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[mkgmap-dev] DEM size in Garmin Basemap > 16MB

From Andrzej Popowski popej at poczta.onet.pl on Fri Dec 22 17:50:31 GMT 2017

Hi Gerd,

I have added DEM to my maps using BuilDemFile and without any changes to 
splitter parameters. The biggest DEM was about 35MB and the biggest img 
about 40MB including 32MB of DEM. I haven't noticed any problems. Even 
more, I have build TDB using test version of mkgmap v3999, so mkgmap has 
no problems with reading big img with DEM.

I think there is no superficial limit for single img. Internal structure 
of img is FAT-alike, and limits comes from this structure. You can get 
256 FAT records for a subfile like DEM and 240 sector pointers in each 
record. With max sector size 64kB, it makes limit like nearly 4GB.

I don't know if mkgamp uses fixed sector size for created img. If yes, 
then limit would be dependent on this value.

Best regards,

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