To compose his world map Fra Mauro (active ca. 1430-ca. 1459/1464) made use also of existing cartographic source material. Its circular form repeats the structure of medieval world maps such as the Hereford Mappa Mundi and those of Albertin di Virga (active 1387-1419) and Giovanni Leardo (active 1442-1453). His representations of the Mediterranean Sea, the Black Sea, and the Atlantic coasts of Europe are based on those employing the wind rose of nautical charts which Fra Mauro himself had designed. Most nautical charts reproduced only the outlines of coasts, but Fra Mauro added a great deal of information about territories of the interior, making his world map one of the first products of continental cartography. We cannot be certain, however, how the Camaldolite cosmographer was able to access such detailed and accurate information.

He undoubtedly consulted and utilized a manuscript containing the cartographic illustrations in in the Geography by Ptolemy (ca. 100-ca. 178). Although he criticized and openly disagreed with Ptolemy’s representation of the Indian Ocean as enclosed, Fra Mauro nevertheless maintained many elements of the Alexandrine cosmographer’s work, transcribing numerous place names and replicating some aspects of the coastal outlines of Asia. He included, for example, Ptolemy’s very large island of Taprobana.

The interior regions of Africa, on the other hand, come from maps designed specifically for Fra Mauro by Ethiopian monks sojourning in Venice. Of these maps, regrettably, no trace remains.

Toward the middle of the 16^th century, Giovanni Battista Ramusio (1485-1557) claimed that Fra Mauro had also made use of maps brought to Venice by Marco Polo (1254-ca. 1324) upon his return from China. Historical research has been unable to confirm this claim, but interesting analogies to Fra Mauro’s map can be found in the coastal outline of Asia provided in the Kangnido Map, made in Korea circa 1480, which is based on a lost prototype of 1402, which in turn relies on a Chinese map of circa 1330.