A Demonstration of High Accuracy Loran-C for Harbor Entrance and Approach Areas

The U.S. Coast Guard has operated the Loran-C system in the United States since 1958. The current system of 24 Loran Stations provides a stated absolute accuracy in navigation position of 0.25 NM. There has been interest in recent years in using Loran-C as a back-up system in case of the loss of GPS; especially in Harbor Entrance and Approach (HEA) areas. The Coast Guard Academy in conjunction with the Coast Guard Loran Support Unit (LSU) is going to be conducting a demonstration of the potential of Loran-C to support the HEA navigational requirements. The purpose of this demonstration is to prove the capability of Loran-C to meet the required accuracy of 8-20 meters. In order to meet these accuracy requirements user receivers must use Additional Secondary Factors (ASFs) in calculating the user position. For a given HEA, a grid of ASF values will need to be created, to take into account the spatial variation in the ASFs and updates to the grid will need to be transmitted to the user in order to account for temporal variations in the ASFs. This paper describes the issues and problems to be overcome, the approach to overcoming those problems, and a design for the demonstration to occur later in 2003.