To define the morphology of
the seafloor, to study its nature, the distribution of the sediments
and rocky outcrops, the extension of the seagrass prairies,
to detect debris and other underwater objects. This is the scope
of work in a morphologic survey.
· This task is executed using a side scan sonar,
which is composed by a Surface Acquisition Unit (for the control
and acquisition of the data) and an underwater vehicle (tow
fish). During the execution of the navigation lines, the fish
is towed from the vessel and it flies on the seafloor sending
acoustic pulse at regular time intervals
During the execution of each navigation line it is possible
to investigate a corridor from 50 to 1000 m wide, depending
from the resolution requested and the water depth of the work
area. Usually the navigation lines are spaced in order to investigate
the seafloor completely
(SwanPro - Communication Technology)
System – USBL (optional)
CARIS SIPS (Sonar Information Processing System)
is a powerful software system for processing sidescan
sonar imagery and multibeam backscatter data. The
data processing permits the user to mosaic multiple
scenes presenting a continuous coverage.
example of mosaic.
geometry of a side scan sonar. The amplitude of the reflected
echoes depends from the nature of seafloor and its morphology.
User Interface of the acquisition and control software
(SwanPro). The area displayed is characterised by rocky
outcrops and sandy areas with ripple marks
Display to check the
data coverage in the work area
Side scan sonar imagery
processing system (Caris SIPS)
Interpretation and mapping
systems (Caris GIS - Esri ArcView)
positioning of the sonar tow fish is obtained using a USBL (Ultra
Short Base Line) underwater positioning system produced by Sonardyne.
The USBL system involves measuring the range and bearing from
the vessel based transceiver to the transponder installed onboard
the underwater vehicle.
Subsequently the navigation software translate the relative
positions of the underwater vehicle in geographical coordinates.