This map is part of the Lopo
Homen Atlas (Also called Miller Atlas). With the onset of voyages
on the open sea, coastal navigation techniques were no longer practical.
It became necessary to study the stars at night and the Sun during the
day to calculate the information necessary for efficient navigation.
It was thus that oceanic or astronomical navigation began, and with
it came a new type of nautical map which contained information on navigational
aspects. It included information on latitudes of key coastal areas,
on harbours, bays and capes, distances, landmarks and angles of the
sun. It also described the wind and sea currents and recommended appropriate
anchorage spots. In contrast to the traditional maps, the new ones did
not chart entire coasts but merely the areas which had been navigated.
They often included recommendations for the best sailing times or an
alternative route considering the different winds and sea currents throughout
the year. The french National Library is home to a collection of maps
known as the Miller Atlas. Despite the misleading name, the maps are
actually of Portuguese origin and attributed to Lopo Homen, the King’s
official cartographer in the first decades of the XVI century (1519).