Urban
1 knot is not the same as 1MPH.
A nautical mile is a distance on the earth's surface of 6,080 feet, which is equal to one minute of latitude at the earth's equator. Since there are 360 degrees around the earth, and each degree equals 60 minutes, the distance around the earth, at the equator or any other great circle, is 21,600 nautical miles. Knots are 1 nautical mile per hour.
In case you were wondering, this is the mathematical equation of a nautical mile to a regular mile.
1 nautical mile = 6378km * [1 inch/(2.54*10^-5km)] * 1 foot * 1 mile * 1 inch * [(pi*radians)/180deg]*(1deg/60ft) = 1.15miles
Probably more than you wanted to know, but, whatever.