Measuring lattitude

Something I’ve always wondered about…

When Robert Peary made it to the North Pole in 1909, how did he know when he got there?

I know you can tell your lattitude in the Northern Hemisphere by seeing how high in the sky the North Star is at night. At the North Pole it’s straight overhead while at the equator it is on the horizon. However, Peary couldn’t use the North Star for two reasons:

  1. He went to the Pole in April, when the Pole is in sunlight 24 hours a day.

  2. It’s hard to tell the difference between the North Star being 90 degrees overhead or 89 degrees and 30 minutes.

So, how did Peary (and Amundsen for the South Pole) know when they got there?

Zev Steinhardt

First, the North Star is not above the North Pole. It’s about latitude 89.

To answer your question: Using a sextant to measure the sun’s angular height avove the horizon. The sun’s latitude is known. Let’s say the latitude of the sun is 12.437 degrees above the equator. Say the sun’s height above the horizon is 12.537 degrees. Well, the north pole is 0.1 degree (6 nautical miles) away from the sun. Now wait 6 hours, and you’ll get a good cross fix because the sun has moved 90 degrees along the horizon.

From Polar Navigation (mentions a bit about using and misusing a sextant):

From this site:

Other related sites:

The Cook-Peary
North Pole Dispute

Polar Geography