Navigation in difficult conditions
Conditions such as poor visibility, foul weather, thick scrub, logs, cliffs and steep or uneven slopes make it very difficult to maintain exact bearings and to judge distances travelled. The competent leader must have the ability to navigate in these conditions, despite fatigue or physical discomfort, with obvious confidence and with a minimum of conscious effort. If navigation is difficult, you could nominate a temporary party manager to look after the group for as long as you need to concentrate on the navigation.
Poor visibility may be caused by fog, heavy rain, whiteout, thick scrub or darkness. This may be forced upon the group by a sudden change in weather or may be due to a deliberate decision taken by the leader. For example, the leader may have purposely included night navigation (perhaps to arrive on the summit of a nearby mountain for sunrise), or has assessed the party as having sufficient experience to continue in the dark. Travelling at night increases the difficulty of navigation and the risk of injury to party members. The leader should consider carefully whether travelling at night is worth the added risk.
Under conditions of poor or zero visibility, do not rely on a sense of direction. Even when following a well-defined feature, consult your compass frequently and heed it. It is advisable to stick to well-defined features as much as possible, e.g. tracks, sharp ridges and spurs. When this is not possible, compass traverses must be resorted to, but these should be kept as short as possible and used to proceed from one well defined point to another. Make full use of the navigational techniques such as catching features, attack points, aiming off, handrails and methods of negotiating obstacles. If each stage of the compass traverse is short and terminates at a well-defined point, then any straying off course can be corrected without difficulty.
In poor visibility (e.g. less than 100 m) on a flat featureless area, the party should travel in single file with the navigator three or four places from the front. Appropriate corrections to the compass line of march can be called, using the front person as the aiming point.
When following snowpoles when the next pole cannot be seen, the ‘long cord’ method should be adopted. This involves sending one person out with the end of a cord which is long enough to reach the next snowpole (usually 40 m). The person moves in an arc until the pole is found, then the remainder of the party follow (Gatty 1977).
To determine distance travelled under conditions of poor to zero visibility, pace counting may be useful. A pace means a double step, i.e. you count each time you put your right (or your left) foot down. For a person of around 1.8 m height carrying a pack on level ground, pace length would be about 1.5 m, which makes about 660 paces to a kilometre. It would be very unusual to pace count for longer distances than this. People shorter than 1.8 m will tend to have shorter paces, and taller people longer ones. Navigation in difficult conditions requires practice, which is really only gained by going out there when the conditions are difficult.