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    Mercator vs. Great Circle Charts
    From: Carolyn Seefer
    Date: 2001 Aug 28, 8:16 PM

    Hello, everyone!
    I just joined the Navigation mailing list. This semester I am taking an
    oceanography class, and this list looked interesting and informative. I am a
    novice in this area (but eager to learn!), so I am hoping to learn a lot on
    this list from the experts.
    We are currently studying Mercator and great circle charts, and I've already
    run into a few questions I am hoping you can help me with:
    1. Can true direction be determined in the same manner for all locations on a
    Mercator chart? How about on a great circle chart?
    2. How is the compass rose used on each of these charts?
    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?
    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?
    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?
    6. Do most large ships today use computer assistance to help them choose the
    best course across the ocean?
    I realize that these questions are very basic, but I am hoping you will share
    your expertise with a beginner. Thanks so much!
    Carolyn Seefer
    Diablo Valley College
    Pleasant Hill, California

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