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    Re: DR navigation in the recreatiional fleet: was Role of CN at sea
    From: Dave Weilacher
    Date: 2004 Oct 13, 07:11 -0500

    You might teach it the way they used to teach drinking and driving to high school kids.
    Line up a bunch of anecdotes that show the perils of relying solely on GPS
    The Sable Island incident where a skipper leaving the USA for Portugal, put in 
    a start point and an end point, then let the Autopilot steer the route.  A 
    mercator chart shows nothing but deep blue Atlantic.  They ran aground at 
    Sable Island and the boat was lost.
    In a regatta from Florida to Bermuda, the schooner I was on had both the 
    Magellan and the Raymarine onboard GPS drop out a day shy of Bermuda.  (My 
    old Garmin 45 handheld, saw us the rest of the way)  Even at that, we were 
    religious about keeping a waypoint log to the 1/2 hour so we could construct 
    a DR if necessary.
    In the 51st annual Mug race on the St Johns river this year, a womens team was 
    relying solely on GPS and visual reference when they became ensconsed in a 
    severe squall.  They immediately lost visual and GPS.  Because they weren't 
    keeping up with their DR, they became disoriented and ran hard aground.
    On a charter in the Florida keys, we anchored on the lee side of Marquesas Key 
    for the night.  The weather was predicted to kick up and swing around on us.  
    To prepare for this, I set up a safe route to the other side of the island on 
    the GPS.  The weather did as predicted but the GPS failed.  (They are prone 
    to this in bad weather)
    It takes no imagination at all to know what happens if you get one digit wrong 
    setting up a route then relying on it exclusively.
    So, like the good insurance agent who convinces you that death is eminant and 
    he has the cure, convince them that bad things will happen, if they want to 
    remain clueless about navigation beyond GPS.
    At the very least, you should be able to get them to believe in system 
    redundancy, think about what to do if it fails, and pay a lot of attention to 
    the numbers they put in.
    -----Original Message-----
    From: Jim Thompson 
    Sent: Oct 13, 2004 6:33 AM
    Subject: Re: DR navigation in the recreatiional fleet: was Role of CN at              sea
    I know we discussed this some last year, but the issue remains unclear in my
    mind.  How should GPS navigation be taught to recreational boaters who have
    minimal or no traditional navigation training?
    I've thought about this issue a lot, partly because I was well grounded in
    traditional coastal DR piloting, and partly because I am now involved in the
    Canadian Power & Sail Squadrons' teaching programs.  We are struggling to
    figure out how to deliver safe GPS training to recreational boaters who
    don't want to spend a lot of time learning navigation.  All my navigation
    now is within sight of land, except for short times when mist, rain or fog
    reduce visibility.
    Boaters with minimal navigation training can go to Canadian Tire, buy a GPS
    (handheld or chartplotter), and had out into the water.  And they do, by the
    thousands in North America.  Those folks for the most part are not
    interested in learning the intricacies of running fixes, leeway, and DR/EP
    plotting, and it is darned hard to convince them why they should (even
    though I believe they should).  I taught a one-day GPS course a couple of
    years ago where I referred to such topics.  The evaluations largely
    suggested that I drop those comments from the course.  But can marine GPS
    navigation be properly taught to beginners who know nothing about LOP's,
    fixes, courses and tracks?
    GPS has changed the way recreational boaters navigate, particularly as we
    become more comfortable with its startling accuracy and reliability.  My
    personal experience is that I use a GPS chartplotter exclusively, but
    mentally I continually maintain a kind of DR plot in my minds' eye, using
    data from my eyes, compass and sounder to verify the GPS postion and to help
    me decide on course changes.  I also use radar, even in good weather.  There
    is nowhere on the boat for me to lay out a chart and draw all the lines and
    symbols that I learned in traditional piloting, but I keep a current chart
    in a large plastic envelope on the bridge and refer to it often as we
    proceed.  If I know from tide tables and the chart that the tide is running
    right to left, then I adjust my course to compensate accordingly.  Same with
    the wind (leeway).  The "tail" on the GPS chartplotter tells me how much
    leeway and current I am experiencing, and shows me whether my compensation
    is effective.  But I am doing all that in my mind's eye after years of
    training in traditional coastal piloting.  But I wonder -- is that how the
    lesser trained boaters are navigating with GPS?  I listened to a long
    exchange on marine radio this summer that makes me think not.
    I still think that boaters should learn EN by first learning traditioanl
    piloting.  They might never use parallel rules again after completing the
    course, but they will certainly know better how to use GPS.
    By the way, I have never experienced GPS drop-out on the Canadian Atlantic
    coast in the past 5 years, unlike the experience of the Lakes boaters.
    Jim Thompson
    Outgoing mail scanned by Norton Antivirus
    > -----Original Message-----
    > From: Navigation Mailing List on Behalf Of Federico Rossi
    > The point is that GPS navigators (I'm talking about boats and not
    > cruisers) sometimes seem they have forgotten DR principles, they regard
    > the practice of estimating and checking their position with the well
    > known methods of coastal navigation (and why not, of celestial
    > navigation) as a waste of time, thus losing the opportunity to interpret
    > the effect of the currents, of the wind, the behaviour of the boat, and
    > to forecast the corrections needed to follow a certain route (and
    > eventually to cross check their electronic instrumentation).
    Dave Weilacher
    .IBM AS400 RPG contract programmer

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