Hi Guido,

I do not understand why the elevation filter "Interpolate Elevation Data" with 
setting "coars" does not fit your need. The used spline interpolation is much 
more natural than a linear interpolation.  

But either linear or spline interpolation will not provide good results if 
your input data is faulty. Especially along steep walls a few meters deviation 
in the horizontal plain can result in a significant difference of the 
elevation. In that case you have to reduce points to a minimum. And fine tune 
the position to a better fit. 

Oliver

Am Montag, 24. Juli 2017, 19:52:27 CEST schrieb Guido Scholz:
> Dear developers,
> I like to request a new feature to improve elevation profile editing for
> planned routes. As mentioned in my earlier request today DEM elevation
> data shows a wobbling effect if available only in low resolution for
> mountainous areas. In certain regions of the earth, like southamerica,
> currently it is a pretty standard to have for example only 90 m
> resolution. But also 40 m resolution can lead to this wobbling effect in
> mountainous regions like the Andes.
> 
> For planning routes this is not just a cosmetic issue but results in
> significant error for summing up the elevation gain for one trip. As I
> found planning my last years trip to Peru the error can easily sum up to
> 50 % or even much more. This is caused by the continuous up an down while
> in reality the road may have a countinuous inclination. Ofcourse the
> situation did not improve for my this years planning ;-).
> 
> To ease planning I like to have a new feature in the "filter" section
> under the topic "Change elevation of track points". There currently are
> some options available but these are unsufficient regarding the
> described usecase.
> 
> My proposal is to add a new linear interpolation option to take the
> start and the end of a marked range and do a straight away linear
> interpolation between these two points. So for planning a user could
> for example start the marked range at a point in the valley and end at a
> pass. The resulting error will be significantly lower than the DEM-only
> solution (even if smoothing is applied).
> 
> Guido



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