Copyright (c) 2013 University of Rhode Island All rights reserved. http://digitalcommons.uri.edu/gsofacpubs Recent documents in Graduate School of Oceanography Faculty & Scientist Publications en-us Wed, 24 Apr 2013 12:38:52 PDT 3600 http://digitalcommons.uri.edu/gsofacpubs/25 http://digitalcommons.uri.edu/gsofacpubs/25 Mon, 14 Jan 2013 11:25:14 PST Practical autonomous robotic vehicles require dependable methods for accurately identifying course or roadway boundaries. The authors have developed a method to reliably extract the boundary line using simple dynamic thresholding, noise filtering, and blob removal. This article describes their efforts to apply this procedure in developing an autonomous vehicle.

]]> Chris Roman et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/24 http://digitalcommons.uri.edu/gsofacpubs/24 Fri, 04 Jan 2013 11:22:19 PST Marine archaeology beyond the capabilities of scuba divers is a technologically enabled field. The tool suite includes ship-based systems such as towed side-scan sonars and remotely operated vehicles, and more recently free-swimming autonomous underwater vehicles (AUVs). Each of these platforms has various imaging and mapping capabilities appropriate for specific scales and tasks. Broadly speaking, AUVs are becoming effective tools for locating, identifying, and surveying archaeological sites. This paper discusses the role of AUVs in this suite of tools, outlines some specific design criteria necessary to maximize their utility in the field, and presents directions for future developments. Results are presented for a recent joint AUV–towed system survey and a demonstration of current mine-hunting technologies applied to archaeology.

]]> Christopher N. Roman et al. History Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/23 http://digitalcommons.uri.edu/gsofacpubs/23 Fri, 04 Jan 2013 10:27:52 PST This paper presents an overview and initial testing results for a shallow water Lagrangian float designed to operate in coastal settings. The presented effort addresses the two main characteristics of the shallow coastal environment that preclude the direct of use of many successfully deep water floats, namely the higher variation of water densities near the coast compared with the open ocean and the highly varied bathymetry. Our idea is to develop a high capacity dynamic auto-ballasting system that is able to compensate for the expected seawater density variation over a broad range of water temperatures and salinities while using measurements of both pressure and altitude above the bottom. The major components of the float consist of a Netburner micro processor, rechargeable lithium ion battery system, piston style volume changing mechanism, sensors for pressure and altitude, and a safely system for recovery and emergency conditions. Results are presented for field tests that verify the performance of the float for a variety of behaviors that are of general utility for both water tracking an profile sampling.

]]> Alex Schwithal et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/22 http://digitalcommons.uri.edu/gsofacpubs/22 Thu, 03 Jan 2013 13:05:47 PST The Arctic seafloor remains one of the last unexplored areas on Earth. Exploration of this unique environment using standard remotely operated oceanographic tools has been obstructed by the dense Arctic ice cover. In the summer of 2007 the Arctic Gakkel Vents Expedition (AGAVE) was conducted with the express intention of understanding aspects of the marine biology, chemistry and geology associated with hydrothermal venting on the section of the mid-ocean ridge known as the Gakkel Ridge. Unlike previous research expeditions to the Arctic the focus was on high resolution imaging and sampling of the deep seafloor. To accomplish our goals we designed two new Autonomous Underwater Vehicles (AUVs) named Jaguar and Puma, which performed a total of nine dives at depths of up to 4062m. These AUVs were used in combination with a towed vehicle and a conventional CTD (conductivity, temperature and depth) program to characterize the seafloor. This paper describes the design decisions and operational changes required to ensure useful service, and facilitate deployment, operation, and recovery in the unique Arctic environment.

]]> Clayton Kunz et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/21 http://digitalcommons.uri.edu/gsofacpubs/21 Wed, 02 Jan 2013 06:38:05 PST There is a persistent need for high resolution photographic and bathymetric maps of the sea floor for many research areas in marine geology, biology and archaeology. This poster will present recent work using high frequency multibeam sonars, stereo vision and structured light laser imaging techniques to create maps with centimeter resolution for these applications. This research involves the development of new image and sonar processing techniques that combat the typical difficulties of imperfect navigation information, limited sensor ranges and adverse environmental conditions associated with using marine robotic vehicles in the ocean. Data for this work has been collected with the Hercules remotely operated vehicle (ROV), which is part of the Nautilus ocean exploration program, and with our newly developed Lagrangian imaging float. The 2010 Nautilus expedition involved more than 80 technical and scientific collaborators from around the world working for four months at archaeogical and geological sites in the Aegean and Mediterranean Seas. Our new Lagrangian float is novel platform that provides high quality sea floor images with significantly less effort and cost than other current methods. The presented results will show direct comparisons between our visual and acoustic sensing modalities, an in-situ calibration procedure for structured light laser imaging, and the visual data products that can be produced by the Lagrangian float.

]]> Gabrielle Inglis et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/20 http://digitalcommons.uri.edu/gsofacpubs/20 Wed, 02 Jan 2013 06:30:37 PST Grain size characteristics of pyroclastic deposits provide valuable information about source eruption energetics and depositional processes. Maximum size and sorting are often used to discriminate between fallout and sediment gravity flow processes during explosive eruptions. In the submarine environment the collection of such data in thick pyroclastic sequences is extremely challenging and potentially time consuming. A method has been developed to extract grain size information from stereo images collected by a remotely operated vehicle (ROV). In the summer of 2010 the ROV Hercules collected a suite of stereo images from a thick pumice sequence in the caldera walls of Kolumbo submarine volcano located about seven kilometers off the coast of Santorini, Greece. The highly stratified, pumice-rich deposit was likely created by the last explosive eruption of the volcano that took place in 1650 AD. Each image was taken from a distance of only a few meters from the outcrop in order to capture the outlines of individual clasts with relatively high resolution. Mosaics of individual images taken as the ROV transected approximately 150 meters of vertical outcrop were used to create large-scale vertical stratigraphic columns that proved useful for overall documentation of the eruption sequence and intracaldera correlations of distinct tephra units. Initial image processing techniques, including morphological operations, edge detection, shape and size estimation were implemented in MatLab and applied to a subset of individual images of the mosiacs. A large variety of algorithms were tested in order to best discriminate the outlines of individual pumices. This proved to be challenging owing to the close packing and overlapping of individual pumices. Preliminary success was achieved in discriminating the outlines of the large particles and measurements were carried out on the largest clasts present at different stratigraphic levels. In addition, semi-quantitative analysis of the size distribution could also be determined for individual images. Although a complete size distribution is not possible with this technique, information about the relative distribution of large and medium size clasts is likely to provide a reasonable proxy for the overall sorting of submarine deposits. Our preliminary work represents the first attempt to carry out an in situ granulometric analysis of a thick submarine pyroclastic sequence. This general technique is likely to be valuable in future studies of submarine explosive volcanism given the recent discoveries of extensive pumiceous deposits in many submarine calderas associated with subduction zone environments. AGU session number OS13A-1501

]]> Clara Smart et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/19 http://digitalcommons.uri.edu/gsofacpubs/19 Wed, 02 Jan 2013 06:08:56 PST Efficiently identifying and localizing diffuse sea floor venting at hydrothermal and cold seep sites is often difficult. Actively venting fluids are usually identified by a temperature induced optical shimmering seen during direct visual inspections or in video data collected by vehicles working close to the sea floor. Relying on such direct methods complicates establishing spatial relations between areas within a survey covering a broad area. Our recent work with a structured light laser system has shown that venting can also be detected in the image data in an automated fashion. A structured light laser system consists of a camera and sheet laser projected at the sea floor. The camera and laser are fixed to a rigid calibrated mount such that the optical axis of the camera and the laser plane intersect at some distance away from the camera, typically 2 to 5 meters. The position of the laser line, visible on the sea floor in the image, can be extracted using standard computer vision techniques (Fig. 1) and used to determine the height of the bottom along the laser line. By collecting images in a survey pattern at a high frame rate, typically 20 to 30 Hz, a bathymetric map can be produced using the individual profiles. In the presence of venting, temperature anomalies refract the laser sheet such that it does not project a crisp and clear line on the sea floor. The laser will instead appear blurred and visible over a larger section of the image. By processing the images to segment out clear laser lines from refracted lines it is possible to identify areas of venting. Our initial approach uses calculated image moments relative to the peak intensity level detected in each column of the image matrix. In the presence of venting the calculated moments differ from those of the undistorted laser shining on the sea floor. Test results from the Kolumbo submarine volcano near Santorini, Greece demonstrate this approach and show the utility of the method for survey work. Test images over active vents are compared to typical sea floor images, allowing for allowing areas of venting to be identified from sequences of images taken during a standard grid survey over the vent field. The use of structured light laser image offers potential for broad area vehicle surveys. The method would also complement direct visual surveys and other acoustic coherence methods that are used to identify the location of fluid flow. AGU session number OS11B-1473.

]]> Gabrielle Inglis et al. Oceanography Engineering http://digitalcommons.uri.edu/gsofacpubs/18 http://digitalcommons.uri.edu/gsofacpubs/18 Wed, 02 Jan 2013 06:01:23 PST This poster reports on the August 2007 Black Sea Expedition of the Institute for Archaeological Oceanography at the University of Rhode Island (IAO) and the Institute for Exploration (IFE), in collaboration with the Department of the Underwater Heritage of Ukraine. This year’s work marks a new phase in a multi-year (2000–2012) archaeological and oceanographic survey of the Black Sea. 2007 fieldwork focuses on two Byzantine shipwrecks. The 10th century C.E. shipwreck Chersonesos A (discovered in 2006) lies at 140 m depth in the suboxic zone off the Crimean peninsula. The ship carried a cargo of one-handled jars of a widely distributed but sparsely documented local type. The sixth century C.E. shipwreck Sinop D (discovered in 2000) lies at 325 m depth off Sinop, Turkey, in the anoxic zone, and also carried a locally-made amphora type. Sinop D is the best-preserved ancient ship yet discovered in the deep sea, and non-intrusive examination of the hull yields unique information about ancient ship construction and local patterns of technological exchange. Our initial studies focus on environmental characterization and the deepwater implementation of long-term site monitoring, decay rate testing, and sediment analyses, to develop management plans for each shipwreck. Cross-site comparisons address deepwater preservation under differing levels of oxygen depletion. We conclude with an assessment of our ability to record, excavate, monitor, and conserve deepwater sites as underwater museums using remote operated vehicle (ROV) deployed technology.

]]> Bridget Buxton et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/17 http://digitalcommons.uri.edu/gsofacpubs/17 Fri, 21 Dec 2012 12:45:41 PST Michael L. Brennan et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/16 http://digitalcommons.uri.edu/gsofacpubs/16 Fri, 21 Dec 2012 12:36:38 PST Michael L. Brennan et al. Oceanography http://digitalcommons.uri.edu/gsofacpubs/15 http://digitalcommons.uri.edu/gsofacpubs/15 Fri, 21 Dec 2012 12:27:12 PST Timothy M. Shank et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/14 http://digitalcommons.uri.edu/gsofacpubs/14 Fri, 21 Dec 2012 12:19:30 PST Steven Carey et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/13 http://digitalcommons.uri.edu/gsofacpubs/13 Fri, 21 Dec 2012 12:06:22 PST Christopher N. Roman et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/12 http://digitalcommons.uri.edu/gsofacpubs/12 Fri, 21 Dec 2012 11:25:08 PST Steven N. Carey et al. Oceanography http://digitalcommons.uri.edu/gsofacpubs/11 http://digitalcommons.uri.edu/gsofacpubs/11 Fri, 21 Dec 2012 11:25:06 PST Chris Roman et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/10 http://digitalcommons.uri.edu/gsofacpubs/10 Fri, 21 Dec 2012 10:04:54 PST Katherine L. C. Bell et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/9 http://digitalcommons.uri.edu/gsofacpubs/9 Fri, 21 Dec 2012 09:17:56 PST Michael L. Brennan et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/8 http://digitalcommons.uri.edu/gsofacpubs/8 Thu, 20 Dec 2012 13:13:36 PST There is a persistent need in the oceanographic community for accurate three dimensional reconstructions of seafloor structures. To meet this need underwater mapping techniques have expanded to include the use of stereo vision and high frequency multibeam sonar for mapping scenes 10's to 100's of square meters in size. Both techniques have relative advantages and disadvantages that depend on the task at hand and the desired accuracy. In this paper, we develop a method to constrain the often problematic stereo correspondence search to small sections of the image that correspond to estimated ranges along the epipolar lines calculated from coregistered multibeam sonar micro-bathymetry. This approach can be applied to both sparse feature based and dense area-based stereo correspondence techniques. Data were collected on an underwater vehicle survey using a calibrated stereo rig and a multibeam sonar gathering coincident datasets. Overall, the constrained correspondence method shows improvements in the number and reliability of correct matches and allows for reduction in complexity of feature descriptors but it is heavily reliant on the quality of the intrinsic and extrinsic calibration of the camera and sonar systems.

]]> Gabrielle Inglis et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/7 http://digitalcommons.uri.edu/gsofacpubs/7 Thu, 20 Dec 2012 12:56:07 PST This paper presents results from recent work using structured light laser profile imaging to create high resolution bathymetric maps of underwater archaeological sites. Documenting the texture and structure of submerged sites is a difficult task and many applicable acoustic and photographic mapping techniques have recently emerged. This effort was completed to evaluate laser profile imaging in comparison to stereo imaging and high frequency multibeam mapping. A ROV mounted camera and inclined 532 nm sheet laser were used to create profiles of the bottom that were then merged into maps using platform navigation data. These initial results show very promising resolution in comparison to multibeam and stereo reconstructions, particularly in low contrast scenes. At the test sites shown here there were no significant complications related to scattering or attenuation of the laser sheet by the water. The resulting terrain was gridded at 0.25 cm and shows overall centimeter level definition. The largest source of error was related to the calibration of the laser and camera geometry. Results from three small areas show the highest resolution 3D models of a submerged archaeological site to date and demonstrate that laser imaging will be a viable method for accurate three dimensional site mapping and documentation.

]]> Chris Roman et al. Engineering Oceanography http://digitalcommons.uri.edu/gsofacpubs/6 http://digitalcommons.uri.edu/gsofacpubs/6 Tue, 18 Dec 2012 11:52:35 PST A number of marine biological, geological, and archaeological applications share the need for high-resolution optical and acoustic imaging of the sea floor [Ballard et al., 2002; Greene et al., 2000; Shank et al., 2002]. In particular,there is a compelling need to conduct studies in depths beyond those considered reasonable for divers (∼50 m) down to depths at the shelf edge and continental slope (∼1000–2000 m). Some of the constraints associated with such work include the requirement to work off of small coastal vessels or fishing boats of opportunity,and the requirement for the vehicle components to be air-shippable to enable inexpensive deployments at far-flung oceanographic sites of interest.

]]> Hanumant Singh et al. Oceanography