For centuries, European sailors navigated between the ports of the Mediterranean Sea. Because of Italy’s prominence in trade, many of the first great explorers, Columbus, John and Sebastian Cabot, Vespucci, and Verrazano, were Italians.
The ancient sea captains directed their ships using the stars, the sun, their experience, and various instruments, including the astrolabe, which allowed navigators to measure the angle of the sun and stars and determine their latitude.
But in the eleventh century, a new device, the compass, allowed sea captains to navigate accurately regardless of weather or time of day. Nevertheless, experienced navigators also continued to rely on a tactic called “dead reckoning.”
By estimating the speed of the ship, the navigator calculated the distance passed in a day and recorded it on a map. Dead reckoning was never exact and relied largely on the instinct of the sailor and his knowledge of the sea.