I am using 11.2.2 iOs on my iPad Air 2, iPad Pro 9.7, and iPhone 6+, sitting in my office on the first floor of my home with wifi, BT, and antenna turned off. I still get good GPS reception, 10 M or better, and the three devices agree within +/- 1 foot with the GPS altitude. The iPad Pro is equipped for cellular, but there is no cellular service. The others are equipped for cellular service,...