Nav Brief - Dealing with data

David Patraiko FNI - Director of Projects, The Nautical Institute

Throughout history, mariners have been asked to make decisions using data that may not be quite good enough. Although great strides have been made by the industry to improve the quality of information available, it’s still not perfect. Professional navigators must still understand the limitations of data and information (there is a difference!) and how to manage them, particularly in the digital age.

A perfect example is hydrographic data. An ECDIS may look impressive and modern on the bridge, but the data it is presenting is only as good as the last hydrographic survey – which might be very old indeed. Even where data input is accurate and upto- date, the process of interpreting that data and turning it into useful information can be flawed. You might receive very accurate meteorological data (temperature, wind speed, humidity…) at any one point, but the same data can result in different weather forecasts, depending on the methods used.

Always try to obtain the best quality of data and information you can. use reputable sources… assess the risks of potential errors 

Always try to obtain the best quality of data and information you can. Use reputable sources (such as official hydrographic offices), assess the risks of potential errors and find ways of corroborating data accuracy wherever possible. The navigator’s ‘golden rule’ has always been to never trust a position obtained by only one means. Even in the age of integrated navigation systems, it remains good practice to always double or triple check a position, perhaps by using LoPs or overlays (see The Navigator issue 27). Such strategies may even be identified in your SMS and Passage Plan. The articles in this issue illustrate some of the data a navigator must use and how that data might be checked for accuracy. You might well assume that the most reliable source is what you see; however, as any lover of magic will tell you, the eye can be fooled and, more seriously, vision is prone to degradation by bright lights and fog.

Of course, some ships will have far more complex sources of data than those covered within these pages, and more sophisticated ways of displaying and transmitting them to the user. Sheer quantity of information is another challenge that needs to be carefully managed. Just because a system can display target tracking for over 100 vessels at once, that does not mean that doing so is the best choice.

As always in The Navigator, we ask you to think about these issues, do your own research and share your thoughts with others so that we can all make better decisions.