[IvyMike]

> if you get cell service through the ceiling, you'll get GPS signal through it.

Download one of the apps that shows individual GPS satellite signal strengths and tell me if you still believe this. Definitely not true for my phone.

[ghaff]

It really depends. I have an older dedicated GPS receiver that absolutely no way will receive a signal indoors. My iPhones all do a pretty good job. (FYI, you can only get signal strength on an Android phone; Apple's CoreLocation API doesn't provide that or some of the other detailed satellite data.)