Differential Loran

Differential Loran is a correction technique that improves LORAN-C or eLoran position accuracy by broadcasting local corrections from a reference station at a surveyed point. The reference station measures the difference between the time-of-arrival the signal should have and the value it observes, dominated by the additional secondary factor (ASF) from the signal’s path over land, then sends that correction to receivers within roughly a 35 km radius over the Loran data channel. Applying it pulls position accuracy from the bare LORAN-C figure toward about 8 to 10 m. The method is the terrestrial parallel of differential GNSS and was developed to make eLoran a backup to GPS for both position and timing.