There are several other names for this travel time estimation technique, but the basics of the technique are:
* For every 5km of easy going, allow 1 hour
* For every 3km of easy scrambling, allow 1 hour
* For every 1km of rough land, deep sand, soft snow or thick bush, allow 1 hour
* Add an extra hour for every 500m up (cumulative)
* Add an extra hour for every 1000m down (cumulative)
* Add an extra hour for every five hours, to allow for fatigue.
For example, take our hike up Mt. Taylor. We will be travelling about four kilometres over clear terrain. So allow one hour for that. We will be climbing about 200m, then coming back down 200m, so allow an extra half hour for that. We won't be travelling for a long time, so there is no allowance for fatigue.
The total travelling time is therefore 2 hours. This is a very pessimistic approximation, as I have done the complete trip in under half an hour - but that is with no pack. Once you do the walk with a pack on, in rough country, on fire trails rather than on open road, your speed will start to drop a little.
Note that not everyone can maintain a cracking pace of 5km/h with an 18kg pack on their backs! You will need to adjust this rule to suit yourself and your hiking partner or group.
The best way to do this is to find a day hike close to you, get the topographic map relative to that area, and do the hike. While you are doing that hike, time how long it takes you to get up hills, down hills and along straights. Once you have done that, calculate your straight and level travelling speed. Use the time it took you to climb the hill to calculate the "up climb" adjustment. Use the time it took you to climb down the hill to calculate the "down climb" adjustment. When you have finished, apply Naismith's rule to your hike and see if you get within 5% of your actual travelling time and checkpoint times. Keep adjusting the figures in the rule to suit you.
Peter Shave (25 Jul 2006)