What are statute miles?

Question

I keep hearing a reference to this on NASA TV.

Answer 1

the statute mile of 1,760 yards (about 1,609 metres), or
the international nautical mile (exactly 1,852 metres).

Answer 2

A statute mile is 5,280 feet. It is the regular mile marked on all the US road maps and the mile in Miles per Hour for all the speed limits. For some reason, NASA likes to use the nautical mile, as in, "The vehicle is now 10 nautical miles in altitude and 30 nautical miles down range". A nautical mile is 6,076 feet. Since most people aren't familiar with nautical miles, NASA sometimes goes out of its way to report the numbers in the statute miles we are all used to using in the hope of being less confusing.

Answer 3

Just to muddy the waters a bit more, nautical miles were originally defined as the distance of 1 minute of arc in latitude or 1/60th of a degree of arc along a "Great Circle" on the earth's surface. This made it easier for ships navigators to figure time and distance. NASA likes to work in nautical miles as well since most orbital trajectory work is in spherical trigonometry and gives results in angle measurements just as in ocean navigation, so using something that is an even multiple or division into a degree measurement makes perfect sense to them. Statute miles (the normal "land based" miles), like feet, inches and yards, are "flat earth" based measurement systems that are related to the size of parts on people and which require lots of extra conversion work to use in computing positions on spheres or in circular orbits.