Ptolemy's Methodological Principles in the Creation of His Map Projections

Abstract

AbstractPtolemy developed instructions for three projections, but only the first two projections were used in practice. These instructions, which contributed significantly to the development of theoretical cartography, did not explicitly describe the methodological basis on which they were elaborated. The derivation of the data used in the instructions thus remained partly unclear, such as the localisation of the centre of the latitude circles in the first projection. Here, an attempt was made to reconstruct Ptolemy's methodological principles. It turned out that he used a simple but ingenious method that made it possible to create all projections without trigonometric calculations, only with the use of compass (instrument to construct circles) and ruler.