cGPSMapper Website . The command-line I first used to install the maps onto the GPS was: sendmap20 -t/dev/ttyUSB0 640000??.img That works fine, but if you have even a moderately sized micro SD card in the GPS there are much faster ways. As I found more free maps I found much better ways to do it. An alternative approach In the GPS (well, in my one anyway) there is a micro-SD card which is FAT formatted and all of the installed maps are in one humungous combined image of all of the uploaded maps. This means that there is no way to straightforwardly add/remove maps without creating that image, and re-uploading the whole thing. The image file is called 'gmapsupp.img' and is in the 'garmin' subdirectory on the SD card. This means that you can create the file (or even several different files, with different maps on them) and move them directly on there much quicker, either by taking the SD card out and using it in a USB2 reader (for really big files) or switching the GPS to operate in USB Storage mode (which is USB1, but OK for smaller files). You can create the IMG file to copy in as gmapsupp.img with sendmap20 also, with a command-line like: sendmap20 -lNZOpenGPSMaps.img 640000??.img and then, if you mount the GPS as /media/GPS, you can copy that file on directly cp NZOpenGPSMaps.img /media/GPS/garmin/gmapsupp.img QLandKarte Another program I found useful specifically for dealing with the Garmin GPS Map format is QLandKarte , which