There is a misconception among some that the mere presence of GPS in any device means that it can be tracked by a government, corporation, or other malicious actor.
It’s actually a pretty reasonable misconception, considering that the most widespread usage of GPS receivers in the world is in smartphones. And unless you have taken some very specific precautions, your smartphone probably is being used to track you in some capacity.
But this is not because GPS is some sort of spy technology that beams your location data to satellites so the satellites can tell you where you are and also your personal FBI guy. The spying comes from the software running on the phone itself and its connection to the terrestrial corporate/government spyware networks.
The reason we’re talking about all this is because some handheld radios are coming out now that have GPS receivers built in. Some people are concerned about this because they intend to use the radios as a method of communication that involves less spying. That’s a complex topic in and of itself, but it’s basically a reasonable thing to do considering some of the alternatives.
GPS is a receive only service. It works based on the principle of time-of-flight and geometric triangulation. Different though it is from celestial navigation, it actually relies on the same basic principle: If you know what time it is and what you’re looking at, you can figure out where you are.
GPS satellites fly on extremely well-known orbits and constantly broadcast a data stream of their position and the current time extremely precisely. Your GPS devices receive this stream from several satellites at once and then use the time difference between transmission (encoded in the stream) and receipt (onboard device clock) to calculate the signal’s time of flight from the known speed of light.
This gives a distance to each satellite, and a known position of each, allowing some basic trigonometry to be used to calculate the receiver’s position. At no point in this process does a receiver transmit any signal.
The reason some radios have GPS built in is because it can be used in conjunction with a service like APRS to squawk out your location to the wider network, or to let team members know where each person is in relation to each other. Either way, this is something that has to be set up intentionally. You will know if you’re broadcasting your location to the world.
Modern GNSS receivers also use the Russian, European, Japanese, Indian, and Chinese GNSS Sat systems in addition to GPS.
While the US government can disable GPS for civilians at will, they cannot detect you through its use. Nor can any of the other nations’ systems.
If you happen to be concerned about internet-connected devices reporting your location to some server somewhere, there are standalone navigation devices that have no network connectivity. Garmin Etrex is one example, but there are plenty of older GPS devices that people used to mount in their cars that can be found inexpensively. The maps can sometimes be updated by loading up an SD card with up-to-date map tiles. You can also use more privacy-respecting navigation tools like OSMAnd or OrganicMaps, or you could learn to use a paper map and compass like your parents did.
Of much greater concern than spying is GPS jamming and spoofing. Here’s some information about that.
https://hackaday.com/blog/?s=GPS+spoofing
https://www.flightradar24.com/blog/inside-flightradar24/gps-jamming-map/
