Ptolemy (87-150 AD) was an Egyptian mathematician, astronomer, and geographer who lived and studied in Alexandria, the Mediterranean cultural center and an important trade center. Here he was able to study ancient authorities and also consult contemporary travellers and merchants. From this wealth of accumulated knowledge, Ptolemy composed his Geographia, in which he explained his method, providing instructions for mapmakers for drawing parts of the earth on a flat surface as well as a means of calculating latitude and longitude. Geographia was destined to dominate the the Christian and Moslem world for 1,500 years.
Ptolemy introduced the concept of latitude and longitude, forming a grid covering the world, making it possible to plot the position of principal land-marks by observations. Unfortunately Ptolemy was hampered by the paucity of observations, which resulted in some exaggerations and significant errors, and by lack of information, which was often circumvented by invention. His most famous errors were the depiction of a landlocked Indian Ocean and an under estimation of the circumference of the globe. The later of which certainly contributed to the belief of Christobal Colombo that he could easily reach the Far East by sailing West. Despite these flaws, his work was of fundamental importance.
In 1477, the first printed edition of Ptolemy’s Geographia with maps was issued in Bologna. Testimony to the influence of Ptolemy is given by the number of editions ofPtolemaic atlases that were subsequently published as late as 1840.