Then Terrill lowers a device called an Echoscope over the side. As we creep along the surface, an onboard computer displays 3-D images of the seafloor in real time.

While side-scan sonar provides a general impression of contours along the bottom, it doesn't directly measure the elevations of features. The Echoscope, or multibeam volume imaging sonar, does, enabling oceanographers to map topography accurately and in high enough resolution to distinguish man-made objects. Terrill describes it as "the oceanographic seafloor-mapping equivalent of ultrasound sonar used to look inside the human body." Using the two technologies in tandem helps to narrow wide-area searches and then pick out targets from clutter on the seafloor, so that human divers maximize their time at the correct site.


http://www.popsci.com/technology/article/2013...ent-175761