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Explore Map Track vs Tracking Track Elevation Discrepancy

janice.heil

I mapped a track I wanted to bike on the explore map tool on the browser version of Gaia. The stats of this mapped route were:

30.7 mi Distance 5,562 ft Ascent 5,563 ft Descent

I then biked the exact route while recording in Airplane mode and my stats for the ride were: 

31.3 mi Distance 3,669 ft Ascent 3,660 ft Descent

How can these exact same routes be so different in ascent and decent?

I also Strava'ed the ride and the stats for that were: 

31.97mi Distance 4,308 ft Ascent 4,308 ft Descent

I then also used CalTopo and the stats were: 

30.58mi Distance 4,314 ft Ascent 4 314 ft Descent

I'm now tempted to think Caltopo and Stava are correct since they are very similar and one was recording and one was mapping, but that would make both the Gaia calcs off by 1000ft in each direction. I don't know what to believe any more! 

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2 comments

Date Votes
  • Jim

    @janice.heil

    Thanks for writing in about this.

    There are two things that you're experiencing in combination:
    1. It looks like the route creation algorithm inflated the ascent of the route
    2. The track ascent was underestimated, perhaps due to GPS accuracy.

    1. We are aware that some routes, especially routes with lots of small ups and downs, are reporting higher than expected elevation stats. We're looking into this more and we plan to update our algorithm so that it produces more expected elevation stats in situations like this.

    An elevation algorithm can spit out vastly different results based on how often you sample the points. For a mountainous track that has continuously undulating ups and downs, it's possible to get widely different elevations calculated, depending on how frequently you want to sample the points. It will be much higher if you include every tiny up and down. If you under-sample - peaks and valleys may get cut off and the elevation will be too low.

    We think the trick is finding the middle ground between what people expect to see, and what is most accurate.

    I don't have an ETA on when you can expect this update to happen, but we are working on it.


    2. This is also true for recording tracks, but for slightly different reasons. When recording tracks, the app is fed all the raw location data gathered by the GPS chip on your device. From there, the algorithm filters out inaccurate points, and then averages the GPS points in groups, and then adjusts the ascent/descent number as you travel. It is likely that other apps use a similar but different algorithm, so this might be part of the reason for discrepancies.

     


    If you have any further questions, please Contact Support.

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  • Persiman

    Many years later, I'm seeing a similar issue.  I bike many different routes in the same area, and always save Tracks.  I want to design the best scenic Route for others, avoiding the worst hills.  The Route is always way overestimating the elevation changes.  Here's a specific example that I just did to try to see what's going on:

    Track   22.7 miles  1031 ft 

    • Ascent

      1,031 ft

    • Descent

      1,021 ft

    • Max Elevation

      1,795 ft

    • Min Elevation

      1,228 ft

      Then I made a new Route, exactly following that Track.  The Route says 22.6 miles, 2126 elevation

      • Ascent

        2,126 ft

      • Descent

        2,118 ft

      • Max Elevation

        1,829 ft

      • Min Elevation

        1,230 ft

         

        So, the reason this is problematic for me is I can't accurately compare a new Route with a former Track.  Thanks for any comments.

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