Geoscience Reference
In-Depth Information
1 Introduction
In 2012
2020 the Republic of Lithuania will build two major sea transport objects.
These objects are: the lique
-
ed natural gas terminal in the Klaipeda seaport and the
outer deep seaport near Butinge. Examination of the seabed in the waterfront of
Klaipeda and Butinge seaports and under the major sea lanes is very important
(CORPI data funds,
www.portofklaipeda.lt
)
. Sea
floor exploration is important topic
in Baltic region and globally. Kuchler et al. [
1
,
2
] are working on sea crane stabil-
ization. This system reduces motions caused by rough sea waters. Wenlin et al. [
3
]
created system that reduces ship motion in
fl
uence to remotely operated vehicles.
Sarker et al. [
4
] made comparison of several systems for heave motion compensation
on ocean drilling ship. Adamson [
5
] created ef
fl
cient heave motion compensation.
Huster et al. [
6
] designed and tested passive heave compensation for ROV. Other
scientists work with software solutions, such as Trucco and Garofalo [
7
], with their
image merging from twin sonar system solution and Teixeira et al. [
8
] with their
nonlinear adaptive control of an underwater towed vehicle. Yet
Chung et al. [
9
]
presented side scan sonar image correction algorithms, for correcting brightness
variation and patching gaps. New, improved methods are developed, how to produce
the best quality sea
-
floor maps and extract objects of interest, using GIS applications
[
10
,
11
]. Also our team was working on object detection in images produced by side
scan sonar [
12
].
In the coming years the Republic of Lithuania will build two major sea transport
objects. These objects are lique
fl
ed natural gas terminal in Klaipeda seaport, and
outer deep-sea port near B
. Both projects require good preparation. One of
most important preparation part is to explore big areas of Baltic Sea and Curonian
Bay
ū
ting
ė
floor in great detail. Lithuanian territorial waters in Baltic Sea are shallow,
deepest places in sea are just over 100 m deep, in Curonian Bay, where the Klai-
peda sea port is and lique
fl
ed natural gas terminal will be located, waters are just
1
oor imaging in shallow waters Klaipeda University
Coastal Research and Planning Institute use ship with small draught and side scan
sonar system. This system performs well only at perfect or nearly perfect sea
conditions. Image quality produced by side scan sonar depends on how smoothly
the side scan sonar is towed. Most of towed device distortions come from uneven
towing vessel movement. At rough waters small ship heaves a lot, and images
generated by towed sonar are disturbed and not usable. Using current system,
sea
16.5 m deep. For sea-
fl
-
oor images produced by side scan sonar are good quality when sea waves are
up to 0.5 m high. When height of waves is between 0.5 and 1 m, images produced
by side sonar system are distorted, but still usable quality. In Figs.
1
and
2
are
samples of such images with objects on sea
fl
floor. It is much harder to use automatic
object detection using distorted messages, because wavy pattern and big colour
variations. If waves are over 1 m high, sonar images are very distorted and unus-
able. Few methods were designed to improve image captured by the side scan sonar
quality. To reduce vessel heave motion effect to sea
fl
oor images we designed
system that can detect and mechanically reduce motions of side scan sonar.
fl
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