Meteorological influence on eLoran accuracy

Stringent accuracy requirements need to be met for eLoran deployment in marine navigation and harbour entrance and approach. A good accuracy model is therefore required to predict the positioning accuracy at the user’s receiver locations. Accuracy depends on the variations of additional secondary factors (ASFs) and the primary factor delay. The changes in the air refractive index caused variations in the primary factor (PF) delay of the eLoran signal, and current eLoran accuracy models do not take this into account. This paper proposes an improved empirical accuracy model that considers the contributions of changes in the refractive index of the air, often classified as a short term effect. The changes in weather parameters such as atmospheric pressure and temperature increase the time of arrival variance. The developed accuracy model is used to predict the eLoran positioning error in the European maritime region. The results show that the short term ASF variations significantly contribute to the positioning error and must be included in the accuracy model. The results also demonstrate that a 20 m accuracy or better would be achieved in the North Sea, while a 10 m accuracy would be achievable at the SOLAS ports if eLoran was reintroduced in Europe. Nevertheless, the repeatable accuracy around the Irish sea exceeds 80 m and does not meet marine navigation requirements compared to GPS. Coverage can be enhanced by including at least two eLoran transmitters in Ireland