Dead Reckoning is how the sailors mapped the world after Christopher Columbus came to the New World. Using the stars, they could find their latitude (distance between the equator and the poles). But before accurate clocks were created, they could not tell their longitude (how far east or west they were) unless they saw land that they knew. So to cross the oceans they used dead reckoning. This is also how Richard Byrd became the first person to fly to the North Pole in 1926. He was able to fly for 16 hours and come back to the place he had left, with only ice fields beneath him.