Ambiguity fixing methods, devices, receivers, and storage media

Abstract

This application relates to the field of satellite navigation and positioning technology, and provides a method, apparatus, receiver, and storage medium for ambiguity fixing. First, the ambiguity candidate subset is fixed using the LAMBDA algorithm to obtain the ambiguity fixing result. If the ambiguity fixing result meets preset conditions, the ambiguity fixing is determined to be correct, and the final ambiguity fixing solution is output. If the ambiguity fixing result does not meet the preset conditions, the ambiguity fixing is determined to be incorrect. Incorrectly fixed observations are identified and removed from the ambiguity candidate subset. Then, the LAMBDA algorithm is used again to fix the ambiguity candidate subset until the ambiguity is correctly fixed. This improves the accuracy of ambiguity fixing to meet the requirements of high-precision GNSS positioning.

Description

Technical Field

[0001] This application relates to the field of satellite navigation and positioning technology, and more specifically, to an ambiguity fixing method, apparatus, receiver, and storage medium. Background Technology

[0002] GNSS (Global Navigation Satellite System) is an all-weather, global, high-precision radio navigation technology that can obtain absolute position coordinates at any time and any location. It can be applied to surveying and mapping, autonomous driving, and other fields. With the development of the autonomous driving industry, higher demands are being placed on the real-time performance, positioning accuracy, continuity, and reliability of GNSS positioning.

[0003] GNSS observation data mainly includes carrier phase observations, pseudorange observations, Doppler observations, and carrier-to-noise ratio (CNR) data. Pseudorange observations have accuracy at the meter or even decimeter level, Doppler observations can achieve decimeter-level velocity measurement accuracy, and phase observations can reach millimeter-level accuracy. However, phase observations contain integer ambiguity, which must be treated as an unknown in filter calculations. Furthermore, an ambiguity fixing method is needed to fix it to integers to achieve centimeter-level or even millimeter-level accuracy in positioning results. Incorrect ambiguity fixing will lead to large errors in the fixed solution; if ambiguity cannot be fixed, centimeter-level positioning accuracy is difficult to achieve.

[0004] Therefore, improving the accuracy of ambiguity fixation is a technical problem that needs to be solved. Summary of the Invention

[0005] The purpose of this application is to provide an ambiguity fixing method, apparatus, receiver, and storage medium that can improve the ambiguity fixing rate and reduce the probability of incorrect fixing, so as to meet the requirements of GNSS high-precision positioning.

[0006] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows:

[0007] In a first aspect, embodiments of this application provide a method for fixing ambiguity, the method comprising:

[0008] Select a candidate subset of ambiguity;

[0009] The LAMBDA algorithm is used to fix the ambiguity of the candidate ambiguity subset, and the ambiguity fixing result is obtained.

[0010] Determine whether the ambiguity fixation result meets the preset conditions;

[0011] If the ambiguity fixation result meets the preset condition, then the ambiguity fixation is determined to be correct, and the final ambiguity fixation solution is output.

[0012] If the ambiguity fixing result does not meet the preset conditions, then the ambiguity fixing is determined to be incorrect. The incorrectly fixed observation is identified, and the incorrectly fixed observation is removed from the ambiguity candidate subset. Then, the step of fixing the ambiguity of the ambiguity candidate subset using the LAMBDA algorithm is repeated until the ambiguity is fixed correctly.

[0013] Optionally, the candidate subset of ambiguities includes the floating-point solutions of the double-difference ambiguity and its covariance matrix;

[0014] The step of fixing the ambiguity of the ambiguity candidate subset using the LAMBDA algorithm to obtain the ambiguity fixing result includes:

[0015] The floating-point solution of the double-difference ambiguity and its covariance matrix are input into the LAMBDA algorithm for search, and the integer solution of the double-difference ambiguity and its ratio value are obtained.

[0016] Substituting the integer solution of the double-difference ambiguity into the pre-constructed double-difference carrier observation equation yields a fixed solution;

[0017] The coordinate parameters of the fixed solution are obtained by performing least squares calculation on the fixed solution.

[0018] Based on the integer solution of the double-difference ambiguity and the coordinate parameters of the fixed solution, the post-hoc residual of each carrier phase is calculated;

[0019] The ambiguity fixation result includes the post-hoc residual of each carrier phase, the ratio value of the integer solution of the double-difference ambiguity, and the number of double-difference ambiguities.

[0020] Optionally, the step of calculating the post-hoc residual for each carrier phase based on the integer solution of the double-difference ambiguity and the coordinate parameters of the fixed solution includes:

[0021] Based on the coordinate parameters of the fixed solution, the coordinates of the base station, the broadcast ephemeris coordinates of different satellites calculated at the base station, and the broadcast ephemeris coordinates of different satellites calculated at the rover station, calculate the coordinate parameters of the fixed solution and the satellite-to-ground distances from the base station and the rover station to different satellites respectively.

[0022] Based on the coordinate parameters of the fixed solution, the satellite-to-ground distances from the base station and the rover to different satellites, calculate the satellite-to-ground distance double difference;

[0023] Based on the integer solution of the double-difference ambiguity and the double-difference value of the satellite-to-ground distance, the post-hoc residual of each carrier phase is calculated.

[0024] Optionally, the satellite-to-ground distance double difference value satisfies the formula:

[0025]

[0026] in, For double-difference differential operators, b is the receiver number of the base station, r is the receiver number of the rover station, s is the satellite, and ref is the reference satellite; The coordinate parameters of the fixed solution and the satellite-to-ground distance between satellite s are given. The distance between the reference station and satellite s is the satellite-to-ground distance. The distance between the rover and the reference satellite (ref) is the satellite-to-ground distance. The distance between the base station and the reference satellite ref is the satellite-to-ground distance.

[0027] Optionally, the coordinate parameters of the fixed solution and the satellite-to-ground distance between satellites 's' satisfy the formula:

[0028]

[0029] The satellite-to-ground distance between the reference station and satellite s satisfies the formula:

[0030]

[0031] The satellite-to-ground distance from the rover to the reference satellite ref satisfies the formula:

[0032]

[0033] The distance between the base station and the reference satellite ref satisfies the formula:

[0034]

[0035] Among them, (X) b ,Y b Z b () represents the coordinates of the base station. Here are the broadcast ephemeris coordinates of satellite s calculated at the reference station. The reference satellite's broadcast ephemeris coordinates calculated at the base station; Here are the broadcast ephemeris coordinates of satellite s calculated at the rover station. The reference satellite's broadcast ephemeris coordinates calculated at the rover station; The coordinate parameters are those of the fixed solution.

[0036] Optionally, the post-hoc residual for each carrier phase satisfies the formula:

[0037]

[0038] in, For the double-difference differential operator, b is the receiver number of the base station, r is the receiver number of the rover station, s is the satellite, ref is the reference satellite; is the frequency number, λ i The carrier phase wavelength, For carrier double-difference observations; V i This represents the post-test residual. The satellite-to-Earth distance is the double difference value. is the integer solution of the double-difference ambiguity.

[0039] Optionally, the ambiguity fixing result includes the post-hoc residual for each carrier phase, the ratio value of the integer solution of the double-difference ambiguity, and the number of double-difference ambiguities;

[0040] The preset conditions include: the chi-square test is passed, the ratio value of the integer solution of the double difference ambiguity is greater than a set value, and the number of double difference ambiguities is greater than a set number;

[0041] The step of determining whether the ambiguity fixation result meets the preset conditions includes:

[0042] The post-hoc residual of each carrier phase is substituted into the pre-constructed chi-square test value to perform a chi-square test;

[0043] If the chi-square test passes and the ratio value of the integer solutions of the double-difference ambiguity is greater than the set number, then the ambiguity fixing result is determined to meet the preset conditions.

[0044] If the chi-square test fails, or the ratio value of the integer solution of the double-difference ambiguity is not greater than the set value, or the number of double-difference ambiguities is not greater than the set number, then the ambiguity fixing result is determined to not meet the preset conditions.

[0045] Alternatively, assume the observed satellite list is s1, s2, s3, ..., s n Then the chi-square test quantifier satisfies the formula:

[0046]

[0047] Where chiTest is the chi-square test satisfying nt degrees of freedom, sigma0 is the theoretically achievable accuracy; j is the satellite number, and r is the frequency number; b is the receiver number of the base station, and r is the receiver number of the rover station; ref is the reference satellite; V i P represents the post-test residual. i This represents the weight of the observation.

[0048] Optionally, the ambiguity fixing result includes the post-hoc residual for each of the carrier phases;

[0049] The step of identifying fixed errors in observations includes:

[0050] The apocalyptic residual of each carrier phase is standardized to obtain the standardized residual of each carrier phase;

[0051] Based on the standardized residuals of each carrier phase, robust estimation is performed to obtain the fixed solution coordinate parameters after robust estimation;

[0052] Based on the fixed solution coordinate parameters after robust estimation, the post-hoc residual of each carrier phase is recalculated;

[0053] The observation value of the satellite corresponding to the maximum value of the post-hoc residual obtained by recalculation is used as the observation value of the fixed error.

[0054] Optionally, the step of performing robust estimation based on the standardized residuals of each carrier phase to obtain the fixed solution coordinate parameters after robust estimation includes:

[0055] Based on the standardized residual of each carrier phase, using the formula:

[0056]

[0057] Perform weight selection iteration to obtain the weights of the observed values ​​after the weight selection iteration;

[0058] Where, P is the frequency number. i The initial observation weights before robust estimation, The weights of the observations after the selection iteration. The standardized residual is given; k0 and k1 are constants;

[0059] The position is recalculated based on the weights of the observed values ​​after the weighting iteration, and the fixed solution coordinate parameters after the robust estimation are obtained.

[0060] Optionally, before the step of selecting a candidate subset of ambiguity, the method further includes:

[0061] Obtain raw GNSS observations, GNSS ephemeris, and GNSS corrections;

[0062] Based on the original GNSS observations, the GNSS ephemeris, and the GNSS corrections, the pre-constructed double-difference observation equations are solved to obtain the floating-point solutions of the double-difference ambiguity and their covariance matrix.

[0063] Secondly, embodiments of this application also provide an ambiguity fixing device, the device comprising:

[0064] The selection module is used to select a candidate subset of ambiguities;

[0065] The ambiguity fixing module is used to fix the ambiguity of the ambiguity candidate subset using the LAMBDA algorithm to obtain the ambiguity fixing result.

[0066] The judgment module is used to determine whether the ambiguity fixing result meets the preset conditions;

[0067] The first execution module is used to determine that the ambiguity fixation is correct and output the final ambiguity fixation solution if the ambiguity fixation result meets the preset conditions.

[0068] The second execution module is used to determine that the ambiguity fixation is incorrect if the ambiguity fixation result does not meet the preset conditions, identify the incorrectly fixed observation, remove the incorrectly fixed observation from the ambiguity candidate subset, and then re-execute the step of using the LAMBDA algorithm to fix the ambiguity of the ambiguity candidate subset until the ambiguity is fixed correctly.

[0069] Thirdly, embodiments of this application also provide a receiver, including a processor and a memory, wherein the memory is used to store a program, and the processor is used to implement the ambiguity fixing method in the first aspect above when executing the program.

[0070] Fourthly, embodiments of this application also provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the ambiguity fixing method described in the first aspect above.

[0071] Compared to existing technologies, the ambiguity fixing method, apparatus, receiver, and storage medium provided in this application first fix the ambiguity of the candidate subset using the LAMBDA algorithm to obtain the ambiguity fixing result. If the ambiguity fixing result meets preset conditions, the ambiguity fixing is determined to be correct, and the final ambiguity fixing solution is output. If the ambiguity fixing result does not meet the preset conditions, the ambiguity fixing is determined to be incorrect, the incorrectly fixed observations are identified, and the incorrectly fixed observations are removed from the ambiguity candidate subset. Then, the LAMBDA algorithm is used again to fix the ambiguity of the candidate subset until the ambiguity is correctly fixed. This can improve the accuracy of ambiguity fixing to meet the requirements of GNSS high-precision positioning. Attached Figure Description

[0072] Figure 1 A schematic diagram of a GNSS system provided in an embodiment of this application is shown.

[0073] Figure 2 A flowchart illustrating an ambiguity fixing method provided in an embodiment of this application is shown.

[0074] Figure 3A block diagram of an ambiguity fixing device provided in an embodiment of this application is shown.

[0075] Figure 4 A block diagram of a receiver provided in an embodiment of this application is shown.

[0076] Icons: 100-Ambiguity fixing device; 101-Acquisition module; 102-Solution module; 103-Selection module; 105-Ambiguity fixing module; 106-Judgment module; 107-First execution module; 108-Second execution module; 10-Receiver; 11-Processor; 12-Memory; 13-Bus. Detailed Implementation

[0077] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0078] Currently, the main GNSS positioning technologies include RTK (Real-Time Kinematic) and PPP-RTK (Precise Point Positioning and Real-Time Kinematic) technologies.

[0079] RTK technology achieves real-time, high-precision centimeter-level positioning by subtracting from a reference station or VRS (Virtual Reference Station) point, thereby eliminating or mitigating the effects of satellite orbital errors, satellite clock biases, and atmospheric errors. PPP-RTK technology, on the other hand, achieves real-time, high-precision centimeter-level positioning by broadcasting SSR (State Space Representation) data to eliminate or mitigate the effects of satellite orbital errors, satellite clock biases, satellite phase biases, satellite code biases, and atmospheric errors.

[0080] Both RTK and PPP-RTK technologies require resolving unknown phase ambiguities and attempting to fix them as integers to provide reliable, high-precision centimeter-level positioning services. Therefore, as mentioned earlier, improving the accuracy of ambiguity fixation remains a persistent challenge for those skilled in the art.

[0081] To address the aforementioned technical problems, this application's embodiments output the final ambiguity-fixed solution when the ambiguity fixation is correct. When ambiguity fixation is incorrect, the incorrectly fixed observations are identified and removed from the ambiguity candidate subset. Ambiguity fixation is then performed again until the ambiguity is correctly fixed. This improves the accuracy of ambiguity fixation, meeting the requirements of high-precision GNSS positioning. A detailed description follows.

[0082] The ambiguity fixing method provided in this application embodiment can be applied to a receiver in a GNSS system. The receiver can be mounted on a vehicle to enable navigation during vehicle operation; of course, it can also be mounted on other devices to enable navigation; this application embodiment does not impose any limitations on this.

[0083] Please refer to Figure 1 A GNSS system can include multiple receivers and multiple satellites. Each receiver can communicate unidirectionally with multiple satellites; that is, the receiver receives signals transmitted by the satellites but does not transmit signals to the satellites. The following description uses a single receiver as an example. The multiple satellites can include GPS satellites, Galileo satellites, BDS BeiDou satellites, etc. For example, in Figure 1, satellite 1 can be a GPS satellite, satellite 2 can be a Galileo satellite, and satellite 3 can be a BDS BeiDou satellite. This application does not impose any limitations on this embodiment.

[0084] Please refer to Figure 2 , Figure 2 A flowchart illustrating the ambiguity fixing method provided in an embodiment of this application is shown. This ambiguity fixing method, applied to a receiver, may include the following steps:

[0085] S101, acquire raw GNSS observations, GNSS ephemeris, and GNSS corrections.

[0086] In this embodiment, the raw GNSS observations and GNSS ephemeris come from the receiver performing the ambiguity fixing method and are real data. The raw GNSS observations may include pseudorange observations, carrier phase observations, and Doppler observations, etc. The GNSS ephemeris may include precise orbital clock bias data, satellite-end pseudorange, phase hardware delay data, and ionospheric and tropospheric delay data along the satellite signal propagation path, etc.

[0087] GNSS corrections come from other receivers in the GNSS system and are virtual data. GNSS corrections can include VRS (Virtual Reference Station), SSR data, etc.

[0088] S102, based on the original GNSS observations, GNSS ephemeris and GNSS corrections, solves the pre-constructed double-difference observation equations to obtain the parameter floating-point solution of the double-difference ambiguity and its covariance matrix.

[0089] In this embodiment, the double-difference observation equation is constructed in the following way:

[0090] The first step is that the GNSS carrier phase observation equation and pseudorange observation equation can be expressed as shown in equations (1) and (2):

[0091]

[0092]

[0093] Where i is the frequency number used to distinguish different frequency points; r is the receiver number of the rover station; and s is the satellite.

[0094] λ i The carrier phase wavelength is expressed in meters (m).

[0095] The carrier phase observation from receiver r to satellite s at frequency i, in cycles;

[0096] The distance from receiver r to satellite s is expressed in meters (m).

[0097] c is the speed of light, measured in m / s;

[0098] δT r The clock bias of receiver r is expressed in seconds.

[0099] δT s The clock bias of satellite s, in seconds;

[0100] The ionospheric delay from receiver r to satellite frequency i (s), in meters (m).

[0101] The tropospheric delay from receiver r to satellite s is expressed in meters (m).

[0102] The integer ambiguity from receiver r to satellite s frequency i, in cycles;

[0103] Lbias i,r The phase bias of receiver frequency i is given by r, in meters.

[0104] Lbias i,s The phase bias of satellite frequency i is given in meters (m).

[0105] The noise of the carrier phase observation from receiver r to satellite frequency i at frequency s is expressed in meters (m).

[0106] The pseudorange observation value from receiver r to satellite s at frequency i is in meters.

[0107] Pbias i,r CodeBias of receiver frequency i, in meters (m);

[0108] Pbias i,s Code Bias for satellite frequency i, in meters (m);

[0109] The pseudorange observation noise from receiver r to satellite s at frequency i is expressed in meters.

[0110] In the second step, assuming b is the receiver number of the base station, the carrier observation equation and pseudorange observation equation for inter-station differential can be expressed as formulas (3) and (4):

[0111]

[0112]

[0113] Due to satellite clock bias (2T) s Satellite Phase Bias (Lbias) i,s ) and satellite-side Code Bias (Pbias) i ,s The effect on different observation stations is consistent, therefore: cΔδT s =0, ΔLbias i,s =0 and ΔPbias i,s =0. Furthermore, since the distance between the base station and the rover is relatively short, generally less than 5 km, and ionospheric and tropospheric errors have spatial correlation, it can be approximated as:

[0114] Then formulas (3) and (4) can be simplified to formulas (5) and (6):

[0115]

[0116]

[0117] The meanings of the symbols in formulas (3) to (6) are as follows:

[0118] Δ is the inter-station difference operator; The noise of the carrier phase observation value between the reference station b and the rover r of satellite s at frequency i is the single difference between the stations. The noise of the pseudorange observation between the reference station b and the rover r of satellite s at frequency i is the noise of the single difference between the stations.

[0119] Third, assuming the reference satellite is selected as ref, the carrier observation equation and pseudorange observation equation for double difference (inter-station difference and inter-satellite difference) can be expressed as shown in formulas (7) and (8):

[0120]

[0121]

[0122] Receiver clock error (ΔδT) after inter-station difference rb ), Receiver Phase Bias (ΔLbias) i,rb ) and receiver-side Code Bias (ΔPbias) i,rb The impact is the same on different satellites. Therefore: and Then formulas (7) and (8) can be simplified to formulas (9) and (10):

[0123]

[0124]

[0125] Formulas (9) and (10) are the double-difference observation equations.

[0126] The meanings of the symbols in formulas (7) to (10) are as follows:

[0127] It is a double difference operator. This represents the noise in the carrier phase observations with double differences. This represents the noise in the pseudorange observations with double differences.

[0128] In this embodiment, Kalman filtering or least squares is used to solve the double-difference observation equations shown in equations (9) and (10), thereby obtaining the receiver's coordinate parameters (X, Y, Z) and the floating-point solution of the double-difference ambiguity parameters. The covariance matrix of the floating-point solution of the double-difference ambiguity.

[0129] S103, Select a candidate subset of ambiguity.

[0130] In this embodiment, the candidate subset of ambiguity includes some or all of the floating-point solutions of the parameters of double-difference ambiguities and their covariance matrices. The specific subset can be flexibly selected according to the actual situation, and this embodiment does not impose any restrictions on it.

[0131] S105, the LAMBDA algorithm is used to fix the ambiguity of the candidate ambiguity subset, and the ambiguity fixation result is obtained.

[0132] In this embodiment, the process of fixing the ambiguity of the ambiguity candidate subset using the LAMBDA algorithm to obtain the ambiguity fixing result may include S1051 to S1054.

[0133] S1051, input the floating-point solution of the double-difference ambiguity parameters and its covariance matrix into the LAMBDA algorithm for search, and obtain the integer solution of the double-difference ambiguity and its ratio value.

[0134] That is, to make the double-difference ambiguity and its corresponding covariance matrix Inputting the data into LAMBDA for searching yields an integer solution for the double-difference ambiguity. Furthermore, the ratio value of the integer solution of the double-difference ambiguity is obtained.

[0135] The ratio value is obtained using the ratio test, which characterizes the similarity between the vectors of the optimal and suboptimal solutions. It can be defined as the ratio of the quadratic residual form of the integer suboptimal solution to the quadratic residual form of the integer optimal solution. The test threshold for the ratio test is generally set to 2 or 3.

[0136] S1052, substitute the integer solution of the double-difference ambiguity into the pre-constructed double-difference carrier observation equation to obtain the fixed solution.

[0137] S1053, perform least squares calculation on the fixed solution to obtain the coordinate parameters of the fixed solution.

[0138] That is, the integer solution of the double-difference ambiguity is... Substitute these values ​​into equation (9) and perform least squares calculations to obtain the coordinate parameters of the fixed solution.

[0139] S1054 calculates the post-hoc residual for each carrier phase based on the coordinate parameters of the integer solution and the fixed solution of the double-difference ambiguity.

[0140] That is, using the integer solutions of the obtained double-difference ambiguity and coordinate parameters of the fixed solution Calculate the post-hoc residual for each carrier phase. The calculation process may include S10541 to S10543.

[0141] S10541, based on the coordinate parameters of the fixed solution, the coordinates of the reference station, the broadcast ephemeris coordinates of different satellites calculated at the reference station, and the broadcast ephemeris coordinates of different satellites calculated at the rover station, calculate the coordinate parameters of the fixed solution and the satellite-to-ground distances between the reference station and the rover station and different satellites.

[0142] In one possible implementation, assume the base station coordinates are (X... b ,Y b Z b The broadcast ephemeris coordinates of satellite s calculated at the base station are: The broadcast ephemeris coordinates calculated by the reference satellite at the base station are: The coordinates of the rover are (X r ,Y r Z r The broadcast ephemeris coordinates of satellite s calculated at the rover station are: The broadcast ephemeris coordinates calculated at the rover station for the reference satellite are: The coordinate parameters of the fixed solution are

[0143] The coordinate parameters of the fixed solution and the satellite-to-ground distance s satisfy the formula:

[0144]

[0145] The satellite-to-ground distance between the base station and satellite s satisfies the formula:

[0146]

[0147] The satellite-to-ground distance from the rover to the reference satellite (ref) satisfies the following formula:

[0148]

[0149] The satellite-to-ground distance from the base station to the reference satellite (ref) satisfies the formula:

[0150]

[0151] S10542, calculate the double difference of satellite-to-ground distance based on the coordinate parameters of the fixed solution and the satellite-to-ground distances between the base station and the rover station and different satellites.

[0152] In one possible implementation, the satellite-to-Earth distance double difference satisfies the formula:

[0153]

[0154] in, For double-difference differential operators, b is the receiver number of the base station, r is the receiver number of the rover station, s is the satellite, and ref is the reference satellite; To fix the coordinate parameters of the solution and the satellite-to-ground distance between satellites s, The distance between the base station and satellite s is the distance between the base station and the satellite. The distance between the rover station and the reference satellite (ref) is the satellite-to-ground distance. The distance between the base station and the reference satellite (ref) is the distance between the base station and the ground.

[0155] S10543, based on the integer solution of the double-difference ambiguity and the double difference value of the satellite-to-ground distance, calculate the post-hoc residual for each carrier phase.

[0156] In one possible implementation, the apologetic residual for each carrier phase satisfies formula (11):

[0157]

[0158] in, For the double-difference differential operator, b is the receiver number of the base station, r is the receiver number of the rover station, s is the satellite, ref is the reference satellite; is the frequency number, λ i The carrier phase wavelength, For carrier double-difference observations; V i Indicates the post-test residual. For the satellite's distance from Earth, there are two differences. For integer solutions of double-difference ambiguity.

[0159] Thus, the results of fixed ambiguity can be obtained, including: the post-hoc residual for each carrier phase, the ratio value of the integer solutions of the double-difference ambiguity, and the number of double-difference ambiguities.

[0160] S106, determine whether the ambiguity fixation result meets the preset conditions.

[0161] In this embodiment, the preset conditions include: the chi-square test is passed and the ratio value of the integer solution of the double difference ambiguity is greater than a set value (e.g., 3) and the number of the double difference ambiguities is greater than a set number (e.g., 5).

[0162] The process of determining whether the ambiguity fixation result meets the preset conditions may include S1061 to S1063.

[0163] S1061, substitute the post-hoc residual of each carrier phase into the pre-constructed chi-square test quantity to perform a chi-square test.

[0164] In one possible implementation, assume the observed satellite list is s1, s2, s3, ..., s n Then the chi-square test statistic satisfies the formula:

[0165]

[0166] Where chiTest is the chi-square test satisfying nt degrees of freedom, sigma0 is the theoretically achievable accuracy; j is the satellite number, and r is the frequency number; b is the receiver number of the base station, and r is the receiver number of the rover station; ref is the reference satellite; V i P represents the post-test residual. i This represents the weight of the observation.

[0167] S1062, if the chi-square test passes and the ratio value of the integer solutions of the double-difference ambiguity is greater than the set number, then the ambiguity fixing result is determined to meet the preset conditions.

[0168] S1063, if the chi-square test fails, or the ratio value of the integer solution of the double-difference ambiguity is not greater than the set value, or the number of double-difference ambiguities is not greater than the set number, then the ambiguity fixing result is determined to not meet the preset conditions.

[0169] S107 If the ambiguity fixation result meets the preset conditions, then the ambiguity fixation is determined to be correct, and the final ambiguity fixation solution is output.

[0170] S108. If the ambiguity fixing result does not meet the preset conditions, then the ambiguity fixing is determined to be incorrect. The incorrectly fixed observation is identified, and the incorrectly fixed observation is removed from the ambiguity candidate subset. Then, the step of fixing the ambiguity using the LAMBDA algorithm is re-executed until the ambiguity is fixed correctly.

[0171] In this embodiment, the process of identifying fixed erroneous observations may include S1081 to S1084.

[0172] S1081, standardize the post-hoc residuals of each carrier phase to obtain the standardized residuals of each carrier phase.

[0173] S1082, robust estimation is performed based on the standardized residuals of each carrier phase to obtain the fixed solution coordinate parameters after robust estimation.

[0174] In one possible implementation, if the chi-square test fails, robust coordinate parameters are obtained through robust estimation, the specific process of which includes:

[0175] First, based on the standardized residual of each carrier phase, using the formula:

[0176]

[0177] Perform weight selection iteration to obtain the weights of the observed values ​​after the weight selection iteration;

[0178] Where, P is the frequency number. i The initial observation weights before robust estimation, The weights of the observations after the selection iteration. Let k be the standardized residual; k0 and k1 are constants.

[0179] Then, the position is recalculated based on the weights of the observed values ​​after the weighting iteration. That is, the weights of the observed values ​​after the weighting iteration are substituted into formula (11) to obtain the fixed solution coordinate parameters after robust estimation.

[0180] S1083, based on the fixed solution coordinate parameters after robust estimation, recalculate the post-hoc residuals for each carrier phase.

[0181] That is, using the fixed solution coordinate parameters after robust estimation, the apostolic residuals of each satellite observation are recalculated using formula (11), and the index s of the satellite observation with the largest residual is recorded. j .

[0182] S1084 uses the observation value of the satellite corresponding to the maximum value of the post-verification residual obtained by recalculation as the observation value with fixed error.

[0183] That is, to put satellite s j The observed value is used as the fixed error observation value and is removed from the ambiguity candidate subset. Then, return to step S105 and continue until the ambiguity is fixed correctly.

[0184] Existing GNSS ambiguity fixing techniques first construct a subset of ambiguity candidates that meet certain conditions. The floating-point solutions to the ambiguities and their corresponding covariance matrices are then input into LAMBDA for searching. If the ratio value meets the conditions, ambiguity fixing is performed. If the ratio value does not meet the conditions, the subset of ambiguity candidates is selected based on information such as satellite altitude cutoff angle, signal-to-noise ratio, covariance matrix, and residuals of the observed floating-point solutions. Then, LAMBDA is searched again on the subset of ambiguity candidates until the ratio value and other conditions are verified, at which point the ambiguity-fixed solution coordinates are calculated to meet the high-precision centimeter-level or even millimeter-level absolute positioning requirements of GNSS.

[0185] Clearly, existing GNSS ambiguity fixing techniques often rely on information such as satellite altitude cutoff angle, signal-to-noise ratio, covariance matrix, and observation floating-point solution residuals to filter ambiguity subsets. Sometimes, this fails to eliminate low-quality observations for ambiguity fixing, and may even eliminate too many observations, resulting in fewer observations entering the LAMBDA search and leading to fixing errors. Furthermore, the conditions for determining ambiguity fixing often only include ratio value judgments and bootstrap tests, which can also lead to ambiguity fixing errors, consequently affecting the fusion results of inertial navigation and other sensors.

[0186] The ambiguity fixing method provided in this application fixes the ambiguity candidate subset using the LAMBDA algorithm. After obtaining the ambiguity fixing result, on the one hand, the chi-square test is used to verify whether the ambiguity fixing is correct. Only when the chi-square test passes and the ratio value of the integer solutions of the double-difference ambiguities is greater than a set number, is the ambiguity fixing result determined to be correct, thereby reducing the probability of ambiguity fixing errors. On the other hand, when an ambiguity fixing error is determined, robust estimation is used to identify the incorrectly fixed ambiguities and remove them from the ambiguity candidate subset. Then, ambiguity fixing is performed again until the ambiguity is fixed correctly, thereby minimizing the occurrence of incorrect or difficult-to-fix situations. This can improve the accuracy of ambiguity fixing to meet the requirements of GNSS high-precision positioning.

[0187] In order to perform the corresponding steps in the above method embodiments and various possible implementations, an implementation of an ambiguity fixing device is given below.

[0188] Please refer to Figure 3 , Figure 3 A block diagram of a ambiguity fixing device 100 provided in an embodiment of this application is shown. The ambiguity fixing device 100 is applied to a receiver and includes: a selection module 103, an ambiguity fixing module 105, a judgment module 106, a first execution module 107, and a second execution module 108.

[0189] Module 103 is used to select a candidate subset of ambiguity.

[0190] The ambiguity fixing module 105 is used to fix the ambiguity of the ambiguity candidate subset using the LAMBDA algorithm to obtain the ambiguity fixing result.

[0191] The judgment module 106 is used to determine whether the ambiguity fixation result meets the preset conditions.

[0192] The first execution module 107 is used to determine that the ambiguity fixation is correct if the ambiguity fixation result meets the preset conditions, and output the final ambiguity fixation solution.

[0193] The second execution module 108 is used to determine that the ambiguity fixation is incorrect if the ambiguity fixation result does not meet the preset conditions, identify the incorrectly fixed observations, remove the incorrectly fixed observations from the ambiguity candidate subset, and then re-execute the step of fixing the ambiguity using the LAMBDA algorithm on the ambiguity candidate subset until the ambiguity is fixed correctly.

[0194] Optionally, the candidate subset of ambiguities includes the floating-point solutions of the parameters of the double-difference ambiguity and its covariance matrix. The ambiguity fixing module 105 is specifically used for:

[0195] The floating-point solution of the double-difference ambiguity and its covariance matrix are input into the LAMBDA algorithm for search, and the integer solution of the double-difference ambiguity and its ratio value are obtained.

[0196] Substituting the integer solutions of the double-difference ambiguity into the pre-constructed double-difference carrier observation equation yields a fixed solution;

[0197] The coordinate parameters of the fixed solution are obtained by performing least squares calculation on the fixed solution.

[0198] Based on the coordinate parameters of the integer and fixed solutions of the double-difference ambiguity, the post-hoc residual of each carrier phase is calculated;

[0199] The ambiguity fixation results include the post-hoc residual for each carrier phase, the ratio value of the integer solutions of the double-difference ambiguity, and the number of double-difference ambiguities.

[0200] Optionally, the ambiguity fixing module 105 performs calculations based on the coordinate parameters of the integer and fixed solutions of the double-difference ambiguity to determine the post-hoc residual for each carrier phase, including:

[0201] Based on the coordinate parameters of the fixed solution, the coordinates of the base station, the broadcast ephemeris coordinates of different satellites calculated at the base station, and the broadcast ephemeris coordinates of different satellites calculated at the rover station, calculate the coordinate parameters of the fixed solution and the satellite-to-ground distances from the base station and the rover station to different satellites.

[0202] Calculate the double difference of satellite-to-ground distance based on the coordinate parameters of the fixed solution and the satellite-to-ground distances from the base station and the rover to different satellites.

[0203] Based on the integer solutions of the double-difference ambiguity and the double difference values ​​of the satellite-to-ground distance, the post-hoc residual of each carrier phase is calculated.

[0204] Optionally, the two differences between the satellite and the ground satisfy the formula:

[0205]

[0206] in, For double-difference differential operators, b is the receiver number of the base station, r is the receiver number of the rover station, s is the satellite, and ref is the reference satellite; To fix the coordinate parameters of the solution and the satellite-to-ground distance between satellites s, The distance between the base station and satellite s is the distance between the base station and the satellite. The distance between the rover station and the reference satellite (ref) is the satellite-to-ground distance. The distance between the base station and the reference satellite (ref) is the distance between the base station and the ground.

[0207] Optionally, the coordinate parameters of the fixed solution and the satellite-to-ground distance s satisfy the formula:

[0208]

[0209] The satellite-to-ground distance between the base station and satellite s satisfies the formula:

[0210]

[0211] The satellite-to-ground distance from the rover to the reference satellite (ref) satisfies the following formula:

[0212]

[0213] The satellite-to-ground distance from the base station to the reference satellite (ref) satisfies the formula:

[0214]

[0215] Among them, (X) b ,Y b Z b () represents the coordinates of the base station. Here are the broadcast ephemeris coordinates of satellite s calculated at the reference station. The reference satellite's broadcast ephemeris coordinates calculated at the base station; Here are the broadcast ephemeris coordinates of satellite s calculated at the rover station. The reference satellite's broadcast ephemeris coordinates calculated at the rover station; The coordinate parameters are fixed for the solution.

[0216] Optionally, the post-hoc residual for each carrier phase satisfies the formula:

[0217]

[0218] in, For the double-difference differential operator, b is the receiver number of the base station, r is the receiver number of the rover station, s is the satellite, ref is the reference satellite; is the frequency number, λ i The carrier phase wavelength, For carrier double-difference observations; V i Indicates the post-test residual. For the satellite's distance from Earth, there are two differences. For integer solutions of double-difference ambiguity.

[0219] Optionally, the preset conditions include: passing the chi-square test, the ratio value of the integer solutions of the double-difference ambiguity being greater than a set value, and the number of double-difference ambiguities being greater than a set number; the judgment module 106 is specifically used for:

[0220] Substitute the post-hoc residual of each carrier phase into the pre-constructed chi-square test value to perform a chi-square test;

[0221] If the chi-square test passes and the ratio value of the integer solutions of the double-difference ambiguity is greater than the set number, then the ambiguity fixing result is determined to meet the preset conditions.

[0222] If the chi-square test fails, or the ratio value of the integer solutions of the double-difference ambiguity is not greater than the set value, or the number of double-difference ambiguities is not greater than the set number, then the ambiguity fixation result does not meet the preset conditions.

[0223] Alternatively, assume the observed satellite list is s1, s2, s3, ..., s n Then the chi-square test statistic satisfies the formula:

[0224]

[0225] Where chiTest is the chi-square test satisfying nt degrees of freedom, sigma0 is the theoretically achievable accuracy; j is the satellite number, and r is the frequency number; b is the receiver number of the base station, and r is the receiver number of the rover station; ref is the reference satellite; V i P represents the post-test residual. i This represents the weight of the observation.

[0226] Optionally, the second execution module 108 executes methods for identifying observations with fixed errors, including:

[0227] The apocalyptic residuals of each carrier phase are standardized to obtain the standardized residuals of each carrier phase;

[0228] Robust estimation is performed based on the standardized residuals of each carrier phase to obtain the fixed solution coordinate parameters after robust estimation;

[0229] Based on the fixed solution coordinate parameters after robust estimation, the post-hoc residuals of each carrier phase are recalculated;

[0230] The observation value of the satellite corresponding to the maximum value of the post-hoc residual obtained by recalculation is used as the observation value with fixed error.

[0231] Optionally, the second execution module 108 performs robust estimation based on the standardized residuals of each carrier phase to obtain the fixed solution coordinate parameters after robust estimation, including:

[0232] Based on the standardized residual of each carrier phase, using the formula:

[0233]

[0234] Perform weight selection iteration to obtain the weights of the observed values ​​after the weight selection iteration;

[0235] Where, P is the frequency number. iThe initial observation weights before robust estimation, The weights of the observations after the selection iteration. The standardized residual is given; k0 and k1 are constants;

[0236] The position is recalculated based on the weights of the observed values ​​after the weighting iteration, and the fixed solution coordinate parameters after robust estimation are obtained.

[0237] Optionally, the ambiguity fixing device 100 provided in this application embodiment further includes an acquisition module 101 and a solution module 102.

[0238] The acquisition module 101 is used to acquire raw GNSS observations, GNSS ephemeris, and GNSS corrections.

[0239] The solution module 102 is used to solve the pre-constructed double-difference observation equation based on the original GNSS observations, GNSS ephemeris, and GNSS corrections, to obtain the parameter floating-point solution of the double-difference ambiguity and its covariance matrix.

[0240] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the ambiguity fixing device 100 described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0241] Please refer to Figure 4 , Figure 4 A block diagram of a receiver 10 provided in an embodiment of this application is shown. The receiver 10 includes a processor 11, a memory 12, and a bus 13. The processor 11 is connected to the memory 12 via the bus 13.

[0242] Memory 12 is used to store programs, for example Figure 3 The ambiguity fixing device 100 shown includes at least one software function module that can be stored in the memory 12 in the form of software or firmware. After receiving the execution instruction, the processor 11 executes the program to implement the ambiguity fixing method disclosed in the foregoing embodiments.

[0243] The memory 12 may include high-speed random access memory (RAM) or non-volatile memory (NVM).

[0244] Processor 11 may be an integrated circuit chip with signal processing capabilities. In implementation, each step of the above method can be completed through integrated logic circuits in the hardware of processor 11 or through software instructions. Processor 11 can be a general-purpose processor, including a Central Processing Unit (CPU), a Microcontroller Unit (MCU), a Complex Programmable Logic Device (CPLD), a Field Programmable Gate Array (FPGA), embedded ARM chips, etc.

[0245] In summary, the ambiguity fixing method, apparatus, receiver, and storage medium provided in this application first use the LAMBDA algorithm to fix the ambiguity candidate subset, obtaining the ambiguity fixing result. If the ambiguity fixing result meets preset conditions, the ambiguity fixing is determined to be correct, and the final ambiguity fixing solution is output. If the ambiguity fixing result does not meet the preset conditions, the ambiguity fixing is determined to be incorrect, the incorrectly fixed observations are identified, and the incorrectly fixed observations are removed from the ambiguity candidate subset. Then, the LAMBDA algorithm is used again to fix the ambiguity candidate subset until the ambiguity is correctly fixed. This can improve the accuracy of ambiguity fixing to meet the requirements of GNSS high-precision positioning.

[0246] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for fixing ambiguity, characterized in that, The method includes: Select a candidate subset of ambiguity; The ambiguity candidate subset is fixed using the LAMBDA algorithm to obtain the ambiguity fixing result, which includes the post-hoc residual for each carrier phase. Determine whether the ambiguity fixation result meets the preset conditions; If the ambiguity fixation result meets the preset condition, then the ambiguity fixation is determined to be correct, and the final ambiguity fixation solution is output. If the ambiguity fixing result does not meet the preset conditions, then an ambiguity fixing error is determined. The post-hoc residual of each carrier phase is standardized to obtain a standardized residual for each carrier phase. Based on the standardized residual of each carrier phase, robust estimation is performed to obtain the fixed solution coordinate parameters after robust estimation. Based on the fixed solution coordinate parameters after robust estimation, the post-hoc residual of each carrier phase is recalculated. The observation value of the satellite corresponding to the maximum value of the recalculated post-hoc residual is taken as the fixed error observation value. After removing the fixed error observation value from the ambiguity candidate subset, the step of fixing the ambiguity using the LAMBDA algorithm is repeated until the ambiguity is fixed correctly.

2. The method as described in claim 1, characterized in that, The candidate subset of ambiguities includes the floating-point solutions of the double-difference ambiguity and its covariance matrix; The step of fixing the ambiguity of the ambiguity candidate subset using the LAMBDA algorithm to obtain the ambiguity fixing result includes: The floating-point solution of the double-difference ambiguity and its covariance matrix are input into the LAMBDA algorithm for search, and the integer solution of the double-difference ambiguity and its ratio value are obtained. Substituting the integer solution of the double-difference ambiguity into the pre-constructed double-difference carrier observation equation yields a fixed solution; The coordinate parameters of the fixed solution are obtained by performing least squares calculation on the fixed solution. Based on the integer solution of the double-difference ambiguity and the coordinate parameters of the fixed solution, the post-hoc residual of each carrier phase is calculated; The ambiguity fixing result also includes the ratio value of the integer solution of the double-difference ambiguity and the number of double-difference ambiguities.

3. The method as described in claim 2, characterized in that, The step of calculating the post-hoc residual for each carrier phase based on the integer solution of the double-difference ambiguity and the coordinate parameters of the fixed solution includes: Based on the coordinate parameters of the fixed solution, the coordinates of the base station, the broadcast ephemeris coordinates of different satellites calculated at the base station, and the broadcast ephemeris coordinates of different satellites calculated at the rover station, calculate the coordinate parameters of the fixed solution and the satellite-to-ground distances from the base station and the rover station to different satellites respectively. Based on the coordinate parameters of the fixed solution, the satellite-to-ground distances from the base station and the rover to different satellites, calculate the satellite-to-ground distance double difference; Based on the integer solution of the double-difference ambiguity and the double-difference value of the satellite-to-ground distance, the post-hoc residual of each carrier phase is calculated.

4. The method as described in claim 3, characterized in that, The two differences between the satellite and the ground satisfy the formula: in, It is a double difference operator. The receiver number of the base station. Here is the receiver number for the rover station, and 's' represents the satellite. For reference satellite; The coordinate parameters of the fixed solution and the satellite-to-ground distance between satellite s are given. The distance between the reference station and satellite s is the satellite-to-ground distance. The distance between the rover and the reference satellite (ref) is the satellite-to-ground distance. The distance between the base station and the reference satellite ref is the satellite-to-ground distance.

5. The method as described in claim 4, characterized in that, The coordinate parameters of the fixed solution and the satellite-to-ground distance between satellites 's' satisfy the formula: The satellite-to-ground distance between the reference station and satellite s satisfies the formula: The satellite-to-ground distance from the rover to the reference satellite ref satisfies the formula: The distance between the base station and the reference satellite ref satisfies the formula: in, For the coordinates of the base station, Here are the broadcast ephemeris coordinates of satellite s calculated at the reference station. The reference satellite's broadcast ephemeris coordinates calculated at the base station; Here are the broadcast ephemeris coordinates of satellite s calculated at the rover station. The reference satellite's broadcast ephemeris coordinates calculated at the rover station; The coordinate parameters are those of the fixed solution.

6. The method as described in claim 3, characterized in that, The post-hoc residual for each carrier phase satisfies the formula: in, It is a double difference operator. The receiver number of the base station. Here is the receiver number for the rover station, and 's' represents the satellite. For reference satellite; For frequency numbering, The carrier phase wavelength, These are carrier double-difference observations; This represents the post-test residual. The difference between the satellite and Earth distances is the double difference value. is the integer solution of the double-difference ambiguity.

7. The method as described in claim 2, characterized in that, The preset conditions include: passing the chi-square test, and the ratio value of the integer solutions of the double-difference ambiguity being greater than a set value, and the number of double-difference ambiguities being greater than a set number; The step of determining whether the ambiguity fixation result meets the preset conditions includes: The post-hoc residual of each carrier phase is substituted into the pre-constructed chi-square test value to perform a chi-square test; If the chi-square test passes and the ratio value of the integer solutions of the double-difference ambiguity is greater than the set number, then the ambiguity fixing result is determined to meet the preset conditions. If the chi-square test fails, or the ratio value of the integer solution of the double-difference ambiguity is not greater than the set value, or the number of double-difference ambiguities is not greater than the set number, then the ambiguity fixing result is determined to not meet the preset conditions.

8. The method as described in claim 7, characterized in that, Assuming the observed satellite list is Then the chi-square test quantifier satisfies the formula: in, To satisfy the degree of freedom Chi-square test, The theoretically achievable level of precision; Number the satellite. Assign frequency numbers; The receiver number of the base station. The receiver number for the rover station; For reference satellite; This represents the post-test residual. This represents the weight of the observation.

9. The method as described in claim 1, characterized in that, The step of performing robust estimation based on the standardized residuals of each carrier phase to obtain the fixed solution coordinate parameters after robust estimation includes: Based on the standardized residual of each carrier phase, using the formula: Perform weight selection iteration to obtain the weights of the observed values ​​after the weight selection iteration; in, For frequency numbering, The initial observation weights before robust estimation, The weights of the observations after the selection iteration. The standardized residual; and It is a constant; The position is recalculated based on the weights of the observed values ​​after the weighting iteration, and the fixed solution coordinate parameters after the robust estimation are obtained.

10. The method as described in claim 1, characterized in that, Prior to the step of selecting a candidate subset of ambiguity, the method further includes: Obtain raw GNSS observations, GNSS ephemeris, and GNSS corrections; Based on the original GNSS observations, the GNSS ephemeris, and the GNSS corrections, the pre-constructed double-difference observation equations are solved to obtain the floating-point solutions of the double-difference ambiguity and their covariance matrix.

11. A device for fixing ambiguity, characterized in that, The device includes: The selection module is used to select a candidate subset of ambiguities; The ambiguity fixing module is used to fix the ambiguity of the ambiguity candidate subset using the LAMBDA algorithm to obtain the ambiguity fixing result, which includes the post-hoc residual of each carrier phase. The judgment module is used to determine whether the ambiguity fixing result meets the preset conditions; The first execution module is used to determine that the ambiguity fixation is correct and output the final ambiguity fixation solution if the ambiguity fixation result meets the preset conditions. The second execution module is configured to determine an ambiguity fixing error if the ambiguity fixing result does not meet the preset conditions, standardize the post-hoc residual of each carrier phase to obtain the standardized residual of each carrier phase, perform robust estimation based on the standardized residual of each carrier phase to obtain the fixed solution coordinate parameters after robust estimation, recalculate the post-hoc residual of each carrier phase based on the fixed solution coordinate parameters after robust estimation, take the observation value of the satellite corresponding to the maximum value of the recalculated post-hoc residual as the fixed error observation value, remove the fixed error observation value from the ambiguity candidate subset, and re-execute the step of fixing the ambiguity using the LAMBDA algorithm on the ambiguity candidate subset until the ambiguity is fixed correctly.

12. A receiver, characterized in that, It includes a processor and a memory, the memory being used to store a program, and the processor being used to implement the ambiguity fixing method according to any one of claims 1-10 when executing the program.

13. A computer-readable storage medium, characterized in that, It stores a computer program that, when executed by a processor, implements the ambiguity fixing method as described in any one of claims 1-10.

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