Forward Looking Sonar Coming of Age

3-D Imaging

The next logical step beyond the 2-D images produced by most existing FLS and side scan sonars is 3-D imaging. Leading the pack in this area is FarSounder, a small Rhode Island-based company. The 3-D FLS developed by FarSounder can display an amazingly detailed rendition of sub-surface contours and targets within a horizontal field of view spanning up to 45 degrees per side, and from directly horizontal to straight down. An entire "sound picture" is produced using returns from a single ping, refreshed every two seconds. The lightning pace of FarSounder's processing and updating, coupled with the system's long effective range, makes this a viable "real time" watch-keeping tool. It's currently capable of maintaining a dependable and undistorted underwater view at speeds up to 10 knots, and since performance is limited only by processing speed (as long as not aerated), future generations should be able to accommodate even higher vessel speeds.

FarSounder was recently awarded first prize at the International Superyacht Technology and Innovation Awards in Nice, France and currently has an inside track on major contracts with the U.S. Government for producing sonar equipment to protect ships against terrorist attacks. The key to the company's impressive results is some extremely complex data management software that refines the underwater imaging through a sophisticated target recognition process. Signal processing begins with relatively conventional beamforming techniques based on data from a 96-channel transducer array. The system incorporates motion sensors, allowing the image to be stabilized to counteract the effects of pitch, roll and yaw up to 20 degrees. In-water targets nearly always fall within specific categories that can be recognized by the echo signatures they produce. Farsounder's SonaSoft software begins by categorizing targets as "surface" (buoys, sleeping whales, floating logs and semi-submerged shipping containers) or "bottom-related" (nearly everything else). It then determines whether the return characteristics of each particular target characterize a piling, isolated rock, reef, sloping soft bottom or whatever-all at lightning speed.

A serious shortcoming of many FLS units has been their very limited range in shallow waters-typically the circumstances when forward imaging is of greatest potential value. Effective ranges of four to five times the water depth are typical because the convergence of surface and bottom triggers spurious echo returns. Thanks again to state-of-the-art processing, FarSounder claims to have pushed out the effective range of its FLS to 11 times the water depth.

Far Sounder originated as a research project headed by James Miller, a Professor of Ocean Engineer at the University of Rhode Island. Matthew Zimmerman, a former student who developed software for the program, now serves as the company's technical V.P. Cheryl Zimmerman, Matthew's mother, has a strong business background, and came aboard to bring the new FLS technology to market, serving as the company's President and CEO. A local dealer, John Edwards of Sea-Image in Victoria, handles applications throughout the Northwest.

The cost of a FarSounder application is currently in the neighborhood of $70,000 US-still a bit steep for the average recreational boater but low enough to be considered a worthwhile safety and insurance investment for megayacht owners. But, if the history of GPS is anything to go by, advanced FLS prices are likely to drop considerable within a decade.

For a complete copy of this article, see PACIFIC YACHTING, March 2006 edition.