Gps Time Clock Offset

As leap seconds are introduced over time gps time diverges further and further from utc.

Gps time clock offset.

The gps navigation message includes the difference between gps time and utc. Periodic corrections are performed to the on board clocks to keep them synchronized with ground clocks. 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. 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.

As of march 2019 the gps time scale is 18 seconds ahead of utc. In brief the offset represents the difference between what time the receiver thinks it is and the true time with the latter determined by the underlying gnss atomic time scale. Periodic corrections are performed to the on board clocks to keep them synchronized with ground clocks. The onboard satellite clocks are independent of one another.

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 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. The lack of corrections means that gps time remains at a constant offset with international atomic time tai tai gps 19 seconds.