Preliminary results of using GPS to look for clock skew
jan.ceuleers at gmail.com
Fri Sep 23 05:24:40 EDT 2011
Can I suggest another method for your comparisons of GPS time to ntp (or
rather network) time?
The whole purpose of ntpd is to compare multiple sources of time,
whether local refclocks such as a GPS receiver or remote-ones. In fact,
when acquiring a new refclock and before pressing it into service it is
necessary to calibrate the offset between its PPS signal (as seen by the
ntpd process, and therefore incorporating the propagation delay in the
cable, in the receiver circuit and the processing delay in the OS) and
the true UTC second.
This is done by adding the new refclock to the ntpd config file, but by
also telling ntpd to distrust it (using the noselect keyword). You can
then leverage all of ntpd's stats for comparing the refclock to all
other available time sources.
More info at www.ntp.org.
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