Polar Opposites – When Compasses Go Bad

I’m one of those lucky people who has an in-built compass that most times just knows instinctively which way is North. I think I got it from my Dad, as opposed to my Mum who was from the ‘turn-the-street-directory [remember those?] around-until-it makes-sense-and-then-stop-to-ask-for-directions’, school of navigation.

So it was no surprise that on last weekend’s trip to the beautiful Coxs River, I thought my inbuilt compass had gone a little wonky.

Which one of these is not like the other one?

The toppo map, the bend in the river, my inbuilt compass and my trusty reliable Silva compass seemed to be conspiring against my sense of sanity.

I couldn’t understand why Goolara Peak was behind us… it should be in front of us! This doesn’t makes sense.

It was only when my friend Helen came along and we conferred that things suddenly became crystal clear. The photo above says it all. Her compass is the one on the left, whereas mine on the right is showing exactly the opposite. Double confirmed by the electronic compass in my watch.

Who moved Goolara Peak? [Upstream on the Coxs River]

I emailed Silva [Sweden, not the USA company] to find out how to fix this. I’ve heard it’s as easy as wafting a magnet nearby. Here’s the response:

“The reason that your compass is not showing north is most likely due to it being subjected to a magnetic field that has polarized the needle. This is, unfortunately, fairly common in today’s world since we carry a lot of items that emit a magnetic field such as mobile phones, GPS and other equipment. A compass needle cannot change its own polarization, it has to be “forced” to reverse its polarity by a magnetic field. 

We write in the manual that it is very important to check the compass every time it is used since polarizations do happen, it is as important as checking any part of your survival gear before it is used, since your life may very well depend on its functions. [Lotsa: Couldn’t agree more… now!]

It is not complicated to reverse the polarization of the needle but to be 100% sure of the result you should be using a controlled magnetic field. Because of this I do not recommend that you polarize your compass by yourself, if you send your compass to us here at Silva Sweden AB we can polarize your compass free of charge, the only cost for you is to ship the compass to us.” (David, Technical Support, Silva)

And so, today my compass which has served me well and I’ve trusted implicitly (until last weekend) will be going on a little Scandinavian holiday…

… I can’t help but think about all the magnetic fields in the aircraft and postal sorting machines between here and Sweden though!

« River and Creek Crossings – Dealing with Wet Feet  |  Bushwalking/Hiking Etiquette or How to make friends in the Bush (The Unofficial List!) »

Comments

    • says

      I’ve tried to think of all it could be and have narrowed it down to placing it on the roof of the car perhaps? It’s not been anywhere unusual or different. Curious and curiouser.

  1. Colin Walker says

    I have numerous compasses, a bit of a collector, and have also noticed this but only on Silva compasses so far. None of the Suuntos that I’ve seen have had this problem??? Retentivity is the property of the alloy used to make the needles that maintains it’s strength and polarity. I’m starting to wonder if the Sunntos use a better alloy?
    Please pass on any experience you may have had with polarity reversal.

  2. Graeme says

    If it’s 180 degrees out, can’t you simply just reprogramme your brain (no magnetic field required!) so that white equals north? Or am I missing something?

      • Colin Walker says

        Graeme I would not be sure that a compass needle that has inverted its magnetic polarity would align exactly south or would retain it’s current polarity. Walking in remote areas I need to be able to trust my compass.

  3. MissLisa says

    wow, I knew it could happen but thought it would probably take more than a phone etc to do it …. mum has the same sense of direction as you … unfortunately she did not pass on any of the genes to me!

  4. says

    I also have a compass with reversed polarity, so I etched “Blk = N” into the baseplate, as red points south and black points north. Got this tip from good old Horace Kephart.

    Thanks for the tip on checking the compass each time before a trip to make sure the polarity hasn’t been unknowingly reversed. I really hadn’t thought of that!

  5. Mike says

    Magnet in a GPS ??? It’s a radio receiver !!!!

    Magnet in a Mobile Phone ??? – maybe if you use a case that has a magnetic latch. There are tiny magnets to hold in stylus. My phone has an Electronic Compass inside it – if it had a magnet strong enough to affect an external compass, it would ruin the internal compass.

    Beware of putting your Emergency Beacon near anything with a magnet – some PLBs are activated by a magnet !

  6. surveyorssos@bigpond.com says

    Ah, the old south point north compass … ;-( It’s made to trick us.

    A while ago 2 of us were taking bearing on mountains and walking set bearings. My friend was always about 15 degrees different. He complained that he had had a few of his compasses (he was now onto his 5th!!) change polarity.

    We finally worked out the problem … his special “outdoor shirt” had some great pocket clips … little magnets to keep them closed. Guess where he used to store his magnet …? String looped around his neck and then compass in his top pocket.

    Watch the clothes you wear. They may have magnets in them!!

    Marcus – who walks with ice creams .. :-)

  7. Jim says

    Lotsa,

    Had the same problem with a magnetised mouthpiece on a bladder hose that ‘attached’ to magnet on the sternum strap. Everytime the mouthpiece swung from side to side over the top of my compass – it remagnetised it. Solution was to prise out the magnet embedded in the mouthpiece.

Leave a Reply

Your email address will not be published. Required fields are marked *