Knot is the speed unit of ships, including warships, and the sign of knot is the prefix of the English word "Kn", which is represented by "Kn". 1 knot is equal to 1 nautical mile per hour, that is to say, driving1.852km per hour. The code name of "knot" is English, which refers to the length of latitude 1 minute on the meridian of the earth. Because the earth is slightly ellipsoid, the radian of 1 min at different latitudes is slightly different.