How does Nuvi read maps


Was wondering how my nuvi 255W reads different maps.

I have a 3rd party map i added to my garmin from

It is an updated map of my area.

It has newer roads than what does city navigator 2009. When I view the roads in Mapsource the new road is there however when viewed on the Nuvi the city navigator 2009 must take precedence and I can not see the map, unless I turn city nav 2009 off.

How do Nuvi's see different map sets? I would have thought the Nuvi would go down the list of maps and overlay roads from the different map sets.

can anyone explain how this works?


Nuvi 255W


The maps are shown in order of hierarchy. City Navigator always has priority over everything else. Unless the maps are designed (ie programmed) to be transparent, then they won't show on top of each other.