In his Geographia, Ptolemy (c.90–c.168) presented a basis for geometric cartography by projecting a spherical surface onto a flat plane. The curved grid produced by his method encompassed slightly more than a quarter of the Earth’s surface (180 degrees West to East, and 120 degrees North to South). Establishing a prime meridian running through the Canary Islands (the Westernmost point known to Imperial Rome), and extending east to China, it allowed every city and landmark with a known latitude and longitude to be positioned relative to their actual locations on Earth.
Painstakingly gathered, these tables of thousands of underlying coordinates were included in the Geographia, along with a geometric method for creating cartographic projections. This map was drawn directly from these sources. It appeared in the earliest edition of the Geographia published north of the Alps, and included the cumulative inaccuracies produced by rudimentary survey techniques, compounded by centuries of transcription errors. The approach, however, marked a fundamental advance in European cartography by constructing maps from points of data arranged on two-dimensional grid that was consistent with their relative positions in three-dimensional space. Just as significantly, it created an immediate demand for more and better data.