thumb|350px|[[Ptolemy's world map, reconstituted from Ptolemy's Geography (circa 150) in the 15th century, indicating "Sinae" (China) at the extreme right, beyond the island of "Taprobane" (Ceylon or Sri Lanka, oversized) and the "Aurea Chersonesus" (Southeast Asian peninsula)]]thumb|350px|Detail of [[East Asia|East and Southeast Asia in Ptolemy's world map. Gulf of the Ganges (Bay of Bengal) left, Southeast Asian peninsula in the center, South China Sea right, with "Sinae" (China)]]

The Ptolemy world map is a map of the world known to Greco-Roman societies in the 2nd century. It is based on the description contained in Ptolemy's book Geography, written . Based on an inscription in several of the earliest surviving manuscripts, it is traditionally credited to Agathodaemon of Alexandria.

Notable features of Ptolemy's map are the first use of longitudinal and latitudinal lines as well as specifying terrestrial locations by celestial observations. The Geography was translated from Greek into Arabic in the 9th century and played a role in the work of al-Khwārizmī before lapsing into obscurity. The idea of a global coordinate system revolutionized European geographical thought, however, and inspired more mathematical treatment of cartography.

Ptolemy's work probably originally came with maps, but none have been discovered. Instead, the present form of the map was reconstructed from Ptolemy's coordinates by Byzantine monks under the direction of Maximus Planudes shortly after 1295. It probably was not that of the original text, as it uses the less favored of the two alternate projections offered by Ptolemy.

Continents

The continents are given as Europe, Asia, and Libya (Africa). The World Ocean is only seen to the west. The map distinguishes two large enclosed seas: the Mediterranean and the Indian (Indicum Pelagus). Due to Marinus and Ptolemy's mistaken measure of the circumference of the earth, the former is made to extend much too far in terms of degrees of arc; due to their reliance on Hipparchus, they mistakenly enclose the latter with an eastern and southern shore of unknown lands, which prevents the map from identifying the western coast of the World Ocean.

India is bound by the Indus and Ganges rivers, but its peninsula is much shortened. Instead, Sri Lanka (Taprobane) is greatly enlarged. The Malay Peninsula is given as the Golden Chersonese instead of the earlier "Golden Island", which derived from Indian accounts of the mines on Sumatra. Beyond the Golden Chersonese, the Great Gulf (Magnus Sinus) forms a combination of the Gulf of Thailand and South China Sea which is bound by the unknown lands thought to enclose the Indian Sea. China is divided into two realms—the Qin (Sinae) and the Land of Silk (Serica)—owing to the different accounts received from the overland and maritime Silk Roads.

References

  • Nicholas the German's Florentine edition, the first to use Ptolemy's 2nd projection, at the University of Minnesota
  • Late Ptolemaic maps at Columbia University
  • Richard Donohue's presentation of Ptolemy's projection with modern geographic knowledge
  • D. Gusev, S. Stafeyev GIS Analysis and Digital Reconstruction of Ptolemy's India beyond the Ganges, Serike and Sinae
  • D. Gusev, S. Stafeyev Iterative Reconstruction of Ptolemy’s West Africa Using Modern GIS Analysis
  • D. Gusev, S. Stafeyev Visualization and GIS Analysis of Ptolemy’s One-Sided Globe in the Old and Modern Contexts
  • D. Gusev, S. Stafeyev Claudius Ptolemy’s East Africa Georeferenced and Visualized e-Perimetron, Vol. 18, No 4, 2023
  • D. Gusev, S. Stafeyev New Digital Reconstruction of Ptolemy’s Iran, Afghanistan, Turkmenistan, and Balochistan