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Modern ships depend heavily on satellite navigation, creating a vulnerability when GPS and other GNSS signals are jammed, spoofed or unavailable. In a contested maritime environment, losing those signals can make it harder for vessels to determine their position precisely, increasing interest in navigation methods that do not depend on transmissions from space.
Quantum technology company Q-CTRL has demonstrated one such approach during maritime trials in the Coral Sea. Its GravNav system uses quantum sensing and maps of Earth’s gravitational field to estimate a vessel’s location without receiving GPS signals or requiring external navigation infrastructure.
The principle relies on the fact that Earth’s gravitational field is not perfectly uniform. Differences in geology and other factors create small, measurable variations from one location to another. The system measures those variations and compares them with an existing gravity map, allowing the system to estimate where the vessel is located.
Because the technique is passive, it does not need to exchange radio signals with satellites or other external transmitters. According to Interesting Engineering, that makes it fundamentally different from GNSS and removes the possibility of directly spoofing the navigation system by broadcasting a counterfeit GPS signal.
Making such measurements aboard a moving ship is difficult, however. Quantum sensors are highly sensitive, meaning vibrations, temperature changes and vessel motion can interfere with the tiny physical signals they are trying to measure.
The company addresses that problem with AI-powered control software that stabilizes the quantum sensor and filters environmental disturbances. According to the company, the system operated without specialized temperature control or gyroscopic motion stabilization.
During the demonstration, the equipment was installed inside the ship’s passenger cabin rather than in a specially prepared location. It operated autonomously while the vessel was underway.
The company reported positioning accuracy of approximately 1.6 km and said the trial delivered a tenfold performance improvement relative to the navigation benchmark used for the demonstration. The result represents a field demonstration rather than evidence that quantum navigation is generally ten times more accurate than standard GNSS under normal conditions.
The technology has clear defense implications. Warships, autonomous vessels and logistics fleets may need to navigate through areas where satellite signals are deliberately disrupted. A passive system based on local gravity measurements could provide another positioning source alongside inertial navigation and other GPS-independent technologies.
The company previously demonstrated a related system called MagNav, which determines location by measuring variations in Earth’s magnetic field. The other system uses gravity instead, for which suitable maps are more widely available and potentially better suited to maritime applications.
The trial does not mean quantum navigation is ready to replace GPS. Size, cost, long-term accuracy and integration aboard operational vessels will still determine its practical value. But it demonstrates a different way to navigate when satellites cannot be trusted: rather than looking toward space for position, a vessel can measure the Earth beneath it.
