Backscatter

Backscatter chart of Dingle Bay

Seafloor backscatter is defined as the amount of acoustic energy received by the sonar after a complex interaction with the seafloor. This information can be used to determine the physical nature of the seabed, because different bottom types “scatter” sound energy differently. Imagine bouncing and catching a tennis ball on a path and then again on some nearby grass. The ball will return with more strength after bouncing on the path. This is because soft ground absorbs some of the tennis balls energy. And so it is on the seafloor, a soundwave will return with more energy if reflected off rocks while a muddy seabed will absorb the energy and return a weaker signal to the sonar receiver.


These differing values can be visualised to show where areas of rock, sand, mud or even coral occur. This information is very useful. At INFOMAR our scientists combine bathymetry and backscatter data collected by MBES to create detailed 3D maps of the sea floor with multiple applications.For example, if you wanted to install a wind turbine on the ocean floor to develop Marine Renewable Energy you need to know what type of seabed to expect. 


Another use is the creation of habitat maps. Different benthic species (those that live on the sea-floor) often live on different types of seabed. Prawns need to live in mud so that they can construct burrows in which to live. Crabs & Lobsters prefer to live among rocks where they can hide from their prey. Herring lay eggs directly onto gravelly ground. If we can tell where the different seabed types are we can tell where different species live and then construct habitat maps. These are useful for conservation, sustainable fishing and in some cases defining Marine Protected Areas. 


MBES backscatter data is routinely acquired by INFOMAR. Once processed, we create freely available Backscatter Charts or you can download the data in various formats here


You can also Compare Multibeam datasets including Backscatter on our new Viewer here

 

Backscatter image

 

INFOMAR delivers three key datasets Bathymetry (or Water depth)Acoustic Backscatter and Water Column Data.