LORAN-C was a medium-range hyperbolic radio navigation system that the US Coast Guard operated. It enabled receivers to determine their positions by using multilateration principles. This involved comparing the differences in reception times of low-frequency radio signals from fixed, land-based radio beacons. Each group of beacons, known as a “chain,” included one “Master” beacon and two to five “Secondary” or slave transmitters. Although LORAN was officially decommissioned in 2010, some parts of the system are still used as a backup for the Global Positioning System (GPS).
The LORAN system, which stands for LOng RA nge N avigation, was developed in the United States during World War II. It resembled the British GEE system but utilized lower frequency radio waves, allowing for a longer range of up to 1,500 miles. While this extended range resulted in lower accuracy—often within tens of miles—it was considered acceptable. The GEE system was reserved for short-range navigation, while LORAN catered to longer distances. Initially, LORAN found use in ships and aircraft operating in the Atlantic theater, later expanding its application in the Pacific.
The acceptance of LORAN’s longer range, albeit with lower accuracy, required a shift to lower frequencies. These frequencies could reflect off the ionosphere at night, providing