[ntp:questions] 1000s offset between GPS module and NTP servers
Lloyd Dizon
thecarrionkind at gmail.com
Mon Jan 23 14:29:38 UTC 2017
On Mon, Jan 23, 2017 at 1:03 PM, Harlan Stenn <stenn at ntp.org> wrote:
> Lloyd Dizon writes:
> > Hi.
> > I've installed a GPS module on a Raspberry Pi and I'm getting 1000ms
> > offsets between the GPS readings and network NTPs.
> >
> > lloyd at jadzia:~ $ ntpq -p
> > remote refid st t when poll reach delay offset
> > jitter
> > ============================================================
> =================
> > =
> > LOCAL(0) .LOCL. 10 l 447 64 100 0.000 0.000
> > 0.001
>
> Why are you using the LOCAL refclock?
>
I shouldn't. I removed it now.
> xGPS_NMEA(0) .GPS. 0 l - 16 377 0.000 6.229
> > 142.320
>
> Is your NMEA source identifying the wrong second?
>
> > *ntp0.as34288.ne 85.158.25.74 2 u 24 64 3 9.810 1004.83
> > 1.687
> > +246.11.25.212.f 162.23.41.10 2 u 19 64 3 10.636 1004.22
> > 1.376
> > +ch-ntp01.10g.ch 81.94.123.17 3 u 21 64 3 10.493 1001.79
> > 3.299
> > -khyber.madduck. 192.33.96.102 2 u 20 64 3 8.703 1001.72
> > 4.474
>
> Your NMEA source is sending ntpd samples every 16 seconds. It's filling
> the sample buffer, and the the other sources (are you using iburst on
> these? You should be...) are taking a while to provide enough samples
> to detect that your NMEA source is "off" by a second.
>
I changed the min and maxpoll to 6 to be consistent with the network
servers.
I'm still getting a 1000ms offset though.
> Anybody has a clue what is going on?
>
> I think your NMEA signal is identifying the wrong second.
>
So my NMEA device is broken then. Is there a way to compensate manually if
the device is systematically adding (or subtracting) 1000ms. Is is correct
to compensate manually.
I looked at the time1 argument to fudge but I only had 300ms removed from
the offset.
Before using "time1 1":
Every 1.0s: ntpq
-pn
Mon Jan 23 15:27:46 2017
remote refid st t when poll reach delay offset
jitter
==============================================================================
x127.127.20.0 .GPS. 0 l 48 64 17 0.000 10.095
6.428
*178.209.53.202 166.171.80.13 3 u 31 64 37 11.298 1015.56
9.837
+81.94.123.16 85.158.25.74 2 u 30 64 37 9.788 1013.30
9.577
+212.51.144.44 .PPS. 1 u 28 64 37 9.864 1013.35
9.723
+82.197.188.130 195.186.1.100 3 u 32 64 37 9.832 1013.75
9.664
After using time1 1:
Every 1.0s: ntpq
-pn
Mon Jan 23 15:28:27 2017
remote refid st t when poll reach delay offset
jitter
==============================================================================
127.127.20.0 .GPS. 0 l 16 64 0 0.000 0.000
0.001
*192.33.96.102 .PPS. 1 u 4 64 1 13.617 721.727
0.112
+5.148.175.134 131.188.3.222 2 u 4 64 1 9.377 720.615
0.436
+81.94.123.17 85.158.25.74 2 u 3 64 1 9.659 720.234
0.552
-46.22.26.12 162.23.41.56 2 u 2 64 1 15.923 722.333
0.171
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