The background is a sharp increase in positioning interference in Swedish and nearby waters in recent years, especially in the south-eastern part of the Baltic Sea. GNSS interference takes the form of jamming, where the signal is knocked out, and spoofing, where the vessel is given a position that looks correct but is in fact wrong. The interference is serious because it affects vessels' navigational safety, operational capability and endurance.

– Our aim has been that the Coast Guard's crews are never surprised by GNSS interference and always have a working backup in the form of dead reckoning, gyro and log. We have taken measures so that we can navigate regardless of signal and so be able to carry out our tasks. Everyone must be able to work safely, even in an environment with interference, says Niklas Blume, project manager at the Coast Guard.

Tests and analyses that have been carried out show that GNSS positioning can be affected or lost within seconds during interference. Tests also show that, in some cases, onboard systems can accept a false position without generating a clear warning. An incorrect position can also be passed on to other systems, for example AIS, radar overlay and communication and command systems. This can affect the common operational picture and the ability to make well-founded decisions.

The ability to navigate in disrupted conditions is teamwork

The Coast Guard has carried out a broad review of our navigation capability. It has also mapped the existing equipment and systems on board, with a particular focus on GNSS dependency and sensitivity to interference. At the same time, earlier methods, routines and training have been reviewed, as have working methods in other relevant organisations.

– We have created a robust foundation for all crews, but this is work that needs to be developed continuously. The ability to navigate in disrupted conditions is teamwork. It requires clear division of roles, an active culture of questioning and a common picture of the situation in which uncertainties are also clearly stated. A robust navigation capability that does not depend on GNSS is an important part of the Coast Guard's operational credibility – in peacetime, in the grey zone and during heightened alert, says Niklas Blume.

In the near future, the Coast Guard will launch a new internal training course. It includes simulator-based exercises, which focus on developing both the technical and the human ability to handle interference and uncertainty in the navigation environment.

– The Coast Guard's crews regularly notice GNSS interference. Our advice to others who work at sea is to be aware of the problem and never to rely solely on navigation equipment that is integrated with GNSS, concludes project manager Niklas Blume.

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