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Marine Electronics


October 2011 Issue

NOAA Multibeam Sonar Detects Deep-Sea Gas Seeps
Multibeam sonar has successfully been used to map and detect gaseous seeps in the water column, said scientists testing the technology on board NOAA Ship Okeanos Explorer in the Gulf of Mexico. During an August cruise, the ship's multibeam system produced data to make high-resolution maps of gas in the water column in depths ranging from 1,000 to 2,500 meters.

As the gulf contains numerous gaseous seeps, data collected by multibeam sonar could prove valuable to researchers planning further studies of gas seeps and their effects on the marine environment, NOAA said. The objective of the August expedition was to test the sonar's ability to map gaseous seeps, not oil, as oil is more difficult to acoustically detect with the multibeam sonar.

Okeanos Explorer's multibeam sonar first displayed its ability to acoustically map the water column during NOAA testing off the U.S. West Coast in 2009. It mapped a plume of suspected methane gas that rose 1,400 meters from the seafloor. The August expedition was the first comprehensive test of Okeanos Explorer's multibeam to detect deep gaseous seeps over a wide area. NOAA said its use during this mission may extend the agency's water-column mapping capabilities.

Single-beam sonar systems have been used extensively to map gas seeps but do not provide as much coverage as typically collected by multibeam systems. Since multibeam sonar obtains information from a wide fan-shape of beams, it maps a wider area more quickly and efficiently. The multibeam sonar on Okeanos Explorer is one of the few that is specially configured to collect water-column data to characterize gaseous seeps in wide areas of the deep ocean's water column in high resolution. For more information, visit www.noaanews.noaa.gov.

USSI Demonstrates Fiber-Optic Intruder Detection System
Two fiber-optic sonar arrays from Los Angeles, California-based US Seismic Systems Inc. (USSI) installed on the bottom of Lake Erie positively detected 100 percent of the intrusion attempts at ranges up to four kilometers during an August demonstration, the company announced.

The USSI underwater harbor security system was installed at a test site under a contract with Pennsylvania State University's Electro Optic Center. Naval Surface Warfare Center, Crane, sponsored the contract.

USSI said its system demonstrated the feasibility of using a low-cost fiber-optic underwater sonar array to provide automated tripwire and alarms in a harbor environment without operator intervention. It had similar results in May during testing of the system in Mission Bay in San Diego, California.

The sonar arrays were part of a much larger integrated harbor security system called Harbor Sentinel, which includes surface search radar, thermal-imaging cameras and automated identification system ship-tracking information. For more information, visit www.ussensorsystems.com.

Applus RTD Introduces Two Nondestructive Testing Systems
Applus RTD (Rivium, Netherlands) released in September two technologies, the RTD RAYSCAN and Inverse Wave field Extrapolation (IWEX 3D), which are designed to locate flaws in pipelines, oil and gas platforms, and other crucial pieces of infrastructure.

RTD RAYSCAN, able to measure two- to 12-inch-diameter pipes, is an advanced digital radiography system primarily designed for pipeline inspection work, suitable for the inspection of girth welds on- and offshore, particularly in new construction projects. IWEX 3D is used for ultrasonic testing. It uses a small, collimated X-ray beam, short exposure and lower energy levels than conventional techniques, and its full lead shielding greatly reduces radiation hazards, Applus said.

IWEX 3D can reconstruct 2D cross-sections of an object shown in real time, rather than presenting the measured signals in an abstract format. It shows interaction of the ultrasound beams with the object, rather than only the object itself. The result provides clearer data than traditional ultrasonic testing techniques, increasing accuracy in both sizing and positioning of the defect, the company said. These cross-sections can be combined to create a 3D image of the object and to detect potential defects. For more information, visit www.applusrtd.com.

Automated Fish Counting System Deployed in Washington River
BioSonics Inc. (Seattle, Washington) has successfully deployed an automated salmon-counting system utilizing its DT-X echosounder on a remote stretch of the Quinault River in Grays Harbor County, Washington, the company said in August.

In 2010, BioSonics was contracted by the Quinault Indian Nation to study the feasibility of establishing a real-time fish-counting station. Harvest managers wanted a timely and precise index of salmon counts to properly manage their fisheries resources, which led BioSonics to select a site on a lower section of the river.

The fish-counting system, deployed in May for several months, consists of a 120-kilohertz split-beam transducer and an ROS PT 25 rotator mounted to an adjustable-track trolley system. The track was gravity-mounted with cement pier blocks for minimal bank disturbance and easy demobilization.

The salmon-counter's surface electronics consist of a BioSonics DT-X echosounder, which allows for the detection, sizing and 3D tracking of targets at ranges in excess of 200 meters, and a control computer. Both are housed in a mobile office trailer with a satellite modem for communication. BioSonics' data-processing software automatically generate fish tracks and create fish count reports, which are transmitted to a website.

For a power source, two heavy-duty trailers were configured, each with a bank of deep cycle batteries and an integrated inverter/charger. By rotating the trailers every three to four days for recharging, the fish-counting system could be powered with relatively little effort and at low cost, BioSonics said.

"This pilot stage deployment was monumental," BioSonics President Tim Acker said. "To our knowledge, there is nothing else like this in the world. Completely autonomous, completely automatic fish counting represents a shift in the way fisheries managers work. Imagine sitting at your desk and receiving a fish count report from an unmanned monitoring station twenty miles away."

For more information, visit www.biosonicsinc.com.


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