Re: [gpsd-users] Help with extracting time information from GPS to NTPD

[Jordan]

Thanks!  I downloaded the ntp source and recompiled from scratch with the
SHM driver.  NTPD can now see the GPS time and is syncing to it.  Now I'm
noticing another issue where the reported time from the GPS is ~24 seconds
ahead of the public time servers.  I did a quick google search and saw this
matches up with Loran-C time vs UTC.  Is it possible the GPS is reporting in
Loran-C time?  If so, can I compensate for this in NTPD?

> From: address@hidden
> Date: Tue, 8 Nov 2011 13:02:25 +0000
> Subject: Re: [gpsd-users] Help with extracting time information from GPS to NTPD
> To: address@hidden
> CC: address@hidden
>
> On Tue, Nov 8, 2011 at 10:21, Jordan <address@hidden> wrote:
> > However I can't quite figure out how to get ntpd to pull the information
> > from gpsd. I've modified my /etc/ntp.conf to:
> >
> > Code:
> >
> > server 127.127.28.0 minpoll 4 maxpoll 4
> > fudge 127.127.28.0 refid GPS
> >
> > restrict 127.0.0.1
> > restrict 10.1.1.0 mask 255.255.255.0 nomodify notrap
> >
> > where 127.127.28.0 is supposed to be the IP to access the GPS information. I
> > can ping that IP successfully. However when I try to access the server using
> > ntpq -p, it says 'No association ID's returned'.
>
> My bet is your ntpd was compiled with options that left out the SHM
> refclock driver (or all refclocks). There should be a message from
> ntpd in syslog hinting as much.
>
> > If I stop NTPD and run 'ntpdate 127.127.28.0' it says there were no suitable
> > synchronization servers found.
>
> That's not really an IP address. 127.*.*.* are all localhost, which
> is why you can ping it. ntpd special-cases 127.127.d.u to refer to
> reference clock driver number d, unit number u. Only within ntpd do
> those IPs refer to reference clocks.
>
> Cheers,
> Dave Hart