An IGGⅢ robustness method for low-cost GNSS receivers with fixed ambiguity

Abstract

The present invention is an IGGⅢ anti-error method suitable for low-cost GNSS receivers with fixed ambiguity, comprising the following steps: analyzing the quality of observations through post-verification residuals, setting post-verification residual thresholds for pseudorange and carrier phases; preliminarily screening the observations through the thresholds, subjecting the maximum value of the post-verification residuals of the current epoch after each filtering iteration to equivalent weight processing by the IGGⅢ anti-error method, determining the post-verification residuals of the pseudorange, determining the post-verification normalized residuals of the carrier, until the total number of filtering iterations reaches N, and outputting the anti-error observations. The present invention effectively solves the problems of multiple iterations leading to filter divergence, difficulty in fixing ambiguity, and reinitialization leading to poor positioning accuracy. When the ambiguity of a low-cost GNSS receiver is fixed, the use of this anti-error model method can provide positioning reliability and stability, and provides a set of complete and feasible algorithm basis for high-precision positioning of low-cost GNSS receivers.

Description

Technical Field

[0001] The invention belongs to the technical field of GNSS satellite navigation and positioning, and in particular relates to an IGGIII anti-error method suitable for fixing ambiguity of a low-cost GNSS receiver. Background Art

[0002] With the development of satellite navigation and positioning technology, the global satellite navigation and positioning system is gradually becoming popular. Traditional geodetic receivers are expensive and have strict usage scenarios, so they cannot provide positioning services to the public. Low-cost GNSS receivers are small in size and low in cost and are widely used in wearable devices, shared bicycles and vehicle equipment. Considering the increasing use of smart wearable devices and mobile phones, the mass market has an increasingly strong demand for the accuracy of low-cost GNSS receivers in positioning and timing.

[0003] Due to the limitations of low-cost, low-power signal receiving units and processing algorithms, the positioning results output by low-cost GNSS receivers on the current mass market can only be accurate to ten meters or even tens of meters. Traditional GNSS positioning algorithms are concentrated in two major areas: RTK and PPP.

[0004] In Chinese patent CN116203603A (published on June 2, 2023), a low-cost PPP random model adaptive adjustment method for complex environments is disclosed, which relates to the field of satellite navigation and positioning technology. In the prior art, PPP positioning only requires a single receiver for positioning, and has been widely used in recent years. However, in the actual application of low-cost GNSS receiver PPP, there are problems such as poor observation data quality and difficulty in fixing ambiguity; and the RTK positioning mode requires observation station data for double difference positioning, so the use scenario is very limited.

[0005] Compared with geodetic receivers, low-cost GNSS receivers are equipped with low-cost hardware and complex application environments that reduce the quality of observation data. Positioning is greatly affected by non-line-of-sight errors and multipath errors of satellite signals, and the carrier movement speed varies during navigation, which brings more difficulties to building a suitable motion model. Therefore, in view of the widespread demand for low-cost receiver GNSS positioning terminals, their own defects and the particularity of the use environment, in the case of being unable to change the hardware performance, the PPP ambiguity of low-cost GNSS receivers is difficult to fix and repeatedly converge. At present, the main methods are divided into two types: external hardware assistance and anti-error processing. External assistance mostly uses low-cost INS assistance and inertial information assistance to fix the PPP ambiguity of low-cost GNSS receivers. Although this method can achieve PPP ambiguity in various complex environments, there is error accumulation in INS assistance and the algorithm implementation is relatively complex. Summary of the invention

[0006] In view of the above problems, the present invention proposes an IGGⅢ anti-error method suitable for low-cost GNSS receiver ambiguity fixation.

[0007] An IGGⅢ anti-error method for low-cost GNSS receiver ambiguity fixation includes the following steps:

[0008] Step S1: Analyze the quality of the observation value through the post-verification residual, and set the post-verification residual threshold of the pseudorange and carrier phase according to the post-verification residual;

[0009] Step S2: Preliminary screening of observations is performed using the threshold in step S1, and observations exceeding the threshold will not be included in the PPP solution;

[0010] Step S3: After the first screening of the posterior residuals, the maximum value of the posterior residual of the current epoch after each filtering iteration is subjected to equivalent weight processing of the IGG III robustness method. At the same time, in order to prevent the filter from diverging, the number of iterations is selected as N times. The specific value of N can be dynamically selected according to the observation conditions and data quality. The recommended selection interval is 3 to 10.

[0011] Step S4: Determine the pseudo-range post-verification residual. If the pseudo-range post-verification standardized residual falls into the reduced weight domain, check whether there is a cycle slip in the carrier phase of this satellite in this epoch; if so, reset the integer ambiguity of this satellite; if not, perform equivalent weight processing on the pseudo-range observation value, and this satellite does not participate in the fixed solution in this epoch; Determine the pseudo-range post-verification residual. If the pseudo-range post-verification standardized residual falls into the rejection domain, reset the integer ambiguity of this satellite; if not, accept the ambiguity parameter value estimated in the current epoch;

[0012] Step S5: The carrier phase observation standardized residual is judged. When it falls into the de-weighted domain or the rejection domain, the satellite does not participate in the fixed solution; if the standardized residual falls into the de-weighted domain, the satellite carrier observation value is processed with equivalent weights; if the standardized residual falls into the rejection domain, the integer ambiguity of the satellite is reset; if the carrier phase observation value falls into the de-weighted domain or the rejection domain for two consecutive epochs, the satellite ambiguity parameters are reset, and the satellite does not participate in the positioning solution in the current epoch;

[0013] Step S6: Repeat steps S2 to S5 until the total number of filtering iterations reaches N, and output the observation value after anti-error.

[0014] Preferably, in step S1, the observation value quality is analyzed by analyzing the posterior-verification residual of one iteration of Kalman filtering, and the pseudorange and carrier phase posterior-verification residual thresholds are set according to the posterior-verification residual of one iteration.

[0015] Preferably, in step S3, after the first screening of the posterior residuals, the maximum posterior residual of the current epoch after each filtering iteration is subjected to IGGⅢ equivalent weight processing to prevent filter divergence, and the number of iterations is selected as N times. The specific value of N can be dynamically selected according to the observation conditions and data quality, and the recommended selection interval is 3 to 10.

[0016] Preferably, the IGGIII robustness method in step S3 is to select a suitable estimation method when the observed gross error exists and cannot be avoided, to weaken or even eliminate the influence of the gross error on the parameter estimation value as much as possible, and to adopt equivalent weight processing for the available information; the classical IGGIII weight function is expressed as follows:

[0017] ,

[0018] in, For the observed quantity Corresponding weights: For GNSS observations, the initial weights of the pseudorange and carrier of each satellite are 1. , is the harmonic coefficient constant. Generally speaking, Take 1.0~1.5, Take 2.5~3.0; is the initial residual value; is the standardized residual, ;in is the unit weight variance factor calculated from the median, , where median is the function of taking the median.

[0019] Preferably, in step S3, IGGⅢ anti-ambiguity adopts the observation value quality and the posterior residual information, adjusts the usage scenarios of different types of observation values, and sets the number of Kalman filter iterations so that the iteration-induced filter divergence and ambiguity are fixed.

[0020] Preferably, in step S4, the standardized residual after pseudorange verification is judged, and when it falls into the reduced weight domain, it is checked whether there is a cycle slip in the carrier phase of this satellite in this epoch; if so, the integer ambiguity of the satellite is reset, and neither the floating point solution nor the fixed solution of this epoch uses any observation value of this satellite; if not, the pseudorange observation value is processed with equivalent weights, and the satellite in this epoch does not participate in the fixed solution.

[0021] Preferably, in step S4, the standardized residual after pseudorange verification is judged. If it falls into the rejection domain, the integer ambiguity of the satellite is reset, and neither the floating point solution nor the fixed solution of the epoch uses any observation value of this satellite; if it does not fall into the rejection domain, the ambiguity parameter value estimated by the current epoch is accepted.

[0022] Preferably, in step S5, the carrier post-verification standardized residual is judged, and when it falls into the down-weighting domain or the rejection domain, the satellite does not participate in the fixed solution; if the standardized residual falls into the down-weighting domain, the satellite carrier observation value is processed with equivalent weights; if the standardized residual falls into the rejection domain, the integer ambiguity of the satellite is reset; and neither the epoch floating point solution nor the fixed solution uses any observation value of this satellite.

[0023] Preferably, in step S5, if the carrier phase observation value falls into the down-weighting domain or the rejection domain for two consecutive epochs, it is considered that there is a gross error in the satellite carrier observation value, and its ambiguity parameter is reset, and the satellite does not participate in the positioning solution in the current epoch.

[0024] Preferably, in step S6, steps S2 to S5 are repeated until the total number of filtering iterations reaches N times. If the maximum number of iterations N is not reached, return to step S2, start a new round of initial screening and processing, and continue to perform multiple rounds of iterative screening and anti-error processing on the observation values; if the maximum number of iterations N is reached, the loop is terminated, and the PPP ambiguity fixation of the low-cost GNSS receiver is achieved by outputting the anti-error observation values ​​through the improved anti-error model.

[0025] With respect to the prior art, the technical solution of this application has the following advantages and effects:

[0026] 1. The present invention utilizes an anti-error processing method to select an ambiguity fixed subset and performs anti-error processing of different methods considering the satellite geometric space configuration and the original observation data, which can effectively improve the PPP ambiguity fixation rate and positioning accuracy of low-cost GNSS receivers.

[0027] 2. The improved IGGⅢ robust ambiguity of the present invention takes into account both the quality of observation values ​​and the posterior residual information, adjusts the usage scenarios of different types of observation values, sets the number of Kalman filter iterations, and effectively solves the problems of filter divergence caused by multiple iterations, difficulty in fixing ambiguity, and deterioration of positioning accuracy caused by reinitialization. When the PPP ambiguity of a low-cost GNSS receiver is fixed, this robust model method can provide positioning reliability and stability, providing a complete and feasible algorithm basis for high-precision positioning of low-cost GNSS receivers.

[0028] 3. The present invention verifies the quality of observations iteratively and applies equivalent weight processing, and can dynamically process and correct observations in real-time PPP solution, thereby improving the adaptability and real-time performance of real-time data.

[0029] 4. The present invention screens and processes the post-test residuals multiple times, and efficiently removes and resets the observations with cycle slips or gross errors, thereby enhancing the fault tolerance and robustness of the PPP solution and reducing the solution errors caused by abnormal data.

[0030] 5. The present invention can downgrade or reject abnormal data according to the post-test standardized residuals of the carrier and pseudorange observation values, effectively reducing the interference of abnormal data on PPP solution and improving the accuracy and reliability of the solution.

[0031] 6. The present invention sets the number of iterations and the threshold of the observation value, and combines the detection and processing of cycle slips. This method can dynamically adjust the processing strategy according to different data situations and has a certain degree of adaptability.

[0032] 7. The present invention can reduce the fixing problem of integer ambiguity caused by abnormal carrier phase observation values ​​by processing and resetting the carrier phase observation values, simplify the PPP-AR process, and improve the fixing success rate.

[0033] The above is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application so that it can be implemented in accordance with the contents of the specification, and to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following is a detailed description of the preferred embodiments of the present application in conjunction with the accompanying drawings as follows.

[0034] Based on the detailed description of the specific embodiments of the present application in combination with the accompanying drawings below, those skilled in the art will become more aware of the above and other objects, advantages and features of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings without creative work. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale.

[0036] Figure 1 It is a flowchart of the IGGⅢ anti-error method with fixed ambiguity for low-cost GNSS receivers; DETAILED DESCRIPTION

[0037] To make the purpose, technical scheme and advantages of the embodiment of the present application clearer, the technical scheme in the embodiment of the present application will be clearly and completely described below in conjunction with the drawings in the embodiment of the present application. Obviously, the described embodiment is a part of the embodiment of the present application, rather than all the embodiments. In the following description, specific details such as specific configurations and components are provided only to help fully understand the embodiments of the present application. Therefore, it should be clear to those skilled in the art that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. In addition, for clarity and brevity, the description of known functions and structures is omitted in the embodiment. It should be understood that "one embodiment" or "this embodiment" mentioned throughout the specification means that the specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, "one embodiment" or "this embodiment" appearing in various places throughout the specification may not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner.

[0038] In addition, the present application may repeat reference numerals and / or letters in different examples. This repetition is for the purpose of simplicity and clarity, and does not in itself indicate the relationship between the various embodiments and / or settings discussed.

[0039] The term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist at the same time. The term " / and" in this article describes another type of association relationship between associated objects, indicating that there can be two relationships. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0040] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusions. Example 1

[0041] This embodiment mainly introduces an IGGⅢ anti-error method suitable for low-cost GNSS receivers with fixed ambiguity, such as Figure 1 As shown;

[0042] An IGGⅢ anti-error method for low-cost GNSS receiver ambiguity fixation includes the following steps:

[0043] Step S1: Analyze the quality of the observation value through the post-verification residual, and set the post-verification residual threshold of the pseudorange and carrier phase according to the post-verification residual;

[0044] Step S2: Preliminary screening of observations is performed using the threshold in step S1, and observations exceeding the threshold will not be included in the PPP solution;

[0045] Step S3: After the first screening of the posterior residuals, the maximum value of the posterior residual of the current epoch after each filtering iteration is subjected to equivalent weight processing of the IGG III robustness method. At the same time, in order to prevent the filter from diverging, the number of iterations is selected as N times. The specific value of N can be dynamically selected according to the observation conditions and data quality. The recommended selection interval is 3 to 10.

[0046] Step S4: Determine the pseudo-range post-verification residual. If the pseudo-range post-verification standardized residual falls into the reduced weight domain, check whether there is a cycle slip in the carrier phase of this satellite in this epoch; if so, reset the integer ambiguity of this satellite; if not, perform equivalent weight processing on the pseudo-range observation value, and this satellite does not participate in the fixed solution in this epoch; Determine the pseudo-range post-verification residual. If the pseudo-range post-verification standardized residual falls into the rejection domain, reset the integer ambiguity of this satellite; if not, accept the ambiguity parameter value estimated in the current epoch;

[0047] Step S5: The carrier phase observation standardized residual is judged. When it falls into the de-weighted domain or the rejection domain, the satellite does not participate in the fixed solution; if the standardized residual falls into the de-weighted domain, the satellite carrier observation value is processed with equivalent weights; if the standardized residual falls into the rejection domain, the integer ambiguity of the satellite is reset; if the carrier phase observation value falls into the de-weighted domain or the rejection domain for two consecutive epochs, the satellite ambiguity parameters are reset, and the satellite does not participate in the positioning solution in the current epoch;

[0048] Step S6: Repeat steps S2 to S5 until the total number of filtering iterations reaches N, and output the observation value after anti-error.

[0049] Technical effect of this embodiment: This embodiment uses an anti-error processing method to select a fixed ambiguity subset and performs anti-error processing of different methods considering the satellite geometric space configuration and the original observation data, which can effectively improve the PPP ambiguity fixation rate and positioning accuracy of low-cost GNSS receivers. Example 2

[0050] This embodiment is based on the above-mentioned embodiment 1, and mainly introduces the implementation details of an IGGⅢ anti-error method suitable for low-cost GNSS receiver ambiguity fixation;

[0051] The quality of the analyzed observation value is analyzed by analyzing the posterior residual of one iteration of the Kalman filter;

[0052] The post-verification residual threshold of the pseudorange and carrier phase is set by iterating the post-verification residual;

[0053] After the first screening of the posterior residuals, the maximum value of the posterior residuals of the current epoch after each filtering iteration is subjected to IGGIII equivalent weight processing to prevent the filter from diverging, and the number of iterations is selected as N times;

[0054] The IGGⅢ robustness method is to select a suitable estimation method when the observation gross error exists and cannot be avoided, to weaken or even eliminate the influence of the gross error on the parameter estimation value as much as possible, and to adopt equivalent weight processing for the available information; the classic IGGⅢ weight function is expressed as follows:

[0055] ,

[0056] in, For the observed quantity Corresponding weights: For GNSS observations, the initial weights of the pseudorange and carrier of each satellite are 1. , is the harmonic coefficient constant. Generally speaking, Take 1.0~1.5, Take 2.5~3.0; is the initial residual value; is the standardized residual, ;in is the unit weight variance factor calculated from the median, , where median is the function of taking the median.

[0057] The IGGⅢ anti-ambiguity adopts the observation value quality and the post-test residual information, adjusts the usage scenarios of different types of observation values, and sets the number of Kalman filter iterations so that the filter divergence and ambiguity caused by the iterations are fixed.

[0058] The standardized residual after the pseudo-range verification is judged, and when it falls into the reduced weight domain, it is checked whether the carrier phase of the satellite in this epoch has a cycle slip; if it does, the integer ambiguity of the satellite is reset, and neither the floating point solution nor the fixed solution of this epoch uses any observation value of this satellite; if it does not exist, the pseudo-range observation value is processed with equivalent weights, and the satellite in this epoch does not participate in the fixed solution;

[0059] The standardized residual after pseudorange verification is judged. If it falls into the rejection domain, the integer ambiguity of the satellite is reset, and neither the floating point solution nor the fixed solution of this epoch uses any observation value of this satellite; if it does not fall into the rejection domain, the ambiguity parameter value estimated by the current epoch is accepted.

[0060] The carrier post-verification standardized residual is judged, and when it falls into the down-weighting domain or the rejection domain, the satellite does not participate in the fixed solution; if the standardized residual falls into the down-weighting domain, the satellite carrier observation value is processed with equivalent weights; if the standardized residual falls into the rejection domain, the integer ambiguity of the satellite is reset; and neither the epoch floating point solution nor the fixed solution uses any observation value of this satellite.

[0061] If the carrier phase observation value falls into the down-weighted domain or the rejection domain for two consecutive epochs, it is considered that there is a gross error in the satellite carrier observation value, and its ambiguity parameters are reset, and the satellite does not participate in the positioning solution in the current epoch.

[0062] Technical effect of this embodiment: The IGGⅢ anti-ambiguity of this embodiment takes into account both the quality of observation values ​​and the post-verification residual information, adjusts the usage scenarios of different types of observation values, and sets the number of Kalman filter iterations, effectively solving the problems of filter divergence caused by multiple iterations, difficulty in fixing ambiguity, and deterioration of positioning accuracy caused by reinitialization. Example 3

[0063] This embodiment is mainly based on Embodiment 1 and Embodiment 2, and mainly introduces a specific implementation method of the IGGⅢ anti-error method suitable for low-cost GNSS receiver ambiguity fixation;

[0064] The first step is to analyze the observation value quality by analyzing the Kalman filter iterative post-verification residual, and set the pseudorange and carrier phase post-verification residual thresholds according to the one-iteration post-verification residual;

[0065] In the second step, the observations are preliminarily screened, and the observations exceeding the threshold will not be included in the PPP solution;

[0066] In the third step, after the first screening of the posterior residuals, the maximum value of the posterior residuals of the current epoch after each filtering iteration is processed with IGGIII equivalent weights, and in order to prevent the filter from diverging, the number of iterations is selected as 8 times;

[0067] In the fourth step, if the standardized residual after the pseudo-range verification falls into the reduced weight domain, check whether there is a cycle slip in the carrier phase of the satellite in the epoch. If so, reset the integer ambiguity of the satellite, and neither the floating point solution nor the fixed solution of the epoch uses any observation value of the satellite; if not, perform equivalent weight processing on the pseudo-range observation value, and the satellite in this epoch does not participate in the fixed solution; if the standardized residual after the pseudo-range verification falls into the rejection domain, reset the integer ambiguity of the satellite, and neither the floating point solution nor the fixed solution of the epoch uses any observation value of the satellite;

[0068] The fifth step is to judge the carrier phase observation value. If the standardized residual after the carrier verification falls into the down-weighting domain or the rejection domain, the satellite does not participate in the fixed solution; if the standardized residual falls into the down-weighting domain, the satellite carrier observation value is processed with equivalent weights; if the standardized residual falls into the rejection domain, the integer ambiguity of the satellite is reset; and neither the epoch floating point solution nor the fixed solution uses any observation value of this satellite. If the carrier phase observation value falls into the down-weighting domain or the rejection domain for two consecutive epochs, the satellite ambiguity parameters are reset, and the satellite does not participate in the positioning solution in the current epoch;

[0069] In the sixth step, this process is repeated until the total number of filtering iterations reaches 8 times.

[0070] Technical effect of this embodiment: This embodiment can provide positioning reliability and stability by adopting this anti-error model method when the PPP ambiguity of the GNSS receiver is fixed, and provides a complete and feasible algorithm basis for high-precision positioning of low-cost GNSS receivers. Example 4

[0071] This embodiment is mainly based on Embodiment 1 and Embodiment 2, and is mainly a specific implementation method of the IGGⅢ anti-error method with fixed ambiguity for low-cost GNSS receivers;

[0072] The IGGⅢ robustness model method with fixed PPP ambiguity is applied in a low-cost GNSS receiver to improve the solution accuracy and reliability.

[0073] Step S1: setting the post-test residual threshold, in the process of Kalman filter solution, the quality of the observation value is analyzed by the post-test residual. For example, in a certain observation, the residual analysis after filtering is as follows:

[0074] The post-verification residuals of the pseudorange observations: [-3.5, 5.3, 4.6, -6.7, 7.8];

[0075] The carrier phase observation value post-validation residual: [0.15, -0.15, 0.16, -0.05, 0.2];

[0076] The residual thresholds of pseudorange and carrier phase are set according to these residuals, and are set to 8.0 and 0.2; pseudorange residual threshold = 8.0, carrier phase residual threshold = 0.2;

[0077] The step S2: preliminarily screens the observation values, and preliminarily screens the observation values ​​using the set residual threshold. The observation values ​​exceeding the threshold will not participate in the PPP solution. The specific screening process is as follows:

[0078] Table 1 Screening table

[0079] Observation Type Residual value Threshold result Pseudorange -8.2 8.0 give up Pseudorange 1.0 8.0 reserve Carrier Phase 0.25 0.2 give up Carrier Phase -0.15 0.2 reserve

[0080] Step S3: IGGⅢ anti-error processing and filtering iteration. After the initial screening, the remaining observations are subjected to the first IGGⅢ anti-error processing. After each filtering iteration, the maximum residual of the current epoch is subjected to equivalent weight processing. At the same time, in order to prevent the filter from diverging, the number of iterations is set to N=8 times.

[0081] The IGGⅢ anti-error weight function is as follows:

[0082] ,

[0083] in = 1.5, = 2.5, standardized residual Unit weight variance factor calculated from the median Calculated.

[0084] Step S4: judging the standardized residual after pseudo-range verification: if the standardized residual falls into the down-weighting domain, checking whether the carrier phase of the satellite at this epoch has a cycle slip; if there is a cycle slip, resetting the integer ambiguity of the satellite; if there is no cycle slip, performing equivalent weight processing on the pseudo-range observation value, and the satellite at this epoch does not participate in the fixed solution;

[0085] Table 2 Pseudorange normalized residual determination table

[0086] Satellite number Pseudorange normalized residual Judgment result A 2.3 Demotion processing, check cycle slip B 1.2 Normal processing, can be used for solving

[0087] Step S5: Determine the standardized residual after carrier verification: if the standardized residual falls into the down-weighting domain or the rejection domain, the satellite does not participate in the fixed solution; if it falls into the down-weighting domain, the carrier observation value is processed with equivalent weights; if it falls into the rejection domain, the integer ambiguity of the satellite is reset; if two consecutive epochs fall into the down-weighting or rejection domain, the ambiguity parameters are reset, and the satellite does not participate in PPP-AR in the current epoch.

[0088] Table 3 Carrier normalized residual determination table

[0089] Satellite number Carrier Normalized Residual Judgment result A 1.6 Downgrade processing, carrier does not participate in fixed solution B 2.7 Reset integer ambiguity and do not participate in the fixed solution

[0090] Step S6: Output the observation value after anti-error, and repeat steps S2 to S5 until the total number of filtering iterations reaches the set N. Through the improved IGGⅢ anti-error model, the final observation value after anti-error is output to achieve high-precision and low-cost PPP ambiguity fixation.

[0091] Technical effect of this embodiment: This embodiment applies detailed strategies to ensure the quality assessment of observation values, anti-error processing, and reliability and accuracy of the final output. In actual operation, specific parameters and thresholds are adjusted according to actual needs to adapt to different environments and application scenarios.

[0092] The above description is only the preferred embodiment of the present invention, which does not limit the protection scope of the present invention. For those skilled in the art, the present invention can be modified and varied in various ways. Within the spirit and principle of the present invention, any change, modification, replacement, integration and parameter change of these embodiments by conventional substitution or capable of achieving the same function without departing from the principle and spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. An IGGⅢ robustness method for low-cost GNSS receiver ambiguity fixation, characterized in that: The following steps are involved: Step S1: Analyze the quality of the observation value through the post-verification residual, and set the post-verification residual thresholds of the pseudorange and carrier phase; Step S2: Preliminary screening of observations is performed using the threshold in step S1, and observations exceeding the threshold will not be included in the PPP solution; Step S3: After the first screening of the posterior residuals, the maximum value of the posterior residual of the current epoch after each filtering iteration is subjected to equivalent weight processing of the IGGⅢ robustness method. At the same time, in order to prevent the filter from diverging, the number of iterations is selected as N times. The specific value of N is dynamically selected according to the observation conditions and data quality, and the selection interval is 3 to 10; Step S4: Determine the residual after the pseudo-range verification. If the normalized residual after the pseudo-range verification falls into the down-weighted domain, check whether there is a cycle slip in the carrier phase of this satellite at this epoch; if there is, reset the integer ambiguity of this satellite; if not, perform equivalent weight processing on the pseudo-range, and this satellite does not participate in the fixed solution at this epoch; The pseudo-range post-verification residual is judged. If the pseudo-range post-verification standardized residual falls into the rejection region, the integer ambiguity of the satellite is reset. If it does not fall into the rejection region, the ambiguity parameter value estimated at the current epoch is accepted. Step S5: Determine the carrier post-verification standardized residual. If it falls into the down-weighted domain or the rejection domain, the satellite does not participate in the fixed solution. If the standardized residual falls into the down-weighting domain, the satellite carrier observation value is treated with equivalent weights; if the standardized residual falls into the rejection domain, the integer ambiguity of the satellite is reset; If the carrier phase observation value falls into the down-weighted domain or rejection domain for two consecutive epochs, the satellite ambiguity parameters are reset, and the satellite does not participate in the positioning solution in the current epoch; Step S6: Repeat steps S2 to S5 until the total number of filtering iterations reaches N times, and output the observation value after robustness; The IGGIII robustness method in step S3 is to adopt equivalent weight processing for available information when the gross error of observation exists and cannot be avoided; the weight function of the IGGIII robustness method is expressed as follows: ， in, For the observed quantity Corresponding weights: For GNSS observations, the initial weights of the pseudorange and carrier of each satellite are 1. , is the harmonic coefficient constant, Take 1.0~1.5, Take 2.5~3.0; is the initial residual value; is the standardized residual, ;in is the unit weight variance factor calculated from the median, , where median is the function of taking the median; The IGGⅢ anti-error method in step S3 adopts the observation value quality and the posterior residual information, adjusts the usage scenarios of different types of observation values, and sets the number of Kalman filter iterations so that the filter divergence and ambiguity caused by the iterations are fixed.

2. The IGGIII robustness method for ambiguity fixation of low-cost GNSS receivers according to claim 1, characterized in that: In step S1, the observation quality is analyzed by analyzing the posterior residual of the Kalman filter iteration, and the pseudorange and carrier phase posterior residual thresholds are set according to the posterior residual of one iteration.

3. The IGGⅢ robustness method for fixing ambiguity of low-cost GNSS receivers according to claim 1, characterized in that: In step S4, the standardized residual after pseudorange verification is judged. When it falls into the down-weighted domain, check whether there is a cycle slip in the carrier phase of this satellite in this epoch; if so, reset the integer ambiguity of the satellite, and neither the floating point solution nor the fixed solution of this epoch uses any observation value of this satellite; if not, perform equivalent weight processing on the pseudorange, and the satellite in this epoch does not participate in the fixed solution.

4. The IGGIII robustness method for fixing ambiguity of low-cost GNSS receivers according to claim 1 or 3, characterized in that: In step S4, the standardized residual after pseudorange verification is judged. If it falls into the rejection domain, the integer ambiguity of the satellite is reset, and neither the floating point solution nor the fixed solution of this epoch uses any observation value of this satellite; if it does not fall into the rejection domain, the ambiguity parameter value estimated at the current epoch is accepted.

5. The IGGIII robustness method for ambiguity fixation of low-cost GNSS receivers according to claim 1, characterized in that: In step S5, the carrier post-verification standardized residual is judged, and when it falls into the down-weighted region or the rejection region, the satellite does not participate in the fixed solution; If the standardized residual falls into the down-weighting domain, the satellite carrier observation value is treated with equivalent weights; if the standardized residual falls into the rejection domain, the integer ambiguity of the satellite is reset; and neither the epoch floating point solution nor the fixed solution uses any observation value of this satellite.

6. The IGGIII robustness method for fixing ambiguity of low-cost GNSS receivers according to claim 1 or 5, characterized in that: In step S5, if the carrier phase observation value falls into the down-weighting domain or the rejection domain for two consecutive epochs, it is considered that there is a gross error in the satellite carrier observation value, and its ambiguity parameters are reset, and the satellite does not participate in the positioning solution in the current epoch.

7. The IGGIII robustness method for ambiguity fixation of low-cost GNSS receivers according to claim 1, characterized in that: In step S6, steps S2 to S5 are repeated until the total number of filtering iterations reaches N. If the maximum number of iterations N is not reached, return to step S2 to start a new round of preliminary screening and processing, and continue to perform multiple rounds of iterative screening and anti-error processing on the observations; If the maximum number of iterations N is reached, the loop is terminated, and the PPP ambiguity of the low-cost GNSS receiver is fixed by outputting the robust observation value through the improved robust model.

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