nautical system
From Glossary of Meteorology
A system for expressing distance, speed, and acceleration in which 1) the distance of one minute of arc along a meridian or great circle is one nautical mile; 2) a nautical mile per hour is a knot; 3) a nautical mile per hour per hour is the acceleration in knots per hour.
Although the nautical system originated with marine operations, it has been adopted to report winds and aircraft speeds.
