> GPS signals are much higher frequency and very low power and thus don’t work indoors. With a $20 antenna placed near the window, together with a modern recei

> GPS signals are much higher frequency and very low power and thus don’t work indoors. With a $20 antenna placed near the window, together with a modern receiver, it is easy to get nanosecond level of precision for GPS systems. Some receivers even have in-door precision specification. GPS not only work indoors, in terms of timing, it works actually pretty well indoors.