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[mkgmap-dev] option --show-profiles and DEM

From Gerd Petermann gpetermann_muenchen at hotmail.com on Thu Jan 11 09:58:40 GMT 2018

Hi Minko,

yes, that's another reason why I think that the additional "precision" of DEM data in feet doesn't improve anything.
Leave alone bridges and tunnels ;-)
Also the map data is rounded to the 24 bit raster  (~2.3 m) , only DEM uses a 32 bit raster for the points, so whatever
Mapsource or Basecamp are doing with the information, it is probably also based on interpolation.
In my eyes hill shading makes a map nicer and helps to decide where the hills are, not much more.

Off Topic:
My experience with height profiles of planned bicycle routes:
When you see a spike in the height profile it may mean that the road goes through a tunnel or that you are routed over
a steep highway=path acress the hill because it is much shorter than the way around it. Always a good reason to examine
the planned route at that point ;-)


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von lig fietser <ligfietser at hotmail.com>
Gesendet: Donnerstag, 11. Januar 2018 10:38:24
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev] option --show-profiles and DEM

With this test map I can also see the difference in the altitude profiles with and without DEM (based on 10m contour interval):

Please note that the higher accuracy of the DEM profile does not always reflect the elevation in reality, the road beds are always smoothing out the micro relief and thus leading to a lower elevation gain/loss when riding/walking this track.
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