Q-CTRL has demonstrated GPS-free navigation of a maritime vessel using a quantum gravimeter during trials in the Coral Sea off the east coast of Australia.
The system achieved positioning accuracy of one nautical mile over the duration of the mission, which the company says is more than 10 times better than navigation-grade GNSS backup systems.
The technology, developed as a maritime variant of Q-CTRL’s Ironstone Opal navigation system, uses quantum sensing to measure variations in the Earth’s gravity and match them against gravity maps to determine a vessel’s position.
Unlike GNSS, the system does not transmit or receive external radio signals and is therefore not affected by jamming or spoofing.
Q-CTRL said the gravimetric navigation system can provide corrections to an inertial navigation system without requiring periodic sensor recalibration or specialised installation infrastructure.
The system was installed in a passenger cabin during the trials and operated autonomously in heavy seas.
Its quantum sensor is stabilised using Q-CTRL software, allowing it to operate without temperature control or gyroscopic motion stabilisation.
The maritime system builds on Q-CTRL’s MagNav technology, which uses magnetic field measurements for GPS-free navigation and was demonstrated in ground and airborne trials in 2025.
Gravity-based navigation is particularly suited to maritime applications because gravity maps are more widely available over the oceans, according to Q-CTRL.
“The presence of malicious interference to GNSS signals via jamming and spoofing attacks means that we need reliable alternatives that cannot be manipulated by external sources,” said Jason Ralph, Professor of Electrical Engineering and Electronics at the University of Liverpool.
“Whilst there are a number of ‘Alt-Nav’ technologies that can help to provide resilience, they all have limitations and their own vulnerabilities. Gravity sensing and map matching is the only passive Alt-Nav technology that is global in extent and is impossible to jam or to spoof.”
“Q-CTRL’s recent work to develop and demonstrate a compact and high precision gravity sensor suitable for navigation applications has the potential to be a game changer for reliable alternatives to GNSS positioning.”
