An Improved Accuracy Model Employing an e-Navigation System

eLoran needs to satisfy the user requirements for accuracy, availability, continuity and integrity to fulfil its envisioned role as a backup system to GPS. The eLoran accuracy performance at receiver locations is dependent on the variations of the Additional Secondary Factor caused by changes in the ground conductivity. This paper focuses on eLoran accuracy performance analysis for maritime harbour entrance and approach. Based on observational ASF data, a new, updated and more accurate empirical model for eLoran time of arrival variance that improves upon the existing models in the literature is proposed. The time of arrival variance algorithm developed herein incorporates the long-term effects of the changes in terrain conductivity on the pseudorange measurement errors of the received signals at the user's receiver location. The developed model has been used to determine the diluted position accuracy of eLoran over the North European maritime region, and for harbour entrance and approach (HEA) for SOLAS ports in Ireland and United Kingdom. The results show that if the European eLoran system was reintroduced, positioning accuracy of less than 20 m would be achievable in the North Sea and less than 10 m at the SOLAS ports if differential Loran was also available there. These would meet the navigational requirements for HEA. However, in the Irish sea down through the Bay of Biscay, the positioning error would exceed 80 m and be unacceptable for marine navigation, especially compared to GPS. This suggests that the inclusion of two or more eLoran transmitters located further South-West of Ireland are needed to enhance coverage in this area. The results of this work can also provide the radio planners and authorities regulating sea traffic with the insight of where to deploy new resources such as reference stations.