GPS Solutions

, 23:20 | Cite as

Enhancing real-time precise point positioning time and frequency transfer with receiver clock modeling

  • Yulong GeEmail author
  • Feng ZhouEmail author
  • Tianjun Liu
  • WeiJin Qin
  • Shengli Wang
  • Xuhai Yang
Original Article


Thanks to the international GNSS service (IGS), which has provided an open-access real-time service (RTS) since 2013, real-time precise point positioning (RT-PPP) has become a major topic in the time community. Currently, a few scholars have studied RT-PPP time transfer, and the correlation of the receiver clock offsets between adjacent epochs have not been considered. We present a receiver clock offset model that considers the correlation of the receiver clock offsets between adjacent epochs using an a priori value. The clock offset is estimated using a between-epoch constraint model rather than a white noise model. This approach is based on two steps. First, the a priori noise variance is based on the Allan variance of the receiver clock offset derived from GPS PPP solutions with IGS final products. Second, by applying the between-epoch constraint model, the RT-PPP time transfer is achieved. Our numerical analyses clarify how the approach performs for RT-PPP time and frequency transfer. Based on five commonly used RTS products and six IGS stations, two conclusions are obtained straightforwardly. First, all RT-PPP solutions with different real-time products are capable of time transfer. The standard deviation (STD) values of the clock difference between the PPP solutions with respect to the IGS final clock products are less than 0.3 ns. Second, the STD values are reduced significantly by applying our approach. The reduction percent of STD values ranges from 4.0 to 35.5%. Moreover, the largest improvement ratio of frequency stability is 12 as compared to the solution of the white noise model. Note that the receiver clock offset from IGS final clock products is regarded as a reference.


GPS Real-time precise point positioning (RT-PPP) Time and frequency transfer Receiver clock offset modeling 



This work was supported by the National Natural Science Foundation of China (No. 41104021, No. 11173026, No. 41704008 and No. 11703033). The authors gratefully acknowledge iGMAS for funding. We would like to thank the Program for Excellent Talents in University of Anhui Province of China (No. gxyq2017008), who supported the project. We also thank the IGS for providing precise orbit, clock products and data.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.National Time Service CenterChinese Academy of SciencesXi’anChina
  2. 2.University of Chinese Academy of SciencesBeijingChina
  3. 3.Key Laboratory of Precise Positioning and Timing TechnologyChinese Academy of SciencesXi’anChina
  4. 4.QianXun Spatial Intelligence Inc.ShanghaiChina
  5. 5.NASG Key Laboratory of Land Environment and Disaster MonitoringChina University of Mining and TechnologyXuzhouChina
  6. 6.Institute of Ocean EngineeringShandong University of Science and TechnologyQingdaoChina
  7. 7.School of Astronomy and Space ScienceUniversity of Chinese Academy of SciencesBeijingChina

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