compasses question?

M

martin j

Joined
May 16, 2001
Messages
692
Most compass co.'s say if you leave a compass near big metal objects for a long time, it can lose accuracy due to magnetic distortions or somethin like that. But I can't find information on "how long?" So how long can you keep a small compass in a small survival tin or kit with knife etc, before it is affected ???? How bad is it affected????
Thank you
Martin
 
Good question, Martin - I wonder the same thing. As it is I just take my compasses out every so often and make sure they can still find North.
 
I can't answer the how long question but I keep knives and compasses in close proximity often and haven't had one go bad yet.

When I moved to Brazil I had one reverse 180 degrees. It pointed south. I don't know why or how but it went out with the trash. You can always check your compass periodically with another compass of known integrity. Mac
 
A compass can lose accuracy really only if placed near another magnet.
Storage in a tin should not affect it, however your compass is too important an item in your PSK to take a chance.
Calibrate your compass against a known direction regularly. This can be done by orienting a street direction with a map, or if you do not have a known direction, it is a simple matter to mark two paint spots on a road or car park using a good quality or trusted compass bearing, and ensure occasionally (3 months?) that you check that *your* compass is holding a true bearing.
Many more expensive compasses can be re-calibrated by the manufacturer if needed, but if it is a cheapie, better to discard and replace.
There is a method of DIY calibration using magnets, but it can very easily go wrong if incorrectly done. Be VERY wary of DIY unless you are confident of the procedure.
 
Thanks for replies, I just checked a Brunton base compass that was lost behind some boxes and pipes for probably 3 years, it still works fine. Is there anyone who's compass lost it's orientation?
Moving to Brazil- this was from northern hemisphere? Does this reverse N-S field for compass orientation?
 
That move was from PA to Brazil. I don't know why that compass had a pbroblem the others were fine.

Compass needles are weighted to stay level according to the earths magnetic field as well as aligned with it. I had several Silva Boy Scout compasses that would still point north but with the needle cocked at a sharp angle so that it made contact with the clear plastic case. The needle wouldn't rotate freely. I gave these to my brother back in PA and they work fine there.

My Recta DP-2 has made the NA - SA trip several times with no problems. It also works in both northern and southern hemispheres. Mac
 
I think Bluey's right on. I had a compass mounted on the steel dash of a car for years. Plenty of steel in cars in those days. It remained accurate. Not to mention compasses on steel ships. A strong magnet, on the other hand, could mess with the magnetic orientation of the needle.
 
"Does this reverse N-S field for compass orientation?"
No, the earth's magnetic field is constant in orientation for all practical purposes. There is evidence that it changes position (the magnetic north and south poles move around, very slowly, over very long periods) but the changes in our lifetimes will not be worth noteing.
Enjoy!
 
Well, actualy, there is some geological evidence that such global catastrophies as the last ice age were due to the sudden reversal of the polarity of the 'poles', which caused a shift of the axis of the earth and an instantaneous climate change.
 
Randjack,

Nostradamus didn't mention that so we're going to be just fine. Besides we all know it's global warming that causes ice ages. Don't you go to the movies? It's best to stock up on tinfoil before "they" ban it :eek: Mac
 
stored (well- lost) an old military compass behind a loudspeaker. When I moved and found it, it had reversed polarity - the N-Part pointing south. The magnetic field-power seems to be the the reason.
The description of the military compass says: keep clear of larger items made of metal or power lines - for using the compass very accurately (<1/2 degree) I was told to go away from the gun - 3 meters they told me... Guess what a tank would do...

btw. I use a recta DP 65 or the recta DS 40 (clear plate)

Andreas
 
Just to clear up a possible misconception here. IMO storing a compass in a metal box, tin etc will not affect its accuracy.

When you are taking a bearing, keep away from magnets, power lines and metal objects including vehicles, fence lines, railway lines, water tanks and so on, as the compass' magnetic field will be attracted to these and give you a false reading. About 10 feet is usually far enough away from large objects, more if you want to be certain.
A common magnetic source that many forget about is a radio handset clipped to your shoulder area. Handsets have a magnet built in them that can seriously distort your bearing. If you have a radio with you, tuck the handset in the back of your shirt while using the compass.

Cellphones also have a built in magnet, keep the cell in your pants pocket and there shouldn't be a problem when sighting the compass
 
I ran into compass problems last year in Alaska due to the 4 inch .41 magnum in the chest holster. I'm telling you, I love to have problems like that. I wish I had problems like that just about every day. In fact if you are out in the bush and you have problems with your compass due to a firearm, ATV, 4x4 etc then keep in mind that you are having a GOOD DAY. ;)
 
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