The long term stability of GPS is very good. Some one here will point out exactly how one measures it. But roughly when speaking of accuracy you always need to specify a time interval. For example if the 1PPS is "off" by 15ns that is not bad and yes there are much better systems if you need to measure time intervals on the order of one second. But if the signal is "off" by 15 ns over 100,000 seconds that is well, 100,000 time better.
This is a basic reference and for some specialized end use case you might couple it with other equipment. Many of the concerns you had, such as effects of the atmosphere get averaged out because the unit is looking at satellites from all over the sky. (averaging over space) And you do git better results with better antenna locations that are away from multi-path and have a 360 degree view of the horizon. But notice the unit has an temperature stabilized crystal oscillator that is stable over many seconds. an is much more stable in the short term then is a GPS receiver. Trimble uses this crystal to average over time You also have to ask where is the tine data going to be used. Are you synchronizing a computer's internal clock or trying to measure the frequency of a microwave transmitter SO it falls back to the old thing about there being no "better" only better for a specific use case. Some of use were lucky enough to buy Trimble Thunderbolts, a previous version of this unit when they were on eBay for $100 each. For those without 5 digits budget they ar pretty much the Gold Standard. I have mine installed with a good filtered DC power supply and an outdoor antenna on mast well above the roofs of surrounding buildings. I get long term stability of about one part in 10E13. Yes 13 digits over long periods. (I think?) It is really hard to know because my measurement system is a little circular referenced On Thu, May 25, 2017 at 6:27 AM, Ebrahim Roghanizad <e.roghani...@gmail.com> wrote: > Dear members > > I am a new amateur member in your group. Maybe my question has been asked. > Recently I found Trimble Mini-T GG, whose data sheet is attached, as a good > GNSS disciplined time reference. I would like to know if there exists a > more accurate one, since it does not employ dual frequencies to compensate > ionospheric delay, though it handles both GPS and GLONASS. Besides, could > anyone guide me about the presented accuracy in the datasheet? There, it is > stated that "When operating in Over Determined Timing Mode, the accuracy of > pulse per second (PPS) is within 15 nanoseconds of GNSS/UTC." Does it mean > that it includes both bias and the noise? In other words, is it true to say > that "The time-synchronization error between two of them with a long > distance is less than 2*15 ns"? > > Best Regards > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. -- Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.