Study reveals 'GPS' tool used by Portuguese to reach India

UK-based researchers have revealed details of the world's earliest known marine navigation tool that may have helped Portuguese explorer Vasco da Gama to reach India. Recovered from a shipwreck in the Indian Ocean in 2014, the tool called astrolabe is a bronze disc, 17.5 centimetres in diameter, engraved with the emblem of the King of Portugal from 1495-1521.