Navigating and safety in winter

by Nigel Williams

Walking in winter can be a very rewarding experience, it gives a different perspective on nature - sounds, light, animal tracks etc. For those comfortable with basic summer navigation skills who like to keep to the main tracks, paths and low hills, there is generally enough information to navigate successfully with even under a foot of snow in reasonable weather. If the plan is to head up to the higher hills and moors, then winter navigation skills need to be based on solid experience of summer navigation off paths and linear features. Leaving linear features where one usually has a predetermined choice of a few directions at a junction is simple by comparison to heading off across country. Navigationally and environmentally, it can be a significant step to go from summer to winter on the high hills.

The higher we go in the UK at any time of the year the colder and windier it gets and the greater the amount of precipitation, usually snow in winter. The average daily windspeed on the Cairngorm plateau in winter is around 40mph. Although the summit of Ben Nevis is only 4 miles from Fort William, it receives only 2/3rds of the sunshine, just over double the precipitation, and is on average 8.5 degrees colder with it rarely going above 0º degrees during the winter months, and winds will be 3 times stronger. It's not enough to be able to navigate, we need to be able to do it sometimes in very difficult conditions when the right equipment and clothing are also of paramount importance.

As I write, 15cms of snow has landed in the garden in the last 24 hours, enough to get the cross-country skis out. I can no longer see the edges of the flower beds, or where the grass meets the paving stones or gravel, and I can't tell by the sound or feel of walking on the different surfaces. Expand that into a couple of square kilometres of hillside and plateau with paths covered, gullies and streams filled in and small lochs frozen and invisible under the snow. You can begin to appreciate the skills, experience and confidence it requires to navigate in poor visibility. To be convinced you are heading in the right direction on a compass bearing that you have chosen and for a distance you have determined, to a feature that may be under snow; This brings into play a whole range of new navigation strategies.

Being in the cloud and on snow creates a whiteout effect, it feels a bit like walking inside a giant ping pong ball: there is no horizon line, blade of grass or boulder to aim toward. Many of our hill and mountain tops can be remarkably flat with low stone wind breaks on the summits that can be completely covered and difficult to locate, even in good visibility.

Navigation in poor winter visibility is almost entirely based on reading the contours and relying on compass and pacing skills. Observation which is so critical to the novice learning to navigate in the summer becomes almost irrelevant. What takes over is feeling the slope and referencing the angle you feel you should be crossing the slope. Straight up and down are easy to determine, but 30 or 50 degrees off that line is trickier. Long distances over about 1km need to be broken down into shorter legs, the choice of intermediate points to help keep one on track are critical. Using changes in steepness and aspect (the direction a slope faces) are invaluable. There is another useful tool in winter when combined with map and compass and that is the altimeter. It can help you traverse a slope accurately, locate your position especially if you are on a linear contour feature such as a ridge line, spur or broad gully. It can help with strategies to avoid avalanche risk and the risk of going over cliff edges and cornices.

We can't ignore the benefits of phone GPS and mapping in bad weather, to at least give a location but the ability to operate and view the touch screen when snow is landing on it is compromised and phone battery life is significantly affected by the cold. Carry backup power.

Pacing in summer compared to winter is likely to be different and a relatively gentle up hill slope in fresh snow can significantly distort distance judgement doubling the number of paces needed to cover a 100m. I allow for this by looking at my footprint in the snow. I usually do 60 paces to 100m in summer on the flat. The distance between the heel of the front boot and toe of the rear boot is roughly the length of my footprint. Half the length of the footprint will be 90 paces and heel to toe will be 120, not unusual on a gentle up hill in soft snow. In winter due to the lack of features one may have to pace for distances around 700m which begins to build in errors. In summer maybe half that is usually possible between features and they are of course visible on the ground.

Avalanche risk is dependent on a number of factors primarily wind direction slope aspect, angle and altitude. Temperature changes and long-term temperature influences are also relevant. A big thaw followed by a refreeze is what stabilises a slope. It is often said that most avalanches are caused by their victims' poor decision making.

The met office weather forecasts are reliably accurate and can even cover individual mountains enabling realistic planning. The avalanche forecast is not as accurate, they only cover the most popular winter climbing areas so a good degree of interpretation is required for a chosen mountain walk. It should always be borne in mind that these are forecasts and are never guaranteed. If the wind direction or temperature at a certain altitude is inaccurate then the avalanche forecast is also likely to be inaccurate.

It is important to start planning a mountain walk in winter at least a week out so you can get read into what is happening in the snow pack and the possible planning implications for your route. A change of wind direction even without any precipitation can blow snow off one slope an onto another that the day before held little risk of avalanche. The Scottish Avalanche Information Service SAIS has a lot of educational material, information and forecasts are posted daily. See www.sais.gov.uk

The Mountain Weather Information Service (MWIS) puts the wind speed first in their forecasts. Cold and precipitation although unpleasant don't stop us travelling but wind will. Wind tends to strip the snow off ridges and spurs so they can offer sensible routes free from avalanche risk but can end up with cornices if the sides of the ridge drop off steeply. In good visibility these will be obvious but in poor visibility it is important to keep well away from the edge.

Ski goggles are the most essential piece of kit you can't do any navigation in a blizzard without them. To manage intricate map and compass processes with gloves on, turn your back to the wind, kneel down on one knee and use the other knee as a stable base.

Weekend walkers with a fixed plan are often vulnerable to the vagaries of winter conditions. Most of the Munros can be climbed on a good winter weather day without a risk of being avalanched and with moderate summer navigation skills. As always planning and decision making contribute 75% of the criteria for a successful day out. That includes consideration of much shorter days, heavier equipment, a slower pace in fresh snow and deciding on key points where and when to turn back. Being prepared to turn back is a much more relevant piece of advice in the winter.

Navigation skills need not be a barrier to enjoying the mountain tops. Do the research and make realistic decisions about the route and weather conditions, and as with all things in the hills steady progressions will build solid experience.

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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