Sonar enters the third dimension

New style of 3-D sensors lets ships avoid hidden obstacles.

By , Staff Writer for The Christian Science Monitor

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    FarSounder's new sonar device allows for 3-D images of what's around a boat. Finally, captains can answer the basic question in navigation: “How deep is the water in front of me?”
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An anonymous garage in an industrial sector of Warwick isn’t the most obvious place to test a revolutionary piece of sonar technology. Yet the inside of this storage facility has been turned into a makeshift laboratory by two scientists who spend more time in face masks and wet suits than the traditional goggles and white coats.

Fresh from a morning dive to retrieve a starfish-encrusted hydrophone (underwater microphone) from a nearby pier, Matthew Zimmerman and Matthew Coolidge turn their attention to testing a similar unit suspended on a pulley above the lab’s showpiece: a 22,000-gallon tank shaped like a rooftop water tower.

Once lowered into the custom-built vessel, the hydrophone barely creates a ripple. But in the maritime world, FarSounder’s sonar stands to make a big splash. It’s the first product to answer one of the basic questions in navigation: “How deep is the water in front of me?”

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Today’s standard sonar, a depthsounder, only communicates the distance to the sea-floor directly beneath a ship. (As someone at FarSounder puts it, it’s like steering a car by only peering through a hole in the floor.) Less commonly used is Forward-Looking Sonar (FLS), a two-dimensional system for small boats that signals the range and bearing of a coming obstacle. But though FLS can detect an object, it won’t describe exactly where it is, nor its dimensions and depth.

By contrast, FarSounder’s new sonar combines all three dimensions – range, bearing, and depth – in a real-time view of the whole volume of water ahead of the ship.

By creating 3-D images of flotsam and jetsam floating in or under the water, it’s ideal for reducing collisions with the thousands of partially submerged containers that fall off cargo ships each year and, more important, avoiding whales.

It’s a perfect tool for navigation through shallow ports and narrow straits. Now, the “ping jockey” on a ship need never play a game of blind-man’s bluff again.

“It gives you a true underwater picture in real time,” marvels Branson Bean, a maritime consultant and writer about technical subjects related to supersized yachts.
Such a product might have come in handy for The Empress of the North, a cruise ship that ran aground off Alaska last year. It might also have warned the Queen Elizabeth II about the uncharted shoal off New England that scuppered its keel in 1992. And it may have saved the M/S Explorer, a cruise ship that guaranteed the journey of a lifetime, from sinking in November after it struck ice off Antarctica, briefly staining a pristine icescape with its red belly before it slipped from view.

In each instance, no lives were lost. But just one calamitous incident could wreck the entire cruise industry, says Craig Eason, technical editor of Lloyd’s List, a daily maritime news publication.

For that reason, cruise ships boast some of the most sophisticated bridge equipment available, he says. No surprise, then, that vacation vessels are a primary market for FarSounder. To date, four cruise ships have been retrofitted with the sonar system, including vessels that regularly voyage to territories such as ice fields.

The company also has commissions from luxury yachts, passenger ferries operated by the San Francisco Bay Area Water Transit Authority, and The World, the first luxury condominium cruise ship. The US Department of Homeland Security has even tapped FarSounder to adapt the technology to detect enemy divers in ports.

It’s a booming start for the 12-employee firm. And, for the most part, FarSounder expects smooth sailing ahead. But it could run into a few jagged reefs as it seeks to expand its market.

One challenge is to get potential customers to understand that its product is fundamentally different from other forward-looking sonar systems on the market. Those devices rotate echosounders in many directions and take several readings to manufacture a multifaceted collage of a small slice of water. FarSounder’s sonar, which fits into the bow of a vessel, doesn’t have any moving parts and creates a real-time image of a 90-degree field of view.

While the company won’t discuss how it created a technology that the US Navy has tried in vain to develop – “It’s a software solution on top of a hardware solution” is all that CEO Cheryl Zimmerman will offer – FarSounder’s cofounder, professor James Miller, says advances in computer processing power have been the key to juggling multiple channels of echosounder data for instant imaging.

The 3-D sonar utilizes an array with about 100 receivers to record signal information. Each “ping” picked up by the unit is transmitted to a computer and run through processing algorithms. The signal information is filtered several times to intelligently extract potential targets. As a ship rocks over the waves, the unit is able to compensate for up to a 20 degree pitch or roll of the vessel and is also able to sift out “surface clutter” such as air bubbles and waves.

Another obstacle for FarSounder could be persuading mariners that 3-D sonar is essential at all – even if FarSounder sales guru Ian Bowles claims, “We think it’s done for sonar technology what radar and GPS has done for navigation above the ground.”

A counterargument is that the contours of ports are meticulously mapped out and ships are able to use satellite navigation to plot exactly where they are, says Chuck Husick, a contributing editor to Guide to Marine Electronics and member of the advisory council of the US Boat Owners Association. Still, Mr. Husick is enthusiastic about FarSounder’s technology and observes that boats do occasionally run afoul of unchartered objects. “An oil tanker in the Delaware River, just south of Wilmington, Del., [hit] an old anchor that nobody knew was there and tore a hole in its bottom [in 2004],” he says.

FarSounder owes its origins to another oil spill. The Exxon Valdez accident off Alaska in 1989 inspired Mr. Miller, a professor of ocean engineering at the University of Rhode Island, to seek a solution to ships running aground. Unfortunately, the company’s sonar still isn’t entirely suitable for tankers because its quarter-mile range doesn’t give the slothful ocean behemoths much time to maneuver at normal traveling speed.

This short range may change. FarSounder has a $2 million grant by the National Institute of Standards and Technology to develop a two-mile range for large ships. Inside the lab, Mr. Zimmerman and Mr. Coolidge take measurements of the transducer’s heartbeat on an oscilloscope, calibrating the transmit signal to proper specifications before they ship the unit to a client.

Zimmerman, who met Miller while studying at the University of Rhode Island and later cofounded the company, enthuses that one of the company’s original goals was to reduce ship strikes, the leading cause of death of the endangered North Atlantic right whale.

“Nobody had a system that could tell you where the whales were and where the rocks were,” reflects Zimmerman. “So, we figured, ‘Sure, we can figure out how to do that.’ Of course, it took more time, more money, and was more difficult than expected. But we’re now doing that in real time.”

[Editor’s note: The original version of this article misidentified North Atlantic right whales.]

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