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2D and 3D Sonar Imaging

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ASI has designed and built a dual axis sonar system that is capable of operating in high flow conditions and provides accurate dimensional information regarding the structure and accumulated debris. This approach was used to obtain a full coverage scan of a flooded surge shaft, the intake structures of hydro electric stations and the forebays of nuclear plants, all while the plants were under fully operational conditions. 

Dimensioned maps were generated providing data regarding debris accumulation on the face of the structure, “as-built” information, and sediment deposition (bathymetric information) in the vicinity of the structure.  This technology provides underwater infrastructure operators accurate inspection data, without the burden of costly downtime.

The dual axis sonar consists of scanning sonar integrated with a precision actuator. By rotating through a minimum of 180 degrees on the secondary axis, full coverage of the submerged asset is obtained.  For increased accuracy the speed of sound may be calculated based on the water depth, temperature and conductivity.

Intake Structure

To maximize the performance of any intake, it must remain free of debris.  With multiple setups of the dual sonar system, it is possible to generate a point cloud representation of an entire intake face and the surrounding bathymetry without requiring a shut down. An accurate measurement of the amount of debris can be determined and the data can be viewed as the scan is taking place, providing immediate results.

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When multiple scans are performed across the face of an intake, the point clouds may be merged by determining common points in adjacent scans and lacing the data sets together. Generating a point cloud representation of an intake structure at scheduled intervals can provide both the ability to predict when a shutdown may be required to facilitate debris removal as well as prevent an unnecessary shutdown.

Forebay Sediment Monitoring

Determining sediment deposits and debris accumulation has been the primary objective for most of ASI’s dual axis surveys; scour and erosion are other viable objectives that such a survey can target. These surveys would be most effective when a baseline survey is available with which to compare subsequent inspections.

Benefits of Dual Axis Sonar Surveys

  • Real Time Monitoring of sediment accumulation in critical facilities that may be subject to rapid build-up
  • construction projects where active changes to the seafloor or river bed are part of the project.
  • monitor an underwater construction process such as a drilling or dredging operation using rate of data collection
  • observation of collapse or undercutting taking place and take corrective action
  • Remote measurement of silt and debris accumulation or scour and erosion
  • collects more points in a denser pattern than a single axis system within a given time period
  • eliminate costly shutdowns
  • information gathered can be used to develop more economic maintenance program


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