Ascent calculation is inaccurateFORUMS HOME SEARCH FORUMS

Hi all,

First, I am really blown away by the fast, easy and intuitive way to create a route! Really great tool!

But also I voted for adding the more realistic ascent calculating approach. Maybe let the user choose the interval as an advanced option?

Thanks.

Eric

Hi Eric - Thanks for your kind feedback about the site.

Hopefully we can make some changes to the ascent calculations soon - I notice it is moving up the Feature Request list!  And also, there is a request to add a Total Descent calculation, which is something that could be done at the same time.  There is already an option for users to choose different elevation intervals though in the Route Profile tool. There would need to be a standard interval by defaut to make the figures comparable between different routes on the site.

John

Thanks, John, for pointing to that option. Sorry for not looking into all of the features in the first place.

Hi,

I have been experimenting with various Garmin and Satmap GPS units and .GPX files with my two Ramblers groups, many members of which have and use these. These units have always recorded very different results in their Trip Computers by the end of a walk.

Personally I have an old and trusted Garmin Etrex 10, which records distance but ascent can only be interrogated via the .GPX file. I use Plotaroute to plan my routes for both A parties. I'd welcome advice from anyone who reckons that I'd get superior accuracy from buying a newer GPS, and which one to buy!

If I download my plots to various mapping apps they all read remarkably similarly for distance, usually within 3%. Ascents vary widely. If I save my Etrex 10 trip computer distance it always reduces when the .GPX file is saved and smoothed. I guess smoothing has a similar effect on ascents.

Here's an example:

From my personal experience of a short trial OS Maps ascents recorded on my Etrex record are far higher than even Garmin Basecamp! So ..........

I've decided after all my research to use Plotaroute for my route plots, distances, timings and ascents and find it as accurate as any other app, easier and quicker to use and more accurate than most, it shows routes on the ground that don't often exist on OS maps, and is reliably within a safe margin of error especially where I need to plot a route within a limited time window, for example when my group has a coach ramble and we need to get back to the coach by a certain time as demanded by the driver's working hours.

Dave

Thanks for sharing this feedback Dave and for putting your faith in plotaroute. It’s hard for any one application to claim they have the most accurate ascent figures, as it really depends on your definition of ascent, but I think the most useful thing you can do is to always use the same system when comparing ascent figures for different routes and I'm very pleased you've chosen plotaroute for this. 

John

Hello

Any update on this ? I ride a lot in the Alps, always using plota route as it is really a great tool.

My impression is that the difference between what plotaroute indicates and reality (measured on a map, or with several GPS or altimeters) has decreased, but remains at least 30% too high.

I know using a GPS to compare is not very accurate (a GPS can also be wrong), but I did comparisons with "famous" climbs (for example some Tour de France stages which are well documented)  which are 100% climbs (no up and downs), with known altitudes (where several web sites or maps agree on the altitude) and every time plot a route overestimates.

But still a great tool despite this!

Pierre

Hi Pierre,

I'm afraid we don't plan to make any further changes to our elevation stats. Every system calculates these differently and there really is no definitive "correct" figure, so we'll be constantly chasing our tail if we try to match calculations from other sources. The best advice we can give is to only compare ascent calculations from plotaroute.com with those of other routes mapped on plotaroute.com, rather than with figures obtained elsewhere.

John

Hi! As someone whose background is in geomatics I confirm what John says.

The "accumulated climb / descent" figures that we use are a useful fiction that can only serve as an approximation. Technically, we are faced with the problem of trying to measure non-rectifiable paths (i.e., curves not having a finite length). The problem was fascinatingly well explained in a fairly accessible manner by Benoît Mandelbrot in his 1967 paper "How Long Is The Coast of Britain?".

I agree with the geometry, topology, mathematical side of it, John is correct in depending on how you define ascent, specially sampling distances, thresholds, you will have very different numbers.

OTOH, in practical terms, many of us are used to numbers given by devices with altimeters that have an intrinsic slow average to it, but somehow RWGPS, Strava and Garmin seem to agree on their "fake numbers" (to paraphrase trump) by 10% or better.

I prefer to generate a route and have a estimate of climb that is just as fake, so while I am riding I can know "done 2/3 of climb already, great".

One simple solution is to have options on the program to have ascent (and descent) with options for "Garmin estimate", "Fitbit estimate", "ant walk", whatever. This way it can be as useful as other existing programs that are "perceived to be correct" (because they match the ride computer), and still give the higher, "more accurate" estimates for the purists.

At least distances seem to be nearly identical for every app out there.

Hi Jose, that's an interesting anlaysis of the psychology - I like your Trump analogy! Personally I've found that different sources often vary by more than 10%, however, regardless of that, it wouldn't be possible to replicate figures from other sources without knowing the exact formulae they use, so having a "Garmin" estimate or a "Fitbit" estimate isn't feasible I'm afraid.  Also, I think it would complicate things and cause consfusion. I'm afraid we've nailed our colours to the mast on this one - we'll be constantly chasing our tail if we try to replicate estimates from other sources, so we've decided to leave things as they are and focus on the many other Feature Requests that we've received. As per our post below, the best advice we can give is to stick with one source for estimates of ascent. 

John

Hi all, In my little experience with plotaroute I've noticed e 40% error in ascent calculation.It is interesting that plotaroute is the only one (among the different apps I use) that over estimates the ascent.

I can tell you that all other apps have the same calculation , at least within few meters, tha precesily overlap tha reading of my gps device. To give some numbers, planned route was more tha 520m ascent with plotaroute, while on the same track otehr apps expected 385m that was  exactly what I recorded.

Moreover, if I look to the elevation only, it is accurate as all other maps.

It is disappoint that such a good planner gives an incorrect prediction, that can't be helpfull if you are concerned about the effort reqiuired to perform that trip (ascent).

Thanks! Any suggestion is welcome.

Please see our FAQ on this: Why does the Total Ascent figure for my route differ from figures calculated by my GPS device or other applications?