Originally Posted by Sailor Steve

WELCOME ABOARD, kramxel!

I'm American, but I'm one of the many who thinks just like you...well, just the opposite, in one sense. I still think in yards, feet and miles, but when I play SH3 I always use metric.

One thing that will make it simple to understand is that when the International Ordinary Hydrographic society standardized the nautical mile in 1929, they made it metric. A nautical mile is exactly 1852 metres. The United States didn't adopt it until 1954, since this comes to an odd number, as Raptor1 pointed out.

Yes, it is confusing, but can be simple to execute. A yard is 0.9144 metres, which makes a metre 1.0936 yards. As you can see, the two are close enough that for measuring fairly short ranges you can do it in your head. For longer ranges it falls apart. The nautical mile is used for long-distance measurement, and the knot for speed, because a nautical mile is one minute of arc (1/60 degree), or 1/21600 of the distance around the earth.

These should help explain it further:
http://en.wikipedia.org/wiki/Nautical_mile
http://en.wikipedia.org/wiki/Minute_of_arc