Gps Time Clock Offset

In order to be more useful for timing applications gps messages contain an offset between gps and utc time which allows current utc time to be calculated by a low cost ground based receiver.

Gps time clock offset.

The gps navigation message includes the difference between gps time and utc. Gps time was set to match utc in 1980 but has since diverged. While gps time itself is designed to be kept within one microsecond 1 µsec or one millionth of a second of utc excepting leap seconds the satellite clocks can be allowed to drift up to a millisecond 1 msec or one thousandth of a second from gps time. Periodic corrections are performed to the on board clocks to keep them synchronized with ground clocks.

Periodic corrections are performed to the on board clocks to keep them synchronized with ground clocks. Gps global positioning system time is the atomic time scale implemented by the atomic clocks in the gps ground control stations and the gps satellites themselves. As of march 2019 the gps time scale is 18 seconds ahead of utc. As leap seconds are introduced over time gps time diverges further and further from utc.

The lack of corrections means that gps time remains at a constant offset with international atomic time tai tai gps 19 seconds. The onboard satellite clocks are independent of one another. Gps time was zero at 0h 6 jan 1980 and since it is not perturbed by leap seconds gps is now ahead of utc by loran c long range navigation time is an atomic time scale implemented.