Jan 192013


USS Guardian - thought the reef was eight nautical miles away

USS Guardian – thought the reef was eight nautical miles away

With a US Navy investigation underway to assess the circumstances surrounding the USS Guardian grounding that occurred in Philippine waters at 02.25 on 17 January local time there are lessons already to be learned: Charts are not infallible even if they are on screen and it is not wise to navigate to fine tolerances with the aid of GPS when the underlying data is less accurate than the GPS.

An inaccurate chart is not a defence – not bumping into bits of ground remains the master’s responsibility.

Much of the Philippine waters have not be surveyed for 50 years or more, an issue highlighted when the Greenpeace ship Rainbow Warrior also grounded on Tubbataha Reef in 2005. The chart in use showed the reef 1.5 miles from where it actually was.

The digital chart aboard USS Guardian, an Avenger-class mine countermeasures vessel, showed a position about eight nautical miles in error. At the time of the grounding the vessel was attempting passage through a channel just half that width.

Many Philippine charts have not been re-surveyed in some 80 years. Transferring this aged data to an electronic chart does not increase its accuracy. The current NGA chart for Tubbataha reef appears to be the 1986 edition, based on Philippine charts of 1975 and earlier.

According to a source in the Philippine Coastguard “With the 1940 or 42 charts by NAMRIA, there might really be a problem with  that’s why we are advised to at least have a difference of Three nautical miles from the shoreline, we have to assume that there is one nautical miles changes in the chart already”.

NAMRIA tells Maritime Accident Casebook that the last hydrographic and topographic survey covering Tubbataha Reef was conducted in 2006 using single beam echosounder for the hydrographic data, 2008 is the latest hydrographic survey using multibeam echosounders. The chart was first published last May 2009 and the reef is marked as a restricted area on current charts.

On Friday, 18 January, the US National Geospatial-Intelligence Agency, NGA provided the US Navy with preliminary findings of a review on Digital Nautical Charts (DNC) that contain inaccurate navigation data and may have been a factor in the Guardian grounding.

This followed the realisation by NGA that there might be a potential inaccuracy regarding the Tubbataha Reef digital chart. NGA has reviewed data from more than 150,000 square nautical miles in the surrounding area and found no additional errors.

The incident may also lead to a review of the $30m 2006 joint hydrographic survey agreement between the US Navy and the Philippines after nine years of negotiations. The project was to use advanced sonar technology to map shipping lanes, harbors, and ports throughout the Philippines. However an incident involving a Philippine Maritime Police Patrol vessel firing warning shots against a US Navy survey vessel in January 2008 led to US Navy surveys being restricted to within four nautical miles of the coast.

The project was expected to generate some $300m in commercial value.

The Philippine mapping agency, NAMRIA remains under-resourced, despite the archipelagic nature of the the islands, of which there are more than 7,000.  The agency has been described as competent but with only two survey ships at its disposal to cover thousands of square miles, it does not have the ability to conduct a comprehensive survey by itself using the latest technology.

Hydrographic agencies are not legally liable for errors or inaccuracies of their charts.

A further reason for inaccuracies may occur in geologically active areas where earthquakes may affect depths. And earthquake in Chile in 2010 led to warning not to trust charted depths until they were re-surveyed. Nor is it only a problem in developing countries. In September 2006 the jack-up barge Octopus ground in the Stronsay Firth, Orkney Islands while under tow in waters not surveyed since 1840.

Since DNC mapping is used for safe navigation by Guardian and other US Navy ships, Navigator of the Navy Rear Admiral Jonathan White on Friday released precautionary guidance to all Fleet and ship commanders. White says “initial review of navigation data indicates an error in the location of Tubbataha Reef” on the digital map.

“While the erroneous navigation chart data is important information, no one should jump to conclusions,” says US Pacific Fleet spokesman Capt. Darryn James. “It is critical that the U.S. Navy conduct a comprehensive investigation that assesses all the facts surrounding the Guardian grounding.”

USS Guardian 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. Guardian remains stuck on Tubbataha Reef, approximately 80 miles east-southeast of Palawan Island.

US 7th Fleet ships are on scene along with several support vessels to conduct salvage operations that minimize environmental effects to the reef.

The accident has all the makings of an international incident. The relevant law, Republic act 10067 says: “The TRNP shall be off-limits to navigation, except for activities that are sanctioned by the TPAMB such as, but not limited to, tourism and research. Except in emergency situations, it shall be unlawful to enter the TRNP without prior permission from the TPAMB or the PASu as herein provided. It shall also be unlawful to enter, enjoy or use for any purpose any prohibited management zone. This rule shall similarly apply to the use of vessels, gears and equipment in management zones where such are not allowed.”

See Also:

The Case of the Unwatched ZOCs






  14 Responses to “Lessons From The Guardian Grounding – Don’t Trust Charts”

  1. Very informative and wise, Bob; thank you. Was the Guardian trying to pass between the north and south reefs at night?

  2. Although not concerning the USS Guardian in particular, the following short story concerning the adequacy of hydrographic information on nautical charts – whether paper or electronic, may have some bearing on this subject.

    30 years ago I was involved in an investigation into the grounding of a VLCC transiting the newly introduced TSS at the entrance to the Gulf of Suez. This was a very major incident where the vessel, with a draught of 21.4 metres had hit (I believe the modern terminology is allided) an uncharted coral pinnacle in the middle of the north bound TSS Lane breaching tanks 1C through to 4C causing a very large pollution.

    My role in the investigation was to liaise with the British Admiralty Hydrographic Office as, at that time I was our company representative on the HO Chart User’s Committee.

    The investigation into the cause of this incident centered on the lack of hydrographic information on the BA chart, particularly regarding this coral pinnacle that the vessel had hit, but also all the depth data throughout the TSS. The charted depths were in the order of 30 metres or more. It was noted that the last hydrographic survey of this area had been done by an RN vessel in the 1870’s and there was a note on the chart regarding potential inaccuracies in the charted information. Nevertheless, without any further surveys the Egyptian Authorities had proposed a TSS in this area of heavy traffic and convinced IMO that it should be established and displayed in the normal manner on nautical charts. It was duly approved and introduced.

    Subsequent investigation using USCG survey vessels and divers with cameras identified a mountain range of coral pinnacles straddling the TSS with a number of peaks approaching within 20 metres of the surface. Not only were surveyors able to identify the pinnacle that our vessel had hit, but also noted that many of these peaks showed signs of being hit by other vessels at some earlier time.

    During these investigations I had a number of meetings with HO staff, leading to a presentation by other senior company representatives of our findings, to the Hydrographer of the Navy.

    The Hydrographer was not surprised by what we had found? The hydrographic surveyors of the 1870’s had only been looking for a maximum of 30 feet (10 metres) of depth and it was from this data that the charts were produced! By the 1970’s vessels with draughts in excess of 22 meters were becoming common, but adequate funding for surveys to modern standards were resisted by most governments. Of particular concern were IMO approved TSS’s being introduced, without the need for surveys to modern standards. His many alerts to industry and to IMO regarding the inadequacy of hydrographic data had long been ignored, as had funding for surveys to support non-naval requirements.

    I well, remember some of the examples he gave us, which had been published in his annual report:-
    • Only 30% of the world continental shelves (less than 100 metre depth) had ever been surveyed.
    • The North Sea had never been formally surveyed north of a line joining Rotterdam to Hull.
    • The South China Sea had never been properly surveyed.
    • The Red Sea had never been properly surveyed.
    • The Southern North Sea, other than the Deep Water (DW) routes had not been surveyed to modern standards.
    • The Dover Straits on the English side extending into the TSS SW bound lane had not been surveyed to modern standards.
    • Of the 7500 wrecks which were known to have occurred in North European waters since 1900, only 30% had been found and the depths over them surveyed.
    • To the west of the southern end of the North Sea DW route near Noord Hinder there was a known area of sand waves with a magnitude of 14 metres from crest to trough in an region of less than 30 metres depth and due to lack of modern survey data hydrographers were unable to predict how the sand waves may move over time.

    The Hydrographer made the point that he was particularly concerned about this data being digitized and used in the production of electronic charts, which were in their infancy at this time. He was strongly opposed to such developments.

    Concerned at the Hydrographer’s comments the OCIMF Navigation and Routing Sub-committee was instructed to promptly review, with the help of the HO, the adequacy of all hydrographic data for all TSS’s world-wide. IMO was advised to stop introduction of any further TSS’s until this review was completed. The findings of the review were of such concern, with inadequate hydrographic data identified covering many TSS’s that IMO changed the Ship Routing guidelines within 6 months, requiring that all existing and proposed TSS’s required surveys to modern standards before approval and insertion on charts.

    Hearing the Hydrographers’ comments I fully appreciated his concerns about the future development of electronic charts. I understand why the WHO has shown extreme reticence in agreeing standards for ECN’s to be used in ECDIS equipment and was being prudent in their understanding of these issues.

    Has anything changed over these 30 years to improve the adequacy of hydrographic data? Yes, I’m sure that many areas of the continental shelves have now been surveyed to modern standards, particularly those where there are high traffic flows. I know this to be the case for the Southern North Sea and Dover Straits, but what of all those other areas the Hydrographer mentioned in 1983? I have my doubts! Has funding been provided by governments for the survey of all these inadequately addressed areas?

    The USS Guardian may just be the latest of many incidents over the past several years which tend to confirm that the status of hydrographic data has not improved since 1983 and is now widely digitized and used on many vessels in ECDIS installations.

    Bob Couttie’s article in Marine Accident Investigation website on ECDIS Zones of Confidence raises this issue providing some graphic examples where this was not the case and reinforces my concerns.

  3. For an earlier, an relevant case, some might remember the USN San Francisco. Details here https://www.e-education.psu.edu/files/sites/file/submarine_crash_case.pdf
    Some of those issues will certainly come up in the investigation.

  4. The findings in this report of the USS San Francisco incident regarding hydrographic survey data are very relevant. Concerned that the authors consider it will take many generations (125 years?) for adequate modern survey data to be determined and entered onto charts. These facts regarding the adequacy of hydrographic data used in the production of nautical charts needs to be given more prominence in the training of all Navigators, particularly as we near the implementation of ECDIS on a growing number of the world fleet.

  5. Good afternoon,

    First, full disclosure — my name is Christine Phillips and I’m a public affairs officer with the National Geospatial-Intelligence Agency. I just wanted to provide an update with what we found in our review of the chart data.

    As the Navy has said, until the investigation is completed, the cause of the grounding won’t be known. But we do know quite a bit more about what happened with the chart in this case.

    Bottom line up front is that based on a careful review, we can now confirm that the error in the placement of the Tubbataha Reef in the Digital Nautical Chart was an exception, not a systemic problem. And while no navigational aid is flawless (as has been pointed out by most folks here), NGA is confident that the Digital Nautical Chart is safe for use in navigation. The Chief of Naval Operations concurred with this assessment in a second message sent to the Fleet on 22 January.

    Now…what happened.

    The Tubbataha Reef was incorrectly positioned on the coastal scale Digital Nautical Chart — the coastal DNC showed it about 8 nautical miles from where it should have been. It was correctly positioned on the general scale DNC, and on the standard (paper) chart.

    We very quickly determined that the primary issue in this misplacement was related to LANDSAT-based commercial imagery. So, from January 17 through the morning of January 22, we examined and validated the accuracy of every situation in the Digital Nautical Chart where that type of data was used.

    In total, NGA reviewed DNC charts that cover more than 116 million square nautical miles of ocean. In that review, we identified only one issue of magnitude similar to the misplacement of the Tubbataha Reef. This error, which appeared on both the paper chart and the Digital Nautical Chart, rotated the placement of the southern coast of Chile toward the sea; at its widest, the discrepancy was 7,000 meters. In accordance with our standard procedures, NGA warned mariners to “navigate with caution” in this area when the error was discovered on January 20.

    A total of 25 chart areas – less than one percent of the total DNC holdings — included inaccuracies that required additional scrutiny. Only two of those – the Tubbataha Reef and the Chilean coast – were cause for concern.

    The Tubbataha Reef chart correction has been completed and the patch is available for download now. The correction to the Chilean charts is being worked with the highest priority. The remaining issues do not pose risks to navigation and will be corrected via normal update cycles.

    Ultimately, we found that the error related to the Tubbataha Reef was caused by a combination of factors.

    Prior to 2008, the charts in use included a number of “phantom islands” – the charts indicated islands that did not exist. In response to customer requests to address that problem, NGA used LANDSAT-derived imagery to update the charts. One of these images included incorrect information about the location of the section of ocean that includes the Tubbataha Reef. At the time, no other source information existed to validate that imagery data. As a result, the reef was incorrectly placed in the DNC. That was the first factor.

    The second was simply human error. In 2011, NGA obtained survey data that corrected this positioning. Due to a failure to follow established procedure, this correction was made in one portion of the DNC, but not in another.

    A single source of data is never ideal, and we use multiple sources to validate information wherever possible. As mentioned earlier, we continuously receive new and better information, from a number of sources. As more information is available from more parts of the world, we will have fewer regions where only one source of information exists. That will decrease the risk of errors like this one.

    It’s also worth noting that a very tiny portion of the Digital Nautical Chart is derived from the same type of source data that was at the core of this issue. The remainder of the DNC holdings are drawn from multiple corroborated sources such as hydrographic surveys, information from ships at sea, and U.S. and international nautical charts, to name just a few. As a result, we are confident in the integrity of that data.

    That said, we are going to further review our production processes – including everything from procedures to training and qualifications to resourcing — to determine whether they could be improved. We are assembling a team of experts from across the maritime community — both inside and outside NGA — to assist.

    I hope this helps!


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