ABSTRACT
Ptolemy’s first concern was to define two technical terms essential to his presentation, geographia and chorographia, since a distinction between the two was an essential part of his thesis. Ptolemy also emphasized that chorographia was not mathematically oriented, but geographia had to take into account the size and shape of the earth and its position in the cosmos and relationship to the fixed stars, issues that were more astronomical. Ptolemy described how the technique of measuring the distance between two points on a single meridian could be used to determine the circumference of the earth. Ptolemy’s first problem with Marinos was his dimensions of the inhabited world, which he believed were excessive. Ptolemy believed that Marinos’ north-south extent of the inhabited world was excessive, and set out to prove the fact.
