This made it much easier to implement the receivers using 1940s electronics.Īnd, unlike LORAN, Decca was not known to the Germans and thus free of jamming. The system used a phase comparison of two low-frequency signals between 70 and 129 kHz, as opposed to pulse timing systems like Gee and LORAN. The Decca Navigator System was a hyperbolic radio navigation system that allowed ships and aircraft to determine their position by receiving radio signals from fixed navigational beacons. The Decca system for hyperbolic navigation was invented in the U.S., but development was carried out in the UK. Hyperbolic navigation and the Decca system As a result of advances in microelectronics, LORAN-C receivers dropped significantly in price, and earlier generations of LORAN were mostly abandoned. The third-generation called LORAN-C became available and offered a longer range and location accuracy of a few tens of feet. With advanced electronics, system costs came down, and automated receivers became available. It was first used for ship convoys crossing the Atlantic Ocean, and then by long-range patrol aircraft, but found its main use on the ships and aircraft operating in the Pacific theater during World War II.Įarly LORAN equipment was expensive, limiting its use to military and large commercial users. Still, it operated at lower frequencies to provide an improved range up to 1,500 miles (2,400 km) with an accuracy of tens of miles. Gee inspired the original LORAN system developed in the U.S. Other navigation information can be used to determine at which intersection the receiver is located. The receiver is then located at one of the two intersections. Each time difference can be used to locate the receiver on a hyperbola branch focused on the ground stations. That is, t A, t B, t C is unknown, but t A – t B and t A – t C are known. The times it takes for a radio signal to travel from the stations to the receiver are unknown, but the time differences are known. In the figure above, the three ground stations A, B, C, have known locations. Hyperbolic navigation example (Image: Wikipedia) The first hyperbolic navigation system was to be used operationally, entering service with RAF Bomber Command in 1942. It measured the time delay between two radio signals to produce a location, with accuracy on the order of a few hundred meters at ranges up to about 350 miles (560 km). Hyperbolic navigation technologies were independently developed in the U.S. Today, the enhanced LORAN (eLORAN) system has been offered a more secure alternative to GPS. Starting with developments in the 1930s and 1940s, land-based long-range navigation (LORAN) systems using hyperbolic navigation have been continuously advanced. Terrestrial-based hyperbolic navigation technologies predate today’s satellite-based global positioning system (GPS).
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