GPS signal strength is Zero while I'm in a (electric) train.

Why is does my device not get a GPS fix in a train?

up vote 6 down vote accepted

In some trains you sit like inside an Faraday cage, as they even metallized the windows -- thus no signal can get through. That's also why you have special "mobile phone" zones in some trains: Here they placed something like a little "repeater" inside this section of the train, capturing the signal from outside the cabin (and transmitting it back the same way, of course). However, they don't do that for GPS.

  • And, AFAICT, they even couldn't, as that would affect the signal run time. – glglgl May 19 '16 at 8:01
  • Even if they could, that would somehow defeat the purpose: you wouldn't get your position, but the position of their GPS antenna – where you cannot tell how far from your place it is and it which of two directions (towards front or rear of the train). Still, it would be sufficient in many cases, as for the speed of the train direction and distance to the antenna might be quite irrelevant :) – Izzy May 19 '16 at 9:47

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