WAYPOINT - The digital data revolution

George Shaw AFNI from the Royal Institute of Navigation explains how digital maritime services are evolving to address higher demands on mariners’ situational awareness

Globally, restricted areas (RAs) are growing rapidly in number, size and diversity of purpose. This means that vessels are being squeezed into more confined navigable spaces. For example, offshore renewable energy installations, with turbines located to maximise wind capture, may spread over hundreds of square nautical miles at considerable inconvenience to shipping. Vessels may now need to negotiate several banks of closely spaced turbines that are either formally designated RAs or simply not safely navigable by large vessels with limited manoeuvrability.

An increase in RAs could force more vessel routes to converge, conflict or introduce dog-leg manoeuvres that deviate unexpectedly from the natural course. The increased density of shipping around the boundaries of RAs raises encounter rates, so that vessels come into close proximity more often. Mariners have to remain alert for possible collision avoidance actions and maintain situational awareness under rapidly changing conditions. They must gather information from multiple onboard systems, supported by intensive visual lookout.

Digital evolution

Digital maritime services are evolving to address the increased demands on mariners’ situational awareness and monitoring of encounters. The IHO has standardised its S100 digital charting products, which now indicate RA boundaries and local speed restrictions (eg S-122 data for Marine Protected Areas and S-130 polygonal demarcation). Another helpful tool is the S-421 Route Plan Exchange Format, which allows nearby vessels to declare their routes and intended manoeuvres

The upgrade from AIS to VDES allows for increased communication bandwidth and data authentication, enabling robust services and countering AIS data spoofing. This data revolution should enable clear ECDIS portrayal of high density traffic around RA boundaries, and give early safety indications when possible collision avoidance situations develop. Data services like these could eventually be extended to safe navigation around dynamically varying RAs, such as for seasonal protection of migrating mammals.

Data quality

Resilient digital services must adapt to the quality of underlying data, for example estimated accuracy of chart surveys and uncertainties in sensor measurements. Ideally, the information displayed should indicate where there are potential errors in derived data, such as circular error probable for position, or uncertainty in minimum passing distance (CPA). If digital information is displayed without error bounds it may seem convincing, but it can become hazardously misleading. Safety alarms should be triggered when estimated error is greater than a certain set limit, while maintaining low false alarm rates. Mariners must remain aware of the fundamental qualities of the data they are using and gradually become familiar with the likely error estimation.

Position data derived from GNSS remains a key input to multiple maritime services, although it may not be immediately evident when it is in use, such as in AIS reporting of vessel locations. For maritime users, GNSS positioning suffers integrity limitations, as can be seen near current conflict zones with some large errors in reported ship locations. GNSS accuracy can be degraded or denied by natural or intentional interference. Determining reliable error for GNSS positions is technically challenging, so mariners should always consider the risk of hazardous GNSS errors being transferred to derived information – including the AIS-derived CPA. Radar remains the principal sensor supporting collision avoidance decisions.