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Intervention in deep and ultra deep water requires increasing amounts of power on the seabed, not just to meet current needs, but to supply the greater demands of subsea processing. If cable sizes are to be kept manageable, efficiency will have to be improved. This can be achieved by using higher voltages. Electrical cables that are deployed from the surface are described as 'dynamic' and have to...
This paper presents a new method to estimate J motion parameters of loud transiting acoustic sources with a single stationary hydrophone in shallow water environments. The parameters of interest include the time of Closest Point of Approach (CPA) and the ratio of velocity over the CPA range. The method involves only processing the intensity surface of the spectrogram of received broadband acoustic...
The last decade has seen a number of Coastal States seek to enact 'Oceans Act' type legislation, to regulate the broad and burgeoning range of maritime activities in the waters under their jurisdiction. For the purpose of this paper, Oceans Act legislation is a generic term for all new or existing Coastal State sponsored legislation seeking to regulate activity in their waters. A recent example of...
Acoustic ultrasonic measurements are widespread and commonly performed using sensitive piezoelectric sensors. An accurate transducer system response to investigate pressure fluctuations in water and their subsequent detection remains a challenge. Typically, these sensors exploit the resonant behaviour of the piezoelectric active element, being designed to give maximum sensitivity in the bandwidth...
A novel yet simple underwater retractable autonomous buoy platform is proposed, whereby a shallow-water buoyancy adjusted platform is able to repetitively transport data from the seafloor to the sea surface. This generic platform design significantly negates much of the environmental and human interference risk factors that often hinder similar technologies. When fitted with suitable payload sensors,...
We have developed a design template for simple, inexpensive model Remotely Operated Vehicles (ROVs) for the purpose of introducing students and schoolchildren to the field of underwater robotics. In this paper we outline our ROV design principles and report on some recent educational applications and workshops using our model ROVs.
Real-time accurate positioning is a key technology for autonomous underwater vehicles to perform close-range seafloor observations such as photo mosaicing. This paper proposes a real-time positioning method that realizes robust and drift-free positioning in a local area based on a passive acoustic landmarks set in the environment and a profiling sonar (profiler) mounted on the vehicle. The method...
The future of marine survey sensors, processing and platforms is reviewed. Seabed survey from autonomous marine platforms is now possible, but, apart from a few niche applications, it is not yet more useful than the manned alternative. However, advances in sensor technology, sensor processing, sensor data merging, and vehicle autonomy will cause the operational-and cost effectiveness of such systems...
We observed the internal wave features in ERS1/2 SAR and ASTER images data over Japan waters, during 1993-2004 period. The internal wave features were shown in the Tsushima Strait, coast of Izu Peninsula, coast of Ibaraki in east of Honshu, coast of Sado Island in west of Honshu, and southwest and south of Hokkaido. The internal wave feature characteristics in image suggest tidal generation source...
Data collected from the Kauai experiment (KauaiEx) shows that the fluctuations of the ocean environment can cause significant variations of the acoustic signals propagating in the shallow water regions. The power level of the arrivals that do not interact with the sea surface is mainly affected by the variability of the ocean water column. The power level of the arrivals that interact with the sea...
This paper applies target-tracking technology to the processing of mammal vocalizations or clicks, with the goal of identifying the number of marine mammals in a surveillance region. This problem has direct application to marine mammal mitigation efforts in the context of active sonar operations. In earlier work, we documented our results in the analysis of hydrophone datasets with detection processing...
JAMSTEC has developed the two types of underwater vehicle since 2005: an ROV to the oceans' deepest depth called ASSS11k (advanced sediment sampling system to 11,000 meter) and a hybrid underwater vehicle for use in shallow-water to mid-depth zones named PICASSO (Plankton Investigatory Collaborating Autonomous Survey System Operon). The most important purpose of the ASSS11k is to get a lot of mud...
In coastal oceanography, currents are difficult to measure with a good temporal and spatial resolution. Nevertheless, precise knowledge of these currents is crucial for certain applications such as pollution monitoring. Up until now, very few instruments have been able to provide current measurements. Although techniques based on HF radar and satellite-based Synthetic Aperture Radar(SAR) are promising,...
Fluid motion, like in environmental flows, may generate chaotic advection: the particles transported by the flow typically exhibit chaotic dynamics. This manifests itself in that the particles trace out complicated geometrical objects, filamentary fractal structures. The appearance of these complex fractal structures plays an important role if the advected particles are chemically or biologically...
System evaluation of AUV embedded technologies via the standard hardware-in-the-loop (HIL) method is based solely on the outcome of the actual embedded system. This limits the amount of testing that can be done before real world trials of the platform. This paper proposes a novel framework for rapid evaluation and integration of embedded technologies for AUVs. The proposed framework uses the concepts...
We present a path tracking algorithm for navigation of an oceanographic unmanned aeronautical vehicle. Aircraft bank angle is used to maintain desired closing speeds along and normal to the desired track. The algorithm is capable of tracking linear and circular path segments. Simulated flights under near gale force winds suggest the algorithm is sufficiently robust for practical navigation during...
High precision atmospheric oxygen (O2) measurements are a relatively new and powerful tool for studying the global carbon cycle. Despite the development of several techniques for achieving these measurements over the past two decades, the quantification of small changes (ppm-level) in the background concentration of O2 (21%) still remains very challenging. We have built a measuring system capable...
Corpus Christi Bay (Texas, USA) is home to the nation's seventh largest port with numerous petrochemical facilities. This shallow wind-driven bay (average depth 3 m) is very dynamic, and is typically a well-mixed system. However, the water column becomes stratified during the summer months in the south-east portion of the bay, and so dissolved oxygen (DO) in the upper-layer water column is not able...
Echoes from patches of fish fluctuate significantly from ping to ping as the sonar beam is swept across the patches. The fluctuations can be strongly non-Rayleigh because 1) there can be a small number of targets in the beam at a time, 2) the distribution of fish can be inhomogeneous, or "patchy", and 3) the echoes are weighted by the non-uniform response of the sonar beam. We have previously...
The presence of multiple, apparently independent track segments originating from the same target complicates the track-level passive sonar picture. If some of these segments can be shown to have common origin, they can be associated into a single composite track, simplifying that picture. The process could also provide additional information about the target, such as range or classification. Track...
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