Calling ALL Hill Walkers!
It’s a FACT, the catalyst for a substantial number of mountain rescue call outs in the UK is either directly or partially a result of a navigation error.
Is that ERRORalways the fault of the individual navigator? Or is there some insidious problem looming, causing havoc with our previously extremely reliable navigation tool – the compass?
Well folks the answer is the latter……read on for essential advice on your compass and the potentially dangerous implications of you being affected by REVERSED POLARITY.
Picture the scene:
You are out on the hill alone, ticking off that remote Munro. Unexpectedly the mist descends and you find yourself in poor visibility. Undeterred, you continue onwards and upwards. Navigation is easy; you are ascending a defined ridge which leads onto a broad summit plateau which gently rises to the summit over a shattered boulder field. Descent however, is a little more challenging, the underfoot conditions mean that the normal ‘defined’ Munro baggers path has not developed, a compass bearing is required to locate the descent ridge.
As usual, your compass is sensibly attached to the zip in the chest pocket of your waterproof jacket….the same pocket where you put your mobile phone. Taking a bearing to the top of the ridge, you start heading down….’alarm bells’ start to ring as the ground ahead seems to be dropping far more steeply than you remembered on the ascent. Suddenly out of the mist, the ground drops dramatically in front of you over what looks to be quite a significant crag. You stop to re-assess….imagine if this had been winter and the ground was snow covered; how easy it would have been to walk right over the edge?
It would be easy to assume that it was you who had made the mistake, but in the scenario above the compass had been affected by the magnet in your mobile phone case and the north/south needle had been reversed. Resulting in a bearing that took you in completely the wrong direction.
In the February edition of Scottish Mountaineer, Nigel Williams (Head of Training at Glenmore Lodge) wrote an article on this very issue. Readers were invited to respond with any similar experiences, stories came flooding in……there is a worrying and increasing trend.
As we all know, our compasses operate on the earth’s magnetic field; so what is ‘reversed polarity’ and how do we protect ourselves from being a ‘reversed polarity victim’?
The Cause: Magnetic fields exist around many items we commonly carry with us on the hill; mobiles & smart phones, magnets hidden inside mobile phone cases, avalanche transceivers, radios, personal locator beacons, GPS, cameras, car keys, small magnets on belt fastenings, under-wired bra’s ……. Lurking unexpectedly on route to the hill lies security loops as you enter outdoor and food stores, speakers in your car doors or on parcel shelves……..
The Effect: The compass needle may just be very briefly, partially or totally reversed when in close proximity to one of the above mentioned. If the needle becomes sluggish and slow to settle (it may appear to stick and be out of balance) it has become partially reversed. If the ‘north’ arrow (usually red) is pointing to south instead of north, then your compass has become completely reversed.
Prevention: A compass is a precise measuring instrument and should be treated accordingly. Your compass should be kept well away from all of the above mentioned items and well clear of magnets and magnetic fields which are associated with electrical circuits and ferrous metal objects.
Cure: Kevin Thomson, Marketing Manager at Silva Ltd says 'It is possible to ‘reverse’ the reversed polarity using a strong magnet. This can be achieved by quickly flicking the magnet outwards along the ‘north’ end of the needle. Repeat vice-verse. Always ensure you compare with a compass that is known to be correct. Note: If you are unsure how to CURE your Silva compass: SILVA will always take back and re-magnetise your compass, no matter how old the compass is.'
Can the compass be used in its ‘reversed polarity state by using the ‘south’ instead of the ‘north’ arrow? In my personal experience (this problem has happened to me 3 times in the past 12 months) the needle does not invert by exactly 180 degrees. It would appear to be approximately 10 degrees out and therefore using it in this state is not reliable.
Golden Rule #1. Keep your compass in a separate location to other electronic gizmos you carry with you on the hill and ensure when you are using it, that it is held well away from your body.
Golden Rule #2. Ensure you read the contours on the map. You should have a very clear idea as to what should happen under your feet as you walk on your compass bearing. If this is not happening, the alarm bells should be ringing and you should re-evaluate.
Golden Rule #3. Always carry a spare compass in the event of malfunction, damage or loss.
Golden Rule #4. Try to get into the habit of checking that your compass is working correctly prior to leaving home.
Page written by Heather Morning April 2013