The tests took place in Finland from 6 to 9 July 2026. The NATO Communications and Information Agency (NCIA), the Finnish Border Guard and the Finnish Defence Forces were involved. As part of the GANDALF-4 measurement campaign, the equipment was installed on the offshore surveillance vessel ‘Turva’ and on board a Finnish H215 Super Puma helicopter.
The system thus left the controlled laboratory environment. Operating conditions on a ship and in an aircraft yield different measurement data to those from a stationary test bench. For further development, therefore, the focus is not merely on whether the sensor detects a disturbance. It must also determine, as reliably as possible under changing conditions, the nature of the disturbance and the direction or location from which it originates.
What GANDALF-4 is designed to detect
GANDALF stands for ‘Ground-based Asset designed and built by NCIA for Direction and Location Finding’. The experimental system was developed by experts at the NCIA’s JISR Centre. JISR stands for ‘Joint Intelligence, Surveillance and Reconnaissance’, i.e. the joint collection and analysis of intelligence data.
The sensor is designed to counter deliberate interference with signals from global navigation satellite systems (GNSS). This includes jamming and spoofing. In jamming, interference signals override the weak satellite signals, meaning that a receiver can no longer determine its position reliably. Spoofing, on the other hand, involves the transmission of manipulated signals. The navigation system may then calculate an incorrect position without the error being immediately apparent.
GANDALF-4 is designed to detect, classify and locate such sources of interference. For military operations, this is a matter of situational awareness. For shipping, the project also demonstrates how important an independent verification of electronic position data can become. Anyone relying solely on a chart plotter may not notice a distorted position until it has already affected navigation.
They are also important for civilian shipping GNSS interference and spoofing has long since become more than just a theoretical problem. Whilst modern receivers use several satellite systems, such as GPS, Galileo, GLONASS and BeiDou, this increases availability but does not automatically make the signals immune to targeted jamming.
Testing in the laboratory and on platforms
As early as April 2025, the NCIA and the NATO Support and Procurement Agency (NSPA) had tested GANDALF-4 in one of the NSPA’s anechoic chambers. There, the antenna array could be calibrated under controlled conditions and its performance assessed without external radio interference. The focus of this series of tests was on the sensor’s antenna.
The subsequent trials in Finland served a different purpose. The data collected on board the ship and in the helicopter were intended to confirm earlier findings, provide additional operational insights and further refine the technology under realistic conditions. The campaign also built on flight trials carried out in 2025 with an NH90 helicopter belonging to the Finnish Armed Forces.
The Cooperation between the NCIA and the NSPA on sensor testing illustrates the multi-stage path from a technical concept to a near-field demonstrator. There are several development stages between the laboratory, integration, verification and field trials. Only the interplay of these steps reveals whether a system can provide reliable data outside an ideal test environment.
CRPA aims to make navigation more resilient
In parallel with GANDALF-4, the NCIA evaluated a new Controlled Reception Pattern Antenna (CRPA). Such an antenna is designed to support the reception of satellite navigation signals even in the event of jamming. It complements the GANDALF approach: whilst GANDALF is intended to detect and locate jamming, CRPA focuses on the resilience of the navigation system itself.
Both technologies therefore pursue different but complementary objectives. One provides a more accurate picture of the electromagnetic environment. The other is designed to help maintain navigational capability despite interference. This provides NATO and its partners with a technical toolkit that combines detection, classification and countermeasures.
The most recent Trial with Finland At the same time, it highlights why ships and aircraft are important as test platforms. GNSS signals are not used in a controlled laboratory environment, but whilst underway, in flight and in an environment characterised by changing reflections, movements and radio conditions.
BOOTE describes in its article how a GPS fault can manifest itself on board GPS interference: Navigating a motorboat without a chartplotter. Further approaches to satellite-independent positioning are discussed in the article on R-Mode backup system for the Baltic Sea as well as in the report on Radar beacons to counter GPS interference presented.
Book recommendations
Stress-free navigation covers the basics of determining your position using a nautical chart, compass and GPS. The guide also covers dead reckoning, trip planning, navigational marks and safety issues. It is therefore suitable for motorboat skippers who wish to gain a better understanding of electronic navigation and be able to fall back on traditional methods in the event of system failures or implausible position data.
Navigation provides a concise summary of the most important traditional and modern navigation methods. The book covers everything from nautical charts to GPS and is suitable as a brief introduction or as a reference work on board. It serves as a useful practical complement to the article, as it places electronic aids within the broader context of safe navigation.
Astronomical navigation without formulas shows how to determine one’s own position using the sun, moon and stars. Among other things, it explains the sextant, celestial data and the exact time. Particularly in the context of GNSS disruptions, the book makes it clear that, alongside satellite navigation, there are other methods which can be used as a fallback under certain conditions.
Have you experienced any GNSS interference? Please join us for a fact-based discussion in the comments.
Hauke Schmidt
Test & Technology editor