Knots and Nautical Miles
A nautical mile (n mile) is the distance on the Earths surface that subtends an angle of 1 minute (where 1 minute = 1/60 degree) along any merician measured from the centre of the Earth (a meridian is any circle drarn on the surface of the Earth that passes through both poles).
The average radius if the Earth is 6,370,000 m and in a circle there are 360 degrees, so with 60 minutes in a degree, there are 360*60=21600 minutes in a circlke.
The length of a meridian, assuming the Earth is a sphere of radius 6,370,000 m is
In fact the nautical mile is defioned as 1852 m along any great circle drawn on the Earth's suface.
A knot is a speed of 1 nautical mile per hour.
A mile is 1609 m and a kilometre or km is 1000 m so a nautical mile isor