3. Seafloor mapping field manual for multibeam sonar

Swath mapping systems use acoustic technology to collect data on the bathymetry (topography) and the backscatter (impedance) of the seafloor (Figure 3.1). These systems can either be mounted on a ship; autonomous underwater vehicle; remotely operated vehicle or a remote surface vehicle. They work by transmitting a sound pulse, called a ping, through a transducer at a specific frequency (or a range of frequencies simultaneously). This same ping is then recorded through a receiver placed very close to the transducer. The elapsed time that the ping takes to reach the seafloor and return to the receiver is used to measure the depth of the water. Certain attributes of the shape of the sound-wave are used to infer characteristics about the seafloor (geomorphology). Typical multibeam echo sounder (MBES) data products include bathymetry (seafloor depth) as well as backscatter intensity, which can provide a metric for seafloor “hardness” and will indicate the substrate type.