GPS is awesome. If I become doubtful, I get on a "Government established" point to check it. Even my little hand held one is within 20 feet if I run it long enough.
My cell phone has an option of "constant" GPS or "911 GPS". I assume that that the 911 option allows only emergency personel to use it, if for example, I called and then keeled over and they wanted to see where it was from or the like. I don't know why anyone would want constant except perhaps one could track their teenager that way? Question is whether there are records of GPS for all partisipating cell phones. That would seem to be a lot of records.