WAYPOINT - It's not just a human problem

01 Oct 2016 The Navigator

Dr Andy Norris, an active Fellow of The Nautical Institute and the Royal Institute of Navigation, explores why humans are not the only source of mistakes – and how to spot technology error.

Humans are not alone in making navigationrelated mistakes. The equipment used on the bridge can also make them, not least when poorly set by the user. Fortunately, humans are in a very good position to check the credibility of displayed information coming from any one source. We should never rely too heavily on data that has not been collaborated. We must always look for consistency in our understanding of the present and evolving situation, using all available information.

Many issues can be automatically detected by the equipment, setting off warnings and alarms. Unfortunately, this is not always the case. Poor user-settings on some systems, such as radar and ECDIS, lead to frequent automatic alerts, which can make operators miss the more important equipment failure alerts. User-chosen alert settings should always be configured properly to meet the current situation without obscuring more important issues.

Continual checks on consistency must be made concerning position. Does my ECDIS-indicated position tie up with all other information, such as radar, visual observations and depth readings? Is my present heading consistent with my indicated track, bearing in mind expected set and drift? Even knowing roughly where the sun should be relative to your own heading is very useful in detecting more extreme error circumstances, not least in ocean waters.

Strength in numbers
We are fortunate in having three totally different ways of detecting targets, all with different strengths and weaknesses, namely sight, radar and AIS. True correlation of all three techniques on all targets of interest is ideal; you are then very sure of the reality of the situation. The correlation of the optical view with the equipment displays is essential in identifying targets of interest undetected by the radar and AIS.

Obviously, in poor visual conditions a much more cautious approach to potential dangers is essential. However, targets that have correlated both radar and AIS returns should incur immensely less suspicion than those with just one. A radar return alone could indicate that the target doesn’t have an AIS signal. However, it could also be the result of a false radar target in that position, maybe from a reflection or a ‘second-time-round’ effect.

If there is just an AIS target showing, is it because a vessel in a totally different position is emitting incorrect AIS signals? Is the radar signature unobservable due to the vessel’s ‘blind angle’, or has it been obscured by clutter?

Always alert
We must also be aware of being over-confident in apparently benign conditions. “The ECDIS shows me to be on track and there’s nothing significant on the radar or from what I can see through the bridge window, so I can relax for a while,” is certainly not a good approach.

Acting with such naivety does not generally result in an accident, which perhaps gives false confidence that it’s acceptable practice. In reality, if your positioning system is in error, the comforting situation of being shown to be on track can be far from the truth. You could be any number of miles off, perhaps with a grounding imminent...

Finally, as emphasised in the last edition of The Navigator, don’t forget the growing possibilities of false information being displayed on navigation equipment through cyber-crime. Fortunately, on vessels being navigated with good error management in mind, such an attack is highly likely to be identified very early on, allowing the vessel to proceed safely.


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