Age of Discovery
Early geographical knowledge and maps

The Periplus of the Erythraean Sea, a document from 40-60 AD, describes a newly discovered route through the Red Sea to India, with descriptions of the markets in towns around Red Sea, Persian Gulf and the Indian Ocean, including along the east coast of Africa, which states "for beyond these places the unexplored ocean curves around toward the west, and running along by the regions to the south of Aethiopia and Libya and Africa, it mingles with the western sea (possible reference to the Atlantic Ocean)". European medieval knowledge about Asia beyond the reach of the Byzantine Empire was sourced in partial reports, often obscured by legends, dating back from the conquests of Alexander the Great and successors. Another source was the Radhanite Jewish trade networks of merchants established as go-betweens between Europe and the Muslim world during the time of the Crusader states.

In 1154, the Arab geographer Muhammad al-Idrisi created a description of the world and a world map, the Tabula Rogeriana, at the court of King Roger II of Sicily, but still Africa was only partially known to either Christians, Genoese and Venetians, or the Arab seamen, and its southern extent unknown. There were reports of great African Sahara, but the knowledge was limited for the Europeans, to the Mediterranean coast and little else, since the Arab blockade of North Africa precluded exploration inland. Knowledge about the Atlantic African coast was fragmented and derived mainly from old Greek and Roman maps based on Carthaginian knowledge, including Roman exploration of Mauritania. The Red Sea was barely known and only trade links with the Maritime republics, Venice especially, fostered collection of accurate maritime knowledge. Indian Ocean trade routes were sailed by Arab traders.

By 1400, a Latin translation of Ptolemy 's Geographia reached Italy from Constantinople. The rediscovery of Roman geographical knowledge was a revelation, both for map-making and worldview, although reinforcing the idea that the Indian Ocean was landlocked.
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