English Cartographer Edward Wrights Portolan chart for sailing
to the recently discovered Azores.
The first great wave of expeditions was launched by Portugal under Prince Henry the Navigator.
European sailing practices before Prince Henry had been primarily coastal. Voyages out of sight of land relied on proven routes detailed in a portolan chart.
Portolan charts showed details of geographic land features, allowing navigators to identify their departure point, follow a compass heading, and on landfall identify their position and drift from the
newly presented land features.
Due to the risks involved in this process, European sailors avoided sailing beyond sight of land for extended periods. A number of nautical myths explained these risks in terms of oceanic monsters
or an edge of the world.
Prince Henry's navigation challenged this belief.
The Madeira Islands were discovered in the Atlantic ocean in 1419, and in 1427 the Azores.
The Portuguese settled these islands as colonies.
Henry the Navigator's primary project was exploration of the West Coast of Africa and development of useful portolan charts.
There were commercial, regal and religious motivations for Henry's endeavor.
For centuries the only trade routes linking West Africa with the Mediterranean world were over the Western Sahara Desert. These routes bringing slaves and gold were controlled by the Muslim states of North Africa, long rivals to Portugal and Spain. The Portuguese monarchy hoped that the Islamic nations could be bypassed by trading directly with West Africa by sea. It was also hoped that south of the Sahara the states would be Christian and potential allies against the Muslims in the Maghreb.In 1434 the Portuguese explorers surmounted the obstacle of Cape Bojador. In the bull Romanus Pontifex the trade monopoly for newly discovered countries beyond Cape Bojador was granted to the Portuguese.
Within two decades of Portuguese exploration, the barrier of the Sahara had been overcome and trade in slaves and gold began in what is today Senegal. A trading fort was built at Elmina. Cape Verde became the first sugar producing colony.
In 1482 an expedition under Diogo Cão made contact with the Kingdom of Kongo.
The crucial breakthrough was in 1487 when Bartolomeu Dias rounded (and later named) the Cape of Good Hope and proved that access to the Indian Ocean was possible from the Atlantic.
In 1498 Vasco da Gama made good on this promise by reaching India.
