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I bet he didn’t believe his eyes at sunrise either!


We have another instance of electronic charts being suspected of a role in a marine accident. The USS Guardian ran aground at 0225 17 January 2013 (1825 UT 16 Jan 2013) on the Tubbataha reef in the Philippines and it looks fairly likely that ignorance of horizontal datum and failure to ‘maintain a proper look-out’ (IMO COLREG 1972) were to blame. There must have been a series of ignored alarms and indications that all was not right, but somehow the app (DNC plotter) was believed.

“Since DNC mapping is used for safe navigation by Guardian and other U.S. Navy ships, Navigator of the Navy Rear Adm. Jonathan White also today released precautionary guidance to all Fleet and ship commanders. White’s message states, “initial review of navigation data indicates an error in the location of Tubbataha Reef” on the digital map.

The Avenger-class mine countermeasures ship had just completed a port call in Subic Bay and was en route to Indonesia and then on to Timor-Leste to participate in a training exercise when the grounding occurred.”


The source data for Electronic Navigational Charts (ENC) as stipulated for ECDIS and presumably the imageDigital Nautical Charts (DNC) as used by the US military comes from National Hydrographic Offices and is shared by agreement between friendly powers such as UK and US. Here are some snapshots of the paper and ENC charts of the Tubbataha Reef in the Sulu Sea. The data includes centuries of observations and measurements, often with supporting notes on validity and advice on use. It is perilous to ignore the advice but in these days of an app for everything and continuous warning messages from gadgets, the critical details is often lost.

The following are all current, corrected charts which would pass any Port of Flag State inspection. They represent more than enough information for any self-respecting navigator to cross the Sulu Sea without running into anything, the cautionary notes are well-known to seafarers as can be seen here in the continuous series of chart notes on surveys dating back to 1850!


Chart 4507 1:3,500,000 Philippines to Bismark Archipelago


The vessel was on passage from Subic Bay in Luzon north of the Sulu Sea to somewhere in Indonesia to the south. Plenty of sea room to avoid the reef and in an area well known for its sensitive natural environments.

The next bit of his intended voyage would have been in the Archipelagic Sea Lanes around Sulawesi and East Timor/Papua New Guinea to take part in a training exercise.



Chart 3811 1:500,000




Chart 967 1:725,000






Chart 3483 1:1,500,000



That note on the chart say “reefs rep to extend 1.5 miles seaward 2005”




clip_image004What was he doing within ten miles of the reef in the pitch dark - the moon’s altitude was -57° at the time? It was virtually low tide but with only a metre or so range that would not have made the difference between sinking or floating.

Below: ECDIS ENC showing a point plotted using the same co-ordinates. It would be interesting to know the co-ordinates which they were working to.

clip_image002[17]Never mind faulty DNC data or 1.5 mile errors, this is an example of ECDIS assisted casualty which would not have happened if the navigating team had looked at all available sources of information. Not just charts and publications but radar, echo-sounder or even looking and listening out of the window which I am sure told a vivid story at sunrise! Where has this vital information been lost (lost may be the wrong word here as there has obviously been a decision not to include it in the data for the ECDIS or DNC apps).

There was a lot of talk about ‘smart’ vector charts (now known as ENCs and DNCs) versus ‘dumb’ raster charts (ARCS etc) some years ago and a lot of spurious assertions as to the intelligence of the data. It makes little difference if the app is running on a mobile phone, am ECDIS or a nuclear bomb-proof naval command and control system, the only intelligent element of the system is the human navigator.


Teach the navigator how to navigate, not how to use an app.


I am guessing that he was trying to go east-west through the channel about 1.52nM north but just got too close to the reef - same school of navigation as Captain Schettino of the Costa Concordia? clip_image010

It would have been no significant deviation to leave the lighthouse to port, he was only 4 nM from it when he hit the reef so he must have been able to see it out of the window as well as on radar. I don’t actually think he was show-boating as it is an uninhabited atoll and it was dark, but he chose to believe his DNC instead of everything else.


There is no ‘error in the location of the Tubbataha Reef on the digital map’, it is referenced to a different horizontal datum. Digital maps can never be any more accurate than the source data which they have been constructed from and it will be a while before the remote (from US and Europe) parts of the world are referenced to the WGS84 spheroid.

Even state of the art cutting-edge aids to navigation apps require a true understanding of how they work and safety back-up using MKI eyeball pointing out of the window.




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