For many centuries, navigators hoped they could find longitude by observing the movement of stars at night.

VOA: special.2010.07.14

And Dewey was influenced by observing his own children.

VOA: special.2010.01.07

A navigator can know the latitude of his ship by observing the location of stars, where the sun rises in the morning and sets in the evening, and what time of year it is.

VOA: special.2010.07.14