On Sun, Feb 19, 2012 at 16:32, unruh <[email protected]> wrote: > On 2012-02-19, Rob <[email protected]> wrote: >> Don't try to use NMEA for timesyncing! It will only drive you crazy. > > No. It is fine. > >> The timestamp in NMEA is a "time of last fix", not the current time. > > And ntpd allows you to alter the offset timestamp to account for the > delay in the end of the nmea message coming through. That it uses the > end of the message rather than the beginning causes excess jitter, but > that is never anywhere near 5000ms.
To elaborate a wee bit, each NMEA sentence parsed by the driver effectively has two timestamps. One is the timestamp implied by the sentence text, which typically has 1s precision. The other is the timestamp the complete line was received, which has higher precision but reflects the transmission time and benefits from fudge time2 being calibrated to match. Cheers, Dave Hart _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
