For srtm I found elevation accuracy of 6m in wikipedia, so my 10m was not that unrealistic. Btw. We are talking about interpolating from hgt-data position to Garmin-data position, aren't we? For filling voids, it would be a good idea to use some spline interpolation as written here: https://en.wikipedia.org/wiki/Shuttle_Radar_Topography_Mission#Void-filled_S... Henning * * On 23.01.2018 20:59, Henning Scholland wrote:
Hi Andrzej,
I also suggest to make interpolation optional.
So far I don't understand your argument. I agree, compilation time is not the only criteria. The question is, what is the benefit for the user. For example: If accuracy of srtm is +- 10m and the difference between with/without interpolation is +-1m, then it's definitely not worth spending any effort on interpolation. Only in cases, where interpolation accuracy is on same level than srtm accuracy, it starting to be worth spending time for it.
Do you have any values for differences with/without interpolation with same input data?
Henning
On 23.01.2018 20:22, Andrzej Popowski wrote:
Hi Gerd,
there are different kind of bicubic interpolations. I'm not good at this math, I think the previous version was actually bicubic spline interpolation. See other possibilities here: http://mrl.nyu.edu/~perlin/cubic/Cubic_java.html
I don't know, which type of spline or cubic interpolation is best for DEM. Maybe differences aren't big, but I think it is better to have good interpolation than fast one. You compile a map once but then many people can use it.
It shouldn't be difficult to include an option like: --dem-interp=..
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