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.

No description available.

No description available.

No description available.

With the Global War on Terrorism (GWOT) taking place in full force, autonomous vehicles have become a major asset to government forces. Expansion of single vehicle technology to multiple vehicle technology is required in order for the United States to stay ahead of its adversaries in the GWOT and other technological fields (such as oceanography). Multiple vehicle technology has been explored by many different institutions in the recent past (Leonard, 2001 and Kucik, 2003). Expansion of this technology will lead to greater autonomy and robustness amongst the vehicles. This thesis presents a simulation of a "follow the leader" behavior for multiple Autonomous Underwater Vehicles (AUVs). The follower vehicle incorporates the use of forward-looking sonar to track the leader vehicle. This process will free up bandwidth between acoustic modems; allowing data transfer to occur with greater efficiency. Hydrodynamic coefficients are used to develop steering equations that model REMUS through a track of specified waypoints similar to a real-world mission track. A two-dimensional forward looking sonar model with a 120 [degree] horizontal scan and a 110 meter radial range is modeled to track the leader vehicle. Resulting bearing and range between the two vehicles is incorporated as control for positioning the follower vehicle.

One day fully autonomous AUV's will no longer require human interactions to complete its missions. To make this a reality, the AUV must be able to safely navigate in unfamiliar environments with unknown obstacles. This thesis builds on previous work conducted at NPS's Center for AUV Research to improve the autonomy of the REMUS class of AUVs with an implemented FLS. The first part of this thesis deals with accurate path following with the use of look-ahead pitch calculations. With the use of a SIMULINK model, constraints surrounding obstacle avoidance path planning are then explored, focusing on optimal sensor orientation issues. Two path planning methods are developed to address the issues of a limited sonar field of view and uncertainties brought on by an occlusion area. The first approach utilizes a pop-up maneuver to increase the field of view and minimize the occlusion area, while the second approach creates a path with the addition of a spline. Comparing the two methods, it was concluded that spline addition planner provided a robust optimal obstacle avoidance path and along with the look-ahead pitch controller completes the design of a "back-seat driver" to improve REMUS's survivability in an unknown environment. / US Navy (USN) author.

Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores (Major Automação). Faculdade de Engenharia. Universidade do Porto. 2009

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.