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    Re: mid-longitude sailing
    From: Bill B
    Date: 2007 Jan 10, 16:44 -0500

    Bill wrote
    
    > I did play with departure
    > and destination latitudes approaching zero and those seem to be a wee bit
    > off at first blush.
    
    My error.  "...latitudes approaching zero..."  should read "longitudes
    approaching zero."
    
    Lu wrote:
    
    > 2.  Any great circle course, when plotted on a Mercator chart, looks a
    > curve swinging towards the nearest pole and then back down again.  The
    > rate of change of a course is greatest in the higher latitudes.  If I
    > were trying to translate a great circle course into steering directions,
    > I'd want to calculate course direction more frequently near this
    > northward (or southward) peak than at lower latitudes.
    
    In George's defense, he did note that the one could subdivide a long
    passage.  He stated, "Having the coordinates of that middle-point, you can
    then easily split each half further, and so on, using the same method, until
    your point-to point legs are short enough to treat each one as a
    rhumb-line."
    
    Given a programmable calculator or computer, or more time the other
    formula's are fine.  With nothing more than the simple formula George
    presented and a $10 pocket calculator one can do the job on the fly.
    
    Bill
    
    
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