Buying a compass

by Nigel Williams

When heading for the great outdoors we are encouraged to have a map and a compass and know how to use them together so we don't get lost. It sounds a simple message but one that many people ignore in favour of using their phone GPS capability and free mapping. A single device, just follow the on-screen dot - except that the batteries deplete rapidly in the cold, touch screens don't respond when wet and can be almost impossible to read in bright sunlight. Add to that free mapping often lacks the detail needed to navigate effectively and there is now clear evidence that habitual use of the device for all journeys can have a lifetime negative impact on our spatial awareness, map memory and cognitive navigation development.

Despite the fact that these days most people have an electronic device to assist with navigation, rescue teams are reporting an increase in the number of people becoming lost in the hills and estimate that poor navigation accounts for around 50% of call outs.

A compass is essentially a simple scientific instrument and it can save your life, but more likely save you from the embarrassment of being disorientated and late home. There are many recreational compasses on the market and the price range is considerable from about £5 to £70, but in general you pay for what you get. Silva and Suunto are the two most reliable makes with the widest range of models.

The variables of cost are the base plate size, having a magnifying glass within the base plate and the range of markings and scales on the base plate. The longer the base plate the more accurately one can aim at things when navigating across country. A magnifying glass can often help one see detail that may be partially hidden by writing on the map for instance. Longer base plates will have a wider range of scales.

Personally, I tend to avoid the mirror compasses for sighting on far away landmarks and accurate plotting skills which are not required for most recreational navigation. In some of the more expensive compasses there can be a small screw to adjust the dial alignment to take into account the magnetic variation (MV) so that one does not need to make that adjustment every time the compass is used; however in the UK I would suggest this is largely irrelevant for a few decades as MV is currently less than the manufacturers estimated accuracy tolerance of the device, which is usually around 2º. Another addition is a black needle that is not magnetised but acts as a clinometer if the compass is put on its side and the baseplate angled to match the slope. The needle will hang down vertically and using the degrees on the dial the angle of the slope can be measured. Useful in winter in the mountains to assist with avalanche information but rarely, if ever, used.

More significant to the cost though is the steadiness, magnetised strength and reliability of the floating needle in the housing capsule.

The liquid in the capsule is also a cost factor, water is cheaper than something akin to white spirit which has a slightly thicker, more oily texture and has a much lower freezing point, around -25º, so good in winter and it steadies the needle movement if you are walking cross country on a bearing. The needle balances on a fine pin and the south (white) end of the needle is fractionally longer than the north (red) end to counter the north end being pulled towards the ground. Finally, there is the sealing of the capsule with no air bubbles. So, there is quite a bit of super accurate manufacturing involved.

The most expensive recreational compasses, around £60 plus, have a plastic disk instead of a needle which sits on a small magnetic block on the pin. This provides a much bigger surface area in contact with the white spirit which dampens the movement of the needle making it settle very quickly and one can walk or run with it quite accurately across country without the needle wobbling all over the place. Preferred by orienteers and professional outdoor instructors.

Lastly, most compasses come with a lanyard loop. Don't hang it around your neck! Undo the loop, tie one end on the compass and at the other end tie a loop big enough to pass the compass through. One can then thread the big loop through a zip pull or belt loop before the threading the compass through the loop. (A few pace counting beads can also be added). Alternatively use a mini karabiner to attach it to yourself (not your rucksack). It can then be used on a map at a comfortable waist height, aimed accurately at eye level at landmarks and kept in any pocket away from your mobile phone and other magnets or pieces of metal.

For most people walking or biking well-marked paths only using the compass for map setting and deciding which path to take at a junction, not really intending to walk cross country legs in remote terrain, then a short base plate is adequate; expect to pay around £20 - £25 for a good model. Anyone aspiring to be more adventurous should consider a longer base plate, expect to pay around £30 - £35. If you are a HARVEY map user then there is only the Silva Expedition Mk 4 with the 1:40,000 scale on it.

The manufacturing of compasses has largely moved to China, and recently there seems to be a higher incidence of bubbles developing in the capsules. Sometimes they can appear on the higher tops in a low pressure weather system but disappear back down at sea level. Once a bubble is about 5mm across it is going to impact the needle accuracy. Most manufacturers will replace the compass for free up to 5 years from manufacture.

You may also be interested in ...

- If you are in need of a compass then we stock a great range of items and other useful navigation equipment, suitable for all levels of navigation.

- For the perfect lanyard to go with your compass, the HARVEY Map - Measure - Go! scale bar laces double up to make measuring distance easy! Available in two scales, 1:25,000 scale markings (red) and 1:40,000 scale markings (yellow).




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