Saul, I really don't know why you think I doubt GPS. I've been using it for years and think it's truly excellent.
The latest Garmin systems are superb; my question was whether they are capable of processing GNSS signals other than the GPS constellation in order to provide additional redundancy. This will be of particular importance with the emergence of the Galileo GNSS.
I'm fully aware that the GNS430 can use terrestrial signals, the question related to alternative space-based systems.
RTFQ!