Staying found - The kit

• Map: a good map is the single most important piece of equipment. In decent conditions a map is often all you need. With no map, you might as well leave everything else at home as well. For off-piste use, the scale needs to be 1:50,000 or (ideally) 1:25,000. and the map must have clear contour lines - ideally spaced no more than 10m apart. Many of the Swiss and French maps mark recommended ski routes and show areas of crevasse and icefall.
  
• Compass: a compass is a device for telling you which way (magnetic ) North lies. Compasses can be mechanical with a small magnetic needle suspended in alcohol or electronic. Many of the more sophisticated watches and altimeters (such as those made by Suunto or Casio) now incorporate electronic compasses which are good for general direction finding. But you really need a good quality mechanical compass in order to be able to take bearings off a map.
  
• Altimeter: an altimeter is a device which measures your vertical height. Altimeters work by measuring barometric pressure (which reduces with altitude) and can double up as barometers to give some indication of changes in weather conditions. Mechanical barometers are still available, but for navigation purposes the wristwatch electronic ones (made by Casio and Suunto) are the ones to go for. These are usefully accurate, relatively cheap, and have lots of additional features not available on a mechanical device. Whilst an altimeter is a useful nice to have in traditional navigation, it is an absolute must have off-piste where knowing your vertical height is often the only way to pinpoint a location.

Nice to have

Other stuff you might carry includes:

• GPS: a GPS is an incredibly clever electronic device (originally developed by the US military) which gives an exact location anywhere in the world. GPS works by picking up signals from a series of 24 satellites orbiting the Earth. By picking up signals from 4 or more satellites, the GPS can work out the distance from each one and (by a complex process of triangulation) pinpoint its location on the earth's surface. Units currently on the market weigh as little as 150g, fit easily into the palm of a hand, give a fix anywhere in the world to within fifteen meters or so, and contain a host of other useful features such as maps and route finding software. Advantages: accurate, very precise, requires no skill to use, works at night or in a whiteout. In theory, you can simply programme in the checkpoints on your route and just follow the direction it points! Disadvantages: needs a clear view of the sky - they don't work in steep valleys, indoors or in thick forest, or when the batteries go flat (the usual problem). Never rely on a GPS as your sole means of navigation.
• Guide book: many popular climbing routes, ski touring routes, and off piste runs are described in guide books whose route descriptions can be very helpful. Advantages: can help to avoid confusion at difficult points and recommend the best routes to follow: Disadvantages: quality varies hugely. Not a substitute for good navigation.
• Flares: not strictly a navigation tool but can be helpful in alerting a search party to your location (especially at night). You can obtain pen sized spring loaded flare gun launchers with flares than are only a couple of centimetres long and weight almost nothing. Advantages: can speed up a rescue, especially at night. Disadvantages: needs to be some-one near enough to see your flares. Also can't be carried on aeroplanes so may end up having to buy a new pack every trip.