In their traditional operational conditions, nautical X-band radars transmit an electromagnetic wave and analyze the received signals to identify the obstacles or ships (targets) .To this aim, the echoes backscattered from the sea surface are considered as undesired noise (sea clutter) since they represent a disturbance signal for the targets detection purposes.

Nevertheless, an appropriate analysis of the sea clutter allows us to obtain information on the characteristic sea state parameters (as wavelength, direction and period of the dominant wave, significant wave height), to get estimation maps of surface current and bathymetry and also to retrieve both the direction and the strength of the wind.

The knowledge of this information can play a crucial role in many civil and military applications, which deal with issues as the coastal protection, the safety of ships and off-shore platforms, and castaway's rescue missions.

However, due to the modulation phenomena which affect the microwave imaging procedure, radar images cannot provide a direct representation of the sea state. Nonetheless, the estimation of sea state parameters can be carried out by exploiting a smart reconstruction procedure. In this context, the IREA researchers developed innovative techniques for the processing of radar data which allow us to estimate in real time and with a high degree of accuracy the characteristic sea state parameters, the surface current and bathymetry.

The Figure depicts the block diagram of the reconstruction procedure of the gravity waves. 

To check the accuracy and the reliability of this procedure a number of simulated and real data was used . In particular, the real data have been acquired by mobile platforms and coastal stations.

 Research activity: Sea state monitoring