Hi Andrzej, yes, your original patch dem-align-6.patch implements bicubic-catmull and the faster replacement by Paul Breeuwsma does that as well. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej@poczta.onet.pl> Gesendet: Mittwoch, 24. Januar 2018 13:45 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: Re: [mkgmap-dev] DEM: performance with bicubic interpolation Hi, I have added more algorithms for testing, patch is attached. Patched mkgmap recognize following values for x-dem-interpolation: bilinear bicubic bicubic-spline bicubic-catmull bicubic-hermite I have prepared new set for testing: http://files.mkgmap.org.uk/download/408/interpolation2.7z For me bicubic-catmull looks like bicubic. Bicubic-spline looks inferior and bicubic-hermite gives weird results, maybe something is wrong. Still bicubic interpolation looks the best. -- Best regards, Andrzej