A nautical mile or sea mile is a unit of length. It is a non-SI unit used by special interest groups such as navigators in the shipping and aviation industries.^[1] It is commonly used in international law and treaties, especially regarding the limits of territorial waters. It developed from the geographical mile. “SI” redirects here. ... This article is about the unit of length. ... “km” redirects here. ... U.S. customary units, also known in the United States as English units[1] (but see English unit) or standard units, are units of measurement that are currently used in the USA, in some cases alongside units from SI (the International System of Units — the modern metric system). ... The Imperial units are an irregularly standardized system of units that have been used in the United Kingdom and its former colonies, including the Commonwealth countries. ... A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′ – a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ... “Miles” redirects here. ... For other uses of this word, see Length (disambiguation). ... “SI” redirects here. ... A navigator is the person onboard a ship responsible for the navigation of the vessel. ... Damaged package The Panama canal. ... Look up aviation in Wiktionary, the free dictionary. ... This article or section is in need of attention from an expert on the subject. ... This does not cite any references or sources. ... Map of Sealand and the United Kingdom, with territorial water claims of 3nm and 12nm shown. ... The geographical mile is a unit of length determined by 1 minute of arc along the Earths equator, approximately equal to 1855 metres (6087. ...

Definition

The international standard definition is: 1 nautical mile = 1852 metres exactly.^[1] This corresponds approximately to one minute of latitude along any meridian. Standards are produced by many organizations, some for internal usage only, others for use by a groups of people, groups of companies, or a subsection of an industry. ... This article is about the unit of length. ... This article does not cite any references or sources. ... This article is about the geographical term. ...

Unit symbol

There is no widely accepted international standard symbol for the unit nautical mile. The preferred abbreviation of the IEEE is nmi,^[2] while M is used by the BIPM^[1] and the maritime authorities of the USA^[3], and Canada ^[4]. For aviation use, the preferred abbreviation of the ICAO is NM.^[5] The abbreviation nm, though conflicting with the SI symbol for the nanometre, is also in widespread use. The Institute of Electrical and Electronics Engineers or IEEE (pronounced as eye-triple-ee) is an international non-profit, professional organization incorporated in the State of New York, United States. ... The Bureau International des Poids et Mesures (International Bureau of Weights and Measures, or BIPM) is a standards organization, one of the three organizations established to maintain the SI system under the terms of the Metre Convention. ... The International Civil Aviation Organization (ICAO), an agency of the United Nations, develops the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth. ... A nanometre (American spelling: nanometer, symbol nm) is a unit of length in the metric system, equal to one thousand-millionth of a metre, which is the current SI base unit of length. ...

Conversions to other units

One nautical mile converts to:

• 1,852 metres (exact)
• 1.150779 mile (statute) [1] (exact: 57,875/50,292 miles)
• 2,025.372 yard (exact: 2,315,000/1,143 yards)
• 6,076.1155 feet (exact: 2,315,000/381 feet)
• 1,012.6859 fathoms (exact: 1,157,500/1,143 fathoms)
• 10 common-definition cables (exact, as one common definition of "cable")
• 10.126859 "ordinary" (100-fathom) cables (exact: 11,575/1,143 ordinary cables)
• 12.152231 US Navy (120-fathom) cables (exact: 9,260/762 US Navy cables)
• 0.998383 equatorial arc minutes = traditional geographical miles (approx.)
• 0.9998834 mean meridian arc minutes = mean historical nautical miles (approx.)

metre or meter, see meter (disambiguation) The metre is the basic unit of length in the International System of Units. ... “Miles” redirects here. ... A yard (abbreviation: yd) is the name of a unit of length in a number of different systems, including English units, Imperial units, and United States customary units. ... A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′ – a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ... A fathom is the name of a unit of length in the Imperial system (and the derived U.S. customary units). ... A cable length is a nautical unit of measure, for which at least four definitions seem to exist: Common definition: 1/10 nautical mile, i. ... A fathom is the name of a unit of length in the Imperial system (and the derived U.S. customary units). ... A cable length is a nautical unit of measure, for which at least four definitions seem to exist: Common definition: 1/10 nautical mile, i. ... A fathom is the name of a unit of length in the Imperial system (and the derived U.S. customary units). ... A cable length is a nautical unit of measure, for which at least four definitions seem to exist: Common definition: 1/10 nautical mile, i. ... A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60) of one degree. ... The geographical mile is a unit of length determined by 1 minute of arc along the Earths equator, approximately equal to 1855 metres (6087. ... A minute of arc, arcminute, or MOA is a unit of angular measurement, equal to one sixtieth (1/60) of one degree. ...

History

Historical definition - 1 nautical mile

The nautical mile was historically defined as a minute of arc along a meridian of the Earth, making a meridian exactly 180×60 = 10,800 historical nautical miles. It can therefore be used for approximate measures on a meridian as change of latitude on a nautical chart. The originally intended definition of the metre as 10^-7 of a half-meridian makes the mean historical nautical mile exactly (2×10⁷)/10,800 = 1,851.851851… historical metres. Based on the current IUGG meridian of 20,003,931.4585 (standard) metres the mean historical nautical mile is 1,852.216 m. Image File history File links No higher resolution available. ... This article does not cite any references or sources. ... On the earth, a meridian is a north-south line between the North Pole and the South Pole. ... This article is about the geographical term. ... A 1976 United States NOAA chart of part of Puerto Rico A nautical chart is a graphic representation of a maritime area and adjacent coastal regions. ... The International Union of Geodesy and Geophysics, or IUGG, is a non-governmental organisation dedicated to the scientific study of the Earth and to the application of the knowledge gained to the needs of society that was established in 1919. ...

The historical definition differs from the length-based standard in that a minute of arc, and hence a nautical mile, is not a constant length at the surface of the Earth but gradually lengthens with increasing distance from the equator, as a corollary of the Earth's oblateness, whence the need for "mean" in the preceding sentence. According to WGS84, the radius of curvature in a meridian plane is 6,399,593.6258 metres at the poles and 6,335,439.3273 metres at the Equator. By the definition of geodetic latitude, the length of a minute of arc depends on the radius of curvature. This radius generally does not pass through Earth's center, except for the latitudes of 0° (equator) and 90° (poles). This length equals about 1,861.57 metres at the poles and 1,842.90 metres at the Equator, a variation of one percent. An oblate spheroid is ellipsoid having a shorter axis and two equal longer axes. ... WGS 84 is the 1984 revision of the World Geodetic System. ... The distance from the center of a sphere or ellipsoid to its surface is its radius. ... This article is about the geographical term. ...

The length of a minute of arc defined by geocentric latitude also depends on the radius of curvature along a meridian on the surface of the Earth, but a specific length occurs at a different latitude because a surface feature's geocentric latitude differs by as much as 12 arc-minutes (at 45°) from its geodetic latitude. The naive definition of an arc minute as the distance over which one's (three-dimensional) trajectory turns one minute when sailing due north corresponds to geodetic latitude; if instead one measures it by the turning of a line between the vessel and the center of the earth this corresponds to geocentric latitude. This article is about the geographical term. ...

Other nations had different definitions of the nautical mile. This variety in combination with the complexity of angular measure described above along with the intrinsic uncertainty of geodetically derived units mitigated against the extant definitions in favor of a simple unit of pure length. International agreement was achieved in 1929 when the International Extraordinary Hydrographic Conference held in Monaco adopted a definition of one (1) international nautical mile as being equal to 1,852 metres exactly, in excellent agreement (for an integer) with both the above-mentioned values of 1,851.851 historical metres and 1,852.216 standard metres. The International Hydrographic Organization (IHO) is an intergovernmental international organization established in 1921. ... To help compare different orders of magnitude this page lists lengths between 1 km and 10 km (103 and 104 m). ...

Since the 1929 agreement, all nations have now adopted the international definition. The United States, formerly using a value of 1,853.248 m (6,080.2 ft), did not however adopt this definition until July 1, 1954.^[6]

British nautical mile (admiralty)

The British definition of the nautical mile originally related to the length on the surface of the Earth just south of Great Britain. It was not specified according to a calibrated measurement of the Earth, but chosen as exactly 800 feet longer than a statute mile, namely 6,080 feet. For disambiguation, this is sometimes called the "admiralty mile" after the British Admiralty. The precise definition of the foot varied slightly around the world until the international yard, always equal to exactly three feet, was standardized at exactly 0.9144 m in 1959, making the admiralty mile exactly 1,853.184 m. The Royal Hydrographic Office of the United Kingdom converted to the international definition in 1970. A mile is any of several units of distance, or, in physics terminology, of length. ... For the international law of the sea, see Admiralty law. ... A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′ – a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ... A yard (abbreviation: yd) is the name of a unit of length in a number of different systems, including English units, Imperial units, and United States customary units. ... A hydrographic office is an organisation which is devoted to acquiring and publishing hydrographic information. ...

US navy nautical mile (rocketry)

As a simpler approximation, designers of radar systems for ballistic and cruise missiles for use by the United States Navy in the 1950s would take 6,000 feet (1,828.8 m) as their equivalent of a nautical mile. In the past, some ship-borne computer systems developed for the Royal Navy also used the "data mile" of 6,000 feet, and the more unusual "foot*", equivalent to about nine inches, defined as 6,000/8,192 feet (223 mm). A Taurus KEPD 350 cruise missile of the Luftwaffe A cruise missile is a guided missile which uses a lifting wing and most often a jet propulsion system to allow sustained flight. ... USN redirects here. ... This article or section is in need of attention from an expert on the subject. ... This article is about the navy of the United Kingdom. ...

Associated units

The derived unit of speed is the knot, defined as one nautical mile per hour. The term "log" is used to measure the distance a vessel has moved through the water, it can also be used to measure the speed through the water (see chip log) as the speed and distance are directly related. This article does not cite any references or sources. ... A knot is a unit of speed abbreviated kt or kn. ... The hour (symbol: h) is a unit of time. ... A chip log is a navigational tool used by mariners to determine speed through the water. ...

The term knot and log originally are derived from the practice of using a "log" tied to a knotted rope as a method of gauging speed of a ship. The log would be thrown into the water and the rope trailed behind the ship. The number of knots that passed off the ship and into the water in a given time would determine the speed in "knots". The present day measurement of knots and log are determined using a mechanical tow, electronic tow, retractable hull-mounted unit, doppler or ultrasonics, or GPS.^[7][8] This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Ultrasound is sound with a frequency greater than the upper limit of human hearing, approximately 20 kilohertz. ... GPS redirects here. ...

See also

Nautical Portal

• conversion of units
• knot for the unit of speed
• mile for other types of mile
• orders of magnitude (length)

Image File history File links No higher resolution available. ... Conversion of units refers to conversion factors between different units of measurement for the same quantity. ... A knot is a unit of speed abbreviated kt or kn. ... “Miles” redirects here. ... Categories: | ...

Notes

The Bureau International des Poids et Mesures (International Bureau of Weights and Measures, or BIPM) is a standards organization, one of the three organizations established to maintain the SI system under the terms of the Metre Convention. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st Century. ... is the 214th day of the year (215th in leap years) in the Gregorian calendar. ...

References

• Moritz, H. (1980). "Geodetic Reference System". Bulletin Geodesique 54 (3).  (IUGG/WGS-84 data)
• Taff, Laurence G. (1981). Computational Spherical Astronomy. John Wiley and Sons.  (IAU data)

External links

• National Bureau of Standards: Refinement of values for the yard and the pound (1959)