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    Re: Over-reliance on GPS
    From: Lu Abel
    Date: 2008 Nov 04, 08:37 -0800

    I couldn't agree with you  more.
    What you say is a very reasonable way of putting it.  It's not the
    existence of GPS, but rather it's not having a backup and not having
    situational awareness, that is the problem.  At the same time your
    "chartplotter plus a couple of backup handhelds in waterproof bags" is
    exactly what I've mentioned on the list before.
    What gets me though, is the folks who say "beware of GPS" or even
    "beware of all electronics" without being specific about what their
    concerns are.
    bruce hamilton wrote:
    > I would say that the biggest problem with GPS it that it is a single
    > system that is so reliable that it is easy to forget it will not always
    > be there.
    > In pre-GPS coastal navigation from my era we had Loran-C, radar, RDF,
    > pelorus, gyro-compass, sextant, and the depth sounder. Radar was the
    > most popular as it gave you an instant range/bearing fix as long as some
    > prominent bit of land was in range. Loran-c was great when it worked,
    > but we spent a lot of time getting information from half the chain.  The
    > sounder was really handy when you crossed an obvious sounding line. I
    > used the sextant for distance off calculations. The RDF was occasionally
    > used, but no single piece of equipment was ever the single source of
    > data.
    > GPS does have it's faults, other than total failure. As in lightning
    > strikes. It is not reliable in the high north. It is also subject to
    > political failure. A fellow Captain in my 60 Ton course was at sea at
    > the time of the 911 attacks and said that GPS was all over the place for
    > several hours during that time. Civilian GPS is easily jammed with very
    > little power and unsophisticated equipment.  A malfunctioning home TV
    > antenna booster shut down GPS in a harbour in the US. The leaky signal
    > took a long time to trace as the transmissions apparently bounce off
    > everything. That little bit of stray EM radiation made the GPS
    > unreliable for a five mile radius. If I can find the article again I
    > will post it here.
    > I will happily admit that I would never take a serious voyage without a
    > good chart plotter, and two spare GPS units tucked in ziplocks with
    > spare batteries. Besides, they work in the fog! Roz Savage used her Tom
    > Tom when her plotter packed it in on her rowing voyage from San
    > Francisco to Hawaii.
    > "Jamming in Moss Landing Harbor, CA
    > 15 Apr 01 - 22 May 01, VHF/UHF television antenna with pre-amplifier
    > caused GPS failures to all of Moss Landing Harbor
    > Boat owner purchased TV antenna, which was equipped with pre-amp
    >  From interior location Amp's emitter jammed all of Moss Harbor and
    > 1km out to sea
    > No GPS in entire area = 37 days
    > Impact to Moss Harbor
    > Research vessels relied heavily on timing from GPS
    > Extreme difficulty going through harbor in foggy conditions
    > Notification to all vessels in area that GPS was down
    > Keep a good watch
    > Bruce Hamilton
    > >
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