[ntp:questions] Reasons of NTP not to use GPS source
pavlov.ig at gmail.com
Mon Sep 16 07:51:08 UTC 2013
I already tryed to use PPS from my GPS receiver connected to DCD-pin of the
But I had PPS also marked as "x", that is why I tryed first to fix problems
with NMEA-based GPS data separate from PPS.
I will try to connect PPS again.
But I can't understand why it is marked "x"? What is wrong with it?
2013/9/16 Rob <nomail at example.com>
> Igor Pavlov <pavlov.ig at gmail.com> wrote:
> > Hi!
> > I am using GPS-receiver based on Geos-1m chip (
> > http://www.geostar-navigation.com/en/navigation_05.html)
> > I connected it to serial port and configured NTP.
> > It becomes unused by NTP: when do ntpq -p reuest ti puts "x" near
> > "GPS_NMEA(1)" record.
> > What reasons can be for this?
> A GPS with NMEA protocol is usually a very lousy time source.
> You can see this in your output: the time offset relative to
> the internet sources is very large:
> > remote refid st t when poll reach delay offset
> > jitter
> > xGPS_NMEA(1) .GPS. 0 l 14 16 377 0.000 -303.07
> > 4.292
> > *stratum1.net .PPS. 1 u 62 64 377 62.800 -68.052
> > 43.693
> > +dl120g7.naviteh 188.8.131.52 2 u 58 64 377 30.151 -100.04
> > 52.432
> > +184.108.40.206 220.127.116.11 2 u - 64 377 10.006 -105.88
> > 64.279
> That is why ntpd declares the time as invalid and attempts to use the
> 3 other sources instead.
> When you want to fix this, you should use PPS with the receiver,
> when possible.
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