Side-scan sonar

The side scan sonar (English side -scan sonar, sonar: SOund Navigation And Ranging, short form: SSS ) is a based on sound technology for the detection and classification of objects in the water or on the bottom of bodies of water of any kind The application possibilities are versatile: It is both in the military ( submarine hunting, mine detection, etc.) and in science ( biology, geology, underwater archeology) and in the private sector (navigation in general, fisheries ) are used, and rescue organizations use high-resolution sonar systems for locating drowned.

Echo Sounders ( Echo Sounder ), beam echo sounders ( Multibeam Echo Sounder ) and sediment sonars ( subbottom profiler ) are systems that are based on the same technical basis, but operate at different frequencies and geometries; the type of data analysis differs in some cases considerably from those applied in sidescan sonar methods.

With side-scan sonar objects can be located, which are not to be found by optical means in turbid water. The frequencies with which are operated sidescan sonars, range between 6.5 kHz and 1 MHz, the range can be between a few meters and 60 km, and the resolution ranges from a few centimeters up to 60 m; As with all on the emission of waves based systems (radar / ground radar, lidar) is also true for sonar systems, the relationship between frequency resolution and range: higher frequencies bring a better resolution at a lower range. Many modern systems can therefore be operated at different frequencies in order to use them as versatile as possible can.

Basics

The basic functioning of all sonar systems is always the same: It creates a sound wave whose registered echo and calculates the distance to the reflecting object from the measured transit time of the wave. In conventional sonar systems, the sound is focused and emitted in a well-defined direction; can be calculated from the transit time of the echo, therefore, the position of the reflecting object in the three-dimensional space. The situation is different in the sidescan sonar: Here the same two fan-shaped pulses ( " pings " ) are emitted transversely to the direction of the ship, one each to the left and one to the right. This two pings generate through their wide fan shape a large number of echoes, but without the direction from which these echoes come, would be known; the only known parameters are the length of their duration and their intensity. It is therefore not possible with conventional methods from these data to create three-dimensional terrain models, but the results are similar to aerial photos: Also Available in These do not contain any three-dimensional data, they are only the projection of a scene onto a plane dar.