The thousand international sailor is a measuring unit of distance used in Navigation maritime and air. It initially indicated the length of an arc of 1 ' (a minute of arc) on a Grand circle of the terrestrial sphere.
Definition
The thousand international sailor is worth 1.852 Mètre S.The International office of the weights and measures class “thousand sailor” in the “Units apart from the IF of use with IF”.
Symbol
The BIPM specifies that there “does not exist symbol agreed upon for the international level, but the symbols M, Nm, Nm and Nmi are used. ”In France, where the term Nautique is usually used, one frequently finds the symbol Nq.
Terminology
The French official designation is thousand or thousand sailor .The denomination used by the First international hydrographic Conference extraordinary (Monaco, 1929) was thousand international sailor .
The nautical term thousand is only one literal translation of English nautical mile (language in whom one can also use sea mile besides).
It is of use in Aerial navigation and in the French National marine to use the nautical term to avoid any confusion with the Numeral adjective thousand .
History
The thousand was initially introduced for the needs for the astronomical Navigation as the minimal distance between two points from which one observes same the Astre with heights with the top of the horizon which differs one minute of angle. It is seen that this corresponds to two points where the horizontal planes (plane tangent with the Geoid) form an angle of 1 '. If the two points are on same the Méridien this is the exact definition of a variation of Latitude of 1 '.The use in navigation always was to use the thousand like equivalent of the minute of arc of Grand circle. This definition gives a measurement in meters which depends on the point where one is on the ground (~1861 meters with the pole S and ~1842 meters with the equator), and even of the direction considered (1842 meters in a North-South direction and 1855 meters in a East-West direction at the equator), but in proportions in general negligible compared to the precision of the means of navigation.
The thousand being also used in Hydrography and as reference for the definition of the Territorial water the need quickly was felt to use a constant equivalence with the meter. Various countries thus used, according to their geographical location and other criteria, various equivalences. Thus, the nautical British mile was it defined as being worth 6080 foot S (either exactly 800 feet more than the statute mile ): 1853,184 m, which is close one minute of latitude to the latitude of 50° (in the middle of the Manche). France used a value close to 1852 m corresponding to one minute of latitude to the latitude of 45°.
In 1929, the first extraordinary international hydrographic Conference, called with Monaco, fixed the value of the thousand sailor at 1.852 meters exactly (rounded figure very near average length of an arc of one minute meridian line).
With the creation of the international System of units in 1960, BIPM disadvised the use of the thousand. It is not currently any more the case.
In 1982, the Convention of the United Nations on the right of the sea employs the thousand sailor to define the concepts of territorial Sea and exclusive economic Zone.
Related units
The node (Nd) is a unit speed equal to one thousand sailor by hour.The Encablure is a length of a tenth of thousand sailor.
Two English units correspond to the degree of longitude (and not of latitude) at the equator:
- the geographical mile (thousand geographical) was fixed at 6082 feet (1853,7936 m),
- the telegraph mile (thousand telegraphic) was fixed at 6087 feet (1855,3176 m).
Approximations
If one remembers that the meter was defined in 1791 like the ten millionth part of a terrestrial quarter of meridian line, and that the thousand was the left 5400e (90 60 minutes degrees), one sees that 10 km are worth 5,4 miles (roughly only because these definitions changed since).mental Calculation:
- to pass from the miles to the kilometers, to multiply the measurement by 2 and to withdraw 10 % of the result (approximation on 1,8).
-
a speed of a node is close a speed of a half-meter a second.
One thousand corresponds about to 2000 Yard S (1 yard = 0,9144 meter)
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