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High-Definition 3D Tools For Underwater Surveying and Inspection
High-Resolution 3D Scanning Sonar System Allows Rapid 3D Survey of Underwater Structures
and Objects


Dr. R. Lee Thompson
Chief Executive Officer
and Chief Technology Officer
BlueView Technologies Inc.
Seattle, Washington

and
Art J. Schroeder Jr.
Chief Executive Officer
Energy Valley Inc.
Houston, Texas



It is hardly news that meeting the world’s demand for energy is challenging and costly. Resources are increasingly sourced from remote, deepwater and hostile environments. Recent dips in energy costs have been welcomed by consumers, but pressures on the supply side drive the need to control operating expenses to help keep energy prices in check.

With the need to inspect underwater structures and sites on the rise, one way to control operating expenses is to optimize underwater surveying and inspection. Installations, maintenance and decommissioning of offshore structures require detailed data to determine safe, environmentally compatible, economically feasible and efficient courses of action.

New technologies that produce accurate, detailed 3D imagery of underwater structures, sites and objects can improve project planning, reduce costly downtime and minimize the need for return-to-site visits.

In order for these solutions to be effective for both offshore and inshore industries, these 3D surveying technologies must operate equally well in deep and shallow-water environments. The technology also must easily integrate with existing deployment platforms to minimize operating costs.


The Challenge
Physical inspections of structures and sites by divers or optical cameras mounted on remotely operated vehicles (ROVs) have been used for many years. More recently, underwater laser systems have been deployed to determine site and structure condition. While these data-gathering techniques are helpful, they are dependent on water clarity conditions to be effective and accurate. In high-turbidity situations, these techniques are often ineffective, causing increased downtime and costly return-to-site visits.

Additionally, 2D scanning sonar and conventional bathymetry systems (of less than one megahertz) have been employed for many years to generate site and structure imagery. These units have been deployed from a wide range of platforms, including ROVs and tripods. While scanning sonar provides high-resolution top-down imagery, it typically lacks the detailed vertical information needed for complete engineering assessments. Conventional bathymetry data provide sufficient depth and contour information, but do not generally provide adequately detailed and/or unambiguous data on complex underwater structures to enable efficient project planning.

Survey measurements that would otherwise be straightforward on land require complicated solutions underwater, which can contribute to delays or long offshore job-cycle times. For example, the typical method of spool piece metrology at a short-range (less than 20 meters) in deep water requires surveyors to physically attach a transducer array around pipe flanges using an ROV. A transducer array uses the known speed of sound to measure the distance between transducers. To obtain the orientation of flange faces, surveyors also must deploy gyroscopes and inclinometers. All the measurements are combined to generate computer-aided design (CAD) drawings. This current methodology is time consuming and provides multiple opportunities for error.


A New Solution
The need to obtain detailed imagery and accurate data in any underwater conditions is clear. BlueView Technologies Inc. introduced the BV5000 3D mechanical scanning sonar to meet the challenging needs of detailed underwater surveying and inspection with its proprietary MicroBathymetry technology. This technology provides high-definition 3D imaging with as little as one-fifth the size, weight and power required by comparable conventional systems and represents more than 10 years of development.

BlueView’s technology was first developed for the military as an advanced sensor for small autonomous underwater vehicles (AUVs), where space and available power are at a premium. In fact, more than 40 of the approximately 400 BlueView sonar systems built since deliveries began in 2005 are in operation on small AUVs. When compared to traditional solutions, the 3D MicroBathymetry system provides as much as a three times increase in linear dynamic range and a five times increase in acoustic frequency. The smaller wavelengths from higher frequency acoustic waves increase reflected signals from even relatively smooth surfaces, resulting in highly detailed sonar imagery.

The BV5000 system combines high-resolution 3D profiling sonar, a high-precision mechanical pan-and-tilt device and control/display software to generate both sector and 360° spherical scan data to create a 3D point cloud of an underwater structure, object or scene. The compact, lightweight system can be easily deployed on ROVs and tripod-mounted systems. Data captured using the BV5000 is analogous to laser scanner data, making it easy to integrate into terrestrial laser survey software. This allows surveyors to combine detailed underwater 3D acoustic mosaics with 3D laser-scan mosaics to create complete below and above-waterline (acoustic and laser) data sets.

The BV5000 was designed to deliver highly detailed 3D imagery and data even in low and zero-visibility conditions. When combined with 3D topographic laser-scan software like Leica Geosystems’ (Heerbrugg, Switzerland) Cyclone-REGISTER and Cyclone-MODEL, operators can create detailed underwater images and combine multiple point clouds to create 3D acoustic mosaics of wide areas and large structures and objects.


Practical Application Benefits
Recent operations conducted by Oceaneering International Inc. (Houston, Texas) and C-Innovation (Galliano, Louisiana) in the Gulf of Mexico yielded highly detailed 3D underwater mosaics of oil rig structures during the decommissioning process. The detailed 3D images provided project managers and engineers with critical imagery and data of the condition of structures and the site as they were found. The BV5000 was integrated with onboard ROV systems, and multiple area scans were performed without impeding the work in progress. Multiple point clouds were combined into a single wide-area 3D image using Leica’s Cyclone software.

While the traditional method of measuring spool pieces at a short range in deep water requires four distinct steps to obtain data that can be used to create CAD drawings, the BV5000 system can simplify this work. BlueView worked with Seatronics LLC (Aberdeen, Scotland), NB Surveys Global (Aberdeen) and Technip (Paris, France) to conduct metrology tests for this application using the BV5000 system in Aberdeen. The testing was conducted in a dry dock facility using multiple pipes typically found throughout the offshore oil and gas industry.

A standard 3D laser scanner was used first to establish ground truth data of the pipes and position angles. The dry dock was then flooded, and the BV5000 was used to gather the same 3D data.

The 3D laser and BV5000 acoustic data were compared at the point cloud level using Leica’s Cyclone software. Pipe models were then generated from the acoustic-based point clouds, imported into CAD software and compared with optical laser CAD models.

The maximum error measured in the short-range test was 1.1° of angle and 0.45 centimeter of range between flange surfaces.

These results are encouraging, considering that instead of four time-consuming steps, using a BV5000, the process can be completed in two steps with a scan time of less than 10 minutes.

These new tools apply equally well to inshore applications. Combining 3D laser-scan images and data with 3D underwater acoustic scan images provides fused data sets for complete under and above-waterline survey. Complete structure studies can be conducted using a single software source.

Recently, BlueView and Arc Surveying & Mapping Inc. (Jacksonville, Florida) created detailed 3D imagery of a bridge footer in Florida that resulted in an integrated above and below-waterline dataset using an Optech Inc. (Ontario, Canada) laser scanner and a tripod-deployed BV5000.

The resulting detailed data enabled rotational viewing and measurements of the entire bridge footer down to the riverbed, including detailed imaging of the river bottom, debris and erosion surrounding the footer. This provided project managers with a virtual close-up inspection of the complete structure from multiple angles.

Illustration of a Li-polymer battery pack containing four battery modules that SWE built for FMC technologies. Click to enlarge.

Conclusions
BlueView Technologies’ BV5000 3D mechanical scanning sonar creates a new dimension in underwater vision and measurements with proprietary MicroBathymetry technology, compact size and straightforward operation. The 3D mechanical scanning concept adapted to offshore and inshore applications provides state-of-the-art technology to enable informed decisions and streamlined project management. The BV5000 system is an efficient and effective 3D data gathering system that operates in any visibility conditions and is easily integrated onto existing platforms or deployed on a tripod.



Dr. R. Lee Thompson is the chief executive officer, chief technology officer and a founder of BlueView Technologies Inc. in Seattle, Washington. He received his Ph.D. from the University of Texas at Austin and has an affiliate research associate position at the Applied Physics Laboratory of the University of Washington.

Art J. Schroeder Jr. is chief executive officer of Houston, Texas-based Energy Valley Inc., which provides money, marketing and management to commercialize and advance energy-related technologies. He received his master’s degree in business administration from the University of Houston and a bachelor’s and master’s degree of science in chemical engineering from the Georgia Institute of Technology.



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