MD11Nut From , joined Dec 1969, posts, RR:
Reply 6, posted (14 years 3 weeks 4 days 21 hours ago) and read 966 times:
Mandargb asked:"Please correct me if I am wrong
My understanding is 1nm = 1minute of latitude at equator. "
Mandargb, you are not wrong in stating that. But if you are implying that it's only true at the equator, then that's not entirely true. 1nm is equal to 1 minute of latitude everywhere on earth since latitude lines are all parallel to each other. For longitudes 1minute = 1 nm multiplied with the cosine of latitude since longitudinal lines gets closer (smaller) and meet at the two poles. In this case, 1 min = 1 nautical mile for longitude only at the equator. Anywhere else it is less by cosine of the latitude.
Sabenapilot From Belgium, joined Feb 2000, 2734 posts, RR: 46
Reply 7, posted (14 years 3 weeks 4 days 19 hours ago) and read 961 times:
The fully correct defenition of the NM as introduced by the Royal Navy well before Columbus had set sail for America is: The length of one minute measured along a MERIDIAN.
Since we can consider the world to be almost a sphere, you may also say EQUATOR, although this is not 100% correct!
In fact, because our earth is not a perfect sphere but is somewhat flatted at the poles due to earth rotation, if you use the EQUATOR in your defenition your NM will be slightly longer: 1.4% to be precise!
Timz From United States of America, joined Sep 1999, 6966 posts, RR: 6
Reply 8, posted (14 years 3 weeks 4 days 15 hours ago) and read 953 times:
Actually a minute of latitude is about 1% shorter at the equator than it is at the poles.
Since the earth isn't spherical there have been various nautical miles in the past, but the official definition is now 1852 meters. A statute mile is exactly 1609.344 meters, so that makes the conversion factor about 1.150779.