Geographical mile: Difference between revisions

Latest revision as of 20:51, 11 April 2009

The geographical mile is a unit of length determined by 1 minute of arc along the Earth's equator, approximately equal to 1855.325 metres (6087.025 international feet). Any greater precision depends more on choice of standard than on more careful measurement: the length of the equator in the World Geodetic System WGS-84 is 40,075,016.6856 m which makes the geographical mile 1855.3248 m, while the International Astronomical Union standard IAU-2000 takes the equator to be 40,075,035.5351 m making the geographical mile 1855.3257 m, almost a millimetre longer.

The unit is not used much; it is closely related to the nautical mile, which was originally determined as 1 minute of arc along a great circle of the Earth but is nowadays defined as exactly 1852 metres.

The Danish and German geographical mile (geografisk mil and geographische Meile or geographische Landmeile, respectively) is 4 minutes of arc, and was defined as approximately 7421.5 metres by the astronomer Ole Rømer of Denmark. In Norway and Sweden, this 4 minute geographical mile was mainly used at sea (sjømil), up to the beginning of the 20th century.

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-The '''geographical mile''' is a unit of length determined by 1 [[minute|minute of arc]] along the [[Earth]]'s [[equator]], approximately equal to 1855 [[metre]]s (6087.15 international [[feet]]).
+The '''geographical mile''' is a unit of length determined by 1 [[minute|minute of arc]] along the [[Earth]]'s [[equator]], approximately equal to 1855.325 [[metre]]s (6087.025 international [[foot (length)|feet]]).   Any greater precision depends more on choice of standard than on more careful measurement: the length of the [[equator]] in the [[World Geodetic System]] WGS-84 is 40,075,016.6856 m which makes the geographical mile 1855.3248 m, while the [[International Astronomical Union]] standard IAU-2000 takes the [[equator]] to be 40,075,035.5351 m making the geographical mile 1855.3257 m, almost a millimetre longer.
-The unit is not used much; it is closely related to the [[nautical mile]], which was originally determined as 1 minute of arc along a [[great circle]] of the Earth and is nowadays defined to be exactly 1852 metres.
+The unit is not used much; it is closely related to the [[nautical mile]], which was originally determined as 1 minute of arc along a [[great circle]] of the Earth but is nowadays defined as exactly 1852 metres.
-The [[Denmark|Danish]] and [[Germany|German]] '''geograpical mile''' (''mil'' and ''Meile'') is 4 minutes of arc, and was defined as 7421.5 metres by the astronomer [[Ole Rømer]] of [[Denmark]]. In [[Norway]] and [[Sweden]], this geograpical mile was only used at sea. See also [[historical weights and measures]].
+The [[Denmark|Danish]] and [[Germany|German]] '''geographical mile''' (''geografisk mil'' and ''geographische Meile'' or ''geographische Landmeile'', respectively) is 4 minutes of arc, and was defined as approximately 7421.5 metres by the astronomer [[Ole Rømer]] of [[Denmark]]. In [[Norway]] and [[Sweden]], this 4 minute geographical mile was mainly used at sea (''sjømil''), up to the beginning of the 20th century.
-In [[France]] there was also a geographical [[league]], see [[historical weights and measures]].
+==See also==
-See [[mile]] for the various other miles in use, and also [[conversion of units]].
+*[[conversion of units]]
+*[[Medieval weights and measures]] for details of the geographical [[league]] of [[France]]
+*[[mile]] for the various other miles in use
+*[[nautical mile]]
+{{ntnes}}
+[[Category:Units of length]]

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Latest revision as of 20:51, 11 April 2009

See also