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    Re: sextant without paper charts
    From: Lu Abel
    Date: 2008 Oct 31, 20:57 -0700

    First of all, any skipper or navigator who doesn't look out the window
    frequently is stupid, just plain stupid (see my previous post about the
    59' sportfisherman that rammed a sailboat, killing the skipper, in
    totally clear weather because the sportfisherman's skipper was "entering
    waypoints in his GPS") (since since this started with submarines, let's
    agree to exempt them ).
    At the same time, I find this Hampton Roads USCG posting a bit more on
    the "beware of the bogeyman" side than on rational navigation.    Let's
    say their their hypothetical ship is traveling at 15 kts (certainly
    pretty fast for conditions of reduced visibility).  That's a nautical
    mile every four minutes or 1500 feet every minute -- or 150 ft every six
    seconds.    I'd sure like to hear of an electronic charting system that
    would take more than six seconds to update a track line!   So at worse,
    the track line might be off by 150 feet.   On the other hand, they
    advise taking fixes "every three minutes"   That means fixing the
    vessel's position every 3/4 of a mile (not counting the uncertainty
    introduced by the time it takes to actually plot radar or visual
    bearings).   If I were navigating a ship, I'd sure rather know my
    position to 150' of accuracy than to 3/4 mile.
    IMHO, it's OVER reliance on electronic navigation that is the danger,
    not using it intelligently while keeping an eye out the window, that
    causes problems.
    Yours for truth and rationality,
    hch wrote:
    > It may be of interest to some to note the following excerpt from "USCG 
    Safety Alert HMRMS04-7", regarding Navigation in restricted visibility, as 
    issued by Sector Hampton Roads on December 13, 2007, particularly the 
    apparent time delay for a track line to upedate on an electronic chart.
    > It seems that such a time delay could have rather far reaching implications.
    > Excerpt ...
    > "TAKE FREQUENT POSITION FIXES. Too often mariners fail to appreciate the 
    importance of frequent fixes while navigating in restricted visibility. Over 
    reliance on radar and electronic navigation systems can cause a mariner to 
    lose situational awareness, in part because of time delays while the image is 
    refreshed. A vessel can travel several hundred yards, especially if the 
    operator fails to reduce speed, in the time it takes for the track line to 
    update on an electronic chart. In some cases it may be necessary to take 
    fixes as often as every three minutes."
    > Regards,
    > Henry
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