When your ECDIS works as an alarm machine.
For many mariners, it is a surprise to discover that the ECDIS produces a high number of unwanted acoustic and visual alarms under specific conditions. The fact that the sound on these alarms cannot be turned off creates a negative working environment and destroys the concentration and focus of navigation officers. In desperation, they sometimes take drastic steps like turning the equipment off or covering the buzzer with plastic tape to minimize the continuous beeping.
This problem occurs under certain, unique conditions. For example, this happens when:
- The ship is entering an area where the ENC chart depth is less than the ship’s safety draft. In such a situation, the ship will need a rising tide in order to pass through the area.
- A ship’s safety draft isslightly deeper than a specific depth curve. This will force the ECDIS to choose the next depth curve as an alarm detection area and generate alarms in many places where there should not be an alarm.
The source of these problems can be traced to mainly one of two causes: the way the depth contours are designed on an ENC map, or the way the ENC safety and display parameters work.
ENCs with a high scale have typical depth contours of 0, 5, 10, 20, 30, and so on. Together with spot depths, the ECDIS uses these contours to create grounding alarms.
On an ENC with contours of 0, 5, 10, 20, 30, and so on, a Safety Contour setting at 11 meters will force the ECDIS to automatically choose the next-higher (i.e. 20 meter) contour. This means that the ECDIS will give an acoustic and visual alarm as soon as the ship guard zone crosses the 20 meter contour. As this type of alarm cannot be switched off, it will continuously beep until the vessel is outside the alarm area. This is not an insignificant problem as there are large navigation areas all over the world that requires more accurate safety contour detection. Actually, an ECDIS using depth contours as alarm levels should have depth contours for each meter, and perhaps for each decimetre in confined waters such as harbours and rivers. This is, in my opinion, a big mistake by the Hydrographic Offices (HOs). They have, in fact, designed the depth curves in an ENC in the same way as the paper chart, without considering the special functionality of the ECDIS to create alarms for depth contours.
A vessel that has such a safety draft or operates in such areas should consider how to avoid these alarms. The alternatives are:
- Switch to harbour mode. In this case, the ECDIS display will be grey and will not show a chart.
- Switch off the ECDIS. This can be an issue, however, as the vessel will not be in compliance with SOLAS chapter V, reg 19.
- Cover the alarm buzzer with tape or another material. In this case, the ECDIS will not meet the alarm requirements.
- Put the system in a non-approval mode and switch off the acoustic alarm. Again, the ECDIS will not be in compliance with SOLAS chapter V, reg 19.
- Plan the route according to the extended alarm area, although this is not possible for many ships. We cannot expect that ships will easily change their excising sailing routes just because they have an ECDIS on board.
- Load ECDIS with charts in raster formats like Admiralty Raster Chart Service (ARCS). Flag and coastal states do not accept the use of the RNC mode in areas where there is ENC coverage.
- Reduce the safety contour and safety depth setting. This, however, can be risky as the system may not give alarm at all.
No doubt, these alternatives are less than ideal. For some vessels, however, there is no way around it; they must choose from among a variety of bad alternatives. It is up to the ship or the company to determine the proper procedure to be used in such conditions. Choosing a reduction in the safety contour and safety depth settings poses an increased risk for grounding without an alarm. This can be dangerous, but it is not necessarily a big risk, as a grounding alarm is not provided using paper charts, a condition with which deck officers are familiar. When a reduction of the safety contour and safety depth settings method is chosen, all navigation officers must be vigilant and fully aware of the conditions.
Another condition that creates a number of unwanted alarms is navigating in channels. In such conditions, the guard zone has a tendency to frequently touch nearby grounding alarm areas and generate alarms.
What makes these problems dangerous is that they appear only under certain conditions. If Hydrographic Offices could create new and better depth contours in the ENC, this would solve the problem. In the short term, though, the best solution is to provide better information, procedures, training, and an inherent understanding of the right decisions in these cases.
One positive development is a change of the alarm sound in the new IEC 61174 ed.4 standard. The ECDIS will now sound alarm beeps three times every 10th second, rather than one long continuous beep, as on previous models. Additional the contour will be the sole anti-grounding (based on depth) source and control crossing alarm will be possible to switch off. The majority of ECDIS devices already installed in ships around the world, of course, but this IEC 61174 ed 4 will be mandatory implemented latest September 2017. Another positive event is introduction of S-102 Bathymetric Surface Product Specification. But, this seems to take some time.
The complexity of this subject is only one of the topics covered at my mobile, type-specific training courses on MARIS, Consilium and ChartWorld eGlobe G2 ECDIS.