Characterization of between-receiver GPS-Galileo inter-system biases and their effect on mixed ambiguity resolution
The Global Positioning System (GPS) and Galileo will transmit signals on similar frequencies, that is, the L1–E1 and L5–E5a frequencies. This will be beneficial for mixed GPS and Galileo applications in which the integer carrier phase ambiguities need to be resolved, in order to estimate the positioning unknowns with centimeter accuracy or better. In this contribution, we derive the mixed GPS + Galileo model that is based on “inter-system” double differencing, that is, differencing the Galileo phase and code observations relative to those corresponding to the reference or pivot satellite of GPS. As a consequence of this, additional between-receiver inter-system bias (ISB) parameters need to be solved as well for both phase and code data. We investigate the size and variability of these between-receiver ISBs, estimated from L1 and L5 observations of GPS, as well as E1 and E5a observations of the two experimental Galileo In-Orbit Validation Element (GIOVE) satellites. The data were collected using high-grade multi-GNSS receivers of different manufacturers for several zero- and short-baseline setups in Australia and the USA. From this analysis, it follows that differential ISBs are only significant for receivers of different types and manufacturers; for baselines formed by identical receiver types, no differential ISBs have shown up; thus, implying that the GPS and GIOVE data are then fully interoperable. Fortunately, in case of different receiver types, our analysis also indicates that the phase and code ISBs may be calibrated, since their estimates, based on several datasets separated in time, are shown to be very stable. When the single-frequency (E1) GIOVE phase and code data of different receiver types are a priori corrected for the differential ISBs, the short-baseline instantaneous ambiguity success rate increases significantly and becomes comparable to the success rate of mixed GPS + GIOVE ambiguity resolution based on identical receiver types.
KeywordsGPS-Galileo interoperability Between-receiver inter-system bias Integer ambiguity resolution GIOVE
This work has been conducted in the context of the Australian Space Research Program (ASRP) project “Platform Technologies for Space, Atmosphere and Climate”. The second author is the recipient of an Australian Research Council (ARC) Federation Fellowship (project number FF0883188). Curtin colleague Dr. Bofeng Li was responsible for conducting the Bentley/Muresk experiment. All this support is gratefully acknowledged.
- de Bakker PF, Tiberius CCJM, van der Marel H, van Bree RJP (2012) Short and zero baseline analysis of GPS L1 C/A, L5Q, GIOVE E1B, and E5aQ signals. GPS Solut 16:53–64Google Scholar
- Bonhoure B, Boulanger C, Legenne J (2009) GPS—GIOVE mixed PVT experimentation. Proceedings of ION GNSS 2009, Savannah, GA, 22–25 Sep, pp 2996–3007Google Scholar
- Cao W, Hauschild A, Steigenberger P, Langley RB, Urquhart L, Santos M, Montenbruck O (2010) Performance evaluation of integrated GPS-GIOVE precise point positioning. Proceedings of ION ITM 2010, San Diego, CA, 25–27 Jan, pp 540–552Google Scholar
- Colomina I et al (2011) The accuracy potential of Galileo E5/E1 pseudoranges for surveying and mapping. Proceedings of ION GNSS 2011, Portland, OR, 19–23 Sep, pp 2332–2340Google Scholar
- Hahn JH, Powers ED (2005) Implementation of the GPS to Galileo time offset (GGTO), Proceedings of 2005 joint IEEE international frequency control symposium and precise time & time interval (PPTI) Systems & applications meeting, 29–31 Aug, Vancouver, Canada, pp 33–37Google Scholar
- Hegarty C, Powers E, Fonville B (2004) Accounting for timing biases between GPS, modernized GPS, and Galileo signals. Proceedings of 36th annual precise time and time interval (PTTI) Meeting, Washington, DC, 7–9 Dec, pp 307–317Google Scholar
- Hofmann-Wellenhof B, Lichtenegger H, Wasle E (2008) GNSS—global navigation satellite systems: GPS, GLONASS Galileo & more. Springer, Wien-New YorkGoogle Scholar
- Milbert D (2005) Influence of pseudorange accuracy on phase ambiguity resolution in various GPS modernization scenarios. Navig J Inst Navig 52(1):29–38Google Scholar
- Simsky A, Mertens D, Sleewaegen JM, De Wilde W, Hollreiser M, and Crisci M (2008) Multipath and tracking performance of Galileo ranging signals transmitted by GIOVE-B. Proceedings of ION GNSS 2008, Savannah, GA, 16–19 Sep, pp 1525–1536Google Scholar
- Sleewaegen, JM (2012) New GNSS signals: how to deal with the plethora of observables? Presentation at IGS bias workshop, University of Bern, Switzerland, 18–19 JanGoogle Scholar
- Teunissen PJG (1997) A canonical theory for short GPS baselines—Part II: the ambiguity precision and correlation. J Geodesy 71:89–401Google Scholar
- Tiberius C, Pany T, Eissfeller B, de Jong K, Joosten P, Verhagen S (2002) Integral GPS-Galileo ambiguity resolution. Proceedings of ENC-GNSS 2002, The European Navigation Conference, Copenhagen, Denmark, 27–30 May 2002, CD ROMGoogle Scholar