Prime meridian

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Prime Meridian

A prime meridian is the meridian (a line of longitude) in a geographic coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its anti-meridian (the 180th meridian in a 360°-system) form a great circle. This great circle divides a spheroid into two hemispheres. If one uses directions of East and West from a defined prime meridian, then they can be called the Eastern Hemisphere and the Western Hemisphere.

Contents

Gerardus Mercator in his Atlas Cosmographicae (1595) used a prime meridian somewhere close to 25degW, passing just to the west of Santa Maria Island in the Azores in the Atlantic Ocean. His 180th meridian runs along the Strait of Anian (Bering Strait) Atlas Cosmographicae (Mercator) 033.jpg
Gerardus Mercator in his Atlas Cosmographicae (1595) used a prime meridian somewhere close to 25°W, passing just to the west of Santa Maria Island in the Azores in the Atlantic Ocean. His 180th meridian runs along the Strait of Anián (Bering Strait)

A prime meridian for a body not tidally locked (or at least not synchronous) is ultimately arbitrary, unlike an equator, which is determined by the axis of rotation. For celestial objects that are tidally locked (more specifically, synchronous), however, their prime meridians are determined by the face always inward of the orbit (a planet facing its star, or a moon facing its planet), just as equators are determined by rotation. For Earth's prime meridian, various conventions have been used or advocated in different regions throughout history. [1] The most widely used modern meridian is the IERS Reference Meridian. It is derived but deviates slightly from the Greenwich Meridian, which was selected as an international standard in 1884.

Longitudes for the Earth and Moon are measured from their prime meridian at 0° to 180° east and to 180° west. For all other Solar System bodies, longitude is measured from 0° (their prime meridian) to 360°. West longitudes are used if the rotation of the body is direct, that is, it follows the right hand rule. East longitudes are used if the rotation is retrograde. [2] However, °E that are greater than 180 can be converted to °W by subtracting the value from 360. The same is true of °W greater than 180, converting to °E.

History

Ptolemy's 1st projection, redrawn under Maximus Planudes around 1300, using a prime meridian through the Canary Islands west of Africa. (The obvious central line is the junction of two sheets). Ptolemy-World Vat Urb 82.jpg
Ptolemy's 1st projection, redrawn under Maximus Planudes around 1300, using a prime meridian through the Canary Islands west of Africa. (The obvious central line is the junction of two sheets).

One of the earliest known descriptions of standard time in India appeared in the 4th century CE astronomical treatise Surya Siddhanta. Postulating a spherical earth, the book described the thousands years old customs of the prime meridian, or zero longitude, as passing through Avanti , the ancient name for the historic city of Ujjain, and Rohitaka, the ancient name for Rohtak ( 28°54′N76°38′E / 28.900°N 76.633°E / 28.900; 76.633 (Rohitaka (Rohtak)) ), a city near the Kurukshetra. [3]

The notion of longitude for Greeks was developed by the Greek Eratosthenes (c. 276 BC – c. 195 BC) in Alexandria, and Hipparchus (c. 190 BC – c. 120 BC) in Rhodes, and applied to a large number of cities by the geographer Strabo (64/63 BC – c. 24 AD). But it was Ptolemy (c. AD 90 – c. AD 168) who first used a consistent meridian for a world map in his Geographia .

Ptolemy used as his basis the "Fortunate Isles", a group of islands in the Atlantic, which are usually associated with the Canary Islands (13° to 18°W), although his maps correspond more closely to the Cape Verde islands (22° to 25° W). The main point is to be comfortably west of the western tip of Africa (17.5° W) as negative numbers were not yet in use. His prime meridian corresponds to 18° 40' west of Winchester (about 20°W) today. [4] At that time the chief method of determining longitude was by using the reported times of lunar eclipses in different countries.

Facsimile of Diego Ribeiro's map of 1529; the original is in the Vatican Library. Map Diego Ribero 1529.jpg
Facsimile of Diego Ribeiro's map of 1529; the original is in the Vatican Library.

Ptolemy's Geographia was first printed with maps at Bologna in 1477, and many early globes in the 16th century followed his lead. But there was still a hope that a "natural" basis for a prime meridian existed. Christopher Columbus reported (1493) that the compass pointed due north somewhere in mid-Atlantic, and this fact was used in the important Treaty of Tordesillas of 1494, which settled the territorial dispute between Spain and Portugal over newly discovered lands. The Tordesillas line was eventually settled at 370 leagues (2,193 kilometers, 1,362 statute miles, or 1,184 nautical miles) [note 1] west of Cape Verde. This is shown in Diogo Ribeiro's 1529 map. São Miguel Island (25.5°W) in the Azores was still used for the same reason as late as 1594 by Christopher Saxton, although by then it had been shown that the zero magnetic deviation line did not follow a line of longitude. [9]

1571 Africa map by Abraham Ortelius, with Cape Verde as its prime meridian. Atlas Ortelius KB PPN369376781-006av-006br.jpg
1571 Africa map by Abraham Ortelius, with Cape Verde as its prime meridian.
1682 map of East Asia by Giacomo Cantelli, with Cape Verde as its prime meridian; Japan is thus located around 180deg E. CEM-36-Regno-della-China-2355.jpg
1682 map of East Asia by Giacomo Cantelli, with Cape Verde as its prime meridian; Japan is thus located around 180° E.

In 1541, Mercator produced his famous 41 cm terrestrial globe and drew his prime meridian precisely through Fuerteventura (14°1'W) in the Canaries. His later maps used the Azores, following the magnetic hypothesis. But by the time that Ortelius produced the first modern atlas in 1570, other islands such as Cape Verde were coming into use. In his atlas longitudes were counted from 0° to 360°, not 180°W to 180°E as is usual today. This practice was followed by navigators well into the 18th century. [10] In 1634, Cardinal Richelieu used the westernmost island of the Canaries, Ferro, 19° 55' west of Paris, as the choice of meridian. The geographer Delisle decided to round this off to 20°, so that it simply became the meridian of Paris disguised. [11]

In the early 18th century the battle was on to improve the determination of longitude at sea, leading to the development of the marine chronometer by John Harrison. But it was the development of accurate star charts, principally by the first British Astronomer Royal, John Flamsteed between 1680 and 1719 and disseminated by his successor Edmund Halley, that enabled navigators to use the lunar method of determining longitude more accurately using the octant developed by Thomas Godfrey and John Hadley. [12]

In the 18th century most countries in Europe adapted their own prime meridian, usually through their capital, hence in France the Paris meridian was prime, in Germany it was the Berlin meridian, in Denmark the Copenhagen meridian, and in United Kingdom the Greenwich meridian.

Between 1765 and 1811, Nevil Maskelyne published 49 issues of the Nautical Almanac based on the meridian of the Royal Observatory, Greenwich. "Maskelyne's tables not only made the lunar method practicable, they also made the Greenwich meridian the universal reference point. Even the French translations of the Nautical Almanac retained Maskelyne's calculations from Greenwich – in spite of the fact that every other table in the Connaissance des Temps considered the Paris meridian as the prime." [13]

In 1884, at the International Meridian Conference in Washington, D.C., 22 countries voted to adopt the Greenwich [14] meridian as the prime meridian of the world. The French argued for a neutral line, mentioning the Azores and the Bering Strait, but eventually abstained and continued to use the Paris meridian until 1911.

List of prime meridians on Earth

LocalityModern longitudeMeridian nameImageComment
Bering Strait 168°30' W
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168°
168th meridian west
Offered in 1884 as possibility for a neutral prime meridian by Pierre Janssen at the International Meridian Conference [15]
Washington, D.C. 77°03′56.07″ W (1897) or 77°04′02.24″ W (NAD 27)[ clarification needed ] or 77°04′01.16″ W (NAD 83) New Naval Observatory meridian
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77°
77th meridian west
Washington, D.C.77°02′48.0″ W, 77°03′02.3″, 77°03′06.119″ W or 77°03′06.276″ W (both presumably NAD 27). If NAD27, the latter would be 77°03′05.194″ W (NAD 83) Old Naval Observatory meridian
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77°
77th meridian west
Washington, D.C.77°02′11.56299″ W (NAD 83), [16] 77°02′11.55811″ W (NAD 83), [17] 77°02′11.58325″ W (NAD 83) [18] (three different monuments originally intended to be on the White House meridian) White House meridian
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77°
77th meridian west
Washington, D.C.77°00′32.6″ W (NAD 83) Capitol meridian
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77°
77th meridian west
Philadelphia 75° 10' 12″ W
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75°
75th meridian west
[19] [20]
Rio de Janeiro 43° 10' 19″ W
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43°
43rd meridian west
[21]
Fortunate Isles / Azores25° 40' 32″ W
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32°
32nd meridian west
Used until the Middle Ages, proposed as one possible neutral meridian by Pierre Janssen at the International Meridian Conference [22]
El Hierro (Ferro),
Canary Islands
18° 03' W,
later redefined as
17° 39' 46″ W
Ferro meridian
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18°
18th meridian west
[23]
Tenerife 16° 38' 22" W Tenerife meridian
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16°
16th meridian west
Rose to prominence with Dutch cartographers and navigators after they abandoned the idea of a magnetic meridian [24]
Cadiz 6° 17' 35.4" WCadiz meridian
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6th meridian west
Royal Observatory in southeast tower of Castillo de la Villa, used 1735–1850 by Spanish Navy. [25] [26]
Lisbon 9° 07' 54.862″ W
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9th meridian west
[27]
Madrid 3° 41' 16.58″ W
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3rd meridian west
[27]
Kew 0° 00' 19.0″ WPrime Meridian (prior to Greenwich)
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Prime Meridian
Located at King George III's Kew Observatory
Greenwich 0° 00' 05.3101″ W Greenwich meridian
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Prime Meridian
Airy Meridian [28]
Greenwich0° 00' 05.33″ W United Kingdom Ordnance Survey Zero Meridian
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Prime Meridian
Bradley Meridian [28]
Greenwich0° 00' 00.00″ IERS Reference Meridian
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Prime Meridian
Paris 2° 20' 14.025″ E Paris meridian
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2nd meridian east
Brussels 4° 22' 4.71″ E
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4th meridian east
[27]
Antwerp 4° 24' E Antwerp meridian
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4th meridian east
Amsterdam 4° 53' E
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4th meridian east
Through the Westerkerk in Amsterdam; used to define the legal time in the Netherlands from 1909 to 1937 [29]
Pisa 10° 24' E
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10°
10th meridian east
[19]
Oslo (Kristiania) 10° 43' 22.5″ E
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10°
10th meridian east
[19] [20]
Florence 11°15' E Florence meridian
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11°
11th meridian east
Used in the Peters projection, 180° from a meridian running through the Bering Strait
Rome 12° 27' 08.4″ EMeridian of Monte Mario
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12°
12th meridian east
Used in Roma 40 Datum [30]
Copenhagen 12° 34' 32.25″ E
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12°
12th meridian east
Rundetårn [31]
Naples 14° 15' E
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14°
14th meridian east
[22]
Pressburg 17° 06' 03″ EMeridianus Posoniensis
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17°
17th meridian east
Used by Sámuel Mikoviny
Buda 19° 03' 37″ EMeridianu(s) Budense
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19°
19th meridian east
Used between 1469 and 1495; introduced by Regiomontanus, used by Marcin Bylica, Galeotto Marzio, Miklós Erdélyi (1423–1473), Johannes Tolhopff (c. 1445–1503), Johannes Muntz. Set in the royal castle (and observatory) of Buda. [32]
Stockholm 18° 03' 29.8″ E
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18°
18th meridian east
At the Stockholm Observatory [27]
Kraków 19° 57' 21.43″ EKraków meridian
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19°
19th meridian east
at the Old Kraków Observatory at the Śniadecki' College; mentioned also in Nicolaus Copernicus's work On the Revolutions of the Heavenly Spheres.
Warsaw 21° 00' 42″ E Warsaw meridian
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21°
21st meridian east
[27]
Várad 21° 55' 16″ ETabulae Varadienses
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21°
21st meridian east
[33] Between 1464 and 1667, a prime meridian was set in the Fortress of Oradea (Varadinum at the time) by Georg von Peuerbach. [34] In his logbook Columbus stated, he had one copy of Tabulae Varadienses (Tabula Varadiensis or Tabulae directionum) on board to calculate the actual meridian based on the position of the Moon, in correlation to Várad. Amerigo Vespucci also recalled, how was he acquired the knowledge to calculate meridians by means of these tables. [35]
Alexandria 29° 53' EMeridian of Alexandria
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29°
29th meridian east
The meridian of Ptolemy's Almagest.
Saint Petersburg 30° 19' 42.09″ E Pulkovo meridian
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30°
30th meridian east
Great Pyramid of Giza 31° 08' 03.69″ E
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31°
31st meridian east
1884 [36]
Jerusalem 35° 13' 47.1″ E
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35°
35th meridian east
[20]
Mecca 39° 49' 34″ E
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39°
39th meridian east
See also Mecca Time [37]
Ujjain 75° 47' E
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75°
75th meridian east
Used from 4th century CE Indian astronomy and calendars(see also Time in India). [38]
Kyoto 136° 14' E
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136°
136th meridian east
Used in 18th and 19th (officially 1779–1871) century Japanese maps. Exact place unknown, but in "Kairekisyo" in Nishigekkoutyou-town in Kyoto, then the capital.[ citation needed ]
~ 180
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180°
180th meridian
Opposite of Greenwich, proposed 13 October 1884 on the International Meridian Conference by Sandford Fleming [22]

International prime meridian

In October 1884 the Greenwich Meridian was selected by delegates (forty-one delegates representing twenty-five nations) to the International Meridian Conference held in Washington, D.C., United States to be the common zero of longitude and standard of time reckoning throughout the world. [39] [note 2] The modern prime meridian, the IERS Reference Meridian, is placed very near this meridian and is the prime meridian that currently has the widest use.

Prime meridian at Greenwich

Markings of the prime meridian at the Royal Observatory, Greenwich. Prime meridian.jpg
Markings of the prime meridian at the Royal Observatory, Greenwich.

The modern prime meridian, based at the Royal Observatory, Greenwich, was established by Sir George Airy in 1851. [41]

The position of the Greenwich Meridian has been defined by the location of the Airy Transit Circle ever since the first observation was taken with it by Sir George Airy in 1851. [41] Prior to that, it was defined by a succession of earlier transit instruments, the first of which was acquired by the second Astronomer Royal, Edmond Halley in 1721. It was set up in the extreme north-west corner of the Observatory between Flamsteed House and the Western Summer House. This spot, now subsumed into Flamsteed House, is roughly 43 metres to the west of the Airy Transit Circle, a distance equivalent to roughly 2 seconds of longitude. [28] It was Airy's transit circle that was adopted in principle (with French delegates, who pressed for adoption of the Paris meridian abstaining) as the Prime Meridian of the world at the 1884 International Meridian Conference. [42] [43]

All of these Greenwich meridians were located via an astronomic observation from the surface of the Earth, oriented via a plumb line along the direction of gravity at the surface. This astronomic Greenwich meridian was disseminated around the world, first via the lunar distance method, then by chronometers carried on ships, then via telegraph lines carried by submarine communications cables, then via radio time signals. One remote longitude ultimately based on the Greenwich meridian using these methods was that of the North American Datum 1927 or NAD27, an ellipsoid whose surface best matches mean sea level under the United States.

IERS Reference Meridian

Beginning in 1973 the International Time Bureau and later the International Earth Rotation and Reference Systems Service changed from reliance on optical instruments like the Airy Transit Circle to techniques such as lunar laser ranging, satellite laser ranging, and very-long-baseline interferometry. The new techniques resulted in the IERS Reference Meridian, the plane of which passes through the centre of mass of the Earth. This differs from the plane established by the Airy transit, which is affected by vertical deflection (the local vertical is affected by influences such as nearby mountains). The change from relying on the local vertical to using a meridian based on the centre of the Earth caused the modern prime meridian to be 5.3 east of the astronomic Greenwich prime meridian through the Airy Transit Circle. At the latitude of Greenwich, this amounts to 102 metres. [44] This was officially accepted by the Bureau International de l'Heure (BIH) in 1984 via its BTS84 (BIH Terrestrial System) that later became WGS84 (World Geodetic System 1984) and the various ITRFs (International Terrestrial Reference Systems).

Due to the movement of Earth's tectonic plates, the line of 0° longitude along the surface of the Earth has slowly moved toward the west from this shifted position by a few centimetres; that is, towards the Airy Transit Circle (or the Airy Transit Circle has moved toward the east, depending on your point of view) since 1984 (or the 1960s). With the introduction of satellite technology, it became possible to create a more accurate and detailed global map. With these advances there also arose the necessity to define a reference meridian that, whilst being derived from the Airy Transit Circle, would also take into account the effects of plate movement and variations in the way that the Earth was spinning. [45] As a result, the International Reference Meridian was established and is commonly used to denote Earth's prime meridian (0° longitude) by the International Earth Rotation and Reference Systems Service, which defines and maintains the link between longitude and time. Based on observations to satellites and celestial compact radio sources (quasars) from various coordinated stations around the globe, Airy's transit circle drifts northeast about 2.5 centimetres per year relative to this Earth-centred 0° longitude.

It is also the reference meridian of the Global Positioning System operated by the United States Department of Defense, and of WGS84 and its two formal versions, the ideal International Terrestrial Reference System (ITRS) and its realization, the International Terrestrial Reference Frame (ITRF). [46] [47] [48] A current convention on the Earth uses the opposite of the IRM as the basis for the International Date Line.

List of places

Map all coordinates using: OpenStreetMap  
Download coordinates as: KML

On Earth, starting at the North Pole and heading south to the South Pole, the IERS Reference Meridian (as of 2016) passes through:

Co-ordinates
(approximate)
Country, territory or seaNotes
90°0′N0°0′E / 90.000°N 0.000°E / 90.000; 0.000 (North Pole) Arctic Ocean
85°46′N0°0′E / 85.767°N 0.000°E / 85.767; 0.000 (EEZ of Greenland (Denmark)) Exclusive Economic Zone (EEZ) of Greenland (Denmark)
81°39′N0°0′E / 81.650°N 0.000°E / 81.650; 0.000 (Greenland Sea) Greenland Sea
80°29′N0°0′E / 80.483°N 0.000°E / 80.483; 0.000 (EEZ of Svalbard (Norway)) EEZ of Svalbard (Norway)
76°11′N0°0′E / 76.183°N 0.000°E / 76.183; 0.000 (International waters) International waters
73°44′N0°0′E / 73.733°N 0.000°E / 73.733; 0.000 (EEZ of Jan Mayen) EEZ of Jan Mayen (Norway)
72°53′N0°0′E / 72.883°N 0.000°E / 72.883; 0.000 (Norwegian Sea) Norwegian Sea
69°7′N0°0′E / 69.117°N 0.000°E / 69.117; 0.000 (International waters) International waters
64°42′N0°0′E / 64.700°N 0.000°E / 64.700; 0.000 (EEZ of Norway) EEZ of Norway
63°29′N0°0′E / 63.483°N 0.000°E / 63.483; 0.000 (EEZ of Great Britain) EEZ of Great Britain
61°0′N0°0′E / 61.000°N 0.000°E / 61.000; 0.000 (North Sea) North Sea
53°46′N0°0′E / 53.767°N 0.000°E / 53.767; 0.000 (United Kingdom) Flag of the United Kingdom.svg  United Kingdom From Tunstall in East Riding to Peacehaven, passing through Greenwich
50°47′N0°0′E / 50.783°N 0.000°E / 50.783; 0.000 (English Channel) English Channel EEZ of Great Britain
50°14′N0°0′E / 50.233°N 0.000°E / 50.233; 0.000 (EEZ of France) English Channel EEZ of France
49°20′N0°0′E / 49.333°N 0.000°E / 49.333; 0.000 (France) Flag of France.svg  France From Villers-sur-Mer to Gavarnie
42°41′N0°0′E / 42.683°N 0.000°E / 42.683; 0.000 (Spain) Flag of Spain.svg  Spain From Cilindro de Marboré to Castellón de la Plana
39°56′N0°0′E / 39.933°N 0.000°E / 39.933; 0.000 (Mediterranean Sea) Mediterranean Sea Gulf of Valencia; EEZ of Spain
38°52′N0°0′E / 38.867°N 0.000°E / 38.867; 0.000 (Spain) Flag of Spain.svg  Spain From El Verger to Calp
38°38′N0°0′E / 38.633°N 0.000°E / 38.633; 0.000 (Mediterranean Sea) Mediterranean Sea EEZ of Spain
37°1′N0°0′E / 37.017°N 0.000°E / 37.017; 0.000 (EEZ of Algeria) Mediterranean Sea EEZ of Algeria
35°50′N0°0′E / 35.833°N 0.000°E / 35.833; 0.000 (Algeria) Flag of Algeria.svg  Algeria From Stidia to Algeria-Mali border near Bordj Badji Mokhtar
21°52′N0°0′E / 21.867°N 0.000°E / 21.867; 0.000 (Mali) Flag of Mali.svg  Mali Passing through Gao
15°00′N0°0′E / 15.000°N 0.000°E / 15.000; 0.000 (Burkina Faso) Flag of Burkina Faso.svg  Burkina Faso
11°7′N0°0′E / 11.117°N 0.000°E / 11.117; 0.000 (Togo) Flag of Togo.svg  Togo For about 600 m
11°6′N0°0′E / 11.100°N 0.000°E / 11.100; 0.000 (Ghana) Flag of Ghana.svg  Ghana For about 16 km
10°58′N0°0′E / 10.967°N 0.000°E / 10.967; 0.000 (Togo) Flag of Togo.svg  Togo For about 39 km
10°37′N0°0′E / 10.617°N 0.000°E / 10.617; 0.000 (Ghana) Flag of Ghana.svg  Ghana From the Togo-Ghana border near Bunkpurugu to Tema
Passing through Lake Volta at 7°46′N0°0′E / 7.767°N 0.000°E / 7.767; 0.000 (Lake Volta)
5°37′N0°0′E / 5.617°N 0.000°E / 5.617; 0.000 (EEZ of Ghana in Atlantic Ocean) Atlantic Ocean EEZ of Ghana
1°58′N0°0′E / 1.967°N 0.000°E / 1.967; 0.000 (International waters) International waters
0°0′N0°0′E / 0.000°N 0.000°E / 0.000; 0.000 (Equator) Passing through the Equator (see Null Island)
51°43′S0°0′E / 51.717°S 0.000°E / -51.717; 0.000 (EEZ of Bouvet Island) EEZ of Bouvet Island (Norway)
57°13′S0°0′E / 57.217°S 0.000°E / -57.217; 0.000 (International waters) International waters
60°0′S0°0′E / 60.000°S 0.000°E / -60.000; 0.000 (Southern Ocean) Southern Ocean International waters
69°36′S0°0′E / 69.600°S 0.000°E / -69.600; 0.000 (Antarctica) Antarctica Queen Maud Land, claimed by Flag of Norway.svg  Norway
90°0′S0°0′E / 90.000°S 0.000°E / -90.000; 0.000 (Amundsen–Scott South Pole Station) Antarctica Amundsen–Scott South Pole Station, South Pole

Prime meridian on other planetary bodies

As on the Earth, prime meridians must be arbitrarily defined. Often a landmark such as a crater is used; other times a prime meridian is defined by reference to another celestial object, or by magnetic fields. The prime meridians of the following planetographic systems have been defined:

See also

Notes

  1. These figures use the legua náutica (nautical league) of four Roman miles totaling 5.926 km, which was used by Spain during the 15th, 16th, and 17th centuries for navigation. [5] In 1897 Henry Harrise noted that Jaime Ferrer, the expert consulted by King Ferdinand and Queen Isabella, stated that a league was four miles of six stades each. [6] Modern scholars agree that the geographic stade was the Roman or Italian stade, not any of several other Greek stades, supporting these figures. [7] [8] Harrise is in the minority when he uses the stade of 192.27 m marked within the stadium at Olympia, Greece, resulting in a league (32 stades) of 6.153 km, 3.8% larger.
  2. Voting took place on 13 October and the resolutions were adopted on 22 October 1884. [40]

Citations

  1. Prime Meridian, geog.port.ac.uk
  2. Archimal, B. A. (2015), Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2015 (PDF), p. 27 of 46, The range of longitudes shall extend from 0° to 360°. Thus, west longitudes are used when the rotation is direct, and east longitudes are used when the rotation is retrograde. ... The Earth, Sun, and Moon do not traditionally follow this definition. Their rotations are direct and longitudes run both east and west 180°, or positive to the east 360°.
  3. Schmidt, Olaf H. (1944). "The Computation of the Length of Daylight in Hindu Astronomy". Isis, 35(3):205–211. The University of Chicago Press. JSTOR   330729.
  4. Norgate & Norgate 2006
  5. Chardon, Roland (1980). "The linear league in North America". Annals of the Association of American Geographers. 70 (2): 129–153 [pp. 142, 144, 151]. doi:10.1111/j.1467-8306.1980.tb01304.x. JSTOR   2562946.
  6. Henry Harrisse, The Diplomatic History of America: Its first chapter 1452—1493—1494 (London: Stevens, 1897). pp. 85–97, 176–190.
  7. Newlyn Walkup, Eratosthenes and the mystery of the stades
  8. Engels, Donald (1985). "The length of Eratosthenes' stade". American Journal of Philology . 106 (3): 298–311. doi:10.2307/295030. JSTOR   295030.
  9. Hooker 2006
  10. e.g. Jacob Roggeveen in 1722 reported the longitude of Easter Island as 268° 45' (starting from Fuerteventura) in the Extract from the Official log of Jacob Roggeveen reproduced in Bolton Glanville Corney, ed. (1908), The voyage of Don Felipe Gonzalez to Easter Island in 1770-1, Hakluyt Society, p. 3, retrieved 13 January 2013
  11. Speech by Pierre Janssen, director of the Paris observatory, at the first session of the Meridian Conference.
  12. Sobel & Andrewes 1998 , pp. 110–115
  13. Sobel & Andrewes 1998 , pp. 197–199
  14. "The Prime Meridian at Greenwich". Royal Museums Greenwich. n.d. Retrieved 28 March 2016.
  15. International Conference Held at Washington for the Purpose of Fixing a Prime Meridian and a Universal Day. October, 1884, pp. 4351. Project Gutenberg
  16. NGS 2016, PID: HV1847.
  17. NGS 2016, PID: HV1846.
  18. NGS 2016, PID: AH7372.
  19. 1 2 3 Hooker (2006), introduction.
  20. 1 2 3 Oct. 13, 1884: Greenwich Resolves Subprime Meridian Crisis, WIRED, 13 October 2010.
  21. Atlas do Brazil, 1909, by Barão Homem de Mello e Francisco Homem de Mello, published in Rio de Janeiro by F. Briguiet & Cia.
  22. 1 2 3 "The Project Gutenberg eBook of International Conference Held at Washington for the Purpose of Fixing a Prime Meridian and a Universal Day". Gutenberg.org. 12 February 2006. Retrieved 28 March 2016.
  23. Ancient, used in Ptolemy's Geographia . Later redefined 17° 39' 46″ W of Greenwich to be exactly 20° W of Paris. French "submarin" at Washington 1884.
  24. A.R.T. Jonkers; Parallel meridians: Diffusion and change in early modern oceanic reckoning, in Noord-Zuid in Oostindisch perspectief, The Hague, 2005, p. 7. Retrieved 2 February 2015.
  25. "In search of the lost meridian of Cadiz", El País, 23 December 2016. Retrieved 8 November 2018.
  26. Antonio Lafuente and Manuel Sellés, El Observatorio de Cádiz (1753–1831), Ministerio de Defensa, 1988, p.144, ISBN   84-505-7563-X. (in Spanish)
  27. 1 2 3 4 5 Bartky, Ian R. (2007). One Time Fits All: The Campaigns for Global Uniformity. Stanford University Press. p. 98. ISBN   978-0-8047-5642-6.
  28. 1 2 3 Dolan 2013a.
  29. (in Dutch) Eenheid van tijd in Nederland (Unity of time in the Netherlands), Utrecht University website, retrieved 28 August 2013.
  30. Grids & Datums – Italian Republic, asprs.org, Retrieved 10 December 2013.
  31. meridian , article from Den Store Danske Encyklopædi
  32. When Tolhopff handed over his book, titled Stellarium (1480) to king Matthias Corvinus, he emphasized that he had used the meridian of Buda for his calculations. The German physician, Johannes Müntz used it the same way in his 1495 calendar. However, in the second edition, he had already introduced the Vienna meridian. Zsoldos, Endre – Zsupán, Edina: Stellarium – egy csillagászati kódex Mátyás könyvtárában. Orpheus Noster V. évf. 2013/4. 62–85.; Szathmáry, László: Az asztrológia, alkémia és misztika Mátyás király udvarában. In: Ponticulus Hungaricus, VI. évfolyam 5. szám · 2002.
  33. Oradea, Tourism office website, retrieved 3 February 2015.
  34. "Romanian astronaut makrsk 10th anniversary of Prime Meridian Astronomy Club". NineO'Clock.ro. 2015. Retrieved 26 June 2017.
  35. Meridian Zero csillagászklub access-date = 27 December 2018
  36. Wilcomb E. Washburn, "The Canary Islands and the Question of the Prime Meridian: The Search for Precision in the Measurement of the Earth Archived 29 May 2007 at the Wayback Machine "
  37. Maimonides, Hilchot Kiddush Hachodesh 11:17, calls this point אמצע היישוב, "the middle of the habitation", i.e. the habitable hemisphere. Evidently this was a convention accepted by Arab geographers of his day.
  38. Burgess 1860
  39. International Conference Held at Washington for the Purpose of Fixing a Prime Meridian and a Universal Day. October, 1884. Protocols of the proceedings. Project Gutenberg. 1884. Retrieved 30 November 2012.
  40. Howse 1997, pp. 12, 137
  41. 1 2 Greenwich Observatory ... the story of Britain's oldest scientific institution, the Royal Observatory at Greenwich and Herstmonceux, 1675–1975 p.10. Taylor & Francis, 1975
  42. McCarthy, Dennis; Seidelmann, P. Kenneth (2009). TIME from Earth Rotation to Atomic Physics. Weinheim: Wiley-VCH. pp. 244–5.
  43. ROG Learning Team (23 August 2002). "The Prime Meridian at Greenwich". Royal Museums Greenwich. Royal Museums Greenwich. Retrieved 14 June 2012.
  44. Malys, Stephen; Seago, John H.; Palvis, Nikolaos K.; Seidelmann, P. Kenneth; Kaplan, George H. (1 August 2015). "Why the Greenwich meridian moved". Journal of Geodesy. 89 (12): 1263. Bibcode:2015JGeod..89.1263M. doi: 10.1007/s00190-015-0844-y .
  45. Dolan 2013b.
  46. History of the Prime Meridian -Past and Present
  47. IRM on grounds of Royal Observatory from Google Earth Accessed 30 March 2012
  48. The astronomic latitude of the Royal Observatory is 51°28'38"N whereas its latitude on the European Terrestrial Reference Frame (1989) datum is 51°28'40.1247"N.
  49. "Carrington heliographic coordinates".
  50. Merton E. Davies, "Surface Coordinates and Cartography of Mercury," Journal of Geophysical Research, Vol. 80, No. 17, 10 June 1975
  51. Merton E. Davies, S. E. Dwornik, D. E. Gault, and R. G. Strom, NASA Atlas of Mercury, NASA Scientific and Technical Information Office, 1978.
  52. Archinal, Brent A.; A'Hearn, Michael F.; Bowell, Edward G.; Conrad, Albert R.; Consolmagno, Guy J.; et al. (2010). "Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009" (PDF). Celestial Mechanics and Dynamical Astronomy. 109 (2): 101–135. Bibcode:2011CeMDA.109..101A. doi:10.1007/s10569-010-9320-4. Archived from the original (PDF) on 4 March 2016. Retrieved 26 September 2018.
  53. Merton E. Davies; Colvin, T. R.; Rogers, P. G.; Chodas, P. G.; Sjogren, W. L. ; Akim, W. L.; Stepanyantz, E. L.; Vlasova, Z. P.; and Zakharov, A. I.; "The Rotation Period, Direction of the North Pole, and Geodetic Control Network of Venus", Journal of Geophysical Research, vol. 97, no. 8, 1992, pp. 1–14, 151
  54. "USGS Astrogeology: Rotation and pole position for the Sun and planets (IAU WGCCRE)". Archived from the original on 24 October 2011. Retrieved 22 October 2009.
  55. Merton E. Davies, and Berg, R. A.; "Preliminary Control Net of Mars", Journal of Geophysical Research, vol. 76, no. 2, 10 January 1971, pp. 373–393
  56. Archinal, Brent A.; Acton, C. H.; A’Hearn, Michael F.; Conrad, Albert R.; et al. (2018), "Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2015", Celestial Mechanics and Dynamical Astronomy, 130 (22): 22, Bibcode:2018CeMDA.130...22A, doi:10.1007/s10569-017-9805-5
  57. "Planetographic Coordinates" . Retrieved 24 May 2017.
  58. Merton E. Davies, Thomas A. Hauge, et al.: Control Networks for the Galilean Satellites: November 1979 R-2532-JPL/NASA
  59. Merton E. Davies, P. G. Rogers, and T. R. Colvin, "A Control Network of Triton," Journal of Geophysical Research, Vo l. 96, E l , pp. 15,675-15,681, 1991.

Works cited

Related Research Articles

Greenwich Mean Time Time zone (UTC+0)

Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London, reckoned from midnight. At different times in the past, it has been calculated in different ways, including being calculated from noon; as a consequence, it cannot be used to specify a precise time unless a context is given.

Longitude geographic coordinate that specifies the east-west position of a point on the Earths surface

Longitude, is a geographic coordinate that specifies the east–west position of a point on the Earth's surface, or the surface of a celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda (λ). Meridians connect points with the same longitude. The prime meridian, which passes near the Royal Observatory, Greenwich, England, is defined as 0° longitude by convention. Positive longitudes are east of the prime meridian, and negative ones are west.

A time standard is a specification for measuring time: either the rate at which time passes; or points in time; or both. In modern times, several time specifications have been officially recognized as standards, where formerly they were matters of custom and practice. An example of a kind of time standard can be a time scale, specifying a method for measuring divisions of time. A standard for civil time can specify both time intervals and time-of-day.

Universal Time (UT) is a time standard based on Earth's rotation. There are several versions of Universal Time, which differ by up to a few seconds. The most commonly used are Coordinated Universal Time (UTC) and UT1. All of these versions of UT, except for UTC, are based on Earth's rotation relative to distant celestial objects, but with a scaling factor and other adjustments to make them closer to solar time. UTC is based on International Atomic Time, with leap seconds added to keep it within 0.9 second of UT1.

Royal Observatory, Greenwich Observatory in Greenwich, London, UK

The Royal Observatory, Greenwich is an observatory situated on a hill in Greenwich Park in east London, overlooking the River Thames to the north. 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, the precursor to today's Coordinated Universal Time (UTC). The ROG has the IAU observatory code of 000, the first in the list. ROG, the National Maritime Museum, the Queen's House and Cutty Sark are collectively designated Royal Museums Greenwich.

Geographic coordinate system Coordinate system to specify locations on Earth

A geographic coordinate system (GCS) is a coordinate system associated with positions on Earth. A GCS can give positions:

Sidereal time Timekeeping system

Sidereal time is a timekeeping system that astronomers use to locate celestial objects. Using sidereal time, it is possible to easily point a telescope to the proper coordinates in the night sky. Briefly, sidereal time is a "time scale that is based on Earth's rate of rotation measured relative to the fixed stars".

Hour angle

In astronomy and celestial navigation, the hour angle is one of the coordinates used in the equatorial coordinate system to give the direction of a point on the celestial sphere. The hour angle of a point is the angle between two planes: one containing Earth's axis and the zenith, and the other containing Earth's axis and the given point.

International Meridian Conference

The International Meridian Conference was a conference held in October 1884 in Washington, D.C., in the United States, to determine a prime meridian for international use. The conference was held at the request of U.S. President Chester A. Arthur. The subject to discuss was the choice of "a meridian to be employed as a common zero of longitude and standard of time reckoning throughout the world". It resulted in the recommendation of the Greenwich Meridian as the international standard for zero degrees longitude.

George Biddell Airy English mathematician and astronomer

Sir George Biddell Airy was an English mathematician and astronomer, and the seventh Astronomer Royal from 1835 to 1881. His many achievements include work on planetary orbits, measuring the mean density of the Earth, a method of solution of two-dimensional problems in solid mechanics and, in his role as Astronomer Royal, establishing Greenwich as the location of the prime meridian. His reputation has been tarnished by allegations that, through his inaction, Britain lost the opportunity to discover the planet Neptune.

Prime meridian (Greenwich)

The prime meridian is a geographical reference line that passes through the Royal Observatory, Greenwich, in London, England. It was first established by Sir George Airy in 1851, and by 1884, over two-thirds of all ships and tonnage used it as the reference meridian on their charts and maps. 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. This conference selected the meridian passing through Greenwich as the official prime meridian due to its popularity. However, France abstained from the vote, and French maps continued to use the Paris meridian for several decades. 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.

Airy-0

Airy-0 is a crater inside the larger Airy Crater on Mars, whose location defines the position of the prime meridian of that planet. It is about 0.5 km (0.3 mile) across and lies within the region Sinus Meridiani. The IAU Working Group on Cartographic Coordinates and Rotational Elements has now recommended setting the longitude of the Viking 1 lander as the standard. This definition maintains the position of the center of Airy-0 at 0° longitude, within the tolerance of current cartographic uncertainties.

Reference ellipsoid Ellipsoid that approximates the figure of the Earth

In geodesy, a reference ellipsoid is a mathematically defined surface that approximates the geoid, which is the truer, imperfect figure of the Earth, or other planetary body, as opposed to a perfect, smooth, and unaltered sphere, which factors in the undulations of the bodies' gravity due to variations in the composition and density of the interior, as well as the subsequent flattening caused by the centrifugal force from the rotation of these massive objects . Because of their relative simplicity, reference ellipsoids are used as a preferred surface on which geodetic network computations are performed and point coordinates such as latitude, longitude, and elevation are defined.

Meridian (geography) Line between the poles with the same longitude

A (geographic) meridian is the half of an imaginary great circle on the Earth's surface, a coordinate line terminated by the North Pole and the South Pole, connecting points of equal longitude, as measured in angular degrees east or west of the Prime Meridian. The position of a point along the meridian is given by that longitude and its latitude, measured in angular degrees north or south of the Equator. Each meridian is perpendicular to all circles of latitude. Meridians are half of a great circle on the Earth's surface. The length of a meridian on a modern ellipsoid model of the earth has been estimated at 20,003.93 km.

Eastern Hemisphere

The Eastern Hemisphere is a geographical term for the half of Earth which is east of the prime meridian and west of the antimeridian. It is also used to refer to Afro-Eurasia and Australia, in contrast with the Western Hemisphere, which includes mainly North and South America. The Eastern Hemisphere may also be called the "Oriental Hemisphere". In addition, it may be used in a cultural or geopolitical sense as a synonym for the "Old World".

Selenographic coordinates Coordinate system used on the Moon

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Meridian circle

The meridian circle is an instrument for timing of the passage of stars across the local meridian, an event known as a culmination, while at the same time measuring their angular distance from the nadir. These are special purpose telescopes mounted so as to allow pointing only in the meridian, the great circle through the north point of the horizon, the north celestial pole, the zenith, the south point of the horizon, the south celestial pole, and the nadir. Meridian telescopes rely on the rotation of the sky to bring objects into their field of view and are mounted on a fixed, horizontal, east–west axis.

25th meridian west from Washington

The 25th meridian of longitude west from Washington is a line of longitude approximately 102.05 degrees west of the Prime Meridian of Greenwich. In the United States of America, the meridian 25 degrees west of the Washington Meridian defines the eastern boundary of the State of Colorado, the western boundary of the State of Kansas, and the western boundary of the State of Nebraska south of the 41st parallel north.

The 32nd meridian of longitude west from Washington is a line of longitude approximately 109°02′48″ west of the Prime Meridian of Greenwich. In the United States of America, the meridian 32 degrees west of the Washington Meridian defines the western boundaries of the State of Colorado and the State of New Mexico and the eastern boundaries of the State of Utah and the State of Arizona.

IERS Reference Meridian International prime meridian used for GPS and other systems

The IERS Reference Meridian (IRM), also called the International Reference Meridian, is the prime meridian maintained by the International Earth Rotation and Reference Systems Service (IERS). It passes about 5.3 arcseconds east of George Biddell Airy's 1851 transit circle which is 102 metres (335 ft) at the latitude of the Royal Observatory, Greenwich. It is also the reference meridian of the Global Positioning System (GPS) operated by the United States Department of Defense, and of WGS84 and its two formal versions, the ideal International Terrestrial Reference System (ITRS) and its realization, the International Terrestrial Reference Frame (ITRF).