GPS broadcasts several signals, the higher precision ones are encrypted - until 1999 GPS was encrypted at much lower resolution but the army and armies it share

GPS broadcasts several signals, the higher precision ones are encrypted - until 1999 GPS was encrypted at much lower resolution but the army and armies it shares its tech with still operate at a higher resolution. The US can lock countries out of higher resolution GPS at will - this (and GLONASS) make sense because of it.