Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Development of an Underwater Towed Exploration System for Archaeological Relics
Satoru Yamaguchi
Department of Marine Systems Engineering, Kyushu University
Fukuoka, JapanYu Fukuda and Yuta Shindo
Graduate School of Engineering, Kyushu University
Fukuoka, Japan

ABSTRACT

accuracy.

Many archaeological relics such as a wreck of an ancient ship areremains under the sea bottom and most of them are untouched becauseof difficulties of underwater exploration. Usual sub-bottom explorations
for offshore resources such as oil and gas are carried out using seismicand sonic prospecting instruments and it is high cost and time consuming.
On the other hand, archaeological relics in the relatively shallow water
are explored by a sub-bottom profiler and by divers so the area which
can be investigated is very limited.

In the step of the relic exploration, the diver manually performs thesubsequent survey according to the primary sonic prospecting whichmeasures abnormal reflections in the target area. In the manual survey
using a surveying rod, the accurate positioning of the target inunderwater is a big issue because the precise positioning by GPS cannot
be performed in the seawater.

The authors have been developing underwater towed vehicles andautonomous underwater gliders in the previous studies. These vehicles
equip various types of instruments including an OBEM (Ocean Bottom
Electro-Magnetometer). They are promising instruments for marine
environment survey and ocean floor resources exploration.

A steel frame is installed at the target area on the seabed and the positionof the target object in the frame is actually measured manually. The
diving term is limited by the depth of water and only a part of the target
area which shows abnormal reflections in the sonic prospecting can besurveyed by this method. So, the many promising sites are left untouchedwithout detailed survey.
Various instruments are used in subsea survey of geophysical andunderwater archeological field. A geophysical survey using a side-scansonar and a high-resolution sub-bottom profiling was carried out toreconstruct the evolutionary history of Lower Lough Erne,
northwestern Ireland using chrono- and bio-stratigraphic markers(Lafferty, Quinn, Breen, 2006). High-resolution marine seismic dataacquisition and subsequent analyses are highly influenced by sea
conditions. A multi-beam echo sounder data and chirp sub-bottom
profiler data require special correction to keep data quality (Kim, 2017).
The sub-bottom profiler can capture the sediment interfaces andproperties of different types of sediment. An integrated horizon picking
method including the diffusion filtering method, the enhancementfiltering method and the local phase calculation method was proposed toobtain the main and detailed horizons (Li et. al., 2021).

In this report, a towed exploration system for archaeological relics
exploration is proposed and the development of the vehicle including a
motion controller is discussed. The vehicle is towed near the sea bottom
to improve the accuracy of the measurement using a sonic prospector.
The performance of the towed system and its motion control system areassessed by tank experiments and numerical simulations.
KEY WORDS: Towed vehicle; underwater exploration; archaeologicalrelics.
INTRODUCTION
In underwater archaeology explorations, there are many problems tosurvey objects buried under the seafloor, such as the selection of themeasuring instruments, accurate positioning method in underwater, thedepth of the surveyed sea area, the cost of the equipment, etc. The survey
area is very limited consequently.

An autonomous underwater vehicle has an ability to achieve acontinuous resource exploration autonomously for a long term. The
motion control system for landing of the vehicle was investigated in theprevious studies (Yamaguchi and Miyai, 2020). In these reports,hydrodynamic performance of the vehicle in landing was examined by
CFD calculations. The bottom effect which affects the lift and drag of
the wings of the glider was studied and the characteristics of the blended
wing body near a sea bottom was discussed. The authors attempt to adopt
the underwater vehicles for the archaeological relic’s exploration in thisresearch. In order to solve the above problems in underwater

In general, for the exploration of survey of sunken ships buried in a
relatively shallow area, very expensive devices for the offshore oil andgas explorations are used. They have ability to measure up to a depth ofseveral kilometers below the seafloor. It cannot be said that these
instruments are suitable for underwater archaeology in terms of cost and1200