GPS jamming in the Baltic Sea has become a reality for many crews in recent years. The fact that NATO is now systematically testing technology under operational conditions that detects, classifies and locates jammers shows just how seriously the situation is being taken.
What GANDALF 4 can do
GANDALF 4 was developed by specialists at the Joint Intelligence, Surveillance and Reconnaissance Centre of the NATO Communications and Information Agency (NCIA). According to the NCIA, the prototype sensor is designed to detect, classify and locate deliberate attempts to jam or manipulate GNSS signals: both jamming and spoofing.
Previous tests took place in controlled environments, including a measurement campaign in a shielded test chamber at the NATO Support and Procurement Agency (NSPA). This was followed in July 2026 by the first deployment on actual platforms: NCIA experts installed GANDALF 4 on board the border guard vessel ‘Turva’ and an H215 Super Puma helicopter belonging to the Finnish Defence Forces, and tested the system under realistic maritime and airborne conditions. In addition to the NCIA, the Finnish Border Guard and the Finnish Defence Forces were involved. The campaign builds on flight tests carried out in 2025, which were conducted jointly with the Finnish Defence Forces on board an NH90 helicopter. With “Turva” and the H215 Super Puma, the test base was expanded to include further maritime and airborne platforms. According to the NCIA, the data collected confirmed previous findings, enabled the collection of new operational data and allowed system development to continue under representative conditions.
At the same time, the NCIA was testing its CRPA (Controlled Reception Pattern Antenna) technology. This is designed to keep navigation receivers operational even under jamming conditions. According to the NCIA, GANDALF and CRPA complement one another: whilst GANDALF locates sources of interference, CRPA enhances the resilience of the navigation systems themselves.
Jamming and spoofing: two types of interference
In GNSS jamming, a transmitter floods the receiver with strong signals on the satellite frequency. The receiver loses connection to the satellites and the position display cuts out. GPS spoofing is technically more complex: Attackers transmit fake satellite signals that receivers cannot distinguish from genuine ones. The device calculates an incorrect position without the crew initially noticing anything. Our guide describes which backup methods work on board if the chartplotter loses its position: Guide to navigation in the event of GPS interference.
Focus on the Baltic Sea
The Finnish authority Traficom has reported ongoing GNSS disruptions. According to the authority, these disruptions have increased in the spring of 2026. With regard to shipping, Traficom specifically identifies the eastern Gulf of Finland as an affected area. Estonia has also issued a warning. The authorities point out that the disruptions not only affect position readings but may also impact other on-board systems, such as autopilot functions or AIS data.
NATO has not yet announced when GANDALF 4 will be operational or in which areas the system is due to operate in future.
Book recommendations
Astronomical navigation In this book, Bobby Schenk explains how to determine position and course without GPS or electronic aids: using a sextant, a chronometer and celestial data. The book provides precisely the tools needed when jamming or spoofing causes the satellite navigation system to fail and the crew has to fall back on traditional methods.
Stress-free navigation By Duncan Wells, this book covers position fixing using nautical charts, a compass and GPS, as well as by sight, along with route planning, navigational marks and safety at sea. Unlike celestial navigation, the focus is on practical on-board navigation rather than star navigation. A concise introduction to the backup skills required in the event of GPS failures on the Baltic Sea.
Should you put your blind faith in the plotter, or always have a backup method to hand? Share your experiences in the comments.
Hauke Schmidt
Test & Technology editor