Achieving precision in underwater inspections is essential for subsea operations, where even minor inaccuracies can lead to significant operational setbacks. To solidify its status as a trusted solution for subsea inspections, the Discovery Stereo Vision System underwent rigorous third-party validation by Bureau Veritas (BV). This certification process verified the system’s accuracy against standard industry practices, affirming its capability for both long-range and close-range precision measurements.
Testing Methodology: A Closer Look
The certification process involved two primary accuracy tests, each targeting core subsea applications, where accuracy is critical to operational success:
- Linear Accuracy (Drift Ratio) for validating precision in long-range measurements. Target application was addressing accuracy for long baseline subsea metrology
- Local Accuracy for assessing the vision system’s ability to capture fine details at close range. Target application was focusing on localized chain inspections and measurements.
Both tests were conducted in controlled environments using high-precision fixtures and measurement tools. This meticulous approach ensured that results were repeatable and representative of actual subsea inspection scenarios.
Linear Accuracy: Beam Metrology Test
The Linear Accuracy test evaluated the Discovery Stereo Vision System’s ability to measure distances over extended ranges—an essential feature for subsea metrology and large-scale inspections. The Beam Metrology Test was designed to assess measurement drift across long distances, with a 6-meter beam fixture serving as the primary test platform.
Key aspects of the process:
- Test Fixture Design:
The 6-meter-long beam was constructed to maintain rigidity and minimize deflection during testing. Any deformation could introduce measurement errors, therefore the beam’s structural integrity was verified through finite element analysis (FEA) to confirm there were no deflections. Markers were affixed to the beam, and their exact positions were validated using a coordinate measurement machine (CMM), a gold standard for precision measurement.
- Test Execution:
The Discovery Stereo was mounted on a crane and traversed along the 6-meter beam at an altitude of approximately 1 meter. The camera performed two passes along the beam, capturing stereo image data under consistent lighting provided by 4x Nova Mini Lights.
Results: The data confirmed that the Discovery Stereo Vision System met the Linear Accuracy specification listed in its datasheet, and exceeded the operational accuracies defined in IMCA S 019, Guidance on Subsea Metrology with precise measurements across long distances. This verification underscores the Discovery Stereo’s suitability for large-scale metrology tasks, such as subsea infrastructure mapping and dimension verification.
Local Accuracy: Chain Inspection Test
While long-range precision is crucial, close-range accuracy is equally important for detailed inspections of critical assets, such as mooring chains, pipelines, and weld joints. To validate its capability for detailed inspections, the Local Accuracy test focused on the Discovery Stereo Vision System’s ability to resolve fine features and measure small objects accurately.
Key Technical Steps
- Test Fixture Design:
A section of a mooring chain was selected for the inspection test. Small, high-contrast markers were securely bonded to the chain links to serve as reference points. These markers were then measured using a calibrated vernier caliper, ensuring that ground truth values for link diameter and width were established with precision.
- Measurement Process:
The Discovery Stereo was mounted on a remotely operated vehicle (ROV) and maneuvered around the chain to capture high-resolution images from multiple angles, achieving 360-degree coverage of the target. 2x Nova Mini Lights illuminated the chain to enhance visual clarity, allowing the camera to capture crisp, high-detail images.
- Evaluation Criteria:
The primary focus was on the measurement of link diameter and width, as these are critical dimensions for mooring chain integrity. The system’s ability to maintain accurate dimensions in a confined and complex inspection environment was tested rigorously.
Results: The Discovery Stereo demonstrated Local Accuracy as specified in its datasheet, validating its capability to capture detailed 3D models of small, complex objects. This performance makes it an ideal tool for close-range inspections of mooring chains, subsea connectors, and other high-precision inspection tasks.
Setting a New Benchmark for Underwater Accuracy
The Bureau Veritas certification serves as independent validation of the Discovery Stereo‘s performance, confirming that it meets or exceeds the accuracy standards published in its datasheet. By validating both Linear Accuracy for long-range measurements and Local Accuracy for detailed inspections, Voyis has demonstrated that the Discovery Stereo can support a range of critical underwater operations.
These results reinforce its position as a trusted tool for subsea metrology, mooring chain inspections, and precision tasks requiring detailed 3D modeling. With the support of BV certification, users can have increased confidence in the data accuracy of the Discovery Stereo during subsea missions.
Learn more about the Discovery Stereo Vision System’s accuracy and capabilities.
