To get where they're going, navigators first need to know where in the world they are. And to help them find out, navigators calculate their latitude and longitude, which are imaginary lines around the globe. Navigators sometimes found their latitude using an instrument called an astrolabe like the one above.
Lines of latitude are the parallel lines north and south of the equator.
The equator is at 0 degrees latitude. There are 90 degrees north and 90 degrees south of the equator. In the northern hemisphere, navigators can use an astrolable and the North Star as a way to determine their latitude. The North Star is the first star in the handle of the Little Dipper. The angle that the North Star is above the horizon is equal to the latitude of the observer.