Re: pedometers/mileage -gps

[bturner@ida.org (Ben Turner)]

On Tue, 15 Jun 1999 09:32:50 -0700, "s.m.willis" <smw@sos.net> wrote:
>I purchased a GPS unit a couple of years ago thinking it would be a great
>asset to our high mountain trips......not so.  It was inaccurate most of the
>time because of timber or rock interference.  .  .  .
--<snip>--

    Over time GPS units have improved with increased sensitivity, ability
to track more satellites simultaneously, etc.  My first GPS bought in 95 was
great on the water but useless in the woods.  A 1998 Garmin II+ performed much
better, but still failed in dense foliage.  Adding an external antenna (modified
with velcro has fixed the problem for most situations I encounter in eastern
forests.
 
    Improved satellite tracking has not improved the absolute accuracy of GPS
in the presence of dithering.  I still chuckle to see the track showing up on
the wrong side of a creek or crossing the creek a couple more times than I
remember.  For rides of any distance however, the total mileage estimates from
the Garmin track pretty well to marked miles.  They also track well with
estimates derived from a recording GPS unit with differential-GPS postprocessing
that corrects for dithering and some of the other errors (a state-supported,
expensive, heavy, user-unfriendly, but more accurate unit employed in a
trail-mapping project in Maryland).

YMMV--literally ;-)

Best,
Ben Turner
bturner@ida.org


=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Ridecamp is a service of Endurance Net, http://www.endurance.net.    
Information, Policy, Disclaimer: http://www.endurance.net/RideCamp   
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=