Small Object Detection

The detection of small objects using the SeaDarQ system uses a space-time model for sea clutter propagation measurements and applies filtering techniques, based on information derived from prior images. This methodology enables information to be drawn from the backscatter signature, which is normally lost in the sea clutter, and results in a greatly increased detection capability for small nearby objects.

Clutter Filtering for Detection of Small, Slow Moving Floating Objects

Small floating objects, such as rubber boats and jet ski's have a very low radar reflection compared to the reflection of the sea surface, i.e. the sea clutter. Conventional detection methods do not suppress this sea clutter and as a result, small floating objects are not visible due to the low signal to clutter ratio.

Investigation over the past 25 years has identified that the evolution of sea clutter can be considered a deterministic process, if it is assumed that the propagation of sea clutter from radar scan to radar scan is directly proportional to the space-time evolution of the sea surface. With this data, the SeaDarQ system makes use of the space-time model for sea clutter propagation and subtracts the predicted clutter from the actual scan results in a residual image. This creates an image of features not predicted by the sea clutter model, including an image of any small objects present. The SeaDarQ system uses this adaptive filtering in combination with AIS identification and tracking systems to greatly increase the detection capability of small nearby floating objects.

Ship Wake Detection for Moving Targets

Ship wakes are the result of water disturbance caused by the ship's hull and the action of screws. Their visibility in radar images depends on the sea surface roughness caused by the wind, and on the propagation direction of the wake relative to the looking direction of the radar. For navigation radars which have low grazing angles, observation of ship wakes requires higher sea state conditions. It is under these conditions that small objects are difficult to observe. The SeaDarQ system uses a number of algorithms to detect different features in a ship wake which are visible by radar. Testing and recordings have shown the SeaDarQ system is successful in detecting small moving objects by means of identifying the wake these objects make.

Validation and Testing

Numerous tests have been completed to assess the capabilities of the SeaDarQ system to detect small objects. In Dubai, tests and recordings have recognised small objects, such as pieces of wood, plastic and metallic barrels, foam markers, buoys, small boats and small floating objects.

To summarise, small object detection using the SeaDarQ system has been designed to detect both small floating objects and moving targets. It successfully operates during all sea conditions, and even functions during high sea states when objects are hidden in the waves.