alt Hacker NewsIf you do positioning in degrees, minutes, and seconds (or decimal minutes which I guess is more common nowadays), a 'natural' length unit for navigation is a minute of longitude, which is the original definition of the nautical mile. And then we get velocity as nautical miles per hour, or knots.
Blame the French for reinventing the wheel instead of, say, using a 1/1000th of a nautical mile as the definition of the metre. Alas, that's all water under the bridge by now.
If you want to do navigation in SI units, the UTM projections (see sibling thread) typically do positioning in metres inside each grid square.
Funnily enough the metre is defined by the globe as well: the arc from the equator to North pole is defined as 10,000 km. I think this might be where the alternative angle metrics came from, which went with the metre:
full circle is 400 grad, so a right angle (10,000 km) is 100 grad.
Then minutes and seconds are factors of 100, so a centesimal minute is 1 km and 1 centesimal second is 10 m.