[mkgmap-dev] DEM: performance with bicubic interpolation

Tue Jan 23 21:17:21 GMT 2018

Hi Gerd,

thanks for option. I have prepared a set for tests:
http://files.mkgmap.org.uk/download/407/interpolation.7z

This set creates maps with different resolutions and interpolations. I 
have created a direct route and compared  height profiles created with 
different maps. Here my observations:
- I can't see any difference between bicubic and bicubic-spline.
- Oversampling with DEM resolution twice the resolution of HGT improve 
look of height profile. It improves shading too.
- I have looked at maximum and minimum height of profile. I noticed 
differences in range 2-6m between bilinear and bicubic interpolation for 
3" HGT.

My suggestion: use bicubic version. If size is not a problem, try some 
oversampling.

-- 
Best regards,
Andrzej