Why does GPS work when underground and under big buildings but radio signals, Wi-Fi, and cell phone signals struggle?
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I remember being in a Saab about a decade ago. That thing had a built in GPS where the map used the distance travelled and turning radius of the car to find out where it was in the tunnel. My phone lost signal but the car did just fine.
GPS doesn’t work well underground. GPS is ultra-high frequency. Ironically your phone will look for WiFi and Cell signals and has a database of expected GPS coordinates based on the signals that is sees. These aren’t super precise but since these WiFi signals have an expected GPS location your phone can guess a triangulation of your location.
Most electronics are ultra high frequency and don’t go through things very well. Low frequencies like AM radio and ultra-low frequencies are such that they can more easily go through the ground.
Tell me you haven’t tried to use GPS inside a tunnel without telling me you haven’t tried to use GPS inside a tunnel.
A lot like saying all internet is “wifi”, this is conflating GPS with broader location finding technologies.
GPS is one specific method used to find a device’s location, and it does not work underground, or even when standing next to tall buildings/mountains, etc.
As other commenters have pointed out, GPS is not our only location finding technology. Oftentimes, these technologies work together to cover up each others’ faults.
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)
GPS does not work underground, it can even have trouble in certain terrain where you don’t have reception to enough satellites.
GPS does not work underground and does not work under big buildings. It even struggles between buildings.
It doesn’t. My GPS struggles and fails when I enter a tunnel. It recovers when I exit the tunnel.
It does? I guess my experiences exiting the Holland Tunnel have all been flukes…terrifying, confused, flukes
They don’t. However there is a magnetic field mapping sensor that can accurately navigate underground and in buildings.
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