Sub-bottom characterisation using a parametric sonar

High quality seabed data are needed in many situations connected with marine surveillance and monitoring. At FOA we are developing remote sensing methods, which use a parametric sonar. It has a very small footprint, which means that individual small objects can be detected and separated. The sonar can be operated with broadband signals, which gives good resolution in the time domain. We have used a parametric sonar in very shallow water in the Baltic. The results of our interpretation are compared to "ground truth" from bottom samples. We have tested the sonar's capability to detect embedded objects by burying test targets into the ground. The recorded signals are then analysed by various detection algorithms. These give the position of the object. The physical properties are then determined by comparison to theoretical calculations on object signatures.