On average, 22 people fall off cruise ships every year. However, few cruise ships in operation today have any form of system to detect these man-overboard (MOB) events. MOB events are typically reported by someone who happens to notice the fall or by a member of the person’s party who reports the person missing. Although ships typically have cameras and imaging systems to monitor activity on board the ship, these camera systems are not designed to detect a man falling overboard. Increasing the survival rate of MOB events requires accurate and timely detection, which can be achieved with the patented man overboard detection technology from PureTech Systems.
MOB Video Analytics
Accurately detecting a human falling from a moving cruise ship is not an easy task. An object falling from the top level of a large cruise ship can reach speeds of 70 mph. A MOB system must therefore be able to detect objects moving at these speeds while mounted on the ship itself, which is in a constant state of pitch, roll and yaw. Cruise ships are also very busy environments, with people moving about, blowing debris and a variety of normal operational activities that may involve the movement of items along the side of the ship (ladder deployments, crew boarding, water spray from decks, etc.). And although most cruises tend to target fair weather locations, they still experience all types of weather conditions and sea states. A reliable man overboard detection system must accurately detect human falls in all these situations, while avoiding false alarms and providing the crew with actionable data to react to the situation.
PureTech Systems’ man overboard detection system captures images using thermal cameras surrounding the ship’s perimeter, extending from the lowest passenger deck to the waterline. Thermal video is a logical choice for maritime situations, as it is less susceptible to harsh lighting scenarios, such as sunrise and sunset. It can also provide clear images day or night and in most weather conditions. High resolution thermal sensors can therefore deliver clear visual indications of a human target to the crew for confirmation.
PureTech Systems also employs the use of geospatial video to further enhance the MOB detection capabilities in this busy type of marine environment. Geospatial video provides an understanding of where each video pixel resides in “real” space –latitude, longitude and elevation. This adds another dimension to video analysis by allowing the software to not only understand the physical location of the object, but also the real size, the real speed and the real acceleration. Therefore, although an object may be falling at the same expected speed of a human, a geospatial video solution can understand that this same object is too big or too small to be a human, and suppress the alarm.
Additionally, the use of opposing cameras provides a means by which the video analytics can further confirm the event is happening on the ship itself, and is not something occurring in the background, such as on the water, in the sky or on the dock. In addition to actually being detected in both images, an incident occurring between two camera pairs must pass several additional tests for the duration of the fall – including time stamp, object size, object location, object speed, object type and fall trajectory – on both cameras within the pair before being considered an alarm. This further ensures that the crew receives minimal false alarms.
The man overboard detection system uses maritime specific thermal cameras to ensure the long life and reliability of the imaging sources. The number of cameras required varies by class of ship and whether the ship owner desires coverage at the bow and/or stern of the vessel. A typical superliner class ship looking to cover the entire perimeter of the ship, excluding the bow, might require 16 cameras. The balance of the system includes a commercial off-the-shelf server, which analyzes the video feeds and provide MOB alarms and supporting video data to the bridge and crew.