[mkgmap-dev] DEM: performance with bicubic interpolation

Wed Jan 24 16:03:52 GMT 2018

Hi Gerd

Perhaps I'm too fussy  differating between values per se  and string values

Anyway,  the --dem-interpolation seems a very good idea with a chance to 
add  more types of interpolation  when available.

Nick

On 24/01/2018 15:57, Gerd Petermann wrote:
> Hi Nick,
>
> is that so?
> I'll change it to
> --dem-interpolation=auto|bicubic|bilinear
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von osm at pinns <osm at pinns.co.uk>
> Gesendet: Mittwoch, 24. Januar 2018 16:52
> An: mkgmap-dev at lists.mkgmap.org.uk
> Betreff: Re: [mkgmap-dev] DEM: performance with bicubic interpolation
>
> Hi Gerd
>
> I'm a bit confused when you mentioned value as that seems to imply a number?
>
> Just to clarify :
>
> the options are:
>
> --dem-interpolation=auto or bilateral or bicubic ?
>
> Nick
>
>
>
> On 24/01/2018 15:10, Gerd Petermann wrote:
>
> Hi all,
>
> I like Andrzejs suggestion and created a patch that implements and documents the option like this:
>
> --dem-interpolation=value
>          Use this option to speciy the method that is used to interpolate
>          data from hgt raster to the DEM raster. The value bicubic gives the
>          highest precision but is slower, bilinear is faster but less precise,
>          it tends to smooth the profile and thus also reduces DEM size compared to
>          bicubic. The value auto means that bicubic is used where is seems
>          appropriate according to hgt resolution and dem-dist value, else bilinear
>          is used. If not given, the default is auto.
>
> Please suggest improvements, else I'll commit that tomorrow.
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk><mailto:mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej at poczta.onet.pl><mailto:popej at poczta.onet.pl>
> Gesendet: Mittwoch, 24. Januar 2018 14:57
> An: mkgmap-dev at lists.mkgmap.org.uk<mailto:mkgmap-dev at lists.mkgmap.org.uk>
> Betreff: Re: [mkgmap-dev] DEM: performance with bicubic interpolation
>
> Hi Gerd,
>
> maybe someone will add more input to this discussion, but for me now
> following solution make sens: provide option dem-interplation with 3 values:
> - bilinear - fast interpolation for all layers,
> - bicubic - precise interpolation for all layers,
> - auto - default settings - automatically switching between bilinear and
> bicubic, depending on DEM and HGT resolution.
>
> --
> Best regards
> Andrzej
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>
>
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