High levels of in-water noise generated by such vessels and their seismic sources have necessitated corresponding new acoustic methods for detection of thousands of positioning signals.

Meanwhile, Sonardyne also reports the sale of an ROV-Homer acoustic positioning system to the Japan Marine Science & Technology Centre (JAMSTEC) for installation on its full ocean-depth ROV, Kaiko.

The system will be used to relocate research instruments sited in the Japan Trench at depths of 7,000m as well as the Marianas Trench at 12,000m.

The latter application is thought to signify the deepest-ever use of acoustic positioning equipment.

The system is a range and direction guidance facility for ROV's and is specifically designed for rapid and efficient relocation of underwater targets such as lost diving bells, divers, seabed equipment and small objects.

It is the second such unit to have been acquired by JAMSTEC following earlier installation of one aboard its Shinkai manned submersible used for a wide range of international research projects in depths down to 4,000m.