[mkgmap-dev] DEM: performance with bicubic interpolation

Tue Jan 23 21:24:44 GMT 2018

Hi Andrzej,

I think you don't see a difference between bicubic and bicubic-spline because your script uses
the same option bicubic for both ;-)

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej at poczta.onet.pl>
Gesendet: Dienstag, 23. Januar 2018 22:17:21
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] DEM: performance with bicubic interpolation

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
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