Nation Sun Yat-sen University, Institute of Under Sea Technology has sidescan equipment. The sidescan¡¦s graphic recorder uses thermal printer to record reflection data. Although thermal printer is convenient, it is difficult to archive and analyze data. Sidescan manufacturer also provide digital display and data storage equipments, but those equipments are expensive, and does not support development tools. It is not suitable for further research and development of sidescan sonar image processing algorithm. For this reason, we develop own sidescan digital image acquisition system. The new sidescan digital image collection system can provide sidescan digital image data, GPS data (include Longitude, Latitude, and GMT). Research methodology¡G (1) Measure sidescan¡¦s analog signal output characteristics. (2) Develop controlling programs to collect digital image data from general purpose ADC (Analog to Digital Converter) Card. (3) Test in Laboratory and under the sea This sidescan equipment can display and store digital data in real time, and more functions like switch scan automatic, etc now. The digit data include right side 1024 sample points, left side 1024 sample points, GPS data (include Longitude, Latitude, and GMT).

In the world over, the mainstream method of investigating coral reefs is conducted by scuba diving. Take the domestic physical examination of coral reefs for example, divers use the basic ¡§transect¡¨ method to estimate the coverage rate of coral reefs and to identify characteristics of the seabed environment. In addition, amount of specific fishes and invertebrates were recorded to gauge the influence of human activities exercised on coral reefs. Because the transect method can facilitate full and accurate investigation into the coral reefs in the surveyed area, it has been widely adopted by relevant domestic and international organizations for many years. However, in respect to charting out the area of coral reefs, scuba diving reveals some technological drawbacks, such as slower in investigation speed and lack of accurate positioning system. Also, this method imposes dangers on divers. One way to improve these deficiencies is by the application of sidescan sonar system, which renders investigation more speedy and positioning more accurate. This research attempted to use sidescan sonar technology to survey the coral reefs at two sites, i.e. the area of the Third Nuclear Power Plant and offshore area near Tiaoshi (the total surveyed area was about 0.94km2). In addition, optical images of the seabed, collected by a towed operated vehicle, were used to groundtruth the sonar imagery. As for investigation speed, an underwater terrain of 3,600m2 could be surveyed by the sidescan sonar system per minute, with scan range setting at 30m and ship speed of 2 knots. To enhance positioning accuracy of the sonar imagery, a DGPS was incorporated to the sidescan sonar system. The precision of the geocoded sonar imagery was within 5m. The major steps in this research were¡G 1. The surveyed seabed was classified into rocky and sandy seabeds based on the characteristics of sonographs. Furthermore, the geographic distributions of these seabeds were mapped. 2. Sonographs characteristics were groundtruthed by optical images. 3. By the specific characteristics of sonograph, the rocky seabed could be further classified into three subcategories, i.e. rocky seabed with high density, middle density, and low density of reef organisms. 4. The distribution of each type of seabed was further verified with optical images. 5. The method of applying sonographes to chart out conditions and distributions of coral reefs area was established. The feasibility of this acoustical method was then estimated. The results of this investigation included¡G 1. the site near the outfall of the Third Nuclear Power Plant The major seabed of this site was rocky seabed covered by reef organisms of middle density. The area of this kind of seabed was 228,617m2, with most of it located at depth shallower than 5m. The surveyed rocky seabed covered by reef organisms of high density was 125,838m2, with most of it located near Houbihu(shallower than 10m) and off Leidashi area. 2. the site near Tiaoshi The major seabed of this site was rocky seabed covered by reef organisms of high density. The area of this kind of seabed was 183,325m2. Most of this kind of seabed was located off Tiaoshi at depth shallower than 7m and also stretched between Tantzewan and Shiniuzai at depth shallower than 8m. The results of this research illustrated that sidescan sonar system is considerably effective in mapping the distribution of coral reefs and in estimating living conditions of the reef organisms.

Abstract The purpose of this study was to integrate the principle of marine geotechnical engineering, underwater acoustic and optical observation techniques into studying the distribution of seafloor sediments and engineering stability of artificial reefs off Yung-an Harbor, Kaohsiung Country, south-western part of Taiwan. The reefs were deployed to the testing site in November, 1996. The goal of this study was intended to describe the situation of reefs site and confirm whether reefs were moved and buried or not; as well as, to predict whether reefs should be deployed again in the future. Long-term monitoring of underwater targets was conducted by using of side-scan sonar system, echo sounder, sub-bottom profiler, and underwater camera. The utility of side-scan system was to depict the topography and terrain features of seabed. The other equipments were used to complement and prove the results of side-scan sonar observations. In this study was estimated by Morison¡¦s equation wave force against reef, calculate the scouring depth by Silvester¡¦s experience equation (1974), and figure out the settlement of reefs by Das¡¦s theoretical equation (1990). The topography of Yung-an reef site is generally gentle and terrain features is monotonous. The Most textures of surficial sediments in this site were sandy silt and some gravel was distributed at south of site. According to result, sandy silt layer is above gravel layer, and the height of sandy silt layer was decreased progressively from the North to the South. The largest height of sandy silt was in set-A(about 2 meters), second one was in set-B(about 1 meters), and set-C was covered by boulder rock and gavel. Typhoon was the major factor which causes movement and overturning of reefs. Based on theoretical analysis and long term in-situ observations on a testing site, original heaped reef was overturned among the investigated period, and there were no obvious movement and settlement status for non-heaped reefs. Besides, the relationships between reefs and seafloor sediment were arrived dynamic balance after six years. According to difference site, the total depression of reefs was estimated to be 0 to 2 meters, and no any reef was buried. To sum up, there was no reefs had been buried and moved in set-A, set-B, and set-C on the Yung-an reef site. Furthermore, due to the ability of gathering fishes of artificial reefs, some fish groups surround with reefs. Consequently, in the view of engineering, Yung-an reef site was a suitable site for deploying reefs.

Underwater stationary targets are objects under the water that can¡¦t move autonomously. Apparatus feasible for detecting underwater stationary targets includes: optics, acoustics and geophysical instruments. The objective of this study was to investigate engineering characteristics of the battleship reef and other reefs deployed off Hai-Kou, Ping-Dong County, by the application of an integrated underwater surveying system. A total of four surveys were conducted. i.e., the 14th of April 2004, the 20th of July 2006, the 3rd of Mar. 2007 and the 30th of Oct. 2007. The investigation were completed using primarily the sidescan soner, along with other auxiliaries such as magnetometer and single beam echo sounder. Based on a mutual consideration of the results of the first survey in April 2004, the battleship on the seafloor was identified as Jong-Rong battleship. The battleship was sitting on the seabed in an upright condition at depths of 32 to 42m below the sea surface. A chain cable was catenated from the stern of the battleship down to the seabed. In addition, a large number of cubic artificial reefs were spreaded around. A comparision of results obtained during the first and the third survey indicated that the battleship was undergone a displacement of 250m. The significant displacement of the battleship was correlated with a medium magnitude typhoon passed by on the 3rd of Dec. 2004 and the 17th of May 2006 (i.e., Nanmadol and Chanchu Typhoon). The second and the third survey indicated that the battleship was¡¦t moved by earthquake on the 26th of Dec. 2006 (i.e., Herng Chuen earthquake)with magnitude of seven. A comparison of the third and the fourth surveys suggested that the battleship¡¦s bow was moved to the north for an extra 20m. This movement is correlated with a typhoon passed by in Aug. 2007(i.e., Pabuk Typhoon). However, a detailed investigation of the sonographs indicated that there are very limited relative displacement between the battleship and cement artificial reefs that scattered around the battleship. Therefore, further investigations are needed to verify this tautative conclusion. Based on sidescan soner imagery collected in four surveys between 2004 and 2007. the location of various type of artifical reefs at Hai-Kou artifical reef site were investigated. Except the battleship reef, all the orther types of reefs which include steel reef, electric-pole reef and cement reef were not displaced by either typhoon or earthquake. Under the influence of typhoon waves, the battleship reef was displaced for a distance of 250m.

No description available.

Automatic target recognition capabilities in autonomous underwater vehicles has been a daunting task, largely due to the noisy nature of sonar imagery and due to the lack of publicly available sonar data. Machine learning techniques have made great strides in tackling this feat, although not much research has been done regarding deep learning techniques for side-scan sonar imagery. Here, a state-of-the-art deep learning object detection method is adapted for side-scan sonar imagery, with results supporting a simple yet robust method to detect objects/anomalies along the seabed. A systematic procedure was employed in transfer learning a pre-trained convolutional neural network in order to learn the pixel-intensity based features of seafloor anomalies in sonar images. Using this process, newly trained convolutional neural network models were produced using relatively small training datasets and tested to show reasonably accurate anomaly detection and classification with little to no false alarms. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

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Identifying the location of sunken logs is a task of considerable interest in today?s world economy. The main motive of this work is to find and locate sunken cypress logs that were lost during the transit to a lumber mills. Underwater logging is possible because of the fact that many of the logs were barely affected by the decades of submersion. Cypress logs, the types of logs used in this research have a natural resistant to rotting. The other probability for the logs not being affected significantly, even staying in water for decades, is the high density of the growth rings. The quality of these sunken logs is far superior because of their high density in growth rings and they have a high economic value compared to present day logs. Sidescan sonar is proposed for the work of locating the sunken logs. Based on various research and studies, which involve several similar projects, sidescan sonar is proposed to locate and identify these sunken targets. These images that resemble a cylinder in some aspects can then be compared with a template for pattern matching. Any image size that is not matched with the acceptable size can be rejected. Using this template matching procedure, the size of the object is matched and the logs can be located and recovered. Based on various technical papers and studies involving similar projects, conclusions were drawn and future work has been suggested.

Sidescan Sonar has been the most popular probe for sea floor detecting in the underwater engineering. It is not only use to map the topography of the sea floor but also apply to the underwater search and rescue. Sidescan Sonar relies on commercial software, e.g. SonarPro, to record the raw data and draw images of the sea floor. However, SonarPro only presents the data to display segmental images, but it can not illustrate all images of the sea floor in one drawing. Researchers need to use the other software, called WizMap, to mosaic all Sidescan images in one drawing. WizMap is powerful for analyzing Sidescan data, but it is costly and has never been published its technology of Sidescan mosaic images. Thus we can not understand how Wizmap analysis raw data and make a mosaic drawing. Moreover, we could only accept the results it made, even the mosaic drawing is not correct. In this study, we implement a new analysis software package to facilitate reading raw data and drawing mosaic images of Sidescan Sonar. Sidescan Sonar provides basic function to record all digital raw data including GPS position, heading, roll, pitch, etc. We transfer the ship and Sidescan location from GPS to TM2 coordinate and illustrate the two side images along Sidescan trace in the same drawing. We will review the drawing and check all characteristics of these images and then adjust the heading offset and location offset to fit a better mosaic drawing. Finally, we combine all images into one mosaic drawing and compare two drawings between WizMap mosaic image and our mosaic drawing for confirming all results.

Sedimentation rates in sediment cores from Lavaca Bay have been high within the last 1-2 decays within the central portion of the bay, with small fluctuations from river input. Lavaca Bay is a broad, flat, and shallow (<3 m) microtidal estuary within the upper Matagorda Bay system. Marine derived sediment enters the system from Matagorda Bay, while two major rivers (Lavaca & Navidad) supply the majority of terrestrially derived sediment. With continuous sediment supply the bay showed no bathymetric change until the introduction of the shipping channel. Processes that potentially lead to sediment transport and resuspension within the bay include wind driven wave resuspension, storm surges, wind driven blowouts, and river flooding. These processes were assessed using X-radiographs, grain size profiles, and 210Pb and 137Cs geochronology of sediment diver cores. In six cores the upper 10 cm of the seabed has been physically mixed, where as the rest showed a continuous sediment accumulation rate between 0.84-1.22 cm/yr. Sidescan sonar and subbottom chirp sonar data coupled with sedimentological core and grab samples were used to map the location and delineate the sedimentary facies within the estuarine system in depths >1 m. Five sedimentary facies were identified in Lavaca Bay and adjacent bays, they are: 1) estuarine mud; 2) fluvial sand; 3) beach sand; 4) bay mouth sand; and 5) oyster biofacies. Of the five facies, Lavaca Bay consists primarily of estuarine mud (68%). Pre-Hurricane and post-Hurricane Claudette cores were obtained to observe the impact to the sedimentary processes. The north and south Lavaca Bay were eroded by 10 cm and 2-3 cm, respectively. Cox Bay and Keller Bay saw a net deposition of 2-3 cm.