GPS threats are increasing at a record rate.
Escalating conflicts around the world are undermining GPS reliability as a surge of interference attacks continues to impact vast areas of Europe and the Middle East, causing significant disruptions for civilians. At the same time, more criminals increasingly use jammers for drug trafficking, cargo truck thefts and other criminal operations in North America. Sporadic GPS jamming and spoofing incidents have disrupted key American airports in recent years. Even everyday American citizens are now purchasing low-cost retail jammers as privacy fears and anti-government conspiracy theories spread.
Security analysts have spent years warning about the potential for targeted attacks on GPS that could disrupt the financial system, power grid, air traffic systems and emergency services. However, while there are growing calls to develop backup capabilities for GPS, there is another critical issue that must also be addressed.
America urgently needs an automated national detection system that can pinpoint GPS interference the moment it occurs and provide accurate real-time maps of where the impact is actually occurring.
The lack of a coordinated real-time, high-precision jamming and spoofing detection system is a critical shortcoming in our satnav capabilities that leaves American government, commercial and emergency operations vulnerable within their own borders.
The current situation
Current detection methods and outage maps are inadequate, as they rely on limited data collection and outdated systems, leaving huge coverage gaps that make it difficult to achieve an effective response.
Today, GPS outages are mainly detected through a hodge-podge of high-altitude platforms for broad area coverage, like Automatic Dependent Surveillance-Broadcast (ADS-B) — typically at 30,000 feet or higher — and satellite systems, as well as ground-based sensors targeted to a few specific locations like busy airports and military bases. Both of these have important limitations. Aviation-based sensors have more difficulty detecting jamming and spoofing that targets terrestrial assets or low-altitude drones. For instance, we know from firsthand accounts there is Chinese jamming around Taiwan and the Taiwan Strait. This jamming often doesn’t show up on outage apps which rely on ADS-B because China uses low angle directed jammers and terrain shielding to prevent detection from these systems. Meanwhile, ground-based sensors have a limited overall range, so their limited deployment means they cannot provide extensive geographic coverage. This results in a very incomplete picture of what’s happening.
Outage maps
The proof is in current global navigation satellite system (GNSS) outage maps. While several valiant efforts are underway to track interference incidents, these maps are limited by the insufficient data they receive.
As a result, they do not provide highly precise, real-time location data for acts of GPS interference, nor do they determine the intensity — or power — of the jamming or spoofing, nor do they track how this intensity varies across physical distance, by altitude and by topographical features such as hills, mountains, trees and buildings. Additionally, their effectiveness is limited to the immediate areas around airports and flight paths.
The net effect is that most interference maps have significant coverage gaps in certain geographical locations. These maps are useful at providing an overall sense of where GNSS interference is broadly occurring, but they are not precise or complete enough to be relied on by the military, civilian aircraft, maritime vessels or medevac services that would need precise location data to coordinate their responses.
Are smartphones the solution?
The National Space-based PNT Advisory Board has been actively encouraging the development of a national detection and reporting system for satnav interference. One of its key recommendations is to base such a system on mobile wireless technology.
Years of research have backed crowdsourced smartphone detection of GPS/GNSS interference. With more than 300 million smartphone users in the United States, these powerful mobile computer platforms represent one of the most potent distributed sensor networks on the planet.
Sophisticated algorithms that combine data from many smartphones in an area can identify signal anomalies that indicate the presence of jamming and spoofing. Further spatial analysis of raw GNSS signals from a network of smartphones can be used to localize the source of attacks. By leveraging indicators in real time, smartphone-based networks could provide timely alerts on potential jamming or spoofing threats which will enhance protection for civilian navigation, critical infrastructure and timing applications from disruption.
The vast distributed nature of these networks could also address two other fundamental challenges in interference detection: pinpointing emitters and determining the area of effect.
Tracking emitters
Geolocating the actual source of an interference attack — the emitter — is critical for launching fast and effective countermeasures, such as disabling the jammer to restore navigation service.
Finding the emitter also helps reveal exactly where the interference is occurring, where it is likely to have the greatest effect and which assets are most at risk.
However, emitters are often difficult to accurately locate using conventional ground-based sensors. One basic challenge is that jammers often utilize low-power signals that are more difficult to detect from a distance and may reflect off of buildings, cars and trees. Mobile jammers also change locations frequently, making them harder to track. Sophisticated jammers also use detection countermeasures, such as omnidirectional antennas and frequency hopping, which make triangulation difficult.
A smartphone-based detection system would vastly increase the number of sensors tracking down the emitter. A dense grid of detection points will be able to more quickly and accurately detect, confirm and centralize information on signal location in real time — even if the emitter changes locations. We’ve already seen that large networks of mobile devices can provide real-time monitoring of the ionosphere to improve positioning accuracy.
Areas of effect
Current detection methods face a similar challenge in determining the area of effect of GPS interference.
The signal strength and overall effectiveness of interference attacks can vary widely across regions because of geographical distance, natural topographical features such as hills and forests, urban density and environmental factors. As a result, an attack’s actual impact may be substantially different in one area than it is for another, even within a relatively close distance. A blended network of high altitude and ad hoc terrestrial sensors provides a more diverse set of inputs to best accomplish the goal.
Another important factor is altitude. In our own field testing with Ukraine’s military innovation unit, we’ve found significant differences in the power and effectiveness of jamming signals by altitude. “Clear sky” objects, such as planes, are more likely to suffer the full effect of the jamming attack, whereas other vehicles, like low-flying drones and cars, may experience less of an effect.
Accurately determining the area of effect is essential for providing real-time, actionable alerts to satnav users in those areas.
Here too, smartphones can play an important role. A distributed network of mobile sensors can improve both the accuracy and speed of determining the distributed effect of jamming and spoofing signals by measuring the impact on each device and comparing that to its location data.
Where to go from here
The Defense Department, Department of Homeland Security, Federal Aviation Authority and other agencies are all working on new efforts to improve GPS interference detection. These initiatives utilize a variety of technologies, including commercial satellites and artificial intelligence.
Mobile phones should play a critical role in these detection efforts, as they make it easy to disperse many sensors over wide areas, significantly improve redundancy and are cheaper to implement than most other solutions.
What is ultimately needed is a more unified approach that integrates all of these core technologies into a single advanced system for real-time detection. For instance, in our own work, we are currently testing new capabilities for smartphone-based detection and emitter localization. A multi-layer system — combining detection data from satellites, ground-based units, mobile phones and aviation platforms — will provide the most robust capability for instantly identifying GNSS anomalies and tracking their effect. The establishment of a mobile phone detection system is particularly important, as this would allow for an inexpensive early-warning tip and cue system, where phone sensors provide initial alerts of attacks that satellites other systems then confirm.
Establishing a dense grid of detection points is the best path forward for improving our defenses and enabling a faster response.
Sean Gorman is the CEO and co-founder of Zephr.xyz, a developer of next-gen location-based solutions. Gorman has a more than 20-year background as a researcher, entrepreneur, academic and subject matter expert in the field of geospatial data science and its national security implications. He is the former engineering manager for Snap’s Map team, former Chief Strategist for ESRI’s DC Development Center, founder of Pixel8earth, GeoIQ and Timbr.io, and held other senior positions at Maxar and iXOL. Gorman served as a subject matter expert for the DHS Critical Infrastructure Task Force and Homeland Security Advisory Council, and he’s been awarded eight patents. He is also a former research professor at George Mason University.
