the annoying part is that software of different firms isn't compatible most of the time. Satmap, Garmin, Anquet and others each want their share of the market. (The only one getting rich is the OS
If you have a Satmap device and have an online account you can plot your routes on their website and transfer them to your gps. For detailed mapping you need the appropriate memorycard.
Others can enlighten you on open source mapping and software. I'm not familiar with that ballgame.