[ntp:questions] Reasons of NTP not to use GPS source
Mark C. Stephens
marks at non-stop.com.au
Mon Sep 16 10:44:59 UTC 2013
Igor, please post the contents of
From: questions-bounces+marks=non-stop.com.au at lists.ntp.org [mailto:questions-bounces+marks=non-stop.com.au at lists.ntp.org] On Behalf Of Igor Pavlov
Sent: Monday, 16 September 2013 5:56 PM
Subject: Re: [ntp:questions] Reasons of NTP not to use GPS source
Sorry, didn't see the first part of your answer.
I thought that offset - it's offset of current system time from NMEA-based info.
But if system time would be set to this NMEA-based time, than offset would not be so great. Isn't it?
But NTP prefer to sync to other sources - Why?
2013/9/16 Igor Pavlov <pavlov.ig at gmail.com>
> I already tryed to use PPS from my GPS receiver connected to DCD-pin
> of the same RS-232.
> 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 22.214.171.124 2 u 58 64 377 30.151 -100.04
>> > 52.432
>> > +126.96.36.199 188.8.131.52 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
>> questions mailing list
>> questions at lists.ntp.org
> Игорь Павлов
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