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Objectives: Although the precise point positioning (PPP) can provide global cm-level positioning, it takes tens of minutes to converge. While PPP-RTK (real-time kinematic) relies on regional reference stations to provide atmospheric delay corrections to accelerate the convergency, however, only the regional service can be provided. Methods: PPP with multi-frequency and multi-GNSS observations is presented, and only the satellite orbit, clock and observable-specific signal bias (OSB) are needed to achieve instantaneous cm-level positioning. This approach solves the problems of slow convergence of PPP as well as the limited-service scope of PPP-RTK. Furthermore, a wide-area instantaneous cm-level service system com ‐ patible with BDS （BeiDou satellite navigation system） PPP-B2b service is proposed, and the performance of real-time orbit, clock and OSB is evaluated. Results: The results of static and in-vehicle kinematic data in China confirm that the system can provide cm-level precision positioning within 1 min. Conclu⁃ sions: It's implied that our system bears the ability to meet the needs of fast, high-precision and high-confidence positioning in autonomous driving and other fields around the world. [ABSTRACT FROM AUTHOR]

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Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objectives: Precise point positioning (PPP) combines the advantages of standard point positioning (SPP) and relative positioning, which can achieve centimeter level positioning. With the development of BeiDou satellite navigation system (BDS), more and more BDS satellites begin to provide global positioning, navigation and timing services, which also promotes the development of multi⁃frequency and multi⁃system PPP. For a long time, because of the atmospheric delay and hardware delay of satellite and receiver, the ambiguity of PPP is not an integer. PPP needs a long time to converge, which greatly limits its application. The ambiguity can be restored to integer and the convergence time can be shortened with the help of fractional cycle bias (FCB). Methods: In order to improve the effect of precise point positioning⁃am biguity resolution (PPP⁃AR) of BDS as a whole, we estimate the FCBs of GPS and BDS based on the observation data from August 1 to August 31 in 2020 of globally distributed stations. The single difference between satellites is used to eliminate the influence of hardware delay at the receivers, and the single difference ambiguity vector is solved by the whole network adjustment to obtain the FCB estimation of each satellite. Results: The results of the time series of BDS⁃3 wide lane (WL) and narrow lane (NL) FCBs show that the WL FCBs has long term stability, the change of BDS 3 WL FCBs in 31 days is less than 0.2 weeks, and the change of GPS WL FCBs is less than 0.1 weeks. The FCBs of BDS⁃3 NL can keep stable for a period of time, and the change is less than 0.1 weeks. The percentages of GPS WL and NL FCBs residuals within 0.15 weeks are 99.8% and 99.3% respectively, and the percentages of BDS 3 are 99.7% and 98.1% respectively. In order to reflect the improvement effect of FCBs on PPP, static and dynamic PPP⁃AR tests were carried out at 8 stations around the world. The results show that under the static condition, the average fixed time and convergence time of BDS⁃3 are 31.5 min and 24.9 min respectively, which is 24.8% shorter than the float PPP. The errors in E, N and U directions are 1.03 cm, 0.60 cm and 1.72 cm respectively, and the fixed rate is 89.8%. Under the dynamic condition, the average fixed time and convergence time of BDS⁃3 are 33.3 min and 50.7 min respectively, which is 17.4% shorter than the float PPP. The errors in E, N and U directions are 2.57 cm, 2.29 cm and 3.71 cm respectively, and the fixed rate is 83.9%. Conclusions: PPP⁃AR can shorten the convergence time of PPP to a certain extent, but the improvement of positioning accuracy is not obvious after complete convergence. BDS 3 FCBs stability is limited by precision products and observation data, and its PPP⁃AR is slightly worse than GPS. [ABSTRACT FROM AUTHOR]

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The performance of NTCM-BC model, MNTCM-BC model, NTCM-Klobuchar model and traditional Klobuchar model are compared and analyzed. The results show that: In a solar cycle, the accuracy of the vertical total electron content calculated by the NTCMBC model and MNTCMBC model is consistent and the highest, followed by the NTCM-Klobuchar model and the Klobuchar model is the lowest. At low- latitude stations, the NTCM models can reduce the error about 20 TECU compared with the Klobuchar model at most. In comparison to use the Klobuchar model, the single point positioning using NTCMBC and MNTCMBC model can improve the height accuracy of about 38%, especially at lowlatitude stations, the maximum can be reduced by about 3 m. [ABSTRACT FROM AUTHOR]

Multi-GNSS (Global Navigation Satellite System) precise orbit determination and prediction is the prerequisite of high-precision real-time precise positioning. To improve the efficiency of ultra-rapid orbit solution and prediction precision in multi-GNSS, this paper proposes a collocation method based on block recursive least squares. The proposed method can combine post estimation with real-time filtering orbit determination by ① relaxing and connecting kinetics and geometry parameters, and ② transferring and recurring orbit status parameters. In addition, this method increases the efficiency of GNSS orbit solution and shortens the orbit updating time. Furthermore, experimental result verifies the reliability and effectiveness of our proposed method. Our orbit precisions are superior to the precisions of ultra-rapid GPS orbits provided by international GNSS service (IGS) and German Research Centre for Geosciences. The results show that, for quad-constellation (GPS/GLONASS/Galileo/BDS) precise orbit determination by 120 ground observation stations, our method is able to realize one-hour updating and provides service with 30 minutes delay. The 3D root mean squares of available parts in GPS/GLONASS/Galileo/BDS real-time orbit are 2.8 cm,8.5 cm,5.0 cm and 11.5 cm(IGSO/MEO), respectively. At present, one-hour updating for multi-GNSS orbits and real-time service system have been provided, and compared with previous three-hour and six-hour updating orbit, the precision has been improved by 20% to 40%. [ABSTRACT FROM AUTHOR]

Computation-intensive tasks in the data processing for global ionosphere mapping are analyzed. A parallel algorithm with OpenMP technique is proposed for data preprocessing incorporating normal equation matrix stacking, parameter pre-elimination, and normal equation matrix inversion. A validation experiment was executed on a single server. Results indicate that the computing time for rapid global ionosphere mapping is only about 10~13 minutes with a speedup of about six, the time for final global ionosphere mapping is only about 39-47 minutes and the speedup is about five. The precision for global ionosphere products are about 2.8~3.8 TECUs compared with IGS final products, and the final solutions are at higher precision, about 0.2 TECUs in contrast to rapid solutions. The parallel algorithm proposed in this paper is very useful for the optimal testing of global ionosphere mapping, when reprocessing long time span data extending over periods such as 10 years, as well as for the real-time ionosphere mapping. [ABSTRACT FROM AUTHOR]

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Differential Code Biases (DCBs) are the main systematic error in ionosphere TEC monitoring and modeling. Meanwhile, satellite DCBs are important parameters for satellite navigation messaging. This article presents a satellite DCBs estimation algorithm and DCBs transformation formula derived under different zero-mean conditions as applied to the constellation average of the satellite DCBs. Using BeiDou Experimental Tracking Station (BETS) observations from 2013, the DCBs for BDS satellite were determined, and the BDS satellite DCBs monthly stability was analyzed and compared with the DCBs products published by MCEX under the same zero-mean conditions. Results show that the BDS satellite B1-B2 DCBs values are between -9~17 ns, and the stability was better than 0. 4 ns. Stability for BDS IGSO satellites was belter than GEO and MEO satellites. The BDS satellite DCBs determined using BETS and MGEX have system biases, where the largest discrepancy was about 1. 7 ns. The probable reason lies in a discrepancy in the pseudo range code measurement. The difference of receiver material results in a discrepancy in receiver DCBs. [ABSTRACT FROM AUTHOR]

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We studied and implemented an algorithm for real-time precise satellite clock estimation based on the undifferenced code and phase observations. The BDS and GPS observations of 53 MGEX global sites were collected to generate the real-time clock that was compared with the final WHU 30 s precise clock product. The accuracy of our real-time GPS clock was better than 0.06 ns, comparable to that of the IGS final clock products, which verifies the processing accuracy of our software. The accuracy of the real-time BDS clock was 0.1-0.15 ns, a little worse than that of GPS satellites. A kinematic PPP test showed that, the horizontal accuracy of BDS solution was about 0.041 m, comparable to 0.058 m of GPS solution, while the vertical accuracy is 0.069 m, a slightly worse than 0.037 m of GPS. The kinematic PPP solution based on the real-time clock correction was consistent with the solution based on the final clock products, which verifies the real-time clock products. [ABSTRACT FROM AUTHOR]