Navigation - Time and Distance

One of the most difficult aspects of navigation is to know how fast you are travelling when on foot over various terrains. Being able to measure these things yourself will make a massive difference to being safe and staying on track.

In the same way that a car Speedo is useless unless it is calibrated you will also need to calibrate yourself. Once calibrated you can then measure distance travelled in various conditons.

• Calibration - 1Km Walk
• Calibration - 100m pace counting
• Calibration - Gradients (Naismith's Rule)
• Calibration - rough ground
• Measurement - putting it all together

Calibration - 1Km (or 1 Mile) Walk

The first calibration that you need is to work out how long it takes you to walk for a set distance (1Km or 1Mi).

The best way to do this is to wear your normal walking gear and carry a normal pack weight - since both of these will alter your speed. You then need to measure out the distance (1Km) on easy flattish-ground - maybe the street or a metalled path and time yourself using a stopwatch when walking at normal pace.

If you have a GPS or are good at measuring distance on a map then you can easily incorporate this measurement into one of your walks.

An alternative way to do this is if you know the exact distance of an easy walk in which case you simply do the walk and time it (to within a few minutes). You then divide the number of minutes taken by distance (in Km or Mi) and you are done.

I know that over easy ground with my normal pack on I will cover 1Km in 11 minutes.

Calibration - Pace Counting on a 100M Walk

The second (and more useful) calibration is to work out how many double-steps it takes you to cover a fixed distance of 100M on average.

A double-step is counted by choosing one leg (left or right) and whenver that leg is placed in the front the step is counted - so the other leg is always being ignored. Double-step counting is a lot easier to do than step counting simply because it is happening half as fast!

Again, it is best to do this wearing your normal gear since this does have a slight effect on your pacing.

What you need to do is accurately measure out 100M by either finding two items that 100M apart (such as marks on a school running track) or by borrowing/buying a 30M+ tape measure and measuring the distance yourself. You could also try to use a GPS.

With the distance measured out you now walk back and forth between the two marks a couple of times until you have worked out an average number of double-paces.

For instance I know that I average 57 double paces to cover 100M under normal conditions.

Calibration - Gradients ( Naismith's Rule)

As you know the real world is not flat. So far we have discussed calibration of how you cover distance on flat ground. Since you will be taking measurements from a map which is flat and transferring it to the ground which is not flat you will need to make adjustments for both the actual time and distance covered.

In practice you do not want to do lots of calculations whilst out walking and so there are some corrections that can be made that are good enough. The first famous one is Naismith's Rule (Wikipedia) which gives a rough estimate that takes into account height gained (or lost) when walking for a typical person.

The simplest version of the rule is to say that for every 10m of height gained add 1 minute to your estimated journey time which in practice means that you can just count contour lines!!!!

What this means in practice is that I can look at a map, measure (or estimate) the distance and then just add on 1 minute for every contour line that I can see. If I am being lazy (usual) then I will look at the nearest contour line to the start and the finish and take the difference between the two of them in metres and divide by 10. Mostly this will be good enough.

When descending then obviously I will be travelling faster than ascending (usually) and so I might use Naismith's rule again but halve it.

Calibration - Rough Ground

This one is much more difficult to do and in reality comes with practice.

It should be obvious that walking accross a boulder field or up a scree slope or accross peat bog will be much more difficult than walking along a simple path.

Rough ground tends to mean that you take shorter paces (as does going uphill) and it tends to mean that you take longer to cover the same distance and so your 'flat ground' measurements will be too low.

Therefore you need to estimate how much the rough ground is slowing you down (or making you take shorter steps) and then compensate for this in your navigation.

In reality you just learn to do this over time. The key point is to remember that your distance estimates based on steps will be too optimistic and the actual may be anything between 10% and 100% (or more wrong).

On rough ground I generally find that counting paces is more reliable than measuring time.

Measurement - walking the walk

Measurement - Long Distance

I know from my calibration exercises that it takes me 11 minutes to walk 1Km. If I am travelling 1 or more Km between landmarks then what I do is use a countdown timer on my watch which has been preset to 11 minutes. All I then need to do is to count and remember how often I reset the alarm.

Measurement - Shorter Distances (<2Km)

For this I will use pace counting. Let's say that I have chosen a bearing to my next key landmark and that the landmark is 450m away.

What I will do is use my left fingers to count 100,200,300,400 metres. So, I will count 57 paces and then unwind one finger from my closed hand. I will count from zero for another 57 paces and unwind a second finger. I will do this for the first 400m. I will now plan on counting another 30 paces but I will also be keeping a careful eye out for my landmark whilst doing this. If I get to 450m and I still cannot see my landmark then I may consider walking on a bit further on the same bearing (if visibility is good) and rechecking my map and also I might consider a spiral search (if visibility is bad).

The key point is that I will start looking for the landmark slightly early and based on the ground I will assume that I will slightly undershoot or overshoot. In general my navigation will be accurate and I will be accurate to within a few metres. It just takes practice!

The last time that I checked my pacing I did it between two well defined landmarks that were 750m apart and I used a GPS to measure the distance travelled between points. It was an easy path and my pacing was spot on!

Measurement - Ranger Beads / Pacer Beads

In practice it can be difficult to keep track of 100m legs using just the fingers of one hand - either you run out of fingers or you need to use your hand for something else. This is where Ranger Beads / Pacer Beads can help.

Really they are nothing more than a simple abacus on a string. A typical set of Ranger beads consists of a piece of para cord doubled up with two sets of beads on it - one set of 9 and one set of 4. Each on of the set of 9 beads represents 100m walked and each of the 4 represent 1Km walked.

Every time you walk 100m you move one of the 9 beads down the string. When you have moved all 9 then the next time you move one of the 4 beads down and move all beads up. In this way you can count of 5Km with accuracy.

Ranger beads are a little difficult to find in shops but it is easy to make your own.