This may be a bit of bizarre question but I'm trying to work out what's on top of my car?! I bought an ex-demonstrator GTI and it has what I would call a 'shark fin' style aerial on the top. I always thought that these were specifically for cars with in-built sat-nav systems, which mine doesn't have. Therefore I was wondering if it's just a neat and tidy radio aerial or if its likely a GPS aerial with all the appropriate wiring, (but just not connected to a sat nav system)? If anyone knows anything about these things and could provide me with a clue, that would be great!