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[mkgmap-dev] HGT - getElevation()

From Gerd Petermann gpetermann_muenchen at hotmail.com on Tue Jan 9 20:19:58 GMT 2018

Hi Andrzej,

the patch is based on r4040. Do you see those artifacts with r4041?


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej at poczta.onet.pl>
Gesendet: Dienstag, 9. Januar 2018 21:04:20
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] HGT - getElevation()


Gerd, your additional interpolation would be redundant.
Side note: comparison of double and integer doesn't look safe. Maybe
would be better if interpolateHeight() returned integer?

Frank, I understand your idea, but please note, that your choice of
triangle is arbitrary. There are 2 ways of dividing a square and if you
would choose the other way, results would be different and not only for
the middle point. This suggest that the solution isn't complete. Classic
bilinear interpolation seems better, but differences are small and
actual map looks more or less the same.

I have attached second patch, which apply interpolation when only 2
values on any edge are present.

Another topic. I observe some DEM artifacts, when displaying area near
the border of dem-poly. There are small rectangles without shading
within a bigger tile. They appear at random, when scrolling or zooming
map in BaseCamp or Mapsource. Ctrl-G doesn't help. See attached img.

I haven't noticed the problem, when compiling a map without dem-poly.
Maybe it is a result of slanted edge of DEM clipped by poly.

Best regards,

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