DECCA was a
radio navigation system used until March 31, 2000. Now superseded by
GPS, DECCA used radio signals in a band ranging from 70 to 130 kHz.
Introduced in 1944 for the WWII invasion in Normandy known as D-Day, where the system was used to navigate ships through mine fields with a precision only matched by today's differential GPS.
Commercial DECCA navigation receivers became available as early as 1945.