Feature 4 | COMMUNICATIONS & NAVIGATION EQUIPMENT Getting out of a jam
Te widespread availability of GPS jammers poses a potential threat to coastal vessels that rely on this service. However, recently hosted sea trials have identified a successful back-up solution
G
PS serves a valuable real-time tracking function but, as with many technologies, it is not fool-proof.
Although such devices can bolster security and safety aboard private yachts, leisure craſt, fishing vessels and coastal craſt, some form of redundancy is advised should the service be disrupted. GPS signal reception can be interrupted
by a number of factors, the most common being space weather effects, obscuration of the system antenna and hardware failures affecting the receiver, antenna and/or cabling. However, some industry experts have expressed concern over a new potential source of signal interruption, namely GPS jamming – either by accident or as an intended means of disruption. Dr Alan Grant, principal development
engineer at the General Lighthouse Authorities of the UK and Ireland (GLA), tells Ship & Boat International: “GPS jamming is relatively uncommon at present, but more and more cases are being reported as the different monitoring networks grow. We are not aware of any notable cases around the UK coastline, however jamming events have been observed along the UK road network.”
Widespread jammers These concerns have particularly been prompted by an increase in availability of GPS jamming solutions; some of these can be sourced online for as little as GBP£30 (US$45), putting them well within the reach of potential troublemakers, from serious criminals to bored teenagers. Even some of the most low-end jamming devices are capable of causing complete outages across the majority of available receivers, Grant claims. Such devices need not even be intentionally
utilised for criminal ends to cause disruption, Grant adds. He says: “It is likely that most cases observed are people using jammers marketed as privacy protection devices [PPDs], which are marketed as units that can stop your vehicle from being tracked. However, they often prevent GPS signal reception well beyond the
62
vehicle. While this can be classed as ‘deliberate jamming’, the effect is oſten more than the user intended.” However, he concedes, some reports of GPS jamming have indeed been linked to criminal activities. Martin Bransby, research and radio
navigation manager, GLA, adds: “Te more dependent we become on electronic solutions, the more resilient they must be. Otherwise, we face a scenario where technology is actually reducing safety rather than enhancing it. Demands on marine navigation are only getting tighter, yet electronic systems at sea are primitive compared to those used in air travel. Tis needs to change.”
Seamless switch In response, GLA has previously conducted two trials, in 2008 and 2010, dedicated to pinpointing a work-around solution in the event of GPS service denial. In March this year, the organisation struck gold aſter the successful conclusion of a sea trial in which a back-up service was demonstrated. Conducted in tandem with the Accessibility
for Shipping, Efficiency, Advantages and Sustainability (ACCSEAS) Project, which aims to improve safety and efficiency within the North Sea, the trials, which were hosted on board the 84m loa Trinity House lighthouse tender Galatea, showed that deployment of eLoran technology created an automatic and seamless stopgap for critical data transmission when GPS service was deliberately jammed. eLoran, or ‘enhanced Loran’, builds on
the established Loran low-frequency radio system that enables vessels to keep a fix on their position and speed. The enhanced version differs in that it is able to offer accuracy within 8m, and also uses a series of additional pulses that can transmit digital GPS (DGPS) corrections. Grant comments: “eLoran is able to provide
position, navigation and timing [PNT] information independently to GPS, but it needs a separate system to swap the feed to the bridge systems. Technically, though, this could be built into the receiver.
“In the case of the ACCSEAS Project,
the prototype PNT data processor monitored the performance of GPS and eLoran separately and completely independently. By reviewing a number of quality measures, it was then able to identify when there was a problem with GPS, and automatically switch the output to eLoran.”
Equipped for the future Currently, there are eight Loran stations located in the North Sea region, but few vessels are equipped with adequate receivers to utilise this service. For now, the prototype PNT system used in the Galatea trials is yet to be submitted to testing for approval by IMO, the flag states and/or class societies, but GLA believes that a combined GPS / eLoran unit would be the most logical move. Whether this substitute service takes
off remains to be seen, but the trials have proven eLoran’s capability to fill in for GPS in periods of disruption, and several steps have already been taken
in this
direction. In January 2013, for instance, a Loran station was activated in Dover, UK, to aid vessels in obtaining port approach level accuracies via eLoran. Meanwhile, P&O Ferries is reported to have installed an eLoran receiver aboard one of its vessels. GLA predicts that, by 2019, all major UK ports will boast full eLoran operational capability. At the heart of this story, however, lies an important message; chiefly, that over-dependency on any one type of technology is inadvisable and impractical when it comes to covering all safety and security angles. Or, as Martyn Thomas, vice president at the Royal Academy of Engineering, has commented, specifically about the sea trials: “The dangerous over-reliance on GPS makes it a potential common point of failure for many systems, so any technology that can provide resilience to these systems should be welcomed across the board.” SBI
Ship & Boat International May/June 2013
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90