Developing resilient systems to counter GPS vulnerability

The modern world’s increasing dependence on global navigation satellite systems (GNSSs), such as the USA’s Global Positioning System (GPS), is well documented. So, too, are the risks inherent in placing so much trust in a single technological system that many see as insufficiently robust. In the summary of its November 2010 report Jamming the Global Positioning System - A National Security Threat: Recent Events and Potential Cures, the US National Space-Based Positioning, Navigation, and Timing Advisory Board said: “The United States is now critically dependent on GPS. For example, mobile phone towers, power grid synchronisation, new aircraft landing systems, and the future air traffic control system cannot function without it. Yet we find increasing incidents of deliberate or inadvertent interference that render GPS inoperable for critical infrastructure operations.”

In the marine environment, the need for a system or systems to allow mariners to check the accuracy of positions delivered via GPS and other GNSS is well understood. The General Lighthouse Authorities of the UK and Ireland (GLAs) are in the forefront of research and practical action in this field. In July the GLAs announced that seven differential enhanced Loran (eLoran) stations will be installed on the south and east coasts of the UK.

A recent demonstration of GPS vulnerability, if any more were needed, is the reported spoofing of the GPS on board a luxury yacht, carried out by a radio navigation research team from the University of Texas (see box). Spoofing is a technique that creates false civil GPS signals to gain control of a vessel’s GPS receivers. While signal blocking or jamming will normally raise system alarms on board a vessel, successful spoofing will not be detected by a ship’s navigation equipment unless it has another source of positional information to compare with the GPS-derived information. In this case, it seems that the yacht’s GPS devices found the team’s false signals indistinguishable from authentic signals.

The researchers, led by Todd Humphreys of the Department of Aerospace Engineering and Engineering Mechanics at the Cockrell School of Engineering, hope their efforts will highlight the perils of navigation attacks, demonstrating that spoofing is a serious threat to marine and other forms of transportation.

Dr Humphreys said, “With 90 per cent of the world’s freight moving across the seas and a great deal of the world’s human transportation going across the skies, we have to gain a better understanding of the broader implications of GPS spoofing. I did not know, until we performed this experiment, just how possible it is to spoof a marine vessel and how difficult it is to detect this attack.”

Technology of eLoran is seen by many as an effective, dissimilar backup system for GNSS. It is based on terrestrial long wave radio signals. It is independent of, and complementary to, GNSS. The UK is the first in the world to deploy this technology to provide alternative positioning, navigation and timing (PNT) information.

The roll-out, led by the GLAs, will replace the equipment in two prototype stations at Dover and Harwich, while five new stations will be deployed in the Medway, Humber, Middlesbrough, Firth of Forth, and Aberdeen. The GLAs have contracted UrsaNav for the deployment, to deliver initial operational capability by the summer of 2014. Full operational capability covering all major UK ports is expected by 2019.

The GLAs said that they are in consultation with several nations that hope to benefit from their knowledge and experience of eLoran and other resilient PNT technologies. South Korea wants to establish an eLoran alliance with the UK while it pursues its own roll-out of differential eLoran stations, due for completion in 2015. In 2012, South Korea was the victim of a 16-day GPS jamming attack by North Korea.

Many ship systems, including navigation and dynamic positioning, rely on GPS-based information. But GPS signals are vulnerable to both deliberate and accidental jamming. This is an increasing cause for concern because of the wide availability of GPS jammers online for as little as US$50, capable of causing complete outages across all receivers currently on the market.

Of course, eLoran can only fulfil its navigational safety role if ships operating in areas of eLoran coverage have the capability to take advantage of the service, said Martin Bransby, research and radio navigation manager at the GLAs. “Demands on marine navigation continue to increase and awareness of the vulnerability of GPS is growing, yet electronic systems at sea have not evolved at a sufficient pace to meet these challenges. Today’s announcement [about the seven eLoran stations] is a significant step towards improving safety at sea, but few vessels currently have receivers to take advantage of the new stations. We hope that the maritime industry will respond proactively to the new stations roll-out by installing eLoran receivers on more vessels.”

UrsaNav president and chief executive Charles Schue said that the GLAs’ project was the most advanced of its kind in the world. “The number of enquiries we receive about eLoran and other resilient PNT technology continues to increase and we are now approached for further information on a daily basis. Much of this is testament to the example being set in the UK, raising awareness of the need for a robust backup to GPS,” he said.

UrsaNav says that its specialised products include the Ursa Navigator (UN-100), a scalable PNT gateway system; a pirate alert and tracking system (PATS); a 3D Sonar System (UN-400); and a Loran-based low-frequency, small footprint terrestrial positioning system (TPS).

While differential eLoran provides a robust, effective backup to GNSS for those with the will and the economic resources to implement it, GNSS redundancy on a global scale will require a mix of solutions.

“GNSS systems have become the mariner’s primary aid-to-navigation but they have been demonstrated to be susceptible to jamming, interference and spoofing, leaving dangerous vulnerabilities in ships’ navigational abilities,” Mr Bransby explained.

“The need for resilient PNT data is clear, especially in high-risk areas like coastal regions, harbours, and congested shipping routes where collisions or groundings are more likely.

“Unfortunately, there is no ‘one size fits all’ approach to providing resilient PNT. Different systems will suit local geographical, operational and economic conditions. As such, we are supporting the development of a multi-system receiver approach that would integrate GNSS with a range of independent yet interoperable systems providing a wide scale, perhaps even global, solution over time.” Such systems could include inertial navigation, eLoran, ranging mode and e-Pelorus, for example.

“Crucially, we are also contributing to the establishment of standards for a multi-system receiver,” said Mr Bransby. “Of the candidate systems, eLoran is currently the most technologically mature and widely available. For many regions it also promises to be the most cost-effective backup.”

A formal business case for resilient PNT, compiled by the GLAs for the UK Government, has demonstrated eLoran to be the most economical solution for the UK and Ireland, with a benefit-to-cost ratio exceeding 2:1 over the next decade. The resilient PNT business case has been provided to many maritime administrations across the world to encourage them to consider the optimal contributions to a multi-system receiver.

“Prototype UK eLoran currently operates in co-operation with the other Loran transmitters in France, Norway, Germany and the Faroe Islands, covering the whole North Sea region and beyond,” said Mr Bransby. “Further afield, South Korea is actively implementing eLoran and Russia is collaborating with the UK to develop eChayka, a system that will be interoperable with eLoran and capable of providing resilient PNT for the Arctic shipping route.

“These, along with the Far East Radio Navigation Service (FERNS) Loran service operated by Russia, South Korea, China and Japan, and the low frequency eLoran-compatible technologies currently being developed in the US, indicate that e-Loran will become a foundation block of the future multi-system receiver architecture, providing resilient PNT to the majority of the world’s busiest ports and their approaches.”

GPS spoofing trial

In a demonstration of GPS vulnerability, a research team from the University of Texas was able to change the course of a luxury yacht. The signals from the spoofing device, contained in a box about the size of a briefcase, slowly overpowered the authentic GPS signals until the team effectively gained control of the ship’s navigation system.

The strategy was then to coerce the ship onto a new course using subtle manoeuvres that positioned the yacht a few degrees off its original course. Once a location discrepancy was reported by the ship’s navigation system, the crew initiated a course correction. In reality, each course correction was setting the ship slightly off its course line. The yacht’s electronic chart showed progress along a fixed line, while the ship’s wake showed a pronounced curve showing that the yacht had turned. After several such manoeuvres, the yacht had been tricked onto a parallel track hundreds of metres from its planned route.

Chandra Bhat, director of the Center for Transportation Research at the University of Texas at Austin, believes that the experiment highlights the vulnerability of the maritime sector to such attacks. “The surprising ease with which Todd and his team were able to control a multimillion dollar yacht is evidence that we must invest much more in securing our transportation systems against potential spoofing.”

SRT acquires 3D visual software

Software Radio Technology (SRT) will be developing GeoVS 3D visualisation technology after acquiring the Welsh company for almost £1 million (US$1.5 million) in October. GeoVS has developed PC-based software that enables the real-time 3D visualisation of the marine environment from live data streamed from multiple sensors and information sources. By using the technology and multiple sensors, ship operators will be able to mitigate the effects of the failure or jamming of the global navigation satellite system (GNSS).

The technology converts data from radar and the automatic identification system (AIS) and combines it with multi-layer electronic marine (S57) charts, instantly creating a live 3D model. The user can then move around the marine domain in full 3D to improve their understanding of the area. SRT said it will integrate the GeoVS technology with its own AIS transceivers to produce new electronic display products.

“The GeoVS 3D display technology is impressive in terms of how it transposes real world data, in real-time into a 3D digital virtual reality world,” said chief executive Simon Tucker. “This unique core technology platform, coupled with the expertise of the GeoVS team, enables SRT to develop a series of new system products which will allow us to start to build a significant stream of recurring revenues. I expect to see this increase the value of some existing opportunities for SRT, as well as opening additional opportunities over time.”MEC