On Mapmaking

No maps made by Ptolemy are extant. Rather, only the texts of his geographic works, which include instructions for making maps, survive.

For Ptolemy, gathering information about the earth and places on it is critical to making accurate maps: "It remains for us to turn our attention to the method of making maps. There are two ways in which this matter may be treated; one is to represent the habitable earth as spherical; the other is to represent it as a plane surface" (Ptolemy 1932, 38). The sphere or globe is the best way to depict the round earth accurately. Practical problems with globes include size, portability, durability, storage. Even though Ptolemy recognizes that compromises will have to be made in depicting a round earth on a flat plane, this is the preferred way to make maps, as the viewer can see the entire world from one viewpoint.

Ptolemy recognizes that a mapmaker has to make choices, a major one being the subject of the map. He notes that detailed maps of Europe are difficult to make, because of the many known features and places that need to be legible on a map of reasonable size. As a solution Ptolemy proposes to make single maps of areas where fewer places appear (for some areas of Asia, for example) and make several maps for Europe, where many names appear. Twenty-seven maps are present in most editions of the Geographia, as follows: 1 world map; 10 maps of Europe; 4 of Africa, 12 maps of Asia.