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IMCA guidance demonstrates the strength of working together

Published on 25 January 2017

The International Marine Contractors Association (IMCA) has undertaken the ambitious project of reviewing every guidance document in their extensive library, ensuring all are fully up-to-date. Work on the project, which started in January 2016, will be completed in the first quarter of this year.

The comprehensive review has seen the Marine Division Management Committee and Offshore Survey Committees working together to revise some of IMCA’s important guidance covering acoustic and satellite-based position reference systems. The result is two new documents providing guidance to both the offshore survey and dynamic positioning community; and two revised documents of equal use to members of both divisions.

“We’ve been able to use the technical knowledge of manufacturer members and the operational experience from both Marine Division and Offshore Survey Division members to combine, revise and update our existing documents,” explains IMCA’s Technical Director, Richard Benzie.

Diving deeper into the publications

Guidelines on the shared use of sensors for survey and positioning purposes (IMCA S 023/M 235) merges previous IMCA guidance on the shared use of vessel sensors for DP and survey purposes, originally prepared in 2005 and 2007 respectively. Two documents were published separately, as IMCA S 009 -Guidelines for the shared use of DGPS for DP and survey operationsand IMCA S 010 -Guidelines for the shared use of sensors for DP and survey operations. The purpose of these documents was two-fold; to provide guidance in highlighting the risks associated with sharing vessel DP sensors for survey operations, and to provide guidance on developing procedures to mitigate those risks. In 2014, the IMCA Offshore Survey Division Management Committee started a revision of the two documents, and it was agreed at that time that they should be merged to form one common document. This document forms a full and thorough technical revision and merging of the two former documents.

Guidance on satellite-based positioning systems for offshore applications (IMCA S 024/M 242) has been created by merging and revising two earlier IMCA documents,Guidelines on installation and maintenance of DGNSS-based positioning systems (IMCA S 012/M 199) and Guidance on the selection of satellite positioning systems for offshore application (IMCA S 018), both of which were originally produced for IMCA under the direction of its Offshore Survey and Marine Division Management Committees.

The revised document has been prepared by industry experts from the main GNSS suppliers and provides guidance for all parties involved in the selection, installation and ongoing maintenance of DGNSS solutions for use on board offshore vessels, DP and otherwise. These parties include (but are not limited to) ship designers, naval architects, shipyards, DP manufacturers, vessel owners and operators, marine consultants, companies carrying out DP vessel audits and FMEA assessments, and vessel marine crews.

Deep water acoustic positioning (IMCA S 013/M 200) was first produced in 2009. It has been revised and republished first in July 2014, and most recently, during 2016 as part of the ongoing review of IMCA documentation. This document provides an authoritative guide for users and potential users of acoustics for underwater positioning, particularly in deep water. It covers the basics of acoustics and signalling, the equipment required, methods of acoustic positioning and their limitations, and the operation and performance of acoustic positioning systems. The focus is on the use of acoustic positioning systems and techniques for deep water operations, though it should be recognised that many of the techniques and applications are also applicable to shallow water.

Guidance on vessel USBL systems for use in offshore survey and positioning operations (IMCA S 017/(an ‘M’ reference number will be given on publication)) was first developed in 2011. The objectives of this document are to discuss the issues affecting USBL system performance and to describe issues associated with the installation, configuration and documentation of USBL systems on offshore vessels involved in subsea positioning. The document is intended for use by offshore construction, survey and inspection companies when chartering third-party vessels with USBL system(s) already installed, when commissioning new USBL installations on new-build or existing vessels, or when maintaining existing systems.

The recent revision of the document, during 2016, includes taking into account developments in system design and sensor performance, together with high accuracy GNSS surface positioning, that have led to a significant increase in the capability, performance and accuracy of modern USBL-based acoustic positioning solutions. High performance vessel USBL systems, operating to a high specification, can now form a critical part in meeting the very demanding technical and contractual requirements in modern offshore operations.

Obtaining the documents

All IMCA guidance documents can be downloaded free of charge by members from the IMCA website at and can be purchased by non-members. Having determined that printed hard copies are no longer a membership requirement, future revisions, large or small, will be quick and easy to implement. Every document now features a ‘feedback’ button enabling suggestions or changes to be easily submitted by email.