3 ms·One nautical mile is very nearly the length of one minute of arc at the earth's surface.by gshubert17 14y agoOne nautical mile is very nearly the length of one minute of arc at the earth's surface.geon 14y agoWouldn't that make the arc-minute the practical unit?kbutler 14y ago> Wouldn't that make the arc-minute the practical unit? Yes. However, the earth is not a perfect sphere. The nautical mile is an average arc-minute.cygx 14y agoAnd the kilometer is an average centigrad.ISL 14y agoThanks for triggering a rarely used synapse. http://en.wikipedia.org/wiki/Grad_(angle) http://en.wikipedia.org/wiki/Grad_(angle)siscia 14y agoFor what I know the nautical mile change due to your position in the Earth...