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    Re: News Item on Over-reliance on GPS
    From: Frank Reed
    Date: 2008 Nov 08, 19:27 -0500

    Fred H., you wrote:
    "It's very nice to have one's faith in the utility of sextants on small
    boats restored now and again.  I wonder whether Frank were trolling for such
    a response!"
    Not a bit, Fred. My point is merely that the best backup for a complicated
    GPS "system" aboard a boat, with all its complexities and risk of electrical
    failure, is a simple well-protected handheld GPS. We all enjoy celestial
    navigation here, no doubt about it. But its value for backup navigation is
    quite limited -- it takes specific education, skill, practice; it only works
    when the weather cooperates; its accuracy is much less than GPS; it requires
    special tables and a delicate instrument; it requires a functioning watch,
    typically electronic, for a complete fix; etc.
    I've been trying to think of people who use handheld GPS units in stressful
    marine conditions. It occurred to me that sea kayakers often use GPS units
    and they get dunked quite regularly. I also learned about a neat little gps
    sport called 'speedsurfing'. These folks are wind surfers who collect speed
    records using GPS units, usually attached to their wrists or ankles. A very
    wet environment. I doubt they would survive a lightning strike (!), but such
    applications may serve to remind people that many of these devices are now
    designed to be quite robust.
    So what would make a good backup nav system aboard a small boat? I suggest a
    waterproof handheld GPS unit, capable of floating, as many are, with a dozen
    spare batteries (I would think a unit that takes standard AA batts would be
    preferable here) kept in a waterproof pouch and all that stored in a sturdy
    metal box to protect against lightning strikes and lightning-induced EMP.
    Throw in a small-scale paper chart if you like. Also, there should be very
    simple printed instructions on a laminated card so that a layperson can use
    it in an emergency and know how to operate the unit and not use up the
    batteries too quickly.
    So where's the sextant then? Well, gee, that's your PRIMARY navigation
    system. Use that every day and impress your friends. And of course, in the
    highly unlikely event of the disabling of the GPS constellation of
    satellites, then you'll have celestial as a backup for the backup.
    Navigation List archive: www.fer3.com/arc
    To post, email NavList@fer3.com
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