Globetrotter From United States of America, joined Feb 2000, 174 posts, RR: 0 Posted (15 years 9 months 3 weeks 5 days 9 hours ago) and read 16460 times:
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.
Mls515 From United States of America, joined Jun 2000, 3081 posts, RR: 8
Reply 1, posted (15 years 9 months 3 weeks 5 days 9 hours ago) and read 16402 times:
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.
Purdue Arrow From United States of America, joined May 1999, 1574 posts, RR: 7
Reply 2, posted (15 years 9 months 3 weeks 5 days 8 hours ago) and read 16390 times:
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.
Timz From United States of America, joined Sep 1999, 7211 posts, RR: 7
Reply 3, posted (15 years 9 months 3 weeks 5 days 1 hour ago) and read 16364 times:
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.