William.W. Naismith was a founder of the Scottish Mountaineering Club. In 1892, he worked out a way of estimating the length of time it would take to cover a walking route, including ascents and descents. His simple rule was to "allow 1 hour for every 3 miles forward, plus ½ hour for every 1000 feet of ascent". He was obviously a fast walker! Note that Naismith made no allowance for descending.
Since then, verious other people have refined the rule, taking into account personal fitness, weight carried, the nature of the terrain, etc.
For a D of E expedition, a good starting point would be 4 km per hour walking speed and 300 m per hour ascent speed.
If your walking speed (i.e. on flat ground) is set at 4 km per hour, that would equal 1 km per 15 mins or 100 metres per 1½ mins. If you are a slow walker, this could be adapted to your pace, e.g. to 3 km per hour (1 km per 20 mins or 100 metres per 2 mins.).
If your speed of ascent is set at 300 m per hour, that would equal 100 metres per 20 mins or 10 metres per 2 mins. A very fit group might manage 400 metres per hour (100 metres per 15 minutes or 10 metres per 1½ mins.).
You then need to add 10 mins per hour for stops (e.g. putting on/taking off waterproofs, comfort breaks, navigation, making notes, etc.). You also need to allow half an hour hour for lunch.
Once all these elements are added together, you arrive at a total time for each section of your walk and for the whole expedition.
On your practice expedition, you will make a note of your arrival times at all points on the route card. These can then be used to calculate what variation of Naismith's Rule applies to you so that you can accurately plan your qualifying expedition. Having said that, adverse weather conditions can cause even the most carefully planned day's walking to be significantly adrift of the route card timings.
Click here to see how use Naismith's formula in the construction of your route card.