The 660 is the latest Garmin for RVs. I have used Garmin for years and love them, they are very user friendly! Garmins should be updated regularly via the Garmin website to maintain highest accuracy.
Are gps units perfect, no. A gps is only as good as the information entered in to it. If a developer doesn't send accurate information to the county then the information loaded in a gps won't be accurate since they get a lot of their information this way.
When going to my friends new house the gps showed two houses off, not the fault of the gps, problem was the person who sent in the plat map.
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