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    Re: Wind & Current Navigation
    From: George Istok
    Date: 2003 Apr 22, 14:48 -0500

    I have always thought that navigation and piloting were separate concepts.
    I navigate from A to B, planning a course and making checks and calculations
    to insure I am near that course.  I pilot (sounds odd) my sailboat in the
    harbor, selecting a course and observing my environment to make sure I am
    near that course.  The two sound similar, but the differences are important.
    For instance, in crossing an area with a known current I need to make
    corrections for the set and drift of that current.  In navigation, I would
    use a vector diagram and determine a course to steer.  I would, however, use
    my piloting skills to observe the effects of a current and correct my course
    accordingly.  I suppose that, given enough time, I could also use vector
    diagrams in a harbor to determine a course to steer.  However, when piloting
    is involved, I want to see what is going on in the real world rather than
    estimate what is happening to my position by lines on a paper chart.
    
    There is a large overlap of navigation and piloting.  In thick fog, in the
    harbor, I would be very happy to back track a GPS plot or, even better,
    follow a preplanned track created on a clear day.  I could divide my
    attention between the cross track error on the GPS and trying to see through
    the fog.  On open water, looking around to see what is close will help keep
    you from navigating your way through solid object.  I think there must be
    different "rules" for different vessels.  Me, myself, and I on a sailboat
    operate differently than the nav section on a carrier.  With several bearing
    takes, observers, and plotters a line can be drawn on the chart that could
    help a bit in keeping the keel off the bottom.
    
    I think the principle and theory Dan is looking for only comes from practice
    and is not open to calculation.  The equations, if there can be any, are
    more than complex.  Even the number of variables would seem to be infinite.
    Is there a phenomena in mathematics where complexity so great that the
    "answers" are not predictable?  I can predict that your boat and mine will
    not react the same to wind and current. In fact, the same wind and current
    can not be felt by both boats.  However, we both can recognize the effect of
    wind and current and drive safely into the slip.  That may be the only
    "theory" that exists.
    
    George Istok
    
    
    
    -----Original Message-----
    From: Navigation Mailing List [mailto:NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM]
    On Behalf Of Dan Allen
    Sent: Tuesday, April 22, 2003 10:56 AM
    To: NAVIGATION-L{at}LISTSERV.WEBKAHUNA.COM
    Subject: Re: Wind & Current Navigation
    
    On Monday, April 21, 2003, at 02:36 PM, Charles Tait wrote:
    
    > I severely doubt that any equation will fix this better than judgement.
    
    I know that the equations that govern marina navigation are very
    complex with currents and winds added, and that there may be no current
    good real-time calculation mechanism to make use of them.
    
    But I am looking for us to develop a more rigorous theory of what is
    happening so that we can learn from it and make some progress on
    understanding the physics of winds and currents so we can have some
    first principles to work from while at the helm.  I am therefore
    looking for the theory that will help practice.
    
    Dan
    
    
    

       
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