Prime meridian (Greenwich)

Greenwich MeridianPrime MeridianGreenwichGreenwich Prime Meridian0 degrees longitudeanti-meridian of GreenwichGreenwich Meridian LineGreenwich meridienThe Greenwich Meridian
The future prime meridian based at the Royal Observatory, Greenwich, in London, England, was established by Sir George Airy in 1851.wikipedia
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Greenwich

Greenwich, LondonGreenwich, EnglandEast Greenwich
The future prime meridian based at the Royal Observatory, Greenwich, in London, England, was established by Sir George Airy in 1851.
Greenwich is notable for its maritime history and for giving its name to the Greenwich Meridian (0° longitude) and Greenwich Mean Time.

Royal Observatory, Greenwich

Royal Greenwich ObservatoryRoyal ObservatoryGreenwich Observatory
The future prime meridian based at the Royal Observatory, Greenwich, in London, England, was established by Sir George Airy in 1851.
It played a major role in the history of astronomy and navigation, and because the prime meridian passes through it, it gave its name to Greenwich Mean Time.

Paris meridian

Meridian of ParisArago medallionFrench meridian arc
However, France abstained from the vote, and French maps continued to use the Paris meridian for several decades.
It was a long-standing rival to the Greenwich meridian as the prime meridian of the world.

International Meridian Conference

1884 prime meridian systemabandonedcontemporaneously
In October of that year, at the behest of US President Chester A. Arthur, 41 delegates from 25 nations met in Washington, D.C., United States, for the International Meridian Conference.
It resulted in the recommendation of the Greenwich Meridian as the international standard for zero degrees longitude.

Meridian (geography)

meridianmeridiansmeridian line
By 1884, over two-thirds of all ships and tonnage used it as the reference meridian on their charts and maps.
The meridian through Greenwich (inside Greenwich Park), England, called the Prime Meridian, was set at zero degrees of longitude, while other meridians were defined by the angle at the center of the earth between where it and the prime meridian cross the equator.

World Geodetic System

WGS84WGS 84GPS coordinates
In the past, this offset has been attributed to the establishment of reference meridians for space-based location systems such as WGS 84 (which GPS relies on) or that errors gradually crept into the International Time Bureau timekeeping process.
The WGS 84 meridian of zero longitude is the IERS Reference Meridian, 5.3 arc seconds or 102 m east of the Greenwich meridian at the latitude of the Royal Observatory.

Prime meridian

GreenwichGreenwich meridianGreenwich Prime Zero meridian
It is derived but deviates slightly from the Greenwich Meridian, which was selected as an international standard in 1884.

Antarctica

AntarcticAntarctic continentReference Elevation Model of Antarctica
The portion west of the Weddell Sea and east of the Ross Sea is called West Antarctica and the remainder East Antarctica, because they roughly correspond to the Western and Eastern Hemispheres relative to the Greenwich meridian.

Greenwich Mean Time

GMTGMT+4UTC±00:00
Because of Earth's uneven angular velocity in its elliptical orbit and its axial tilt, noon (12:00:00) GMT is rarely the exact moment the Sun crosses the Greenwich meridian and reaches its highest point in the sky there.

London

London, EnglandLondon, United KingdomLondon, UK
The future prime meridian based at the Royal Observatory, Greenwich, in London, England, was established by Sir George Airy in 1851. The prime meridian was therefore long symbolised by a brass strip in the courtyard, now replaced by stainless steel, and since 16 December 1999, it has been marked by a powerful green laser shining north across the London night sky.

England

🏴󠁧󠁢󠁥󠁮󠁧󠁿󠁧󠁢󠁥󠁮󠁧󠁿EnglishENG
The future prime meridian based at the Royal Observatory, Greenwich, in London, England, was established by Sir George Airy in 1851.

George Biddell Airy

George AiryAirySir George Biddell Airy
The future prime meridian based at the Royal Observatory, Greenwich, in London, England, was established by Sir George Airy in 1851. The plane of the prime meridian is parallel to the local gravity vector at the Airy transit circle (51.47781°N, -0.00147°W) of the Greenwich observatory.

Tonnage

tonstonGRT
By 1884, over two-thirds of all ships and tonnage used it as the reference meridian on their charts and maps.

Nautical chart

chartschartnautical charts
By 1884, over two-thirds of all ships and tonnage used it as the reference meridian on their charts and maps.

President of the United States

PresidentU.S. PresidentUnited States President
In October of that year, at the behest of US President Chester A. Arthur, 41 delegates from 25 nations met in Washington, D.C., United States, for the International Meridian Conference.

Chester A. Arthur

Chester ArthurArthurChester Alan Arthur
In October of that year, at the behest of US President Chester A. Arthur, 41 delegates from 25 nations met in Washington, D.C., United States, for the International Meridian Conference.

Washington, D.C.

Washington, DCWashington D.C.District of Columbia
In October of that year, at the behest of US President Chester A. Arthur, 41 delegates from 25 nations met in Washington, D.C., United States, for the International Meridian Conference.

Malachy Postlethwayt

Postlewayta London commercial expertMalachy Postlewayt
In the 18th century, London lexicographer Malachy Postlethwayt published his African maps showing the "Meridian of London" intersecting the Equator a few degrees west of the later meridian and Accra, Ghana.

Equator

equatorial planeThe Equator
In the 18th century, London lexicographer Malachy Postlethwayt published his African maps showing the "Meridian of London" intersecting the Equator a few degrees west of the later meridian and Accra, Ghana.

Accra

Accra, GhanaAccra Metropolitan AreaAccra, Gold Coast
In the 18th century, London lexicographer Malachy Postlethwayt published his African maps showing the "Meridian of London" intersecting the Equator a few degrees west of the later meridian and Accra, Ghana.

Ghana

GhanaianRepublic of GhanaGHA
In the 18th century, London lexicographer Malachy Postlethwayt published his African maps showing the "Meridian of London" intersecting the Equator a few degrees west of the later meridian and Accra, Ghana.

Meridian circle

transit circlemural circletransit
The plane of the prime meridian is parallel to the local gravity vector at the Airy transit circle (51.47781°N, -0.00147°W) of the Greenwich observatory.

Laser

laserslaser beamlaser light
The prime meridian was therefore long symbolised by a brass strip in the courtyard, now replaced by stainless steel, and since 16 December 1999, it has been marked by a powerful green laser shining north across the London night sky.

International Time Bureau

Bureau International de l'Heure
In the past, this offset has been attributed to the establishment of reference meridians for space-based location systems such as WGS 84 (which GPS relies on) or that errors gradually crept into the International Time Bureau timekeeping process.