/ Reverse polarity on a Compass

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glennofsheff - on 20 Jan 2013
on more than one occasion during a recent visit to Borrowdale in the lakes,a friend and i had compasses reversing their polarity , by which i mean the Red/North end of the needle, working normally a few minutes before, suddenly started pointing south , the White end then becoming the one pointing north.
even stranger was the fact that his compass kept true but later in the day his switched and mine then returned to its normally position.
this caused us some problems the following day when the weather closed in quickly , as we left Great End , visibility was very poor and not able to
see any land features we took out our map and compasses both showing opposite readings for North. they were nt stored together but in separate packs
we did consider they may be affecting each other but the first time this happened, mine was the only compass we were using .

also considered was the affect of magnetic elements in the rock is this an issue in that area ?

i ve been hillwalking for a good number of years and never encoutered this before
has anyone else had this happened ? or more importantly know the reasons for this and if possible preventions

as for the effects of gadgets
we both had cameras but , i regularly take one and its never been a problem

any suggestions most welcome !
liz j on 20 Jan 2013
In reply to glennofsheff:
Yes, had this happen to me a couple of years ago on the top of the Glyders in awful weather and ended up on Glyder Fawr instead of Fach. I put it down (afterwards) to having my sister's camara in my pocket as the compass corrected itself later. The camara had a rechargable internal battery rather than disposable ones.
glennofsheff - on 20 Jan 2013
In reply to liz j: thanks liz , my camera does have a rechargable battery , but i have used it many times before with no problems , i guess its worth me doing some tests with and without it to at least eliminate that as being the cause ,
thanks again
chiz - on 20 Jan 2013
In reply to glennofsheff: Between Great End and Bowfell the rocks are partially magnetised due to a lot of iron in the rock and compasses are affected. Same in Cuillin.
happy_c - on 20 Jan 2013
In reply to glennofsheff: my mates compass did this, although it was the magnet on his hydration pack clip . . . . . . . .
anaesthetic on 21 Jan 2013
In reply to chiz:

Good to know.

Also, ice axes...I'm told mobile phones can affect them too
jkarran - on 21 Jan 2013
In reply to glennofsheff:

You're probably carrying a magnet you're not aware of.
jk
obi-wan nick b - on 21 Jan 2013
In reply to glennofsheff:Just happened to me - I noticed it yesterday when checking gear for a trip. I keep my compass and a spare compass in the same bag in the top of my rucksack and they were pointing in different directions. I attacked the one pointing south with a magnet and it now seems to point in the same direction as the other one. (Hopefully I chose the right one!).
Silva offer a free re-magnetising service if you post it off to Switzerland however as the bezel on my spare had seized solid I don't have time to get that done!
StuDoig - on 21 Jan 2013
In reply to liz j:
It doesn't have to be the batteries either. My Olympus Tough Camera (metal casing) has a huge affect on a compass if in close proximity (less than 6"). once I spotted this I checked some other items I carry and found GPS also caused the compass to deviate, as did my mobile phone, but all needed to be within inches of the compass. The camera was by far the worst though.

If your worried that its something your carrying, then look for consistency - it should happen every time more or less.

Cheers,

Stuart.
NottsRich on 21 Jan 2013
In reply to chiz:
> (In reply to glennofsheff) Between Great End and Bowfell the rocks are partially magnetised due to a lot of iron in the rock and compasses are affected. Same in Cuillin.

This is my understanding of the area too.
chiz - on 21 Jan 2013
In reply to NottsRich: Not sure how local it is, but the iron in the rock definitely affects compasses at Ore Gap (the clue is in the name), and on Skye, but I think that is the basalt dykes. May of course also be batteries/axes/phones etc!
glennofsheff - on 21 Jan 2013
In reply to glennofsheff: thanks for all your responses guys ,
i think any of your suggestions could have been the culprit or maybe a combination of them all.
ill certainly be more on the ball in future and try to pack more considerately making sure the compass(es)are stowed well away from any potential magnetic sources .
many thanks and keep safe on the hill !
Cheese Monkey - on 21 Jan 2013
In reply to glennofsheff: This happens? Now I have an excuse for getting lost on the summit of Snowdon at night in zero vis! Although most probably still a monumental error on my part, plus my poor mate will never believe me.
Al Evans on 22 Jan 2013
In reply to Cheese Monkey: Up on Bleaklow once I had this happen at Shelf Stones, it was the aircraft wreck thats there, a big one, I think its a B42
though I believe , or have been told, that so many of the ferrous parts have now been stolen as souvenirs (it's a war grave) that all that is left these days is aluminimum so maybe it doesn't do it anymore.
liz j on 22 Jan 2013
In reply to StuDoig:
> (In reply to liz j)
> It doesn't have to be the batteries either. My Olympus Tough Camera (metal casing) has a huge affect on a compass if in close proximity (less than 6"). once I spotted this I checked some other items I carry and found GPS also caused the compass to deviate, as did my mobile phone, but all needed to be within inches of the compass. The camera was by far the worst though.
>
> If your worried that its something your carrying, then look for consistency - it should happen every time more or less.
>
> Cheers,
>
> Stuart.

That is exactly the same camera as I was carrying. I won't be making the same mistake again!
Ridge - on 22 Jan 2013
In reply to glennofsheff:
I simply carry a bottle of tippex and a red marker pen, which allows me to easily modify the compass needle in the event the polarity reverses..
John W - on 22 Jan 2013
In reply to Ridge:

You win this week's Top Tip!

:-)
John W - on 22 Jan 2013
In reply to John W:

Alternatively, draw a compass needle on your hand while facing north, then it can't possibly reverse polarity. Job done!
Pero - on 22 Jan 2013
In reply to John W: The polarity would reverse every time you turned round!
John W - on 22 Jan 2013
In reply to Pero:

Damn you Pero, you've thwarted my brilliant invention!
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