I'm trying to generate a "World overview map" for my Garmin device. The idea is to have this map on the device all the time, for a very rough idea of the position and then feed in higher resolution maps where necessary, e.g. when going on trip. I would like to use OSM for this purpose with mkgmap.
If I do this straightforward, I would create a ridiculously large img-file, using all the OSM data. I would thus like to just have lower scale information included in the map. However I haven't grasped yet, how to achieve this. Can anybody help me out?