on the historical database, obtain the prior Beidou precise satellite orbit and clock correction parameter set p at the same time i on the previous day i k-1 , that is, the extrapolated value of the BeiDou precise satellite orbit and clock correction parameter group at the current time i

[0045] Step 2: The data processing server receives the position and clock correction parameter group p of the Beidou precision satellite i at the current moment i k . Precision satellite position and clock correction parameter group p i k for:

[0046]

[0047] Among them, δO r ,δO a ,δO c 、 are the correction parameters and change rates in the radial, tangential and normal directions respectively; C0, C1 and C2 are the clock error correction number, clock speed correction number and clock rate correction number respectively.

[0048] Step 3: Use the position and clock correction parameters of BeiDou precision satellites to set the parameter group p. i k , calculate the current Beidou precision satellite position and clock error s sat,i . Position and clock errors s sat,i for:

[0049]

[0050] Among them, X orbit is the satellite position vector in the earth-fixed coordinate system after precise satellite orbit correction, Clk is the satellite clock error after precise clock error correction, and sat is the corresponding satellite number.

[0051] Satellite position vector X orbit for:

[0052]

[0053] Among them, X broadcast is the satellite position vector in the Earth-centered Earth-fixed coordinate system calculated from the broadcast ephemeris parameters, δX is the satellite position correction vector in the Earth-fixed coordinate system, and e r 、e a 、e c are radial, tangential, and normal direction vectors respectively, t is the current epoch time, and t0 is the reference time for the correction parameters;

[0054] The satellite clock error Clk is:

[0055]

[0056] Among them, Clk broadcast is the satellite clock error calculated from the broadcast ephemeris, and δC is the clock error correction calculated from the precise clock error correction information.

[0057] The error vector, covariance matrix and test statistic construction method are specifically expressed as:

[0058]

[0059] Among them, s sat,i is the BeiDou precise satellite position and clock error, is the extrapolated value of BeiDou precise satellite position and clock error, δs sat,i is the error vector, Q δs is the covariance matrix, and d is the test statistic.

[0060] Step 4: Use the modified parameter group p i k Extrapolated value Calculate the position and clock error s of Beidou precision satellite sat,i Extrapolated value

[0061] Step 5: Use the current Beidou precise satellite position and clock error s sat,i With extrapolated value The error vector δs is obtained by subtraction sat,i , through the sliding window method, combined with the historical error vector to obtain the error covariance matrix Q δs , the test statistic d is calculated according to the formula.

[0062] The test statistic calculation formula is:

[0063]

[0064] Among them, s sat,i are satellite position and clock errors, is the extrapolated value of satellite position and clock error, δs sat,i is the error vector, Q δs is the covariance matrix, d is the test statistic, and K is the ideal inflation factor.

[0065] Since the test statistic does not completely obey the chi-square distribution with four degrees of freedom, non-ideal compensation is required to avoid this situation. The CDF envelope of the actual non-ideal distribution is formed, which can be described as:

[0066]

[0067] Where, To establish the CDF boundary of the standard chi-square distribution, is the actual detection statistic CDF distribution, and then determines the expansion factor K of the original covariance matrix.

[0068] Step 6: Based on the Gaussian statistical distribution characteristics of the inter-day deviation of the Beidou precision satellite orbit and clock correction parameter group and the false alarm rate requirements of the server, the inspection threshold value T is calculated.

[0069] The specific method for calculating the inspection threshold value is:

[0070]

[0071] Among them, v is the degree of freedom, t is the threshold variable, Γ is the gamma function, T is the test threshold, P ffa The false alarm rate requirement of the server.

[0072] Step 7: Perform integrity check by comparing the test statistic d with the test threshold value T. If the test passes, proceed to step 8. If not, issue an alarm and mark the integrity of the current correction service as abnormal.

[0073] Step 8, based on the covariance matrix Q δs , combined with the missed detection rate requirement of the server, the minimum detectable error MDE of the current integrity monitoring system is calculated.

[0074] The calculation method of the minimum detectable error is as follows:

[0075]

[0076] Where λ is the noncentral parameter of the noncentral chi-square distribution, P md is the missed detection rate requirement of the server, MDE is the current minimum detectable deviation, and T is the detection threshold. The alarm limit AL is obtained by analyzing the MDE value of long-term historical prior data.

[0077] Step 9: Compare the minimum detectable error MDE with the alarm limit AL. If the MDE exceeds the constraint of the alarm limit AL, an alarm is issued and the integrity of the current correction service is marked as abnormal. Otherwise, it indicates that the current correction service is available, passes the integrity monitoring, and updates the historical database.

[0078] On the one hand, the present invention uses historical prior Beidou precision satellite clock and orbit corrections to construct a test statistic that reflects the accuracy of real-time correction services. Combining the statistical distribution characteristics of the inter-day deviations of Beidou precision satellite clock and orbit corrections and the missed detection rate requirements of the server, a test threshold is obtained. By comparing the test statistic with the test threshold, anomalies of the satellite real-time clock and orbit corrections that have not yet been broadcast are monitored. On the other hand, based on the covariance of the prior Beidou precision satellite clock and orbit corrections, the minimum detectable error of the current integrity monitoring method is obtained. By comparing the minimum detectable error with the alarm limit related to the integrity risk requirements of the server, the purpose of integrity monitoring of the PPP server is achieved.

[0079] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for monitoring the integrity of satellite correction services, characterized in that: include: Get the satellite's current position i and clock correction parameter group p i k , the modified parameter group p i k Substitute into the satellite clock orbit calculation formula to obtain the position and clock error s sat,i ; Get the correction parameter group p at the current time i i k Extrapolated value of The modified parameter group p i k Extrapolated value Substitute into the satellite clock orbit calculation formula to calculate the position and clock error s sat,i Extrapolated value of The error s between the current position i and the clock sat,i Error s from position and clock sat,i Extrapolated value of The error vector δs is obtained by subtraction sat,i , the error vector δs sat,i Substitute into the test statistic calculation formula to obtain the test statistic d; By modifying the parameter set p i k The Gaussian statistical distribution characteristics of the day-to-day deviation are used to calculate the test threshold value T; Comparing the test statistic d with the test threshold value T, and testing the integrity of the satellite correction service based on the comparison result; Among them, the satellite position and clock correction parameter group p i k for: Among them, δO r ,δO a ,δO c 、 are the correction parameters and change rates of the radial, tangential and normal positions respectively; C0, C1 and C2 are the clock error correction number, clock speed correction number and clock speed correction number respectively; The position and clock error s sat,i for: Among them, X orbit is the satellite position vector in the earth-fixed coordinate system after satellite orbit correction, Clk is the satellite clock error after clock error correction, T is the transpose, and sat is the satellite number; The satellite position vector X orbit for: Among them, X broadcast is the satellite position vector in the Earth-centered Earth-fixed coordinate system calculated from the broadcast ephemeris parameters, δX is the satellite position correction vector in the Earth-fixed coordinate system, and e r 、e a 、e c are radial, tangential, and normal direction vectors respectively, t is the current epoch time, and t0 is the reference time for the correction parameters; The satellite clock error Clk is: Among them, Clk broadcast is the satellite clock error calculated from the broadcast ephemeris, and δC is the clock error correction calculated from the precise clock error correction information.

2. The method for monitoring the integrity of satellite correction services according to claim 1, wherein: Extrapolated value of the correction parameter group at the current time i Equal to the correction parameter group p at the same time of the previous day i k-1 .

3. The method for monitoring the integrity of satellite correction services according to claim 1, wherein: The test statistic calculation formula is: Among them, s sat,i are satellite position and clock errors, is the extrapolated value of satellite position and clock error, δs sat,i is the error vector, Q δs is the covariance matrix, d is the test statistic, and K is the ideal inflation factor.

4. The method for monitoring the integrity of satellite correction services according to claim 1, wherein: The calculation test threshold value T is: Among them, v is the degree of freedom, t is the threshold variable, Γ is the gamma function, T is the test threshold, P ffa The false alarm rate requirement of the server.

5. The method for monitoring the integrity of satellite correction services according to claim 1, wherein: Comparing the test statistic d with the test threshold value T and detecting the integrity of the modified service according to the comparison result includes: If the test statistic d is greater than the test threshold T, an alarm is issued and the current moment correction service integrity anomaly is marked; If the test statistic d is less than the test threshold value T, the current minimum detectable deviation MDE is calculated, and the alarm limit AL is obtained by analyzing the minimum detectable deviation MDE of the long-term historical prior parameters; Compare the minimum detectable deviation MDE with the alarm limit AL: if the current minimum detectable deviation MDE is less than the alarm limit AL, the test passes; If the current minimum detectable deviation MDE is greater than the alarm limit AL, an alarm is issued and the current moment of correction of service integrity anomaly is marked.

6. The method for monitoring the integrity of satellite correction services according to claim 5, wherein: The calculation of the current minimum detectable deviation MDE is: Where λ is the noncentral parameter of the noncentral chi-square distribution, P md is the missed detection rate requirement of the server, MDE is the current minimum detectable deviation, and T is the detection threshold.

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