LAPA_SAAB340 From Spain, joined Aug 2001, 389 posts, RR: 5 Reply 7, posted (12 years 2 months 2 weeks 2 days 22 hours ago) and read 714 times:
Notar, if you want to roughly convert knots to mph and don't feel like using a calculator, you can do this:
Say your speed in knots is 160. Divide by ten (and get 16) and add it to your original to get 176mph. This gives you a rough estimate.
If you want a more exact answer, you do a little more math, just divide that 16 by 2, and add it as well.
So you have 160+16+8=184mph
The same applies if you want to convert mph to knots, except instead of adding to your mph speed, you subtract.
Timz From United States of America, joined Sep 1999, 6642 posts, RR: 7 Reply 10, posted (12 years 2 months 2 weeks 2 days 19 hours ago) and read 694 times:
The reason there have been various nautical miles in the past is the fact that the earth isn't spherical. WGS84 assumes the radius of the equator is 6378137 meters exactly, which makes a minute of longitude at the equator about 1855.325 meters. But a minute of latitude is 1842.905 meters at the equator and 1861.566 at the poles-- so presumably the now-official 1852-meter nautical mile is just a semi-arbitrary semi-average.