Journal of Geodesy

, Volume 92, Issue 11, pp 1267–1283 | Cite as

Real-Time Precise Point Positioning (RTPPP) with raw observations and its application in real-time regional ionospheric VTEC modeling

  • Teng Liu
  • Baocheng ZhangEmail author
  • Yunbin Yuan
  • Min Li
Original Article


Precise Point Positioning (PPP) is an absolute positioning technology mainly used in post data processing. With the continuously increasing demand for real-time high-precision applications in positioning, timing, retrieval of atmospheric parameters, etc., Real-Time PPP (RTPPP) and its applications have drawn more and more research attention in recent years. This study focuses on the models, algorithms and ionospheric applications of RTPPP on the basis of raw observations, in which high-precision slant ionospheric delays are estimated among others in real time. For this purpose, a robust processing strategy for multi-station RTPPP with raw observations has been proposed and realized, in which real-time data streams and State-Space-Representative (SSR) satellite orbit and clock corrections are used. With the RTPPP-derived slant ionospheric delays from a regional network, a real-time regional ionospheric Vertical Total Electron Content (VTEC) modeling method is proposed based on Adjusted Spherical Harmonic Functions and a Moving-Window Filter. SSR satellite orbit and clock corrections from different IGS analysis centers are evaluated. Ten globally distributed real-time stations are used to evaluate the positioning performances of the proposed RTPPP algorithms in both static and kinematic modes. RMS values of positioning errors in static/kinematic mode are 5.2/15.5, 4.7/17.4 and 12.8/46.6 mm, for north, east and up components, respectively. Real-time slant ionospheric delays from RTPPP are compared with those from the traditional Carrier-to-Code Leveling (CCL) method, in terms of function model, formal precision and between-receiver differences of short baseline. Results show that slant ionospheric delays from RTPPP are more precise and have a much better convergence performance than those from the CCL method in real-time processing. 30 real-time stations from the Asia-Pacific Reference Frame network are used to model the ionospheric VTECs over Australia in real time, with slant ionospheric delays from both RTPPP and CCL methods for comparison. RMS of the VTEC differences between RTPPP/CCL method and CODE final products is 0.91/1.09 TECU, and RMS of the VTEC differences between RTPPP and CCL methods is 0.67 TECU. Slant Total Electron Contents retrieved from different VTEC models are also validated with epoch-differenced Geometry-Free combinations of dual-frequency phase observations, and mean RMS values are 2.14, 2.33 and 2.07 TECU for RTPPP method, CCL method and CODE final products, respectively. This shows the superiority of RTPPP-derived slant ionospheric delays in real-time ionospheric VTEC modeling.


Real time PPP with raw observations SSR corrections Slant ionospheric delays Ionospheric VTEC modeling 



The authors would like to acknowledge the IGS, GA (Geoscience Australia), CNES and CODE for providing access to the real-time data streams, SSR satellite orbit and clock corrections, post-processed DCB and GIM products. We would like to express our great appreciation to Weixin He for kindly providing the IGG NTRIP software and related technical supports. Funding supports from Collaborative Precision Positioning Project funded by Ministry of Science and Technology of China (No. 2016YFB0501900) and China Natural Science Funds (Nos. 41231064, 41674022, 41621091) are also gratefully acknowledged. The second author is supported by the CAS Pioneer Hundred Talents Program.


  1. Bisnath S, Gao Y (2007) Current state of precise point positioning and future prospects and limitations. Observing our changing planet. IAG Symp 133:615–624Google Scholar
  2. Choy S, Bisnath S, Rizos C (2017) Uncovering common misconceptions in GNSS Precise Point Positioning and its future prospect. GPS Solut 21(1):13–22CrossRefGoogle Scholar
  3. Colombo OL (2008) Real-time, wide-area, precise kinematic positioning using data from internet NTRIP streams. In: Proceedings of ION-GNSS-2008, Institute of Navigation, Savannah, Georgia, pp 327–337Google Scholar
  4. Ciraolo L, Azpilicueta F, Brunini C et al (2007) Calibration errors on experimental slant total electron content (TEC) determined with GPS. J Geod 81(2):111–120CrossRefGoogle Scholar
  5. Defraigne P, Baire Q, Guyennon N (2007) GLONASS and GPS PPP for time and frequency transfer. In: Frequency control symposium, 2007 joint with the 21st European frequency and time forum. IEEE international, pp 909–913Google Scholar
  6. Elsobeiey M, Al-Harbi S (2016) Performance of real-time Precise Point Positioning using IGS real-time service. GPS Solut 20(3):565–571CrossRefGoogle Scholar
  7. Feltens J (2003) The activities of the ionosphere working group of the International GPS Service (IGS). GPS Solut 7(1):41–46CrossRefGoogle Scholar
  8. Feltens J, Angling M, Jackson-Booth N et al (2011) Comparative testing of four ionospheric models driven with GPS measurements. Radio Sci 46(6):1–11CrossRefGoogle Scholar
  9. Ge M, Chen J, Douša J et al (2012) A computationally efficient approach for estimating high-rate satellite clock corrections in realtime. GPS Solut 16(1):9–17CrossRefGoogle Scholar
  10. Gu S, Lou Y, Shi C et al (2015) BeiDou phase bias estimation and its application in precise point positioning with triple-frequency observable. J Geod 89(10):979–992CrossRefGoogle Scholar
  11. Guo F, Zhang X, Wang J et al (2016) Modeling and assessment of triple-frequency BDS precise point positioning. J Geod 90(11):1223–1235CrossRefGoogle Scholar
  12. Hadas T, Bosy J (2015) IGS RTS precise orbits and clocks verification and quality degradation over time. GPS Solut 19(1):93–105CrossRefGoogle Scholar
  13. Haines G (1988) Computer programs for spherical cap harmonic analysis of potential and general fields. Comput Geosci 14(4):413–447CrossRefGoogle Scholar
  14. Hernández-Pajares M, Juan JM, Sanz J et al (2009) The IGS VTEC maps: a reliable source of ionospheric information since 1998. J Geod 83(3–4):263–275CrossRefGoogle Scholar
  15. Hernández-Pajares M, Juan JM, Sanz J et al (2011) The ionosphere: effects, GPS modeling and the benefits for space geodetic techniques. J Geod 85(12):887–907CrossRefGoogle Scholar
  16. Kouba J, Héroux P (2001) Precise point positioning using IGS orbit and clock products. GPS Solut 5(2):12–28CrossRefGoogle Scholar
  17. Kuo C, Chiu K, Chiang K et al (2012) High-frequency sea level variations observed by GPS buoys using precise point positioning technique. Terr Atmos Ocean Sci 23(2):209–218CrossRefGoogle Scholar
  18. Lou Y, Zheng F, Gu S, Wang C, Guo H, Feng Y (2016) Multi-GNSS precise point positioning with raw single-frequency and dual-frequency measurement models. GPS Solut 20(4):849–86CrossRefGoogle Scholar
  19. Li X, Ge M, Zhang X, Zhang Y, Guo B, Wang R, Klotz J, Wickert J (2013) Real-time high-rate co-seismic displacement from ambiguity-fixed precise point positioning: application to earthquake early warning. Geophys Res Lett 40(2):295–300CrossRefGoogle Scholar
  20. Li X, Ge M, Dai X, Ren X, Fritsche M, Wickert J, Schuh H (2015a) Accuracy and reliability of multi-GNSS real-time precise positioning: GPS, GLONASS, BeiDou, and Galileo. J Geod 89(6):607–635CrossRefGoogle Scholar
  21. Li X, Dick G, Lu C et al (2015b) Multi-GNSS meteorology: real-time retrieving of atmospheric water vapor from BeiDou, Galileo, GLONASS, and GPS observations. IEEE Trans Geosci Remote Sens 53(12):6385–6393CrossRefGoogle Scholar
  22. Li Z (2012) Study on the mitigation of ionospheric delay and the monitoring of global ionospheric TEC based on GNSS/compass. Ph. D. thesis, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan, China (in Chinese)Google Scholar
  23. Li Z, Yuan Y, Wang N et al (2015c) SHPTS: towards a new method for generating precise global ionospheric TEC map based on spherical harmonic and generalized trigonometric series functions. J Geod 89(4):331–345CrossRefGoogle Scholar
  24. Liu T, Yuan Y, Zhang B et al (2017) Multi-GNSS Precise Point Positioning (MGPPP) using raw observations. J Geod 91(3):253–268CrossRefGoogle Scholar
  25. Mannucci A, Wilson B, Yuan D, Ho C, Lindqwister U, Runge T (1998) A global mapping technique for GPS-derived ionospheric total electron content measurements. Radio Sci 33(3):565–582CrossRefGoogle Scholar
  26. Marques HA, Monico JFG, Aquino M (2011) RINEX_HO: second-and third-order ionospheric corrections for RINEX observation files. GPS Solut 15(3):305–31CrossRefGoogle Scholar
  27. Montenbruck O, Hauschild A, Steigenberger P (2014) Differential code bias estimation using multi-GNSS observations and global ionosphere maps. Navigation 61(3):191–201CrossRefGoogle Scholar
  28. Rovira-Garcia A, Juan J, Sanz J et al (2016) Accuracy of ionospheric models used in GNSS and SBAS: methodology and analysis. J Geod 90(3):229–240CrossRefGoogle Scholar
  29. Schaer S (1999) Mapping and predicting the earth’s ionosphere using the global positioning system. Ph.D Dissertation, University of Berne, SwitzerlandGoogle Scholar
  30. Shi C, Fan L, Li M et al (2016) An enhanced algorithm to estimate BDS satellite’s differential code biases. J Geod 90(2):161–177CrossRefGoogle Scholar
  31. Tegedor J, Øvstedal O (2014) Triple carrier precise point positioning (PPP) using GPS L5. Surv Rev 46(337):288–297CrossRefGoogle Scholar
  32. Teunissen P (1985) Generalized inverses, adjustment, the datum problem and S-transformations. In: Sanso F, Grafarend EW (eds) Optimization of geodetic networks. Springer, Berlin, pp 11–55CrossRefGoogle Scholar
  33. Teunissen P, Khodabandeh A (2015) Review and principles of PPP-RTK methods. J Geod 89(3):217–240CrossRefGoogle Scholar
  34. Weber G, Mervart L, Lukes Z, Rocken C, Dousa J (2007) Real-time clock and orbit corrections for improved point positioning via NTRIP. In: Proceedings of ION-GNSS-2007, Institute of Navigation, 25–28 Sept, Fort Worth, TX, USA, pp 1992–1998Google Scholar
  35. Zhang B, Ou J, Yuan Y, Li Z (2012) Extraction of line-of-sight ionospheric observables from GPS data using precise point positioning. Sci China Earth Sci 55(11):1919–1928CrossRefGoogle Scholar
  36. Zhang B (2016) Three methods to retrieve slant total electron content measurements from ground-based GPS receivers and performance assessment. Radio Sci 51(7):972–988CrossRefGoogle Scholar
  37. Zhang X, Andersen O (2006) Surface Ice flow velocity and tide retrieval of the Amery ice shelf using precise point positioning. J Geod 80(4):171–176CrossRefGoogle Scholar
  38. Zumberge J, Heflin M, Jefferson D, Watkins M, Webb F (1997) Precise point positioning for the efficient and robust analysis of GPS data from large networks. J Geophys Res 102(B3):5005–5017CrossRefGoogle Scholar

Copyright information

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

Authors and Affiliations

  1. 1.State Key Laboratory of Geodesy and Earth’s Dynamics, Institute of Geodesy and GeophysicsChinese Academy of SciencesWuhanPeople’s Republic of China

Personalised recommendations