[ntp:questions] Too much offset from GPS?

chowalit.lab Chowalit Lab Linux chowalit.lab at gmail.com
Tue Mar 11 04:26:38 UTC 2008


Thanks all,
      So It's wrong on my GPS (GPSmap60). Oh... So If I still use this
GPS I should add offset with fudge option. Can I get other source from
this GPS?

Thank Again
Chong

On Sat, Mar 8, 2008 at 10:46 PM, Unruh <unruh-spam at physics.ubc.ca> wrote:
> isw <isw at witzend.com> writes:
>
> >In article <Z_jAj.87237$C61.22584 at edtnps89>,
> > Unruh <unruh-spam at physics.ubc.ca> wrote:
>
> >> Steve Kostecke <kostecke at ntp.org> writes:
> >>
> >> >On 2008-03-07, Hal Murray wrote:
> >>
> >> >>ATTRIBUTION MISSING wrote:
> >> >>
> >> >>>I have problem with my stratum1 box. My box include: freebsd
> >> >>>5.2-RELEASE without PPS , ntp-4.2.0_1, Intel Pentium III, 40 G IDE,
> >> >>>Germin GPSmap60 , connect with serial com. In GPSmap60 set as NMEA.
> >> >>>Freebsd box can get NMEA input string. My configuration of ntp.conf
> >> >>>like this:
> >> >>>
> >> >>>server 127.127.20.0 mode 1 prefer minpoll 4
> >> >>>server  127.127.1.0 minpoll 5
> >> >>
> >> >> Most NMEA devices (or at least all the ones I've worked with)
> >> >> send their text with a significant offset.
> >>
> >> >It gets even better ... NMEA sentences are output by the GPS device
> >> >when it is not busy. This means that there is no fixed relationship
> >> >between the top of the second and the NMEA sentence. And there will be
> >> >significant jitter.
> >>
> >> Ie, NMEA is good for getting the second, not for getting any better
> >> accuracy (well maybe 1/10 sec) If you want accurate time get a gps with PPS
> >> output.
> >> Otherwise there is no advantage of NMEA over a network ntp connection.
>
> >Well, except for the "no wires" part...
>
> Then buy a gps with ppm. The GPS18LVC is only about $60. And you get
> microsecond accuracy rather than 1/10 sec.
>
>
>
> >Isaac
>
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