Determine your Latitude: Altitude of Polaris

What is the relationship between one's latitude on earth and the altitude of Polaris above the northern horizon?

As explained in Starstruck Tonight:

From ancient times sailors have known that the altitude of Polaris above the horizon is the same as one's latitude on Earth.

Suppose you are in Norman, Oklahoma, where your latitude is 35 degrees north. Similarly, you will find Polaris at 35 degrees above the northern horizon.

To sail west at a constant latitude, Columbus kept the north star at a constant altitude above the horizon.

Measure the altitude of Polaris above your northerly horizon with a protractor quadrant!
Then you will have determined your geographical latitude.