LORAN is a navigational system which relies on signals from radio transmitters. For much of the second half of the 20th century, this system was in use by navigators all over the world, from casual sailors to national fleets, and it radically increased the reliability of navigational measurements, making ocean travel much safer. This system has largely been displaced by global positioning satellites (GPS) and their associated navigation systems, which are extremely accurate and very affordable.
LORAN is a clever abbreviation of long range navigation. The earliest LORAN systems were developed in Britain prior to the Second World War, and the technology was refined at the Massachusetts Institute of Technology in the 1940s by researchers for the American military. When the technology was first released, it had a fairly limited range, despite the name, and its use was restricted to the military. Over time, the range and applications of LORAN were expanded, with LORAN-C, which operates in the 90-110 kilohertz range, becoming the system in most widespread use.
The science behind this method of navigation is fairly simple in principle, but it took some time to refine in actuality. A LORAN receiver is capable of receiving pulsed tones from radio transmitters. Since the receiver knows where the transmitters are located, it can use the pulses to triangulate its position, as long as it can pick up signals from two transmitters. Nautical charts typically included transmitter data for the reference of navigators.
There were a number of problems with this system. The transmitters had to be highly accurate and precisely synchronized to ensure that they gave out accurate data, and the radio waves were subject to corruption as they traveled. Bad weather and poor atmospheric conditions could interrupt a LORAN signal, making it impossible for a navigator to get a fix on his or her position, and this was a serious risk. The computer systems for navigation were also very expensive to install, and the maintenance could be intensive.
As GPS became more readily available, many people switched from LORAN, although several governments such as the United States and Russia continued to maintain and use their LORAN systems. Some enthusiasts also started promoting enhanced or eLORAN, which blends LORAN with other navigation systems to create a complementary system which is less likely to break down. If one system fails, a navigator can simply use another to safely determine where in the world he or she is located.