Sonar Scanner Provides Complete Picture

APRIL/MAY 2007 VOLUME 1, NUMBER 1

Sonar Scanner Provides Complete Picture

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What is Sonar?Sonar stands for SOund NAvigation and Ranging. Sonar instruments can be passive or active. Passive sonar reacts to sounds in the ocean, like underwater explosions, earthquakes, volcanic eruptions, sounds produced by fish and other animals or ships. Active sonar sends sound waves toward objects, then records what the sounds are like when they come back to the instrument. Objects in the ocean can transmit, absorb and reflect sound waves. Density affects sound speed, and sound speed is slower in fresh water than in sea water. There are many kinds of sonar, each developed for a different task. For example in side scan sonar, the sonar device is attached to the hull of a ship or towed behind a ship and emits fan-shaped pulses down toward the seafloor. Side scan sonar is used for such things as mapping the ocean floor, searching for sunken ships and inspecting undersea pipelines and cables. The study of underwater sound is called hydroacoustics.

chool buses cross bridges every day. But how do we know when a bridge is no longer safe? How would anyone know if the foundation of a bridge were cracking underwater?

The maintenance of bridges and roads falls under the responsibility of state or federal departments of transportation. In the spring of 2006, the Michigan Department of Transportation (DOT) hired professional diver and MTS member Brian Abbott and his company, Nautilus Marine Group, to perform an inspection of the Independence and Liberty Bridges in Bay City.

Using a team of four divers, Abbott examined the bridges using both surface supplied air diving and underwater acoustic imaging. A color camera was mounted on one diver’s helmet, but there was so much sediment suspended in the river that the pictures were of little use. The divers countered the poor visibility by performing tactile inspections of the piers.

Once the structural inspection was complete, Abbott used acoustic underwater imaging to determine any scour present on the river bed. Using a sonar scanner to take pictures

of the piers from various distances and angles, Abbott was able to create a complete picture of the river bed, identify debris around the piers and determine the effects of scouring (Picture 1). After creating a series of side view images from 360 degrees around the foundation, Abbott used Adobe Photoshop to combine them to produce an overhead picture of each pier (see Picture 2). Abbott is one of the first people in the world to use this technique to examine

an entire structure. Using surface-supplied air diving and this

new application of underwater imaging, Abbott was able to detect and detail the structural problems and deterioration of the Independence and Liberty Bridges. The Michigan DOT is preparing to repair the bridges. Thanks to

Brian Abbott prepares for the plunge.

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Career Corner

MTS Club News is a bimonthlypublication of theMarine Technology Societyand a member benefit of the MTS Club.

To join the MTS Club, visit the Web siteat www.mtsociety.org/youthclub.cfmor e-mail mtsprograms@erols.com.

Send address changesto mtsprograms@erols.com.

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innovative methods like Abbott’s, advanced marine technology plays an important role in ensuring the safety of people who cross that bridge.

The Marine Technology Society has both a Diving Committee and an Underwater Imaging Committee for our professional members. If you have questions about diving, please free to contact Diving Committee Chair Brian Abbott (abbottc@msu.edu). Or, if you have questions about underwater imaging, please contact UI Committee Chair Donna Kocak (dkocak@greenskyimaging.com).

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Diving into a Marine Technology Career

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Sonar Scanner

Underwater Acoustic Imaging is used to produce high-quality images in water where visibility is too poor to use optical methods. In underwater acoustic imaging, electrical energy (electricity) is sent to a crystal, which causes the crystal to vibrate. The sound of the vibration (mechanical energy) travels out into the water

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www.mtsociety.org/ youthclub.cfm

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nterested in making diving a part of your career in marine technology? There are a number of options available in commercial, research and military diving.

Brian Abbott is an example of a commercial diver. A civil engineer who is also an expert diver, he uses his skill set not only to inspect bridges and other structures, but also to perform navigational charting, channel maintenance, construction management, pipeline routing and archaeology.

Typically, engineering positions require a four-year degree in mechanical, structural, marine or ocean engineering. Phoenix International is a marine engineering company and an MTS member. According to the company’s Mechanical Engineering Manager Craig Kohler, diver certification and experience are not requirements for Phoenix’s engineers, but are certainly highly valued credentials. Kohler’s engineers develop and design underwater systems, tools and methods for performing offshore inspections. Kohler has found that experienced divers, having spent so much time in the water, are better equipped to understand the necessities of the job when designing systems.

Research diving is a field that generally requires an advanced degree in oceanography or another related discipline. Research divers are typically employed by academic institutions or

government agencies. Students who have received their master’s degrees often secure jobs as diving technicians at their academic institutions as they pursue their doctoral degrees. A research diver employed by an academic institution normally spends significant time teaching in the classroom as well as doing research in the field.

Military diving offers the privilege of serving your country while enjoying a career in diving and marine technology. There is a wide variety of specialties available to divers in the military. Navy divers perform underwater maintenance and repair of ships, salvage operations, surveying and research, deep submergence rescue, construction and explosive ordnance disposal.

Diving is a skill that can lead to a number of exciting career paths in marine technology.

Did you know?The minimum age to become a certified SCUBA

diver is 10 years old. If you are interested in training to become a certified diver, visit www.padi.com.

Here are a few fun and free things you can do online.

Learn about Woods Hole Oceanographic Institution (WHOI) expeditions that use deep-sea tools and vehicles. The current expedition is exploring the Arctic. Web link: www.divediscover.whoi.edu

California engineer Mark Fischer uses wavelets—a technique for rocessing digital signals—to transform the haunting calls of ocean mammals into movies that visually represent the songs and still images that look like electronic mandalas. Web link: www.aguasonic.com.

Check out live video and special content from the National Oceanic amd Atmospheric Administration’s (NOAA) National Marine Sanctuaries. Web link: www.oceanslive.org.

The Center for Ocean Science Education Excellence offers a “one-stop” Web site for ocean careers. Web link: www.oceancareers.com.

The California Ocean Communicators Alliance has launched a public awareness campaign to help Californians learn, experience and respect the oceans. Web link: www.ThankYouOcean.org

ORBITAL (Ocean Remote-sensing Base for Interactive Teaching And Learning) is an interactive Web site that shows how scientists use satellites to monitor the oceans. Web link: education.imars.usf.edu

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column until it hits an object and is reflected back to the crystal. After the energy returns to the crystal, a computer converts it to an image.

Surface Supplied Air Diving: Divers tethered to a surface-supplied-air diving system can achieve dives up to 190 feet of seawater (FSW) in air diving and 300 FSW in mixed gas diving. Air is supplied via an air compressor or high-pressure air flasks. A surface-supplied-air diving system can permit a diver to stay down for a longer period of time than a SCUBA system would allow.

Scour is the destructive effect that flowing water has on a submerged object. When a man made object such as a bridge pier, pipeline, cable, etc. is submerged in flowing water the local effect is to increase the current velocity around the object. This increased velocity has the tendency to remove or scour away the bottom material that supports the structure.

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+A cademic Arena

Are you on the Scholarship Bus?

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A researcher takes a core sample from brain coral. (Photo courtesy of Wolcott Henry.)

Send questions to the Club News editor at michael.hall@mtsociety.org to have them answered by a Marine Technology Society expert.

Marine Technology Society Expert TopicsAutonomous Underwater Vehicles (AUV)Buoy TechnologyCables & ConnectorsDynamic PositioningMarine EducationMarine SecurityMoorings

Ocean Economic Potential Ocean EnergyOcean ExplorationOcean PollutionOceanographic InstrumentationOffshore StructuresPhysical Oceanography/MeteorologyRemote SensingRopes & Tension MemberRemotely Operated Vehicles (ROV)Seafloor EngineeringUnderwater Imaging

ASK AN EXPERT

We are looking for promising high school seniors who are interested in studying marine technology next year. The Marine Technology Society offers thousands of dollars in scholarships to graduating high school seniors who have been accepted into a full-time undergraduate program.

Available scholarships include:

$2,000 MTS Student Scholarship for Graduating High School Seniors $2,000 Paros-Digiquartz Scholarship – open to graduate, undergraduate, and graduating

high school seniors interested in marine instrumentation Up to $10,000 ROV Scholarship – open to graduate, undergraduate and high school

seniors interested in Remotely Operated Vehicles (ROVs) or underwater work that furthers the work of ROVs

Take advantage of this opportunity to follow your dreams and launch your career in marine technology. The deadline to apply for MTS Scholarships is April 16, 2007. For more information and applications, visit the Education link on the MTS Web site:/www.mtsociety.org/education/student_scholarships.cfm

Check out the MTS Club Web page!

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