Article ID: CBB116997130

The Western Coast of Africa in Ptolemy's Geography and the Location of his Prime Meridian (2016)

unapi

A controversial question concerning ancient geography is the location of the prime meridian which underlies the position data in Ptolemy's Geography and runs through the Fortunate Islands. An answer to this question is derived by means of a localisation of the places given by Ptolemy at the African western coast, i.e. in Mauritania Tingitana and Libya Interior, whose modern identifications are often uncertain or unknown. The origination of Ptolemy's positions from the distance data of seafarings is considered. A comparison of his data with distances reported by Pliny yields a satisfactory agreement. The localisation of Ptolemy's places is based on distances derived from Ptolemy's coordinates and partly on further information by ancient authors. Through it previous identifications are confirmed and new identifications are found. It shows that the Fortunate Islands correspond to several eastern islands of the Canary Islands. Explanations are given for the errors of Ptolemy's position data. A likely error by Ptolemy barely considered is his repetition of a part of Mauritania Tingitana in his description of Libya Interior. The existence of this repetition is confirmed by an adjustment of a transformation between the positions of the duplicated places and a statistical test of the arranged model. A comparison of longitudinal distances in different ancient sources reveals that the position of Ptolemy's prime meridian is based on distances given by Marinos and Eratosthenes.

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Authors & Contributors
Panichi, Silvia
Shcheglov, Dmitry A.
Prontera, Francesco
Marcotte, Didier
Seubert, Philippe
McPhail, Cameron
Concepts
Geography
Cartography
Roman Empire
Longitude and latitude
Meridians (geodesy)
Maps; atlases
Time Periods
Ancient
17th century
20th century, early
20th century
19th century
18th century
Places
Mediterranean region
Europe
Middle and Near East
Greenwich (England)
Hellenistic world
Arabian peninsula
Institutions
University of St. Andrews
Royal Observatory Greenwich
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