Prime Meridian
The Prime Meridian is the meridian
Meridian (geography)
A meridian 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...

 (line of longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

) at which the longitude is defined to be 0°.

The Prime Meridian and its opposite the 180th meridian
180th meridian
The 180th meridian or antimeridian is the meridian which is 180° east or west of the Prime Meridian passing through the Royal Observatory, Greenwich. It is common to both east longitude and west longitude. It is used as the basis for the International Date Line because it for the most part passes...

 (at 180° longitude), which the International Date Line
International Date Line
The International Date Line is a generally north-south imaginary line on the surface of the Earth, passing through the middle of the Pacific Ocean, that designates the place where each calendar day begins...

 generally follows, form a great circle
Great circle
A great circle, also known as a Riemannian circle, of a sphere is the intersection of the sphere and a plane which passes through the center point of the sphere, as opposed to a general circle of a sphere where the plane is not required to pass through the center...

 that divides the Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 into the Eastern
Eastern Hemisphere
The Eastern Hemisphere, also Eastern hemisphere or eastern hemisphere, is a geographical term for the half of the Earth that is east of the Prime Meridian and west of 180° longitude. It is also used to refer to Europe, Asia, Africa, and Australasia, vis-à-vis the Western Hemisphere, which includes...

 and Western
Western Hemisphere
The Western Hemisphere or western hemisphere is mainly used as a geographical term for the half of the Earth that lies west of the Prime Meridian and east of the Antimeridian , the other half being called the Eastern Hemisphere.In this sense, the western hemisphere consists of the western portions...


An international conference in 1884 decided the modern Prime Meridian passes through the Royal Observatory, Greenwich
Royal Observatory, Greenwich
The Royal Observatory, Greenwich , in London, England played a major role in the history of astronomy and navigation, and is best known as the location of the prime meridian...

 in southeast London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

, United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, known as the International Meridian or Greenwich Meridian, although the Prime Meridian is ultimately arbitrary unlike the parallels of latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

, which are defined by the rotational axis of the Earth with the Poles
Geographical pole
A geographical pole is either of the two points—the north pole and the south pole—on the surface of a rotating planet where the axis of rotation meets the surface of the body...

 at 90° and the Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

 at 0°.

Historically, various meridians have been used, including four different ones through Greenwich.
Starting at 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 its surface...

 and heading south 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 axis of rotation intersects its surface. It is the southernmost point on the surface of the Earth and lies on the opposite side of the Earth from the North Pole...

, the Prime Meridian passes through:

The Prime Meridian is ultimately arbitrary—a matter of convention—and various conventions have been used or advocated in different regions and throughout history:
  • Washington, D.C.
    Washington, D.C.
    Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....

     (77° 3' 2.3” W), see Washington meridian
    Washington meridian
    The Washington meridian was one of four prime meridians of the United States which passed through Washington, D.C.. The four which have been specified are:# through the Capitol# through the White House# through the old Naval Observatory...

  • Philadelphia
    Philadelphia, Pennsylvania
    Philadelphia is the largest city in the Commonwealth of Pennsylvania and the county seat of Philadelphia County, with which it is coterminous. The city is located in the Northeastern United States along the Delaware and Schuylkill rivers. It is the fifth-most-populous city in the United States,...

     (75° 10' 12” W)
  • Rio de Janeiro
    Rio de Janeiro
    Rio de Janeiro , commonly referred to simply as Rio, is the capital city of the State of Rio de Janeiro, the second largest city of Brazil, and the third largest metropolitan area and agglomeration in South America, boasting approximately 6.3 million people within the city proper, making it the 6th...

     (43° 10' 19” W)
  • El Hierro (Ferro)
    El Hierro
    El Hierro, nicknamed Isla del Meridiano , is the smallest and farthest south and west of the Canary Islands , in the Atlantic Ocean off the coast of Africa, with a population of 10,162 .- Name :The name El Hierro, although phonetically identical to the Spanish word for 'iron', is generally thought...

    , Canary Islands (18° 03' W, later redefined as 17° 39' 46”? W)
  • Lisbon
    Lisbon is the capital city and largest city of Portugal with a population of 545,245 within its administrative limits on a land area of . The urban area of Lisbon extends beyond the administrative city limits with a population of 3 million on an area of , making it the 9th most populous urban...

     (9° 07' 54.862” W)
  • Madrid
    Madrid is the capital and largest city of Spain. The population of the city is roughly 3.3 million and the entire population of the Madrid metropolitan area is calculated to be 6.271 million. It is the third largest city in the European Union, after London and Berlin, and its metropolitan...

     (3° 41' 16.58” W)
  • Paris
    Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

     (2° 20' 14.025” E), see Paris Meridian
    Paris Meridian
    The Paris Meridian is a meridian line running through the Paris Observatory in Paris, France—now longitude 2°20′14.025″ east. It was a long-standing rival to Greenwich as the prime meridian of the world, as was the Meridian of Antwerp in Antwerp, Belgium....

  • Brussels
    Brussels , officially the Brussels Region or Brussels-Capital Region , is the capital of Belgium and the de facto capital of the European Union...

     (4° 22' 4.71” E)
  • Antwerp (4° 24' E), used by Mercator, see Meridian of Antwerp
    Meridian of Antwerp
    The Meridian of Antwerp is an analog to the Paris Meridian and Prime Meridian, running through the city of Antwerp, in Flanders, Belgium, and forming the 0° longitude upon which some Belgian maps were based...

  • Bern (7° 26' 22.5” E)
  • Pisa
    Pisa is a city in Tuscany, Central Italy, on the right bank of the mouth of the River Arno on the Tyrrhenian Sea. It is the capital city of the Province of Pisa...

    , Italy
    Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

     (10°24' E)
  • Oslo (Kristiania)
    Oslo is a municipality, as well as the capital and most populous city in Norway. As a municipality , it was established on 1 January 1838. Founded around 1048 by King Harald III of Norway, the city was largely destroyed by fire in 1624. The city was moved under the reign of Denmark–Norway's King...

     (10° 43' 22.5” E)
  • Rome
    Rome is the capital of Italy and the country's largest and most populated city and comune, with over 2.7 million residents in . The city is located in the central-western portion of the Italian Peninsula, on the Tiber River within the Lazio region of Italy.Rome's history spans two and a half...

     (12° 27' 08.4” E), meridian of Monte Mario
    Monte Mario
    -External links :* * *...

  • Copenhagen
    Copenhagen is the capital and largest city of Denmark, with an urban population of 1,199,224 and a metropolitan population of 1,930,260 . With the completion of the transnational Øresund Bridge in 2000, Copenhagen has become the centre of the increasingly integrating Øresund Region...

     (12° 34' 32.25” E) Rundetårn
    The Rundetårn is a 17th-century tower located in central Copenhagen, Denmark. One of the many architectural projects of Christian IV, it was built as an astronomical observatory...

  • Stockholm
    Stockholm is the capital and the largest city of Sweden and constitutes the most populated urban area in Scandinavia. Stockholm is the most populous city in Sweden, with a population of 851,155 in the municipality , 1.37 million in the urban area , and around 2.1 million in the metropolitan area...

     (18° 3' 29.8” E), at the observatory
    Stockholm Observatory
    The Stockholm Observatory is an astronomical institution in Stockholm, Sweden, founded in the 18th century and today part of Stockholm University...

  • Warsaw
    Warsaw is the capital and largest city of Poland. It is located on the Vistula River, roughly from the Baltic Sea and from the Carpathian Mountains. Its population in 2010 was estimated at 1,716,855 residents with a greater metropolitan area of 2,631,902 residents, making Warsaw the 10th most...

     (21° 00’ 42” E), see Warsaw meridian
    Warsaw meridian
    The Warsaw meridian is a meridian line running through Warsaw. The local mean time at the meridian was known as Warsaw mean time. It corresponds to an offset from UTC of +01:24....

  • Oradea
    Oradea is the capital city of Bihor County, in the Crișana region of north-western Romania. The city has a population of 204,477, according to the 2009 estimates. The wider Oradea metropolitan area has a total population of 245,832.-Geography:...

    , Romania
    Romania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...

     (21° 55' 16” E)
  • Alexandria
    Alexandria is the second-largest city of Egypt, with a population of 4.1 million, extending about along the coast of the Mediterranean Sea in the north central part of the country; it is also the largest city lying directly on the Mediterranean coast. It is Egypt's largest seaport, serving...

     (29° 53' E)
  • Saint Petersburg
    Saint Petersburg
    Saint Petersburg is a city and a federal subject of Russia located on the Neva River at the head of the Gulf of Finland on the Baltic Sea...

     (30° 19' 42.09” E), Pulkovo meridian
  • Great Pyramid of Giza
    Great Pyramid of Giza
    The Great Pyramid of Giza is the oldest and largest of the three pyramids in the Giza Necropolis bordering what is now El Giza, Egypt. It is the oldest of the Seven Wonders of the Ancient World, and the only one to remain largely intact...

     (31° 8' 3.69” E), 1884
  • Jerusalem (35° 13' 47.1” E), for the small dome of the Church of the Holy Sepulchre
    Church of the Holy Sepulchre
    The Church of the Holy Sepulchre, also called the Church of the Resurrection by Eastern Christians, is a church within the walled Old City of Jerusalem. It is a few steps away from the Muristan....

  • Mecca
    Mecca is a city in the Hijaz and the capital of Makkah province in Saudi Arabia. The city is located inland from Jeddah in a narrow valley at a height of above sea level...

     (39° 49′ 34″ E), see Mecca Time
    Mecca Time
    Mecca Time is a time standard that uses the line of longitude that goes through Mecca, Saudi Arabia as its Prime Meridian. Its proposed use as a global standard is based on the claim that the city is the true center of the Earth and thus should become the basis of the world's timezones...

  • Approximately 59° east of Greenwich
  • Ujjain
    Ujjain , is an ancient city of Malwa region in central India, on the eastern bank of the Kshipra River , today part of the state of Madhya Pradesh. It is the administrative centre of Ujjain District and Ujjain Division.In ancient times the city was called Ujjayini...

     (75° 47' E), Used from 4th century CE Indian astronomy and calendars.
  • Kyoto
    is a city in the central part of the island of Honshū, Japan. It has a population close to 1.5 million. Formerly the imperial capital of Japan, it is now the capital of Kyoto Prefecture, as well as a major part of the Osaka-Kobe-Kyoto metropolitan area.-History:...

     (135° 74' E), Used in 18th and 19th (officially 1779-1871) century Japanese maps.