NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Mercator vs. Great Circle Charts
From: Carolyn Seefer
Date: 2001 Aug 28, 8:16 PM
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