High-resolution underwater robotic vision-based mapping and three-dimensional reconstruction for archaeology

Documenting underwater archaeological sites is an extremely challenging problem. Sites covering large areas are particularly daunting for traditional techniques. In this paper, we present a novel approach to this problem using both an autonomous underwater vehicle (AUV) and a diver-controlled stereo imaging platform to document the submerged Bronze Age city at Pavlopetri, Greece. The result is a three-dimensional (3D) reconstruction covering 26,600 m2 at a resolution of 2 mm/pixel, the largest-scale underwater optical 3D map, at such a resolution, in the world to date. We discuss the advances necessary to achieve this result, including i) an approach to color correct large numbers of images at varying altitudes and over varying bottom types; ii) a large-scale bundle adjustment framework that is capable of handling upward of 400,000 stereo images; and iii) a novel approach to the registration and rapid documentation of an underwater excavations area that can quickly produce maps of site change. We present visual and quantitative comparisons to the authors' previous underwater mapping approaches

Intervention AUVs: The Next Challenge

While commercially available AUVs are routinely used in survey missions, a new set of applications exist which clearly demand intervention capabilities. The maintenance of: permanent underwater observatories, submerged oil wells, cabled sensor networks, pipes and the deployment and recovery of benthic stations are a few of them. These tasks are addressed nowadays using manned submersibles or work-class ROVs, equipped with teleoperated arms under human supervision. Although researchers have recently opened the door to future I-AUVs, a long path is still necessary to achieve autonomous underwater interventions. This paper reviews the evolution timeline in autonomous underwater intervention systems. Milestone projects in the state of the art are reviewed, highlighting their principal contributions to the field. To the best of the authors knowledge, only three vehicles have demonstrated some autonomous intervention capabilities so far: ALIVE, SAUVIM and GIRONA 500, being the last one the lightest one. In this paper GIRONA 500 I-AUV is presented and its software architecture discussed. Recent results in different scenarios are reported: 1) Valve turning and connector plugging/unplugging while docked to a subsea panel, 2) Free floating valve turning using learning by demonstration, and 3) Multipurpose free-floating object recovery. The paper ends discussing the lessons learned so far

DeepSurveyCam — A Deep Ocean Optical Mapping System

Underwater photogrammetry and in particular systematic visual surveys of the deep sea are by far less developed than similar techniques on land or in space. The main challenges are the rough conditions with extremely high pressure, the accessibility of target areas (container and ship deployment of robust sensors, then diving for hours to the ocean floor), and the limitations of localization technologies (no GPS). The absence of natural light complicates energy budget considerations for deep diving flash-equipped drones. Refraction effects influence geometric image formation considerations with respect to field of view and focus, while attenuation and scattering degrade the radiometric image quality and limit the effective visibility. As an improvement on the stated issues, we present an AUV-based optical system intended for autonomous visual mapping of large areas of the seafloor (square kilometers) in up to 6000 m water depth. We compare it to existing systems and discuss tradeoffs such as resolution vs. mapped area and show results from a recent deployment with 90,000 mapped square meters of deep ocean floor

Classification of underwater targets from autonomous underwater vehicle sampled bistatic acoustic scattered fields

One of the long term goals of autonomous underwater vehicle (AUV) minehunting is to have multiple inexpensive AUVs in a harbor autonomously classify hazards. Existing acoustic methods for target classification using AUV-based sensing, such as sidescan and synthetic aperture sonar, require an expensive payload on each outfitted vehicle and post-processing and/or image interpretation. A vehicle payload and machine learning classification methodology using bistatic angle dependence of target scattering amplitudes between a fixed acoustic source and target has been developed for onboard, fully autonomous classification with lower cost-per-vehicle. To achieve the high-quality, densely sampled three-dimensional (3D) bistatic scattering data required by this research, vehicle sampling behaviors and an acoustic payload for precision timed data acquisition with a 16 element nose array were demonstrated. 3D bistatic scattered field data were collected by an AUV around spherical and cylindrical targets insonified by a 7–9 kHz fixed source. The collected data were compared to simulated scattering models. Classification and confidence estimation were shown for the sphere versus cylinder case on the resulting real and simulated bistatic amplitude data. The final models were used for classification of simulated targets in real time in the LAMSS MOOS-IvP simulation package [M. Benjamin, H. Schmidt, P. Newman, and J. Leonard, J. Field Rob. 27, 834–875 (2010)]United States. Office of Naval Research (Grant N00014-14-1- 0214

Activity, Mud Migration, and Formation Mechanisms of Helgoland and Dvurechenskii Mud Volcanoes, Black Sea

The main motivations of this study was, to use the new near-to-seafloor remotely-operated instruments to obtain detailed information on the morphology, sedimentology and gas emissions of two neighboring mud volcanoes; the Dvurechenskii Mud Volcano (DMV) and the Helgoland Mud Volcano (HMV) located in the Sorokin Trough, northern Black Sea at water depths of >2,000 mbsl. The resulting deep marine data sets include high resolution micro-bathymetry and backscatter data of the mud volcanoes and the surrounding seafloor, sediment and water column temperatures, sediment samples, and in-situ HD-photographic imaging. This allowed us to obtain new insights into the factors controlling mud volcanoes I) formation and development, II) activity, including horizontal and vertical mud migration processes, III) the inter-relationship of neighboring diapir- and fault-formed mud volcanoes and, IV) mud volcano gas emissions

An Autonomous Surface Vehicle for Long Term Operations

Environmental monitoring of marine environments presents several challenges: the harshness of the environment, the often remote location, and most importantly, the vast area it covers. Manual operations are time consuming, often dangerous, and labor intensive. Operations from oceanographic vessels are costly and limited to open seas and generally deeper bodies of water. In addition, with lake, river, and ocean shoreline being a finite resource, waterfront property presents an ever increasing valued commodity, requiring exploration and continued monitoring of remote waterways. In order to efficiently explore and monitor currently known marine environments as well as reach and explore remote areas of interest, we present a design of an autonomous surface vehicle (ASV) with the power to cover large areas, the payload capacity to carry sufficient power and sensor equipment, and enough fuel to remain on task for extended periods. An analysis of the design and a discussion on lessons learned during deployments is presented in this paper.Comment: In proceedings of MTS/IEEE OCEANS, 2018, Charlesto

RRS James Cook Cruise JC120 15 Apr - 19 May 2015. Manzanillo to Manzanillo, Mexico. Managing Impacts of Deep-seA resource exploitation (MIDAS): Clarion-Clipperton Zone North Eastern Area of Particular Environmental Interest

RRS James Cook Cruise JC120 was part of the Managing Impacts of Deep-seA resource exploitation (MIDAS) European Union Framework Programme 7 Project. It was jointly funded by the UK Natural Environment Research Council. JC120 was the first UK science cruise to the Clarion Clipperton Zone (CCZ) in the northern equatorial Pacific, an area likely to be targeted for deep-sea mining for polymetallic nodules. This cruise visited the north easternmost Area of Particular Environmental Importance (APEI). There are a total of nine of these APEIs situated to the north and south of the mining claim areas defined by the International Seabed Authority (ISA) across the CCZ. The APEIs have been delineated by the ISA as part of their environmental management plan for the CCZ and are designed to protect representative species and habitats for the CCZ. The APEIs have been designed based on surface ocean characteristics and the topography of the seafloor, estimated from satellite altimetry. At present there has been virtually no sampling of seafloor habitats or species in the APEIs. The NERC cruise aimed to change that. The cruise studied a representative area of the APEI in great detail at high resolution and over a variety of scales. This characterised the habitats, biology, physical and chemical conditions - adding important information about the CCZ in general and making a detailed baseline assessment for this area, which can be compared to other sites and used as a barometer of change in the deep sea associated with mining activities. The NERC cruise JC120 used a variety of tools for assessment of this >4000m deep area of the CCZ. Shipboard mapping of depth and backscatter were carried out (EM12). The autonomous underwater vehicle (AUV) Autosub6000 carried out wide-area acoustic surveys (Edgetech Side-scan sonar, EM2040 Multibeam Bathymetry and sub-bottom profiler), collected seabed photographs and made physical measurements of the water column of the APEI. There were also more detailed HD video and photographic surveys of the seafloor using the HyBIS vehicle. Sediment samples (megacore, boxcore and gravity core), water samples (CTD) and biological samples (Agassiz Trawl) were also collected

Vision-based navigation for autonomous underwater vehicles

This thesis investigates the use of vision sensors in Autonomous Underwater Vehicle (AUV) navigation, which is typically performed using a combination of dead-reckoning and external acoustic positioning systems. Traditional dead-reckoning sensors such els Doppler Velocity Logs (DVLs) or inertial systems are expensive and result in drifting trajectory estimates. Acoustic positioning systems can be used to correct dead-reckoning drift, however they are time consuming to deploy and have a limited range of operation. Occlusion and multipath problems may also occur when a vehicle operates near the seafloor, particularly in environments such as reefs, ridges and canyons, which are the focus of many AUV applications. Vision-based navigation approaches have the potential to improve the availability and performance of AUVs in a wide range of applications. Visual odometry may replace expensive dead-reckoning sensors in small and low-cost vehicles. Using onboard cameras to correct dead-reckoning drift will allow AUVs to navigate accurately over long distances, without the limitations of acoustic positioning systems. This thesis contains three principal contributions. The first is an algorithm to estimate the trajectory of a vehicle by fusing observations from sonar and monocular vision sensors. The second is a stereo-vision motion estimation approach that can be used on its own to provide odometry estimation, or fused with additional sensors in a Simultaneous Localisation And Mapping (SLAM) framework. The third is an efficient SLAM algorithm that uses visual observations to correct drifting trajectory estimates. Results of this work are presented in simulation and using data collected during several deployments of underwater vehicles in coral reef environments. Trajectory estimation is demonstrated for short transects using the sonar and vision fusion and stereo-vision approaches. Navigation over several kilometres is demonstrated using the SLAM algorithm, where stereo-vision is shown to improve the estimated trajectory produced by a DVL

Design, construction, and operation of an unmanned underwater vehicle

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (leaf [62]).The practical usage of unmanned underwater vehicles (UUVs) is limited by vehicle and operation cost, difficulty in accurate navigation, and communication between the vehicle and operator. The "Rex 2" UUV employs a system design where a submersible is connected to a float at the water's surface by means of a tether. By maintaining a surface expression, high-bandwidth radio communication to the operator becomes possible, and GPS may be used for accurate navigation. This arrangement allows the freedom of movement characteristic of untethered autonomous underwater vehicles (AUVs), while maintaining the live operator control and communication found with tethered remotely operated vehicles (ROVs). Expanding on the design and field experiences with the MIT AUV Lab's first Reef Explorer UUV, Rex 2 was designed to be inexpensive, easy to deploy, adaptable to various payloads, and simple to use. Rex 2 was designed, built, and operated in a number of ocean field tests, validating the utility of the vehicle and system concept.by Dylan Owens.S.M

Autosub Long Range 1500: A continuous 2000 km field trial

Long Range Autonomous Underwater Vehicles (LRAUVs) offer the potential to monitor the ocean at higher spatial and temporal resolutions compared to conventional ship-based techniques. The multi-week to multi-month endurance of LRAUVs enables them to operate independently of a support vessel, creating novel opportunities for ocean observation. The National Oceanography Centre’s Autosub Long Range is one of a small number of vehicles designed for a multi-month endurance. The latest iteration, Autosub Long Range 1500 (ALR1500), is a 1500 m depth-rated LRAUV developed for ocean science in coastal and shelf seas or in the epipelagic and meteorologic regions of the ocean. This paper presents the design of the ALR1500 and results from a five week continuous deployment from Plymouth, UK, to the continental shelf break and back again, a distance of approximately 2000km which consumed half of the installed energy. The LRAUV was unaccompanied throughout the mission and operated continuously beyond visual line of sight