Hi Henning, yes, we have to scale hgt resolution to garmin resolution, this is not about voids.
We may use the same algo to fill voids. I think this link is quite interesting: https://web.archive.org/web/20051024202307/http://www.geovista.psu.edu/sites/geocomp99/Gc99/082/gc_082.htm Gerd ________________________________________ Von: mkgmap-dev <[email protected]> im Auftrag von Henning Scholland <[email protected]> Gesendet: Dienstag, 23. Januar 2018 14:09:17 An: [email protected] Betreff: Re: [mkgmap-dev] DEM: performance with bicubic interpolation 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_SRTM_datasets 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=.. _______________________________________________ mkgmap-dev mailing list [email protected]<mailto:[email protected]> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev _______________________________________________ mkgmap-dev mailing list [email protected] http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
