Geophysical
survey includes the application of many technologies, for the study of the
bottom bathymetry, morphology and nature.
Navigation tools are the way the position is checked and all acquired
information is geo-referenced; they include GPS for location, gyro for
identification of survey direction (heading), motion sensor for detection of
ship movements (pitch, roll, heave) and navigation software for
visualization of the ship position and of all collected data.
Bathymetric survey is performed by means of
echosounders, which record the travel time of acoustic waves emitted from
the transducers and reflected from the sea bottom. Singlebeam echosounders
provide the measure of depth along the ship track, while multibeam
echosounders provide the depth record along a corridor (swath) beneath
the ship. Sub-bottom survey is performed
through sub-bottom profilers (among which the chirp technology) which record
the travel time of acoustic waves reflected by different horizons present in
the subsurface, allowing to study sediment stratigraphy.
Side-Scan-Sonar provides a sonogram of the sea bottom
acoustic backscattering, which depends on the nature (roughness, grain size)
and on the morphology (presence of steep walls or shaded areas) of the
substrate. |
