The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In this work a set of near co-located acoustic intensity observations and environmental measurements is presented which allowed quantification of the source of the acoustic scattering and confirmation of backscattering contributions from salinity microstructure. Observations were made by the T-REMUS Autonomous Underwater Vehicle (AUV) in a fresh water plume off a coastal river estuary characterized...
We propose the simulated rendition of the observation of a variety of small sea patches by radar. These patches include a random sea surface of variable state, with possibly the presence of a manufactured, metallic object in its middle. The simulation in itself draws upon two different techniques which are combined: for the free-space propagation, a simple geometrical ray tracing method is used. On...
The determination of the nearshore bathymetry by inverting the propagation of the wave field over shallow waters as observed by ground based X-band radar has became recently part of the coastal monitoring routing. In this investigation, four different wave theories, linear, solitary, modified cnoidal and Stokes extended to shallow waters, are inverted by using the Dispersive Surface Classificator,...
Design of the control unit for the OBSEA seafloor observatory based on a 32 bit microcontroller with SNMP (simple network management protocol) communication.
The receiver signal of sonar systems consists of the sum of reflected signals stemming from many scatterers. The resolution of sonar imaging systems depends in range direction on the bandwidths of the transmitter signal and in angular direction on the beamwidth of the receiver antenna. Tomography is a very promising method to improve the resolution of such sonar systems in angular direction. Basically,...
Nowadays, many voice recognition systems are used in our daily live. In most of case, the transmission canal is the air and they integrate some microphones. The purpose of this study is to develop such a system but able to recognise predefined words under water. To identify those commands sent after their propagation in shallow water (use of the ray tracing theory to simulate the propagation in shallow...
Operational requirements for naval applications have shifted towards the fast, reliable detection and avoidance or elimination of underwater threats (e.g. mines, IEDs (improvised explosive devices),...) over the last decade. For these purposes the ability to reliable separate mines or IEDs from rocks or bottom features is essential. This separation can be much more difficult for IEDs compared to traditional...
In support of development and validation of a wave and current model for the coastal zone off Massachusetts in the United States of America, two deployments of a small tripod were made in 15 m depth in Buzzards Bay. The tripod bore an upward looking Acoustic Doppler Current Profiler (ADCP) and, on one deployment, a Modular Acoustic Velocity Sensor (MAVS) current meter 1.5 m above the bottom. From...
We consider the problem of navigation error detection in synthetic aperture sonar images. Specifically, the effect of errors in the position and attitude of the sonar antenna is explored in the image and frequency domain. We present two metrics which can be used to discriminate between images with different degrees of navigation errors. A systematic test is developed which allows an automatic detection...
Today's situational awareness requirements in the undersea environment present severe challenges for acoustic communication systems. Acoustic propagation through the ocean environment severely limits the capacity of existing underwater communication systems. Specifically, the presence of internal waves coupled with the ocean sound channel creates a stochastic field that introduces deep fades and significant...
In this paper, we analyze a scenario, in which a hydrobot would be sent through the several kilometers thick ice layer of the Jovian Moon Europa, integrated in a melting probe, and once reaching the ocean, would perform a highly autonomous investigation of its habitability. The hydrobot would be either swimming or driving at the bottom of the ocean or the underside of the ice layer, equipped with...
The Ocean Observatories Initiative (OOI) is an environmental observatory covering a diversity of oceanic environments, ranging from the coastal to the deep ocean. Construction is planned to begin in mid-2010 with deployment phased over five years. The key integrating element of the OOI is a comprehensive cyberinfrastructure whose design is based on loosely coupled distributed services, and whose elements...
HF ground wave radar data, collected as part of the European Radar Ocean Sensing Experiment (EuroROSE) in Lyngoy, Norway during April, 2000 using a Wellen Radar (WERA) system with an FMCW waveform, are compared with data simulated from models designed at Memorial University. The similarities between them give a solid confirmation not only of the backscattering cross sections developed for the FMCW...
In this work, we present a concept and the theoretical evaluation of a high resolution 3D imaging sonar system based on high bandwidth transducers and frequency compound imaging.
Underwater acoustic networks (UAN) are becoming an integral part of a wide range of applications, such as those used for exploration and maintenance in the offshore oil and gas industry, surveillance for homeland security, subsea mine counter measures, marine environmental assessment and diving activities. For UAN, efficient and effective media access control (MAC) is a very important requirement...
A new optimal design strategy for monohull vessels is proposed. The goal of the proposed procedure is to make monohulls competitive with their multihull counterparts. The resulting designs, thus, would combine the advantages of high speed vessels with those of simpler monohull vessels. The proposed strategy proposes a new re-formulation of hull optimization problem objective and uses a new class of...
A cabled ocean observatory such as NEPTUNE Canada is a complex system of systems. Technologies include software, firmware, DC power systems, electrical and optical communication systems, subsea cable and connector design, pressure housings and material compatibility to pressure and salt water, as well as instrument transducers and control systems. These systems are designed and built by a variety...
HF radar measurements are presented focussing in particular on the estimation of wave parameters in both high and low sea conditions. In high sea conditions theory suggests that low radio frequencies are needed in order to make wave measurements whereas in low sea conditions, higher radio frequencies are required. The theory is reviewed and measurements used to demonstrate the impact of these theoretical...
Blainville's beaked whale (Mesoplodon densirostris) buzz clicks have been found to have characteristics that can vary significantly. While we have not succeeded to classify them individually, we find that their spectrum is very similar from one click to the next. In previous work, we showed that a multihypothesis tracker can be used to associate these clicks, and subsequently to classify the click...
This work proposes a near-optimal hard output neural network based iterative maximum likelihood sequence estimation (MLSE) equalizer, based on earlier work by the authors, able to equalize single carrier 4-QAM signals in underwater acoustic channels with extremely long delay spreads. The performance of the proposed equalizer is compared to a suboptimal equalization technique, namely Decision Feedback...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.