Precise frequency transfer model suitable for short baseline link based on GPS single-differenced observations with ambiguity resolution


A frequency transfer model that is suitable for short baseline links is proposed herein. Based on a GPS single-differenced (SD) observation among two stations, the initial values and the corresponding variance of the SD ambiguity can be estimated. This can form the double-differenced (DD) ambiguity while defining the reference satellite, and can be fixed to an integer value by using the integer search method. After defining the values of the SD ambiguity datum for the reference satellite, the other SD ambiguities can be recovered; then, the final time difference of the two stations can be estimated using the known and fixed SD ambiguities. Validations performed using five different baseline links show that the new method has better accuracy and stability for precise time transfer than the traditional precise point positioning method, and it can be operated in conjunction with the broadcast ephemeris data, which is more convenient for real-time application.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6


  1. Allan, D.W., Weiss, M. (1980) Accurate time and frequency transfer during common-view of a GPS satellite. In Proceedings of the 1980 IEEE Frequency Control Symposium, Philadelphia, PA, USA, 28–30 May, pp. 334–356

  2. Caissy M, Agrotis L, Weber G, Hernandez-Pajares M, Hugentobler U (2012) Innovation: the international gnss real-time service. GPS World 23:52–58

    Google Scholar 

  3. Dach R, Hungentobler U, Fridez P, Michael M (2007) Bernese GPS software version 5.0. Astronomical institute, University of Bern

  4. Ge M, Gendt G, Rothacher M, Shi C, Liu J (2008) Resolution of GPS carrier-phase ambiguities in precise point positioning (PPP) with daily observations. J Geod 82(7):389–399.

    Article  Google Scholar 

  5. Geng J, Shi C (2017) Rapid initialization of real-time PPP by resolving undifferenced GPS and GLONASS ambiguities simultaneously. J Geod 91:361–374

    Article  Google Scholar 

  6. Harmegnies A, Defraigne P, Petit G (2013) Combining GPS and GLONASS in all-in-view for time transfer. Metrologia 50:277–287

    Article  Google Scholar 

  7. Jiang Z, Petit G (2009) Combination of TWSTFT and GNSS for accurate UTC time transfer. Metrologia 46:305–314

    Article  Google Scholar 

  8. Jiang Z, Lewandowski W (2012) Use of GLONASS for UTC time transfer. Metrologia 49:57–61

    Article  Google Scholar 

  9. Kouba J, Héroux P (2001) Precise point positioning using igs orbit and clock product. GPS Solut 5:12–28

    Article  Google Scholar 

  10. Li X, Ge M, Dai X, Ren X, Fritsche M, Wickert J, Schuh H (2015) Accuracy and reliability of multi-GNSS real-time precise positioning: GPS, GLONASS, BeiDou, and Galileo. J Geod 89:607–635

    Article  Google Scholar 

  11. Petit G, Jiang Z (2008) GPS All in view time transfer for TAI computation. Metrologia 45:35–45

    Article  Google Scholar 

  12. Schmid R (2003) Estimation of elevation-dependent satellite antenna phase center variations of GPS satellites. J Geod 77:440–446

    Article  Google Scholar 

  13. Teunissen PJG (1995) The least-square ambiguity decorrelation adjustment: a method for fast GPS ambiguity estimation. J Geodesy 70(1–2):65–82

    Article  Google Scholar 

  14. Tu R, Zhang P, Zhang R, Liu J, Lu X (2018) Modeling and assessment of precise time transfer by using beidou navigation satellite system triple-frequency signals. Sensors 18(4):1017.

    Article  Google Scholar 

  15. Tu R, Zhang P, Zhang R, Liu J, Lu X (2019a) Modeling and performance analysis of precise time transfer based on BDS triple frequency un-combined observations. J Geod 93(6):837–847

    Article  Google Scholar 

  16. Tu R, Zhang P, Zhang R, Liu J, Lu X (2019b) GNSS time offset monitoring based on the single difference among systems. IET Radar Sonar Navig,.

    Article  Google Scholar 

  17. Zhang P, Tu R, Zhang R et al (2018) Combining GPS. Remote Sens.

    Article  Google Scholar 

  18. Zhang P, Tu R, Gao Y, Liu N, Zhang R (2019) Improving Galileo’s carrier-phase time transfer based on prior constraint information. J Navig 72(1):121

    Article  Google Scholar 

  19. Zhang P, Tu R, Gao Y, Zhang R, Han J (2020) Performance of Galileo precise time and frequency transfer models using quad-frequency carrier phase observations. GPS Solution.

    Article  Google Scholar 

  20. Zumberge J, Heflin M, Jefferson D (1997) Precise point positioning for the efficient and robust analysis of GPS data from large networks. J Geophys Res.

    Article  Google Scholar 

Download references


This work is partly supported by the National Natural Science Foundation of China (Grant Nos: 41674034, 41974032, 11903040), the Chinese Academy of Sciences (CAS) programs of “High-level talents” (Grant No: Y923YC1701), and “The Frontier Science Research Project” (Grant No: QYZDB-SSW-DQC028).

Author information



Corresponding author

Correspondence to Rui Tu.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Tu, R., Zhang, P., Zhang, R. et al. Precise frequency transfer model suitable for short baseline link based on GPS single-differenced observations with ambiguity resolution. Acta Geod Geophys (2021).

Download citation


  • GPS
  • Single-differenced observation
  • Ambiguity resolution
  • Precise time transfer