<P> The derived unit of speed is the knot, defined as one nautical mile per hour . The geographical mile is the length of one minute of longitude along the Equator, about 1,855 m on the WGS 84 ellipsoid . </P> <P> There is no internationally agreed symbol . </P> <Ul> <Li> M is used as the abbreviation for the nautical mile by the International Hydrographic Organization and by the International Bureau of Weights and Measures . </Li> <Li> NM is used by the International Civil Aviation Organization . </Li> <Li> nm (the SI symbol for the nanometre) is used by the U.S. National Oceanic and Atmospheric Administration . </Li> <Li> nmi is used by the Institute of Electrical and Electronics Engineers and the United States Government Publishing Office . </Li> </Ul> <Li> M is used as the abbreviation for the nautical mile by the International Hydrographic Organization and by the International Bureau of Weights and Measures . </Li>

Why is a nautical mile longer than a statute mile