Most navigation errors are not errors of direction but of distance. We hold a good bearing, walk confidently, and then turn off at the wrong stream because we did not know how far we had come. Two old techniques answer the question “how far?” without any electronics: counting paces for short legs and timing for long ones. Both are approximate, both are improvable with practice, and together they turn a bearing into a position.
Why distance is the hard half
On a clear day, distance takes care of itself; we see the col and walk to it. In cloud, forest or darkness the only way to know we have reached a feature is to know how far we have travelled since the last one. A compass leg of 800 m through fog with the instruction “turn left at the second stream” is only as good as our estimate of 800 m. If we undercount, we turn at a gully that is not on the map. If we overcount, we walk past the stream and keep going, and the map appears to stop making sense. Pacing and timing give us a running estimate of where we are along the line.
Counting double paces
A pace in navigation is a double step: count every time the same foot, say the left, hits the ground. On flat, easy terrain most adults take between 60 and 70 double paces per 100 m (about 55 to 64 per 100 yards), depending on leg length and stride. The number is personal and must be measured, not guessed. Find a stretch of level path of known length, a running track or a measured 100 m on a road, walk it at a normal hill pace three times and average the count. That figure is our baseline.
The baseline changes with the ground. Going uphill the stride shortens and the count per 100 m rises, typically by 10 to 20 percent on a moderate slope and more on a steep one. Downhill the stride can lengthen slightly on gentle gradients but shortens again on steep or loose ground. Deep heather, bog, snow and boulder fields all add paces. A heavy pack adds paces. Fatigue at the end of the day adds paces. Good navigators keep a small table in the map case: flat, gentle up, steep up, gentle down, rough, snow, each with its own count.
Keeping the count is a mechanical problem. Beyond a few hundred metres the mind wanders, so we use a physical tally: a set of ten beads on a cord, sliding one down every 100 m, or moving a small stone from one pocket to another. On a leg of 600 m we know we should arrive at the target when the sixth bead drops. If the feature is not there, we have information, not confusion: we are within a few tens of metres of the right place, and we begin a short deliberate search rather than pressing on.
Pacing works best on legs under about a kilometre. Beyond that the accumulated error, typically 5 to 10 percent, grows large enough that a half-hour of counting yields a position known only to within 100 m, and timing becomes the better tool.
Naismith’s rule and its corrections
The classic timing formula was proposed by a Scottish mountaineer in the 1890s and is still the starting point for every route card. In its original form it allows one hour for every 5 km (about 3 miles) of horizontal distance, plus one hour for every 600 m (roughly 2,000 ft) of ascent. In practical units that is 12 minutes per kilometre plus 10 minutes per 100 m of climb, or 20 minutes per mile plus 30 minutes per 1,000 ft.
The rule assumes a fit walker, a reasonable path and no pack to speak of, which is to say it describes a fast day. Several corrections have been proposed over the decades and the most useful are simple. Descent is not free: on gentle slopes it is slightly faster than flat walking, but on steep ground below about 20 degrees it costs time, and a common adjustment adds 10 minutes per 300 m of steep descent. Rough ground, snow and bushwhacking can multiply the whole estimate by 1.5 or more. A fully loaded pack of 15 kg (33 lb) adds roughly a quarter to the time. Stops for food, photographs and layer changes are not in the formula at all and can easily add an hour to a summer day.
A widely used alternative applies a fitness factor: divide the Naismith time by a personal ratio derived from timed walks. Someone who consistently completes routes in 80 percent of the calculated time can plan with that figure, while a group moves at the speed of its slowest member and should plan accordingly.
Timing a single leg
Timing at the scale of a leg uses a personal speed rather than the day-long average. Most walkers cover level ground at 4 to 5 km/h (2.5 to 3 mph) unloaded; in poor visibility, on a bearing and with a pack, 3 km/h (about 2 mph) is more realistic, which is 2 minutes per 100 m. Add half a minute to a minute for every 10 m contour crossed uphill. For a leg of 700 m with 60 m of climb at 3 km/h, we expect 14 minutes plus about 5 for the ascent, around 19 minutes. We note the start time on the watch, and if the target feature has not appeared by 22 or 23 minutes we stop and reassess rather than walking on hopefully.
The discipline is to write the estimate down before starting the leg. An estimate made after the fact always agrees with wherever we happen to be.
Combining the two into a position
Bearing gives direction, pacing or timing gives distance, and together they place us on the map. On a route card each leg carries five entries: start point, bearing, distance, ascent, and estimated time or pace count. The card is built at home, when the mind is fresh, and read on the hill, when it is not. A few practices sharpen the method over a season:
- Recalibrate the pace count every few months and after any change of boots or fitness.
- Pace short legs and time long ones; never rely on pacing beyond a kilometre.
- Write the expected time on the card and set a limit beyond which the leg is abandoned.
- Reset the count and the watch at every confirmed feature, so errors do not accumulate.
- Practise on clear days, when the target is visible and the count can be checked.
The reward for this small bookkeeping is a peculiar calm. When the cloud comes down and the phone is cold, we know not only which way to walk but how long to walk it, and when to stop and look around. That knowledge is what separates a navigator from a walker with a compass.