Results from Developments in the Use of a Scanning Sonar to Support Diving Operations from a Rescue Ship

Artur Grządziel

doi:10.3390/rs12040693

Abstract

In recent years, widespread use of scanning sonars for acoustic imaging of the seabed surface can be observed. These types of sonars are mainly used with tripods or special booms, or are mounted onboard remotely operated or unmanned vehicles. Typical scanning sonar applications include search and recovery operations, imaging of underwater infrastructure, and scour monitoring. The use of these sonars is often limited to shallow waters. Diver teams or underwater remotely operated vehicles (ROV) are commonly used to inspect shipwrecks, port wharfs, and ship hulls. However, reduced underwater visibility, submerged debris, and extreme water depths can limit divers’ capabilities. In this paper, a novel, nonstandard technique for use of a scanning sonar is proposed. The new application for scanning sonar technology is a practical solution developed on the Polish Navy’s search and rescue ship “Lech.” To verify the effectiveness of the proposed technique, the author took part in four different studies carried out in the southeastern Baltic Sea. The tests were performed using the MS 1000 scanning sonar. The results demonstrate that the proposed technique has the potential to provide detailed sonar images of the seabed and underwater objects before the descent of divers. The divers get acquainted with the underwater situation, which undoubtedly increases the safety of the entire operation. Scanning sonars are unlikely to completely replace the work of divers but may reduce the number and duration of dives. The sonar use technique turned out to be useful when rescuing a crew of a submarine that crashed and settled on the sea bottom as part of a naval exercise. The sonar data obtained during four experimental tests performed in the Baltic Sea prove the validity, usefulness, and significance of the proposed technique, especially from the standpoint of safety of underwater work.

Highlights

Most of the world’s oceans are inaccessible to humans
There are several factors that determine the choice of the measurement system, but the most important ones to consider are (1) the required object detection, (2) the size of the area to be covered by the measurements, and (3) the depth ranges in the area covered by the acoustic survey
This paper presents a new technique for use of a scanning sonar, which was tested on a rescue ship while performing tasks at sea

Summary

Introduction

Most of the world’s oceans are inaccessible to humans. When exploring wreckages and studying the seabed or other navigation obstacles, people must rely on advanced measurement technology. The great role of hydroacoustic bottom surveying techniques is primarily due to the beneficial properties of propagation of sound waves in the aquatic environment These devices enable complete search of relatively large areas of the seabed in a relatively short time. Several acoustic devices are available for hydrographic measurements of sea and inland waters These include multibeam echosounders (MBES) [1,2], singlebeam echosounders (SBES) [3,4,5], side scan sonars (SSS) [6,7], interferometric sonars, and synthetic aperture sonars (SAS) [8,9,10]. Hydroacoustic measuring systems are not ideal, especially with regard to searching for and identifying very small objects Such activities may require the use of optical underwater inspection methods. The characteristics of the seabed to be analyzed should be examined in detail by divers or autonomous underwater vehicles

Acoustic Systems for Imaging of Seabed and Underwater Objects

Major Application Methods of Scanning Sonar

Study Areas

Case One—Wreckage of the Aircraft Carrier Graf Zeppelin

Case Four—Search for a Hall-Type Anchor

Conclusions