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    Re: Mercator vs. Great Circle Charts
    From: Dan Hogan
    Date: 2001 Aug 29, 7:22 AM

    On 28 Aug 2001, at 22:15, Carolyn Seefer wrote:
    [Snip personal info]
    
    NOTE:
    
    These are REALLY basic questions. The answers are available in any navigation
    text.
    
    >
    > 1. Can true direction be determined in the same manner for all locations on a
    > Mercator chart? How about on a great circle chart?
    
    Mercator -- Yes
    Great Circle Yes the Great Circle True Course.
    
    > 2. How is the compass rose used on each of these charts?
    
    To refer to the True Direction using plotting tools.
    
    > 3. If I were to draw a straight line between two points (say Tokyo and Cabo
    > San Lucas) on both a Mercator chart and a great circle chart, would either
    > straight line represent a great circle?
    
    Only on the Great Circle chart.
    
    > 4. Given the straight line drawn between Tokyo and Cabo San Lucas (see
    > above), which chart, the Mercator or the great circle, would give me the
    > shortest route between these two points?
    
    The Great Circle.
    
    > 5. Would sailing a great circle course always be the best way to travel
    > across the ocean, or would ships have to take into consideration unfavorable
    > winds, currents, or storms that might cause a delay?
    
    Depends on the destination and obstacles on the course. Ships use weather
    routing, small boats use best wind/current and avoiding weather.
    
    > 6. Do most large ships today use computer assistance to help them choose the
    > best course across the ocean?
    
    Yes.
    
    > I realize that these questions are very basic, but I am hoping you will share
    > your expertise with a beginner. Thanks so much!
    
    Try reading Pub. No. 9, Bowditch; Dutton's Navigation and Piloting or any
    navigation manual.
    
    
    Dan Hogan WA6PBY
    C27 "Gacha"
    dhhogan{at}verimail.com
    Nav-L Page: http://www.wa6pby.com
    

       
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