GNSS is widely used as a source of timing and synchronisation for a broad range of market sectors, particularly in Military and Critical National Infrastructure applications. Whilst GNSS under steady state conditions can provide excellent timing and stability accuracy, it is well known that GNSS is vulnerable to the effects of jamming, spoofing and space weather. In recent times there has been a significant increase in the number of GNSS jamming and spoofing incidents around the world. Due to such threats, there is now a strong and growing interest in developing alternative timing and synchronisation techniques and technologies that do not rely on GNSS and can therefore provide more resilient and robust timing delivery to critical applications. This paper presents the capability of eLoran technology to provide an alternative broadcast of highly accurate timing and navigational signals utilising high power terrestrial transmitters that do not exhibit exposure to the known vulnerabilities of GNSS. eLoran signals are however exposed to signal propagation delays called Additional Secondary Factors (ASF) which must be compensated for to ensure accurate UTC alignment at the user segment and this paper includes ASF data analysis from previous research activities in this area.

In recent years, the world has come to recognize dependencies of devices and systems that employ GNSS as the primary source of PNT. Regions of conflict are characterized by widespread areas of GNSS denial from both jamming and spoofing. This has led to increased interest in eLoran’s wide area coverage and orthogonal failure modes to GNSS. All eLoran services (by definition) have certain characteristics and capabilities. These were developed and detailed in the US FAA Technical Evaluation report in 2004 that proved a properly modernized Loran system (i.e., eLoran) operating in the internationally protected 90-110kHz band, could meet the requirements for RNP 0.3 in aviation, 10–20-meter accuracy for Harbor Entrance and Approach for maritime applications, and continue to be a stratum-1 frequency source adding UTC traceable time for precise time applications. This presentation will include a brief comparative review of eLoran vs Loran-C. Current and recent projects will be described in the context of use cases addressed, and detailing the current state of the technology. The potential capabilities and benefits of adding encryption are discussed. We also provide several examples of real-world data.

Multipath and skywaves are major sources of range errors in enhanced long-range navigation (eLoran), with early skywaves posing a particular threat to user safety by inducing range errors exceeding one kilometer. This study proposes a novel eLoran pulse design that mitigates skywave-induced range errors while fully complying with the SAE9990 pulse shape and spectrum specifications. Optimized pulse shapes are developed using genetic algorithms (GA), with transmitter-induced signal distortions incorporated by modeling the characteristics of the antenna and power amplifier. Simulation results demonstrate significant performance improvements: for a fixed skywave-to-groundwave amplitude ratio (SGR) of 0.3, the GA-based pulse designs reduce range errors by 51.9%. Furthermore, under simulated ionospheric polar-cap disturbance conditions with SGR values greater than 1, the proposed pulses effectively suppress early-skywave–induced errors. These results highlight the potential of optimization-based pulse shaping to enhance eLoran positioning accuracy under challenging propagation conditions.