Nautical mile

A nautical mile is a unit of distance, or, as physical scientists like to call it, length. It is widely used around the world for maritime and aviation purposes.

The international nautical mile is defined as exactly 1,852 metres. This definition was adopted in 1929 by the International Extraordinary Hydrographic Conference, Monaco. The United States adopted it in 1954. Prior to the adoption of the international nautical mile, the nautical mile used by the US and the UK was 6080 feet, or 1853.184 metres.

The nautical mile is a minute of arc along a great circle of the Earth at the equator. In practice the nautical mile is measured on a meridian as change of latitude on a map, as the nautical mile is only a minute of arc on the equator.

The abbreviation "nm" is used. The same abbreviation, "nm", is also used to denote nanometre in the SI though little confusion is generated from this, as the contexts of use are very different. For example, the 'nm' abbreviation is typically seen in listings of aircraft flight range, but listed next to the range in kilometers (km). ([Example (http://www.airliners.net/info/stats.main?id=400)] of nm, km together- in performance section). Also, the large ratio of 1.852 trillion makes confusion unlikely in most cases. The abbreviation nmi is also used.

One knot is a unit of speed defined as one nautical mile per hour. It is therefore 1852 metres per hour exactly.

See also: conversion of units, orders of magnitude (length).

NMI is also the name of a joint venture responsible for the construction of the Dublin Port Tunnel.

NMI also stands for Non-Maskable Interrupt, a type of interrupt on several types of computers, such as the IBM PC and Apple II, that causes the CPU to stop what it was doing, change the program counter to point to a particular address, and continue executing code from that location. Programmers are unable to program the CPU to ignore these interrupts, hence the term "non-maskable".

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