Engineering news
Most commercial drones rely on global navigation satellite systems (GNSS), the family of services that includes the US-owned GPS, Europe’s Galileo and China’s BeiDou. GNSS tells an aircraft where it is, helps it follow waypoints and provides the position needed for safety features such as ‘return to home’.
But those signals weaken when they are beamed back down to Earth, and they can be spoofed or removed entirely by malicious actors. So far, that has mostly been limited to the military realm, but Russian interference in everyday life has the Civil Aviation Authority spooked. Its safety notice on GNSS radio frequency interference says incidents have increased since 2022 and have been encountered in UK airspace. Issues have included incorrect drone positioning, wayward route deviations and the loss of satellite-based navigation functions.
The issue is a particular problem for drones precisely because they are uncrewed. The same interference is happening to crewed aircraft, but they can rely on fallbacks in a way drones cannot.
Fixing that issue is an engineering problem the industry is trying to solve. Manuel Del Castillo, vice-president of business development at positioning technology specialist FocalPoint, says aircraft can monitor GNSS integrity by comparing signals from different satellites and frequency bands, checking them against independent inertial sensors, then rejecting movements that would require physically impossible speeds or vertical acceleration.
“In any of these cases, GNSS is ‘deweighted’ within the mix of positioning sources used,” he says. “The key is avoiding a ‘confident but wrong’ position by ensuring the navigation system can reliably determine when GNSS can and cannot be trusted.”
It is vital to deweight GNSS because quickly switching navigation sources could create a dangerous jump in the drone’s estimated position. Modern systems instead use sensor fusion, continuously combining several imperfect measurements and changing how much they trust each one.
An easy hardware-based fallback is to deploy an inertial measurement unit containing accelerometers and gyroscopes that measure movement and rotation. Because it relies on onboard sensors, inertial navigation cannot be jammed and can continue calculating movement from the drone’s last trusted position.
Inertial navigation is not perfect, however, as it drifts over time. Tiny sensor errors are repeatedly added to the position estimate, meaning the aircraft becomes progressively less certain of where it is. Better sensors reduce that drift, but tend to be heavier and more expensive – and, given drones are designed to keep weight down and battery life up, smarter tech can be more expensive.
Another solution is to use cameras, which can track distinctive points in successive images – such as a building corner or road marking – to calculate how a drone has moved. When combined with inertial sensing, this technique can go a long way to replacing GNSS.
The CAA’s July 2026 concept for future drone operations already envisages inertial navigation and visual odometry maintaining aircraft positions when GNSS degrades. But vision is far from perfect; when darkness falls or a drone goes over a featureless stretch of land or sea, it loses its waypoints. Radar or lidar can bridge that information gap, but those technologies also cost money and add weight.
The answer to GPS or GNSS failure is strength in numbers. Multiple satellite constellations and frequencies improve the chance of retaining a legitimate signal, while inertial sensors can withstand short outages and visual, radar or lidar odometry can track when there are visible signs.
New solutions are important not just because of subterfuge, but also shifting geopolitical partnerships. Most UK industries remain dependent on satellite-based positioning, navigation and timing (PNT), according to a 2025 government statement. Operated by the US government, there could be fears of GPS being switched off for previous allies depending on current government policy.
The US says GPS has never been switched off since becoming operational and that it has no intention of restoring Selective Availability, the deliberate degradation of civilian GPS signals abandoned in 2000. But engineering a resilient system has to be based around consequences rather than assurances. Whether an outage is caused by a jammer beside an airport, a counter-drone system, atmospheric interference or a decision in Washington, the consequences would be the same. Drone operators need to be ready.
Want the best engineering stories delivered straight to your inbox? The Professional Engineering newsletter gives you vital updates on the most cutting-edge engineering and exciting new job opportunities. To sign up, click here.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.