[time-nuts] GPS question

Chris Kuethe chris.kuethe at gmail.com
Thu Apr 5 17:32:25 UTC 2007


On 4/5/07, Joseph Gray <jgray at zianet.com> wrote:
> Am I correct in assuming that the position given by a WAAS enabled handheld
> GPS unit is more accurate than the position reported by my Z3801?
> Specifically, I tried a Garmin eTrex Legend Cx with WAAS enabled and used
> averaging mode for the waypoint.
>
> On a related question, the eTrex reported that the position was +- 6ft. Is
> that really 6ft, or is that 6ft in addition to the 3M claimed accuracy of
> WAAS?

NAVSTAR is specified to provide some minimum level of precision and
accuracy; if you get better than that, lucky you. If you find that 95%
of navigation solutions are within a 2m sphere when WAAS is being
used, lucky you. But 6ft is quite reasonable with a decent receiver
and good visibility - I have a receiver on top of an office building,
and roughly 50% of my solutions were within 1m, 95% within 2m.

http://www.navcen.uscg.gov/gps/geninfo/2001SPSPerformanceStandardFINAL.pdf
http://gps.faa.gov/Library/Data/waas/2892bC2a.pdf
http://www.usace.army.mil/publications/eng-manuals/em1110-1-1003/toc.htm
-- 
GDB has a 'break' feature; why doesn't it have 'fix' too?




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