Ptolemy was a geographer and astronomer in the library of Alexandria who lived from about 90 to 168 AD. He wrote several books that would influence scientific thought for over a millennia.

His book "Geographia" was the most authoritative source for geography through the middle ages and was seen as an influence on maps much later. Like other great minds of antiquity, Ptolemy was one of the founders of modern cartography. Concepts used in this text such as a strong focus on scale, the use of longitude and latitude lines, his method of projection, and representing the world in a series of maps both global and local are all evident in the modern atlas.

Ptolemys authority on cartography and geography was considered so complete that the side effect was the acceptance of errors from his work well into the late middle ages. These include the belief in a geocentric universe (where the sun revolves around the earth) and a significant miscalculation of the sizes and positions of key land masses. When Columbus landed in the new world, his belief that he had landed in Asia was based upon Ptolemys calculations of the circumference of the world and relative sizes of the continents. Another continent the size of North / South America and the vast expanse of the Pacific Ocean was not accounted for in the Ptolemaic world view.

Ptolemy is also known for conventions that we use today including representing subsections of a degree in minutes and seconds, the convention of a single low resolution map of the world accompanied by multiple higher resolution local maps as the the format of Atlases.