[mkgmap-dev] HGT - getElevation()

Mon Jan 15 21:05:13 GMT 2018

Hi Andrzej,

hgt files are 3'' from viewfinder, the pictures show an area in Bolivia.
The picture shows the location in the status line.
And yes, the extended DEM data is clearly shifted relative to the OSM data.
I assume now that Garmin uses this feature to match existing map data with existing
DEM data.
Do you want to say that you don't see a movement in your tests?

Gerd

________________________________________
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 21:41:48
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] HGT - getElevation()

Hi Gerd,

on your pictures it looks like shading form extended DEM doesn't match
map features. Is it HGT with resolution 1200? Shading looks more
detailed than on my map, which uses DEM created by BuidDemFile. I have
to recompile my map to compare.

I have done different test. I have analyzed a round peak on a map and
traced coordinates of the center of highest DEM value. All at zoom 20m.
Than I looked up the coordinates on HGT tile in QGIS. There were good
match, coordinates were max 5m from the center of a HGT pixel. Then I
checked offset of DEM, it was about 7m north and 18m west.

For me it looks like shifting DEM works correctly, but I can't explain
effects on your map.

--
Best regards,
Andrzej
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