Total ascentFORUMS HOME SEARCH FORUMS

Hi

I recently registered and am finding the site much more user friendly than others. However, I'm also finding that the total ascent displayed for each route is consistantly greater than that calculated for the same routes by other sites. Even route data from CTC shows lower assessments. Is there a reason for this?

Cheers

William 

Hi William - thanks for the nice feedback.  

The total ascent figure will depend on how frequently elevation readings are sampled - less frequently sampled elevation readings will result in lumps and bumps being smoothed out and therefore a lower figure. I suspect the sites you are comparing us with use less frequent, or irregular sampling.  We take elevation readings at regular 30m intervals as a default, with longer intervals for longer routes.

You can see the effect of different elevation intervals with our route profile tool.  Have a look at the following example.  The default elevation interval for this route is 30m, which gives a total ascent of 100m.  However, if you drag the slider on the right to take elevation readings every 300m, this will then give you a total ascent of 65m.

Route Profile for East Quantoxhead Coastal Circuit

Hope that helps.

John

Thanks for the explanation John

I see filtering bumps also makes a difference

Regards

William

And what happens if I upload GPX route with altitude readings from my barometer? Are you using topographic data from your maps or one supplied by my file? I assume you still use same sampling algorithm here

We use global elevation data sampled from space for a consistent apoproach on all routes.  Although baraometric altometers can be more accurate with elevation data than GPS on it's own, we have found that they can still be a long way out - someone recently sent us a sample file for analysis and his device had said he was at 50m above sea level when he was actually next to the sea!

John

Obviously it depends on particular device used as well as technology (Suunto uses FusedAlti, basically calculating the altitude from both barometer as well as GPS, etc.) - however its not what we are discussing here. My personal preference would be allowing the user to choose - keep his own altitude data or use yours. Ether way, thanks for clarifying it for me

The major kind of problem with topographic data could be represented in an example below:

https://www.plotaroute.com/routeprofile/107448

This is a straight bridge over the river and it's steady slope uphill only. Thus the actual ascent is about 61m-35m = 26m give or take. In the same time your numbers of:

- total ascent 43m

- anything with "downhill" or "flat"

- lowest point 18m

It's clear all of them are blantly false. I assume they track the landscape itself and make sense in this regard but nonetheless are completely inappropriate for a cyclist. So for example if we have several bridges over the longer route, this combines to huge error (like this small bridge would also show you some ascent while going in the opposite direction, thus effectively crediting us with ascent while purely descending, etc.)

You're right, there are instances where topographic data can be innaccurate and bridges are a good example.  It would be nice if there was a perfect global source of this data but the main advantage we find is that it enables us to provide a consistent universal approach across all routes.  Hopefully at some point we might be able to add an option for users to make adjustments or corrections where topographic data is wrong but I think this could be quite complicated for us to design and develop and we have lots of development work in the queue, so it's probably not something we can do in the near future.  

John

I've observed that sistematically the total ascent of a ploted route prepared using Plotaroute is greather than the total ascent registered witth Strava when that route is cycled.

I prepared my last route some days ago (id 911997, route name PedalGuia_SpedroCadeira- https://www.plotaroute.com/route/911997?units=km) 118.67Km, total ascent = 2267m. Today we cycled that route (a small deviation of about 2 Km regarding the route planned was in fact done, without significativily change in total ascent - i presume no more than 20 meters), using the navigation App Osmand to follow that route, discharged from plotaroute in GPX file.

I registered the trip using Strava: 121.53 Km, total ascent=2046m, ie, a diference of 221m.

One of the guys registered the trip using Garmin: 120.21 Km, total ascent registered was 2042m

Could plotaroute admin explain me how should i proceed in order to minimize this "deviation"? Is it possible to get more accuracy in the total ascent? How? 

Thank you,

Antonio Ratao

Hi Antonio,

I'm afraid it's pointless trying to compare Total Ascent calculations from different sources, as they all have different methods of calculation. You should really only compare figures from the same source, so that the are calculated in a consistent way.  There is no "correct" or "most accurate" figure for Total Ascent - it depends on the formula used.  Strava probably uses more smoothing than we do, which would account for lower results. We've looked into this a lot in the past and concluded that we'd be chasing our tail trying to match figures from elsewhere! See this post for more background on the issue.

John

Hello

I agree with Antonio. The elevation data is highly over estimated. I'm not trying to compare with Strava or my Garmin GPS, but with official maps.

I rode several ascent where you have only uphills (no flat part or downhill part), and the altitude of the start and end points are clearly marked on official maps -> elevation is easy to compute. Every time the ploaroute elevation was too high.  (some of the climbs were climbed by Tour de France, and measured very precisely)

Plotaroute remains a great tool I use all the time :-)

Greetings from France