Why does GPS work when underground and under big buildings but radio signals, Wi-Fi, and cell phone signals struggle?

Question

Why does GPS work when underground and under big buildings but radio signals, Wi-Fi, and cell phone signals struggle?

In: 4773

Answer 1

Most things equipped with GPS also come equipped with a ‘dead reckoning’ system of some kind.

It uses your last known location and accelerometers and compass and such to make a best guess at where you are when you are out of contact.