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In March 2015, 2G Robotics performed demonstration scans at the Fisheries and Marine Institute of Memorial University in St. John’s, NL in order to validate the ease of operation of the ULS-500 underwater laser scanning system and to demonstrate the system’s 3D point cloud visualization capabilities.

 

“Researchers were able to gather information about a trawl that would normally be more difficult to obtain”

-George Legge, CSAR Facility Supervisor

 

2G Robotics’ ULS-500The Marine Institute’s Centre for Sustainable Aquatic Resources (CSAR) is home of the world’s largest flume tank. The tank is used predominantly for studying fishing gear, specifically scaled models of fishing gear. Relationships are drawn from the scaled-down gear, allowing gear technologists to predict performance of full-scale fishing gear without actually going to sea. This use of scaled models is an effective means of pre-testing experimental gear as well as newly designed fishing gear.

 

In evaluating fishing gear, there are a number of common geometrical parameters of interest such as the horizontal spread at the wingtips of a trawl and the height of the trawl from the seafloor. At sea, these parameters are typically measured with hydro-acoustic sensors. In the flume tank, positioning cameras are able to provide three-dimensional data, but in an indirect manner. Two camera systems, one mounted above the water and the second mounted adjacent to the viewing gallery windows, provide YZ and XY planar data. This data can be used to provide positions of discrete points within the tank. Typically clients are satisfied with these straight line measurements, but the ability to capture a complete 3D data set of the fishing gear via laser scanning was of interest to CSAR researchers.

 

 

 

Red Fish Trawl Scan using the ULS-500

 

3D point cloud model of a red fish trawl

 

 

 

For the demonstration, 2G Robotics worked with George Legge, the Facility Supervisor, to scan trawl nets, a crab pot, and a flange using the ULS-500. The ULS-500 with rotary actuator was hoisted by crane into the flume tank and anchored horizontally to the movable platform positioned across the width of the tank. For scanning the shrimp trawl net and red fish trawl net, a flow rate was set and the platform was incrementally moved to allow the ULS-500 to scan segments of each net. These segments were merged in post-processing to produce complete 3D models of the top and sides of the nets. For capturing the flange and crab pot, the platform remained stationary and no flow rate was set.

 

“The ULS-500 did an excellent job capturing data which would otherwise take a great deal of time to acquire.”

-George Legge, CSAR Facility Supervisor

 

As the scans progressed, the formation of the point clouds was available for previewing in real-time using the 2G Robotics Scanner Application software. Legge commented that “researchers were able to gather information about a trawl that would normally be more difficult to obtain. Parameters such as mouth opening and mesh opening were more easily extracted using the 3D models generated by the laser scanners.”

 

With the Marine Institute’s current metrology method, there is minimal capability for additional information extraction from the acquired data. This potential lack of information means that queries regarding the fishing gear sometimes remain unanswered, or require further testing.

 

Legge commented that the “most recent series of tests with 2G Robotics provided an opportunity to demonstrate the technology on unique objects. The model twines used in trawls provide an almost transparent target, yet the ULS-500 did an excellent job capturing data which would otherwise take a great deal of time to acquire.”

 
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