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Ascent calculation is inaccurateFORUMS HOME SEARCH FORUMS

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    plotaroute admin   Friday 15 Dec 2017 08:45:44

    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. 


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    Dave Fellwalker Thursday 14 Dec 2017 12:12:03


    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:

    Track_13-DEC-17 015026 PM.gpx   kms Metres Scale
    Plotaroute Open Source mapping 18.294 419 Unknown
    WalkLakes 18.3 549 1:25,000 mapping
    Ride with GPS 18.3 441 OpenSource
    Where's the path 18.2 549 1:50,000 mapping
    Dave's Trip computer 18.41   1:25,000 mapping
    Garmin Basecamp 18.3 658 OpenSource
    Contours counted visually on WalkLakes   400 1:25,000 map

    rom 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.


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    eric borghs Friday 17 Jun 2016 07:03:24

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

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    plotaroute admin   Wednesday 15 Jun 2016 14:43:53

    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.


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    eric borghs Tuesday 14 Jun 2016 12:37:21

    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?



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    Pierre Chartier Monday 23 May 2016 18:10:06

    Thanks. I voted or it.

    There is just near my place an ascent which is pure uphill on 18km. It's about 1400m ascent. Next time I climb it I will see what plot a route gives and compare it both with a map and with what my GPS gives.

    I will let you know.

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    plotaroute admin   Monday 23 May 2016 11:12:28

    Thanks Pierre for your feedback - glad you're enjoying using the site.  Adding some smoothing to our elevation data is on the Feature Requests list but please vote for it to move it up the list (number 52).  Please be aware though that GPS devices are not a reliable bechmark for ascent calculations - we've looked at numerous examples of raw GPS recordings and usually find big gaps in the data (probably due to poor signal reception) that result in ascent figures being understated.


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    Pierre Chartier Saturday 21 May 2016 17:44:45


    I think this would be a nice idea, not to make it comparable with other applications but also to make it more accurate.

    I leave in a mountain area (French Alps), so I ride frequently rides with a lot of elevation. The total elevation on plotaroute is often at least 50% too high. Example : I rode yesterday https://www.plotaroute.com/route/216481

    Total ascent is 2671m on plotaroute. Yesterday a friend and I measured a total ascent of around 1820m (we had two different GPS)

    I found similar results on pure uphill rides when comparing also with the altitudes written on a map.

    The percentages as well are too high. I frequently get on plotaroute a max percentage of more than  35% (38.8% on the ride above) which is impossible to climb on a bike (at least for me!)

    Keep on the excellent work you are doing. Your site is great!


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    plotaroute admin   Wednesday 11 May 2016 12:48:16

    Glad you like the site Claudio - thanks.  

    The Total Ascent figure shown on the elevation profile as you are plotting a route is just an estimate based on a small sample of elevation readings (a maximum of 500 at equidistant intervals across the route)  - a more detailed calculation is made when you save the route using elevation readings at 30m intervals, as it isn't feasible to recalculate this in such detail as you are plotting.  We do adjust the 'as-you-plot' figure by a factor to try to compensate for the smoothing effect of using elevation readings at bigger intervals, but the impact of using bigger intervals differs according to the amount of bumps and dips on the route, so it will sometimes vary quite a bit from the final figure.


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    Claudio Crivelli Wednesday 11 May 2016 09:40:17

    Reagrding ascent calculation I have to say estimation by Plotaroute is quite good during the editing. But once I saved the track, I see even a +40% increment without any reason.

    If I go back to editing the same track and I just move the start-stop point by few meter, the system updates the total ascent and the number comes back to "real" values. So to me the problem seems to be related to the SAVE process... Even without saving, if I switch to the profile tool I see the increased value... It seems the right value is given only during the editing and only in the "HILLS" area (below the map).

    Is this happening only to me?



    ps: plotaroute is a great tool! many compliments!