Equator is commonly modeled as a sphere flattened 0.336% along its axis. This makes the Equator 0.16% longer than a meridian (a great circle passing through the two poles). The IUGG standard meridian is, to the nearest millimetre, , one arc-minute of which is , explaining the SI standardization of the nautical mile as , more than less than the geographical mile. The sea-level surface of the Earth (the geoid) is irregular, so the actual length of the Equator is not so easy to determine. "Aviation Week and Space Technology" on 9 October 1961 reported that measurements using the Transit IV-A
Adlard Coles Nautical Adlard Coles Nautical Adlard Coles Nautical is a nautical publisher, with over 300 books in print. The company publishes books on topics of interest to sailors and motorboaters and also ‘landlubbers’ with an interest in the sea. Their list includes almanacs, cruising guides, pilot books and how-to instruction books, as well as large format photographic books, sailing narratives and sea-related reference, maritime history, humour and trivia books. Adlard Coles Nautical has been part of Bloomsbury Publishing since 2003. The company was founded by yachtsman Kaines Adlard Coles in 1947. He wrote many of the books, including pilots, sailing narratives and