The historical setting
The Piri Reis map is a world map compiled in 1513 by the Ottoman admiral and cartographer Piri Reis. Approximately one third of the map survives, housed in the Topkapı Palace in Istanbul. After the empire's 1517 conquest of Egypt, Piri Reis presented the 1513 world map to Ottoman Sultan Selim I (r. 1512–1520). It is unknown how Selim used the map, if at all, as it vanished from history until its rediscovery centuries later. When rediscovered in 1929, the remaining fragment garnered international attention as it includes a partial copy of an otherwise lost map by Christopher Columbus. The map is a portolan chart with compass roses and a windrose network for navigation, rather than lines of longitude and latitude. It contains extensive notes primarily in Ottoman Turkish. The depiction of South America is detailed and accurate for its time.
Sources
There is some scholarly debate over the various sources. In the modern sense, mappae mundi refer to medieval Christian schematic maps of the world. In the fifteenth century, the term was also literally used to describe world maps, and it is possible the source maps fit in that broader definition. The Jaferiyes are seen by scholars as a corruption of the Arabic Jughrafiya, most often taken to mean the Geographia of Claudius Ptolemy. Ptolemy's book was widely printed during the sixteenth century, accompanied by maps from Nicolaus Germanus and Maximus Planudes. The Jaferiyes may also refer to the largely symbolic world maps of medieval Islamic cartography. Descended from classical scholarship, these treatises sometimes used the loanword jughrafiya in their titles.
The Arabic and the four Portuguese source maps have not been conclusively identified but have been associated with several notable maps of the period. Finally, there is debate on the total number of source documents. Some scholars interpret the "20 charts and mappae mundi" in the inscriptions as including the other maps, and others interpret them to mean a total of 30 or 34. Compared to the Islamic cartography of the era, the map shows an atypical knowledge of foreign discoveries.
Iconography
Piri Reis's inclusion of many foreign accounts was atypical within the Ottoman Empire. After the conquest of Constantinople, Sultan Mehmed II began a project of creating copies of traditional Islamic maps in the Book of Roads and Kingdoms tradition. Piri Reis adapted the elements of iconography from the traditional maps—which illustrated well-known routes, cities, and peoples—to the portolan portrayals of newly discovered coasts. Piri Reis provides an unusual etymology of "Ocean" as coming from "Ovo Sano", or "sound egg". The accepted etymology comes from the world-encircling river, Oceanus. Historian Svat Soucek has described the egg etymology as naive. Historian Karen Pinto has proposed that the egg etymology is better understood in the context of traditional attitudes towards the deep seas in Islamic culture.
Typical medieval world maps followed a standardized and schematic design, with a disc-shaped "inhabited quarter" of the world separated from Mount Qaf by an impassable Encircling Ocean. Pinto observed that Piri Reis had reconciled the discovery of new land beyond the sea with this existing model, by framing the Old World—ocean included—as a giant lake surrounded by the shores of the New World. The Ottoman miniatures that illuminate the map can be further interpreted in the context of new possibilities and the changing cultural landscape.
Southern Continent
The Southern Continent stretching across the Atlantic Ocean is most likely Terra Australis. Some authors have claimed that it depicts areas of South America not officially discovered in 1513, and a popular but disproven hypothesis alleges it to be Antarctica. Maps of the period generally depicted this theoretical southern continent, in various configurations. This land was posited by Roman geographer Ptolemy as a counterbalance to the extensive land areas in the known world. As explorers charted the Southern Hemisphere, it pushed back the potential bounds of Terra Australis. Discoveries, like Tierra del Fuego and New Holland, were initially mapped as the northern edge of the unknown southern land.
As these areas were mapped, Terra Australis shrank, grew vague, and became a fantastical locale invoked in literature, notably Gulliver's Travels and Gabriel de Foigny's La Terre Australe Connue. Belief in the Southern Continent was abandoned after the second voyage of James Cook in the 1770s showed that if it existed, it was much smaller than imagined previously. The first confirmed landing on Antarctica was only during the First Russian Antarctic Expedition in 1820, and the coastline of Queen Maud Land did not see significant exploration before Norwegian expeditions began in 1891.