Nautical mile 1 sea mile", followed by "For most practical purposes distance is measured from the latitude scale, assuming that one minute of latitude equals one nautical mile". One tenth of a nautical mile is a cable length. The derived unit of speed is the knot, defined as one nautical mile per hour. The metre was originally defined as of the meridian arc from the North pole to the equator passing through Dunkirk. The Earth’s circumference is therefore approximately 40,000 km. The equatorial circumference is slightly longer than the polar circumference – the measurement based on this (40,075.017 km x x =
American Ephemeris and Nautical Almanac American Ephemeris and Nautical Almanac" and "The Astronomical Ephemeris", a new name for the old British title "The Nautical Almanac and Astronomical Ephemeris". Beginning in 1981, the title "The American Ephemeris and Nautical Almanac" and the British title "The Astronomical Ephemeris" were completely merged under the single title "The Astronomical Almanac". American Ephemeris and Nautical Almanac The American Ephemeris and Nautical Almanac was published for the years 1855 to 1980, containing information necessary for astronomers, surveyors, and navigators. It was based on the original British publication, "The Nautical Almanac and Astronomical Ephemeris", with which it merged to form "The Astronomical