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[mkgmap-dev] Usage of DEM files within zip

From Gerd Petermann gpetermann_muenchen at hotmail.com on Mon Jun 8 06:56:54 BST 2020

Hi Joris,

I cannot reproduce the problem. I've created a srtm3.zip containing two files N52W003.hgt and N53W003.hgt and --dem=c:\temp\srtm3.zip works fine.
My assumption: Your world-hgt.zip file really contained all hgt files and got larger than maybe 2G and the zipfile class in java cannot process it.

mkgmap tries to support the file formats which are provided by the various DEM providers. I think I once tested performance with a large zip containing many hgt files and it was worse compared to single zipped files.
IIRC the better alternative was to compress the folder with the hgt files (not using zip but the OS methods) or to have each hgt file zipped.


Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Joris Bo <jorisbo at hotmail.com>
Gesendet: Sonntag, 7. Juni 2020 20:45
An: Development list for mkgmap
Betreff: [mkgmap-dev] Usage of DEM files within zip


I struggled today with the DEM/hgt files in a zip. After downloading some extra and checking/rezipping finally my maps did not work anymore.
I do not have the exact error anymore but it was clear: DEM HGT files not found

Now it looks like if the ZIP does not have a folder but only the HGT files on the root of the zip then mkgmap does not recognize them
If I rezip everything again and put the files within a subfolder first, it is oke.
For me its fine, I solved ‘my’ issue, but if this is true it could better be in the manual or solved in code.

Looks like this does not work:

And if I do it like this its oke

Kind regards,
Joris Bo

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