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Subject: Mercator vs. Great Circle Charts
From: Carolyn Seefer (CCSeefer@XXX.XXX)
Date: Tue Aug 28 2001 - 22:15:41 EDT
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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