If a navigator stands on the North Pole, the North Star will sit directly overhead at ninety degrees to the horizon in all directions. The top of the world is at ninety degrees latitude. On the equator, at zero degrees latitude, Polaris dances right on the horizon. So latitude can be directly determined by the angle between the polestar and the horizon. I will try to measure the angle of the North Star to the horizon to give me my latitude.
