Revisualising Ptolemy’s Geographia

Claudius Ptolemy’s monumental 2nd Century treatise, the Geographike hyphegesis, is one of the most important works in the history of cartography and gave a significant impetus to the Age of Discovery following its reappearance in Western Europe in 1397. Ptolemy’s great contribution to cartographic science was the separation of geographic data from its representation. By providing tables of geographic coordinates, rather than embedding them in commentaries as his predecessors had done, he was able to transmit a picture of the world that could be depicted in different ways according to the needs of the geographer and their audience.

Today we still marvel at the apparent accuracy of a work that stretches from Portugal to China, but easily forget that beyond the visual impact of the medieval maps which survive, there exists a remarkable resource in the raw coordinate data that form their basis. ‘Revisualizing Ptolemy’s Geography’ uses modern Geographical Information Systems (GIS) and statistical visualization to explore this unique dataset. In doing so it hopes to bring to light structural phenomena that may tell us more about its sources and construction.

This map is being drawn using the coordinates from Ptolemy’s Geographia.  Cities, land features, and coastlines are all listed separately and in linear sequence within the Geographia, such that a cartographer can ‘connect the dots’ between the coordinates to trace a map of the world as Ptolemy described it.  Ptolemy used traditional Greek parallels and hour intervals to create his latitudinal and longitudinal grid.

People

• Leif Isaksen