Due to simplicity I’ve always used pre-compiled OSM maps for my Garmin. Since they are only available for certain pre-defined areas there is a slight lack of comfort, since I did need to change the whole gmapsupp.img every time I’ve moved out of the loaded area. Today I tried mkgmap to comile my own set of tiles into a gmapsupp.img and it did work great. I took a map of germany and added some areas I did also want to visit. At first I couldn’t believe how fast mkgmap had processed the tiles, but the output was a valid gmapsupp.img and after transfering to the Garmin it did work flaslessly.
How to create your own gmapsupp.img:
Grab the tiles you want. I used a routable map of germany as the base.
Extract the downloaded files: gunzip *.img.gz
And combine them using mkgmap: java -jar mkgmap.jar –gmapsupp *.img
This will result in a gmapsupp.img file that you can transfer to your Garmin.