### Determination of Latitude

How to determine your latitude by observing the stars.

The line NS is the Earth's axis: S is the South Pole, and the
North Pole points toward N. E stands for either East or Equator. A is
your position on the surface of the Earth. The Earth's axis points
very close to Polaris, the North Star. If you look at Polaris, it is
so far away that you are looking very nearly parallel to the Earth's
axis. NE which is tangent to the circle at A represents the horizon,
so angle NAP represents the angle above the horizon where one sees
Polaris. That angle is always equal to the latitude at your
position.Using this method, even the ancients could tell that the
Earth is round. This explains how the Egyptians could have measured
the circumference of the Earth very precisely.