[mkgmap-dev] Usage of DEM files within zip

Mon Jun 8 10:41:33 BST 2020

Hi Joris,

it probably depends on the tool that is used to create / update the zip file. Many programs cannot handle large zip files. I hope mkgmap / java has no such problems, else we may run into problems with precompiled bounds or sea.

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Joris Bo <jorisbo at hotmail.com>
Gesendet: Montag, 8. Juni 2020 11:21
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev] Usage of DEM files within zip

Thanks, i'll do some more testing.

It was indeed a single zip with 17Gb hgt.
Strange thing is that it for sure works with a 17Gigabyte single zip containing 26.000 mixed 1arc/3arc hgt files. (Windows 10)
It still finds all files from New Sealand, to Zambia and Europe as long as it contains a subfolder in the zip.
But don't bother, I did not take performance into account. And my tests where not that scientifically correct. Because of the huge sizes... I only tried only until it worked again.

Kind regards
Joris

-----Oorspronkelijk bericht-----
Van: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> Namens Gerd Petermann
Verzonden: maandag 8 juni 2020 07:57
Aan: Development list for mkgmap <mkgmap-dev at lists.mkgmap.org.uk>
Onderwerp: Re: [mkgmap-dev] Usage of DEM files within zip

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.

Gerd

________________________________________
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

Hi

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:
world-hgt.zip\N00E006.hgt
world-hgt.zip\N00E007.hgt
world-hgt.zip\N00E008.hgt

And if I do it like this its oke
world-hgt.zip\world-hgt\N00E006.hgt
world-hgt.zip\world-hgt\N00E007.hgt
world-hgt.zip\world-hgt\N00E008.hgt

Kind regards,
Joris Bo

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