# Measuring lattitude

**URL:** <https://boards.straightdope.com/t/measuring-lattitude/58022>\
**Category:** Factual Questions\
**Created:** [March 14, 2001, 11:20pm UTC](https://boards.straightdope.com/t/measuring-lattitude/58022 "2001-03-14T23:20:35Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![zev\_steinhardt](https://avatars.discourse-cdn.com/v4/letter/z/97f17d/32.png) [@zev\_steinhardt](https://boards.straightdope.com/u/zev_steinhardt)\
**Post date:** [March 14, 2001, 11:20pm UTC](https://boards.straightdope.com/t/measuring-lattitude/58022/1 "2001-03-14T23:20:35Z")

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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

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**Author:** ![bizerta](https://avatars.discourse-cdn.com/v4/letter/b/3be4f8/32.png) [@bizerta](https://boards.straightdope.com/u/bizerta)\
**Post date:** [March 14, 2001, 11:43pm UTC](https://boards.straightdope.com/t/measuring-lattitude/58022/2 "2001-03-14T23:43:36Z")

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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.

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**Author:** ![Ringo](https://avatars.discourse-cdn.com/v4/letter/r/779978/32.png) [@Ringo](https://boards.straightdope.com/u/Ringo)\
**Post date:** [March 14, 2001, 11:48pm UTC](https://boards.straightdope.com/t/measuring-lattitude/58022/3 "2001-03-14T23:48:41Z")

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From [Polar Navigation](http://members.tripod.com/norpolar/Polar_Navigation.html) (mentions a bit about using and misusing a sextant):

> [@](#):
>
> Before the advent of radio and satellite aids to navigation, polar travelers, once out of sight of visible landmarks, had four primary means of navigating and determining location: (a) dead reckoning; (b) timepiece; © magnetic compass; (d) sextant.

From [this site](http://www.matthewhenson.com/1927.htm):

> [@](#):
>
> Because it was so easy to travel, Peary sledded in various directions to take sextant readings which verified his location.

Other related sites:

[The Cook-Peary  
North Pole Dispute](http://members.tripod.com/PolarFlight/controversy1.htm)

[Polar Geography](http://www.northpole-expeditions.com/vj/vj5.html)