GT2014/15 - Don't Follow the Lights

Ghaz, how do you measure your distances for each day? They seem excessive, even taking the side-trips to Khulus into account. For example, the normal hiking distance from Injisuthi Summit Cave to where you camped behind Erskine, Bond and Potterill is 14km. Surely you didn't do 13km extra bagging Khulus?



Forgive me for being a pedant, but it's this sort of "rounding-up" that had everybody believing the GT was 260km long for many years. The scenic route is more like 230km with the record route being 210km.

Stijn wrote: Ghaz, how do you measure your distances for each day?

It is as per the GPS track. It is recording with relatively high frequency, so zig-zagging up a hill could make a difference to distance. In total we did 42km more than expected, which I think is quite plausible, especially with having done just over 2km extra to do Popple and Auditor, the walk up the 2 Rwanqa peaks added a lot etc.

My GPS went with me up all the khulus (although my pack didn't always).

As the crow flies (according to GE) it is roughly 12km from UI Cave to Durnford Camp. We most certainly did not do this route in a straight line!

No, but you also almost certainly did not double it...

Are there not perhaps spikes in your GPS track when the GPS is hunting for signal? This can often add lots of false distance.

This is the 23km track from UI Cave to Durnford Camp


I saved and cleared when I set up my tent, but we did a further 4km (which I have as a separate track) from doing Bond, Potterill and Erskine. The deviations are Trojan Wall, Popple, Auditor, Bannerman Face and Thumb Spur - so no funnies there. You can cut a lot of distance by going over the Sanqebethu saddle, dropping down to the Langalibalele River and going straight up the other side - you can see the massive bulge to the right for the longer alternative route we used.

I’m commenting of the apparent distance discrepancy that Stijn pointed to between Ghaz’s GPS distance for the day and what is thought to be more the norm for the GT. Let’s assume that Ghaz’z GPS is doing its job correctly (that should be easy enough to check in any case). We might be looking at the real difference in the track taken by someone with a heavy bag (22 kg +) versus a light and fast (record) route on the GT with a little day pack. The difference will derive from more than the absolute path taken by a person.

Suppose two people are doing the GT, each with the same GPS sampling at the same frequency. Suppose they are going between the same points, A and B. The heavily loaded, slower moving person will have her/his position sampled more often by the GPS between A and B than the fast moving, light-packing hiker given the same sampling rate because the lighter hiker is on the route for less time. The track of the slower moving person will therefore contain a lot more detail and their path, even if identical to that of the heavily loaded hiker, will be longer. This idea is captured by the ‘coastline paradox’ question, the idea that the coastline of an island is of infinite length. The coastline length depends on the detail with which you choose to measure it. The more detail, the longer the coastline. The less the detail, the more straight lines, the shorter the distance. The idea stems from Lewis Fry Richardson, the father of modern weather forecasting. Seminal work on the subject was done by Mandelbrot and is bound up in the branch of maths called fractals. So that could be one explanation for the difference in distance noted by Ghaz and Stijn.

The other contributor Ghaz has already pointed out. A heavily laden hiker does not take the same path as a lightly loaded, fast moving hiker. The heavily loaded hiker zig-zags more and also takes smaller steps which themselves are indirect.

If Ghaz’s GPS is reporting an accurate figure, then we might be looking at the price paid for travelling heavy. It is not only the case that one carries a heavier load but also that one has to walk a lot further.

Interesting theory Tiska. I know I didn't take the most direct line up the hills. With a light pack I would probably take a more direct line up the ridges, but even with all my plans to stay light (such as never carrying more than 750ml of water and taking almost no clothes), my pack did start out heavier than it has ever been (22kg). While my pack would not be abnormally heavy for many people, I rarely hike with more than 12kg, 15kg for a long hike with a tent. We all had to start with enough food to reach Sani in 10 days.

{Spoiler Alert} The GT I did in 2012 was 230km total (as per Tony Marshal's GPS), this one totaled 291km. About 15km of that is due to taking Knuckles Traverse Pass and Bushman's Nek Pass. 46km for 51 khulus sounds like a lot until you consider that we did the Rwanqa's, Botlolong/Ships/Champagne, Carbineers and Mzimude Peaks as separate trips after setting up camp. Mafadi Ridge, Ntonjelana khulus, Icidi Back Ridge etc all took very wide inefficient lines to bag khulus. We did lots of the middle section in the mist, so, for example, we walked the entire way around Redi rather than the much easier route over the top. We even slogged up Walkers Peak, which adds over 1.5km on its own.

The last part of our trip will be up some time soon. But I won't have a chance to write this before the second half of next week.

ghaznavid wrote: Interesting theory Tiska. I know I didn't take the most direct line up the hills. With a light pack I would probably take a more direct line up the ridges,

And with a super-light daypack on a GT record attempt, the line would probably be close to direct.

As Ghaz has pointed out, its an imperfect experiment given that the Khulu bagging is thrown in. It would be interesting to get a cleaner estimate on the percentage distance added by track suitable for a laden, multi-day trip versus super-light, direct line.

ghaznavid wrote: With a light pack I would probably take a more direct line up the ridges, but even with all my plans to stay light (such as never carrying more than 750ml of water and taking almost no clothes), my pack did start out heavier than it has ever been (22kg). While my pack would not be abnormally heavy for many people, I rarely hike with more than 12kg, 15kg for a long hike with a tent. We all had to start with enough food to reach Sani in 10 days.

And just for the record Ghaz, my contribution was no criticism of the weight of your bag! 22 kg for such a multi-day trip is light.

mnt_tiska wrote: And just for the record Ghaz, my contribution was no criticism of the weight of your bag! 22 kg for such a multi-day trip is light.

Not taken as criticism.

Here's a bit more on the fractals as they apply to the distance issue:

"
Richardson decided to search for a relation between the probability of two countries going to war and the length of their common border. However, while collecting data, he found that there was considerable variation in the various published lengths of international borders. For example, that between Spain and Portugal was variously quoted as 987 or 1214 km, and that between the Netherlands and Belgium as 380 or 449 km.
The reason for these inconsistencies is the "coastline paradox". Suppose the coast of Britain is measured using a 200 km ruler, specifying that both ends of the ruler must touch the coast. Now cut the ruler in half and repeat the measurement, then repeat.

Notice that the smaller the ruler, the longer the resulting coastline. It might be supposed that these values would converge to a finite number representing the "true" length of the coastline. However, Richardson demonstrated that this is not the case: the measured length of coastlines, and other natural features, increases without limit as the unit of measurement is made smaller. This is known nowadays as the Richardson effect.

At the time, Richardson's research was ignored by the scientific community. Today, it is considered an element of the beginning of the modern study of fractals. Richardson's research was quoted by mathematician Benoît Mandelbrot in his 1967 paper How Long Is the Coast of Britain? Richardson identified a value (between 1 and 2) that would describe the changes (with increasing measurement detail) in observed complexity for a particular coastline; this value served as a model for the concept of fractal dimension.
"