GPS devices such as this have to do two things: They have to receive signals from at least three different satellites, simultaneously, in order to calculate their coordinates. This, essentially, requires line of sight view of three different positions in the sky. Then they have to somehow transmit this data to a responding site. This could be by Internet, or by radio signals. If they are transmitted by radio, the signal has to be very strong (much stronger than a blue tooth or wireless router signal) which would take more power than most computers would supply and would be easily detectable. If they are transmitted by the Internet, they obviously require an Internet connection, and would also be easy to detect.
Thanks for this information. I’m the one who alluded to GPS technology: technically, the article did not.
Would there be NO type of transponder of that size detectable by satellite (for example, I thought RFID devices were very small and inexpensive)? That is, does the device literally have to “transmit” a signal as opposed to having some form of unique “signature” detectable by satellite?
Put another way, if a satellite can detect something as small as neutrinos http://www.isv.uu.se/thep/talks/os/060505-SNOW.pdf why can’t it detect something on the ground that’s emitting an admittedly feeble signal? Sorry if this is an absurdly naive question. I’m not a technical person, so don’t waste time on a technical explanation. Your say-so “can’t be done” is fine by me. I’m just curious.