[ntp:questions] Re: HELP PLEASE::: NTP Garmin GPS 18lvc with PPS andgpsd

David J Taylor david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk
Mon Jul 31 17:38:28 UTC 2006


sleek daelite wrote:
> <questions at lists.ntp.isc.org>Hey guys,
>
> Could anyone help me with Garmin GPS 18lvc device that comes with PPS
> output. I've been trying to configure the device to achieve about 1ms
> accuracy. The specification of this device states it could achieve
> about 1ns accuracy. Im quite puzzled as to why i can't achieve such
> accuracy. My software include:
>
> ntp-4.2.2p3-RC
> Debian  Kernel 2.6.16-2-486
> gpsd 2.33

I believe that those who get the best accuracies use FreeBSD.

I would have thought that 1ms was quite easy to achieve, providing your 
GPS has a good view of the whole sky hemishpere.  Even my own system gets 
10 - 20us and it can hardly see half the sky!

  http://www.david-taylor.myby.co.uk/mrtg/pixie_ntp.html

  http://www.david-taylor.myby.co.uk/ntp/FreeBSD-GPS-PPS.htm

and that's just using an old Pentium 133 with 48MB memory....

David 





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