Well, the whole point of the exercise is to see how well you can do if you DON'T have an internet connection, a 1PPS signal, or a stratum 1 time server available... only the humble messages coming from a 10 dollar GPS receiver. Try getting a net connection in the middle of the Gobi desert (where one user uses Lady Heather's time sync feature to keep their system clocks reasonably accurate). If you can put the receiver into a binary message mode, you can usually do better than NMEA (but, surprisingly, usually not by much). And by selecting a receiver that has known good / stable message timing you can do surprisingly well. ---------------------- > I feel that using the serial NMEA stream would, today, be a last resort, as an Internet sync would be considerably better. Would you agree with that?

As an exercise it might be fun to try to do the best you can with just NMEA. But practically speaking even my very $10, 8-channel motorola GPS receiver can output a PPS to about 50ns. Better then needed for NTP. You friend in the Gobi desert would be better off my $10 GPS That said, if you had a good local oscillator you could make a decent GPSDO using NMEA only with a VERY long time constant On Mon, Aug 1, 2016 at 9:23 AM, Mark Sims <holrum@hotmail.com> wrote: > Well, the whole point of the exercise is to see how well you can do if you DON'T have an internet connection, a 1PPS signal, or a stratum 1 time server available... only the humble messages coming from a 10 dollar GPS receiver. Try getting a net connection in the middle of the Gobi desert (where one user uses Lady Heather's time sync feature to keep their system clocks reasonably accurate). > > > If you can put the receiver into a binary message mode, you can usually do better than NMEA (but, surprisingly, usually not by much). And by selecting a receiver that has known good / stable message timing you can do surprisingly well. > > > ---------------------- > > >> I feel that using the serial NMEA stream would, today, be a last resort, as an Internet sync would be considerably better. Would you agree with that? > > > _______________________________________________ > 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

From: Mark Sims Well, the whole point of the exercise is to see how well you can do if you DON'T have an internet connection, a 1PPS signal, or a stratum 1 time server available... only the humble messages coming from a 10 dollar GPS receiver. Try getting a net connection in the middle of the Gobi desert (where one user uses Lady Heather's time sync feature to keep their system clocks reasonably accurate). If you can put the receiver into a binary message mode, you can usually do better than NMEA (but, surprisingly, usually not by much). And by selecting a receiver that has known good / stable message timing you can do surprisingly well. ======================================== Well, yes, but if you choose a GPS receiver wisely it also has PPS, even on some of the cheapest eBay units. Of course, what is best depends on what accuracy the user needs, and how much they are prepared to pay. Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-taylor@blueyonder.co.uk Twitter: @gm8arv