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Could pen-sized GPS jammers paralyse UK shipping?

Obsolete satnav rivals troll for security pork

By Lewis Page, 19 Jun 2008

Analysis Contractors and sector-straddling quangocrats sought yesterday to convince politicians of the need to spend defence or security funds on radio-based backups for GPS satnav, according to reports.

The BBC, covering recent Commons defence committee testimony, gives serious play to the contention by VT Communications and Trinity House that Loran radio-station signals - while not, perhaps, making much commercial sense - are worth funding for the security benefits they bring.

The Beeb quotes Doug Umbers, of VT Communications, as saying that a pen-sized device could prevent ships in a port from receiving satnav signals, whereas a huge field of jammers would be required to deny Loran service.

Sally Basker of the General Lighthouse Authorities (GLAs) told the Beeb that "GPS and Galileo have the potential to do great things ... satellite navigation has got into our critical infrastructure but we know that it has some weaknesses".

VT Communications has a contract from the GLAs to run trial Loran transmissions at its government-services radio station in Cumbria. The GLAs are an alliance of the lighthouse authorities covering the UK and Ireland: Trinity House, the Northern Lighthouse Board and the Commissioners of Irish Lights. The alliance is funded by a special tax on shipping, the "light dues" charged to ships calling at UK and Irish ports. Apart from its role as an arm of government, however, Trinity House also operates as a commercial offshore contractor, deep sea pilot bureau and mariners' charity.

Since the advent of GPS as a serious contender for maritime navigation in the late 1980s, most other electronic navaids have withered on the vine. The UK formerly maintained chains of Decca radio stations, using similar technology to Loran but shorter-ranged, erratic, expensive to run and typically difficult to use. (Your correspondent, as a navigating officer in the early 1990s, was occasionally forced to use Decca).

The only thing that really kept Decca and the rest going was the fact that for a long time the USA deliberately degraded the accuracy that civilian GPS users could get - using so-called "Selective Availability" (SA) technology. However, in the early 1990s SA became largely irrelevant as a workaround called Differential GPS (DGPS) became common. With DGPS, a ground station at a known location works out the error in the civil GPS signal and continuously transmits corrections to GPS users in the region. This makes an ordinary GPS user, without the codes needed to read the military signal, able to get accuracy as good as 1m - as opposed to say 150m under SA.

As paid-for commercial DGPS became widely available, the always fairly rubbish Decca became totally outmoded and it was finally shut down in 2000. (The only people who really liked it by then were old-school fishermen.) Funnily enough, SA was switched off on the orders of President Clinton the same year, making ordinary free GPS accurate to 20 metres or better. In 2007, the US announced that it wouldn't even build SA kit into its future GPS satellites. For those worried that civil GPS service might be denied altogether - an option the US reserves, though extremely unlikely to be exercised off the British coast - it now appears certain that the interoperable European Galileo system will be operational during the next decade.

These developments could well be said to have made the GLAs' free to air British-Irish network of 14 DGPS stations - which they only got round to setting up rather late, in 2002 - as much things of the past as SA and Decca. Certainly the shipowners who are compelled to pay for them probably wouldn't choose to do so voluntarily. Nor, most likely, would they choose to pay for Loran.

Loran is somewhat better than Decca but it's based on similar 1940s tech. It's only accurate for most navigational purposes - say, for finding your position on a chart - to around 200 metres. As with Decca, however, Loran can be used to return to a given point under similar propagation conditions with accuracy as good as 50 metres. What it can't do is tell you accurately where that point is in terms of coordinates. (This was why traditionalist fishermen liked Decca. They could use their favourite "lanes" to avoid fouling seabed gear such as beam trawls or scallop dredges on wrecks or rocks whose positions weren't accurately laid down. Those who have seen the effects of beam trawls and scallop dredges first-hand are sometimes less convinced of the benefits.)

Loran and Decca are only marginally useful even in the maritime or aviation environments, mainly for longer-haul navigation in areas where they're available. Across much of the world, you have to rely on GPS or dead reckoning. Loran's no good for piloting a ship into a harbour or a plane onto a runway, as GPS or DGPS can be. And it's no real use whatsoever for minicab drivers, truckers etc. trying to find a given street address in an urban environment. Seriously - no matter what VT and the GLAs would like to tell you.

All in all, then, the future doesn't look too rosy for the GLAs' radio-station branch and VT Communications. Commercial shipowners don't want to pay for their stations, and if their protests got noisy enough someone might seriously start taking a look at the light-dues levy and the somewhat anomalous status of Trinity House - straddling as it does the public, private and "third" sectors.

So there's a need for a new source of revenue - and what could be better than the defence budget? Though the MoD is very hard up at the moment, it wouldn't particularly notice the expense of running Loran.

To get defence/security cash, though, you need a scare threat. Hence, the dreaded pen-sized device which could shut down a major container port or oil terminal and paralyse the British economy.

Hold on, though. Your correspondent used to move ships in and out of British harbours for the navy, back when ordinary GPS was SA-crippled and DGPS cost money directly and thus wasn't normally given to you. If it was foggy and you couldn't navigate in and out of harbour visually, you didn't fool about with Decca and nor would you do so with Loran - they just aren't accurate enough for harbour pilotage. You would use radar, like a sensible person.

And that's what the merchant skippers and harbour pilots still do, in the real world. Radar is the real backup for GPS, when operating anywhere near a coast. Far out at sea where you can't navigate by radar, people can't jam your satnav - not without following you around - and anyway, it takes long enough to get anywhere that the weather will clear sooner or later and you can get a fix with your trusty sextant as of old.

As for jamming radar, that's not something you do with a pen-sized device (actually, nor is jamming GPS; but it's true that jamming GPS is relatively simple). You'd be found and switched off easily if you tried that kind of caper on any effective scale.

It's quite disingenuous of VT Communications to tell politicians that they need Loran in case of GPS jamming in harbours, then. And it's probably a bit naughty of the GLAs to imply that they need tax money - either from shipowners, or even less justifiably from ordinary people like you and me - to run DGPS and Loran stations on such a basis. Especially if that cash is to come from the Defence budget, which frankly has quite enough calls on it just now.

On the other hand, if governments are to piss away cash on domestic security panic, Loran is at least more useful than, oh, biometric ID cards, or a nationwide surveillance-cam network, or urban nerve-gas propagation research or airport mind probes. Why don't Umbers and Basker take their pitch along to the Home Office? ®

Lewis Page was a Royal Navy officer from 1993 to 2004. In the early '90s he was navigating officer and precise-nav officer for minewarfare purposes, employing many recondite technologies of the times including Decca, DGPS, Hyperfix et al. He was also a diver, and once spent six months on fishery patrol duties.

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