ComputerTeddy provides a gmapsupp file for the whole earth in 4 parts (planet_neu_gmapsupp1.img.gz etc. on http://wiki.openstreetmap.org/wiki/User:Computerteddy). How should these parts be combined on a Windows PC into a single gmapsupp.img file for immediate downloading to a Garmin Dakota device?
I concatenated the 4 .gz files to a single .gz file using command line copy and then used winzip to extract the concatenated .gz, but winzip hangs without error message.
Thanks in advance!
Garmin devices use FAT32 file system which limits files size to 4GB. While you could create bigger img on PC with NTFS or EXT2 file system, you won't be able to copy it to GPS.
For your Dakota unpack and copy all 4 files to directory \Garmin on Dakota or SD. You can rename them if you need but preserve extension img.
To answer your question: you can merge img files with GMapTool http://www.gmaptool.eu/
This clarified everything for me!