Navigation and autonomous systems specialist Advanced Navigation has delivered high-precision positioning without reliance on fixed infrastructure or GNSS, in Europe’s deepest underground mine in Pyhäjärvi, Finland.

The Hybrid Navigation System, combining a Laser Velocity Sensor (LVS) with the Boreas D90 fibre-optic gyroscope (FOG) Inertial Navigation System (INS), achieved consistent sub-0.1% navigation error across multiple runs, without relying on any fixed positioning infrastructure, pre-existing maps, or external aiding.

Navigating the vast subterranean network of the Pyhäsalmi Mine poses significant challenges. Located 1.4 km underground with a 63 degree latitude – just two degrees below the Arctic Circle, where traditional systems fail – the mine is completely impervious to GNSS signals. Its repetitive, multi-level tunnel network creates a high risk of visual disorientation, while its metallic ores distort magnetic fields and scatter radio waves.

To overcome these conditions, mines typically rely on infrastructure-heavy solutions such as ultra-wideband beacons, Wi-Fi, 5G repeaters, or perception-based techniques such as SLAM (Simultaneous Localisation and Mapping) which require cameras. These methods are typically costly to integrate and maintain, slow to install, and often unavailable in hazardous or unmapped zones where reliable navigation is most critical. Shifting to a resilient navigation system, with less dependency infrastructure offers a scalable alternative, enabling reliable navigation even in the most inaccessible or hazardous environments.

The Hybrid Navigation System is centred on Boreas – a FOG INS. Boreas does not rely on GNSS or magnetic compasses. Instead, it uses ultra-sensitive FOG technology to detect the Earth’s rotation and determine true North, a process known as gyrocompassing to find the vehicle’s direction (heading).

To maintain and enhance this accuracy, the INS is fused with Advanced Navigation’s LVS. Using infrared lasers, LVS continuously measures the vehicle’s true 3D velocity relative to the ground. This real-time data is critical for correcting the gradual ‘drift’ that occurs in standalone inertial systems, enabling the Hybrid System to maintain precision over extended distances.

This integration is made possible with Advanced Navigation’s AdNav OS Fusion software. Using adaptive algorithms, it dynamically weighs the reliability of each sensor in real time. Together, these technologies form a resilient Hybrid System delivering accurate uninterrupted navigational data in extreme environments without GNSS or fixed infrastructure.

The Hybrid Navigation System has been validated across five separate runs in complete isolation from external aids or maps, achieving an accuracy of better than 0.1% of distance travelled.

Over a 6 km rough and rugged terrain that extended 400 m below the surface, the system achieved a best-case 3D position error of just 0.55 m (0.009%), with an average error of 2.83 m (0.047%). For context, standard single-band GNSS on the surface typically delivers 2–10 m accuracy in open-sky conditions. This system delivered significantly greater precision even within a subterranean labyrinth.

“Unreliable navigation underground isn’t a minor technical constraint – it’s a major operational bottleneck.” said Joe Vandecar, Senior Product Manager at Advanced Navigation. “Maintaining precision over a 22.9 km subterranean course in Europe’s deepest underground mine demonstrates a level of performance that few systems in the world can rival without any prior intelligence of the environment. These results prove we’re one step closer to unlocking scalable underground autonomy.”