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

GPS doesn’t work underground. What IS working is “Location Services”. Most devices with Location Services use GPS but also an array of different technologies to self-locate.

For example, my cell phone uses any and all of the following:

* Global Positioning Satellite
* Wifi Location (if Wifi is turned on on a Google phone, it looks at what SSIDs it can see and their relative signal strengths and other location data and uploads to Google. Other devices can then use this same list of SSIDs to ask Google where it is and get a pretty accurate result.)
* Cell Network (the phone can see multiple cell towers and their relative signal strengths and self-locate the same way as WiFi)
* Accelerometer-based dead reckoning (If you know where you were and then traveled at known speeds and directions, you can work out where you are pretty accurately, though the accuracy falls off the longer the time between confirmed location)