Garmin’s navigation systems use Garmin Real Directions ... The former two have maps of Europe and the latter has maps of the entire world. All three receive updates via Wi-Fi, but TomTom ...
Now what? The secret sauce is tiling. [facklere] used KMZfactory, a free map editor for Garmin maps that goes the extra mile to split the tiles for you, keeping them under the 1MP limit.