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Meridian (geography)

 
Meridian (geography)

 
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Meridian (geography)
 
 
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A meridian (or line of longitude) is an imaginary arc on the Earth's surface from the North Pole
North Pole

The North Pole, also known as the Geographic North Pole or Terrestrial North Pole is, subject to the caveats explained below, defined as the point in the northern hemisphere where the Earth's axis of rotation meets the Earth's surface....
 to the South Pole
South Pole

The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's rotation intersects the surface....
 that connects all locations running along it with a given longitude
Longitude

Longitude , symbolized by the Greek character lambda , is the geographic coordinate most commonly used in cartography and global navigation for east-west measurement....
. The position of a point on the meridian is given by the latitude
Latitude

Latitude, usually denoted symbolically by the Greek letter phi gives the location of a place on Earth north or south of the equator. Lines of Latitude are the horizontal lines shown running east-to-west on maps ....
. Each meridian is perpendicular to all circles of latitude
Circle of latitude

A circle of latitude, on the Earth, is an imaginary east-west circle connecting all locations that share a given latitude. A location's position along a circle of latitude is given by its longitude....
 at the intersection points.






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Encyclopedia


Prime Meridian
A meridian (or line of longitude) is an imaginary arc on the Earth's surface from the North Pole
North Pole

The North Pole, also known as the Geographic North Pole or Terrestrial North Pole is, subject to the caveats explained below, defined as the point in the northern hemisphere where the Earth's axis of rotation meets the Earth's surface....
 to the South Pole
South Pole

The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is one of the two points where the Earth's rotation intersects the surface....
 that connects all locations running along it with a given longitude
Longitude

Longitude , symbolized by the Greek character lambda , is the geographic coordinate most commonly used in cartography and global navigation for east-west measurement....
. The position of a point on the meridian is given by the latitude
Latitude

Latitude, usually denoted symbolically by the Greek letter phi gives the location of a place on Earth north or south of the equator. Lines of Latitude are the horizontal lines shown running east-to-west on maps ....
. Each meridian is perpendicular to all circles of latitude
Circle of latitude

A circle of latitude, on the Earth, is an imaginary east-west circle connecting all locations that share a given latitude. A location's position along a circle of latitude is given by its longitude....
 at the intersection points. Each is also the same size, being half of a great circle
Great circle

A great circle of a sphere is a circle that runs along the surface of that sphere so as to cut it into two equal halves. The great circle therefore has both the same circumference and the same center as the sphere....
 on the Earth's surface and therefore measuring 20,003.93 km.

Since the meridian that passes through Greenwich, England, establishes the meaning of zero degrees of longitude, or the Prime Meridian
Prime Meridian

The Prime Meridian is the meridian at which longitude is defined to be 0?.The Prime Meridian and the opposite 180th meridian , which the International Date Line generally follows, form a great circle that divides the Earth into the Eastern Hemisphere and Western Hemispheres....
, any other meridian is identified by the angle, referenced to the center of the earth as vertex, 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 (which forms the other half of a circle with the two through Greenwich) is 180° longitude
180th meridian

The 180th meridian or antimeridian is the meridian defined as 180? longitude. It is the line of longitude exactly opposite the Prime Meridian....
, and the others lie between 0° and 180° of West longitude in the Western Hemisphere
Western Hemisphere

The Western Hemisphere, also Western hemisphere or western hemisphere, is a geography term for the half of the Earth that lies west of the Prime Meridian , the other half being the Eastern Hemisphere....
 (west of Greenwich) and between 0° and 180° of East longitude in the Eastern Hemisphere
Eastern Hemisphere

The Eastern Hemisphere, also Eastern hemisphere or eastern hemisphere, is a geography term for the half of the Earth that is east of the Prime Meridian and west of 180? longitude....
 (east of Greenwich). You can see the lines of longitude on most maps.

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 Meridian) and P.M. (Post Meridian)
12-hour clock

The 12-hour clock is a time conversion convention in which the 24 hours of the day are divided into two periods called ante meridiem and post meridiem ....
 used to disambiguate hours of the day when using the 12-hour clock
12-hour clock

The 12-hour clock is a time conversion convention in which the 24 hours of the day are divided into two periods called ante meridiem and post meridiem ....
.

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. 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
Magnetic declination

The magnetic declination at any point on the Earth is the angle between the local magnetic field -- the direction the north end of a compass points -- and true north....
, which is relevant for navigating with a compass.

See also

  • Prime Meridian
    Prime Meridian

    The Prime Meridian is the meridian at which longitude is defined to be 0?.The Prime Meridian and the opposite 180th meridian , which the International Date Line generally follows, form a great circle that divides the Earth into the Eastern Hemisphere and Western Hemispheres....
     (includes other reference meridians)
  • Meridian (astronomy)
    Meridian (astronomy)

    This article is about the astronomical concept. For other uses of the word, see meridian .In the sky, a meridian is an imaginary great circle on the celestial sphere....


For meridians used as references in surveying:
  • Public Land Survey System
    Public Land Survey System

    File:US-DOI-BLM-logo.pngThe Public Land Survey System is a method used in the United States to survey and identify land parcels, particularly for titles and deeds of rural, wild or undeveloped land....
    , United States
  • Dominion Land Survey
    Dominion Land Survey

    The Dominion Land Survey is the method used to divide most of Western Canada into one-square-mile sections for agricultural and other purposes....
    , Canada


External links

  • Note: This is a large file, approximately 46MB. Searchable PDF prepared by the author, C. A. White.