Why the stage 2 gpx track shows a rollercoaster

For those who’ve done the Manaslu Trail Race already, who raised their eyebrows at the elevation profile for the trail race’s second stage, from Dhoban to Deng, here is an explanation.

Firstly, see the profile below. It looks like the course involves mountaineering! There is a sudden height change of 670m / 2200ft in less than a mile. Impossible!

We’ve always put this down to the GPS readings being affected by the hugely steep cliffs surrounding the river and the trail at that point.

Normally a GPS device with a barometric altitude meter would take the correct readings, however until now we’ve never seen a track that does not make an elevation profile similar to what is seen.

We’ve tried to add data from elevation datasets, like Google DEM, where satellites sense the elevation of the surface of the earth in 1m2 tiles. That should be good for any GPS track to give a realistic elevation profile (as digital GPS trackers are notoriously bad at measuring the elevation correctly).

However, it took until today to look more closely at the Google DEM – which is effectively the same as the contour lines on Google Maps. See the image below. You can see that the river is running over a rolloercoaster, descending into two deep troughs, going down to 1600m, from much higher.

And a bit closer:

Conclusion:

Until we measure the route with a decent barometric altimeter, we’re going to have a rollercoaster elevation profile!

One Comment “Why the stage 2 gpx track shows a rollercoaster”

  • Jeff

    says:

    hi Richard
    I will be a volunteer for Everest 135mile run in Lukla May 2024.
    Found your videos so amzing and impressed while collecting info of running video in Nepal.
    Just wondering if you or any your freinds would be in KTM/Jiri/Lukla then?
    Like to have you and our 135Mile runner catch up if possible.

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