Navigation for Skiers - Part 3 (2019)
In the first two parts of this series we looked at different scales of maps and the information that we can get from contour lines. In this part, we'll take a look at the compass and how to use it.
The best type of compass to buy for navigating in the mountains and doing exams is a baseplate compass, made by a good manufacturer, such as Silva or Suunto. Compasses can seem to be expensive but they're a precision instrument and will last a long time, if you take care of them. If you're going to be doing a lot of navigating in the mountains, either with a compass or GPS, ski gloves are often too bulky. Get some thin gloves, preferably with a grippy texture on the palms and fingers. Wearing these inside some thin shells is a good way to keep your fingers warm when working in bad weather.
"Conscience is a man's compass."
Vincent van Goch never had to navigate in a whiteout.
The baseplate of the compass should fit comfortably in your hand. BASI and the MLTB recommend the Silva Expedition type but I find it uncomfortable and use the smaller Silva Ranger instead. Any smaller baseplate limits what you can measure off the map. The magnifying glass can be incredibly useful for spotting small features on the map and also for looking at snow crystals. Some Suunto models have large magnifiers on their baseplates.
Get some cord and a small karabiner, like the ones that come with ski gloves and put them onto your compass. You can clip the compass onto a zip on your jacket or onto you backpack. This means that you can let go of your compass and not drop it and ski over it nor tread on it & smash it nor lose it in powder snow.
One of the first things to do when navigating is to orientate your map. This means to turn the map so that it is the same way around as the real world. The convention for most maps is that if you are reading the place names the right way up, then map north is at the top of the page. You need to turn your map so that its north points to north in the real world. One way to do this is to put you compass on the map and turn the whole lot around until the compass needle and map north match. A quicker and more skilful way to do this, is to use features such as valleys and summits and line your map up with these, without the need for a compass.
The main use for a compass is to take bearings from the map and then to follow them in the real world. This video from Mountaineering Ireland explains the process really well. Something to be aware of is that magnetic north isn't necessarily in the same direction as north on your map. In Iceland the magnetic declination is currently around -12° and in Patagonia it ranges from +6°to +14°. You can find your local declination on the key to your map, or sometimes from your GPS. Fortunately, the declination for most of Europe is only 1°or 2°, so it's currently not a problem. However, as the Earth's molten iron core flows around, this will change; so don't forget about it in the future!
Other things to consider when using bearings include how many sections or "legs" do you need and how long should they be? The further you travel with just a few degrees of error, the further off to the side of your destination you will be (above left). Six degrees of error for 1km distance will put you 100m off target. Shorter legs have smaller errors. If you want to get to the other side of a combe (or cwm or corrie), taking a bearing straight there might lead you over a cliff. It's better to break the journey into smaller chunks (above right). It's also worthwhile thinking about the scale of the map and how big your target is. Are you likely to find it in poor visibility and under the snow? Do you need to choose a different one?
"And don't forget aspect of slope - that's the best card in the hand."
Peter Cliff, Mountain Guide & Ski Instructor, "Mountain Navigation"
Aspect of slope is one of the most useful compass techniques for skiers. Imagine that you're skiing down a smooth cone, like an Andean volcano, in poor visibility. To find out which side you're skiing down, first take a bearing down the fall-line. You might need to roll a snowball down the hill to see this. Then put your compass onto the map and line up the north-south lines in the capsule with those on the map. Move the compass around the hill that you're on, until the direction of travel arrow on the baseplate crosses the contour lines at 90°. This is the side or aspect of the slope that you are on.
Once you get into navigation, you'll want to know more about things like aspect of slope, attack points, aiming off, handrails and catching features. Mountain Training UK's "Navigation in the Mountains" covers all of this and more. Another book that's well worth buying is Bruce Goodlad's "Ski Touring". It covers all aspects of the activity and has a chapter on navigation techniques for skiers. In the next part of this series, we'll take a look a measuring how far you've travelled using pacings, timings and altimeters.