Interference with GPS signals through either jamming or spoofing continues to be an issue in various parts of the world, with hotspots in Eastern Europe, Scandinavia, Russia, and in various conflict zones, including the Middle East. In September, flight operations support provider OpsGroup released its GPS Spoofing Final Report, identifying key issues and work underway to mitigate spoofing problems. 

Spoofing occurs when a GPS/GNSS (global navigation satellite system) receiver is tricked into calculating a false position by equipment transmitting from the ground. This can show the aircraft in a different location than its actual position and prompt the navigation system to send the aircraft off the desired course. Jamming systems attempt to overwhelm relatively weak GPS or GNSS signals and prevent their use by aircraft navigation systems.

According to the OpsGroup report, “The greatest safety concern is the degraded functionality of the ground proximity warning system. The system does not operate correctly after spoofing, even if GPS coverage is restored. The number of false alerts is astounding. There is an increasing normalization of risk. As a result, there was widespread apprehension in the workgroup that the decades-long work to reduce controlled flight into terrain accidents is at great risk of being undone.”

Further, once a GPS/GNSS receiver is spoofed, it could be contaminated with false data, OpsGroup warned. “This places doubt on the use of GPS at any point after spoofing, especially RNP [required navigation performance] approaches and RNP en route use.”

OpsGroup has noted a 500% increase in spoofing in 2024, affecting an average of 1,500 flights per day, up from 300 per day in the first half of the year. A major concern is that flight crew aren’t being provided technical information about “GPS involvement in aircraft systems” and they are receiving “conflicting crew guidance and incomplete or insufficient procedures, all leading to misunderstandings and knowledge gaps.”

In a survey that saw nearly 2,000 responses, OpsGroup reported, “The results show that a full 1,400 crewmembers (about 70%) rated their concern relating to GPS spoofing impact on flight safety as very high or extreme [and] 91% of all crewmembers rated their concern as moderate or higher.”

While OpsGroup acknowledged that there are “no quick and easy solutions…The key focus in the short term is on mitigation, crew awareness, guidance, and training. In the longer term, the workgroup identified potential solutions to hardware, avionics, and system components…Consideration must be given to the potential for a deepening of the GPS vulnerability problem. In mid-2024, we are already seeing a major increase in both spoofing and impact to aircraft. Locations could widen further, and impacts could worsen.”

The group did note that “the over-reliance on GPS for primary navigation places great importance on preserving a sufficient network of conventional ground-based navaids.”

Anti-Spoofing Solutions Available

One solution to GPS jamming and spoofing has be developed by Aerodata, and EASA has issued a supplemental type certificate (STC) for installation of its product in Textron Aviation’s Garmin G5000-equipped Cessna Citation Latitude business jet. 

According to Aerodata, “Based on the alert/information provided by the G5000 suite, the pilot may select the backup GPS source via the new system. The antenna of the new system is mounted on top of the fuselage.”

Aerodata is planning to develop STCs for other aircraft, including civil and military platforms “Aerodata’s solution will enhance its special mission capabilities, especially in intelligence, surveillance, and reconnaissance missions and flight inspection, where continuous, highly accurate navigation is mission-critical.”

“As incidents of GPS interference rise, it is essential that the aviation industry responds with effective solutions to ensure continuous GPS availability,” said Aerodata president and CEO Neset Tükenmez. “This STC represents a significant advancement in ensuring the future safety in civil and military aviation.”

SandboxAQ is tapping quantum computing to mitigate GPS interference, using measurements of Earth’s magnetic field with a vector magnetometer to detect anomalies due to jamming and spoofing.

“The earth’s magnetic field is unique in different places,” explained Luca Ferrara, general manager of navigation for SandboxAQ. “The magnetic field has more information than just the compass heading,” he added, “with anomalies that add or detract from the field, like a fingerprint. This gives us a reference data stream based on magnetism. When we have the right sensing technology, we can see that signal and navigate off it.”

Sandbox AQ’s AQNav does comparison mapping against the magnetic gradient that it is able to detect. “If I’m able to take measurements that allow me to see this changing gradient, I have more information that I can use to determine my position,” Ferrara said.

The baseline magnetic data comes from databases such as one maintained by the U.S. National Oceanic and Atmospheric Administration. What makes AQNav able to detect the magnetic gradient is a quantum-based magnetic sensor.  

“It’s very sensitive,” he said, but it also measures outputs that aren’t needed to provide a navigation solution. “All aircraft emit electromagnetic interference. The technology challenge is how to generate a value that I can use for a matching technique. We use hardware and software to generate the best possible signal such that we can use it intelligently with another layer of algorithms tuned for the particularities of map-based matching with magnetic fields.”

In practical terms, AQNav “produces a position estimate, by comparing the best estimate of the magnetic field with an existing database paired with an inertial navigation dead reckoning system to constrain uncertainties.”

Ferrara compares AQNav with a lost hiker finding their position using an altimeter and a topographic map. By going to each mountain top nearby and taking an altitude reading, the hiker can match the peak to the map. Dead reckoning in the air works if you know the starting position, but it doesn’t continue working unless you can take measurements to update the position. “If you have a topographic map equivalent, that opens your ability to do more with that data,” he said.

So far, the U.S. Air Force has tested AQNav, which fits into a package about the size of a suitcase that can be easily rolled on and off an aircraft. “The sensor is not large,” Ferrara said. A system designed with modular architecture could place smaller distributed sensors around the aircraft. Or a portable system could fit into a pod. 

Ferrara expects to develop a system for commercial aircraft that complements existing avionics. “It’s not about positional accuracy,” he said, “but about how that position is being calculated. It can’t be spoofed or jammed and it works in all weather conditions and over the ocean. When added to that mix of systems, it adds value because it’s different.”

SandboxAQ has been working with commercial partners to explore use cases for AQNav, including what levels of accuracy would be useful and how the system would integrate with the aircraft’s avionics. “We’re going to engage with the FAA to make sure it’s well understood,” Ferrara said. “We’re already open to working with commercial groups to develop it in lockstep and we think it’s only a few years away.”