[ntp:questions] UTC Time from NMEA receiver one second behind DCF?

David J Taylor david-taylor at blueyonder.neither-this-bit.nor-this-bit.co.uk
Fri Aug 15 19:24:55 UTC 2008


Harald Brinkmann wrote:
[]
> Just in case anyone is interested: The bug is active again right now
> (2008-08-15T18:27 UTC).
>
> Here is a sample ntpq -p
>
>     remote           refid      st t when poll reach   delay   offset
> jitter
> ==============================================================================
> LOCAL(0)        .LOCL.          10 l   53   64    3    0.000    0.000
> 3.906
> GPS_NMEA(0)     .GPS.            3 l   51   64    3    0.000  -987.23
> 224.958
> ptbtime2.ptb.de .PTB.            1 u   51   64    3   70.359   21.022
> 58.591
>
> Here are a couple of NMEA messages off my Navilock:
>
> $GPRMC,182711.000,A,5212.1284,N,00833.4496,E,0.51,173.76,150808,,*07
> $GPVTG,173.76,T,,M,0.51,N,0.9,K*69
> $GPGGA,182712.000,5212.1283,N,00833.4497,E,1,06,1.1,83.1,M,47.1,M,,0000*67
> $GPGSA,A,3,24,21,30,29,13,31,,,,,,,2.1,1.1,1.7*3A
> $GPRMC,182712.000,A,5212.1283,N,00833.4497,E,0.78,163.32,150808,,*08
> $GPVTG,163.32,T,,M,0.78,N,1.5,K*6E
> $GPGGA,182713.000,5212.1282,N,00833.4497,E,1,06,1.1,83.0,M,47.1,M,,0000*66
> $GPGSA,A,3,24,21,30,29,13,31,,,,,,,2.1,1.1,1.7*3A
> $GPRMC,182713.000,A,5212.1282,N,00833.4497,E,0.43,182.94,150808,,*03
> $GPVTG,182.94,T,,M,0.43,N,0.8,K*69
> $GPGGA,182714.000,5212.1282,N,00833.4497,E,1,05,1.2,82.9,M,47.1,M,,0000*69
>
> When talking about a workaround I was thinking about a combination of
> statuses that are found in these messages that only occurs when the
> bug is active. Trying to guess the times at which it will strike is
> clearly pointless.
>
> Nevertheless the Garmin unit is on order.
>
> BTW: I didn't know that ordering GPS units from the U.S. would be
> *that* difficult. :-(
>
> Cheers
>
> Harald

Harald,

I know it's difficult to judge, but looking at my SiRF-based GPS 60 CSx, 
at 19:19 UTC, I could have been persuaded that the time indication did 
change 1second after the exact 19:19:00 time (from NTP & a different GPS 
unit).

Someone will probably tell me that the offset should have been the other 
way!

(Yes, some US suppliers don't like "foreign" business - I bought my GPS18 
from my own country!).

Cheers,
David 





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