Geoscience Reference
In-Depth Information
3.1 Operating Conditions
In the Baltic Sea there are no strong underwater currents. Image disturbances occur
due to uneven movement of the vessel that tows the sonar. While scanning in the
rough sea, sonar heaves together with the vessel. If the sonar rises higher above the
sea
floor path widens. If the sonar goes down, the image
captured by sonar becomes narrower and distorted. The
fl
oor, the scanned sea
fl
fluctuations of the ship and
the sonar are not completely identical due to the flexible cable that connects the
sonar and the ship [
14
,
15
]. Using current vessel without any additional stabilization
system, the sea
fl
oor scanning surveys can be done only when the sea waves are not
higher than 0.5 m. In order to ensure stable side scan sonar towing, a system that
could accurately capture heave motions of the towing vessel and the side scan sonar
was designed (Figs.
5
and
6
). The initial system operating conditions have to be
determined in order to calculate the engine parameters that ensure the minimization
of sonar
fl
fluctuation in the sea waters [
1
]. According to the ship crew, the maximum
height of the waves that still enables the ship to maintain constant speed and
trajectory is 2 m. We have calculated the maximum speed of the vertical (axis Z)
movement of the starting point, while ship is swimming on h = 1 m waves.
It is assumed that the ship runs perpendicularly to the direction of waves. The
vertical
fl
fluctuation in the axis Z.
Fluctuation of the keel aboard is not taken into account. The simpli
fl
fluctuation of the ship coincides with the wave
'
s
fl
ed equation of
the wave motion is presented as (
1
):
Fig. 5 Chosen start point
Fig. 6 System with a gravitic
depressor
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