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Wiihìn the 3 year project DAEDALUS the battery powered underwater vehicle AUVx was developed at DFKI. This autonomous underwater vehicle (AUV) is a novel, miniaturized exploration and research vehicle (see Fig. 1). The AUVx can be operated both autonomous or remotely as a hybrid ROV with a near field optical communication modem or a copper wire cable. What makes this paper unique is that it describes...
Data communication with high data rate and precise underwater positioning with an accuracy of several centimeters is an unsolved problem. Precise positioning is important for autonomous vehicles. State-of-the-art acoustic communication and distance estimation faces difficulties underwater, e.g. multipath fading or variation of propagation speed. In this work, we propose optical distance estimation,...
The General Bathymetric Chart of the Oceans (GEBCO, http://www.gebco.net/) training of a new generation of hydrographers and scientists in ocean mapping has been funded by the Nippon Foundation, based in Tokyo, Japan, since 2004. The Nippon Foundation is a private, non-profit foundation, whose overall objectives include social innovation, assistance for humanitarian activities and global ocean management...
This paper presents the modeled performance of a navigation algorithm that steers a vessel so that its towed acquisition devices follow a predefined track in variable sea currents. The present study applies that algorithm on a dataset recorded during a scientific seismic acquisition cruise.
Underwater acoustic networks is an enabling technology for a range of applications such as mine countermeasures, intelligence and reconnaissance. Common for these applications is a need for robust information distribution while minimizing energy consumption. In terrestrial wireless networks topology information is often used to enhance the efficiency of routing, in terms of higher capacity and less...
This paper describes the calibration of an underwater navigation system in enclosed scenarios. The work was performed in the context of the VAMOS project addressing the development of robotic solutions for flooded open pit mine exploration. An algorithm for calibration of extrinsic parameters for DVL and USBL systems is presented. Field experiments were performed with the ROAZ autonomous surface vehicle...
Propulsive performance of harmonically heaving and pitching foil is degraded by a breakdown in the angle of attack profile. In this paper, we build up a two-degree freedom harmonic motion in both heave and pitch motion as the baseline, and compare directly the performance obtained with specific angle of attack profiles and three-degree freedom harmonic motion. We set these profiles are: a square,...
In this work the mechanical design of a tide gauge station is presented. The structure consists of a surge pipe anchored to a pier and partially immersed in seawater. Despite such conceptual simplicity, this design required a careful analysis under different points of view to ensure a long life in the hostile environment in which the station will be installed and to guarantee an optimal sea level...
When a submerged target is crossing the source-receiver line, the aberration in the received acoustic field and Doppler shift in the forward scattered field are simultaneously induced. Formulations for the two variations are developed upon an ideal forward scattering configuration. Both the field aberration and Doppler shift are expressed as functions with the same argument — target motion time. The...
This work proposes an approach that finds efficient representations for training and classification of different mine like objects (MLOs) in underwater imagery, e.g. side scan sonar and synthetic aperture sonar (SAS). The focus is on the design and selection of a compact, optimal and a non linear snbspace, a dictionary, based on the gradient and curvature models in 2D images. Here, the traditional...
Oceanographic fronts are boundaries between water masses with differences in hydrography. Often the presence of fronts coincide with oceanographic currents. The detection of fronts has traditionally been carried out by looking for sudden horizontal changes in the sea surface temperature or salinity. Applications involving temperature or salinity alone, may therefore overlook significant oceanic fronts...
This paper describes the adaptation of an existing wave filtering method for vessel Dynamic Positioning (DP) Systems for use in a Remotely Operated Vehicle (ROV) control system. The novelty is that the proposed control system will work in tandem with a Lagrangian waverider buoy deployed on a Marine Renewable Energy (MRE) site. The waverider will be tethered to a moored buoy on site, and will have...
The optical satellite imagery with high resolution and large coverage has been widely applied to gain the geospatial information of island and reef area. In this paper, according to the repeated observation of satellites, the method of georeferencing with multi-source optical satellite imagery is presented, in which the constraint model is introduced in to solve the rank defect of the coefficient...
With the proliferation of exciting tools such as GPS, voice assistants, and cloud computing, advanced technology is in the hands of the average person more than ever before. In the field of marine technology, this is especially true. Previously only the most well-funded research programs could afford equipment such as Remote Operated Vehicles (ROVs), but in recent years more cost efficient solutions...
On the base of laboratory experiment the regularities of changes of the transformation coefficient and of mean wave period on the wave parameters and parameters of submerged bars of different permeability were obtained. The typical scenarios of cross-shore sediment transport above sloping bottom profile with submerged bar and assessments of the contribution of physical processes of wave transformation...
In this paper, the conceptual design and practical construction of a wind propelled Autonomous Surface Vehicle (ASV), for marine research are described. The ASPire (Autonomous Sailing Platform) will be deployed for collecting marine sensor data (i.e., Conductivity, Temperature and Density (CTD) measurements) and for passive-acoustic monitoring (PAM) of harbor porpoise in the vicinity of the Åland...
The growth of biofilms in seawater-cooled heat exchangers limits the heat exchange of their surfaces, with high impact in the design and maintenance operations. The principal aim of this work has been to study the fit of different biological growth models to the development of biofilms in heat exchangers, with incorporation of the tube surface roughness effects as a main parameter. This study was...
Field optical measurement results show that a classification study of inshore water is necessary. Typical dehazing methods rely on a dark channel model using global rough estimates of back-scattering, that performs poorly on inshore underwater image restoration. This paper introduces a restoration approach to the problem that focuses on inshore water body optical properties. The method introduces...
Underwater environment is modeled as a bounded medium with the surface and bottom. Different acoustic models are used to model sound propagation in underwater environment. In this work a broadband mode based model, proposed for underground tunnels, is adapted for underwater environment and ray-mode analogy is studied in detail. In ray theory, the wave field is modeled as a sum of paths between the...
This paper deals with accurate navigation for underwater remotely operated vehicles. A feasibility study for a multi-pressure device to be mounted on an ROV is presented. The device can provide accurate estimates of a ROV orientation and angular speed. It is based on the well-known total pressure principle, also used in a Pitot tube, and allows reconstruction of static and dynamic pressures, which...
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