[ntp:questions] $GPGGA fix indicator 6 estimated/dead reckoning
"terje.mathisen at tmsw.no" at ntp.org
Wed Feb 4 08:07:18 UTC 2009
Dave Hart wrote:
> ntpd/refclock_nmea.c when using $GPGGA tests for 0 and declares the
> clock not in sync. When I read "estimated" or "dead reckoning" wonder
> if ntpd should consider the clock not of sync when it sees fix
> indicator 6. The gotcha that comes to mind is what if there are too
> few satellites in view for a good position fix but still enough for
> the time to be stable and accurate?
The problem is that this only works on GPSs which can be set into
"Zero-D" mode, i.e. dedicated timing receivers like the Oncore UT+.
Most NMEA-generating GPSs cannot do this, unfortunately.
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"
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