SHORAN is an acronym for SHOrt RAnge Navigation, a type of electronic navigation and bombing system using a precision radar beacon. It was developed during World War II and the first stations were set up in Europe as the war was ending, and was operational with Martin B-26 Marauders based in Corsica, and later based in Dijon and in B2-6's given to the South African Airforce in Italy. The first 10/10 zero visibility bombing was over Germany in March 1945. It saw its first combat use in the B-25, B-26 and B-29 bomber aircraft during the Korean War.
SHORAN used ground-based transponders to respond to interrogation signals sent from the bomber aircraft. By measuring the round-trip time to and from one of the transponders, the distance to that ground station could be accurately determined. The aircraft flew an arcing path that kept it at a set distance from one of the stations. The distance to a second station was also being measured, and when it reached a set distance from that station as well, the bombs were dropped. The basic idea was similar to the Oboe system developed by the Royal Air Force, but in Oboe the transponder was on the aircraft. This limited Oboe to guiding a single aircraft per ground station, while SHORAN could guide dozens, limited only by how rapidly the ground station's transponders could respond.
SHORAN was sent into combat due to the presence of the MiG-15 over Korea, which drove the B-29's from daylight combat in June 1951. Night operations were not very productive and the US Air Force became interested in any way to improve their results. The system was in place and the crews trained by November 1952, and SHORAN remained in use from then until the end of the war. It was particularly effective during early 1953 when the North Korean Air Force began to re-equip in case a new offensive opened. B-29's began the campaign, but only a dozen aircraft were available, so they were soon supplanted by B-26s to maintain constant bombing of the airfields. The possible offensive never occurred; the armistice was signed in July. It was not used after that point, due to Strategic Air Command's increasing focus on long-range bombing with nuclear weapons. Although SHORAN was used by the military only briefly, surplus equipment soon found a new use in the oil and gas industry, where it was used to position ships with high accuracy for seismic measurements.