GPS Forerunner is a term used to refer to the three technologies that preceded the Global Positioning System (GPS). These technologies are MAP (3 letters), LORAN (5 letters), and ROADATLAS (9 letters). MAP stands for Microwave Anisotropy Probe, which was a satellite-based navigation system developed by the United States Navy in the 1950s. LORAN stands for Long Range Navigation, which was a hyperbolic radio navigation system developed by the United States Coast Guard in the 1940s. ROADATLAS stands for Road Atlas, which was a system of ground-based navigation beacons developed by the United States Army in the 1930s. All three of these technologies were important precursors to the development of GPS.