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The prime meridian at Greenwich, England. The meridian is actually about 200 metres east of this point since the adoption of WGS84.

A meridian (or line of longitude) is an imaginary line on the Earth's surface from the North Pole to the South Pole that connects all locations along it with a given longitude. The position of a point along the meridian is given by its latitude. Each meridian is perpendicular to all circles of latitude. Each is also the same size, being half of a great circle on the Earth's surface and therefore measuring 20,003.93 km (12,429.9 miles).

Geographic[link]

The meridian through Greenwich, England, also called the Prime Meridian was set at zero degrees of longitude, with other meridians being defined by the angle at the center of the earth between where it and the prime meridian cross the equator. As there are 360 degrees in a circle, the meridian on the opposite side of the earth from Greenwich, forming the other half of a circle with the one through Greenwich, is 180° longitude, and the others lie between 0° and 180° of West longitude in the Western Hemisphere (West of Greenwich) and between 0° and 180° of East longitude in the Eastern Hemisphere (East of Greenwich). Most maps show the lines of longitude.

The position of the meridian has changed a few times throughout history, mainly due to the transit observatory being built next door to the previous one (to maintain the service to shipping). Such changes have had no significant effect as historically, the accuracy of the determination of longitude was much larger than the change in position. The adoption of WGS84 as the positioning system, has moved the meridian approximately 200 metres east of its last position (measured at Greenwich). The position of the current meridian is not identified at all in Greenwich but may easily be located using a GPS receiver.

The term "meridian" comes from the Latin meridies, meaning "midday"; the sun crosses a given meridian midway between the times of sunrise and sunset on that meridian. The same Latin stem gives rise to the terms a.m. (ante meridiem) and p.m. (post meridiem) used to disambiguate hours of the day when using the 12-hour clock.

Magnetic[link]

The magnetic meridian is an equivalent imaginary line connecting the magnetic south and north poles and can be taken as the magnetic force lines along the surface of the earth.^{[1][dubious – discuss]} That is, a compass needle will be parallel to the magnetic meridian. The angle between the magnetic and the true meridian is the magnetic declination, which is relevant for navigating with a compass.^[2]

See also[link]

• Meridian (astronomy)
• Meridian lines used with a gnomon to measure solar elevation and time of year
• Meridian arc

For meridians used as references in surveying:

• Public Land Survey System, United States
• Dominion Land Survey, Canada

References[link]

1. ^ http://www.met.gov.pk/Subpage4/geomagnotes.html^{[dead link]}
2. ^ http://brunelleschi.imss.fi.it/museum/esim.asp?c=100234

External links[link]

• The Principal Meridian Project (US)
• [1] Note: This is a large file, approximately 46MB. Searchable PDF prepared by the author, C. A. White.
• Resources page of the U.S. Department of the Interior, Bureau of Land Management

v t e Circles of latitude / Meridians Equator Tropic of Cancer Tropic of Capricorn Arctic Circle Antarctic Circle Equator Tropic of Cancer Tropic of Capricorn Arctic Circle Antarctic Circle Equator Tropic of Cancer Tropic of Capricorn Arctic Circle Antarctic Circle W 0° E 30° 60° 90° 120° 150° 180° 30° 60° 90° 120° 150° 180° 5° 15° 25° 35° 45° 55° 65° 75° 85° 95° 105° 115° 125° 135° 145° 155° 165° 175° 5° 15° 25° 35° 45° 55° 65° 75° 85° 95° 105° 115° 125° 135° 145° 155° 165° 175° 10° 20° 40° 50° 70° 80° 100° 110° 130° 140° 160° 170° 10° 20° 40° 50° 70° 80° 100° 110° 130° 140° 160° 170° 0° 10° 20° 30° 40° 50° 60° 70° 80° 90° 10° 20° 30° 40° 50° 60° 70° 80° 90° 5° N 15° 25° 35° 45° 55° 65° 75° 85° 5° S 15° 25° 35° 45° 55° 65° 75° 85° 45x90 45x90 45x90 45x90

Look up meridian in Wiktionary, the free dictionary.

Meridian, or a meridian line may refer to:

Earth science[link]

• Meridian (astronomy), imaginary circle in a plane perpendicular to the planes of the celestial equator and horizon
• Meridian (geography), an imaginary arc on the Earth's surface from the North Pole to the South Pole
• Meridian arc

United States geography[link]

• Meridian, California (disambiguation)
  • Meridian, Humboldt County, California
  • Meridian, Kern County, California
  • Meridian, Santa Clara County, California, a place in Santa Clara County
  • Meridian, Sutter County, California
• Meridian, Colorado
• Meridian, Florida
• Meridian, Idaho
• Meridian, Mississippi
• Meridian, New York
• Meridian, Oklahoma (disambiguation)
  • Meridian, Logan County, Oklahoma
  • Meridian, Stephens County, Oklahoma
• Meridian, Pennsylvania
• Meridian, Seattle, Washington
• Meridian, Texas
• Meridian Township, Clinton County, Illinois
• Meridian Charter Township, Michigan

Arts and entertainment[link]

Print[link]

• Meridian (novel), novel by Alice Walker
• Meridian (comics), comic book series published by CrossGen in the early 2000s
• Meridian, a literary journal published by the University of Virginia
• Meridian (W.I.T.C.H.), a fictional realm in the Italian comic book series W.I.T.C.H.

Film and television[link]

• Meridian: Kiss of the Beast, 1990 movie
• "Meridian" (Star Trek: Deep Space Nine), episode of the series
• "Meridian" (Stargate SG-1), an episode of Stargate SG-1
• Meridian Broadcasting, ITV station for the south and south-east of England

Business[link]

• Meridian Audio, Ltd., British manufacturer of audio equipment
• Meridian Bank, bank based in Serbia
• Meridian Credit Union, a credit union based in Ontario, Canada
• Meridian Energy, New Zealand electricity generation and electricity retailing company
• Nortel Meridian, a popular PBX telephone system
• Meridian Mall, Meridian Township, Michigan, US
• Meridian Mall, Dunedin, New Zealand

Education[link]

• Meridian High School (disambiguation)
• Meridian Technology Center, Stillwater, Oklahoma, United States

Transportation[link]

• Meridian (train), British Rail Class 222 trains
• MS Meridian, cruise ship constructed in 1961
• Meridian (schooner) Shipwreck Site, sunken schooner in Lake Michigan
• Piper Meridian, turboprop model of the Piper PA-46 aircraft

Other[link]

• Meridian (Chinese medicine), or channel, for blood and qi
• Meridian (perimetry, visual field), polar coordinate system for the visual field
• Meridian F.C., an English non-league football club
• Meridian Hall, listed on the National Register of Historic Places in Washington, D. C.
• Meridian Manor, listed on the National Register of Historic Places in Washington, D. C.
• Meridian Mansions, listed on the National Register of Historic Places in Washington, D. C.
• Meridian Records, a record label
• Meridian (Nosgoth), the capitol of Nosgoth in Blood Omen 2: Legacy of Kain
• Meridian (horse), American Thoroughbred racehorse, winner of 1911 Kentucky Derby

People with the name[link]

• Meridian Green, California-based folk musician

See also[link]

• Meridian 59, online game
• One Meridian Plaza, an office building that burned down in 1991 in Philadelphia, Pennsylvania, US
• Meridian Hill Park, a park in Washington D.C.

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