If you tune in a NAV frequency into your G1000 the ID of the Nav Aid will be shown next to the frequency after some time. In this example SEA
:
Source: http://krepelka.com
How does this work? Because we know that there is the possibility that two VORs could have the same frequency, so the frequency is not uniquely bound to an identifier.
I have two assumptions:
The Garmin is listening to the morse code, transfers it into the letters and shows it in the display.
The Garmin is checking the Nav database and searches for the frequency and takes the identifier of the closest, based on the GPS position.
Which one is right, or is there even another way Garmin does it?