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[mkgmap-dev] DEM: performance with bicubic interpolation

From Andrzej Popowski popej at poczta.onet.pl on Tue Jan 23 15:24:03 GMT 2018

Hi Gerd and Henning,

 > 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.

This is not like interpolations error is placed within source data 
error. This error is added to data error. I believe it can be much 
bigger, especially in case of 3" HGT. This could be tested.

Apart of height error, there is a problem of DEM shape. I mean the exact 
places where is a peak of a mountain or heights points in a profile of a 
route. With simple interpolation, there probably would be much bigger 
positional error.

I have read reports, that increasing DEM resolution above HGT resolution 
increases DEM quality. But this was opinion about bilinear 
interpolation, maybe there is no need for such a settings with better 

Best regards,

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