Pacing, timing or ticking off – measuring distances when navigating on foot
On our navigation courses we always end up coming around to the subject of distance. Indeed, it’s one of the ‘D’s of navigation and unless you intend to just stand still and survey the surrounding countryside you’ll need to deal with the problem of measuring distance both on the map and on foot at some point or another.
There are three ways that we cover in depth on the EST Framework navigation courses – ‘pacing‘, ‘timing‘ and the enigmatically named ‘ticking off‘. They each have their merits, but also a few drawbacks. Like pretty much every other navigational technique – they are just a tool in the toolkit, and it is up to you to select the right one for the right task.
When we talk about ‘pacing’ with regard to measuring distances when walking we’re actually talking about ‘double-paces’. A double-pace (DP) is just two consecutive walking strides – so if your first step is with your left foot forward then you would count every time your right foot hits the ground for your double-pace count.
When we’re relaxed and walking normally humans are quite good at maintaining a steady rhythm and stride length. This means that we can rely on that regular pacing to measure out distances along paths or across open ground with a reasonable amount of accuracy.
Measuring over 100m segments
If you know how many double-paces (DP) it takes you to walk 100m (mine is 60DP, but I regularly walk with people who could range between 55 and 75DP) then you can use that number to measure either multiples of 100m, or distances shorter than 100m.
So if I measure out a navigation leg as being 120m then it SHOULD take me 72DP to complete that distance (60DP for 100m then 12DP for 25m).
When measuring out longer navigation legs there always comes a point where the number of double-paces (DP) you are counting out becomes a bit too much to keep track of – especially when you’re also trying to concentrate on a bearing or moving over rough ground. I try to keep pacing navigation legs as short as possible, and then count in ‘sets’ of 100m. So if I need to walk for 300m then I will count to 60DP three times, rather than trying to count to 180DP in one go.
Some people make use of counting aids, such as a row of beads on a length of paracord or even knitting and crochet stitch counters! I either use my fingers (at least 5 on each hand) or pick up the relevant number of rocks and throw one away every time I reach 100m.
Working out your Pacing
You need to find a 100m section of flat, easy terrain where you have clear markers at either end. Wear your normal walking boots, rucksack and clothing and walk as normally as you can from one end of your measured distance to another. Make a note of how many double-paces (DP) it took for you to get there, then turn around and walk back the other way. If all is going well then this number should be the same!
Do this another few times and take an average of the number you get to each time you complete 100m. This is now a number you can start to use to measure distances, but check it against other known distances to see if you have worked it out correctly.
- Accurate measuring of distance for shorter navigation legs (less than 500m)
- Walking at variable speeds where stride length is roughly the same
- When accuracy of distance matters more than accuracy of speed
Not So Good For…
- Longer navigation legs
- Walking and talking at the same time
- Very steep or rocky terrain where regular pacing is impossible or lots of zig-zagging occurs
Timing is another accurate method of measuring distances when walking, but requires a bit more in the way of careful calculation and adjustment for different scenarios. It often works when pacing does not (longer distances, difficult ground) but in some ways it requires more mental energy.
William Wilson Naismith – Scottish mountaineer and founding member of the Scottish Mountaineering Club – developed a formula for calculating time over distances when walking in the mountains. It essentially says:
one hour for every 3 miles (5 km) forward, plus an additional hour for every 2,000 feet (600 m) of ascent
A slightly easier way of saying this is:
allow 12 minutes per kilometre, then add 1 minute for every 10m of ascent
The problem that may arise here is – what if you walk faster than 12 min/KM? Or slower? My own pace varies substantially either side of 5km/h depending on the terrain I am walking over, the load I am carrying and even how far I have to travel that day or the task I am completing.
Measuring your pace
As with working out your pacing – you need to find a length of easy, flat ground where you can measure against a known distance. Walk that distance (if you can find somewhere that is 1km or 500m long it will help with the maths) with your normal walking clothing and equipment and time it. Turn around and walk it again in the other direction. Do it at least 3 or 4 times and take the average. Work out how long it will have taken you to walk 1KM and make a note of this. Next – try it out against another set distance and see if you can predict how long it will take for you to complete it.
Ascent and Descent
As a general rule you add 1 minute for every 10m you will ascend within the horizontal distance (i.e. the distance you measure on the map). This accounts for both the extra distance of the slope and slowing down as you work harder to walk uphill. In some extreme cases (running etc) you may want to add in less than 1 minute for 10m, but generally speaking it’s best to adjust your horizontal pace and stick to 1min/10m of ascent.
When descending it’s often best to just stick to the horizontal (map-measured) distance and make no adjustments for the change in elevation. However – if the slope you are descending is very rocky, vegetated or steep then you might need to make an adjustment.
Calibrating for the day
Some people are happy to come up with a figure for their average pace and stick with it, but where possible I prefer to measure how quickly I am moving at the beginning of a trip then base my calculations for the rest of the trip on that figure.
So if I have, for example, a 500m section of flat-ish walking at the start of the day I will make a note of how long it takes for me to complete it then use that figure for my min/KM pace. If I walk that 500m in 4 minutes 30 seconds then it’s likely that I will be moving at 9 minutes per KM for the foreseeable future, and so on.
Next I will work out another short leg (less than 1km) and estimate how long it will take for me to complete it at that pace (still adding in 1 minute for every 10 minutes of vertical ascent).
So if I am walking at 9 minutes per kilometre, and in the next 800m on the map I will ascend 250m then my estimated travel time is going to be around 32 minutes and 12 seconds (7 minutes 12 seconds for the horizontal distance, and 25 minutes for the vertical ascent). If that estimated time is substantially wrong then something has gone wrong somewhere – if my calculations are correct then I need to adjust either the times for the horizontal or vertical distances.
The problem with using timing and average pace for measuring distance is that it relies on fixed figures in a world where there are a lot of variables. Dense vegetation, rocky ground and bogs/swamps can all substantially slow you down – and a stretch of unexpectedly good path or road can allow you to move much faster than expected. For these reasons you should always be ready to use another navigation technique such as a Catch Feature or Handrailing (see below) to make sure you spot any errors creeping in.
- Macro navigation or where accuracy matters less
- Walking along well-defined linear features such as paths or along fencelines
- Working out if you have enough time to complete a certain route/navigation leg
- Walking in a group where you want to be able to talk and not worry too much about counting
Not So Good For…
- Where high-accuracy is crucial
- When you are tired and mathematical calculations are harder
- Where the terrain constantly varies and establishing an average is difficult
This isn’t often mentioned as a way of measuring distance, but if you think about it it’s possibly the technique you will use most often.
‘Ticking Off’ is the navigational term for the process of mentally noting features as you pass them on the ground. You can look at a map and say to yourself:
“OK, I’m going to walk along the edge of this field, cross over a boundary of some kind and then walk on the southern side of a small stream for about 300m. After that I will cross over another stream to the side, climb up a slope with 30m of ascent and then come out onto a plateau.”
That short story adequately describes the route ahead using map features that SHOULD be there on the ground, and you can use it to roughly measure distance. If you have crossed over the boundary of the field and are walking alongside the stream BUT haven’t yet come to the side-stream or the slope then you can at least narrow your position down to a 300m-long stretch of riverbank. And I am willing to bet that you would know if you were closer to the boundary or the stream crossing – so you can maybe narrow your position down to the nearest 150-100m.
Ticking Off is a very broad tool for measuring distance, but if you use it properly it will allow you to narrow things down to a rough area and create a ‘bracket’ of “I have passed this feature but haven’t passed this feature yet, so I must be somewhere between the two“.
Of course, this only works if the features you are looking for actually exist on the ground – fences move, streams dry up and sometimes there are just map errors.
- Terrain where there are lots of easily-identified features
- Linear routes along paths, rivers or fencelines where progress can be checked
- In good weather where position is important but high-accuracy isn’t
Not So Good For…
- Times where high-accuracy is important
- Where it could be easy to confuse similar features
- Where there are few definable features on the ground
No matter which of the three techniques you use to measure distance – it’s wise to have a backup plan. The easiest way to implement this is to identify a ‘Catch Feature’ – something big and obvious that is just beyond the edge of your navigation leg that will immediately alert you if you have gone too far. It could be a fenceline, a river, an obvious change in slope angle (either uphill or downhill) or even a change in vegetation – the edge of a forest maybe.
This is something that you will need to identify on the map before you begin that navigation leg, and maybe even allow for when planning that section of the route. If getting your navigation planning wrong is going to put you in a dangerous situation it’s probably better to take a slightly longer route where any errors can be picked up and fixed straight away than to take the direct route and have errors go unnoticed.
So which is the best?
Pacing, timing and ticking off are all tools in your toolkit. Pacing has the highest accuracy in most cases, but only works well over shorter distances. Timing CAN be very accurate, but you need to put in a lot of work to get there and it’s easy for error to creep in. Ticking Off can work very well, but unless you are stood at the junction of two linear features it’s difficult to be very accurate with it.
Both Pacing and Timing seem to have about 90% accuracy – i.e. you are going to have an error of about 10% each time you use it, even if you are doing it well. 10m of error on 100m is fine, but 50m over 500m can be significant and make the difference between finding the safe descent route or walking off a cliff. No matter which technique you use it’s wise to use i tin conjunction with another navigation tactic – aiming off, a catch feature or even just feature recognition.
Over the course of a navigation-intensive mountain day I will probably use Ticking Off for 80% of the route, Timing for 18% and Pacing for maybe 2% – but that 2% might be the most critical part of the day, such as finding my way from the summit to the correct edge of the plateau for the path I want.