I believe it will see any "visible" router, and so long as that router is in the skyhook database. It can use the signal strength and GPS coordinated of that router (along with others) to guess approximately where you are. Routers may be not visible, and not in the database. What you need an open access point for is so google maps can connect and compare data it has with Skyhook's database.So let me get this straight. I can determine my location via wi-fi as long as there are wi-fi routers present. I do not have connect to the router it just somehow transfers the location data to me even though the network is locked. And the maps can only be downloaded if I am near an unlocked router. Is this correct?