The compass

"Early in the Han Dynasty, between 300–200 BC, the Chinese fashioned a rudimentary compass out of lodestone " these discovery enabled the Chinese navigators to indicate the south with precision and navigate safely by day or night. This quickly gave an advantage to the chinese in terms of navigation, and it was the most efficient way to know the position of the boat

in conjonction with the reading of the stars. This technic was only supplanted in year 1300, and has been for a long time the "compass" of humanity.