[ntp:questions] PPS versus serial offset

Steve Kostecke kostecke at ntp.org
Wed Aug 28 12:26:03 UTC 2013


On 2013-08-28, detha <detha at foad.co.za> wrote:

> Done the 'let it run for 24 hours, take average offset between PPS and
> serial reading, and use that as time1 for the gpsd line in ntp.conf.'

Where did you find that bad advice?

A timing GPS provides two pieces of information:

1. The PPS signal which marks the seconds

2. NMEA sentences which label the seconds

The PPS signal is emitted at the beginning of each second and is
non-preemptable.

The NMEA sentences are emitted when the GPS receiver is not busy with
other tasks and can occur at any time during the relevant second.

-- 
Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/



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