's 1st projection, redrawn under
Maximus Planudes around 1300, using a prime meridian through the
Canary Islands west of Africa, at the left-hand edge of the map (The obvious central line shown here is the junction of two sheets.) The notion of longitude for Greeks was developed by the
Greek Eratosthenes (c.276195BCE) in
Alexandria, and
Hipparchus (c.190120BCE) in
Rhodes, and applied to a large number of cities by the
geographer Strabo (64/63BCEc.24CE).
Ptolemy (c.90168CE) was the first geographer to use 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°W to 18°W), although his maps correspond more closely to the
Cape Verde islands (22°W to 25°W). The main point is to be comfortably west of the western tip of
Africa (17°30′W) as negative numbers were not yet in use. His prime meridian corresponds to 18°40′ west of
Winchester (about 20°W) today. At that time the chief method of determining longitude was by using the reported times of
lunar eclipses in different countries. 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 in Central India, and
Rohitaka, the ancient name for
Rohtak (), a city north. 's facsimile of the 1529
Spanish Padron Real, from the copy made by
Diogo Ribeiro and held by 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. In 1493,
Christopher Columbus reported 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 (about ) west of
Cape Verde. This is shown in the copies of Spain's
Padron Real made by
Diogo Ribeiro in 1527 and 1529.
São Miguel Island (25°30′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 declination line did not follow a line of longitude. , with
Cape Verde marking its prime meridian , with Cape Verde originating its prime meridian;
Japan is thus located around 180° E. In 1541,
Mercator produced his 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. In 1634,
Cardinal Richelieu used the westernmost island of the Canaries,
El Hierro, 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. 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. 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, enabled navigators to use the
lunar method of determining longitude more accurately using the
octant developed by
Thomas Godfrey and
John Hadley. 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
Prussia 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." In 1884, at the
International Meridian Conference in
Washington, D.C., 22 countries voted to adopt the Greenwich 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. The current international standard Prime Meridian is the
IERS Reference Meridian. The
International Hydrographic Organization adopted an early version of the IRM in 1983 for all nautical charts. It was adopted for air navigation by the
International Civil Aviation Organization on 3 March 1989. ==International prime meridian==