Modeling and Correction Methods for Positioning Errors in Loran System at Sea

Loran is a crucial maritime navigation system and is also considered a key backup for satellite navigation systems. To enhance positioning and timing services, improving the accuracy of the Loran system is essential. This paper discusses the factors affecting Loran’s positioning and timing performance, with a focus on ASF (additional secondary factor) measurement techniques and filtering methods. This study specifically addresses challenges in maritime navigation and employs a first-order Gauss–Markov process to simulate ASF+SF values. This approach eliminates the need for precise geodetic distances or real-time GNSS corrections. The research included experimental tests conducted along the eastern coast of China, evaluating environmental conditions and the positioning station’s location data. Positioning calculations were performed under maritime navigation conditions. The experimental results demonstrate that when satellite navigation systems are unavailable, the proposed model significantly enhances navigation accuracy. The accuracy, previously at the level of several hundred meters, was improved to approximately 40 m, making Loran a more reliable alternative for maritime applications.