Oceanographers and archeologists have a new tool for uncovering the mysteries of the briny deep. Developed by professor David Mindell of the Massachusetts Institute of Technology, the Exact high-precision navigation system debuted this summer in two exploratory missions. This wireless sonar system uses three acoustic beacons with custom signal processors to navigate and scan an archeological site that's thousands of meters under the ocean's surface, far deeper than any diver can go, to an accuracy of less than a cubic centimeter.
Exact's three beacons, or transponders, are sealed in metal breadbox-size containers. The host transponder is attached to a remotely operated vehicle (ROV) that hovers over the target site. It then signals the other transponders, which are set at the site's edges. The host transponder "pings" the other two, registering their location and pinpointing itself in 3D space. By processing this information, researchers can cover a volume of more than 300 cubic meters on a side.
Next, the ROV travels over and around the site. Its sub-bottom profiler bounces ultrasonic waves off objects under the mud on the ocean floor. With this data, the profiler creates color images of the buried part of the site. Researchers then can map out shipwrecks, structures, and other archeological treasures that would otherwise appear to be hills and valleys of mud.
For details, go to www.mit.edu.
See associated figure.
