Hmmmmm.... interesting ...the plot thickens!! I still maintain its the sat nav aerial and as such needs to be 'visible' to the satellites, hence its location on dash. Yes its ugly, with the wire dangling and routed under trim, but like modern day Tom Toms and Navmans we locate them on windscreen for best signal. To retro fit such a system , although not impossible, would require sourcing of the cd rom in boot, the Philips lcd screen next to radio, the aerial and the loudspeaker in passenger footwell, and all the associated wiring.Would this wiring be in car already? According to my manual (TS 1492-A-97) the cars location is constantly calculated by GPS and a gyro sensor (acceleration probe) and the speedo signal.Would these be in place ready for retro fitting? Would someone go to all this hassle when mobile sat navs have been around for many years? Not sure, so i think its how it left the factory....And the small black dome in center of windscreen on dash is indeed the sunshine sensor for climate control.