Map downloaded successfully.
Could someone please explain what this map does? Thanks to Google, I know that this is a Digital Elevation Map, whatever that means.

Just for the sake of curiosity:
- Will my Nuvi 760 be able to use its gmapsupp.img maps without the base map?
- And why would a base map need an update in the first place, e.g. from 3.00 to 4.00 or to 5.00? Did digital elevations change or something?