Reinforcing short-range detection capabilities on small-sized objects
The objective of this configuration is to reinforce a ship’s detection capabilities using a fully automated, stand-alone system, to help the crew perform their assigned tasks more effectively. Indeed, the capabilities of radar systems are limited in certain situations (small objects (such as buoys, people in the water, or items of debris) are rarely detected by a radar and are very difficult for a human being to see), and an ability to see using infrared systems would increase options and efficiency for night-time missions.
The proposed configuration can meet the needs of maritime safety (collision prevention, search and rescue, obstacle avoidance) and can be adapted to provide maritime security capabilities (such as detection of pirates, smugglers and clandestine immigrants).
Larger ships can have additional requirements, such as the detection of people falling overboard (cruise ships) or surveillance of an area of low freeboard or one that can be accessed easily (which could allow intrusion by pirates or undesired individuals), and these requirements can be covered by a short-range detection and display system.
This case study relates to a capability for automatic short or medium-range detection using a configuration that is simple and economical but effective. It is based on a flexible network of cameras making it possible to cover an area of variable size (from several degrees to 90-120°) and distance (200 to 1500 metres approximately). These performance characteristics can be obtained using either a set of fixed cameras or one pan-tilt-zoom (PTZ) camera.
The detection range is directly linked to the characteristics of the camera. As an example, a camera with a horizontal field of vision (HFOV) of 50° is capable of seeing a target measuring 5 x 2 metres (small craft) at 1000 metres (requires a minimum of 2 pixels for detection by the ASV module), while a camera with a field of 30° can see up to 1700 metres, and one with a field of 15° approximately 3000 metres.
The compromises to be considered in this configuration are horizontal coverage versus detection distance on the one hand and fixed camera versus PTZ camera on the other hand:
- Coverage of a wide field (such as 90°) requires only two cameras with an HFOV of 50°, but will only make it possible to detect small craft at a distance of approximately 1000 metres, while coverage by six cameras with an HFOV of 15° provides ‘greater’ detection performance at approximately 3000 metres. However, the budget for six cameras is higher than for two;
- Fixed-angle cameras provide an unchanging view, but have limited identification capability (no zoom), while PTZ cameras can provide good identification capabilities (Z = zoom), but no permanent view: where a PTZ camera is looking on one side, it is blind on the other!