Nav Brief - A multi-layered approach

David Patraiko FNI - Director of Projects, The Nautical Institute

We’re all familiar with using radar and ECDIS on their own, and these two systems are often viewed as being separate, independent and employed for separate tasks. Most modern bridge systems, however, have functions allowing navigators to share information between the two devices, often incorporating Multi-Function Displays (MFD) to show different ‘layers’ (overlay/ underlay). If done well, this can improve situational awareness and provide backup checks for critical features. Done poorly, it can also present great risks. Using ECDIS on its own, it is very easy to become over-reliant on GPS/GNSS. If your GPS is inaccurate, you may not realise if your own ship’s position is wrong. Radar, on the other hand, is excellent at identifying information in relation to own ship’s position, but less so at showing how that position relates to navigational hazards below the water. Traditionally, the navigator’s role was to assimilate these views manually, but with the advent of electronic integration these views can now be combined on screen. Managing ‘layers’ from these systems can provide valuable confirmation of GNSS accuracy, Gyro integrity and proximity to navigational hazards both above and below the water. This issue of The Navigator looks at the use of ‘layers’ to support and enhance good decision-making. It explores how a radar image of the coastline can be aligned with the chart image of the same land to check the accuracy of GPS – a very comforting sight when the two line up. We also explore how displaying the outline of a Traffic Separation Scheme (TSS) on a radar image improves situational awareness and how the traditional practice of Parallel Indexing (PI) is still valid and effective. These articles highlight how mismanaging layers can mask critical information or overload the user with information, hampering good decisions. There is no single ‘best solution’ to manage navigation layers. It is up to the navigator to understand the options available, to assess the situation and to choose the information that is most useful in that particular moment. Modern navigation systems also have a variety of options for manually plotting positions and using PI. Practise using them on a regular basis to make sure you have the competency when you need it. Unfortunately there is a wide discrepancy in how systems operate (something The Nautical Institute is working on) so make sure you are familiar with the operation of systems on your own ship to get the maximum benefits. As always, it’s good to discuss these issues with your bridge teams in order to share your knowledge and learn from other. Please learn from this issue of The Navigator, share it with your colleagues and enjoy.