A
maritime navigation system that originated in the
United
States, and has later spread to the rest of the world. It is based on a system of
earthbound transmitters (
stations), which
encode time codes in
powerful radio
pulses in the 100
kHz band. When a
Loran C receiver on board a ship can receive
pulses from 3 different stations, it is able to
calculate the distance from them, and thus
the ship's
position, down to an accuracy of about 50
metres.
It is believed that it is on its way to be superseded by GPS, a navigation system using
the same basic principle, only with satellites instead of earth-based stations, but it
is still in widespread use, at least as a backup solution. This is because the Loran
C system has slightly less downtime than GPS has.
Loran is an acronym for Long Range Navigation. The C is a kind of version number. Loran A was the predecessor of Loran C, and was less accurate. Loran B, Loran D and Loran F were used only for U.S. military purposes; Loran E was planned, but never made it to the drawing board.