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 =
Nautical almanac Nautical Almanac Office, ever since the first edition was published in 1767. In the United States, a nautical almanac has been published annually by the US Naval Observatory since 1852. It was originally titled "American Ephemeris and Nautical Almanac". Since 1958, the USNO and HMNAO have jointly published a unified nautical almanac, "The Astronomical Almanac" for use by the navies of both countries. Almanac data is now available online from the US Naval Observatory. Also commercial almanacs were produced that combined other information. A good example would be Brown's — which commenced in 1877 – and is still produced annually,