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[mkgmap-dev] DEM file and the block-size option

From Gerd Petermann GPetermann_muenchen at hotmail.com on Tue Dec 26 08:33:49 GMT 2017

Hi all,

the current default block-size is 512. This is used for most *.img files and gives a maximum file size of 65534*512 ~ 32MB.
For large DEM files you might need a --block-size=1024 or even 2048.
If I got that right you may run into the next problem when using this option as
the mdr file will be also created with this value, and if no value is given it uses 16384 (which means the mdr file can grow close to  1GB)

This disadvantage of a larger block-size is that your img files are typically a bit larger.

If I got that right we should be able to calculate the optimal block-size
as we do know the number of bytes that we will write to the img-file before 
anything is actually written to the disk. Wouldn't that be much better?


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