The Art of Dredging

Dredging and shipping

ECDIS UPDATE  March 2010


In 2016, all ships will be mandatory outfitted with ECDIS, sending paper charts to the museum.

ECDIS is coming of age, not without growing pains:

1.  IHO Circular letter: isolated shoals not displayed on ECDIS. 

2. ...and more troubles ahead ...



IHO Circular letter - isolated shoals not displayed on ECDIS


The International Hydrographic Organization has issued a Circular Letter on Feb. 24th 2010, warning that -in some cases- isolated shoals may not be displayed on ECDIS.

 IHO Circular letter (download)


The problem has been noticed due to some producer states of Electronic Navigation Charts (ENCs) misinterpreting some of the encoding rules for isolated shoal depths.

The result is that ECDIS may not display some isolated shoal depths when operating in "base or standard display" mode and route planning and monitoring alarms for these shoal depths may not always be activated, pending operator settings.

The IHO is taking steps with its members to achieve corrective action on the ENCs which are affected.

Meanwhile a navigation warning is being broadcast on SafetyNET and NAVTEX advising mariners to confirm that a planned route is clear of such dangers by visually inspecting the planned route and any deviations from it using ECDIS configured to display "all data". The automated voyage planning check function should not be solely relied upon. 


...and more troubles...



Knowing where you are going requires a map.

But if that map is out of date, you could get lost. Not such a problem if it results in a longer car trip. However, if we talk ships, the consequences could be far more dramatic. And it would seem that the incidence of incorrect charts is on the rise.
Port State Control data reveals that 7% of all ships were detained for inadequate nautical publications, up from 3%.

The dangers of using out of date nautical charts have been brought home by a protection and indemnity club. The London P&I Club raised the issue in its January StopLoss Bulletin. One incident cited by the club involved a ship hitting a hazardous wreck that had not been recorded by the chart in use. The club’s investigator found that a chart correction showing the wreck had been issued three years previously.

In another incident, a submarine cable was damaged by a ship’s anchor. In this case, it was assumed the anchor had been dragged along the sea floor before coming into contact with the cable. In fact, the ship, unaware of its existence as it had been using an old edition of the chart, had dropped anchor directly above it. Apparently, the second officer had not checked whether or not he had the chart’s most recent edition.



But the problem of inaccurate charts does not stop at the ship’s bridge or with the seafarer tasked to make sure the charts onboard are up to date.

Concerns have been raised from other quarters in the maritime industry over the quality of the data upon which the charts are based.

While it is possible the chart onboard a ship is out of date through not being updated, it is also conceivable that the original data fed into the chart is inaccurate. A case in point involved the jack up barge Octopus .

A 2007 report by the Marine Accident Investigation Bureau into this incident, which took place off the Scottish coast, found that the cause of the accident was attributable to out-of-date charts. The barge "Octopus" was under towed by a tug. Due to strong tidal streams, the vessels changed course to a route unusual for deep draught vessels. The jack up barge was subsequently grounded on an uncharted sandbank.

According to the area’s applicable Admiralty chart, the draught should have been above 20 m. But the barge, with legs extended to 13m, found itself stuck on the sandbank which had a depth of 7.1m. The source data for the map was found to be over 150 years old.

Responsibility for chart surveys in UK waters lies with the Maritime Coast Guard Agency (MCA).

The MCA has a£5.5m (US$ 8.6m) budget annually to hydro-map the UK’s coastal waters. The funds would be enough to survey a sea area of around 10,000 sq km. But this figure should be set against a total sea area of 720,000 sq km.

In this situation, the agency will prioritise which parts of the seabed are in urgent need of surveying and which are not. Essentially, it is an approach based on risk. Shipping lanes in continual use by the same ship types tend to be left alone. But where there have been changes, for example, if the location of a windfarm has introduced a new edition to an accepted route or where ships’ draughts have increased, these areas will be prioritised. “We are fairly good at working out the high risk areas,” said an MCA spokesman. In the case of the Octopus , the barge had deviated from the known passage, and it was on this unusual track that the accident occurred.

The case is: base data of some surveys remains hundreds of years old.


Another human aspect of the move to electronic charts is readability. Some argue that it is easier to read and note the age of the source data on paper charts. “It is harder to see the provenance of the underlying data in an electronic chart,” said one cartographer. What he is referring to is "layering" in ECDIS-systems; switching between various layers of information electronically. Layers of data could be switched off and ‘forgotten’ by the seafarer in charge.

Then there is the question of different systems. Electronic charts are here to stay. By 2012, electronic chart display and information systems will start to become mandatory and be on board all SOLAS vessels by 2016.



Another endemic problem is the lack of proper training in using ECDIS.

The user interface is different for different systems. If a system is not set up right, or people are not properly trained, you are in substantial trouble.

In 2008, the ro-ro passenger ferry "Pride of Canterbury" grounded on a charted wreck. According to the MAIB report, the ship’s officer was navigating by eye and with reference to an electronic chart system but “he was untrained in the use and limitations of the system”.

There is an ever present risk of a chart not being up to date. One reason is the simple fact that the correction takes its time from the real world occurence through the reporting system until it's incorporated in a chart, paper or electronic. I won't go into technical details, but depending on the area it can be days, weeks or even months. Or hundreds of years as pointed out above. This is not a unique case, there are charts in use which are based on surveys done in 19th century.



Variouse analysis have shown that ECDIS is improving safety of navigation by increasing situational awareness.

But the mariner needs to be aware that differential GPS provides high accurate position, but that the underlying digital chart still suffers from some of the issues mentioned above.



March 2010, 

Marc Van de Velde

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