[mkgmap-dev] Performance with zipped hgt files

Mon Jan 8 11:01:02 GMT 2018

Hi Andrzej,

thanks for the input.
The current implemention with zip files fills a buffer for each hgt file when it is needed (when the first elevation data is needed).
The buffer is freed if the DEM calculation for the tile is done or when mkgmap is sure that the buffer is no longer needed for the current tile.

I did not try it but mkgmap should support 76x76 tiles, but I see no need to use that with mkgmap, at least not with unzipped hgt files.

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej at poczta.onet.pl>
Gesendet: Montag, 8. Januar 2018 11:50:13
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] Performance with zipped hgt files

Hi Gerd,

 > 2) reduce run time be storing more data in buffers

This is what I would chose. I think java x64 can use swap to increase
heap size. And RAM memory is a relatively cheap upgrade.

 > I think NTFS compressed folder is a good compromise

I did it long time ago. Whole set of SRTM3 is about 38.3GB and takes
23.1G on HDD. It is even better for Viewfinder Panoramas files, where
44.3GB od HGT takes 13.8GB of drive space.

Another question, does mkgmap support non-standard HGT size? With
BuildDemFile I use HGT with raster 76x76 for overview maps. It is faster.

--
Best regards,
Andrzej

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