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Chicken Little report: Sat-nav dependency spells DISASTER!

Quango pushes 1940s tech as backup for GPS

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GPS jamming trial caused chaos on ship's bridge

The fact is that accurate eLORAN is more a goal than a reality. It might prove capable one day of meeting a US Coastguard requirement calling for "8-20m" accuracy, but this hasn't been demonstrated: and such performance is marginal at best for most modern GPS applications. It is unacceptable for future ones that will call for sub-1m accuracy, such as lane control on the motorway and so forth.

The GLAs prefer to talk about a trial they did in which they used differential eLORAN – that is LORAN enhanced by the use of a nearby ground station sending error corrections, as with dGPS. Naturally this is right up their street. As the GLAs' document The Case for eLORAN tells us:

Initial differential eLoran trials conducted at Harwich in April 2006 have demonstrated horizontal positioning accuracies better than 9m with 95 per cent confidence using modern, miniaturised eLoran receivers. This puts eLoran on the same basis as single frequency GPS or Galileo: each requires differential corrections to guarantee meeting the International Maritime Organisation's future accuracy requirements for port approach and restricted waters.

This is disingenuous at best: in no way does <9m with differential assistance put eLORAN "on the same basis" as satnav for accuracy. Given the same conditions, differential GPS or Galileo would be accurate to within a metre, an order of magnitude better than eLORAN. Both systems promise sub-metre accuracy unassisted by ground station in future.

It's pleasing to see that the RAE report stopped short of outright recommending eLORAN as a mandatory backup for satnav, but it was still mentioned a lot: and the GLAs managed to slip into the appendices another recent trial of theirs in which they carried out GPS jamming using borrowed Ministry of Defence kit against one of their ships, NLV Pole Star, off Bridlington.

This apparently caused dangerous chaos on the Pole Star's bridge:

When Pole Star entered the jamming zone, numerous alarms sounded on the bridge over a period of approximately 10 minutes. These alarms were all linked to the failure of different functions to acquire and calculate their GPS position, which included: the vessel’s DGPS receivers, the AIS transponder*, the dynamic positioning system, the ship’s gyro calibration system and the digital selective calling system ... In the situation where a crew was not expecting this level of system failure then the distraction caused by so many alarms sounding at once could have had a significant effect ...

Some vessels have integrated bridge systems, which enable automatic execution of a passage plan on autopilot. If this system is operating at a time that jamming occurs, then the vessel's course and heading may change without informing the crew, potentially leading to extremely hazardous consequences.

Although the Pole Star's crew was expecting GPS failure, problems were experienced. The vessel's Electronic Chart Display & Information System (ECDIS) was not updated due to the failure of the GPS input, resulting in a static screen. ECDIS is the normal mode of positioning on board Pole Star (with paper chart backup) and during the periods of jamming some crew members became frustrated when trying to look at the ECDIS. This resulted in the monitor being switched off!

There are several questions raised by this trial, such as the ability of a vessel's crew to quickly revert to traditional means of navigation and also the extent to which they are able to navigate with these means. Given the greater reliance on satellite navigation, in particular GPS, these skills are not being used daily and are no longer second nature.

QED, then – we definitely need eLORAN! And differential eLORAN stations everywhere run by the GLAs, because eLORAN on its own isn't much good!

Actually, it seems that what we need is properly designed bridge hardware and properly trained watchkeeping officers. As a bridge watchkeeping officer myself from 1993 to 2001, I have been in the kind of situation described above far too many times: the Royal Navy minehunters I was handling gradually acquired nearly all the kit described above in early military forms (therefore highly unreliable forms).

A bridge watchkeeping officer who can't cope on passage without an electronic chart and automated collision warning is an unskilled monkey hardly worth paying: an "integrated" bridge that sounds multiple alarms for a single problem is not integrated at all (certainly none that I ever had charge of were, but one copes all the same). An ECDIS system which doesn't continue running an automated dead-reckoning plot (and display a growing circle of uncertainty) on losing GPS is badly designed. The ship's log – the speed readout, not the records book – and its compass could and should also serve as a simple safeguard against the "Hazardously Misleading Information" problem, where satnav or another electronic nav aid gives locations which are plausible but wrong.

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