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[mkgmap-dev] r4015 in dem-tdb branch implements --x-overview-dem-dist

From Ervin Malicdem schadow1 at gmail.com on Sat Dec 23 09:12:41 GMT 2017

Hi Gerd,

This is regarding hillshade still being rendered even if the area was
excluded in the osm file.
As an example, I specifically removed borneo island in the southwest but
DEM still showed up.


Ervin M.
*Schadow1 Expeditions* - A Filipino must not be a stranger to his own

On Sat, Dec 23, 2017 at 4:08 PM, Gerd Petermann <
gpetermann_muenchen at hotmail.com> wrote:

> Hi Ervin,
> I think there is no longer a need to change splitter since DEM files are
> allowed to grow > 16MB with r4016.
> Just to make that clear: When I write about DEM files I mean the files in
> the Garmin DEM format, they are either contained in a *.img
> or in a *.DEM, and they contain the text "GARMIN DEM". I guess DEM means
> something like "Digital Elevation Model".
> Besides that I don't understand what you mean. Is it about the contour
> lines created by tools like srtm2osm or phyghtmap?
> What could be improved in splitter?
> Gerd
> ________________________________________
> Von: ebmalicdem at cxsmedia.com <ebmalicdem at cxsmedia.com> im Auftrag von
> Ervin Malicdem <schadow1 at gmail.com>
> Gesendet: Samstag, 23. Dezember 2017 06:21:36
> An: Development list for mkgmap; gpetermann_muenchen at hotmail.com
> Betreff: Re: [mkgmap-dev] r4015 in dem-tdb branch implements
> --x-overview-dem-dist
> Getting better each time! Great!
> A suggestion once you will be working with splitter is for the dem to be
> cut using a poly file as well.
> Ervin M.
> Schadow1 Expeditions - A Filipino must not be a stranger to his own
> motherland.
> http://www.s1expeditions.com
> On Sat, Dec 23, 2017 at 12:11 AM, Gerd Petermann <
> GPetermann_muenchen at hotmail.com<mailto:GPetermann_muenchen at hotmail.com>>
> wrote:
> Hi,
> okay, so we now have three new (still undocumented options) to enable
> hillshading and calculation of elevation data in routes.
> Here is a summary of the new options:
> --x-dem=path_to_dir[,path_to_other_dir,...]
> gives one or more directories containing *.hgt files.
> --x-dem-dists=n1,n2,n3,...
> Sample from a Garmin Demo map: --x-dem-dists="5520, 16560, 44176, 88368"
> should contain one number for each level in case you want to use the DEM
> data in a gmapsupp, the values give
> the number of DEM units between two points. A DEM unit is 360° / 2 ^32.
> The higher the numbers the smaller the DEM file. Useful values for level 0
> start
> at 1600 if you have 1'' hgt data and a small area, for large areas
> consider to use 8000 or more. If this option is missing mkgmap will
> calculate one DEM
> level based on the resolution of the hgt files.
> --x-overview-dem-dist=n
> Use this option to add DEM also to the overview map. The value again gives
> the distance between two DEM points.
> It the option is not given or the value is 0 the creation of DEM data for
> the overview map is disabled. This might be needed for large areas and for
> overview img files which
> are already close to 16MB .
> Useful are probably values > 100000, e.g. 256000
> Expect to see "There is not enough room in a single garmin map for all the
> input data. The .osm file should be split into smaller pieces first."
> when experimenting with these options. The additional amount of bytes for
> the DEM files depend on the above options, and the relief of the area.
> Mountains
> require much more space compared to flat areas like the netherlands.
> If you have contour lines in your overview map try without.
> I'll try to add code to splitter so that it creates smaller tiles for
> areas with many mountains. I don't know yet how to store that info.
> Gerd
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