Hvor langt er en nautisk mil? Og hva er bueminutt?

[sailorboy]

Ja der lærte jeg noe i kveld også.

 

Avstanden 1852 meter kommer hverken fra lengden rundt ekvator eller avstand ekvator til pol, men et gjennomsnitt av målinger foretatt rundt om på kloden. Altså både nord/syd og øst/vest. Dette ble bestemt ved en konferanse tilbake i Monaco i 1929. Som vi vet er jorden flattrykt på polene, og avstand rundt ekvator er lenger enn avstand rundt jorden gjennom polene. Dagens målinger som ligger til grunn for all GPS navigasjon gir derimot en annen verdi for denne avstand. Se WGS84 koordinat system.

 

Koordinaten.de

 

History

The nautical mile was historically defined as a minute of arc along a great circle of the Earth. It can therefore be used for approximate measures on a meridian as change of latitude on a nautical chart. However, like all planets, the Earth is not a perfect sphere. It bulges at the equator like a spinning top, so the length of one minute of arc on the Earth's surface varies from 1862 m at the poles to 1843 m at the Equator. The Earth's surface also has bumps and hollows like a potato. Thus, there is no fixed relationship between angle and arc length along the Earth's surface; one minute of arc can vary in length by tens of metres.

 

The British definition related to the length on the surface of the Earth just south of Great Britain. It was 6080 feet exactly (1853.184 metres). The Royal Hydrographic Office of the United Kingdom converted to the international definition in 1970.

 

In the United States, the nautical mile was defined as 6080.2 ft (1853.249 m). It adopted the international definition in 1954.

 

The precise definition of the foot varied slightly around the world until a standard definition of the international yard, always equal to exactly 3 feet, was agreed upon in 1959.

 

Other nations had different definitions of the NM. International agreement was achieved in 1929, when the International Extraordinary Hydrographic Conference, Monaco adopted a definition of 1 international nautical mile = 1,852 metres, very close to the average length of one minute of latitude i.e. one minute of arc along a line of longitude (a meridian). In subsequent years, nations adopted the international definition.

 

sailorBoy