@cpf
Region 3 is partly protected in the older non-MSM devices such as your GPSMAP 278 and Garmin claims that the OEM regional basemap can't be replaced. That's not completely true, it simply can't be overwritten like the detail maps in region 49 [gmapprom.img] and region 10 [gmapsupp.img] can be replaced using the usual methods. It's a little more complex to do but it can be done. Read: [Only registered and activated users can see links. ]. Keep in mind that ALL 3 regional basemaps [Americas, Atlantic and Pacific] will still work in other parts of the world. That's because they contain more detailed road data in the specific countries they're meant for, but they still also contain basic data for the rest of the world. If you're wanting to add a modern 'all-world' basemap meant for more modern devices you may find that rgn3 of your device doesn't have sufficient space. To see the size of the region you'll need to dump it using GPSDaemon, that will also give you a copy of the present basemap. Read P4 in full: [Only registered and activated users can see links. ]. Your device may only have ~16MB for basemap storage like the related SP 26x0 and 27x0 series mentioned there. It may be possible to add a non-DEM (Digital Elevation Mode)) world basemap, but the modern DEM ones are too big. Stripping out the DEM may reduce the size sufficiently and your device can't use DEM anyway I think. Best to post in the other threads if you need more info or help as it's more on-topic there for basemaps.