Precision In The Deep
Mooring chains are the lifelines of offshore assets. But how do you measure material loss to the nearest millimeter, in the turbid waters of the North Sea, without ever bringing the chain to the surface?
For a major North Sea operator seeking to extend the operational life of an FPSO, traditional visual inspection methods were no longer sufficient. What was required was objective, measurable data to validate the structural integrity of aging mooring systems. This challenge could not be addressed by a standard ROV contractor or a standalone data-processing firm. It demanded a fully integrated approach.
FILM-OCEAN / ROAV7
Turning cloudy waters
into sub-millimeter data.
Integrated Capture. Actionable Data.
Mooring chains are critical structural components, yet their condition is often assessed with incomplete or indirect information.
By combining Film-Ocean’s subsea operational expertise with ROAV7’s advanced photogrammetry and data processing capabilities, this project delivers a precise and measurable understanding of material loss – without recovering the chain to the surface.
High-quality image acquisition in challenging subsea conditions enables the creation of a dense 3D Digital Twin. This digital representation allows accurate diameter measurements, surface irregularity detection, and direct comparison between the actual geometry and the theoretical chain model.
The result is not just visualization, but reliable metrology – providing operators with the data required to make informed asset integrity and life extension decisions.
Powered by Film-Ocean
Part 1: The Capture
The first challenge was to secure a dataset suitable for high-precision photogrammetry. This required far more than conventional ROV video recording.
Operating in the demanding conditions of the North Sea, Film-Ocean deployed a Work Class ROV using a dedicated acquisition methodology focused on stability, controlled motion, and optimized lighting. Rather than prioritizing speed, the mission emphasized repeatability and image quality.
As Merv New, CEO at Film-Ocean, explains:
“Operating a Work Class ROV in the North Sea is standard business for us. But photogrammetry requires a different mindset. It’s not just about flying the ROV – it’s about stability and lighting strategy. To feed ROAV7’s algorithms, we had to deliver a pristine dataset.
We captured more than 1,300 stereo images of a moving chain in suspension. The collaboration started well before the dive, with a jointly defined flight plan to ensure full coverage and zero blind spots.”
Powered by ROAV7
Part 2: The Processing
Once the dataset was secured, it was transferred to ROAV7’s data processing teams.Their objective was clear: transform raw subsea imagery into a measurable and exploitable 3D Digital Twin.
Using advanced photogrammetry algorithms, ROAV7 reconstructed a dense point cloud of the mooring chain. This allowed direct comparison between the measured geometry and the theoretical cylindrical profile of each chain link, achieving an uncertainty of just ±0.5 mm.
As Maxime Chevallier, Production Manager at ROAV7, explains:
“When we receive a dataset from Film-Ocean, we know the acquisition quality is there. That allows us to focus entirely on the mathematics.
For this mooring line, we reconstructed a dense point cloud and compared the real geometry against the theoretical model. This is not just a 3D visualization – it is a diagnostic tool. We identified surface irregularities and measured link diameters with a level of precision that is simply not achievable by divers using calipers in this environment.”
Measured. Verified. Delivered.
The Result
Instead of a subjective inspection report, the client received a fully navigable Digital Twin of their mooring system, supported by objective and traceable measurements.
Safety
Zero divers deployed in the splash zone.
Speed
Rapid ROV-based acquisition with asynchronous data processing.
Certainty
Actionable metrology to support asset life extension decisions.
This project illustrates the STAPEM Group signature: connecting subsea operational explainability with data intelligence to deliver certainty where it matters most.