Even when operating at optimum efficiency, GPS satellite outputs are weak - the high frequency and low wattage at the transmitter means that, by the time the signal reaches the Earth the strength is so diminished, receivers frequently decipher noise as opposed to clear signals. The eLoran system delivers the radio signal at up to one million times stronger than GPS.
Solar flares and other cosmic phenomena, as well as purposefully employed personal protection devices (satellite jamming systems), lead to GPS outages and failures. The reasons behind jamming are more benign than malicious; intercontinental vehicles apply GPS jamming signals to avoid toll charges, the technology can be purchased online for a fraction of the costs they stand to incur. When at sea these jamming signals pose little threat to the superyacht fleet, an outreach of hundreds of metres is hardly a hazard on the open ocean. However, in instances where these jamming signals have not been turned off and a vessel approaching port is carrying vehicles employing them, proximity becomes a much more immediate and dangerous proposition.
Martin Bransby, research and radionavigation manager at the General Lighthouse Authorities of the UK and Ireland explains:
“Shipping lanes are becoming busier and more perilous than ever, whilst mariners are becoming increasingly reliant on one, fallible, source of PNT (position, navigation and timing) data. This presents a significant risk to the safety and efficiency of vessels, particularly in congested areas like ports. eLoran reduces the vulnerability of vessels by ensuring the uninterrupted provision of position, navigation and timing data, even when GPS is down. As a terrestrial system, eLoran signals are much stronger when received than GPS, making it exceptionally difficult to interrupt.”
It is easy to take GPS for granted. For most it will always be there, but it is shortsighted to believe that this will provide safe passage for everyone on every occasion. If the satellites that provide the signals do, for some reason, fail, fixing them is by no means quick or easy. eLoran not only provides a backup, it provides a system that can be managed from the ground in case of emergencies.
Still in its infancy the testing phase has been positive and the product has been adopted by a number of shipping companies. It has been highlighted from the offset that eLoran is not a replacement for GPS and superyacht operators should bear in mind that, as yet, it is currently only operating from the British coastline and to a limited degree in Europe, but it does provide accuracy to within 20m (5-10m when approaching port as the IMO requires).
Designed as a coastal failsafe with a range up to 1000km, this land-based technology does not offer the global outreach of GPS. Nonetheless, with due diligence on the rise, and safety always top of the agenda, with system redundancy an expected prerequisite, it stands to reason that technology as critical as GPS should finally have shoulders to lean on.
Bransby continues, “By replacing the receiver and adding another antenna and cable run on board, it is possible to have integrated receivers – or ‘multisystem receivers’. These systems make it possible to run both GPS and eLoran simultaneously, allowing both sets of navigational data to feed into the on board systems, giving you one resilient output on your navigation display. If one fails the other will automatically take up the slack. Multisystem receivers were on the IMO’s agenda for the most recent National Centre for Sensor Research meeting.”
Progress is also being made with the Radio Technical Commission for Maritime Services (RTCM) for eLoran receiver standards and specifications. Although the RTCM is an American body many of their standards filter into the maritime technical community at large.
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