Ship & Boat International: eNews March/April 2020
With paparazzi now using drones to snap pics of yachtowners and their guests, and terrorists becoming far less discriminatory about who they target, the yacht sector has become increasingly keen to investigate advanced surveillance systems. Many of these solutions were originally conceived for the defence and commercial sectors, as is the case with Sonardyne’s underwater sonar technology. With a ‘typical’ 100m superyacht costing approximately US$275 million, few owners are unwilling to invest top dollar in solutions that have been proven to safeguard US$600 million jack-up rigs.
“There’s a tendency to think of private yacht security only in terms of above-the-water solutions such as CCTV, lighting, access control and personnel,” says Dan Zatezalo, Sonardyne technical sales manager for US maritime and defence, “but the threat from under the water, be it someone with scuba equipment or controlling a drone, is as great, if not greater, than someone approaching the yacht in a small RIB.”
Sonardyne’s Sentinel Intruder Detection Sonar (IDS) functions as an underwater ‘eye’, warning onboard security personnel should any ROVs/AUVs, divers or swimmers get too close to the yacht for comfort. “Sentinel comprises a sonar head which is deployed below the waterline, a subsea cable, a processor and a power supply,” Phil Parish, Sonardyne operations manager for maritime security, tells Ship & Boat International. “It can be installed permanently or temporarily on the yacht; temporarily, for instance, if there is a requirement for a certain level of security for a specific occasion, such as the visit of a VIP. But, on most superyachts, we’ve permanently installed the sonar head, which is fitted to a through-hull deployment pole leading to the topside, and interfaced with the vessel’s existing command and control [C2] security system.”
Users can adjust the pole length by adding or removing sections, and, once this has been determined, the pole is locked into position. Alternatively, the sonar head can be suspended by cable, or mounted onto a trolley-and-rail system and lowered into the water by winch. An onboard ethernet connection is required to link the components, connecting the sonar head to the topside rack, and then the topside rack to the bridge and/or security room.
Customers can opt for multiple sonar heads, positioned at certain points of the hull to provide full perimeter coverage. “There are several variants of the sonar head, some of which weigh less than 35kg,” Parish continues. The sonar heads measure approximately 330mm in diameter, and are designed to be easily portable, to simplify cleaning and replacement operations.
Sentinel has an object detection and tracking range of 1.5km and will raise visual and audible warnings should a vehicle or swimmer be detected within this zone. The alarm is raised locally for the benefit of the operator and the onboard security staff, though it can also be routed to law enforcement or rescue agencies. Ross Gooding, business development manager for maritime security at Sonardyne, adds: “An integrated underwater loudhailer system can also alert the intruder that they have been detected, and issue instructions, such as ‘Surface now – you have entered a restricted area’.” Such alerts would give non-hostile persons a timely ‘heads-up’ to vacate the area before things escalate.
So, how does Sentinel distinguish between potential threats and harmless ‘objects’ such as wildlife or flotsam? After all, operators don’t want every fish or turtle in the vicinity to trigger frequent false alarms. “Sentinel is both an active and passive sonar,” Parish explains. “With an active sonar, the system emits a pulse of sound and then listens for echoes to detect targets. With a passive sonar, the system listens to detect any potential targets in the water.
“In both cases, Sentinel uses advanced behavioural filtering to discriminate between ‘friend or foe’ – recognising swimmers and underwater vehicles whilst filtering out fish and mammals.” The system essentially applies an automatic detection and tracking algorithm to everything it ‘sees’ and displays only those tracked ‘objects’ that appear to be behaving in a threatening manner. This means sifting through thousands of sonar returns and applying the ‘knowledge’ that the system has built up through years of deployment in the field.
Gooding elaborates: “In addition to this, we use acoustic signature classification on the passive part of the transmission cycle to identify the type of threat. It’s a little like a process used by the world’s navies to identify vessel types – only we use it to identify divers and machines. Sonar works by pulling out the signal from the background noise. So, it stands to reason that if you increase the background noise without increasing target strength, you will reduce the probability of detection. We reduce the effects of this because Sentinel has built-in features to monitor the signal-to-noise ration and then adapt the threshold at which it detects targets.”
The system then arranges and displays threat alerts ranked by factors such as: the object’s range from the vessel; its bearing, position and speed; and the perceived severity of the threat. Obviously, an ROV moving towards the yacht at 3-5knots is going to be of more immediate concern than a swimmer loitering 1,000m away.
Sonardyne adds: “The user interface can be configured to display only threat data, or the complete sonar picture as a transparent overlay onto a satellite image or electronic chart background” – thus giving the crew and/or security detail a more comprehensive overview of the yacht’s environment.
