FarSounder's forward-looking sonar system has a great deal to offer the big-yacht sector. Its 3D images of what lie directly ahead of a vessel not only helps avert potentially disastrous collisions with underwater objects - such as uncharted reefs and rocks, partially submerged containers, or perhaps the odd basking whale - but it can also make a valuable contribution to onboard security. The system is particularly useful for more adventurous cruising schedules that take in waters where charting surveys are poor - the sort of locations that attract expedition and explorer-style yachts.

The FarSounder system is not just a glorified fishfinder - it is robust big-yacht, big-ship equipment - and, surprisingly, it does not have its origins in the military sector.

Initial development of the system was led by a professor of ocean engineering at the University of Rhode Island, and since then the US Navy, US Coast Guard and US Department of Homeland Security have all shown predictable interest in the technology for a host of applications.

Yachts with the FarSounder system installed thus far include new-builds such as the 68m (223ft) Lürssen Kismet and the Devonport 77m (252ft) Samar; plus retrofits like the three-year-old 66m (217ft) Oceanco Dilbar.

At least four large cruise ships have also retrofitted FarSounders - including Clipper Adventurer, Clipper Odyssey, Spirit of Oceanus and The World, says FarSounder's Vice-President of Sales & Marketing Ian Bowles. One of the most recent yachts to launch with the system installed aboard is the 54m (177ft) CRN Maraya and the smallest yacht to have an installation thus far is the 37m (122ft) Trinity-built sports-fish Mary P.

Projects that will incorporate the FarSounder system include the 75m (248ft) Project 703 (Oceanco), the 130m (426ft) Project May (Kusch) and HJB's 62m (203ft) Athos, which will be the first sailing yacht to receive an installation.

Unlike other systems currently available, FarSounder delivers its information in real time and has a range that is good enough to allow plenty of time for the necessary course corrections to be made. It has a range of up to 330m (1,082ft) with its ‘field of view' set at 90º, but up to 440m (1,444ft) with a more restricted 60º picture.

According to Paul Weir - one of the two captains aboard the CRN-built Maraya - its clarity is exceptional. "On this boat our FarSounder can be viewed on any of five Kelvin Hughes bridge monitors. It is so good that I have watched the anchor trip from the seabed and get winched up towards the yacht's bulbous bow, which houses the transducer. I don't suppose you could expect much better definition than that."

FarSounder works by sending out multiple ‘pings' from a sophisticated transducer that provide range and bearing information. This is analyzed by Windows-based software and then converted into 3D imagery. The user can choose the viewing angle too, as if viewing a 3D model on a CAD system or a computer game. You choose what you want to see and if things aren't clear enough you can simply change the perspective.

The transducer head is the heavy bit of the system. It weights in at around 36kg (80lbs). Then there is a rack-mounted ‘power-module' box, which needs to be located within 30m (98ft) of the transducer. Required power supply needs to be 110/220VAC (100W continuous), ideally with a ‘quiet' UPS (uninterrupted power supply), so that no electrical noise pollution can get to the sonar signals.

The transducer for the system consists of a circular black urethane-faced array that comprises around 100 receivers. They all translate to one ‘ping' being received every second, which delivers range and bearing data on any obstruction or debris. The transducer unit is 254mm (10in) in diameter and there's a 178mm (7in) diameter tube behind it with the faring collar at 305mm (12in) in diameter. The faring collar should not be installed with a silicon sealer as water needs to flow through some of the slots in the collar for cooling purposes.

The tubes and collar are made of 316 grade stainless steel, but if required they can be supplied in other alloys in order to be a better galvanic match with hull materials.

When mounting, the array face should look straight ahead but, thanks to real-time roll-and-pitch compensation, it can cope with plus or minus 20º movements without compromising the representation.

Installing the FarSounder FS-3 and FS-3DT units is relatively easy. The transducer module should be located as far forward - and as deep as possible - in the vessel. It is recommended that it is located on a vessel's centreline and at least 915mm (3ft) below the waterline - ideally in bubble-free water, often referred to as ‘clean' water.

An obvious transducer location is around a stem base. The centre of a bulbous bow is ideal - as seen in several of the yacht applications. But they can also be located to the side of a stem in a tube - a solution that can help with particularly pointed bows - but only if the bow doesn't obscure the transducer's ‘field of view'.

Another good transducer location would be in a sailing yacht keel: this is where the one on board Athos will go. And putting the transducer in a retractable pod, possibly one capable of rotating, would particularly suit those with more interest in the security aspects of the technology.

A FarSounder installation should typically require a total budget of US$100,000, of which around US$90,000 would be the necessary for the hardware - including transducer and power controls.

Windows-based software converts range and bearing information into real-time 3D images. The user can choose the viewing angle too . Aboard Maraya, the FarSounder system can be pulled up on one of five Kelvin Hughes monitors.