Sonar enters the third dimension
New style of 3-D sensors lets ships avoid hidden obstacles.
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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.Skip to next paragraph
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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.]