Detecting and Defeating GPS Jamming

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Published Feb 16, 2018 5:54 PM by Sean McCrystal

Positioning and timing have been the foundation blocks for navigation since man first took to the oceans. Since the development of the Global Navigation Satellite System (GNSS) in the late 1970s, position, navigation and timing (PNT) based on satellite input has been vital to many critical systems on board vessels, allowing receivers to determine location to a high-degree of precision (within a few meters) using time signals transmitted from space. The maritime industry relies on trustworthy PNT in transport infrastructure, navigation, communications, search and rescue applications, fishing operations, regulation and recreational boating.

As an example of its significance, UK Government research in 2017 identified that a five-day loss of GNSS would cost the UK maritime economy over a billion pounds, highlighting the fundamental value of the signal in core marine operations, and the growing realisation that GNSS as a source of PNT needs to be both protected and irrefutable. This realisation of the importance of GNSS has led to the birth of what is now known as Resilient PNT.

GNSS are the primary PNT reference sources, but their signals are very weak when they arrive to earth. They have well-known vulnerabilities and limitations that require protection and mitigation. They can be disrupted by unintentional interference and the unencrypted signal in civilian use is susceptible to attack.

Intentional interference can be the denial of access to satellite signals or jamming, so your vessel can’t determine its exact location. Spoofing, also known as advanced jamming, is the creation of additional signals that provide misleading PNT information, so the vessel’s position or time reference is no longer accurate.

Resilient PNT is the convergence of traditional positioning, navigation and timing technology with non-traditional and emerging technology to improve the reliability, performance and safety of mission-critical applications, where discrepancy in data accuracy, availability and stability can impact the safety, security and economic viability of vessels at sea. Resilience offers vessels position and time information it can trust, by protecting, authenticating and offering alternatives to existing PNT sources, such as GNSS.

The operational impact of resilience is the ability to detect vulnerabilities in GNSS, such as spoofing or jamming incidents, issue alerts to the vessel and provide alternative sources of navigation and positioning.

Alternative navigation signals such as Satellite Time and Location (STL), offer an encrypted signal, 1000 times stronger than GNSS that resists jamming and spoofing. STL is available worldwide, operating on the Iridium satellites. Though not as accurate as GNSS, it provides 30-50 meter accuracy which can serve as a check to the GNSS indicated position or time. When combined with an Inertial Navigation System (INS), it can provide valuable range and Doppler updates to the inertial measurements, reducing drift and maintaining a proper navigation solution, even during extended periods of GNSS denial.

Navigation Protection Devices are an emerging product category that addresses the concerns about trust in the navigation information being provided. A Navigation Protection Device typically includes a monitoring component, such as Orolia’s NPD BroadShield, which monitors GNSS receptions, analyses the signals and alerts the pilot on the bridge. This Navigation Protection Device (NPD) is independent of the vessel’s navigation system and interfaces with the ECDIS display, if one is available, to give real time indication of alerts and positional discrepancies. However BroadShield can also send alarms or warnings in other forms for vessels not equipped with an ECDIS.

Similarly, eLoran, where available, provides another diverse alternative signal for Navigation Protection Devices. It is literally at the other end of the spectrum from GNSS – low frequency instead of microwave; high-power pulse instead of low power spread spectrum; and terrestrial instead of space-based. The jammer required to block GNSS is very different from one designed to block eLoran, adding resiliency to navigation.

Three typical detection scenarios exist that would indicate there is a problem: the NPD activates on the presence of additional signals in the GNSS band or anomalous behaviour of the signal; it determines its navigation solution does not match the ship’s GNSS guidance solution due to equipment malfunction or malicious signals; or it identifies that the navigation solution differs from the GNSS constellations and its alternatives sources, such as STL or eLoran.

There is a growing realisation of the risks of unsecured maritime PNT. Recent examples of attacks on vessel positioning and navigation systems include the widely known Black Sea spoofing of GNSS/AIS reported positions in 2016, concerns surrounding high profile Navy collisions and jamming of fishing vessels attributed to North Korea.

PNT resilience becomes even more significant when you consider the exponential growth of maritime connectivity, living in an always-connected world and the need to share sensitive data. Global shipping is leveraging the value of Big Data, so as maritime connectivity quality increases with the adoption of VSAT (estimated to be installed in 6500 vessels by 2026 – according to SES Networks) and the growth of satellite coverage, fleet owners are better able to integrate global fleets with onshore operation and are under growing pressure to adopt these solutions or face losing their competitive edge.

Satellite Time and Location or STL offers an additional signal authentication tool through geo-location. STL’s encrypted signal means the vessel has an irrefutable PNT source, which in turn can authenticate communication or network access, as you can trust the vessel was in a certain location at a certain time and that communications to and from the vessel are genuine. This offers huge scope in cyber security, protection network access and the big data solutions that are rapidly changing the capabilities of the maritime industry. PNT is the foundation of trusted maritime navigation and with the latest technological advancements adding resilience, safer shipping can extend trust to cyber security and secure communication too.

There is now a growing awareness of the vulnerabilities of GNSS but what is not yet clear is what to do about them. There is no silver bullet – no one solution that can overcome the problems – but we believe a combination of several alternative methods can augment GNSS and provide the resilience necessary for all critical operations.

Sean McCrystal is senior maritime marketing manager at Orolia

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.