Compass direction using a watch: Difference between revisions
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== Using a standard watch == |
== Using a standard watch == |
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Using a standard 12-hour watch, such as a wristwatch, one's approximate bearings can be found as follows: |
Using a standard 12-hour watch, such as a wristwatch, one's approximate bearings on the norther hemisphere can be found as follows: |
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# Rotate the watch such that the hour hand is pointing towards the Sun. |
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# The point halfway between the hour hand and 12 o'clock then points towards the south. |
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# The point halfway between the hour hand and 12 o'clock points towards the south. |
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There are minor inaccuracies due to the difference between [[local time]] and zone time, and due to the [[equation of time]]. |
There are minor inaccuracies due to the difference between [[local time]] and zone time, and due to the [[equation of time]]. |
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During [[daylight saving time]], the same method can be employed using 11 o'clock instead of 12. |
During [[daylight saving time]], the same method can be employed using 11 o'clock instead of 12. |
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On the southern hemisphere, the same holds for the northern direction. |
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==Explanation== |
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On the northern hemisphere, at noon, the sun appears in the southward direction. The sun performs its circle in 24 hours, thus with half the speed of a 12-hour watch's hour hand. Therefore the angle has to be bisected. |
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== Direction-finding watch == |
== Direction-finding watch == |
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The photograph to the left shows a specialized 24-hour watch optimized for finding directions using the Sun. With the watch set to indicate local time, the hour hand points directly at the Sun. North is indicated by the local noon position (in the Northern Hemisphere). |
The photograph to the left shows a specialized 24-hour watch optimized for finding directions using the Sun. With the watch set to indicate local time, the hour hand points directly at the Sun. North is indicated by the local noon position (in the Northern Hemisphere). |
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Revision as of 22:42, 25 April 2008
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It is possible to locate a compass direction using a watch.[1] This survival technique is well-known in organisations such as the armed forces and Cub Scouts.
Using a standard watch
Using a standard 12-hour watch, such as a wristwatch, one's approximate bearings on the norther hemisphere can be found as follows:
- Rotate the watch such that the hour hand is pointing towards the Sun.
- The point halfway between the hour hand and 12 o'clock then points towards the south.
There are minor inaccuracies due to the difference between local time and zone time, and due to the equation of time.
During daylight saving time, the same method can be employed using 11 o'clock instead of 12.
On the southern hemisphere, the same holds for the northern direction.
Explanation
On the northern hemisphere, at noon, the sun appears in the southward direction. The sun performs its circle in 24 hours, thus with half the speed of a 12-hour watch's hour hand. Therefore the angle has to be bisected.
Direction-finding watch
The photograph to the left shows a specialized 24-hour watch optimized for finding directions using the Sun. With the watch set to indicate local time, the hour hand points directly at the Sun. North is indicated by the local noon position (in the Northern Hemisphere).
See also
References
- ^ Arthur Mee (1920). The Children's Encyclopedia. p. 4777.
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