Side viewing sonar
The side scan sonar ( English side-scan sonar , short form: SSS; Sonar : SOund Navigation And Ranging) is an on sound -based technology for locating and classifying objects in the water or at the bottom of bodies of water of any kind The applications are versatile: It is. Used both in science (geology, underwater archeology and biology), in the commercial sector (general shipping, fishing) and in the military sector ( submarine hunting , mine detection, etc.). Rescue organizations use high-resolution sonar systems to locate drowned people.
Sonar (echo-sounder), subjects sonar (multibeam echosounder) and sediment sonars (subbottom profiler) are systems that are based on the same technical basis, but operate at different frequencies and measurement geometries; The type of data analysis also differs, in some cases considerably, from the methods used with side-view sonars.
With side-view sonar, objects can be located that cannot be found with optical means in cloudy water. The frequencies with which side vision sonars are operated are 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 to 60 m; As with all systems based on the emission of waves (radar / ground radar, lidar), the relationship between frequency, resolution and range also applies to sonar systems: higher frequencies bring better resolution with a shorter range. Many modern systems can therefore be operated with different frequencies in order to be able to use them as versatile as possible.
Basics
The basic functionality of all sonar systems is always the same: A sound wave is generated, its echo is registered and the distance to the reflecting object is calculated from the measured time of flight of the wave. With conventional sonar systems, the sound is bundled and emitted in a precisely defined direction; The position of the reflecting object in three-dimensional space can therefore be calculated from the transit time of the echo. The situation is different with the side-view sonar: Here, two fan-shaped impulses ("pings") are transmitted across the direction of travel of the ship, one to the left and one to the right. Due to their broad fan shape, these two pings generate a large number of echoes, without the direction from which these echoes come being known; the only known parameters are their duration and their intensity. It is therefore not possible to use conventional methods to create three-dimensional terrain models from this data; rather, the results are similar to aerial photographs: These do not contain any three-dimensional data either, they merely represent the projection of a scene onto a plane.
literature
- Gerhard Aretz: Sonar in theory and practice for underwater applications. Monsenstein and Vannerdat , Münster 2006, ISBN 3-86582-393-9 .
Web links
References and footnotes
- ↑ Blondel, Philippe: The Handbook of Sidescan Sonar. Chichester, UK, 2009, p. 8