AIS tracks of converging vessels_cred MAIB.jpg. Caption: Satellite navigation such as GPS and AIS used in shipping has ‘vulnerabilities’ that could be backed-up be eLoran radio navigation. Credit: MAIB
The UK government has signalled support for establishing a land-based eLoran radio navigation system as a backup for satellite navigation systems such as GPS amid concerns of satellite navigation reliability.
In response to a paper highlighting that Global Navigation Satellite Systems (GNSS), which includes GPS, has “various vulnerabilities to failure”, such as continuity and accuracy failings, the UK Minister for Implementation, Caroline Noakes said it is important that the UK government establishes “an alternative to these satellite systems which does not suffer from the same vulnerabilities”.
The paper, Economic Impact to the UK of a disruption to GNSS, written by policy and economics consultancy London Economics, estimates that the cost of a five-day disruption to GNSS for the UK would run in at £5.2bn, also highlighting that the maritime sector would suffer major disruption and a loss of £1.1bn gross value added.
Caroline Noakes, who was Minister for Implementation when the report was written last year, said that based on the reports assertion, eLoran offers a “technologically dissimilar system” that provides a resilient alternative to satellite systems. She added that the UK government would be “supportive of any progress towards initiating and maintaining an operational eLoran network that can provide position, navigation and timing services and will lend support where appropriate to aid its establishment and continued use”. The comments made by Noakes were made July last year but have only just been released, and have since been adopted by her successor Oliver Dowden.
This response comes in the light of an increasing reliance on GPS and alternative satellite navigation systems by a wide range of users, including the maritime sector, which uses it for navigation and safety systems such as AIS. Weak signals from GPS satellites can be readily jammed using cheap equipment that can be bought on the Internet and has raised reliability concerns in the maritime industry following reports of suspected GPS-spoofing in the Black Sea in June 2017.
ELoran is based on the old Loran C radio navigation system but can provide much greater accuracy, equivalent to that of GPS. The land based system uses powerful signals at a low frequency which are much harder to jam, and can provide the essential timing signals upon which so much modern infrastructure depends.
To establish eLoran would mean erecting tall transmitting towers or re-establishing the ones from the old Loran stations. In Europe it would require international agreement because the system needs transmitters in a range of countries to provide the necessary coverage over Northern European waters. It appears that the EU is showing little interest in promoting eLoran as a back up system because they are spending large amounts of funding on their Galileo satellite system that is similar to GPS and thus equally vulnerable.
However, if eLoran does become established as a back up, there are questions around which system you believe if both are showing different positions. Professor David Last, a navigation expert commented, “The integrity requirements that both GNSS and eLoran are required to demonstrate are very tough to meet but the probability of a serious discrepancy is very low. If one system fails then it should show a blank screen not wrong information.”