It's just a convenient way to define a unit of length. Look up the original definition of the metre and you'll see that it's basically the same except for some constants.
The metre was originally defined as 1/10,000 of the distance from the equator to the north pole through Paris. There's a corresponding measure of angle (gradian -- 1/400 of a circle) which has never become widely adopted (although my old casio calculator supported it)
Tloewald|12 years ago