Navigation for Skiers - Part 4 (2019)
In the first three parts of this series we've taken a brief look at different scales of map, what contour lines mean and using a compass. In this part we'll think about how you can measure the distance that you've travelled over the ground, without having to lay out a tape measure across the mountains.
Timings can be an incredibly useful tool for tracking your progress as you skin up a hill. This can be both on the macro-scale, e.g. to make sure you've enough time to get home before it's dark and on a micro-scale, e.g. to have an idea of how long the next section should take you. In the second case, we can use timings as a sort of catching feature. If you're navigating to the top of a hill and haven't got there by you E.T.A., it's an opportunity to stop and re-evaluate. Has the terrain or snow been slower going than you anticipated? What do tools such as the shape or aspect of the slope tell you about where you are?
Things can get very mathematical very quickly when we start to navigate seriously. The flipside of the chart in Part 1 has a table of distances and times for three different speeds of travel. You can keep a laminated copy of this, either on your compass string or in your mapcase.
But which speed on our chart should we use? It's a good idea to have some checklists that you always do before you set out: transceiver checks, resetting your altimeter and checking your watch for your departure time. Different groups move at different speeds over different snow and terrain. You might be averaging a faster or slower speed than you planned. For instance breaking trail is a lot slower than skinning along a ready-made track or hard snow. Checking your watch at various points on your route means that you get an idea of how fast your group is moving on that day. This enables you to make a more accurate estimate of how long the next sections will take.
Another way to measure our progress as we skin along is to count our paces. This can be a very useful technique if we're doing short sections of a few hundred metres and need to measure distances as precisely as we can. Before we can use this technique, we need to set a baseline of how many paces we take to cover 100m. We also need to be aware of how the number can increase as the terrain changes.
To set your baseline, you'll need to find somewhere fairly flat. Use a tape measure or your rope or an accurate GPS to measure 100m. Walk up and down it a few times, counting each time you put your left foot down. Most people take between 60 to 70 double paces for 100m. Try it skinning: is there a difference? Is there difference in deeper snow? Eventually you can make yourself a table of how many double paces you need to cover 25m, 50m & 100m in different conditions. Print it, laminate it and add it to your mapcase or compass string for reference.
Another technique that helps to reduce the amount of mental arithmetic you need to do, starts by adding some toggles to your compass string, like the ones in the photo in Part 3. If your next section is 375m long, working out the total number of paces for the leg can be tricky. Instead, walk your first 100m and slide a toggle along the string. Do the same after each 100m chunk and then pace the final 75m. If you have stop along the way, remember the number of paces you were at and the toggles will tell you how many hundreds of metres you've travelled, so you can start again.
One of the places where pacing fails is if you're not walking in a straight line: for instance if the slope is so steep that you're traversing and doing kick-turns. This where using timings can be important. It can also be a warning. If you're doing kick turns, the terrain is steepening into 30° slopes, which is where there can be a heightened avalanche hazard. If the visibility is so bad that you're using bearings and pacings to navigate, how much information about the avalanche picture can you gather and how safe are you? Is time to turn around?
Altimeters use the principle that air pressure reduces as altitude increases. The United Kingdom is set on a series of islands, in the Atlantic Ocean, with weather systems constantly tracking across it. This means that there can be large variations in atmospheric pressure each day. Keeping an altimeter updated would be a problem and so people don't generally use altimeters for navigating in the British hills. The weather in the Alps is usually more settled and so altimeters are a more useful and common tool. However, it's good practice to update your altimeter whenever you get to a known altitude.
So far we've covered techniques for measuring distance going uphill but you can't count your paces skiing downhill and timings can vary wildly. The standard technique when skiing downhill is to follow a bearing to an altitude. Where the bearing crosses the contour line is where you should be. Thinking back to the previous parts of series, it's a good idea to pick an altitude with some distinctive features, e.g. change in slope shape, to help you confirm that you've arrived in the right place.
GPS has revolutionised mountain navigation. So long as you have a satellite signal and batteries, the computer will do the maths for you and even show you exactly where you are on the map. However, GPS is not a panacea: it's another tool in your kit and it's important to understand how it works and what its limitations are. If the GPS breaks down, then knowing that you can rely on traditional methods to get you home gives you greater freedom.
This series has been a brief introduction to some of the techniques of navigating in the mountains and on skis. It can be difficult to become fluent in them but also incredibly rewarding. If you can navigate accurately in fog then you can also navigate at night, which opens up another world of adventures in the hills. Navigation also opens up other opportunities such trail running or orienteering or gaining other qualifications to work in the mountains, such as the International Mountain Leader. Or perhaps you just want to use a map to spot new and beautiful places to ski. Wherever you end up navigating, have fun in the hills!