Who invented the GPS unit?

The invention of the Global Positioning System is credited to Roger Easton, Bradford Parkinson and Ivan Getting. Easton is prominently cited as being the lead developer of the GPS team; he had been working on satellite-based location systems for the Naval Research Laboratory since 1955.

The contemporary GPS system was initially conceived as a U.S. Department of Defense project. Its concept was to make nuclear and conventional forces more accurate by providing fine location discrimination. Development and launch of 24 satellites making GPS technology initially possible began in the 1960s and lasted until the system became operational in 1995. The system was opened up to civilian use in 1996 by a policy directive of former President Clinton.