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    Over-reliance on GPS
    From: Bruce Hamilton
    Date: 2008 Nov 03, 23:35 -0800

    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
    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
    Navigation List archive: www.fer3.com/arc
    To post, email NavList@fer3.com
    To , email NavList-@fer3.com

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