I'd really like dealer installed NAV in my new car. Why are they cd driven & not satellite?

I heard if you get navigation "in dash" that it can only be updated by buying cd's to load. The dash mounted types, Garmin, TomTom, receive satellite signals and are constantly updated. I really hate anything on my dash or stuck on the winshield. Why aren't "in dash" kinds satellite driven too? I don't understand why the same antenna that runs your satellite radio couldn't run your nav too? Or maybe you can order one to be installed that is?


If not, how do you know how often to update, and are the cd's expensive?|||I think I see what you are asking, the satellites transmit a signal which your GPS interprets into a position and superimposes the position onto a built in database of maps, both systems whether built in or windshield mounted need to have their map database updated periodically, the new tom toms you can just hook them to your computer and update from their website. The built in models you need to buy CD's. Your position is updated continuously, the maps you need to update yourself. Sat radio and GPS receive different signals so different antennas, on cars with factory antennas you don't even see them.|||Nissan "Zen Ren" DVDs are $145 each and get updated every 3 or four years. Nissan system uses global positioning too. It is just the software files are so massive all the roads of the western hemisphere ponits of interest, malls ect... Most of the in cars sytems have some advantages the TOM TOM and Garmin do not. Like not breaking a side window reaching in and steal it...There gos $500 not covered by your insurance unless you pay extra.|||The disc only contains the map that you see on the screen. The country side is constantly changing with new roads, neighborhoods, and infrastructure. The map must be updated in order for the system to be accurate. Whether it be by download or disc, all nav systems require that the maps be updated.





They all use the GPS system, it's how your nav knows where you are on earth and then displays the little arrow as it moves along the map.





As far as antennas go, a regular old car radio antenna doesn't have enough surface area to receive a sattelite signal.