Underwater inspections are pivotal in maintaining the integrity of offshore energy infrastructures. Traditional methods, such as multibeam echosounders and underwater laser scanners, have dominated horizontal inspections of assets including pipeline or unburied cable and accurate measurements. However, when it comes to vertical inspections, newer computer vision-based technologies such as photogrammetry and VSLAM (Visual Simultaneous Localization and Mapping) offer significant advantages. This blog explores the benefits of a computer vision setup for visual inspections of vertical underwater assets: the Voyis Discovery Stereo camera integrated with Voyis VSLAM Powered by EIVA NaviSuite. This is then compared to the use of underwater laser scanners for horizontal scopes, such as the Voyis Insight Underwater Laser Scanner, providing insight into when to use each technology for optimal results.
As an experienced manufacturer of both solutions, Voyis is particularly well placed to objectively compare the two approaches.
Understanding Vertical and Horizontal Underwater Inspections
Vertical Underwater Inspections
Vertical inspections focus on examining structures that extend vertically from the seafloor. These include offshore oil and gas platform legs, risers, and vertical sections of subsea installations. The primary goal is to assess the integrity and condition of these vertical components, detecting any signs of wear, corrosion, or damage that could compromise the structure’s stability and safety.
Horizontal Underwater Inspections
Horizontal inspections, on the other hand, are concerned with structures that extend laterally along the seafloor. This includes pipelines, seabed mapping, and horizontal structural elements of offshore platforms. These inspections aim to cover large areas to check for where there may be threats to the integrity of these components, identifying issues such as leaks, structural deformations, or seabed movements that might affect the infrastructure.
Benefits of Computer Vision Technology for Vertical Underwater Inspections
Superior Detail from Every Angle
Combining the Discovery Stereo vision system with integrated software, the Voyis VSLAM Powered by EIVA NaviSuite solution excels in vertical inspections. The system captures high-resolution images for use in constructing detailed 3D models of structures such as risers, platform legs, and manifolds.
The Discovery Stereo camera doesn’t only provide superior image quality when compared to standard underwater cameras, but crucially, thanks to the integrated software, it can perform 3D reconstructions dynamically, continuously building the 3D model as it observes the object of interest from multiple angles, adding additional detail at every position change. This is key when detecting minute defects and ensuring the structural integrity of offshore energy infrastructure.
All of this is achieved without the need for accurate positioning and attitude data, which is notoriously challenging when navigating vertically.
Complete Survey Data QC
Data collected from the Discovery Stereo is processed in real-time into an initial 3D reconstruction using VSLAM algorithms. This 3D display helps the surveyor validate that the image data is effective at detecting target features, and that full coverage is achieved, prior to survey completion.
The solution thereby ensures that adequate data is collected for performing photogrammetry in post-processing to subsequently generate a 3D textured mesh model for data delivery.
The real-time generated coverage map offers benefits for piloting complex structures. With respect to the object being reconstructed, pilots see both a real-time display of the vehicle position and attitude, as well as the path navigated, meaning the vehicle track over time. This coverage map also provides an overview to help pilots save time by avoiding returning over areas already inspected.
Adaptability to Dynamic Environments
Vertical structures in offshore energy installations are often subject to dynamic conditions, such as varying currents and light levels. VSLAM technology creates a point cloud using visual feature matching of consecutive images. Compared to laser scanners, this approach is much more reliable in dynamic conditions, where the survey is not being carried out from a fixed point of view or travelling along a continuous navigation pattern. The Discovery Stereo camera’s ability to function effectively in low-light environments further enhances its suitability for vertical inspections, where lighting conditions can be challenging.
When to Use Laser Scanners for Horizontal Inspections
Precision in Detailed Measurements
Underwater laser scanners are highly effective for horizontal inspections where precision and detailed measurements over extended areas are paramount. These devices emit laser lines to scan surfaces and create accurate 3D models. They are ideal for tasks requiring meticulous detail, such as inspecting pipelines, seabed mapping, and horizontal structural assessments.
Wide Area Coverage
Horizontal inspections often involve covering extensive areas, and laser scanners excel in providing comprehensive coverage in a timely manner. Their ability to scan large sections of the seabed or horizontal structures ensures that no detail is overlooked, making them indispensable for broad-range inspections.
Inspection of Featureless Environments
The Insight Underwater Laser Scanner can create 3D Models even in environments with no features detected. The laser will project a laser line which will be captured regardless of seabed’s characteristics, creating a detailed model.
Choosing the Right Technology: Computer Vision vs. Laser Scanners
The decision to use computer vision or laser scanners depends on the specific requirements of the inspection task. For vertical underwater inspections, particularly in offshore energy applications, the Voyis VSLAM Powered by EIVA NaviSuite solution offers unparalleled benefits in terms of data coverage, ease of deployment, and adaptability to dynamic conditions. In contrast, for horizontal inspections requiring wide area coverage, underwater laser scanners remain the preferred choice due to the faster processing time for large datasets of laser data. This is because the VSLAM solution’s process is more data intensive and computationally heavy than laser scanners, and therefore does not scale well to larger areas.
By understanding the strengths and limitations of each technology, inspection teams can make informed decisions, ensuring optimal inspection results and maintaining the safety and integrity of offshore energy infrastructures.
The future of underwater inspections
The integration of VSLAM technology, specifically through the Voyis Discovery Stereo camera and EIVA NaviSuite, marks a significant advancement in vertical underwater inspections. While laser scanners maintain their relevance in horizontal inspections of large areas, the unique benefits of the VSLAM technology make it an indispensable tool for structure inspection, for example in offshore energy applications, civil engineering and defence.
By leveraging the strengths of both technologies, we can achieve comprehensive and accurate underwater inspections, safeguarding the future of offshore energy operations.
