A BDS-2 / 3 precise point positioning tight combination ambiguity resolution method

Abstract

The application discloses a BDS-2 / 3 precise point positioning tight combination ambiguity resolution method, which comprises the following steps: S1: fixing station coordinates, using international GNSS service (IGS) analysis center satellite orbit and clock error products, performing (MW) combination calculation and ionosphere-free (IF) floating point PPP resolution, and outputting station channel floating point wide lane ambiguity and pseudo-range OMC residual error; and S2: selecting a reference station and a BDS-3 reference star, and using the result of step S1 to calculate wide lane phase correction deviation and ionosphere-free combination signal distortion deviation correction number. The BDS-2 / 3 precise point positioning tight combination ambiguity resolution method has better model strength. Compared with a PPP-AR loose combination mode, the application adopts a tight combination mode, has better model strength, can fully play the advantages of BDS-2 and BDS-3 fusion processing, can eliminate the phase deviation between wide lane systems and the pseudo-range system deviation and the signal distortion deviation between channels of BDS-2 and BDS-3, and significantly improves the precise positioning performance of the Beidou system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of satellite navigation technology, in particular to a BDS-2 / 3 precise point positioning tight combination ambiguity resolution method. BACKGROUND

[0002] Fast initialization has always been a difficult problem for precise point positioning ambiguity resolution. High-precision troposphere and ionosphere products are usually introduced or multi-frequency multi-system GNSS processing schemes are used to speed up convergence. High-precision troposphere and ionosphere products depend on a dense reference station network and cannot be easily obtained. Therefore, multi-frequency multi-system processing is considered an effective solution.

[0003] BDS-3 has officially served on July 31, 2020, and will coexist with BDS-2 for a period of time in the future. The joint resolution technology of BDS-2 and BDS-3 not only helps to improve the performance of Beidou precise positioning, supports the promotion and application of Beidou system, but also can expand the application prospect of multi-system combination PPP technology.

[0004] At present, BDS-2 / 3 float PPP resolution mainly includes two types: one directly regards BDS-2 and BDS-3 as the same system; the second considers the pseudorange system bias between BDS-2 and BDS-3. Further, for PPP-AR resolution, the joint processing of BDS-2 and BDS-3 usually adopts a loose combination method, that is, BDS-2 and BDS-3 select their own reference stars respectively. For BDS-2 / 3 tight combination PPP-AR, there is no relevant research in the existing patents or documents. Compared with loose combination, tight combination only selects one reference star, which can often obtain better model strength, especially in the case of insufficient number of satellites. In addition, the existing technology does not fully consider the bias under the fusion processing of BDS-2 and BDS-3, such as wide-lane inter-system phase bias and pseudorange inter-system bias, and receiver-related inter-channel signal distortion bias.

[0005] In summary, the existing technology has obvious defects and deficiencies, so it is necessary and urgent to study a BDS-2 / BDS-3 precise point positioning tight combination ambiguity resolution method. SUMMARY

[0006] The present application relates to the field of satellite navigation technology, in particular to a BDS-2 / 3 precise point positioning tight combination ambiguity resolution method.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a BDS-2 / 3 precise point positioning tight combination ambiguity resolution method, comprising the following steps:

[0008] S1: fixed station coordinates, using the International GNSS Service (IGS) analysis center satellite orbit and clock error products, (MW) combined calculation and ionosphere-free (IF) floating point PPP solution, output station each channel floating wide lane ambiguity and pseudorange OMC residual;

[0009] S2: select reference station and BDS-3 reference star, use the results of step S1 to calculate wide lane phase correction bias and ionosphere-free combined signal distortion bias correction number;

[0010] S3: select clock error estimation network, use the ionosphere-free combined signal distortion bias correction number of step S2 and the satellite orbit product of IGS analysis center, re-estimate satellite clock error;

[0011] S4: use the ionosphere-free combined signal distortion bias of step S2 and the re-estimated satellite clock error of step 3 to calculate the pseudorange inter-system bias between each station BDS-2 and BDS-3;

[0012] S5: select phase bias estimation network, use the wide lane phase correction bias and ionosphere-free combined signal distortion bias correction number of step S2 and the pseudorange inter-system bias product of step S4, according to the tight combination model of BDS-2 / BDS-3, estimate and get wide lane and narrow lane (NL) phase bias;

[0013] S6: apply the above products and tight combination model to user end PPP-AR positioning solution.

[0014] Preferably, the wide lane phase correction bias and ionosphere-free combined signal distortion bias correction number of step S2 and the pseudorange inter-system bias correction number of step S4.

[0015] Preferably, when the step S5 performs server wide lane and narrow lane phase bias estimation and the step S6 user end positioning solution, the tight combination method is used to fuse and process BDS-2 and BDS-3 observation data.

[0016] Preferably, the floating point wide lane ambiguity and ionosphere-free combined pseudorange OMC residual sequence obtained by the step S1 can be expressed as:

[0017]

[0018]

[0019] Preferably, the selected reference station is the inter-station single difference:

[0020]

[0021] Preferably, the BDS-3 satellite is the inter-satellite single difference:

[0022]

[0023] Preferably, the step 2 uses IGG3 anti-difference estimation method to obtain the wide lane phase correction bias correction product between BDS-2 and BDS-3 and the ionosphere-free combined signal distortion bias correction product related to each channel of the receiver, and the anti-difference estimation parameters k0 and k1 are constants.

[0024] Compared with the prior art, the BDS-2 / 3 precise point positioning tight combination ambiguity resolution method has the beneficial effects that:

[0025] 1. Tight combination has better model strength. Compared with the PPP-AR loose combination mode, the present application adopts a tight combination mode, has better model strength, can fully play the advantages of BDS-2 and BDS-3 fusion processing, can eliminate the wide lane system phase bias and the pseudorange system bias and the channel signal distortion bias between BDS-2 and BDS-3, and significantly improve the performance of Beidou system precise positioning.

[0026] 2. Wide lane system phase bias and pseudorange system bias and channel signal distortion bias elimination. The present application selects reference stations and BDS-3 reference stars, not only successfully eliminates the wide lane system phase bias and the pseudorange system bias between BDS-2 and BDS-3, but also eliminates the channel signal distortion bias, which is beneficial to the joint solution under the BDS-2 / BDS-3 tight combination mode.

[0027] 3. Phase bias product performance improvement. The wide lane phase bias product of the present application has greatly improved the fixing rate and stability, and the ambiguity residual distribution is more concentrated, which greatly improves the product robustness.

[0028] 4. Beidou precise positioning performance improvement. The present application greatly accelerates the convergence speed of dynamic users, significantly improves the performance of Beidou precise positioning, and enhances the reliability and usability of Beidou system. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The flow chart of the BDS-2 / BDS-3 precise point positioning tight combination ambiguity resolution technology of the present application is shown in the figure.

[0030] Figure 2 The standard deviation STD of the Beidou wide lane phase bias product for 14 days from DOY 279 to 292 in 2021 is shown in the figure.

[0031] Figure 3 The ambiguity residual distribution of the Beidou wide lane phase bias product for 14 days from DOY 279 to 292 in 2021 is shown in the figure.

[0032] Figure 4To apply the loose combination and the dynamic user hour ambiguity resolution of the present application, the 14-day statistical results are as follows:

[0033] Figure 5 To apply the loose combination and the dynamic user hour ambiguity resolution of the present application, the 14-day statistical results of positioning accuracy are as follows. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0035] Please refer to Figures 1-4 The present application provides a technical solution: a BDS-2 / 3 precise point positioning tight combination ambiguity resolution method, comprising the following steps:

[0036] S1: fixing the station coordinates, using the satellite orbit and clock error products of the International GNSS Service (IGS) analysis center to perform Melbourne-Wübbena (MW) combination calculation and ionosphere-free (IF) float PPP resolution, and outputting the float wide-lane ambiguity and pseudorange OMC residual sequence of each channel of the station:

[0037]

[0038]

[0039] wherein, and are the original GNSS pseudorange and carrier observations; the index K represents different GNSS systems, for example, ‘C2’ represents BDS-2, and ‘C3’ represents BDS-3; represents the carrier signal frequency, represents the corresponding wavelength; and represent the receiver-end and satellite-end pseudorange hardware delays; and represent the float and integer wide-lane ambiguities, respectively, and and are the receiver-end and satellite-end wide-lane ambiguity decimal parts; is the ionosphere-free combination pseudorange observation minus its calculated value; represents the ionosphere-free combination pseudorange observation; represents the geometric distance after the antenna phase center and the earth rotation are corrected; and t' K,sdenotes the clock difference of receiver and satellite respectively; c is the light speed in vacuum; is the tropospheric delay; and denotes the MW and ionosphere-free signal distortion bias related to the receiver type respectively; denotes the ionosphere-free combined pseudorange observation noise

[0040] S2: Select the reference station and the BDS-3 reference star, calculate the wide lane phase correction bias and the ionosphere-free combined signal distortion correction number using the results of step S1, the wide lane phase correction bias and the ionosphere-free combined signal distortion correction number and the pseudorange inter-system bias correction number of step S4, and obtain the wide lane phase correction bias correction number between BDS-2 and BDS-3 and the ionosphere-free combined signal distortion bias correction number product related to each channel of the receiver using the IGG3 robust estimation method;

[0041] The inter-station single difference of the reference station is selected as follows:

[0042]

[0043] Wherein, Δ denotes the inter-station single difference. Then, a BDS-3 satellite is selected as the reference star to make the inter-satellite single difference as follows:

[0044]

[0045] Wherein, is the inter-satellite single difference. The formula uses the rounding method to obtain the decimal part of the Beidou wide lane ambiguity:

[0046]

[0047] Similarly, the inter-station single difference of the reference station is selected as follows:

[0048]

[0049] Then, the inter-satellite single difference of the selected BDS-3 satellite is made as follows:

[0050]

[0051] The position of the station coordinate point has been fixed as the IGS weekly solution, and the satellite position can be calculated from the IGS analysis center precise satellite orbit product. The ionosphere-free combined signal distortion bias sequence can be obtained through the formula. The BDS-2 / 3 wide lane phase correction bias and the ionosphere-free combined signal distortion bias are calculated for multiple days using the IGG3 robust method, and the final BDS-2 / 3 tight combined wide lane phase correction bias and the ionosphere-free signal distortion bias correction number product is obtained;

[0052] IGG3 anti-difference estimation is to replace the observation weight in adjustment model with equivalent weight, so as to avoid the influence of gross error on the estimation result as far as possible, and the iteration process is as follows:

[0053] First, the adjustment result is taken as the initial value of IGG3 anti-difference iteration, and the equivalent weight factor matrix is initialized;

[0054] According to the error equation and the equivalent weight factor, the equation is constructed and solved;

[0055] Calculate the residual error, and judge whether it is less than the convergence threshold, if yes, stop iteration and output the result; if not, proceed to the subsequent steps;

[0056] The equivalent weight factor matrix is calculated by IGG3 function, and jump to step b).

[0057] Equivalent weight factor Can be calculated by IGG3 function:

[0058]

[0059]

[0060] Wherein, is the standardized residual error, which can be calculated by the observation value residual error v i and the mean error mvi of the observation value residual error; k0 and k1 are constants, which are 1 and 2.5 respectively in the present application.

[0061] S3: Select the clock error estimation network, and use the ionosphere-free combined signal distortion bias correction number of step S2 and the satellite orbit product of IGS analysis center to re-estimate the satellite clock error;

[0062] S4: Calculate the pseudo-range system bias between BDS-2 and BDS-3 of each station by using the ionosphere-free combined signal distortion bias of step S2 and the re-estimated satellite clock error of step 3;

[0063] S5: Select the phase bias estimation network, use the wide lane phase correction bias and ionosphere-free combined signal distortion bias correction number of step S2 and the pseudo-range system bias product of step S4, and estimate and obtain the wide lane and narrow lane (NL) phase bias according to the BDS-2 / BDS-3 tight combination model;

[0064] S6: Apply the above products and the tight combination model to the user end PPP-AR positioning solution, and use the tight combination method to fuse and process the BDS-2 and BDS-3 observation data when the wide lane and narrow lane phase bias estimation of step S5 and the user end positioning solution of step S6 are performed.

[0065] The following tight combination method is used to fuse and process the BDS-2 and BDS-3 observation data when the server estimates the BDS-2 / 3 satellite wide-lane and narrow-lane phase bias and the user terminal performs ambiguity fixing and positioning solution:

[0066]

[0067] wherein, is the inter-system bias of the BDS-2 and BDS-3 pseudo-range after the ionosphere-free combined signal distortion bias is corrected; is the ionosphere-free combined phase observation value; is the ionosphere-free combined float ambiguity, is the corresponding wavelength; is the ionosphere-free combined phase observation value noise.

[0068] The user can realize the BDS-2 / 3 precise point positioning tight ambiguity solution by receiving the above wide-lane phase correction bias, ionosphere-free combined signal distortion bias, pseudo-range inter-system bias correction number and re-estimated satellite clock bias and satellite wide-lane and narrow-lane phase bias products.

[0069] Embodiment 2: Reference Figure 2 , 3 The statistical results of the 14-day standard deviation and the ambiguity residual distribution of the satellite wide-lane phase bias product of the application are shown. It can be seen that the satellite wide-lane phase bias of BDS-2 and BDS-3 both show high stability, and the average STD of BDS-2 and BDS-3 can reach 0.009 and 0.008 cycles respectively. At the same time, the application can greatly improve the distribution of wide-lane ambiguity residual, and the ambiguity residual of the application is much smaller than that of the loose combination method. Figure 3 It can be seen that the ambiguity residual is basically concentrated within 0.2 cycles, and the proportion within 0.1 cycles is as high as 92%. The above results show that the wide-lane phase bias product of the application has better stability and robustness.

[0070] Embodiment 3: Reference Figure 2 , 3 Six stations in Europe are selected as user stations to compare the loose combination and the tight combination ambiguity solution method of the application, Figure 4 and Figure 5 are the convergence speed and positioning error in the E\N\U three directions of the user in dynamic mode, it is not difficult to see that the application can accelerate the convergence speed of the E\N\U three directions, especially for the E direction, in addition, the application also greatly improves the positioning accuracy of the dynamic user PPP-AR.

[0071] In summary, the BDS-2 / 3 precise point positioning tight combination ambiguity resolution method can effectively eliminate the phase deviation between the wide lane systems of BDS-2 and BDS-3, the pseudo-range system deviation, and the inter-channel signal distortion deviation related to the receiver, fully utilizes the BDS-2 and BDS-3 observation data, significantly improves the convergence speed and positioning accuracy of PPP-AR, enhances the usability of the Beidou system, and has a positive effect on the promotion and application of the Beidou system.

[0072] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and concepts of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A BDS-2 / 3 precise point positioning tight combination ambiguity resolution method, characterized in that, The method comprises the following steps: S1: fixing station coordinates, using the International GNSS Service (IGS) analysis center satellite orbit and clock error products, performing Melbourne-Wübbena (MW) combination calculation and ionosphere-free (IF) floating point PPP solution, and outputting floating point wide lane ambiguity and pseudo-range OMC residual of each channel of the station; S2: selecting reference stations and BDS-3 reference stars, and calculating wide lane phase correction bias and ionosphere-free combination signal distortion bias correction numbers by using the results of step S1; S3: selecting clock error estimation network, and re-estimating satellite clock error by using the ionosphere-free combination signal distortion bias correction numbers of step S2 and the IGS analysis center satellite orbit products; S4: calculating the pseudo-range inter-system bias between BDS-2 and BDS-3 of each station by using the ionosphere-free combination signal distortion bias of step S2 and the re-estimated satellite clock error of step 3; S5: selecting phase bias estimation network, and estimating and obtaining wide lane and narrow lane (NL) phase bias according to the BDS-2 / BDS-3 tight combination model by using the wide lane phase correction bias and the ionosphere-free combination signal distortion bias correction numbers of step S2 and the pseudo-range inter-system bias product of step S4; S6: applying the above products and the tight combination model to user end PPP-AR positioning solution. 2.The BDS-2 / 3 precise point positioning tight combination ambiguity resolution method according to claim 1, characterized in that: The wide lane phase correction bias and the ionosphere-free combination signal distortion bias correction numbers of step S2 and the pseudo-range inter-system bias correction numbers of step S4. 3.The BDS-2 / 3 precise point positioning tight combination ambiguity resolution method according to claim 1, characterized in that: When the server wide lane and narrow lane phase bias estimation of step S5 and the user end positioning solution of step S6 are performed, the BDS-2 and BDS-3 observation data are fused and processed in a tight combination mode.

4. The BDS-2 / 3 precise point positioning tight combination ambiguity resolution method according to claim 1, characterized in that: The floating point wide lane ambiguity and ionosphere-free combination pseudo-range OMC residual sequence obtained in step S1 can be expressed as:

5. The BDS-2 / 3 precise point positioning tight combination ambiguity resolution method according to claim 1, characterized in that: The inter-station single difference of the reference stations selected in step S2 is:

6. The BDS-2 / 3 precise point positioning tight combination ambiguity resolution method according to claim 1, characterized in that: The inter-satellite single difference of the BDS-3 satellites is:

7. The BDS-2 / 3 precise point positioning tight combination ambiguity resolution method according to claim 1, characterized in that: The wide lane phase correction bias correction numbers between BDS-2 and BDS-3 and the ionosphere-free combination signal distortion bias correction numbers related to the receiver obtained in step 2 by using the IGG3 robust estimation method, and the robust estimation parameters k0 and k1 are constants.

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