The sonar itself uses the sound velocity profile from our CTD casts in real time to adjust the data as we collect it. Thanks to technology, there are ways to solve this problem. Sound waves refract, too, and this refraction can cause some issues with our survey data. The bending of a wave is called refraction. From the training, I primarily learned that the most important policy is safety, which interestingly is emblazoned on the front of the ship just below the bridge. That orientation aligns with policies of NOAA and the expectation aboard Oregon II of its crew. Before I was allowed join the science party, I was required to complete an orientation.
Others, mostly those who are part of the science party, use the vessel for weeks at a time intermittently. Some call the ship “home” for extended periods of time such as most of the operational crew. The signs serve to direct and try to create consistency in the overall operation of the ship and the experience people have aboard it. Throughout the year, various individuals work and dwell on this vessel. At first, I was amused at the volume and redundancy, but then I realized that this ship is a communal space. Lamented signs and stickers can be found all over the ship. One of the most common fixtures throughout the vessel are posted signs. Looking around, I took many pictures of the various features with an eye on the architectural elements of the ship. I have never spent a significant amount of time on a trawling vessel or a research ship. When I first arrived aboard Oregon II, the new environment was striking. Today, sonar has evolved into more sophisticated forms of digital imaging multibeam technology and side scan sonar (see for more information). French physicist Paul Langévin constructed the first sonar set to detect submarines in 1915. During World War I, a need to detect submarines increased interest in sonar. In 1906, American naval architect Lewis Nixon invented the first sonar-like listening device to detect icebergs. The dark is either seaweed or other plant material or rocks. Sample scan from monitor in the computer lab. On some scans, we have found the surface of the sea floor to be generally sandy and suitable for trawling, but then on another scan with similar data results, chunks of coral and rock have impeded our trawls and damaged the net. Certainly, the side scanner is great for defining large items or structures on the sea floor, but in areas where the contour of the floor is more subtle, picking out distinctions on the monitor can be harder to discern. While EdgeTech praises the accuracy of its own technology, we have learned that accurate readings of data on the monitor can be more taxing. This means that the side scanner provides fast survey results, but the accuracy of the results becomes the challenge. While the imagining sent to our computer monitors have been mostly sand and rock, one researcher in our crew said he has seen tanks, washing machines, and other junk clearly on the monitors during other research cruises. The side scanner provides higher resolution imagery. From the manufacturer’s information, I have learned that it was designed for search and recovery and shallow water surveys. Having seen the side scanner used at a dozen different research stations on this cruise, I wanted to learn more about capabilities of this scientific instrument. Preparing to put the side scan over board. Scanners such as these have been useful on other NOAA and marine conservation research cruises especially working to map and assess reefs in the Gulf. This system was added as a precaution in advance of trawling due to the uneven nature of the Gulf floor off the Florida Coast, which is not as much of a problem the further west one goes in the Gulf. Using a scanner such as this for a groundfish survey in the Gulf by NOAA is not typical. Since it plays a major role in the scientific research we have completed, I wanted to focus on it a bit more in this blog. That probe is called the EdgeTech 4125 Side Scan Sonar. I also mentioned the use of a probe to scan the sea floor in advance of trawling for fish samples. In my previous blog, I mentioned the challenges of doing survey work on the eastern side of the Gulf near Florida. Geographic Area of Cruise: Gulf of Mexico Mission: Leg III of SEAMAP Summer Groundfish Survey
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