Guidance on Subsea Metrology

Subsea metrology surveys are conducted to determine accurately the relative horizontal and vertical distance between subsea assets, as well as their relative heading and attitude. This information is then used by pipeline engineers to design connection pieces to join the assets together. The document, which has been developed by DOF Subsea under the direction of the IMCA Offshore Survey Division management committee, and reviewed by members of the OGP (International Association of Oil & Gas Producers) Geomatics Committee, explores the most common subsea metrology techniques in use today - long baseline (LBL) acoustics, both diver taut wire and digital taut wire, photogrammetry, and inertial navigation systems (INS).

The new 32-page document can be downloaded free of charge from the IMCA website; printed copies are available at GBP10 for members and GBP20 for non-members (zero VAT, plus 20% for delivery outside Europe). Sections include an Executive Summary with short definitions of the five subsea metrology techniques; a glossary; introduction clarifying terminology; subsea metrology requirements; fuller detail on each of the subsea metrology survey methods; subsea metrology deliverables; and references and further reading. Appendices cover dimensional control requirements for metrology; a typical subsea metrology diagram; and a comparison of subsea metrology systems. It does not compare or evaluate different manufacturers' products or services, or the specific performance of systems, and does not endorse or recommend a specific type, model or make of system.