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[mkgmap-dev] HGT - getElevation()

From Gerd Petermann gpetermann_muenchen at hotmail.com on Mon Jan 15 14:31:53 GMT 2018

Hi Andrzej,

attached patch moves hgt area. With this patch I see two effects:
1) DEM tiles have the same size (values in header), but different data. The aligned tiles are always much bigger, so
I think I underestimated the nnegative effect of interpolation.
2) In Mapsource data DEM data is a bit clearer, but it is shifted relative to the other data. This also happens with your patch,
no difference visible.

See http://files.mkgmap.org.uk/download/394/extend.png and http://files.mkgmap.org.uk/download/393/orig.png
If you open both screenshots and switch between them the move is visible.
My conclusion:
1) aligning the tile to hgt raster would be better if quality matters
2) if we do that, we must align all data, not only DEM, and I think that means that we should do it in splitter.


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen at hotmail.com>
Gesendet: Montag, 15. Januar 2018 14:57:17
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev] HGT - getElevation()

Hi Andrzej,

ooops , just noticed that I did not update my patch. See new version attached.
I am now playing with a version that moves all corners into the same direction.
BTW: I've used --dem-poly=bolivia.poly with file from geofabrik.


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej at poczta.onet.pl>
Gesendet: Montag, 15. Januar 2018 12:51:00
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] HGT - getElevation()

Hi Gerd,

I guess your code already makes sure, that whole area is covered by DEM.
So yes, extending bottom/right is not necessary.

Best regards,
mkgmap-dev mailing list
mkgmap-dev at lists.mkgmap.org.uk
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