Receiver DCB unification method based on regional reference station network

Abstract

The invention discloses a DCB unification method based on a local area network reference station network receiver. The method comprises the following steps: obtaining ionospheric correction of each reference station of a regional reference station network through a non-difference non-combination PPP AR positioning mode; the ionosphere corrects the DCB containing the reference stations, due to the fact that satellites observed by the reference stations of the regional network are different, the benchmark of the DCB of the receiver of the regional reference network is not uniform, and the relation of the DCB of the receiver between the regional reference stations is obtained through the inter-station single-difference method of the reference stations of the regional reference station network; and solving the DCB of each reference station through a constraint attached least square method and the constraint that all DCBs in the regional reference station network are equal to 0, thereby realizing the unification of the DCBs of the receivers of the regional reference station network.

Description

Technical Field

[0001] The present invention relates to the fields of GNSS positioning, autonomous driving, UAV navigation, geodetic surveying, geophysical research, etc., and specifically to a method for unifying the DCB of receivers in a regional network reference station network. Background Art

[0002] In traditional methods, in order to ensure that the receivers absorb the same ionospheric corrections of satellites, only the satellites with fixed ambiguities observed by the same reference station are used to calculate the ionospheric corrections, ignoring the satellites with fixed ambiguities observed by a small number of reference stations. The final result is that only some reference stations and satellites are used to construct the ionospheric model. In order to make full use of the satellites observed by the reference stations, it is necessary to unify the Differential Code Bias (DCB) of the receivers in the regional network reference station network. Summary of the Invention

[0003] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, a method for unifying the DCB of receivers in a regional network reference station network is proposed, which solves the problems caused by the influence of the receiver DCB coupled in the ionospheric correction and the low utilization rate of reference stations and satellites.

[0004] The technical solution of the present invention is: a method for unifying the DCB of receivers in a regional network reference station network, including:

[0005] Obtaining the ionospheric correction of each reference station in the regional reference station network through the positioning mode of non-differential non-combination PPP AR, and the ionospheric correction contains the DCB of the reference station;

[0006] Eliminating the DCB of the satellite and the ionosphere from the ionosphere containing the DCB correction through the inter-station single-difference method to obtain the relationship equation of the receiver DCB between the regional reference stations;

[0007] Calculating the receiver DCB of each reference station through the constrained least squares method and the constraint that all DCBs in the regional reference station network are equal to 0, so as to realize the unification of the receiver DCB in the regional reference station network.

[0008] Obtaining the ionospheric correction of each reference station in the regional reference station network through the positioning mode of non-differential non-combination PPP AR, including:

[0009] Assume that the pseudo-range and carrier of the GNSS raw observation data observed by the regional network reference station have the following observation equations:

[0010]

[0011] where represents the geometric distance from the satellite antenna phase center to the receiver; s represents the GNSS system; t r and t s respectively represent the clock offsets of the receiver and the satellite; represents the ionospheric delay at frequency i; and respectively represent the mapping functions of the zenith hydrostatic delay and the wet delay; T d,r and T w,r respectively represent the mapping functions of the tropospheric zenith hydrostatic delay and the wet delay; λ i represents the carrier wavelength at frequency i, represents the carrier phase integer cycle ambiguity, and respectively represent the delays of the receiver and satellite pseudorange hardware at frequency i; and respectively represent the delays of the receiver and satellite phase hardware at frequency i; and respectively represent the observation noises of the pseudorange and the carrier phase;

[0012] At the regional network reference station, the raw observations are processed by the undifferenced combined precise point positioning UDUC PPP model, and the ionospheric tilt delay is estimated as an unknown parameter;

[0013] Using the positioning mode of PPP AR to evaluate the parameter, the results of the ionospheric parameters of each reference station in the regional station are as follows:

[0014]

[0015] Among them, represents the ionospheric correction with DCB for each reference station in the regional station network; β ij represents the coefficient of the ionosphere-free combination; represents the DCB correction at the receiver end; represents the DCB correction at the satellite end.

[0016] The measurement equation of the UDUC PPP model is as follows:

[0017]

[0018] Among them,

[0019]

[0020] represents the unit vector from the receiver r to the satellite s; x represents the position of the receiver; γ ij represents the ionospheric coefficient of frequency i relative to frequency j; α ijand β ij represents the coefficient of the ionosphere-free combination; represents the satellite clock error of the absorption code bias.

[0021] The DCB correction at the receiver side and the DCB correction at the satellite side are specifically expressed as:

[0022]

[0023] By using the inter-station single-difference method for the ionosphere with DCB correction, the DCB of the satellite and the ionosphere are eliminated, and the relationship equation of the receiver DCB between the regional reference stations is obtained, including:

[0024] Since the satellites observed by each reference station in the regional network are different, the reference of the receiver DCB in the regional reference network is not unified; by using the inter-station single-difference method for the above-mentioned ionosphere with DCB correction, the DCB of the satellite and the ionosphere can be eliminated, and the relationship equation of the receiver DCB between the regional reference stations is obtained as follows:

[0025] The DCB of the satellite side and the ionosphere delay can be eliminated by the obtained inter-station single-difference of the ionosphere, and the expression is:

[0026]

[0027] Then the observation equation is expressed as:

[0028]

[0029] where, R represents a column vector with all coefficients being 1; The result of the above-mentioned inter-station single-difference of the ionosphere, with the subscript representing two stations p, q tracking the satellite; n represents the pair of inter-station single-differences of the regional reference stations; ε DCB represents the noise between the two stations; H represents the previous coefficient matrix;

[0030] Through the above equation, the relationship equation of the receiver X DCB between the regional reference stations is obtained.

[0031] By using the constrained least squares method and the constraint that all DCBs in the regional reference station network are equal to 0, the receiver DCB of each reference station is obtained to unify the receiver DCB of the regional reference station network, including:

[0032] The constrained least squares method considering the constraint is used to evaluate the DCB of each station in the reference station network, and the DCB evaluation equation of the receiver is expressed as:

[0033]

[0034] N = HT WH

[0035]

[0036] where H represents the given DCB coefficient matrix, K represents the Lagrange multiplier; C represents a matrix with all coefficients being 1, which is used to set the sum of DCBs of different reference stations to zero as a constraint; the noise of the single-difference observation can be determined by W through the deviation of the average value of the inter-station single-difference ionospheric delay;

[0037] Combining the above equations, the unified values of each receiver in the regional reference station network are obtained. value.

[0038] The beneficial effects of the present invention compared with the prior art:

[0039] The present invention effectively unifies the DCBs at the receiver ends of each reference station in the regional observation stations based on the least squares with constraints, solves the problem that satellites must be co-visible at all stations in the traditional modeling method, and greatly increases the number of available satellites; in the process of evaluating the receiver DCB, the present invention identifies and eliminates satellites with gross errors or weak spatial similarity of ionospheric delay, improving the accuracy of DCB; using the obtained DCB correction of the receivers in the regional reference station network can improve the accuracy of navigation positioning and timing; in the fields of autonomous driving, UAV navigation, geodetic surveying, geophysical research, etc., DCB correction is a key technology for achieving high-precision positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a flowchart of a method for unifying the DCB of receivers based on a regional reference station network according to the present invention.

[0041] Figure 2 is a schematic diagram of satellites with fixed ambiguities at different reference sites in the regional reference station network of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0042] As Figure 1 shown, the method of the present invention includes:

[0043] 1) Step 101: Obtain the ionospheric correction of each reference station in the regional reference station network through the positioning mode of undifferenced and non-combined PPP AR.

[0044] The observation equations of the GNSS raw observation data pseudorange and carrier are:

[0045]

[0046] where represents the geometric distance from the satellite antenna phase center to the receiver; sys represents the GNSS system; tr and t s represent the clock offsets of the receiver and satellite, respectively; is the ionospheric delay at frequency i; and represent the mapping functions of the zenith hydrostatic delay and wet delay, respectively, while T d,r and T w,r represent the mapping functions of the tropospheric zenith hydrostatic delay and wet delay, respectively; λ i is the carrier wavelength at frequency i, is the carrier phase integer cycle ambiguity, and are the delays of the receiver and satellite pseudorange hardware at frequency i, respectively, while and are the delays of the receiver and satellite phase hardware at frequency i, respectively, and are the observation noises of the pseudorange and carrier phase, respectively. It should be noted that, for simplicity, other errors usually corrected by the corresponding models, such as phase wrapping, phase center offsets (PCOs), phase center variations (PCVs), and tidal loading, are omitted in (1) and (2).

[0047] The ionosphere-free (IF) model and the undifferenced and uncombined (UDUC) model are both commonly used models in PPP solutions. Although the IF model can effectively eliminate the first-order effect of the ionosphere, there are still some limitations, such as amplified observation noise and the inability to directly invert the ionospheric delay. In contrast, the UDUC PPP model processes the raw observations and estimates the ionospheric tilt delay as an unknown parameter, which can provide prior knowledge of the ionosphere in addition to the accurate ionospheric delay. The measurement equation of the dual-frequency UDUC PPP model is shown as follows:

[0048]

[0049] where

[0050]

[0051] It can be noted that the precise clock offset of the IGS agency absorbs the satellite code bias of the ionosphere-free combination. If this clock offset product is used in PPP positioning, the ionospheric parameter will absorb this pseudorange hardware delay. To more accurately evaluate the ionospheric parameter of the reference station, the PPP AR positioning mode is used to evaluate this parameter. The representation of the ionospheric parameter in the result:

[0052]

[0053] represents the unit vector from receiver r to satellite s; x represents the position of the receiver; γij Denotes the ionospheric coefficient of the i frequency relative to the j frequency; α ij and β ij Denotes the coefficient of the ionosphere-free combination; Denotes the satellite clock error that absorbs the code bias.

[0054] Through the above operations, the results of the ionospheric parameters of each reference station of the regional station

[0055] 2) Step 102: This ionospheric correction contains the DCB of the reference station. Since the satellites observed by each reference station in the regional network are different, the benchmarks of the receiver DCB in the regional reference network are not unified. By using the inter-station single-difference method of the reference stations in the regional reference station network, the relationship equation of the receiver DCB between the regional reference stations is obtained;

[0056] The influence of the satellite-side DCB is independent of the reference station and remains unchanged at different reference stations, and has no influence on the positioning result. However, the DCB of the receiver can be eliminated by the inter-satellite single-difference method assuming that the ionospheric corrections absorbed by the receiver DCB for each satellite are the same.

[0057] As Figure 2 shown, in the traditional method, in order to ensure that the ionospheric corrections absorbed by the receiver are the same, only the satellites with fixed ambiguities observed by the same reference station are used to calculate the ionospheric corrections, ignoring the satellites with fixed ambiguities observed by a small number of reference stations. The final result is that only some reference stations and satellites are used to construct the ionospheric modeling. In order to make full use of the satellites observed by the reference stations, it is necessary to unify the receiver DCB of the regional reference station network.

[0058] According to the existing literature, for the same satellite, it is almost the same for reference stations hundreds of kilometers apart in the region where the ionosphere is inactive. Therefore, the satellite-side DCB and ionospheric delay can be eliminated by the inter-station single-difference. The following are the expressions:

[0059]

[0060] where

[0061]

[0062] The observation equation can be expressed as:

[0063]

[0064] where R represents a column vector with all coefficients being 1; The result of the above ionospheric inter-station single-difference, the subscript represents two stations p, q that track the satellite; n represents the pair of inter-station single-differences of the regional reference stations; ε DCBDenote the noise between two stations; H represents the previous coefficient matrix.

[0065] Through the above equations, the relational equation of the receiver X between regional reference stations can be obtained. DCB of the relationship.

[0066] 3) Step 103: By using the constrained least squares method and the constraint that all DCBs in the regional reference station network are equal to

[0067] 0, calculate the DCB of each reference station, so as to unify the DCB of the receivers in the regional reference station network;

[0068] Use the least squares considering constraints to evaluate the DCB of each station in the reference station network. The DCB evaluation equation of the receiver can be expressed as:

[0069]

[0070] N = H T WH

[0071]

[0072] where H represents the given DCB coefficient matrix, K represents the Lagrange multiplier; C represents a matrix with all coefficients being 1, which is used as the constraint that the sum of the DCBs of different reference stations is set to zero; the noise of the single-difference observation can be determined by W through the deviation of the average value of the inter-station single-difference ionospheric delay.

[0073] Combining the above equations, the unified values of each receiver in the regional reference station network can be obtained. value.

Claims

1. A method for unifying the DCB of receivers in a regional network reference station network, characterized in that Including: Obtain the ionospheric corrections of each reference station in the regional reference station network through the positioning mode of non-differential and non-combination PPP AR. The ionospheric corrections contain the DCB of the reference stations; Eliminate the DCB of the satellite and the ionosphere by means of the inter-station single-difference method for the ionosphere containing the DCB correction, and obtain the relational equation of the receiver DCB between the regional reference stations; Obtain the receiver DCB of each reference station through the constrained least squares method and the constraint that all DCBs in the regional reference station network are equal to 0, and realize the unification of the receiver DCB of the regional reference station network.

2. The method for unifying the DCB of receivers of a regional network reference station network according to claim 1, characterized in that: Obtain the ionospheric corrections of each reference station in the regional reference station network through the positioning mode of non-differential and non-combination PPP AR, including: Let the regional network reference station observe the pseudorange of the GNSS raw observation data and the carrier wave The observation equation is as follows: where represents the geometric distance from the satellite antenna phase center to the receiver; s represents the GNSS system; t r and t s represent the clock offsets of the receiver and the satellite, respectively; represents the ionospheric delay at frequency i; and represent the mapping functions of the zenith hydrostatic delay and the wet delay, respectively; T d,r and T w,r represent the mapping functions of the tropospheric zenith hydrostatic delay and the wet delay, respectively; λ i represents the carrier wavelength at frequency i, represents the integer cycle ambiguity of the carrier phase, and d i s represent the delays of the receiver and satellite pseudorange hardware at frequency i, respectively; and represent the delays of the receiver and satellite phase hardware at frequency i, respectively; and represent the observation noises of the pseudorange and the carrier phase, respectively; Process the original observations through the non-differential combined precise point positioning UDUC PPP model at the regional network reference stations, and estimate the ionospheric tilt delay as an unknown parameter; Adopt the positioning mode of PPP AR to evaluate the modified parameters, and the results of the ionospheric parameters of each reference station in the regional stations are: Among them, represents the ionospheric correction with DCB for each reference station in the regional network; β ij represents the coefficient of the ionosphere-free combination; represents the DCB correction at the receiver end; represents the DCB correction at the satellite end.

3. A method for unifying the DCB of receivers of a regional network reference station network according to claim 2, characterized in that: The measurement equation of the UDUC PPP model is as follows: Among them, Denote the unit vector from receiver r to satellite s; x represents the position of the receiver; γ ij Denote the ionospheric coefficient of frequency i relative to frequency j; αi j and βi j Denote the coefficients of the ionosphere-free combination; Denote the satellite clock error that absorbs the code bias.

4. A method for unifying the DCB of receivers based on a regional network reference station network according to claim 3, characterized in that: The DCB correction at the receiver side and the DCB correction at the satellite side are specifically expressed as:

5. A method for unifying the DCB of receivers based on a regional network reference station network according to claim 4, characterized in that: Eliminate the DCB of the satellite and the ionosphere by means of the inter-station single-difference method for the ionosphere containing the DCB correction, and obtain the relational equation of the receiver DCB between the regional reference stations, including: Since the satellites observed by each reference station in the regional network are different, the benchmark of the receiver DCB in the regional reference network is not unified; by using the inter-station single-difference method for the above-mentioned ionosphere containing the DCB correction, the DCB of the satellite and the ionosphere can be eliminated, and the relational equation of the receiver DCB between the regional reference stations can be obtained, specifically as follows: The DCB and ionospheric delay at the satellite end can be eliminated by the obtained ionospheric inter-station single-difference, and the expression is: Then the observation equation is expressed as: wherein, R represents a column vector with all coefficients being 1; For the above results of the ionospheric single-difference between stations, the subscripts represent two stations p and q that track the satellite; n represents the pair of single-differences between regional reference stations; ε DCB represents the noise between the two stations; H represents the coefficient matrix in front; Based on the above equation, the relational equation of the receivers between the regional reference stations X is obtained. DCB ​ 6. A method for unifying the DCB of receivers in a regional network reference station network according to claim 1, characterized in that: Obtain the receiver DCB of each reference station through the constrained least squares method and the constraint that all DCBs in the regional reference station network are equal to 0, and realize the unification of the receiver DCB of the regional reference station network, including: Evaluate the DCB of each station in the reference station network by using the least squares method considering constraints. The evaluation equation of the receiver DCB is expressed as: N=H T WH Where H represents the given DCB coefficient matrix, K represents the Lagrange multiplier; C represents a matrix with all coefficients being 1, which is used as a constraint to set the sum of the DCBs of different reference stations to zero; the noise of the single-difference observation can be determined by W through the deviation of the average value of the inter-station single-difference ionospheric delay. Combined with the above equations, the values of each receiver for the unified regional reference station network are obtained. Value.

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