As gmt_osx is not gonna be updated to x64 - I wonder if there is an alternative.

Or maybe could this function be added to mkgmap?

I would imagine a call java mkgmap.jar --change-typ gmapsupp.img newtyp.typ

(so remove all existing .typfiles in the gmapsupp.img and replace them with newtyp.typ - for gmapsupp.img consisting of several maps this would be more complicated - I do not feel that is needed).

Plus maybe the option to join several gmapsupp.img files into a new bigger one (only important for very old devices).

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