[closed] Extreme slope variation in different tracks

[walter.z]

Hi,
I made a small tracking while running uphill a road and found in the dynamic profile the max. inclination to be 24.3%. A check with the 'compute slope' tool shows 22% which seems to be reasonable. But then I made another tracking with the road bike and found a slope of only ~10% at the same location which I do not believe. How can that be? The accuracy of the smartphone generally is excellent (Xiamo Mi A1) and was around 3m at this location. See three screenshots for clarification.
Thx, Walter

[Psyberia-Support]

Hi,

"Instant" slopes based on the GPS data is not precise, you should not rely on it.
This data makes more sense when it's smoothed and calculated over longer distances (as given by the "mean slope" value in the statistics).

So why it is so bad? Just because the GPS accuracy is.
Unfortunately you cannot expect reliable horizontal accuracy better than 5 meters with general purpose receivers. And it's much worse for the vertical component.
For example, if you have 2 locations recorded 10 meters apart on a flat surface, you may get a 5 meters elevation variation, leading to a slope of 50%...

In order to get more accurate values, you can try to set the "Noise reduction" setting to high as explained here.

But the best way to have much more precise elevations (and so slopes), is to use a device with pressure sensor. In this case the application will compute and use barometric elevations instead of GPS elevations, which are much more precise.

Another way is to use DEM elevations (I see you have them stored). You can click on the map center icon, on "Tools" and on "Informations" to get the slope value and direction at the screen center.

Hope it helps