Nutloose, Oi !
I am a yachtie, and while I am fortunate ( ? ) to be old enough to have learned to navigate without anything like GPS - in fact it was a science fiction dream to us then - many, many modern yachties would be buggered without it ( civil & amateur flyers, car users & ramblers etc too for that matter ).
When Gulf War 1 broke out, the U.S. cunningly put a spoof signal into the non-friendly GPS (as in everyone else but friendly military ) version; the system already had a built-in inaccuracy of 10-30 metres.
A lot of people found themselves in trouble, particularly sailors who found to their surprise they were doing 500+ knots at 10,000', which is unusual for most sailing boats.
The Iraqi's weren't that bothered, as they could barely read a compass and were on home ground anyway...
The built in error has since been discarded, and in my little boat if I zoom in I get a picture ( not google earth but real time ) of us alongside the appropriate jetty etc.
I think it's been accepted that the bad guys know even better than the good guys as to who is where...