Using radar to confront the challenges facing autonomous vessels in GNSS-limited environments

Often, vessels use onboard sensors to cope where GNSS cannot. The most commonly used sensors are cameras and lidar. These have been successful in land-based autonomy projects, and can provide rich data concerning a maritime vessel’s environment. However, cameras perform poorly in unfavourable weather or lighting conditions, whilst lidar lacks the range required for marine autonomy.

Clearly, the maritime sector needs a single-sensor approach that can accurately provide positional information, whilst enduring tough conditions and environments.

Navtech Radar has recently developed an approach to autonomous navigation that uses W-band radar. Unlike conventional X-band marine radars (8–12GHz), Navtech sensors use signals in the microwave frequency (76–77GHz). This creates a much clearer picture of the local environment.

Terran360 uses radar data to build up a map of a particular route, and on subsequent runs, radar data is used to localise a vessel’s position within this route, providing centimetre-level precision.

This approach to localisation distinguishes itself from alternative solutions that use GNSS, lidar and cameras in the following ways:

• Range: Navtech’s radars have a range of up to 500 m.
• Environmentally robust: radar-based localisers are unaffected by changes in weather or lighting.
• GNSS-free: radar-based localisation continues to work in GNSS-denied environments, such as ports or inland waterways. There is also no risk of interference.
• Precision: The system can assess vessel position with centimetre-level accuracy.

Radar’s advantage as a sensor is most pronounced in harsh environments. Thus, it makes sense to apply Terran360 to the maritime industry, where conditions are generally harsh and unpredictable. Radar-based localisation is a lesser-known approach that now, with changing demands, shows great potential. It is accurate and robust, and overcomes the problems arising from GPS and alternative sensor solutions.