A multi-form code bias unified estimation and correction method

Abstract

The application discloses a multi-form code bias unified estimation and correction method, constructs a compatible and unified function model, can realize unified estimation of any type of code bias in OSB, DCB and IFCB, and can broadcast internally consistent code bias products based on the method; the user end can adopt different types of code bias products, convert satellite clock error correction values provided by satellite clock error products into satellite clock error correction values of a target frequency combination, and applies the converted correction values to ionosphere-free combinations of observation values to perform a precise point positioning process; the application can realize internal consistency of multi-form code bias estimation, and makes each form of code bias product unified and convenient for use in a terminal user positioning correction process, effectively improves the adaptability and practicality of precise point positioning.

Description

Technical Field

[0001] This invention belongs to the field of high-precision satellite navigation error correction technology, and in particular relates to a unified estimation and correction method for multi-form code deviation. Background Technology

[0002] Global Navigation Satellite Systems (GNSS) are a modern space infrastructure and a powerful tool for human navigation, positioning, and timing (PNT). With the operation of my country's BeiDou (BDS) system and Europe's Galileo system, and the modernization of GPS and GLONASS systems, navigation constellations, signal frequencies, and signal types have become increasingly diverse. Multi-frequency and multi-type observations generated by multiple GNSS systems have become a major characteristic and important trend of modern GNSS.

[0003] In GNSS applications, rigorous handling of various observation errors is a prerequisite for achieving high-precision multi-frequency applications. Hardware bias in pseudorange measurement, also known as code bias, refers to systematic deviations caused by hardware delays in both the satellite and receiver, ranging in value from a few nanoseconds to tens of nanoseconds. Handling code bias is crucial for achieving consistency in GNSS observation data across different frequencies. Correcting code bias can reduce systematic errors in observations, significantly impacting the convergence process of precise point positioning and improving its convergence speed and positioning accuracy. Therefore, how to accurately handle these code biases has become a research focus in the international GNSS field in recent years.

[0004] To adapt to different applications, various forms of code bias have been defined. Among them, differential code bias (DCB) refers to the time delay difference between different types of GNSS signals on different channels of the satellite and receiver. For a long time, DCB has been the most widely used form of code bias. Observational signal bias (OSB), also known as pseudo-absolute code bias, is defined for specific observations at each specific frequency. Inter-frequency clock bias (IFCB) is defined as the satellite inter-frequency clock bias calculated using observations from different frequency references; its pseudorange component (CIFCB) typically includes hardware delay factors from both the satellite and receiver. For these different representations, this paper studies a compatible and unified code bias estimation method that ensures internal consistency between the different forms of code bias provided to users by the server. Furthermore, it provides a unified correction method for multiple forms of code bias, making these different types of code bias more uniform and convenient for use in the end-user positioning correction process. This represents a new development requirement in the field of GNSS code bias.

[0005] The existing technology has at least the following problems: 1. Currently, research on code bias is relatively independent, with most studies estimating bias in a single form. The data processing for DCB, OSB, and IFCB estimations is independent of each other, and differences in estimation models, error handling strategies, and benchmark introduction can lead to inconsistencies in code bias products from different sources and with different forms.

[0006] 2. Currently, there is a lack of standardized code bias correction models in GNSS precise point positioning. In actual positioning processes, corrections for different types of code bias products (such as DCB, OSB, and pseudorange IFCB) are implemented at multiple stages, including the raw observation level, the observation equation error correction level, and the clock bias correction level. This prevents existing technologies from forming a unified code bias correction method using any of the aforementioned code bias products, and also makes the positioning correction process inconvenient for users. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a unified estimation and correction method for multi-form code deviation, which can achieve internal self-consistency in multi-form code deviation estimation and enable the unified and convenient use of various form code deviation products in the end-user positioning correction process.

[0008] To achieve the above objectives, this invention provides a unified estimation and correction method for multi-form code deviation, comprising: Server-side: Acquires raw observation files from the Global Navigation Satellite System; corrects for tropospheric delay, antenna phase center offset, tidal effects, and relativistic effects errors in the raw observations using empirical models; introduces external precise orbit products to correct satellite orbit errors and generates error-corrected observation equations; introduces precise satellite clock bias products and global ionospheric map products to correct satellite clock bias and ionospheric delay and introduces ionospheric residual errors; reorganizes the observation equations to estimate any type of code bias in OSB, DCB, and IFCB using a compatible and unified function model; adds code bias parameter constraints to eliminate rank deficiency; performs parameter estimation using the least squares method and outputs a set of internally consistent observation signal bias, differential code bias, and inter-frequency clock bias products. On the user side: Obtain the original observation files and establish the observation equations; correct the original observation values ​​for tropospheric delay, antenna phase center offset, tidal effects, and relativistic effects errors using an empirical model; introduce external precise orbit products to correct satellite orbit errors and generate the error-corrected observation equations; perform dual-frequency ionospheric combination on the original observation values; obtain precise satellite clock bias products; convert the satellite clock bias correction values ​​provided by the satellite clock bias products into satellite clock bias correction values ​​suitable for the target frequency combination according to the code bias product type; apply the corrected satellite clock bias correction values ​​and ionospheric combination observation values ​​to perform a precise single-point positioning process.

[0009] Optional, the error-corrected linearized observation equations include: ; in, It's satellite PRN. It is the receiver serial number. Representing frequency , It is the GNSS system number. This represents the linear residual before the test after error correction; and These are the residuals of GNSS pseudorange and phase linearity before verification after error correction at different frequencies. Indicates the receiver in inertial frames. r To satellite s The direction vector, This represents the receiver r-coordinate correction vector in the Earth-fixed system. and These are the receiver satellite clock bias and the system. Satellite clock bias, This refers to inter-system bias with reference to the GPS system; It is the delayed wet component of the troposphere; yes Ionospheric delay of frequency, coefficient It is to reduce the ionospheric slack delay from Mapped to The ionospheric dispersion coefficient, For any frequency; and These are the hardware delays in pseudorange observations at the satellite and receiver ends. and These are the phase deviations between the satellite and the receiver, respectively. Indicates carrier phase ambiguity; and It refers to the unmodeled errors in pseudorange and phase observations.

[0010] Optional, precision satellite clock bias products include: The satellite clock bias of each system will include the corresponding system reference frequency. , Code deviation in the following form: ; in, The reference frequency provided for precision satellite clock bias products , Satellite clock bias correction value; It is to reduce the ionospheric slack delay from Mapped to The ionospheric dispersion coefficient.

[0011] Optionally, residual ionospheric error estimation includes: The residual error of the global ionospheric map product is modeled as a random quantity with a mathematical expectation of zero and a variance of 3 meters, and is used as a random parameter in the recombined observation equations for solution. ; in, It is frequency Residual error of ionospheric delay; E The mathematical expectation of the residual error estimate for ionospheric delay; D The variance is the residual error estimate for ionospheric delay.

[0012] Optionally, the method is also compatible with a unified function model, including: Reorganize the observation equations and establish a function model: ; in, , These are the newly generated receiver clock bias and ambiguity parameters; , The estimation process incorporates code bias components, specifically in the following form: ; ; in, and This is the sum of the hardware delays of the reference frequencies at the receiver ends of each system; , ; These are the newly generated satellite and receiver endcode offset parameters. In the observation equation The coefficient; assigned Different forms of expression will The estimated deviation is due to different code formats, specifically: when ; ; At that time, It is estimated to be in OSB format; when ; ; At that time, It is estimated to be in DCB form; when ; ; At that time, It is estimated to be in IFCB form; in, For the system frequency The sum of code deviations at the satellite and receiver ends.

[0013] Optional, code offset parameter constraints include: When outputting products with arbitrary code deviations, the sum of the code deviations for all frequency-constrained satellite ends is zero: ; in, Total number of satellites; This is due to satellite code deviation; When outputting OSB products, an ionospheric-free combined constraint is applied to the code deviation at the reference frequency satellite end and receiver end: ; ; in, It is a system frequency satellite Code deviation parameter; It is a system frequency Receiver The code deviation parameter.

[0014] Optionally, correcting the clock bias product reference to the target frequency includes: If an OSB product is used, the clock bias correction method is as follows: ; If a DCB product is used, the clock error correction method is as follows: ; If a pseudorange IFCB product is used, the clock error correction method is as follows: ; in, , Two frequencies used for precise single-point positioning and ; The reference frequency provided for precision satellite clock bias products , The satellite clock bias correction value; For frequency , The satellite clock bias correction value is the baseline; coefficient It is to reduce the ionospheric slack delay from Mapped to The ionospheric dispersion coefficient, For any frequency; It is a system frequency satellite The code deviation parameter.

[0015] Technical advantages of this invention: This invention discloses a unified estimation and correction method for multiple forms of code bias, enabling different code bias products to have the same data processing procedure, estimation model, and error handling strategy, while avoiding inconsistencies between code bias products caused by differences in the reference standard. This achieves internal consistency among different forms of code bias. For three different forms of code bias—OSB, DCB, and IFCB—a unified correction is performed on GNSS clock bias products based on ionospheric-free combinations published by the IGS analysis center. This method can correct the clock bias reference, allowing clock biases published by various analysis centers based on specific frequency references to be easily converted into clock bias correction values ​​applicable to GNSS signals of any frequency. This invention constructs a rigorous and unified code bias estimation model, achieving internal consistency in the estimation of multiple forms of code bias, and enabling end users to complete clock bias correction in a unified and convenient manner using code bias products of any form, significantly lowering the barrier to entry and improving application efficiency. Attached Figure Description

[0016] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart illustrating the unified estimation and correction method for multi-form code deviation in an embodiment of the present invention. Detailed Implementation

[0017] 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.

[0018] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0019] like Figure 1 As shown, this embodiment provides a unified estimation and correction method for multi-form code deviation, including: Server-side: Acquires raw observation files from the Global Navigation Satellite System; corrects for tropospheric delay, antenna phase center offset, tidal effects, and relativistic effects errors in the raw observations using empirical models; introduces external precise orbit products to correct satellite orbit errors and generates error-corrected observation equations; introduces precise satellite clock bias products and global ionospheric map products to correct satellite clock bias and ionospheric delay and introduces ionospheric residual errors; reorganizes the observation equations to estimate any type of code bias in OSB, DCB, and IFCB using a compatible and unified function model; adds code bias parameter constraints to eliminate rank deficiency; performs parameter estimation using the least squares method and outputs a set of internally consistent observation signal bias, differential code bias, and inter-frequency clock bias products. On the user side: Obtain the original observation files and establish the observation equations; correct the original observation values ​​for tropospheric delay, antenna phase center offset, tidal effects, and relativistic effects errors using an empirical model; introduce external precise orbit products to correct satellite orbit errors and generate the error-corrected observation equations; perform dual-frequency ionospheric combination on the original observation values; obtain precise satellite clock bias products; convert the satellite clock bias correction values ​​provided by the satellite clock bias products into satellite clock bias correction values ​​suitable for the target frequency combination according to the code bias product type; apply the corrected satellite clock bias correction values ​​and ionospheric combination observation values ​​to perform a precise single-point positioning process.

[0020] Specifically, the unified estimation method for multi-form code bias includes the following steps: Step S1: Obtain the raw GNSS observation files.

[0021] Step S2: Calculate errors including tropospheric delay correction, antenna phase center correction, tidal effect correction, and relativistic effect correction using empirical models, and correct the original observation values ​​for errors.

[0022] Step S3: Introduce external precision orbit products to correct satellite orbit errors.

[0023] Step S4: After steps S2 and S3, establish the original observation equation for the linearized pre-analysis residuals after error correction: ; in, It's satellite PRN. It is the receiver serial number. Representing frequency , It is the GNSS system number, where Represents GPS, Represents BDS-3, Represents Galileo. This represents the linear residual before the test, after error correction. and These are the residuals of GNSS pseudorange and phase linearity before verification after error correction at different frequencies. Indicates the receiver in inertial frames. r To satellite s The direction vector, This represents the receiver r-coordinate correction vector in the Earth-fixed system. and These are the receiver and the satellite clock bias, It is the inter-system bias (ISB) with reference to the GPS system. It is the delayed wet component of the troposphere; yes Ionospheric delay of frequency, coefficient It is to reduce the ionospheric slack delay from Mapped to The ionospheric dispersion coefficient, For any frequency. and These are the hardware delays in pseudorange observations at the satellite and receiver ends. and These are the phase deviations between the satellite and the receiver, respectively. This indicates carrier phase ambiguity. and These are unmodeled errors in pseudorange and phase observations, including systematic errors, observation noise, and multipath errors.

[0024] Step S5: Introduce external precision clock products to correct orbital clock errors. Since the precision clock products for each system are generated through ionosphere-free (IF) combinations, the satellite clock bias of each system will include the corresponding system reference frequency. , Code deviation in the following form: ; in, The reference frequency provided for precision satellite clock bias products , The satellite clock error correction value.

[0025] Step S6: Introduce Global Ionospheric Map (GIM) products to account for ionospheric delay errors. Corrections were made and the residual error of the GIM product was estimated. Given that the correction accuracy of the GIM product is no greater than 8 TECU, i.e., within... The frequency introduces an error of no more than 3 m, which can reduce the residual error of the ionosphere. The estimated random quantity is a random variable with a mathematical expectation of 0 and a variance of 3m. ; in, It is frequency Residual error of ionospheric delay; E The mathematical expectation of the residual error estimate for ionospheric delay; D The variance is the residual error estimate for ionospheric delay.

[0026] Step S7: After error correction in S5 and S6, reorganize the observation equation in S4 to estimate the bias of any type of code in OSB, DCB, and IFCB using a compatible and unified function model. ; in, , These are the newly generated receiver clock bias and ambiguity parameters; , The estimation process incorporates code bias components, specifically in the following form: ; ; and This is the sum of the hardware delays of the reference frequencies at the receiver ends of each system. , . These are the newly generated satellite and receiver endcode offset parameters. In the observation equation The coefficient. Assigned Different forms of expression will The estimate is due to discrepancies in different code formats. Specifically: when ; ; At that time, It is estimated to be in OSB format; when ; ; At that time, It is estimated to be in DCB form; when ; ; At that time, It is estimated to be in IFCB form; in, For the system frequency The sum of code deviations at the satellite and receiver ends.

[0027] Step S8: Introduce a zero-mean reference to eliminate the rank deficiency for each frequency code deviation at the satellite end of each system, as follows, so that the code deviations at the satellite and receiver ends can be estimated respectively: ; in, Total number of satellites; This is due to satellite code deviation.

[0028] In particular, if the code offset is estimated in OSB form, an additional ionospheric constraint needs to be added to the code offset at the receiver and satellite ends so that the OSB at each frequency can be estimated separately.

[0029] ; ; in, It is a system frequency satellite Code deviation parameter; It is a system frequency Receiver The code deviation parameter.

[0030] Step S9: Parameter estimation is achieved through the least squares method, specifically including receiver coordinate correction, receiver clock error, tropospheric delay wet component, floating-point ambiguity parameter, code deviation between satellite and receiver, and ionospheric correction residual.

[0031] Using the above method, different parameter coefficients and constraints can be applied to achieve a unified estimation of the code deviation for any of the OSB, DCB, and IFCB forms in a one-step process. This yields a set of internally consistent code deviation parameters, which are then broadcast to the user. This completes the process of unified estimation of multi-form code deviations on the server side.

[0032] Specifically, the unified correction method for multi-form code deviation includes the following steps: Step S1: Obtain the raw GNSS observation files and establish the raw observation equations. Step S2: Calculate errors including tropospheric delay correction, antenna phase center correction, tidal effect correction, and relativistic effect correction using empirical models, and correct the original observation values ​​for errors.

[0033] Step S3: Introduce external precision orbit products to correct satellite orbit errors.

[0034] Step S4: After steps S2 and S3, establish the linear pre-analysis residual observation equation after error correction: ; The original observations were combined using a dual-frequency, ionosphere-free method to obtain the combined observations. The ionosphere-free operator is: ; Therefore, frequency , The non-ionized combination is as follows: ; in, and For frequency , The pseudorange and phase linearization residual observation equations after ionospheric integration.

[0035] Step S5: Obtain the clock bias reference as frequency. , Precision satellite clock products Its satellite clock bias correction includes frequency , Hardware latency components.

[0036] Step S6: Use the code deviation product to set the frequency as the reference. , Precision satellite clock products Convert to reference frequency , Satellite clock correction value .

[0037] If an OSB product is used, the conversion method is as follows: ; If a DCB product is used, the conversion method is as follows: ; If a pseudorange IFCB product is used, the conversion method is as follows: ; in, , Two frequencies used for precise single-point positioning and ; The reference frequency provided for precision satellite clock bias products , Satellite clock bias correction value; For frequency , The satellite clock bias correction value is the baseline; coefficient It is to reduce the ionospheric slack delay from Mapped to The ionospheric dispersion coefficient, For any frequency; It is a system frequency satellite The code deviation parameter.

[0038] Step S7: Obtain the parameter estimation equations after correction for each error term: ; in, This is the floating-point ambiguity estimate after ionospheric integration, which includes the phase hardware delay component. At this point, all parameters can be estimated, specifically including receiver coordinate corrections, receiver clock bias, tropospheric delay wet component, and floating-point ambiguity parameters.

[0039] Using the above method, any code bias product from OSB, DCB, or IFB can be introduced to correct satellite clock bias products and apply them to the user's precise positioning process. This method provides a unified user correction model applicable to different code bias types, enabling different forms of code bias to be applied to GNSS bias correction in a unified and convenient manner.

[0040] This invention discloses a unified estimation and correction method for multiple code bias forms, enabling different code bias products to have the same data processing procedure, estimation model, and error handling strategy, while avoiding inconsistencies between code bias products caused by differences in the reference standard. This achieves internal consistency among different code bias forms. For three different forms of code bias—OSB, DCB, and IFCB—the method uniformly corrects GNSS clock bias products based on ionospheric-free combinations published by the IGS analysis center. This method can correct the clock bias reference, allowing clock biases published by various analysis centers using specific frequency references to be easily converted into clock bias correction values ​​applicable to GNSS signals of any frequency. This invention achieves internal consistency in the estimation of multiple code bias forms and makes various code bias products uniformly and conveniently used in the end-user positioning correction process.

[0041] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A unified estimation and correction method for multi-form code deviation, characterized in that, include: Server-side: Retrieves raw observation files from the Global Navigation Satellite System; The system corrects for errors in tropospheric delay, antenna phase center offset, tidal effects, and relativistic effects in the original observations using an empirical model. It introduces external precise orbit products to correct satellite orbit errors and generate error-corrected observation equations. Precise satellite clock bias products and global ionospheric map products are introduced to correct satellite clock bias and ionospheric delay, and residual ionospheric errors are introduced. The observation equations are reorganized to estimate any type of code bias among the observed signal bias (OSB), differential code bias (DCB), and inter-frequency clock bias product (IFCB) using a compatible and unified function model. Code bias parameter constraints are added to eliminate rank deficiency. Parameter estimation is achieved using the least squares method, outputting a set of internally self-consistent observed signal bias (OSB), differential code bias (DCB), and inter-frequency clock bias product (IFCB). User-side: Acquire raw observation files and establish observation equations; correct tropospheric delay, antenna phase center offset, tidal effect, and relativistic effect errors in the raw observations using empirical models; introduce external precision orbit products to correct satellite orbit errors and generate error-corrected observation equations; perform dual-frequency ionospheric-free combination of raw observations; acquire precision satellite clock bias products; convert the satellite clock bias correction values ​​provided by the satellite clock bias products into satellite clock bias correction values ​​suitable for the target frequency combination according to the code bias product type; A precise point positioning process is performed using the corrected satellite clock bias values ​​and combined observations without an ionosphere. The compatible and unified function model includes: Reorganize the observation equations and establish a function model: ； in, and These are the residuals of GNSS pseudorange and phase linearity before verification after error correction at different frequencies. Receiver in inertial frame r To satellite s The direction vector, Let r be the correction vector of the receiver's r-coordinate in the Earth-fixed system. This refers to the inter-system bias with reference to the GPS system. For frequency The residual error of ionospheric delay For the system frequency The sum of code deviations at the satellite and receiver ends, , These are the newly generated receiver clock bias and ambiguity parameters; , The estimation process incorporates code bias components, specifically in the following form: ； ； in, and This is the sum of the hardware delays of the reference frequencies at the receiver ends of each system; , , In the observation equation The coefficient; assigned Different forms of expression will The estimated deviations are due to different code formats, specifically: when ; ; At that time, It is estimated to be in OSB format; when ; ; At that time, It is estimated to be in DCB form; when ; ; At that time, It is estimated to be in IFCB form; Code deviation parameter constraints include: When outputting products with arbitrary code deviations, the sum of the code deviations for all frequency-constrained satellite ends is zero: ； in, Total number of satellites; This is due to satellite code deviation; When outputting OSB products, an ionospheric-free combined constraint is applied to the code deviation at the reference frequency satellite end and receiver end: ； ； in, It is a system frequency satellite Code deviation parameter; It is a system frequency Receiver The code deviation parameter.

2. The method for unified estimation and correction of multi-form code deviation as described in claim 1, characterized in that, The linearized observation equations after error correction include: ； in, It's satellite PRN. It is the receiver serial number. Representing frequency , It is the GNSS system number. This represents the linear residual before the test after error correction; and These are the residuals of GNSS pseudorange and phase linearity before verification after error correction at different frequencies. Indicates the receiver in inertial frames. r To satellite s The direction vector, This represents the receiver r-coordinate correction vector in the Earth-fixed system. and These are the receiver satellite clock bias and the system. Satellite clock bias, This refers to inter-system bias with reference to the GPS system; yes Ionospheric delay of frequency, coefficient It is to reduce the ionospheric slack delay from Mapped to The ionospheric dispersion coefficient, For any frequency; and These are the hardware delays in pseudorange observations at the satellite and receiver ends. and These are the phase deviations between the satellite and the receiver, respectively. Indicates carrier phase ambiguity; and It refers to the unmodeled errors in pseudorange and phase observations.

3. The method for unified estimation and correction of multi-form code deviation as described in claim 1, characterized in that, Precision satellite clock bias products include: The satellite clock bias of each system will include the corresponding system reference frequency. , Code deviation in the following form: ； in, The reference frequency provided for precision satellite clock bias products , The satellite clock bias correction value; It is to reduce the ionospheric slack delay from Mapped to ionospheric dispersion coefficient; For the system Satellite clock bias.

4. The method for unified estimation and correction of multi-form code deviation as described in claim 1, characterized in that, Ionospheric residual error estimation includes: The residual error of the global ionospheric map product is modeled as a random quantity with a mathematical expectation of zero and a variance of 3 meters, and is used as a random parameter in the recombined observation equations for solution. ； in, It is frequency Residual error of ionospheric delay; E The mathematical expectation of the residual error estimate for ionospheric delay; D The variance is the residual error estimate for ionospheric delay.

5. The method for unified estimation and correction of multi-form code deviation as described in claim 1, characterized in that, Correcting the clock difference product benchmark to the target frequency includes: If an OSB product is used, the clock bias correction method is as follows: ； If a DCB product is used, the clock error correction method is as follows: ； If a pseudorange IFCB product is used, the clock error correction method is as follows: ； in, , Two frequencies used for precise single-point positioning and ; The reference frequency provided for precision satellite clock bias products , The satellite clock bias correction value; For frequency , The satellite clock bias correction value is the baseline; coefficient It is to reduce the ionospheric slack delay from Mapped to The ionospheric dispersion coefficient, For any frequency; It is a system frequency satellite The code deviation parameter.

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