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  • - Truman Prevatt

    RE: [RC] GPS - Bob Morris

    To see just how inaccurate your GPS is, and it is inaccurate, down load the route from the GPS and overlay it on a Orthophoto.  I have done this numerous times and found that the normal handheld GPS can be off the trail by 100 meters. They are not accurate.
    With the newest ones there is a built in correction system but it is only available when you can see down to 10 degrees above horizon. Wonderful for coastal navigation for which it was designed but worthless in our mountains.
    Now if you want to spend 6 - 8 grand for a survey grade unit you might get a bit better track after corrections are done but the hand held, while it will get you in the area you want to go to, will get you no closer than seeing distance as an average.

    Bob Morris
    Morris Endurance Enterprises
    Boise, ID

    -----Original Message-----
    From: ridecamp-owner@xxxxxxxxxxxxxxxxx [mailto:ridecamp-owner@xxxxxxxxxxxxxxxxx]On Behalf Of Truman Prevatt
    Sent: Tuesday, July 09, 2002 2:35 PM
    To: amber applegate
    Cc: ridecamp@xxxxxxxxxxxxx
    Subject: Re: [RC] GPS

    I hit the send button too soon. There are 24 operational birds on orbit.  You can see about 1/3 of the sky from the mid latitudes on the earth. Any birds on the horizon are of no use. In the mid latitudes if you can see down to 10 degrees elevation above the horizon you will be able to see 6 birds. If you can see down to 15 degrees you can see 4 birds. In order to be certain to see 4 birds you need clear visibility down to 15 degrees in all directions. In the mountains this can be difficult. Your reciever will function with three birds, but it fixes the location at mean sea level. If you can not see at least three it will go to sleep.


    amber applegate wrote:
    I have to differ with that statement, Truman. I ride in nothing but
    mountains, forest, valleys and my garmin gps works great. Why would they
    make them if they couldn't be used in all types of terrain? I carry it
    zipped up in my saddlepack even, it has always recorded everything. Only
    problem I have with it is the batteries use up way too fast. I can only get
    about 7 hours on a set of batteries, even using the battery saving mode.

    So I missed the beginning of this thread, is it not allowed to be used in
    AERC? and if so, why?

    Unless you are riding in pretty flat, open terrain - no follage cover,
    no valleys, no hills, etc.- the GPS won't do much of a job with what you
    want since your satellite coverage will be limited. On a ride last year
    I turned my on doing a 24 mile loop just for grins. This loop was pretty
    open - no trees - but there was enough blockage from hills and valleys
    that the 24 miles ended up showing up as 11 on the unit.

    Great tool for what it was designed to do but it does take some
    judgement in reading the results.


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    Re: [RC] GPS, Truman Prevatt