Navy Hydrographers Provide Critical Mapping of Ocean Floor

By John Ohab
Special to American Forces Press Service

Jan. 30, 2009 - Advanced ocean-bottom mapping technologies have enhanced the Navy's ability to navigate safely throughout the world and have helped support disaster assistance and humanitarian relief operations, the Navy's oldest active diver said. Michael Jeffries, a Navy hydrographer and technical director of the Fleet Survey Team, spoke with bloggers and online journalists on "Armed with Science: Research and Applications for the Modern Military" on BlogTalkRadio.com Jan. 28 about the science of hydrography and the tools and techniques used to develop precise nautical navigation charts.

Hydrography focuses on measurements and descriptions of the physical characteristics of oceans, seas and coastal areas, including lakes and rivers. The primary purpose of collecting hydrographic information is to support the production of nautical charts, graphical representations of the maritime environment and adjacent coastal regions.

The most important information contained on a nautical chart is the depiction of soundings, or the water depths.

"Whether the user is a fisherman or a captain of a U.S. Navy aircraft carrier, knowing the depths of the water you are navigating is paramount to maintaining the safety of the vessel and all of its crew," Jeffries, a hydrographer for more than 30 years, said.

The Fleet Survey Team, a subordinate command to the Naval Oceanographic Office at Stennis Space Center in Mississippi, supports Navy and Marine Corps global operations by conducting hydrographic surveys that provide critical nautical information, including water depth, tide levels, and the location of navigational aids like buoys, lighthouses, beacons, shipwrecks, rocks and reefs.

The team also conducts expeditionary hydrographic surveys using personal watercraft called "expeditionary survey vessels," or ESVs, to identify underwater hazards during amphibious landing exercises.

"Teams conduct surveys in advance of our amphibious landing forces to determine the most suitable beach landings for the military exercise," Jeffries said.

An estimated 89 percent of Earth's waters have not been adequately charted, and some nautical charts still contain source data from the 19th century, Jeffries said. Furthermore, the marine environment and seafloor are constantly changing due to natural events like hurricanes, tsunamis and earthquakes, and manmade events like shipwrecks and construction. For these reasons, emerging navigation and positioning equipment play an important role in developing the most accurate and up-to-date nautical charts, he said.

"One of the most remarkable technological advances for the science of hydrography is the use of satellites for positioning and navigation," Jeffries said. "With our current technology, we can refine [positioning] to less than 1 centimeter."

The Fleet Survey Team employs a variety of high resolution sonar systems to define the topographic characteristics of the seafloor. Portable sensors known as "single beam echo sounders" can be outfitted on ESVs to provide depth information. A specialized sensor called "side-scan sonar" is the main tool used by the Naval mine warfare community to locate mine-like objects and other obstructions on the seafloor.

"The key to accurate hydrographic surveying is precise positioning of your vessel and the sensors that collect information about the seafloor," Jeffries said.

Comprising 65 military and civilian personnel, the Fleet Survey Team plays a critical role in support of disaster assistance and humanitarian relief operations. After the 2004 tsunami that struck the coastal town of Banda Aceh, Indonesia, teams surveyed for underwater hazards and cleared waterways for relief ship traffic. Recently, it conducted joint hydrographic surveys with the National Oceanic and Atmospheric Administration, the U.S. Coast Guard and the Army Corps of Engineers to ensure that waterways were clear in Texas and Louisiana after hurricanes Ike and Gustav.

"Whether here in the U.S. or anywhere else in the world, our 'fly-away teams' comprised of three or four Fleet Survey Team members hand-carry suites of sonar sensors with them," Jeffries said. "Upon arriving at their mission location, the teams install these sensors onboard any platform that is made available to them."

The Fleet Survey Team also supports joint hydrographic survey operations with more than 20 international partners.

"Partnership building with other countries contributes to the security and stability of the maritime domain, and this most certainly benefits all of us," Jeffries said.

(John Ohab holds a doctorate in neuroscience and works for the New Media directorate of the Defense Media Activity.)