Elevation Gain, What to believe?

[Wilford Matt]

So as per title really.
Went out on Thursday and did Hathersage Circuit out of Vertebrate Dark Peak book.
Recorded ride on Trail forks and Outdoor active.

I planned the route on Outdoor Active before I did it so I could refer/follow it while I was out. it said 650 meters of vertical.
At the end of the ride:
Trail forks said 775 meters of vertical
Outdoor active said 534 meters of vertical
However the Vertebrate book says the route is 1020 meters of vertical.
Now i appreciate there will be discrepancies, but surely not the figures that Outdoor active and trail forks produced compared to the book.

Can anyone explain the variation or issue?
What do I believe?

 

[Stihldog]

I have other route-recording apps but I/we mostly use Strava. There’s a lot of info on this app (some useful) and it will forward your recorded data to other apps, or vis-versa.
I seem to hit the elevation benchmark, that I set, each week. If two of us travel the exact same route with each other, the information comparison is slightly different between us. I’m usually 3-5% higher most times.
However, your data variation seems a bit extreme. I’m not sure why this is?

 

[Gary]

Whatever GPS unit you are using and where it is positioned will probably make a difference to your stats too

 

[Wilford Matt]

A bit more detail
Use Samsung S20 FE in a Quadlock mounted above stem.

I think using same device and app could be useful, but even in Trail forks doing same trail I get 100 meters + variation. So consistency seems lacking.

Was wondering more if the Vertebrate book was to believed.

 

[Gary]

I wouldn't place too much importance on the accuracy of your stats. (or your Book's)
So long as you're enjoying the riding it's all good.

If you're after consistency for your own data. Use the same device. mounted in the same place. and just stick to using one App when comparing data.

 

[Gary]

Was wondering more if the Vertebrate book was to believed.

I've never heard of the book. But if it really bothers you you could always try contacting the author and ask how the elevation of the routes was measured and whether it's considered accurate. I'm sure these days through social media/email they won't be too difficult to track down.
If it's not a recent publication my guess would be that it's probably not super accurate.

 

[RustyIron]

Can anyone explain the variation or issue?

Easy peasy... if you're a math savant. But regular folks like us can still "get it." But lets start by admitting that the gps altimeters that we use are not very accurate. But even if they were perfect, your apps would still show variation.

The discrepancy you see is because of the sampling frequency used by the apps. The more frequently you sample the altitude, the greater your accumulated elevation gain will be. For instance, say we sample the altitude twice on the ride, at the beginning and at the end. Your accumulated elevation will be zero. If we sample three times, at the beginning, half way, and end, we might have 500 meters elevation gain. But what about all the smaller hills in between the beginning and the high point? Well, we'll add a couple more data samples, and the accumulated elevation becomes 750 meters. But what about all the little climbs and dips in between the smaller hills?

You can see where this is going. The more frequently we sample, the greater the accumulated elevation gain. If we sampled your ride frequently enough, we could show that you climbed as far as the distance from here to the moon. Alas, we don't control how frequently our apps sample the elevation. But even if we could, we would never be able to agree on how frequently we should sample.

Benoît Mandelbrot explored this paradox in his paper ""How Long Is the Coast of Britain? Statistical Self-Similarity and Fractional Dimension." I'll include a link below that might be helpful.

I use Strava to record my rides, and Trailforks for finding trails. Trailforks consistently shows greater elevation gain. I think they talk about it in one of their FAQ's. And the numbers both these apps show is wildly different from maps from the old days, where someone would hand-draw a route on a topo map and add up all the lines.

A couple friends and I are real data geeks. If we use the same apps and devices, sometimes our Strava reports are accurate to a few feet. Those who use different devices but the same apps usually show different results.

Coastline paradox - Wikipedia

en.wikipedia.org

 

[Wilford Matt]

The book is
Peak District Mountain Biking - Dark Peak Trails written by Jon Barton published by Vertebrate.
They do a few for round the UK I believe

Its more curiosity of what amount of climbing I'm doing. 3 different figures is a little confusing.
Also for I'm trying to work out at approximate range of my bike. The inconsistency won't help between the apps/book and neither will the inconsistency within an app - for example. I did the same trail twice, one time it read 250 meters the next 370 meters
But its no problem.

 

[B1rdie]

Strava is by far the most used worldwide for performance comparison, if there are riders recording theyr routes on the area, the data from this app is reliable.

 

[Zimmerframe]

Strava is by far the most used worldwide for performance comparison, if there are riders recording theyr routes on the area, the data from this app is reliable.

As he says.

You don't have to make your strava rides public. So you can run it in parallel with whatever over app you have/prefer and still get the data.

If you're using a phone, make sure all the power saving is turned off for those apps and GPS accuracy is set to high. Otherwise you'll get lots of false readings.

Unless you have a device with a barometric altimeter, strava will more often than not use it's own topographical data and work out your altitudes based on where you went - rather than using the GPS figures, which sometimes can be hit and miss.