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.”