How Do We Explore Collection: Introduction to Multibeam Sonar. Video courtesy of NOAA Okeanos Explorer Program.

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Introduction to Multibeam Sonar Lessons

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!