To update maps for your garmin, we need to understand the file structure.
The maps installed in your device will be in .System folder. This folder are hidden, unhide.. look here
The maps file are with .img extension and usually the files listed as below.
gmapprom.img – factory preloaded map.
gmapprom1.img – another preloaded map (if any)
gmapsupp.img – supplementary maps ( i.e. loaded from mapsource)
gmapprom.unl – unlock code for gmapprom.img
gmapprom1.unl – unlock code for gmapprom1.img
gmapsupp.unl – unlock code for gmapsupp.img
gmap3d.img – 3D Buildings map
gmap3d1.img – Secondary 3D Buildings map
gmapbmap.img – garmin basemap
gmaptz.img – Garmin time zone map
gmapoem.img – OEM mapset
so if you want to add new maps to device memory use one of them.
The junction view file will be in .System/JCV folder.
Map on SD card must be placed inside Map folder.
Interestingly the name can be any name i.e. Gcc2010.img
You can install as many maps as possible as long as it not exceed your SD card size and each map not exceed 4GB.
The junction view file will be in garmin/JCV/ folder.