PEARL HARBOR, Hawaii - A U.S. Navy investigation to assess the circumstances surrounding the USS Guardian (MCM 5) grounding that occurred in Philippine waters will include information on faulty digital navigation chart data that misplaced the location of Tubbataha Reef.

On Friday, the U.S. National Geospatial-Intelligence Agency (NGA) provided the Navy 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 that occurred in the Sulu Sea on Jan. 17 Philippine time.

This action followed up on initial contact made by NGA on Thursday, when the mapping organization first realized 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.

Since DNC mapping is used for safe navigation by Guardian and other U.S. Navy ships, Navigator of the Navy Rear Adm. Jonathan White on Friday 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.

"While the erroneous navigation chart data is important information, no one should jump to conclusions," said U.S. 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."

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

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

UPDATED: January 19, 2013