Portuguese Empire years for the Portuguese to follow up on Dias's voyage to the Cape of Good Hope, though it has also been speculated that other voyages were in fact taking place in secret during this time. Whether or not this was the case, the long-standing Portuguese goal of finding a sea route to Asia was finally achieved in a ground-breaking voyage commanded by Vasco da Gama. The squadron of Vasco da Gama left Portugal in 1497, rounded the Cape and continued along the coast of East Africa, where a local pilot was brought on board who guided them across the Indian
Brouwer Route that there was no accurate way at the time to determine longitude. The sighting of either Amsterdam Island or Saint Paul Island was the cue for ships to change direction and head north. However, this was reliant on the captain's expertise. The route was devised by the Dutch sea explorer Hendrik Brouwer in 1611, and found to halve the duration of the journey from Europe to Java, compared to the previous Arab and Portuguese monsoon route, which involved following the coast of East Africa northwards, sailing through the Mozambique Channel and then across the Indian Ocean, sometimes via India. By