Loran-C

Loran-C is a radio navigation system that compares the difference in reception times of low frequency radio waves from onshore beacons. Loran stands for LOng RAnge Navigation. The letter “C” refers to an improved, more accurate system (the original system is referred to as Loran-A). Its use is similar to that of radio direction finders, but is capable of operating over larger distances. It had largely supplanted the non-directional beacons used by RDFs by the 1970s.