An echo-sounder measure the sea floor depth below sea surface.
Principle:
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Single beam echo-sounder.
It measures the double way transit time of an acoustic signal reflected on the sea bed.
Water depth under the echo sounder base is computed knowing the sound velocity in water.
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Multi beam echo-sounder.
Acoustic signal is generated through a wide angular lateral aperture transducer.
reflections of the lateral echoes of the sea bed are received from multiples narrow beams.
Water depth are extrapolated along a wide band call swath. The swath width varies from 3 to 7 time the water depth.
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An accurate vessel positioning system is imperatively required (e.g. a DGPS).
Several equipment type exist in this category : Sub bottom profiler, parametric echo-sounder, boomer, sparker.
Gathered data is recorded, corrected from vessel attitude data, wave heave compensated and soundings are reduced from the tide and referenced to a reference level (chart datum, LAT, NGF etc..)
A Digital Terrain Model (DTM) of the sea floor is built.
Isocontours bathymetrical charts are computed and drawn.
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Seabed charting.
Geomorphological and sedimentological analysis of a site.
Requirement of bathymetric chart or data for structure foundation.
Survey of obstructions or existing structures.
Dredging control and cubature calculation.
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