CN114509796B - A satellite positioning method and device in a GNSS system - Google Patents
A satellite positioning method and device in a GNSS system Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
- G01S19/43—Determining position using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
- G01S19/44—Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
- G01S19/25—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS
- G01S19/256—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS relating to timing, e.g. time of week, code phase, timing offset
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
- G01S19/25—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS
- G01S19/258—Acquisition or tracking or demodulation of signals transmitted by the system involving aiding data received from a cooperating element, e.g. assisted GPS relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
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Abstract
本申请实施例公开了一种GNSS系统中卫星定位方法和装置。所述方法包括：从相同GNSS系统内卫星的可用频点中选择一个频点L1作为基准频点，其他频点作为目标频点Ln，且目标频点的数量n≥1；获取每个目标频点Ln相对于基准频点L1的频间偏差的稳定值根据第i颗卫星在目标频点Ln的伪距观测值和频间偏差的稳定值计算第i颗卫星在基准频点L1的伪距融合值；在得到卫星在基准频点L1对应的伪距融合值后，利用基准频点L1对应的伪距融合值进行定位操作。
The embodiment of the present application discloses a satellite positioning method and device in a GNSS system. The method comprises: selecting a frequency point L1 from available frequency points of satellites in the same GNSS system as a reference frequency point, and other frequency points as target frequency points Ln , and the number of target frequency points n≥1; obtaining a stable value of the inter-frequency deviation of each target frequency point Ln relative to the reference frequency point L1; According to the pseudo-range observation value of the i-th satellite at the target frequency point Ln The stable value of the sum frequency deviation 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, use the pseudorange fusion value corresponding to the reference frequency point L1 to perform positioning operation.
Description
Technical Field
The embodiment of the application relates to the field of information processing, in particular to a satellite positioning method and device in a GNSS system.
Background
PVT (Position Velocity Time, location, speed, and time) solution is a basic service provided by the global satellite navigation system (Global Navigation SATELLITE SYSTEM, GNSS) worldwide. With the rapid development of GNSS systems such as a global positioning system (Global Positioning System, GPS), a global satellite navigation system (Global Navigation SATELLITE SYSTEM, GLONASS), galileo, a beidou satellite navigation system (Bei Dou Navigation SATELLITE SYSTEM, BDS), more available satellites provide more reliable positioning, speed measurement and time service for users in each area. The current PVT is widely applied to relevant fields such as vehicle navigation, unmanned aerial vehicle aircrafts, agricultural plant protection, time service and the like, and the PVT reliability and precision requirements on complex environments such as urban canyons, number shielding, signal interference and the like are higher and higher.
In a complex shielding scene, the number of visible satellites is increased mainly through a plurality of GNSS systems, or the continuity of service is improved through the increased observation information by combining with sensors such as inertia and barometer. However, the limited number of visible satellites in the occlusion scene, the increased cost of the auxiliary sensor and the accumulated errors do not effectively utilize the advantages of the GNSS system multi-frequency signals.
Along with the modernization of a GPS system, GPSIII satellites can provide 8 navigation signals, namely civil L1C/A, L1C, L C, L C, military L1P (Y), L2P (Y) and L1M, L2M, and after the global networking of a BDS system is completed, BD3 satellites can simultaneously provide B1I, B3I, B1C, B a, B2B and other multi-frequency signals. The existing research shows that no frequency point navigation signal shows absolute advantages on all scenes and various performance indexes. Due to the existence of Inter-System Bias (ISB) and Inter-Frequency Bias (IFB), the observed values of multiple systems and multiple Frequency points cannot be directly combined at the same time when single-point positioning (SPP (Single Point Position, SPP)) positioning.
At present, the research of GNSS multi-system multi-frequency mainly surrounds the aspects of quick satellite selection algorithm, single-double-frequency positioning selection in the system and the like. After the optimal frequency point of each system is selected, the satellite observation values of the other frequency points are not used. Under complex scenes such as urban canyons, tree shielding and the like, the number and quality of available observation values of individual frequency points of each system can be drastically reduced, and large positioning errors and even discontinuous positioning are caused. This application has a major disadvantage in terms of availability and robustness of GNSS receivers, and it is desirable to provide more efficient measures to solve the above-mentioned problems.
Disclosure of Invention
In order to solve any technical problem, the embodiment of the application provides a satellite positioning method and device in a GNSS system.
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:
Selecting one frequency point L 1 from available frequency points of satellites in the same GNSS system as a reference frequency point, and using other frequency points as target frequency points L n, wherein the number n of the target frequency points is more than or equal to 1;
Obtaining a stable value of the inter-frequency deviation of each target frequency point L n relative to the reference frequency point L 1
According to the pseudo-range observation value of the ith satellite at the target frequency point L n Stable value of sum inter-frequency deviationCalculating a pseudo-range fusion value of the ith satellite at a reference frequency point L 1;
And after the pseudo-range fusion value corresponding to the satellite at the reference frequency point L 1 is obtained, positioning operation is carried out by utilizing the pseudo-range fusion value corresponding to the reference frequency point L 1.
A storage medium having a computer program stored therein, wherein the computer program is arranged to perform the method described above when run.
An electronic device comprising a memory having stored therein a computer program and a processor arranged to run the computer program to perform the method described above.
A satellite positioning device in a GNSS system is provided with the electronic device.
One of the above technical solutions has the following advantages or beneficial effects:
By estimating and compensating IFB between different frequency points in the same GNSS system, the pseudo-range observation values of a plurality of frequency points are fused, so that the pseudo-range observation values fused by all satellites in the same system have the same clock difference reference as the reference frequency points, and all the fused pseudo-range observation values can be directly used for positioning, and the quantity and quality of the available observation values can be effectively increased.
Additional features and advantages of embodiments of the application will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of embodiments of the application. The objectives and other advantages of embodiments of the application may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The accompanying drawings are included to provide a further understanding of the technical solution of the embodiments of the present application, and are incorporated in and constitute a part of this specification, illustrate and explain the technical solution of the embodiments of the present application, and not to limit the technical solution of the embodiments of the present application.
FIG. 1 is a flowchart of a satellite positioning method in a multi-GNSS system according to an embodiment of the present application;
FIG. 2 is a flowchart illustrating a method for improving PVT performance of a multi-system multi-frequency GNSS receiver according to an embodiment of the present application;
FIG. 3 is a schematic diagram illustrating an apparatus for improving PVT performance of a multi-system multi-frequency GNSS receiver according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the embodiments of the present application will be described in detail hereinafter with reference to the accompanying drawings. It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be arbitrarily combined with each other.
Fig. 1 is a flowchart of a satellite positioning method in a multi-GNSS system according to an embodiment of the present application. As shown in fig. 1, the method includes:
Step 101, selecting one frequency point L 1 from available frequency points of satellites in the same GNSS system as a reference frequency point, and using other frequency points as target frequency points L n, wherein the number n of the target frequency points is more than or equal to 1;
102, obtaining a stable value of the inter-frequency deviation of each target frequency point L n relative to the reference frequency point L 1
Step 103, according to the pseudo-range observation value of the ith satellite at the target frequency point L n Stable value of sum inter-frequency deviationCalculating a pseudo-range fusion value of the ith satellite at a reference frequency point L 1;
104, after obtaining a pseudo-range fusion value corresponding to the satellite at the reference frequency point L 1, performing positioning operation by using the pseudo-range fusion value corresponding to the reference frequency point L 1;
According to the method provided by the embodiment of the application, the pseudo-range observation values of a plurality of frequency points are fused by estimating and compensating the IFB between different frequency points in the same GNSS system, so that the pseudo-range observation values fused by all satellites in the same system have the same clock difference reference as the reference frequency point, and all the fused pseudo-range observation values can be directly used for positioning, and the quantity and quality of the available observation values can be effectively increased.
The following describes the method provided by the embodiment of the application:
The method provided by the embodiment of the application improves the related technology as follows, and comprises the following steps:
A. By estimating and compensating IFB between different frequency points in the same GNSS system, pseudo-range observation values of a plurality of frequency points are fused, so that the pseudo-range observation values fused by all satellites in the same system have the same clock difference reference as the reference frequency points, and the quantity and quality of available observation values are effectively increased;
B. Estimating and compensating ISB between different systems by using the clock difference relation between different GNSS systems, so that receiver clock difference items of pseudo-range observation values of all systems share one, and the number of unknowns is reduced;
C. When the Doppler observation values are used for positioning, a plurality of Doppler observation values in all GNSS systems are fused, so that the number of available observation values is effectively increased, and the quality of the observation values is optimized.
The following describes the above improvement one by one:
The scheme provided by the embodiment of the application can improve the PVT resolving performance of the multi-system multi-frequency GNSS, wherein the GNSS system is provided with a plurality of satellites and a plurality of frequency points.
A. Fusing a plurality of frequency point pseudo-range observation values in the same GNSS system, including:
in an example embodiment, the pseudorange fusion value is obtained by:
Stable value of inter-frequency deviation corresponding to target frequency point L n at time T k Correcting pseudo-range observation value of target frequency point L n of ith satelliteObtaining a pseudo-range correction value of the target frequency point L n relative to the reference frequency point L 1
Pseudo-range observation value of reference frequency point L 1 of ith satellitePseudo-range correction value of target frequency point L n Fusion calculation is carried out to obtain a pseudo-range fusion value of the ith satellite at the reference frequency point L 1
The stable value of the inter-frequency deviation corresponding to the target frequency point L n at the time T k is obtained by the following methodComprising the following steps:
determining an inter-frequency deviation optimal value IFB Ln(Tk of a target frequency point L n at the moment T k;
Determining a weight W Tk corresponding to an inter-frequency deviation optimal value IFB Ln(Tk) at the moment T k;
using stable values of inter-frequency deviations at time T k-1 Optimal value IFB Ln(Tk) of the inter-frequency deviation at time T k and weight W Tk thereof, to obtain a stable value of the inter-frequency deviation at time T k
The stable value of the inter-frequency deviation corresponding to the target frequency point L n at the time T 0 is obtained by the following methodComprising the following steps:
The inter-frequency deviation value of the target frequency point L n and the reference frequency point L 1 of each satellite at the moment T 0 is matched with the corresponding preset threshold Comparing;
Selecting the inter-frequency deviation value to be smaller than At least two satellites of the satellite (A) are used as effective satellites of a target frequency point L n at the moment T 0;
According to the inter-frequency deviation value of the effective satellite of the target frequency point L n at the moment T 0, determining the stable value of the inter-frequency deviation at the moment T 0
The optimal value IFB Ln(Tk of the inter-frequency deviation of the target frequency point L n at the time T k is obtained by:
Calculating the inter-frequency deviation value of the target frequency point L n at the moment T k of each satellite Stable value of inter-frequency deviation from target frequency point L n in T k-1 th periodObtaining a difference value between the two frequencies to obtain an inter-frequency deviation check value;
Selecting a satellite with an inter-frequency deviation check value meeting a preset first value condition as an effective satellite of a target frequency point L n at the moment T k;
If the effective satellites larger than the preset number threshold are selected, determining an inter-frequency deviation optimal value IFB Ln(Tk of a target frequency point L n at the moment T k according to the inter-frequency deviation value of the effective satellites at the moment T k at the target frequency point L n, otherwise, stabilizing the inter-frequency deviation value at the moment T k-1 And resetting.
Taking the reference frequency point as the first frequency point L 1 and the target frequency point as the second frequency point L 2 as examples for explanation:
a1, acquiring pseudo-range models of two different frequency point observation values of the same GNSS satellite;
The pseudo-range observation equation of the ith satellite at the first frequency point L 1 and the second frequency point L 2 is as follows:
Wherein, The pseudo-range observation values of the first frequency point L 1 and the second frequency point L 2 are represented, r represents the geometric distance between the receiver and the satellite, c represents the light speed, deltat L1 represents the clock difference of the first frequency point receiver, deltat s represents the clock difference of the first frequency point satellite, T GD is the group delay of a satellite end signal, I L1 represents the ionosphere error of the first frequency point, T represents the troposphere error, epsilon L1、εL2 represents the observation value noise, gamma represents the square of the ratio between the frequency f 1 of the first frequency point L 1 and the frequency f 2 of the first frequency point L 2, namely gamma= (f 1/f2)2;IFBL2 represents the clock difference deviation value of the receiver between the second frequency point L 2 and the first frequency point L 1, and I is the satellite number.
The right part of the pseudo-range model is eliminated through the model, deltat s、TGD related to satellites is corrected through system broadcasting parameter modeling, I L1 is estimated by a Klobuchar model, T is estimated by a Saastamoinen model, multipath delay errors and measurement noise are generally reduced to a relatively small level through a carrier phase observed value smoothing pseudo-range observed value, and the influence of measurement noise epsilon is reflected through observed value quality in actual use and ignored in the model.
The geometric distance r is linearized, expressed as:
r=r0-HxΔx-HyΔy-HzΔz (3)
Wherein r 0 is the geometric distance calculated by using the coordinate of the station and the satellite coordinates, H x、Hy、Hz is the unit vector from the coordinate of the station to the satellite sight direction, and Deltax, deltay and Deltaz are the user coordinates to be calculated.
Substituting the formula (3) into the formulas (1) and (2), and obtaining a measurement equation after conversion:
The left ρ L1、ρL2 above is the range value of the pseudorange measurement after model cancellation error, and the right is the position and clock difference to be solved.
Step A2, calculating an inter-frequency deviation IFB L2:
Step A21, obtaining inter-frequency offset values of all satellites simultaneously tracking a first frequency point L 1 and a second frequency point L 2;
subtracting (4) from formula (5) yields:
IFBL2＝ρL2-ρL1 (6)
For each satellite in the GNSS system which simultaneously tracks the first frequency point L 1 and the second frequency point L 2, calculating an inter-frequency deviation by using the method (6)
Step A22, determining an inter-frequency deviation optimal value IFB L2(Tk at the time of T k according to the inter-frequency deviation values of at least two satellites at the time of T k;
specifically, each effective satellite is calculated according to the information such as satellite altitude angle, frequency point observation value quality and the like Weight W i of the frequency band at the moment of T k and L 1、L2 is obtained after weighted averageInter-frequency deviation optimum IFB L2(Tk) of (a) as follows:
Equation (7) calculates the inter-frequency bias optimum value IFB L2(Tk at time T k, which is relatively stable over a period of time, as a residual ionospheric error, measurement noise, and multipath error after absorbing the single difference of the pseudo-ranges over the two frequencies.
Step A23, stabilizing the value of the inter-frequency deviation according to the time T k-1 The optimal value IFB L2(Tk) of the inter-frequency deviation calculated by the current kth epoch T k is filtered, and the stable value of the inter-frequency deviation at the moment T k is further obtained
Specifically, the weight W Tk of the inter-frequency deviation optimal value IFB L2(Tk) at the time T k is determined, wherein the weight W Tk at the time T k is determined according to the number and quality of the observed values of the inter-frequency deviation optimal value IFB L2(Tk) participating in calculation at the time;
Obtaining the inter-frequency deviation stable value in the T k period by utilizing the inter-frequency deviation stable value at the T k-1 moment and the weight W Tk at the T k moment
Specifically, the optimal value IFB L2(Tk) of the inter-frequency deviation at time T k is compared with the steady value of the inter-frequency deviation estimated in the previous periodFiltering operation is carried out, observation noise and multipath error are weakened, a stable inter-frequency deviation value between two frequency points at the moment T k is obtained, and a stable value of the inter-frequency deviation is obtainedAs formula (8):
Further, the validity detection is performed when IFB L2(Tk at time T k used in the weighting of equation (8) is performed for the stable characteristic of the inter-frequency offset IFB of the receiver. Obtained by IFB L2(Tk) and T k-1 Comparing, e.g. preferablyIs valid in range for rejecting IFB L2(Tk) values that deviate significantly or reset that have been estimated to be incorrectValues.
Equation (8) requires the first time the operation is performedInitializing, wherein the value is IFB L2 which is calculated by the formula (7) and is effective for first detection, and the IFB is taken as a stable value of the inter-frequency deviation at the time T 0 Using satellites at times T 0 When the validity is detected, the method willValue and preset thresholdComparing and eliminating the exceeding thresholdWill (F) beA value less thanWherein, a threshold value is presetAn empirical value set according to the difference between the first frequency point L 1 and the second frequency point L 2 is set at the time of the first start of the calculation. The step can initially detect the coarse difference observed value and improve the accuracy of calculating the inter-frequency deviation value IFB.
The detection is used for further improvementThe reliability of the estimated value is not described here in detail.
A24, utilizing the stable value of the inter-frequency deviation at the time T k Correcting the pseudo-range observation value of the second frequency point L 2 at the moment T k to obtain a pseudo-range correction value of the target frequency point L n relative to the reference frequency point L 1
Stable value of inter-frequency deviation obtained by the formula (8)Pseudo-range observation value of second frequency point L 2 of ith satellitePerforming inter-frequency deviation correction to obtain pseudo-range correction value
As can be seen by comparing formula (9) with formula (4), ρ L1 andThe required quantities are the user coordinate terms deltax, deltay and deltaz and the receiver clock difference term deltat L1.
Step A24, according to the pseudo-range correction valueAnd the pseudo-range observation value of the first frequency point L 1, obtaining a pseudo-range fusion value as a pseudo-range observation value used for positioning;
Using (9), the pseudo-range observation value of the second frequency point L 2 tracked by each satellite can be compensated to be the observation value with the same clock difference standard as the L 1 frequency point Calculating a corresponding weight value W 1、W2 according to the information such as the quality of the observed value of each frequency point, and fusing the observed values of the pseudo ranges to obtain a pseudo range fusion valueSee (10):
it should be noted that, n frequency points L 1、L2 of each GNSS system are dependent on the satellite broadcast signal, the receiver support frequency band, and the current signal tracking state. Ith satellite Ln frequency point Weights W n are based on pseudorange measurementsTracking quality and inter-frequency offset of (a)And further, if Ln frequency points are estimated comprehensivelyIf the value does not calculate the effective value, the weight W n =0.
The satellite broadcasting signals and the supporting frequency bands of all receivers are determined, and the quality difference of the observed values of all current frequency points is large due to the fact that the tracking states of the signals of all the frequency points are different. If the measurement value of the Ln frequency point of the ith satellite in the current epoch is lost, the corresponding value in the formula (5)Wn=0。
Furthermore, the clock difference reference frequency point L 1 is not limited to L 1, and the user may select other frequency points with better tracking states of each GNSS system according to the actual situation, which is not used to limit the protection scope of the present application.
Similarly, for n frequency points in the GNSS system, using equation (8), one can obtain
Similarly, for the observation values of n frequency points of the ith satellite in the GNSS system, fused pseudo-range fusion values can be obtained by using the formulas (9) and (10)
And (3) calculating pseudo ranges of the satellites of the GNSS systems of the current epoch after fusion by using the formula (11), carrying out joint calculation when the number of effective satellites of the systems is large, and acquiring the user position of the current epoch and the clock error of a receiver of the systems by a least square or Kalman filtering method.
B. Pseudo-range fusion calculation based on intersystem bias ISB compensation
When the pseudo-range compensated by the inter-frequency deviation IFB is jointly solved, a receiver clock error state quantity needs to be established for different GNSS systems. When the satellites of N GNSS systems are combined for positioning, N+3 unknowns need to be estimated, and at least not less than N+3 satellites are needed for positioning. In addition, after the rough satellite is removed in the interference scene, the number of available effective satellites in each system is only 1-2, the total number of positioning satellites is still less, and the pseudo-range error is possibly larger. At this time, only the traditional pseudo-range model or the IFB is used for compensating the pseudo-range model, so that the positioning reliability is poor and even the positioning is interrupted. Thus, the following solutions are proposed:
taking one of at least two GNSS systems as a reference system A and the other one or at least two GNSS systems as a target system B, and acquiring a pseudo-range fusion value of satellites in each GNSS system;
determining a stable value of the intersystem deviation of at least one target system B relative to said reference system A at time T k
Stable value using intersystem deviation at time T k Correcting the pseudo-range fusion value of the kth satellite of the target system B to obtain the pseudo-range fusion value of the same clock error reference as the reference system after the kth satellite is corrected;
And performing positioning operation at the time of T k by using the pseudo-range fusion values of satellites in at least two GNSS systems with the same clock difference reference.
The inter-system deviation stable value corresponding to the target system at the moment T k is obtained by the following methodComprising the following steps:
The method comprises the steps of acquiring the receiver clock difference of a target system at the moment T k at the reference frequency point of the target system at the moment T k;
Calculating the difference between the receiver clock difference corresponding to the target system and the receiver clock difference corresponding to the reference system to serve as an intersystem deviation optimal value of the target system at the moment T k;
determining a weight corresponding to an intersystem deviation optimal value of the target system at the moment T k;
And obtaining a stable value of the intersystem deviation at the moment T k by using the stable value of the intersystem deviation at the moment T k-1, the optimal value of the intersystem deviation at the moment T k and the weight thereof.
The method for obtaining the optimal value of the target inter-system deviation at the moment T k comprises the following steps:
Calculating the difference between the actual value of the inter-system deviation of the target at the moment T k and the stable value of the inter-system deviation of the target at the moment T k-1 to obtain a check value of the inter-system deviation;
If the system deviation check value accords with the preset second value condition, calculating the stable value of the system deviation at the moment T k, otherwise, resetting the stable value of the system deviation of the target system at the moment T k-1.
Taking a reference system as a GPS system and a target system as a BDS system as an example for explanation:
Step B1, acquiring a system deviation stable value of the BDS system relative to the GPS system at the time T k on each reference frequency point;
In the same epoch, the clock differences of the receivers of the GPS and BDS systems have deviation, and the clock difference reference frequency points of the GPS and BDS systems are assumed to be L 1、B1 respectively, and according to the formula (4), the observation equations of the satellites of the GPS and BDS systems are expressed as follows:
ρL1＝-Hx_L1Δx-Hy_L1Δy-Hz_L1Δz+cΔtGps_L1 (12)
ρB1＝-Hx_B1Δx-Hy_B1Δy-Hz_B1Δz+cΔtBds_B1 (13)
When the GPS and BDS systems have pseudo-range observation values with good signals, the receiver Zhong Chazhi delta t Gps_L1、ΔtBds_B1 of the GPS and BDS systems can be obtained through joint calculation, and at the moment, the deviation ISB Bds_Gps between the two systems of the current epoch is further obtained, wherein the formula (14) is as follows:
ISBBds_Gps＝ΔtBds_B1-ΔtGps_L1 (14)
The intersystem deviation ISB Bds_Gps calculated by equation (14) is mainly caused by systematic differences of two GNSS systems, and absorbs part of the residual model error, so that the stability of ISB Bds_Gps value of the same receiver is better in a short period. Further calculate the weight W Tk according to the number and quality of the observed values of the T k epoch participation calculation ISB Bds_Gps(Tk) and the previous epoch Filtering operation is carried out, current epoch observation noise and multipath error are weakened, and a stable intersystem deviation stable value is obtained in a period of timeSee (15):
Further, for the stable characteristic of the inter-system clock bias ISB, validity detection is performed when (15) weighting the actual inter-system bias value ISB Bds_Gps(Tk) of the current T k epoch, and ISB Bds_Gps(Tk) is estimated from the previous period of time Comparing to eliminate ISB Bds_Gps(Tk) values with large current epoch deviations or estimation errors before resetValues. The detection is used for further improvementThe reliability of the estimated value is not intended to limit the scope of the present application.
The method can be used for calculating GPS between each system and a reference system for a plurality of GNSS systemsFurthermore, the reference system is not limited to GPS, and the user may select other systems with better tracking status according to actual situations, which is not intended to limit the scope of the present application.
Step B2, correcting a pseudo-range fusion value of the BDS system at a reference frequency point by using a stable value of the system deviation at the moment T k;
When the total effective satellite number is less, fusing pseudo-range fusion value obtained by fusing the ith satellite of BDS system obtained in formula (11) Calculated further by the formula (15)Correcting the deviation between systems, and compensating the pseudo-range observation value of the ith BDS satelliteRestoring the clock difference reference which is the same as the frequency point of the GPS system L 1, and the following formula (16):
Comparing equation (16) with equations (12), (4), after compensation AndThe required quantities are the user coordinate terms delta x, delta y and delta z and the receiver clock error term delta t L1, and only the clock error of the GPS is contained.
Using equation (15), the individual systems can be determined similarlyCompensating the pseudo-range observation values of GLONASS, galileo and other systems into pseudo-range observation values with the same clock error reference as the GPS system L 1 frequency point through the method (16)The receiver clock differences of different GNSS systems are converted to the clock differences of the GPS system, and the current unknown number only comprises a position item and one receiver clock difference, so that the number of the unknown number of the clock differences is reduced, and the positioning redundancy is improved.
C. Fusing Doppler information:
Using all the active satellites of the plurality of GNSS systems, a doppler velocimetry operation at time T k is performed, including:
doppler observation values of all effective frequency points of the ith satellite of each GNSS system are obtained;
determining the weight of each frequency point Doppler observation value;
Fusion calculation of optimal value of Doppler observed value by using Doppler observed value and weight value
Using the optimal value of Doppler observations for all satellitesAnd executing Doppler velocimetry operation at the time T k.
The Doppler observation is generated by the relative motion speed of the satellite relative to the user, and the Doppler measurement model of the kth satellite is expressed as a formula (17) for all satellites tracked in the same epoch:
Wherein: The method is characterized by comprising the steps of obtaining a Doppler observation value, wherein H is a unit vector from a station coordinate to a satellite sight line direction, and v k is a velocity vector of a satellite k; v u is the receiver velocity vector to be solved; the clock drift value of the receiver to be calculated is represented by c, which is the speed of light, and the unit is m/s.
The satellite related speed and the clock drift value are calculated by navigation message parameters, the satellite related terms are subtracted from the equation (17) and linearized, and an observation equation is established:
Where H x、Hy、Hz is the component of the unit vector H of the station coordinates to the satellite line of sight and v x、vy、vz is the component of the receiver velocity v u to be resolved.
According to equation (18), there is no systematic error in Doppler measurements of different GNSS systems and different frequency points. For each frequency point L 1、L2 of the ith satellite once again, ln Doppler observationsCalculating the weight W 1、W2…Wn of the Doppler measured value according to the quality of each frequency point, and directly calculating the optimal value of the fused Doppler observed value by using the formula (19)
And using the fused pseudo-range and Doppler measured values calculated by each satellite by using the method for positioning and speed measurement calculation. According to the law of variance propagation, the measured noise of the observation value calculated after the n frequency points are fused is reduced to a single observation valueMultiple times.
It should be noted that, in the present application, there are more mature methods for calculating the validity detection and the weight W i. General validity detection includes consistency detection of a plurality of values of the same physical meaning, numerical stability detection over a continuous time sequence, and range detection of associated empirical values. Similarly, the weight W i calculation is typically expressed as the inverse of the measurement variance of the corresponding observations, while the measurement variance of the satellite observations at each frequency point is typically expressed as a function of its satellite altitude, CN0, continuous tracking time, observation residuals, typical model error values, and so forth. Other methods may be used for the validity detection and the weight W i calculation, which are not limited herein, and related methods and applications belong to the known techniques of those skilled in the art, and are not described herein again, nor are they used to limit the protection scope of the present application.
In practical application, only the frequency points are estimatedAfter the value, when complex scene signals such as various shielding, interference, serious multipath and the like are unstable, a satellite can pass through only by tracking any frequency point of the satelliteAnd after correction, the satellite positioning calculation is participated in, and the state quantity is not required to be increased, so that the number of available satellites is greatly increased. And the observation values of a plurality of frequency points tracked by the same satellite at the same time are compensated and then fused, so that the coarse-difference observation value can be effectively identified and the accuracy of the observation value can be improved. More available satellites can provide better satellite distribution configuration, and the increased redundant observation values are beneficial to RAIM (Receiver Autonomous Integrity Monitoring, autonomous integrity monitoring) detection, so that the PVT resolving precision and usability of the GNSS receiver are effectively improved.
And, when the effective satellite number is further reduced, passing through the acquired intersystemThe parameters reduce the number of unknowns calculated by joint positioning, and meanwhile, the pseudo-range observation values with the same clock error reference are further used for detecting the observation value RAIM, so that the continuity and reliability of PVT calculation are further improved when the environment is bad.
Multiple GNSS systems can significantly increase the number of satellites visible to the user, and multi-system joint positioning has become a fundamental mode of GNSS application. Because different GNSS satellite navigation systems are composed of different signal systems, carrier frequencies, time systems, coordinate systems and different constellations, inter-system bias ISB exists in satellite observables of different GNSS systems tracked by the same receiver user, and the ISB bias is a factor which must be considered in multi-system joint calculation. When the receiver tracks and replicates signals, the hardware delay deviation of the signals with different frequencies passing through different channels is different, and the inter-frequency deviation IFB needs to be considered when the multi-frequency observers are used simultaneously.
For the multi-system multi-frequency user receiver, the intersystem deviation ISB and the intersystem deviation IFB have better stability in a short period. When the measuring environment is good, stable inter-system ISB values and inter-frequency IFB values are estimated by using the observables with good quality, and when environments such as severe shielding and interference are caused, compensation and fusion are carried out through estimated prior ISB and IFB, more fused optimal observables and redundant information are directly provided, and the accuracy and usability of PVT (PVT) calculation are directly improved.
In this example, the multi-system multi-frequency GNSS receiver simultaneously tracks the pseudorange, doppler and carrier observed quantity information of the GPS dual-frequency L 1、L2 and BDS tri-frequency B 1、B2、B3.
The technical scheme of PVT calculation of the multi-system multi-frequency GNSS receiver is also applicable to frequency point signals with double frequencies, three frequencies or more, and does not limit the GNSS receiver and the antenna. The GNSS receiver antenna is not limited to receiving single or multi-frequency signals, including all satellite signals that may be used for navigational positioning. The receiver is also not limited to a multi-system joint GNSS receiver, including GPS, GLONASS, GALILEO, BDS, QZSS and any navigation positioning satellite system that can forward satellite signals.
FIG. 2 is a flowchart illustrating a method for improving PVT performance of a multi-system multi-frequency GNSS receiver according to an embodiment of the present application. As shown in fig. 2, includes:
Obtaining an observation value of a current epoch multi-system multi-frequency GNSS user;
The first detection unit detects the tracking state of the observed quantity of the frequency points L 1、L2 of the GPS, and if the two frequency points L 1、L2 of the plurality of satellites of the GPS are detected to be well tracked, the detection is passed;
If the first detection unit passes:
The first IFB calculation unit calculates IFB L2 of each GPS satellite and carries out validity detection on all satellites with better GPS double-frequency tracking by taking L 1 as a reference frequency point, and the optimal IFB L2 value among the current epoch GPS frequencies is calculated by utilizing a plurality of satellites with valid detection;
The second IFB calculating unit estimates the optimal IFB L2 value calculated by the first IFB calculating unit and the previous period of time Performing validity detection, and filtering and updating by using the detected current optimal value IFB L2 The values are stored, and the control is carried out by adjusting the filter coefficient according to the single epoch detection state or the continuous multiple epoch detection deviation stateUpdated size;
further, the second IFB calculating unit needs to perform the operation for the first time Initializing the value, and startingThe value is initialized to the calculated and first pass detected effective IFB L2.
Similarly, the BDS takes B 1 as a reference frequency point, and calculates the frequency point of the BDS system B 2、B3 according to the steps
L 2 frequency point pseudo range observed quantity of ith satellite of GPS system by first fused pseudo range calculation unitProceeding withCorrecting, obtaining the pseudo-range observed quantity of the L 2 frequency point with the same clock difference reference as the L 1 frequency pointObserved quantity of ith satelliteFusion calculation is carried out to obtain the optimal value of the L 1 frequency pointLikewise, for the ith satellite of BDSPerforming fusion calculation to obtain an optimal value of the B 1 frequency point
The second detection unit performs condition detection on the available pseudo-range observed quantity acquired by the first fusion calculation unit, if the total number of detected effective satellites is less and the second ISB calculation unit is effectiveDetecting that the signal is not passed, otherwise, detecting that the signal is passed;
if the second detection unit detects that the signal passes:
the first positioning calculation unit performs joint positioning calculation on the optimal values of the fusion pseudo-ranges of the GPS and BDS systems of the first fusion calculation unit to obtain the user position and the receivers Zhong Chazhi of each system;
the first ISB calculation unit calculates the deviation ISB Bds_Gps between the two systems of the current epoch for the receiver Zhong Chazhi of the GPS and BDS systems acquired by the first positioning calculation unit;
the second ISB calculation unit estimates the current epoch ISB Bds_Gps calculated by the first ISB calculation unit and the previous period of time Validity detection is carried out, and the current epoch ISB Bds_Gps filter update passing detection is utilizedThe values are stored, and the control is carried out by adjusting the filter coefficient according to the single epoch detection state or the continuous multiple epoch detection deviation stateUpdated size;
If the second detection unit detects that the signal does not pass:
The second fusion pseudo-range calculation unit obtains the optimal value of the BDS ith satellite B 1 frequency point obtained by the first fusion calculation unit Proceeding withCorrecting, obtaining pseudo-range observed quantity with same clock error reference as GPS system L 1 frequency point
The second positioning resolving unit is used for observing the pseudo-range with the same clock error reference acquired by the second fusion computing unitPerforming positioning calculation to obtain the user position and the receiver clock error;
If the first detection unit does not pass, the first fusion calculation unit processes the two conditions, and then directly uses the first positioning calculation unit to perform positioning calculation;
In case one, if the frequency point of the GPS system L 2 Effective, the first fusion calculation unit is effective for the ith satelliteNormal fusion is carried out to obtain the optimal value of the L 1 frequency pointAt this time, if one of the observed quantity of the frequency points is detected poorly or lost, the weight w=0;
In the second case, if the frequency point of the GPS system L 2 Is ineffective ifIf present, the first fusion calculation unitIf it isIf the satellite is not present, the first fusion calculation unit eliminates the satellite;
similarly, fusion calculation is carried out on the ith satellite of the BDS according to the first condition or the second condition to obtain the optimal value of the B 1 frequency point
The first positioning calculation unit acquires the optimal values of the integrated pseudo ranges of the GPS and BDS systems of the first integrated pseudo range calculation unit, performs joint positioning calculation, and acquires the user position and the receiver Zhong Chazhi of each GNSS system;
The first fusion Doppler calculation unit is used for directly measuring Doppler observed quantity of the ith satellite of GPS Fusion calculation is carried out to obtain the Doppler optimal value of the ith satelliteSimilarly, for the j-th satellite of BDSFusion calculation of Doppler optimum value
The first speed measurement calculation unit acquires the GPS and BDS system fusion Doppler optimal value of the first fusion Doppler calculation unit to perform speed measurement calculation, and acquires the user speed and the receiver clock drift value.
FIG. 3 is a schematic diagram illustrating an apparatus for improving PVT performance of a multi-system multi-frequency GNSS receiver according to an embodiment of the present invention. As shown in FIG. 3, the method comprises a measurement information acquisition step, an inter-frequency deviation IFB calculation step, an IFB compensation multi-frequency pseudo-range fusion step, an IFB compensation pseudo-range joint positioning step, an inter-system deviation ISB calculation step, an ISB compensation multi-system pseudo-range fusion step, an ISB compensation pseudo-range positioning calculation step, a multi-frequency Doppler fusion step and a fusion Doppler velocity measurement calculation step.
A measurement information acquisition step, which is used for acquiring the observation value of the current epoch multi-system multi-frequency GNSS user;
an inter-frequency deviation IFB calculation step, which is used for calculating the inter-frequency deviation IFB between two frequency points of the same satellite in the GNSS system to obtain a stable inter-frequency deviation value between the two frequency points in a period of time
IFB compensation multi-frequency pseudo-range fusion step for performing multiple frequency points of ith satellite in GNSS systemAfter compensation, the pseudo-range observables of a plurality of frequency points are fused to obtain the optimal value of the satellite pseudo-range
IFB compensation pseudo-range joint positioning step for each satellite pseudo-range optimal value of different GNSS systemsPerforming joint calculation to obtain user coordinates and GNSS system receivers Zhong Chazhi;
Calculating the intersystem deviation ISB, namely calculating the intersystem clock difference ISB between two different GNSS systems in the same epoch to obtain a stable intersystem deviation value in a period of time
ISB compensation multisystem pseudo-range fusion step for ith satellite pseudo-range optimal value of different GNSS systemsProceeding withCompensation, obtaining pseudo-range observed quantity of same clock error reference of non-GPS satellite and GPS system
ISB compensation pseudo-range positioning calculation step for each satellite pseudo-range observed quantity with the same clock error reference as GPSAcquiring user coordinates and a user receiver Zhong Chazhi;
A multi-frequency Doppler fusion step, which is used for fusing Doppler observed quantities of a plurality of frequency points of each satellite in the GNSS system to obtain Doppler optimal values of each satellite
Fusion Doppler speed measurement calculation step for each satellite Doppler optimal value of each GNSS systemAnd carrying out joint calculation to obtain the user speed and the receiver clock drift value.
Compared with the prior art, in multi-system multi-frequency GNSS PVT calculation, according to the characteristic of short-term stability of inter-frequency deviation IFB in each GNSS system, the method maintains and calculates the inter-frequency deviation IFB and the inter-system deviation ISB when signal tracking is stable, and when signal tracking is unstable such as shielding, interference, serious multipath and the like, the method compensates the main frequency point by using the calculated and stable IFB for other effective frequency points of the satellite to the main frequency point when the main positioning frequency point is not locked or the main frequency point measurement value is rough. If the satellite simultaneously tracks a plurality of frequency points, the plurality of frequency point observation values after effective compensation of the check are further fused to participate in positioning calculation, the fused observation values can further weaken measurement errors and identify rough differences, and the number of available satellites and redundant observation information can be greatly increased. And, when the effective satellite number is further reduced, the acquired different systems are passed throughThe parameters reduce the dimension of the joint location solution.
According to the application, the observation value information of multi-system and multi-frequency signals is fully utilized, the number and quality of available observation values can be greatly improved in a complex scene, the compensated pseudo range is further used for RAIM detection, no additional state quantity is required to be added, the precision and usability of PVT calculation of a GNSS receiver are effectively improved, and PVT calculation continuity under severe environmental conditions such as urban canyons is particularly improved.
An embodiment of the application provides a storage medium having a computer program stored therein, wherein the computer program is arranged to perform the method as described in any of the preceding claims when run.
An embodiment of the application provides an electronic device comprising a memory having stored therein a computer program and a processor arranged to run the computer program to perform the method as described in any of the preceding claims.
Those of ordinary skill in the art will appreciate that all or some of the steps, systems, functional modules/units in the apparatus, and methods disclosed above may be implemented as software, firmware, hardware, and suitable combinations thereof. In a hardware implementation, the division between functional modules/units mentioned in the above description does not necessarily correspond to the division of physical components, for example, one physical component may have a plurality of functions, or one function or step may be cooperatively performed by several physical components. Some or all of the components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on computer readable media, which may include computer storage media (or non-transitory media) and communication media (or transitory media). The term computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, as known to those skilled in the art. Computer storage media includes, but is 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 tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer. Furthermore, as is well known to those of ordinary skill in the art, communication media typically embodies 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 includes any information delivery media.
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