Nautical mile - Video Learning - WizScience.com
A "nautical mile" is a unit of distance that is approximately one minute of arc measured along any meridian. By international agreement it has been set at 1,852 metres exactly .
It is a non-SI unit used especially by navigators at sea and in the air, and also in polar exploration. It is commonly used in international law and treaties, especially regarding the limits of territorial waters. It developed from the "sea mile" and the related geographical mile.
The nautical mile remains in use by sea and air navigators worldwide because of its convenience when working with charts. Most nautical charts use the
Mercator projection whose scale varies by about a factor of six from the equator to 80° latitude, so charts covering large areas cannot use a single linear scale. The nautical mile is nearly equal to a minute of latitude on a chart, so a distance measured with a chart divider can be roughly converted to nautical miles using the chart's latitude scale.
The "international nautical mile" was defined by the
First International Extraordinary Hydrographic
Conference,
Monaco as exactly 1,852 metres. This is the only definition in widespread current use, and is the one accepted by the
International Hydrographic Organization and by the
International Bureau of
Weights and Measures . Before 1929 different countries had different definitions, and the
Soviet Union, the
United Kingdom and the
United States did not immediately accept the international value.
The Imperial and
U.S. definitions of the nautical mile were based on the
Clarke Spheroid: they were different approximations to the length of one minute of arc along a great circle of a sphere having the same surface area as the Clarke Spheroid.
The United States nautical mile was defined as 1,853.248 metres : it was abandoned in favour of the international nautical mile in 1954. The Imperial nautical mile, also known as the "
Admiralty mile", was defined in terms of the knot, such that one nautical mile was exactly 6,080 international feet : it was abandoned in
1970 and, for legal purposes, old references to
the obsolete unit are now converted to 1,853 metres exactly.
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Disclaimer: This video is for your information only. The author or publisher does not guarantee the accuracy of the content presented in this video. USE AT YOUR OWN RISK.
Background Music:
"The Place Inside" by Silent Partner (royalty-free) from YouTube Audio Library.
This video uses material/images from https://en.wikipedia.org/wiki/Nautical+mile, which is released under Creative Commons Attribution-Share-Alike License 3.0 http://creativecommons.org/licenses/by-sa/3.0/ . This video is licensed under Creative Commons Attribution-Share-Alike License 3.0 http://creativecommons.org/licenses/by-sa/3.0/ . To reuse/adapt the content in your own work, you must comply with the license terms.