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Nautical Vs. Statute Miles

Fri Jul 14, 2000 3:25 am

For the benefit of me and others who are new to aviation, could someone please give a brief explanation of the difference between nautical and statute miles. Also what is the "great circle," and how does it apply to nautical vs. statute?

I've searched the archives and couldn't find a satisfactory answer to this. If it's there, I apologize. Many thanks for the education.
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RE: Nautical Vs. Statute Miles

Fri Jul 14, 2000 4:04 am

Great Circle:

It's the shortest route between two points on the globe. It doesn't follow lines of latitute but rather it arches. Example: If you were to fly from Seattle to Bismark, ND you would probably skim over the US-Canadian border a little.

Nautical Miles-

One Nautical Mile = 1.15077945 regular miles.
Don't kow the history. Sorry.
Purdue Arrow
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RE: Nautical Vs. Statute Miles

Fri Jul 14, 2000 4:30 am

As you probably know, latitude and longitude can be given in degrees, minutes, and seconds, with a minute being 1/60 of a degree, and a second being 1/60 of a minute. The origin of the nautical mile is that one minute of longitude is equal to one nautical mile. While a statute mile is 5,280 feet, a nautical mile is approximately 6,000 feet.
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RE: Nautical Vs. Statute Miles

Fri Jul 14, 2000 11:45 am

Since the earth isn't actually spherical, a degree (or minute) of latitude at the pole is 1% longer than a degree (or minute) of latitude at the equator. So in the past there have been several "nautical mile"s, ranging from around 6076 to 6082 (?) feet. But now it's officially defined as 1852 meters exactly, or 6076.1 ft.

If we pretend the earth is spherical, then the shortest path between two points (measured along the surface of the earth) is the one that has the least curvature-- in other words, the one that follows a arc that has the largest possible radius. The largest possible radius is the radius of the earth itself; so the shortest path is along a circle whose center is at the center of the earth. That's what a great circle is.