Toward High-Precision Positioning for Enhanced Long-Range Navigation Systems: Principles, Progresses, and Practices

The enhanced long-range navigation system (eLoran), a terrestrial navigation system renowned for its strong anti-interference ability and long transmission distance, is internationally acknowledged as the most resilient backup for global navigation satellite systems. In this article, we first elaborate the positioning principle of the eLoran, from which we derive that three modules at the receiver, namely, sky-ground waves recognition, additional secondary factor estimation, and coordinate calculation, are critical to improve positioning accuracy. We then provide an in-depth review on the recent progresses on the design of each module, and rigorously discuss the main challenges imposed on the related algorithms for each module and possible future research directions. Finally, we adopt the practical measurement data to exhibit the state-of-the-art positioning results achieved by the currently most representative algorithms.