A satellite positioning method and device in a GNSS system

Abstract

The present application discloses a satellite positioning method and device in a GNSS system. The method comprises: selecting a frequency point L1 as a reference frequency point from available frequency points of satellites in the same GNSS system, and other frequency points as target frequency points L n , and the number of target frequency points n≥1; obtain each target frequency point L n The stable value of the inter-frequency deviation relative to the reference frequency point L1#imgabs0# is calculated based on the i-th satellite at the target frequency point L n The pseudorange observation value #imgabs1# and the stable value of the inter-frequency deviation #imgabs2# are used to calculate the pseudorange fusion value of the i-th satellite at the reference frequency point L1; after obtaining the pseudorange fusion value corresponding to the reference frequency point L1 of the satellite, the pseudorange fusion value corresponding to the reference frequency point L1 is used to perform positioning operation.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of information processing, and more particularly to a satellite positioning method and device in a GNSS system. Background Art

[0002] PVT (Position Velocity Time) solution is a basic service provided by the Global Navigation Satellite System (GNSS) worldwide. With the rapid development of GNSS systems such as the Global Positioning System (GPS), Global Navigation Satellite System (GLONASS), Galileo, and Beidou Navigation Satellite System (BDS), more available satellites provide more reliable positioning, velocity measurement, and timing services to users in various regions. Currently, PVT is increasingly used in related fields such as vehicle navigation, unmanned aerial vehicles, agricultural plant protection, and timing. The requirements for PVT reliability and accuracy in complex environments such as urban canyons, numerical occlusions, and signal interference are becoming increasingly high.

[0003] In complex obstruction scenarios, multiple GNSS systems are mainly used to increase the number of visible satellites, or by combining with inertial sensors, barometers and other sensors to increase observation information to improve service continuity. However, the number of visible satellites in obstruction scenarios is limited, and auxiliary sensors increase costs and have error accumulation, which does not effectively utilize the advantages of GNSS system multi-frequency signals.

[0004] With the modernization of the GPS system, GPSIII satellites can provide 8 navigation signals: civil L1C / A, L1C, L2C, L5C and military L1P(Y), L2P(Y), L1M, L2M; after the global networking of the BDS system is completed, BD3 satellites can simultaneously provide multi-frequency signals such as B1I, B3I, B1C, B2a, B2b. Existing studies have shown that no frequency navigation signal has an absolute advantage in all scenarios and performance indicators. Due to the existence of inter-system bias (ISB) and inter-frequency bias (IFB), the observation values ​​of multiple systems and multiple frequencies cannot be directly combined and used simultaneously in single point positioning (SPP) positioning.

[0005] At present, the research on GNSS multi-system and multi-frequency mainly focuses on fast satellite selection algorithms and single- and dual-frequency positioning selection within the system. After selecting the optimal frequency of each system, the system satellite observations of other frequencies are not used. In complex scenarios such as urban canyons and tree occlusion, the number and quality of available observations of each system's individual frequency points will drop sharply, causing large positioning errors or even discontinuous positioning. This application method has great disadvantages in terms of the availability and robustness of GNSS receivers, and more effective measures need to be provided to solve the above problems. Summary of the invention

[0006] In order to solve any of the above technical problems, an embodiment of the present application provides a satellite positioning method and device in a GNSS system.

[0007] In order to achieve the purpose of the embodiment of the present application, the embodiment of the present application provides a satellite positioning method in a GNSS system, including:

[0008] Select one frequency point L1 from the available frequency points of satellites in the same GNSS system as the reference frequency point, and the other frequency points as the target frequency points L n , and the number of target frequency points n≥1;

[0009] Get each target frequency point L n The stable value of the frequency deviation relative to the reference frequency L1

[0010] According to the i-th satellite at the target frequency point L n The pseudorange observation value of The stable value of the sum frequency deviation Calculate the pseudorange fusion value of the i-th satellite at the reference frequency point L1;

[0011] After obtaining the pseudorange fusion value corresponding to the reference frequency point L1 of the satellite, the positioning operation is performed using the pseudorange fusion value corresponding to the reference frequency point L1.

[0012] A storage medium stores a computer program, wherein the computer program is configured to execute the method described above when running.

[0013] An electronic device comprises a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute the method described above.

[0014] A satellite positioning device in a GNSS system is provided with the electronic device described above.

[0015] One of the above technical solutions has the following advantages or beneficial effects:

[0016] By estimating and compensating the IFB between different frequency points in the same GNSS system, the pseudorange observations of multiple frequency points are fused, so that the fused pseudorange observations of each satellite in the same system have the same clock error reference as their reference frequency point. Each fused pseudorange observation value can be directly used for positioning, which can effectively increase the quantity and quality of available observations.

[0017] Other features and advantages of the embodiments of the present application will be described in the subsequent description, and partly become apparent from the description, or can be understood by implementing the embodiments of the present application. The purpose and other advantages of the embodiments of the present application can be achieved and obtained by the structures specifically pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide further understanding of the technical solutions of the embodiments of the present application and constitute a part of the specification. Together with the embodiments of the embodiments of the present application, they are used to explain the technical solutions of the embodiments of the present application and do not constitute a limitation on the technical solutions of the embodiments of the present application.

[0019] Figure 1 A flowchart of a satellite positioning method in a multi-GNSS system provided in an embodiment of the present application;

[0020] Figure 2 This is a flow chart of a method for improving PVT performance of a multi-system multi-frequency GNSS receiver in an embodiment of the present application;

[0021] Figure 3 Schematic diagram of the composition structure of an apparatus for improving PVT performance of a multi-system multi-frequency GNSS receiver in an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present application more clear, the embodiments of the present application will be described in detail in conjunction with the accompanying drawings. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other arbitrarily.

[0023] Figure 1 Flow chart of a satellite positioning method in a multi-GNSS system provided in an embodiment of the present application. Figure 1 As shown, the method includes:

[0024] Step 101: Select one frequency point L1 from the available frequency points of satellites in the same GNSS system as the reference frequency point, and other frequency points as the target frequency points L n , and the number of target frequency points n≥1;

[0025] Step 102: Obtain each target frequency point L n The stable value of the frequency deviation relative to the reference frequency L1

[0026] Step 103: According to the i-th satellite at the target frequency L n The pseudorange observation value of The stable value of the sum frequency deviation Calculate the pseudorange fusion value of the i-th satellite at the reference frequency point L1;

[0027] Step 104: after obtaining the pseudorange fusion value corresponding to the reference frequency point L1 of the satellite, use the pseudorange fusion value corresponding to the reference frequency point L1 to perform positioning operation;

[0028] The method provided in the embodiment of the present application estimates and compensates for the IFB between different frequency points in the same GNSS system, and fuses the pseudorange observation values ​​of multiple frequency points, so that the fused pseudorange observation values ​​of each satellite in the same system have the same clock error reference as its reference frequency point, and each fused pseudorange observation value can be directly used for positioning, which can effectively increase the number and quality of available observation values.

[0029] The method provided in the embodiment of the present application is described below:

[0030] The method provided in the embodiment of the present application makes the following improvements to the related technology, including:

[0031] A. By estimating and compensating the IFB between different frequency points in the same GNSS system, the pseudo-range observations of multiple frequency points are fused, so that the fused pseudo-range observations of each satellite in the same system have the same clock error reference as their reference frequency point, effectively increasing the number and quality of available observations;

[0032] B. Use the clock error relationship between different GNSS systems to estimate and compensate for the ISB between different systems, so that the receiver clock error term of the pseudo-range observation values ​​of each system can share one, thereby reducing the number of unknowns;

[0033] C. When using Doppler observations for positioning, multiple Doppler observations in all GNSS systems are fused to effectively increase the number of available observations and optimize the quality of the observations.

[0034] The following are the descriptions of the above improvements one by one:

[0035] The solution provided in the embodiment of the present application can improve the performance of multi-system multi-frequency GNSS PVT solution, wherein the GNSS system has multiple satellites and multiple frequency points.

[0036] A. Fusion of pseudo-range observations of multiple frequency points in the same GNSS system, including:

[0037] In an example embodiment, the pseudorange fusion value is obtained in the following manner, including:

[0038] Using T k The target frequency L at the moment n The corresponding stable value of the frequency deviation Correct the target frequency L of the i-th satellite n The pseudorange observation value of Get the target frequency L n Pseudorange correction value relative to the reference frequency point L1

[0039] Pseudorange observation value of reference frequency point L1 of the i-th satellite And the target frequency L n Pseudorange correction value Perform fusion calculation to obtain the pseudorange fusion value of the i-th satellite at the reference frequency point L1

[0040] T is obtained by k Time target frequency L n The corresponding stable value of the frequency deviation include:

[0041] Determine T k Time target frequency L n The optimal value of inter-frequency deviation IFB Ln (T k );

[0042] Determine T k The optimal value of inter-frequency deviation IFB at time Ln (T k ) corresponds to the weight W Tk ;

[0043] Using T k-1 The stable value of the frequency deviation at the moment T k The optimal value of the time-frequency deviation IFB Ln (T k ) and its weight W Tk , and get T k Stable value of the time-frequency deviation

[0044] The target frequency L at time T0 is obtained by the following method n The corresponding stable value of the frequency deviation include:

[0045] The target frequency L of each satellite at time T0 n The frequency deviation value between the reference frequency point L1 and the corresponding preset threshold Make comparisons;

[0046] Select a frequency deviation value less than At least two satellites are used as the target frequency point L at time T0 n effective satellites;

[0047] According to the target frequency L at time T0 n The effective satellite inter-frequency deviation value is used to determine the stable value of the inter-frequency deviation at time T0.

[0048] T is obtained by k Time target frequency L n The optimal value of inter-frequency deviation IFB Ln (T k ),include:

[0049] Calculate T for each satellite k Time target frequency L n The frequency deviation value With T k-1 The target frequency L in the time period n The stable value of the frequency deviation The difference between them is used to obtain the inter-frequency deviation calibration value;

[0050] Select the satellite whose inter-frequency deviation check value meets the preset first value condition as T k Time target frequency L n effective satellites;

[0051] If the number of valid satellites selected is greater than the preset threshold, then according to T k The effective satellite at the target frequency L n The frequency deviation value is determined by T k Time target frequency L n The optimal value of inter-frequency deviation IFB Ln (T k ); otherwise, for T k-1 Time frequency deviation stability value Perform a reset.

[0052] Take the reference frequency as the first frequency L1 and the target frequency as the second frequency L2 as an example for explanation:

[0053] Step A1, obtaining a pseudorange model of two different frequency point observation values ​​of the same GNSS satellite;

[0054] The pseudo-range observation equation of the i-th satellite at the first frequency point L1 and the second frequency point L2 is as follows:

[0055]

[0056]

[0057] in, represents the pseudo-range observation value of the first frequency point L1 and the second frequency point L2; r represents the geometric distance between the receiver and the satellite; c represents the speed of light; Δt L1 Indicates the receiver clock error at the first frequency point; Δt s Indicates the satellite clock error at the first frequency point; T GD is the group delay of the satellite signal; I L1 represents the ionospheric error at the first frequency point; T represents the tropospheric error; ε L1 , ε L2 represents the observed value noise; γ represents the square of the ratio between the frequency f1 of the first frequency point L1 and the frequency f2 of the first frequency point L2, that is, γ = (f1 / f2) 2 ;IFB L2 It represents the receiver clock error deviation between the second frequency point L2 and the first frequency point L1, and i is the satellite number.

[0058] The right side of the pseudorange model is eliminated by the model: Δt related to the satellite s , T GD Modeling correction through system broadcast parameters; I L1 It is estimated by the Klobuchar model, T is estimated by the Saastamoinen model, and the multipath delay error and measurement noise are usually reduced to a relatively small level by smoothing the pseudorange observations by the carrier phase observations; the influence of the measurement noise ε is reflected by the quality of the observations in actual use and is ignored in the model.

[0059] The geometric distance r is linearized and expressed as:

[0060] r=r0-H x Δx-H y Δy-H z Δz (3)

[0061] Where r0 is the geometric distance calculated using the approximate coordinates of the station and the satellite coordinates; H x , H y , H z are the unit vectors from the approximate coordinates of the measuring station to the direction of the satellite line of sight; Δx, Δy, Δz are the user coordinates to be solved.

[0062] Substituting equation (3) into equations (1) and (2), the measurement equation can be obtained after transformation:

[0063]

[0064]

[0065] The left side of the above formula is ρ L1 , L2It is the distance value after the pseudo-range measurement value is eliminated by the model, and the right side is the position and clock error to be solved.

[0066] Step A2: Calculate the inter-frequency deviation IFB L2 :

[0067] Step A21, obtaining the inter-frequency deviation value of each satellite that simultaneously tracks the first frequency point L1 and the second frequency point L2;

[0068] Subtracting (4) from (5) yields:

[0069] IFB L2 =ρ L2 -ρ L1 (6)

[0070] For each satellite in the GNSS system that simultaneously tracks the first frequency point L1 and the second frequency point L2, an inter-frequency deviation is calculated using formula (6):

[0071] Step A22: According to T k The frequency deviation value of at least two satellites at the time is used to determine T k The optimal value of inter-frequency deviation IFB at time L2 (T k );

[0072] Specifically, the satellite altitude angle, frequency observation quality and other information are used to calculate the The weight W i , and the weighted average is obtained as T k Time L1, L2 frequency point The optimal value of inter-frequency deviation IFB L2 (T k ), as follows:

[0073]

[0074] Formula (7) calculates T k The optimal value of inter-frequency deviation IFB at time L2 (T k ) absorbs the residual ionospheric error, measurement noise and multipath error after the single difference of pseudoranges on two frequencies. This value is relatively stable over a period of time.

[0075] Step A23: According to T k-1 The stable value of the frequency deviation at the moment For the current k-th epoch T k The calculated optimal value of inter-frequency deviation IFB L2 (T k ) to perform filtering operation and further obtain T k The stable value of the frequency deviation at the moment

[0076] Specifically, determine T k The optimal value of the time-frequency deviation IFB L2 (T k ) Tk , where T k The weight W at the moment Tk It is used to calculate the optimal value of inter-frequency deviation IFB based on this moment L2 (T k ) is determined by the quantity and quality of observations;

[0077] Using T k-1 The stable value of the frequency deviation at time T k The weight W at the moment Tk , get the Tth k Stable value of frequency deviation within the time period

[0078] Specifically, T k The optimal value of the time-frequency deviation IFB L2 (T k ) and the stable value of the inter-frequency deviation estimated in the previous period Perform filtering operations to reduce observation noise and multipath errors, and obtain T k The stable inter-frequency deviation value between two frequency points at the moment, and the stable value of the inter-frequency deviation As shown in formula (8):

[0079]

[0080] Furthermore, according to the stability characteristics of the inter-frequency deviation IFB of the receiver, the weighted T used in equation (8) is k IFB at the moment L2 (T k ) to perform validity check. L2 (T k ) and T k-1 Obtained at all times Compare, if possible It is valid within the range and is used to remove IFB with large deviations. L2 (T k ) value or reset an already estimated error value.

[0081] When formula (8) is executed for the first time, Initialize, take the value of the first detection valid IFB calculated by formula (7) L2 , as the stable value of the frequency deviation at time T0 For T0, use the satellite When performing validity testing, Values ​​and preset thresholds Compare and remove those that exceed the threshold satellites, will Value less than n satellites are used as valid satellites; among which, the preset threshold value When the calculation is first started, it is an empirical value set according to the difference between the first frequency point L1 and the second frequency point L2. This step can preliminarily detect the gross error observation value and improve the accuracy of the calculated inter-frequency deviation value IFB.

[0082] This test is used to further improve The reliability of the estimates will not be discussed here.

[0083] Step A24: Use T k Stable value of the time-frequency deviation Modified T k The pseudo-range observation value of the second frequency point L2 at the time is obtained, and the target frequency point L n Pseudorange correction value relative to the reference frequency point L1

[0084] The stable value of the inter-frequency deviation obtained by formula (8) is The pseudo-range observation value of the second frequency point L2 of the i-th satellite Perform inter-frequency deviation correction to obtain pseudo-range correction value

[0085]

[0086] Comparing equation (9) with equation (4), we can see that ρ L1 and The observation equation is consistent with that of , and the quantities to be determined are the user coordinate terms Δx, Δy, Δz and the receiver clock error term Δt L1 .

[0087] Step A24: Correct the pseudorange value and the pseudorange observation value of the first frequency point L1, to obtain a pseudorange fusion value as the pseudorange observation value used for positioning;

[0088] Using formula (9), the pseudo-range observation values ​​of the second frequency point L2 tracked by each satellite can be compensated to the observation values ​​with the same clock error reference as the L1 frequency point Calculate the corresponding weight value W according to the quality of each frequency point observation value and other information 1 , W 2 , perform pseudo-range observation value fusion to obtain pseudo-range fusion value See formula (10):

[0089]

[0090] It should be noted that the n frequency points L1, L2, ..., Ln of each GNSS system depend on the satellite broadcast signal, the receiver supported frequency band and the current signal tracking status. The weight W n According to the pseudorange measurement Tracking quality and frequency deviation The accuracy of Ln is comprehensively estimated; further, if the Ln frequency point If no valid value is calculated, its weight W n =0.

[0091] The satellite broadcast signal and the frequency band supported by each receiver are fixed, but the different tracking states of signals at different frequency points will lead to large differences in the quality of the observation values ​​at the current frequency points. If the measurement value of the Ln frequency point of the i-th satellite in the current epoch is lost, then its corresponding value in equation (5) is W n =0.

[0092] Furthermore, the clock difference reference frequency point L1 is not limited to L1, and the user can select other frequency points with better tracking status of each GNSS system according to actual conditions, and it is not used to limit the protection scope of this application.

[0093] Similarly, for n frequency points in the GNSS system, using formula (8), we can get

[0094] Similarly, for the observation values ​​of n frequency points of the i-th satellite in the GNSS system, the fused pseudorange fusion value can be obtained using equations (9) and (10):

[0095]

[0096] The pseudo-range of each satellite of multiple GNSS systems in the current epoch after fusion is calculated using equation (11). When the number of effective satellites in each system is large, a joint solution is performed to obtain the user position of the current epoch and the receiver clock error of each system through the least squares or Kalman filtering method.

[0097] B. Pseudorange fusion calculation based on inter-system bias ISB compensation

[0098] When using the inter-frequency deviation IFB compensated pseudo-range for joint solution, a receiver clock error state quantity needs to be established for each GNSS system. When the satellites of N GNSS systems are jointly positioned, N+3 unknown quantities need to be estimated, and at least N+3 satellites are required for positioning. In urban canyons and severe occlusion scenarios, the number of satellites that can be observed by each GNSS constellation is very limited; in addition, in interference scenarios, after eliminating gross error satellites, each system has only 1 to 2 valid satellites remaining, and the total number of positioning satellites is still small, and the pseudo-range error may be large. At this time, only using the traditional pseudo-range model or the IFB compensated pseudo-range model, the positioning reliability is poor or even the positioning is interrupted. Therefore, the following solution is proposed:

[0099] One of the at least two GNSS systems is used as a reference system A, and the other one or at least two GNSS systems are used as a target system B, and pseudorange fusion values ​​of satellites in each GNSS system are obtained;

[0100] Determine T k The stable value of the inter-system deviation of at least one target system B relative to the reference system A at the moment

[0101] Using T k The stable value of the system deviation at the moment Correct the pseudo-range fusion value of the k-th satellite of the target system B to obtain the pseudo-range fusion value of the k-th satellite with the same clock error reference as the reference system after correction;

[0102] Using the pseudorange fusion values ​​of satellites in at least two GNSS systems with the same clock error reference, T k Positioning operation at the moment.

[0103] T is obtained by k The stable value of the inter-system deviation corresponding to the target system at the moment include:

[0104] Get T k The receiver clock difference of the target system at the reference frequency point of its system at the moment T k The receiver clock error of the time reference system at the reference frequency of the system;

[0105] Calculate the difference between the receiver clock error corresponding to the target system and the receiver clock error corresponding to the reference system as T k The optimal value of the inter-system deviation of the target system at the moment;

[0106] Determine T k The weight corresponding to the optimal value of the inter-system deviation of the target system at the moment;

[0107] Using T k-1Time system deviation stability value, T k The optimal value of the deviation between systems at the moment and its weight are obtained as T k The stable value of the deviation between systems at any time.

[0108] T is obtained by k The optimal deviation between target systems at each moment includes:

[0109] Calculated at T k The actual value of the deviation between the target system and T k-1 The difference between the deviation stability values ​​of the target systems at the moment is used to obtain the deviation check value between the systems;

[0110] If the inter-system deviation check value meets the preset second value condition, then calculate T k The stable value of the deviation between systems at the moment; otherwise, for T k-1 The stable value of the inter-system deviation of the target system is reset at that moment.

[0111] Take the GPS system as the reference system and the BDS system as the target system as an example:

[0112] Step B1: Obtain the T of the BDS system relative to the GPS system at their respective reference frequencies. k The stable value of the deviation between systems at all times;

[0113] In the same epoch, there is a deviation in the receiver clock errors of the GPS and BDS systems. Assuming that the reference frequency points of the GPS and BDS system clock errors are L1 and B1 respectively, according to equation (4), the observation equations of the GPS and BDS system satellites are expressed as follows:

[0114] ρ L1 =-H x_L1 Δx-H y_L1 Δy-H z_L1 Δz+cΔt Gps_L1 (12)

[0115] ρ B1 =-H x_B1 Δx-H y_B1 Δy-H z_B1 Δz+cΔt Bds_B1 (13)

[0116] When both the GPS and BDS systems have pseudorange observations with good signals, the receiver clock difference Δt of the GPS and BDS systems can be obtained by joint calculation. Gps_L1 , Δt Bds_B1 At this time, further obtain the deviation ISB between the two systems of the current epoch Bds_Gps , see formula (14):

[0117] ISBBds_Gps =Δt Bds_B1 -Δt Gps_L1 (14)

[0118] The inter-system deviation ISB calculated by formula (14) Bds_Gps Mainly caused by the systematic differences between the two GNSS systems, while absorbing some residual model errors, for the same receiver ISB Bds_Gps The value is relatively stable in the short term. k Epochs involved in calculating ISB Bds_Gps (T k ) is used to calculate its weight W based on the number and quality of observations Tk , and the previous epoch Perform filtering operations to weaken the current epoch observation noise and multipath error, and obtain a stable value of the inter-system deviation over a period of time See formula (15):

[0119]

[0120] Furthermore, according to the stability characteristics of the inter-system clock difference ISB, the current T k The actual value of the inter-system bias ISB of the epoch Bds_Gps (T k ) to perform validity check and ISB Bds_Gps (T k ) and the previous period of time estimated Compare and remove ISBs with large deviations from the current epoch. Bds_Gps (T k ) value or reset the previous estimated error This test is used to further improve The reliability of the estimated value is not used to limit the scope of protection of this application.

[0121] The method can be used to calculate the relationship between each system and the reference system GPS for multiple GNSS systems. Furthermore, the reference system is not limited to GPS, and users can choose other systems with better tracking status according to actual conditions, and it is not used to limit the protection scope of this application.

[0122] Step B2: Using T k The stable value of the deviation between systems at the moment is used to correct the pseudo-range fusion value of the BDS system at the reference frequency point;

[0123] When the total number of effective satellites is small, the pseudo-range fusion value of the ith satellite of the BDS system obtained by formula (11) is Further using formula (15) to calculate The pseudo-range observation value of the i-th BDS satellite after inter-system bias correction is Restore the clock error reference with the same frequency as the GPS system L1, see equation (16):

[0124]

[0125] Comparing equation (16) with equation (12) and (4), the compensated and The observation equation is consistent with that of , and the quantities to be determined are the user coordinate terms Δx, Δy, Δz and the receiver clock error term Δt L1 , and only contains the GPS clock error.

[0126] Using formula (15), we can obtain the Through formula (16), the pseudo-range observation values ​​of GLONASS, Galileo and other systems can be compensated to the pseudo-range observation values ​​with the same clock error reference as the GPS system L1 frequency point That is, the receiver clock errors of different GNSS systems are converted to the GPS system clock error. The current unknowns are only the position item and one receiver clock error, thereby reducing the number of clock error unknowns and improving positioning redundancy.

[0127] C. Fusion of Doppler information:

[0128] Utilize all available satellites from multiple GNSS systems to perform T k Doppler velocity measurement operation at all times, including:

[0129] Obtain the Doppler observation values ​​of all valid frequency points of the i-th satellite of each GNSS system;

[0130] Determine the weight of the Doppler observation value at each frequency point;

[0131] Using Doppler observations and their respective weights, the optimal value of the Doppler observations is calculated by fusion.

[0132] Using the best value of Doppler observations from all satellites Execute Section T k Doppler speed measurement operation at a certain moment.

[0133] The Doppler observation value is generated by the relative motion speed of the satellite relative to the user. For all satellites tracked at the same epoch, the Doppler measurement model of the kth satellite is expressed as formula (17):

[0134]

[0135] in: is the Doppler observation value; H is the unit vector from the station coordinates to the satellite line of sight; vk is the velocity vector of satellite k; It is the satellite clock drift; v u is the receiver velocity vector to be determined; is the receiver clock drift value to be determined; c is the speed of light; the unit is m / s.

[0136] The satellite-related speed and clock drift values ​​are calculated from the navigation message parameters. After deducting the satellite-related terms from equation (17) and linearizing it, the observation equation is established:

[0137]

[0138] Where: H x , H y , H z v is the component of the unit vector H from the station coordinates to the satellite line of sight; x 、v y 、v z is the receiver velocity v to be solved u The amount.

[0139] According to formula (18), there is no systematic error in the Doppler measurement values ​​of different GNSS systems and different frequencies. Calculate the weight W according to the quality of Doppler measurement value at each frequency point 1 , W 2 …W n , directly use equation (19) to calculate the optimal value of the fused Doppler observation

[0140]

[0141] The fused pseudo-range and Doppler measurement values ​​calculated by each satellite using the method are used for positioning and velocity measurement. According to the variance propagation law, the measurement noise of the observation value calculated after the fusion of n frequency points is reduced to a single observation value. times.

[0142] It should be noted that the validity test and weight W mentioned in this application i There are many mature calculation methods for calculation. General validity tests include consistency tests of multiple values ​​with the same physical meaning, numerical stability tests on continuous time series, and range tests with relevant empirical values. Similarly, the weight W i The calculation is generally expressed as the inverse of the measurement variance of the corresponding observation value, and the measurement variance of the satellite observation value at each frequency point is generally expressed as a function of its satellite altitude angle, CN0, continuous tracking time, observation value residual, typical model error value, etc. The validity detection and weight W described in this patent iThe calculation may also be performed by other methods, which are not limited here. The related methods and applications are well-known technologies of those skilled in the art and will not be described in detail here, nor are they used to limit the scope of protection of this application.

[0143] In practical applications, as long as the frequency points are estimated After the value is set, when the signal is unstable in complex scenes such as various obstructions, interference, and severe multipath, as long as any frequency point of a satellite is tracked, the satellite can pass through After the correction, it participates in the positioning solution. At this time, there is no need to increase the state quantity, thereby greatly increasing the number of available satellites. In addition, the compensation and fusion of multiple frequency point observations tracked by the same satellite can effectively identify gross error observations and improve the accuracy of observations. More available satellites can provide a better satellite distribution configuration, and the increased redundant observations are conducive to RAIM (Receiver Autonomous Integrity Monitoring) detection, effectively improving the accuracy and availability of GNSS receiver PVT solutions.

[0144] Furthermore, when the number of effective satellites is further reduced, the The parameters reduce the number of unknowns in the joint positioning solution. At the same time, the pseudorange observations with the same clock error reference are further used for observation RAIM detection, which further improves the continuity and reliability of the PVT solution in harsh environments.

[0145] Multiple GNSS systems can significantly increase the number of satellites visible to users, and multi-system joint positioning has become the basic mode of GNSS application. Since different GNSS satellite navigation systems use different signal systems, carrier frequencies, time systems, coordinate systems and different constellation compositions, there is an inter-system bias ISB between satellite observations of different GNSS systems tracked by the same receiver user. ISB bias is a factor that must be considered in multi-system joint solution. When the receiver tracks and copies signals, the hardware delay bias of signals of different frequencies passing through different channels is different. When multi-frequency observations are used simultaneously, the inter-frequency bias IFB needs to be considered.

[0146] For multi-system multi-frequency user receivers, the inter-system bias ISB and inter-frequency bias IFB have good stability in the short term. When the measurement environment is good, the stable inter-system ISB value and inter-frequency IFB value are estimated using good quality observations. In severe occlusion, interference and other environments, the estimated prior ISB and IFB are used for compensation and fusion, directly providing more fused optimal observations and redundant information, directly improving the accuracy and availability of PVT solution.

[0147] In this example, the multi-system multi-frequency GNSS receiver simultaneously tracks the pseudorange, Doppler, and carrier observation information of the GPS dual-frequency L1, L2, and the BDS triple-frequency B1, B2, and B3.

[0148] The technical solution for PVT calculation of a multi-system multi-frequency GNSS receiver in the embodiment of the present invention is also applicable to dual-frequency, triple-frequency, or more frequency signals, and is not limited to GNSS receivers and antennas. The GNSS receiver antenna is not limited to receiving single-frequency or multi-frequency signals, including all satellite signals that can be used for navigation and positioning. The receiver is also not limited to a multi-system joint GNSS receiver, including GPS, GLONASS, GALILEO, BDS, QZSS and any navigation and positioning satellite system that can forward satellite signals.

[0149] Figure 2 This is a flow chart of a method for improving PVT performance of a multi-system multi-frequency GNSS receiver in an embodiment of the present application. Figure 2 As shown, including:

[0150] Get the observation values ​​of multi-system multi-frequency GNSS users in the current epoch;

[0151] The first detection unit performs tracking status detection on the GPS dual-frequency L1 and L2 frequency point observation quantities; if the tracking of the two frequency points L1 and L2 of the GPS multiple satellites is detected to be good, the detection is passed;

[0152] If the first test unit passes:

[0153] The first IFB calculation unit calculates the IFB of each GPS satellite with good dual-frequency tracking for all satellites with L1 as the reference frequency point. L2 And perform validity detection, and use multiple valid satellites to calculate the optimal IFB between GPS frequencies in the current epoch L2 value;

[0154] The second IFB calculation unit calculates the optimal IFB of the first IFB calculation unit. L2 value, compared with the previous period Perform validity check and use the current optimal value IFB that has passed the test L2 Filter Update value and save it; according to the single epoch detection state or the continuous multiple epoch detection deviation state, the filter coefficient is adjusted to control The size of the update;

[0155] Furthermore, when the second IFB calculation unit performs the calculation for the first time, Initialize the value and start The value is initialized to the valid IFB calculated and first passed through the test L2 .

[0156] Similarly, BDS takes B1 as the reference frequency point and calculates the BDS system B2 and B3 frequencies according to the above steps.

[0157] The first fusion pseudorange calculation unit calculates the L2 frequency pseudorange observation of the i-th satellite of the GPS system conduct Correction, obtain the pseudo-range observation of L2 frequency point with the same clock error reference as L1 frequency point The observations of the i-th satellite Perform fusion calculation to obtain the optimal value of L1 frequency point Similarly, for the i-th BDS satellite Perform fusion calculation to obtain the optimal value of B1 frequency point

[0158] The second detection unit performs conditional detection on the available pseudorange observations obtained by the first fusion calculation unit; if the total number of valid satellites detected is small and there is a valid satellite in the second ISB calculation unit, If the test fails, the test will fail; otherwise, the test will pass;

[0159] If the second detection unit passes the test:

[0160] The first positioning solution unit performs joint positioning solution on the optimal value of the fusion pseudo-range of the GPS and BDS systems of the first fusion calculation unit to obtain the user position and the receiver clock difference value of each system;

[0161] The first ISB calculation unit calculates the receiver clock difference of the GPS and BDS systems obtained by the first positioning solution unit to calculate the ISB deviation between the two systems in the current epoch. Bds_Gps ;

[0162] The second ISB calculation unit calculates the current epoch ISB calculated by the first ISB calculation unit Bds_Gps , compared with the previous period Perform validity check, using the current epoch ISB that passes the test Bds_Gps Filter Update value and save it; according to the single epoch detection state or the continuous multiple epoch detection deviation state, the filter coefficient is adjusted to control The size of the update;

[0163] If the second detection unit fails the test:

[0164] The second fusion pseudorange calculation unit calculates the optimal value of the B1 frequency point of the BDS ith satellite obtained by the first fusion calculation unit. conduct Correction, obtain the pseudo-range observation with the same clock error reference as the GPS system L1 frequency point

[0165] The second positioning solution unit obtains the pseudo-range observation of the same clock error reference obtained by the second fusion calculation unit. Perform positioning calculation to obtain user position and receiver clock error;

[0166] If the first detection unit fails, the first fusion calculation unit processes the following two situations and directly uses the first positioning solution unit for positioning solution;

[0167] Case 1: If the GPS system L2 frequency If the first fusion calculation unit is effective, the i-th satellite Perform normal fusion to obtain the optimal value of the L1 frequency point At this time, if one of the frequency point observations is poorly detected or lost, its weight w = 0;

[0168] Case 2: If the GPS system L2 frequency Invalid if If exists, then the first fusion computing unit like If it does not exist, the first fusion calculation unit removes the satellite;

[0169] Similarly, the optimal value of the B1 frequency point is obtained by fusion calculation for the i-th BDS satellite according to case 1 or case 2.

[0170] The first positioning solution unit obtains the optimal value of the fused pseudorange of the GPS and BDS systems of the first fused pseudorange calculation unit to perform joint positioning solution, and obtains the user position and the receiver clock difference value of each GNSS system;

[0171] The first fusion Doppler calculation unit directly calculates the Doppler observation of the GPS i-th satellite Perform fusion calculation to obtain the optimal Doppler value of the i-th satellite Similarly, for the jth BDS satellite Fusion calculation of Doppler optimal value

[0172] The first speed measurement and solution unit obtains the optimal value of the GPS and BDS system fusion Doppler of the first fusion Doppler calculation unit to perform speed measurement and solution, and obtains the user speed and the receiver clock drift value.

[0173] Figure 3 FIG. 1 is a schematic diagram of the structure of a device for improving PVT performance of a multi-system multi-frequency GNSS receiver according to an embodiment of the present invention. Figure 3As shown, it includes: a measurement information acquisition step, an inter-frequency deviation IFB calculation step, an IFB compensated multi-frequency pseudorange fusion step, an IFB compensated pseudorange joint positioning step, an inter-system deviation ISB calculation step, an ISB compensated multi-system pseudorange fusion step, an ISB compensated pseudorange positioning solution step, a multi-frequency Doppler fusion step, and a fused Doppler speed measurement solution step.

[0174] A measurement information acquisition step, for acquiring observation values ​​of multi-system multi-frequency GNSS users in the current epoch;

[0175] The inter-frequency deviation IFB calculation steps are used to solve the inter-frequency deviation IFB between two frequency points of the same satellite in the GNSS system, and obtain the stable inter-frequency deviation value between the two frequency points over a period of time.

[0176] IFB compensates for the multi-frequency pseudorange fusion step, which is used for multiple frequency points of the i-th satellite in the GNSS system. After compensation, multiple frequency point pseudorange observations are fused to obtain the optimal pseudorange value of the satellite.

[0177] IFB compensated pseudorange joint positioning steps for the optimal pseudorange values ​​of each satellite in different GNSS systems Perform joint calculation to obtain user coordinates and receiver clock differences of each GNSS system;

[0178] The inter-system bias ISB calculation steps are used to solve the clock bias ISB between two different GNSS systems in the same epoch to obtain a stable inter-system bias value over a period of time.

[0179] ISB compensates for the multi-system pseudorange fusion step, used for the optimal pseudorange value of the i-th satellite in different GNSS systems conduct Compensation, to obtain pseudo-range observations of non-GPS satellites with the same clock error reference as the GPS system

[0180] ISB compensated pseudorange positioning solution steps, used for pseudorange observations of each satellite with the same clock error reference as GPS Obtain user coordinates and user receiver clock difference;

[0181] The multi-frequency Doppler fusion step is used to fuse the Doppler observations of multiple frequencies of each satellite in the GNSS system to obtain the optimal Doppler value of each satellite

[0182] Fusion Doppler velocity measurement solution steps for optimal Doppler values ​​of each satellite in each GNSS system Perform joint calculation to obtain user speed and receiver clock deviation.

[0183] Compared with the prior art, in the multi-system multi-frequency GNSS PVT solution, the present application maintains the calculation of the deviations IFB between different frequencies and ISB between different systems based on the short-term stability characteristics of the inter-frequency deviations IFB within each GNSS system when signal tracking is stable. When signal tracking is unstable due to occlusion, interference, severe multipath, etc., for satellites whose main positioning frequency tracking is lost or whose main frequency measurement values ​​have gross errors, the other valid frequencies of the satellite are compensated to the main frequency using the already calculated stable IFB. If the satellite tracks multiple frequencies at the same time, multiple verified valid compensated frequency observations are further fused to participate in the positioning solution. The fused observations can further weaken measurement errors and identify gross errors, and can greatly increase the number of available satellites and redundant observation information. In addition, when the number of valid satellites is further reduced, the already acquired inter-system frequency deviations between different systems can be used to obtain the main frequency deviations. Parameters reduce the dimensionality of the joint localization solution.

[0184] This application makes full use of the observation information of multi-system and multi-frequency signals, which can greatly improve the number and quality of available observations in complex scenarios. The compensated pseudorange is further used for RAIM detection without adding additional state quantities, effectively improving the accuracy and availability of PVT solutions of GNSS receivers, especially the continuity of PVT solutions in harsh environmental conditions such as urban canyons.

[0185] An embodiment of the present application provides a storage medium, in which a computer program is stored, wherein the computer program is configured to execute any of the methods described above when running.

[0186] An embodiment of the present application provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute any of the methods described above.

[0187] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the methods disclosed above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical components; for example, a physical component may have multiple functions, or a function or step may be performed by several physical components in cooperation. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or temporary medium). As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those of ordinary skill in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

Claims

1. A satellite positioning method in a GNSS system, characterized in that: include: Select one frequency point L1 from the available frequency points of satellites in the same GNSS system as the reference frequency point, and the other frequency points as the target frequency points L n , and the number of target frequency points n≥1; Get each target frequency point L n The stable value of the frequency deviation relative to the reference frequency L1 The stable value of the inter-frequency deviation is obtained by weighted calculation of the optimal value of the inter-frequency deviation of the target frequency point at the current moment and the stable value of the inter-frequency deviation at the previous moment; the optimal value of the inter-frequency deviation is obtained by weighted average of the inter-frequency deviation values ​​of each valid satellite at the target frequency point at the current moment; According to the i-th satellite at the target frequency point L n The pseudorange observation value of The stable value of the sum frequency deviation Calculate the pseudorange fusion value of the i-th satellite at the reference frequency point L1; the pseudorange fusion value is the pseudorange observation value of the reference frequency point L1 With the target frequency L n Pseudorange correction value Weighted average to obtain; the pseudo-range correction value of the target frequency point is the pseudorange observation value of the target frequency point Frequency deviation stability value difference; After obtaining the pseudorange fusion value corresponding to the reference frequency point L1 of the satellite, the positioning operation is performed using the pseudorange fusion value corresponding to the reference frequency point L1.

2. The method according to claim 1, characterized in that The pseudorange fusion value is obtained by the following method, including: Using T k The target frequency L at the moment n The corresponding stable value of the frequency deviation Correct the target frequency L of the i-th satellite n The pseudorange observation value of Get the target frequency L n Pseudorange correction value relative to the reference frequency point L1 Pseudorange observation value of reference frequency point L1 of the i-th satellite And the target frequency L n Pseudorange correction value Perform fusion calculation to obtain the pseudorange fusion value of the i-th satellite at the reference frequency point L1 3. The method according to claim 1, characterized in that T is obtained by k Time target frequency L n The corresponding stable value of the frequency deviation include: Determine T k The target frequency L at the moment n The optimal value of inter-frequency deviation IFB Ln (T k ); Determine T k The optimal value of inter-frequency deviation IFB at time Ln (T k ) corresponds to the weight W Tk ; Using T k-1 The stable value of the frequency deviation at the moment T k The optimal value of the time-frequency deviation IFB Ln (T k ) and its weight W Tk , and get T k Stable value of the time-frequency deviation 4. The method according to claim 3, characterized in that The target frequency L at time T0 is obtained by the following method n The corresponding stable value of the frequency deviation include: The target frequency L of each satellite at time T0 n The frequency deviation value between the reference frequency point L1 and the corresponding preset threshold Make comparisons; Select a frequency deviation value less than At least two satellites are used as the target frequency point L at time T0 n effective satellites; According to the target frequency L at time T0 n The effective satellite frequency deviation value is used to determine the target frequency point L at time T0. n The stable value of the frequency deviation 5. The method according to claim 4, characterized in that T is obtained by k The target frequency L at the moment n The optimal value of inter-frequency deviation IFB Ln (T k ),include: Calculate T for each satellite k Time target frequency L n The frequency deviation value With T k-1 The target frequency L in the time period n The stable value of the frequency deviation The difference between them is used to obtain the inter-frequency deviation calibration value; Select the satellite whose inter-frequency deviation check value meets the preset first value condition as T k The target frequency L at the moment n effective satellites; If the number of valid satellites selected is greater than the preset threshold, then according to T k The effective satellite at the target frequency L n The frequency deviation value is determined by T k Time target frequency L n The optimal value of inter-frequency deviation IFB Ln (T k ); otherwise, for T k-1 Time deviation stable value Perform a reset.

6. The method according to claim 1, characterized in that One GNSS system among at least two global satellite navigation systems GNSS is used as a reference system A, and the other one or at least two GNSS systems are used as a target system B. The method includes: Obtain the pseudorange fusion values ​​of satellites in each GNSS system; Determine T k The stable value of the inter-system deviation of at least one target system B relative to the reference system A at the moment Using T k The stable value of the system deviation at the moment Correct the pseudo-range fusion value of the k-th satellite of the target system B to obtain the pseudo-range fusion value of the k-th satellite with the same clock error reference as the reference system after correction; Using the pseudorange fusion values ​​of satellites in at least two GNSS systems with the same clock error reference, T k Positioning operation at the moment.

7. The method according to claim 6, characterized in that T is obtained by k The stable value of the inter-system deviation corresponding to the target system at the moment include: Get T k The receiver clock difference of the target system at the reference frequency of its system at the moment T k The receiver clock error of the time reference system at the reference frequency of the system; Calculate the difference between the receiver clock error corresponding to the target system and the receiver clock error corresponding to the reference system as T k The optimal value of the inter-system deviation of the target system at time t; Determine T k The weight corresponding to the optimal value of the inter-system deviation of the target system at the moment; Using T k-1 The stable value of the system deviation at time T k The optimal value of the system deviation and its weight at time T k The stable value of the deviation between systems at any time.

8. The method according to claim 6, characterized in that T is obtained by k Time target frequency L n The optimal value of the inter-system deviation includes: Calculate T k The estimated value of the inter-system deviation of the target system at time T k-1 The difference of the system deviation filter value of the target system B at the moment is used to obtain the inter-system deviation check value; If the inter-system deviation check value meets the preset second value condition, then calculate T k The stable value of the deviation between systems at the moment; otherwise, for T k-1 The stable value of the inter-system deviation of the target system is reset at that moment.

9. The method according to any one of claims 1 to 8, characterized in that: The method further comprises: Obtain the Doppler observation values ​​of all valid frequency points of the i-th satellite of each GNSS system; Determine the weight of the Doppler observation value of each frequency point of the i-th satellite; Using Doppler observations and their respective weights, the optimal value of the Doppler observations is calculated by fusion. Using the optimal value of Doppler observations fused from each satellite Execute T k Speed ​​measurement operation at all times.

10. A storage medium, characterized in that: The storage medium stores a computer program, wherein the computer program is configured to execute the method according to any one of claims 1 to 9 when executed.

11. An electronic device comprising a memory and a processor, characterized in that: A computer program is stored in the memory, and the processor is configured to run the computer program to perform the method according to any one of claims 1 to 9.

12. A satellite positioning device in a multi-GNSS system, characterized in that: An electronic device as claimed in claim 11 is provided.

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