Question: why are knots and mph difference?
Answer: It is slightly more than a statute (land measured) mile (1 nautical mile = 1.1508 statute miles ). Nautical miles are used for charting and navigating. A knot is one nautical mile per hour (1 knot = 1.15 miles per hour ). ... The speed of the ship was said to be the number of knots counted (Bowditch, 1984).