Using multibeam sonar to map the water column can help scientists learn about fish behavior and aid in fishery management. NOAA image.


What do you think it would take to map the entire ocean? Larry Mayer estimates $45,000 a day and 65,246 days, or about the same amount as an unmanned mission to Mars.

“Why are we so willing to spend $3 billion to map Mars when we won’t spend the same money to map our own planet?” he asked a crowd at the Gulf of Maine Research Institute in Portland, Maine, last week.

To be fair, Google Maps has mapped a good portion of our planet since it launched in February 2005 and now provides a sometimes-unnerving level of detail.

But that’s land. What about water? The ocean covers more than 70 percent of the earth’s surface, after all.

Mayer, the director of the University of New Hampshire Center for Coastal and Ocean Mapping, was inspired at an early age by Jacques Cousteau. He realized that if he wanted to truly explore the ocean, he’d have to image the ocean.

Mayer explained that while people have been mapping the ocean as long as they've had boats, the history of the practice can be briefly summarized because technological advances have been few and far between until recently.

Many of the nautical charts that mariners still use today were created using original mapping technology: A lead weight at the end of a rope dangled off a boat. The first major technological advancement in mapping didn’t occur until the first World War, Mayer explained, when single beam echo sounders were developed to detect submarines. Single beam echo sounders measure the time it takes for an acoustic pulse to travel to the seafloor and back. 

The use of sound pulses to map the ocean overcame the fundamental challenge of trying to image what lies beneath the surface. Light doesn’t travel well in the ocean, but sound does. The information returned from echo sounding can be compiled to create a detailed picture of the seafloor. Echo sounding was a game changer — but because it was originally developed for military use, it didn’t become available to the civilian scientific community until the 1970s.

Since then, single beam echo sounders have given way to multibeam echo sounders, which provide fan-shaped coverage of the seafloor and allow for much more precise imaging.

A researcher points to sonar interference and schools of fish in the EM710 multibeam echo sounder water column display. Center for Coastal and Ocean Mapping photo.

When you stop to think about the application of such information, it’s usefulness seems obvious. It’s important for safe navigation, which is critical to global commerce. It can help scientists understand ocean processes which can inform all kinds of other studies including circulation and wave formation. It can teach us history by helping to find and examine shipwrecks. Multibeam echo sounding even has applications in fishery management through water column mapping — it can educate researchers about schools of fish and their behavior.

Thinking about how much water there is on earth and how much we rely on that water — for food production, global shipping, varying types of resource extraction — it’s shocking to realize how little we know about what's beneath the surface.

Multibeam echo sounding isn’t cheap technology. Mayer said that a deepwater system checks in at more than $1 million and even shallow water systems cost $300,000 to $400,000. Which gets us back to his estimate of $45,000 a day over 65,246 days, or $2.94 billion.

Is it as important as a mission to Mars? It’s a fair question. Imagine how many answers it could provide.

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Jessica Hathaway is the former editor in chief of National Fisherman.

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