What is Resilience in PNT?

Resilient positioning, navigation and timing (RPNT) is the convergence of traditional positioning, navigation and timing technology with nontraditional and emerging technology to improve the reliability, performance and safety of mission-critical applications. Resilience offers trusted positioning information by protecting, authenticating and offering alternatives to existing PNT sources like GNSS.

What is PNT?

PNT stands for “positioning, navigation and timing.”
Positioning and timing have been the building blocks for navigation since people first took to the oceans. Since the development of the Global Navigation Satellite System (GNSS) in the late 70s, PNT based on satellite signals has become the cornerstone of critical infrastructure, allowing receivers to determine location to high precision using time signals transmitted from space.

What is GNSS?

The Global Navigation Satellite System, or GNSS, is the primary source of PNT information. It is a satellite system that is used to provide location awareness through the geographic location of a user’s receiver anywhere in the world via a constellation of orbiting satellites working in conjunction with a network of ground stations.
The USA’s GPS system is the most widely known form of GNSS but there are others: The Russian Federation’s Global Orbiting Navigation Satellite System (GLONASS), Europe’s Galileo, China’s BeiDou Navigation Satellite System, and the two regional systems India´s NAVIC, which stands for Navigation with Indian Constellation (also known as IRNSS), and Japan’s Quasi-Zenith Satellite System (QZSS).

Does GNSS work indoors?

The signals from the satellites in high orbit are very weak when they reach the earth, so they do not penetrate buildings well. The signals that do penetrate experience multi-path (bouncing off surfaces) so accuracy is degraded.”

What Are the Most Common Threats to GNSS?

Jamming and Spoofing. Jamming happens often, either intentionally or unintentionally since the GNSS signals are so weak. A simple 1 watt jammer can deny GNSS service for many kilometers. Spoofing is the creation of false GNSS satellite signals. While this is more difficult to implement than jamming, all the civilian GNSS signals are open specification, so anyone can duplicate their signals. Spoofing can be more dangerous since it can sometimes go unnoticed where a jamming threat is easier to detect.

Military signals are encrypted and therefore are mush harder to spoof but jamming them is still possible.

Why is Timing Important in PNT?

Determining precise position from satellite signals depends upon accurately measuring the distances between receiver and satellite, which depends on very accurate measurement of a radio signal’s travel time from the satellite to the receiver.

What Operations Rely on PNT?

Critical infrastructures worldwide rely on trustworthy PNT in various operations. These include military and defense systems, maritime transport infrastructure, navigation and shipping, search and rescue applications, emergency services, financial infrastructure, global datacenters, power grids, telecommunications, and many more.

What Technologies Offer Resiliency to GNSS?

There are alternative signals available that add resiliency to GNSS. One that is commercially available is Satellite Time and Location (STL), which offers an encrypted signal 1000 times stronger than GNSS and resists spoofing. STL is available worldwide and operates on the Iridium satellite network. Though not as accurate as GNSS, STL provides 30-50m accuracy that can serve as a check to the GNSS-indicated position. For example, when combined with an Inertial Navigation System (INS), STL can provide valuable range and Doppler updates to the inertial measurements, reducing drift and maintaining accuracy of ships at sea even during extended periods of GNSS denial.

Another alternative signal, where available, is eLoran. ELoran provides a diverse signal for navigation that is literally at the other end of the spectrum from GNSS – low frequency instead of microwave, high-power pulse vs. low power, spread spectrum, and terrestrial vs. space-based. The jammer required to block GNSS is very different from the one required to block eLoran, adding resiliency to navigation.

Is the Threat to Critical Infrastructure Real?

Yes. There are two billion GPS receivers in use around the world, and Europe’s satellite navigation agency estimates this will reach seven billion by 2022. The US Department of Homeland Security has designated 16 sectors of infrastructure as “critical,” and 14 of them depend on GPS. The European GNSS Agency tallied roughly 50,000 incidents of deliberate jamming in the last two years. Jamming was the cause of more than 40 airliners’ loss of GPS when nearing runways at Manila’s Ninoy Aquino International Airport in July and August of 2016.

In the world of finance, spoofing could foul up everything from a convenience store’s credit card reader to the entire New York Stock Exchange. Spoofing by hostile foreign powers is a concern as well. During a 2012 demonstration, Homeland Security officials watched a drone being easily hijacked by being given false GPS coordinates. A major datacenter was recently the victim of unintentional jamming, fouling up its infrastructure for weeks until the culprit was discovered.

June 2017: Spoofing Attack in Black Sea

Nov 2018: Northern Finland Jamming in the Artic Sea

June 2019: Israeli Airports GPS Signal Loss

July 2019: NASA reports passenger aircraft nearly crashes due to GPS disruption

Feb 2020: US President Trump signs an Executive Order directing critical infrastructure operators to address the vulnerabilities of their PNT services to disruption and manipulation

How Does RPNT Protect Against GNSS Discrepancies?

A resilient system typically includes a monitoring component such as Orolia’s interference and spoofing detection solution, which uses proprietary algorithms to monitor GNSS reception, analyze the signals, compare the signal against other reference systems, and alert the user that there is a problem. This solution also provides detailed threat characteristics, real-time situational awareness and recorded data for post event forensic analysis.