Portuguese-Style Portolan Chart

Timeline

1. c. 1300–1450Mediterranean coast · MediterraneanFrom the late 13th to the first half of the 15th century, Italian and Mallorcan cartographers drew portolan charts with compass bearing lines and surveyed coasts, accurately depicting the Mediterranean and Black Sea shores, becoming the standard navigational document for merchant fleets sailing coastwise.
2. 1480–1490Lisbon and the cartographic workshop held in the Este Library · PortugalPortuguese charts of the 1480s turned their view to the East Atlantic, recording the African coast and islands from the Rio de Lagos (discovered 1471) to the Gulf of Guinea; charts by Pedro Reinel of about 1484–1492 and the anonymous chart C.G.A.5.c are the earliest surviving Portuguese portolan charts, serving both navigation and exploration records.
3. c. 1500–1580Atlantic and Indian Ocean routes · Indian OceanAs astronomical latitude observation became widespread, Portuguese cartography gradually incorporated celestial latitude data into the pure compass-and-estimated-distance method, and the portolan chart transitioned into the latitude chart, while remaining for a long time a practical base chart for coastal and offshore sailing.