There is a GPS thing that happens in "some" countries where it is randomised.I have no idea how it works given that the GPS satellite signal cannot be tampered with ( it can be spoofed though), and the GPS co-ordinates do not align with the maps. It is offset by up to a km or so.
When it was just the US that had GPS there were 2 flavours. "Civilian" - which was guaranteed within 100 metres accuracy. And "Military" which was guaranteed within 10 metres.
This was achieved by encrypting the military feeds and introducing deliberate inaccuracies into the civilian feed.
This genius idea lasted about as long as it took me to type the above out. Immediately the global hacker community realised that if you took a GPS reading at a known location, you could work out the introduced error and then publish it (on a bulletin board if you can remember those days) so the rest of the world could enjoy 10 meter accuracy whether the US wanted you to or not.
Bill Clinton abandoned the practice.
Now you have a plethora of GPS providers and sub 1 metre accuracy is expected.
GPS is a touchy subject in the UK. We are frozen out of the really sexy parts of the Galileo GPS system that are delivering 21st century military capability as we are not EU members. And when the project was started the UK demanded that it only be available to EU states (France and Germany were happy to license it, but the UK
I stayed with a friend in Kenya in the early 90s and their Dad who worked in avionics at Wilson airport was aware of the GPS hack - it was hardly top secret.