The U.S. nuclear submarine San Francisco crashed into an uncharted underwater mountain in the South Pacific recently, killing one submariner and injuring dozens of others. The incident remains under investigation, but it spotlights a troubling nautical reality-we may know more about the geography of the moon than that of the ocean floor.
Walter Smith, Geophysicist in NOAA’s Laboratory for Satellite Altimetry in Silver Spring, Maryland, says that even a compilation of all historical data gathered by ships, no matter how primitive, would leave much of the ocean floor uncharted.
Estimates vary, but the amount of properly mapped seafloor in the public domain is likely around 2 or 3 percent. Classified military information could boost that figure to as high as 10 percent, although even the percentage tends to be obscured in layers of secrecy. The result is that current navigational charts are a mixed bag, often recycling data from primitive surveying techniques of past decades or even past centuries.
Survey ships equipped with sound-based systems can map the seafloor with striking accuracy. Survey ships drop a “beam” below them to map narrow swaths of the seafloor. The Naval Oceanographic Office (NAVOCEANO) operates seven survey ships from the John C. Stennis Space Center in south Mississippi. NAVOCEANO has also taken to the air in an attempt to more efficiently map the shallow waters along coastlines.
The Compact Hydrographic Airborne Rapid Total Survey (CHARTS) system uses laser technology and digital imaging to quickly map the ocean floor from the air. But these CHARTS cannot penetrate murky waters, such as those near some river mouths, but it has proven effective over large stretches of coastline. “It works to a depth of about 50 meters (165 feet),” explained NAVOCEANO Commanding Officer Captain Jeffrey Best.