A better picture down below

A COMBINATION of terrestrial laser and underwater three dimensional multibeam sonar scanning technology is offering a solution to complex subsea metrology operations.
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Called BlueView 3D, the technology has been being developed for the past 18 months by Seatronics, Technip, Star Net Geomantics and BlueView Technologies.

This work included several onshore dry dock trials in Peterhead and Fraserburgh in the UK.

Both Seatronics and Star Net have become recommended execution contractors for BlueView BV5000 multibeam surveys for inspection and metrology projects.

Seatronics recently supplied a complete BlueView BV5000-1350 system and personnel for subsea metrology on Talisman Energy's Auk North project in the North Sea. This was the third successful use of the technology.

The technology provided precise measurements between the subsea connection flanges on two manifolds in the Auk North field development.

A manifold had to be integrated into a field with an existing manifold.

The spool piece required between the new and existing manifold had to be accurate to 70mm and have an alignment error of less than one degree.

All the metrology aids had been removed from the existing structure, which caused design issues.

However, Star Net had laser surveyed the existing manifold before its deployment as part of a previous onshore dimensional control survey.

This dataset became critical in the project execution as the subcontractor was able to generate temporary metrology aids from the survey data.

The location of the flanges within the structures caused additional issues from the access point of view.

The BlueView system was successfully deployed by its offshore personnel to perform multiple scans around the subsea structures.

Data quality control was overseen by Star Net operatives onboard the vessel.

Traditional laser scan data augmented the survey data to position the flanges accurately relative to each other. It also gave precise measurement information to aid the fabrication of the adjoining spool piece.

Following the metrology survey the spool piece was designed and fabricated.

As part of the project's completion Star Net surveyed the two-piece pipe section and brought the sections together to confirm the fabrication tolerances.

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