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ESONIM seeks to facilitate the establishment of a European Seafloor Observatory Network (ESONET) by providing EU member state governments with the technical, legal and financial models and arguments to establish one or establishing seafloor observatories in European waters has been made by the ESONET project. Therefore, ESONIM focuses on detailing the technical specification of a model observatory...
Underwater acoustic communications in their present form do not appear to provide an ability to dramatically increase throughput or range at reasonable energy efficiency. Networks with a long, single-hop between nodes require a significant increase in power to increase throughput or range. Multi-hop networks at current operating frequencies offer improvements in energy efficiency or range, but with...
In this paper wave data from two different coastal stations will be discussed with respect to spatial inhomogeneities in the wave field. Effects of the changes in the local topography and strong tidal currents are reproduced in the radar data. The discussion will focus on the potentials of these data to monitor spatial and temporal variabilities of the sea state in coastal approaches. As an example,...
Dual Wellen HF Radar (WERA) systems have been observing near-surface currents and wave parameters over the Southeast Florida shelf since June 2004 as a part of the Southeast Atlantic Coastal Ocean Observing System (SEACOOS). The region of coverage includes the Florida Straits and the Florida Current (FC) which typically has maximum surface velocities approaching 2 ms"1. The echo-Doppler spectra...
Impulsive biological noise produced by snapping shrimp provides an important contribution to the ambient acoustic noise in warm, coastal waters. The challenge is to understand and model the properties of shrimp noise to reduce its impact on sonar and underwater acoustic telemetry systems. Shrimp snaps are impulsive events occurring apparently at random. The short duration of each snap allows these...
The subdiscipline field of ocean optics has advanced dramatically in the last 2 decade due to a culmination of advances. These advances include large strides in our quantitative understanding of theoretical ocean optics, technological innovations in instrumentation and progress in utilizing interdisciplinary observational platforms. Theoretical understandings of ocean optical processes have evolved...
An autonomous underwater vehicle (AUV) is equipped with an inertial navigation system (INS) in order to understand its own position in real time while it cruises without the communication with the external environment such as a support ship and GPS. Japan Agency for Marine-Earth Science and Technology has the cruising AUV URASHIMA, and it is also equipped with the INS. However the INS outputs its...
Automatic manmade object detection from sidescan sonar image is a key step for automatic mine countermeasure. A high detection rate and low false alarm rate are required if the mine countermeasure system can find the target and destroy it without operator interfering. In our previous work, an algorithm for manmade object detection has been developed for after-mission processing. In order to maintain...
This paper presents a stable formation control scheme for multiple autonomous underwater vehicle (AUV) where the number of independent actuators for each vehicle are less than that of degree of freedom (DOF) of the vehicle's motion. In many of the formation schemes presented so far, the multiple dynamic agents were usually modeled as particles whose motions can be expressed as simple second-order...
In this paper, we describe an electronic holographic camera that has been developed for in situ underwater studies of the distribution and dynamics of plankton and other marine organisms and particles. Holographic data are stored on an embedded computer in the camera for later data extraction and analysis. We describe the main optical and mechanical specifications and outline the design, development...
The target strengths of hollow ceramic flotation spheres manufactured by DeepSea Power and Light, Inc., and tested to a pressure equivalent of 12,000 m have been measured as a function of frequency over the bands 10-150 kHz. The spheres are made of alumina, purity 99.9%, with diameter 91.44 plusmn 0.2 mm, nominal thickness 1.3 mm, mass 140 plusmn 1 g. The target strength spectra have also been calculated...
This paper reports on recent computational fluid dynamics (CFD) work, revisiting the concept of the tear drop shaped laminar flow hull and compares it with practical drag data, both laminar body and torpedo shape, that has been accumulated over the years. A short vehicle of length /diameter ratio 3 to 4 can be a more practical proposition with little if any increase in drag coefficient (Cd). The laminar...
This paper describes an underwater sensor network with dual communication and support for sensing and mobility. The nodes in the system are connected acoustically for broadcast communication using an acoustic modem we developed. The nodes are connected optically for higher speed point to point data transfers using an optical modem we developed. We describe the hardware details of the underwater sensor...
A new autonomous underwater vehicle for exploring the upper water column has been developed. The Autonomous Underwater Explorer (AUE) is a 25 cm diameter sphere whose mission is to monitor currents in the upper 100 m of the ocean via either underwater acoustic tracking or by providing a (lat, Ion) fix via GPS after surfacing. Equipped with both temperature and depth sensors the float is capable of...
Multiple-receiver synthetic aperture sonar (SAS) imaging with Displaced Phase Center (DPC) technique can solve the confliction between mapping speed and resolution, but this mode brings some phase error and restricts the selection of velocity of the SAS carrier and the pulse repetition frequency (PRF), namely, the SAS carrier velocity has to be chosen such that the SAS carrier moves just one half...
Estimations of seafloor clutter (also called mine-like echoes) and roughness (bottom relief) are needed during mine warfare operations to determine seafloor type for a geographic region of interest. Analysts at the Naval Oceanographic Office estimate bottom clutter and roughness from sidescan sonar imagery (SSI). However, detecting clutter and determining roughness manually is often time consuming...
A review of experimental evidence shows that the low frequency attenuation of compressional acoustic waves in sandy marine sediments obeys a simple power law consistent with a frequency dependent attenuation proportional to fn , n =1.0. This observation is in general agreement with Biot's model (1956) for frequencies less than 1 kHz. Recent theoretical work [A. D. Pierce etal., Proc. Oceans 2005,...
Direct sequence spread spectrum (DSSS) uses a code sequence to spread the symbols at the transmitter and a de-spreader at the receiver to recover the transmitted symbols. The de-spreader via a correlator or a matched filter provides a processing gain (matched filter gain) which enhances the symbol energy over noise thus allowing communications at low input signal-to-noise ratio. This paper analyzes...
A new generation of autonomous underwater gliders is currently being developed for the fields of marine biology, physical oceanography, and marine environmental studies, assessment and management at the Florida Institute of Technology, Melbourne Florida, USA. The end-product of the project will be an autonomous powered glider that collects video, acoustic, and physical data, simultaneously obtains...
The marine environment is immensely challenging to all technologies, thus risk is ever present in ocean engineering. In the case of autonomous underwater vehicles, however, risk takes on new dimensions. Engineers must evaluate and overcome technical risks to ensure reliable functioning of an AUV. Operators must develop and rigorously apply standard operating procedures to ensure both the safety of...
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