How Do We Explore Collection: Introduction to Multibeam Sonar

Video courtesy of the NOAA Office of Ocean Exploration and Research. Download larger version (mp4, 70.6 MB).




Images of the ocean floor provided by multibeam sonar are a key part of reconnaissance in the Okeanos Explorer exploration strategy for finding anomalies in the deep ocean, and also provide essential information for planning up‐close investigations that use the ship’s underwater robots.

Multibeam sonar is a great example of new technology that allows us to explore Earth’s ocean in ways that simply weren’t possible a few years ago. This is a technology that has directly evolved from sound navigation and ranging systems that first appeared during World War II, and was itself evolved from earlier work begun by the British Admiralty in World War I. Multibeam sonar depends heavily upon modern computer technology to manage a very large amount of data in a very small amount of time, and this combination of systems is another good example of multiple technologies connected together to achieve a specific purpose.

The fundamental idea is fairly simple: make multiple depth measurements in a plane that is perpendicular to the ship, then repeat this process to obtain a series of swaths, then assemble those swaths to form a three‐dimensional representation of the seafloor. Our lesson, “Wet Maps,” for grades 5 and 6, includes a hands‐on replication of this process in which “Beam Teams” may compete to see which team can most quickly and accurately produce a 3‐D model of an unknown landscape. To complete this activity, each team must collect and process around 100 points of data; and this experience can drive home the reason that computers are essential to process the hundreds of thousands of data points that are collected in a typical multibeam survey.

Our multibeam lesson for grades 7 and 8 is titled “Mapping the Deep Ocean Floor,” and uses data from the INDEX‐SATAL 2010 Expedition for an activity in which students create a three‐dimensional surface plot that depicts an underwater volcano called Kawio Barat, which was a primary exploration target for the Expedition. This activity does not use all of the data collected by Okeanos Explorer’s multibeam system ‐ only 182 points ‐ but the result is a recognizable image of the volcano, and once again illustrates the value of computers in creating this image.

In the “Watching in 3‐D” lesson targeted toward grades 9‐12, students use the real image of Kawio Barat produced by Okeanos Explorer’s multibeam system, and manipulate this image using free software that is a scaled down version of software used by ocean explorers aboard the ship. Again, we encourage you to try this activity, regardless of which grades you actually teach, because once you and your students have learned to use this software – which is really quite easy – you will be able to view and analyze many more multibeam images that become available from future Okeanos Explorer missions; and that is definitely something we can all look forward to!