WAYPOINT - Looking ahead

01 Jun 2021 The Navigator

Dr Andy Norris, an active Fellow of The Nautical Institute and the Royal Institute of Navigation, highlights the advantages of electronic intelligence in navigational layering and data display, both now and into the future

The concept of navigational layers has been incorporated into ships’ bridge display equipment for many years. IMO’s first performance standards for ECDIS, adopted in 1995, covered layers in a section entitled “Display of Other Navigational information”. It particularly highlighted the allowable overlay of radar data, provided the displayed ENC data remained visible.

Since then, there has been a steady increase in the electronic intelligence that can be incorporated into the layering, integration and display of navigational information to give navigators a better understanding of the situation around them. In 2007, IMO published its first Integrated Navigation System (INS) performance standards. This provided the base standards for such systems and has only needed minor revisions since then.

These standards have allowed everdeveloping technology to steadily improve the presentation of the whole situation and to give better indications and/or warnings of discrepancies.

Inertial sensors
The variety of data that can be collected and sensibly displayed to improve the safety of navigation is increasing. Of great significance, inertial sensors are, at last, becoming affordable. These continuously measure the sensed movement of the vessel. Input from inertial sensors is used with knowledge from other systems of the vessel’s position, bearing and speed at a given moment to provide automatic ‘Dead Reckoning,’ generating an estimate of the current position from the last known position.

The immense advantage of these sensors is that their basic measurements are unjammable and unspoofable. This means that a continuous overlay of the calculated position from such sensors onto an integrated display can give an excellent indication that normal positioning information, such as from GNSS, is becoming inaccurate. They continuously estimate the current position based on the best positional information available from other systems at ‘n’ minutes before. ‘n’, for example, could be ten minutes – depending on the actual accuracy of the fitted inertial sensor.

They not only provide a warning when a vessel’s normal positional system is being compromised but also give a continued estimate of position – very important in such a situation. This is effectively based on the last uncompromised position, albeit with ever-decreasing accuracy. Military submarines have used inertial systems for many years, allowing long periods of totally underwater manoeuvring – but, in the past, at great expense.

Optical technology
Evolving optical technology can also provide overlays that make it much easier to correlate features from the current optical scene with the data on an INS display. A hand-held ePelorus, for example, instantly communicates the bearings of human-selected sights as an overlay on an integrated display.

Two or three sights on well-chosen charted and visual objects allow an independent position fix to be generated. These sensors make it so fast and easy to overlay visual bearings on the chart or radar display that it is possible to use regular, sensibly chosen single bearings to effectively maintain an independent check on the accuracy of the displayed scene. In reality today, the actual use of ePelorus remains low, despite their obvious and immense advantages.

The evolution of technology into the future will provide ever-greater insight into the current situation and the way it is depicted – and also highlight when there is any conflicting information. The active involvement of navigators in understanding the full scene is not at all diminished. Instead, these new developments allow navigators to give complete concentration to fully understanding the evolving situation, allowing the early detection and mitigation of potential problems.


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