Generated maps - first experience.


I’m going on a trip to the EU (live in US), so decided to start exploring generating maps for my Garmin Nuvi 3760.
I’ve had a pretty good amount of success with map generation, and I have been enjoying the process quite a bit.

My plan is to generate a map for the US and for Italy. I’ve done some smaller subsets to test this. I’ve successfully loaded both maps individually as gmapsupp.img.
However, I can’t seem to load both maps at the same time. So, that is one issue. I’ve tried <filename.img>, and I’ve tried gmapsup1.img.
It will only load gmapsupp.img.

So, if that is the limitation, then I would like to merge my maps.
I’ve tried to do with mkgmap. However, mkgmap doesn’t seem to merge the maps. At all.

I’ve got “italy.img” at 534M.
I’ve got “usmid.img” at 719M.

So, I run this command:
java -jar mkgmap.jar --gmapsupp italy.img usmid.img (reference:
But the output, is a very small file < 1M.

I know as another work around, I could combine the o5m files.

Thanks for any advice!

You can try OSM combiner: