[ntp:questions] Align PPS to UTC or GPS?

juergen perlinger juergen.perlinger at t-online.de
Wed Feb 10 20:37:16 UTC 2016

On 02/10/2016 07:24 PM, Neil Green wrote:
> I'm configuring a Skytraq Venus GPS module and have the option to align the PPS output to GPS or UTC. Which one is best for use over serial with NTP?

IMHO that's a funny configuration option, as the difference between UTC
and GPS time scale is an integral number of seconds, by definition. So
it should not matter for a true PPS, that is, 1 pulse per second.

This *might* be a difference if the 'PPS' is given every n-th second
(say, every 5 or 10 seconds) and you want one pulse at second zero of
the minute.

Since NTPD syncs to UTC(*), I would suggest the UTC option, and don't be
afraid to have the pulse every second, because it shouldn't make a
difference anyway in that case.

Unless I failed to grasp something?!?

(*) The truth is more complicated, but for all practical purposes it's
easiest to assume NTPD works with UTC.


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