IMCA Offshore Survey Division

Publication Details

Guidelines for the Use of Multibeam Echosounders for Offshore Surveys

Although multibeam echosounders (MBES) have been in use since the 1960s, their track record in commercial marine operations has can be traced back only as far as the 1990s. The growth in their use has been, in part, due to the ability of these instruments to covr wide swathes of the sea floor in a single pass.

With high-resolution bathymetry obtainable over wide areas and with acoustic frequencies ranging from 10kHz to over 500kHz, multibeam echosounders offer the potential for great accuracy and provide detailed sea floor imagery with scales of economy unavailable from traditional single-beam echosounders.

At the time of publication, some 700 systems had been built by at least ten manufacturers world-wide, of which more than 40% had gone into commercial operations.

However, no specifications or guidelines could be found that specifically addressed the use of MBES for offshore surveying. IMCA's Offshore Survey Division Management Committee established a workgroup to oversee the development of these guidelines, as a means of augmenting existing (in the main more general) documentation and to provide a guide for future specifications.

The guidelines draw heavily on a number of existing standards and published papers by persons eminent in their field and were distributed widely for consultation among key users and client groups prior to publication. IMCA was particularly pleased to receive the endorsement of UKOOA's Survey & Positioning Committee following its valuable collaboration, review and input.

While the IMCA guidelines when originally published in 2001 were welcomed, the formulae for sounding density (section 7.5 and the worked examples in 7.5.1), both along track and across track, had been the subject of debate since the publication of the guidelines because of the view that it resulted in an over-optimistic calculated density. After discussion, consensus has been reached and the formulae adjusted accordingly. Members should consider the application of the formulae carefully in relation to the task in hand. The opportunity has also been taken to update the formatting to the current IMCA style.

Contents

1. Preface
2. Introduction
3. Multibeam echosounders
4. Sub-sea vehicles and systems
5. Calibration tests
6. MBES data processing
7. Standards for MBES surveys
8. Survey planning
9. Terminology
10. Bibliography

It is intended to review and update the guidelines on a regular basis - users of the document are encouraged to forward their comments to IMCA.