Portolan chart  From Wikipedia, the free encyclopedia Jump to:
navigation, search  Portolan or portulan charts are navigational
maps based on compass directions and estimated distances
observed by the pilots at sea. They were first made in the 13th
century in Italy, and later in Spain and Portugal. With the
advent of widespread competition among seagoing nations in the
Age of Discovery, Portugal and Spain considered such maps to be
State secrets. The English and Dutch relative newcomers found
the description of Atlantic and Indian coastlines extremely
valuable for their raiding, and later trading, ships. The word
portolan comes from the Italian adjective portolano, meaning
"related to ports or harbours."  Contents and themes[edit]
These charts, actually rough maps, were based on accounts by
medieval Europeans who sailed the Mediterranean and Black Sea
coasts. Such charts were later drafted for coastal resources in
the Atlantic and Indian oceans. At the beginning of the Age of
Discovery, charts had been made