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Time References in GNSS
| Fundamentals | |
|---|---|
| Title | Time References in GNSS |
| Author(s) | J. Sanz Subirana, JM. Juan Zornoza and M. Hernandez-Pajares, University of Catalunia, Spain. |
| Level | Basic |
| Year of Publication | 2011 |
Regarding the GNSS, the GPS Time (GPST), GLONASS Time (GLONASST) and Galileo System Time (GST) are the reference times used in GPS, GLONASS and Galileo applications, respectively.
GPST is defined by the GPS Control segment on the basis of a set of atomic clocks aboard the satellites and in the Monitor Stations. It is synchronised with the UTC(USNO) at nanosecond level. The origin epoch of GPS time is 0h UTC (midnight) of January 5th to 6th of 1980 (6d· 0). At that epoch, the difference TAI−UTC was 19 seconds, thence GPS−UTC=n − 19s.
GLONASST is generated by the GLONASS Central Synchroniser and the differ- ence between the UTC(SU) and GLONASST should not exceed 1 millisecond plus three hours[footnote 1] (i.e.,[math]\displaystyle{ t_{GLONASS}=t_{UTC(SU)}+3^h-\tau }[/math], where [math]\displaystyle{ |\tau|\lt 1
milisec. }[/math]).
GST will be maintained by the Galileo Central Segment and synchronised with TAI with a nominal offset below 50 ns. The starting time of Galileo system is not already defined.
Notes
- ^ The difference between Moscow Time and Greenwich Mean Time (GMT).
References
- Hofmann-Wellenhof, B., Legat, K. and Wieser, M., 2003. Navigation. Principles of positioning and guidance. Springer-Verlag, Wien, Austria.