Alfred Stückelberger and Heiner Rohner:
The mathematical requirements for Ptolemy's drafts of the world map
Cartographica Helvetica 46 (2012) 39–45
One of Ptolemy's extraordinary achievements was the novel method for drawing a world map, taking as much as possible the proportions of the surface of a globe into consideration. The result of his proposed projections – the first and second projections of the famous world map – is well-known. Less known, however, are the mathematical theories and computations he used for these manuscripts. The present article will try to bring light on the development of these projection methods – in close accordance with his writings – and to verify his computations. Should not only his ingenious method but also the astonishing precision of the computations of this great astronomer and mathematician be asserted, then that would be a welcome side effect. And finally, a look at the subsequent hand-written transmission of the map up to Mercator's magnificent 1578 Ptolemy edition shows how Ptolemy's specifications were taken into account later on.