Echo sounding
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As well as an aid to navigation (most larger vessels will have at least a simple depth sounder), echo sounding is commonly used for fishing. Variations in elevation often represent places where fish congregate. Schools of fish will also register.
Most charted ocean depths use an average or standard sound speed. Where greater accuracy is required average and even seasonal standards may be applied to ocean regions. For high accuracy depths, usually restricted to special purpose or scientific surveys, a sensor may be lowered to observe the factors (temperature, pressure and salinity) used to calculate sound speed and thus determine the actual sound speed in the local water column.
In areas where detailed bathymetry is required, an Autonomous Underwater Vehicle (AUV) can be deployed to make a high resolution map. These maps are made using a multibeam echo sounder that measures the time it takes for a pulse of sound emitted from the AUV to travel to the ocean floor and back. The listening devices on the multibeam are known as transducers. A good multibeam will have around one hundred transducers, each recording the sound coming from a specific direction hence the term multibeam. The travel time and direction of the sound return can be converted to a depth relative to the AUV. The vertical position of the AUV in the ocean is determined using a pressure gauge. The accuracy of this process is in the order of centimeters.
See also
External link
- [Bluefin]
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