Using a watch as a compass

sfakiaman · 24-02-2012 11:18AM #1

I meant to put this in the outback survival thread but it would be handy anywhere.

It's possible to determine your orientation using an analog watch (i.e., one with hands) in place of a compass. The direction will be correct if the watch is set for true local time, without adjustments for daylight savings time. And the further you are from the equator, the more accurate this method will be.

In the northern hemisphere, hold the watch horizontal and point the hour hand in the direction of the sun. Bisect the angle between the hour hand and the twelve o'clock mark to get the north-south line. North will be the direction further from the sun.

In the southern hemisphere, hold the watch horizontal and point the twelve o'clock mark in the direction of the sun. Bisect the angle between the hour hand and the twelve o'clock mark to get the north-south line. North will be the direction closer to the sun.

krissovo · 24-02-2012 11:24AM

If you have a digital watch (like me) you can draw a clock face with the correct time and perform the same activity.

baords dyslexic · 24-02-2012 02:38PM

Was reading recently how a magnetic compass in a tank (or any where near it) in the 2nd WW was useless so in the desert they used a sun compass. Quite surprised to see they were still being used in the First Gulf War http://www.sundial.pwp.blueyonder.co.uk/howardsuncompass.html and I think this was one of the versions used in WW II http://www.ww2talk.com/forum/north-africa-med/31724-bagnold-sun-compass.html

krissovo · 24-02-2012 07:29PM

baords dyslexic wrote: »

Was reading recently how a magnetic compass in a tank (or any where near it) in the 2nd WW was useless so in the desert they used a sun compass. Quite surprised to see they were still being used in the First Gulf War

You just brought back some fond memories, I was in a centurion tank in the first Gulf War. Basically spent the first 8 weeks lost, for navigation we had to get out of the tank and walk 20 meters away to get a decent bearing. One sun compass was per troop of tanks (5 heavy, 3 light) was issued. We still got lost and after another month they gave us Magellan's which were very basic GPS units.

CamperMan · 25-02-2012 11:55AM

what if the sun isn't shining?

baords dyslexic · 25-02-2012 01:49PM

CamperMan wrote: »

what if the sun isn't shining?

At least then you know you're lost in Ireland.:P

Grizzly 45 · 25-02-2012 02:20PM

krissovo wrote: »

You just brought back some fond memories, I was in a centurion tank in the first Gulf War. Basically spent the first 8 weeks lost, for navigation we had to get out of the tank and walk 20 meters away to get a decent bearing. One sun compass was per troop of tanks (5 heavy, 3 light) was issued. We still got lost and after another month they gave us Magellan's which were very basic GPS units.

Would have thought that tanks would be degaused[de magnetised] like ships these days to prevent this and against ,if they are still used,magnetic contact mines.

baords dyslexic · 25-02-2012 02:46PM

Grizzly 45 wrote: »

Would have thought that tanks would be degaused[de magnetised] like ships these days to prevent this and against ,if they are still used,magnetic contact mines.

A magnetic compass has a magnetised needle in it so its going to point to the nearest chunk of metal (like a tank) untill you get far enough away from it.

sfakiaman · 25-02-2012 08:31PM

CamperMan wrote: »

what if the sun isn't shining?

Even on a very dull day the sun will cast some bit of a shadow, so stick a stick upright in the ground and the shadow will give you the position of the sun.

Grizzly 45 · 25-02-2012 10:51PM

baords dyslexic wrote: »

A magnetic compass has a magnetised needle in it so its going to point to the nearest chunk of metal (like a tank) untill you get far enough away from it.

So how do ships sort this out?Considering they are all metal as well???

baords dyslexic · 25-02-2012 11:11PM

Grizzly 45 wrote: »

So how do ships sort this out?Considering they are all metal as well???

The traditional magnetic compass on a ship is mounted in one location in the binnacle which is set up with magnets to compensate for the metal in the ship.

Not sure why you can't do that in a tank?

http://en.wikipedia.org/wiki/Compass has it that the correction is made by two iron balls mounted either side of the compass.

robdsherlock · 25-02-2012 11:49PM

seen this on bear grill's.

its a handy technique if ya don't have a compass with you!

Using a watch as a compass

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