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Subject: Re: Mercator vs. Great Circle Charts
From: Dan Hogan (dhhogan@XXX.XXX)
Date: Wed Aug 29 2001 - 09:21:45 EDT
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@XXX.XXX
Nav-L Page: http://www.wa6pby.com
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