1P1-A14 Real-time terrain based localization method : Observation of deep ocean floor using an AUV

2009 ◽  
Vol 2009 (0) ◽  
pp. _1P1-A14_1-_1P1-A14_4
Author(s):  
Takeshi NAKATANI ◽  
Tamaki URA ◽  
Takashi SAKAMAKI ◽  
Junichi Kojima
2006 ◽  
Author(s):  
Eric Kaltenbacher ◽  
David Costello ◽  
Kendall Carder
Keyword(s):  

2009 ◽  
Vol 26 (3) ◽  
pp. 556-569 ◽  
Author(s):  
Ananda Pascual ◽  
Christine Boone ◽  
Gilles Larnicol ◽  
Pierre-Yves Le Traon

Abstract The timeliness of satellite altimeter measurements has a significant effect on their value for operational oceanography. In this paper, an Observing System Experiment (OSE) approach is used to assess the quality of real-time altimeter products, a key issue for robust monitoring and forecasting of the ocean state. In addition, the effect of two improved geophysical corrections and the number of missions that are combined in the altimeter products are also analyzed. The improved tidal and atmospheric corrections have a significant effect in coastal areas (0–100 km from the shore), and a comparison with tide gauge observations shows a slightly better agreement with the gridded delayed-time sea level anomalies (SLAs) with two altimeters [Jason-1 and European Remote Sensing Satellite-2 (ERS-2)/Envisat] using the new geophysical corrections (mean square differences in percent of tide gauge variance of 35.3%) than those with four missions [Jason-1, ERS/Envisat, Ocean Topography Experiment (TOPEX)/Poseidoninterlaced, and Geosat Follow-On] but using the old corrections (36.7%). In the deep ocean, however, the correction improvements have little influence. The performance of fast delivery products versus delayed-time data is compared using independent in situ data (tide gauge and drifter data). It clearly highlights the degradation of real-time SLA maps versus the delayed-time SLA maps: four altimeters are needed in real time to get the similar quality performance as two altimeters in delayed time (sea level error misfit around 36%, and zonal and meridional velocity estimation errors of 27% and 33%, respectively). This study proves that the continuous improvement of geophysical corrections is very important, and that it is essential to stay above a minimum threshold of four available altimetric missions to capture the main space and time oceanic scales in fast delivery products.


2018 ◽  
Vol 52 (3) ◽  
pp. 100-108 ◽  
Author(s):  
Takeshi Nakamura ◽  
Narumi Takahashi ◽  
Kensuke Suzuki

AbstractThe deployment of real-time permanent ocean-bottom seismic and tsunami observatories is significant for disaster mitigation and prevention during the occurrence of large subduction earthquakes near trough areas. On April 1, 2016, a moderate-sized suboceanic earthquake occurred beneath Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) stations that were recently deployed in deep ocean-bottom areas near the Nankai Trough in southwest Japan. P-waves arrived at the ocean-bottom station within 4 s of the origin time, which was 6 and 13 s earlier than the arrival of P- and S-waves at a land station in the coastal area, respectively; this implies earlier detection of strong motion than at land stations. However, the waveforms are amplified by sediment layers and even contaminated with acceleration offsets at some stations, which would lead to overestimations during source investigations. Such amplification and offset did not occur at a borehole station connected to DONET. The amplifications caused by the sediment layers and the offset were found to have a considerable spatial variation, not only between the DONET stations and land and borehole stations but also among the DONET stations, implying that the amplitude evaluation could be unstable. Therefore, procedures for correcting or suppressing the amplification and offset problem are required for conducting waveform analyses, such as magnitude estimations and source modeling, during large subduction earthquakes.


Author(s):  
Steinar Løve Ellefmo ◽  
Thomas Kuhn

AbstractMinerals and metals are of uttermost importance in our society, and mineral resources on and beneath the deep ocean floor represent a huge potential. Deciding whether mining from the deep ocean floor is financially, environmentally and technologically feasible requires information. Due to great depths and harsh conditions, this information is expensive and time and resource consuming to obtain. It is therefore important to use every piece of data in an optimum way. In this study, data retrieved from images and expert knowledge were used to estimate minimum and maximum nodule abundances at image locations from an area in the Clarion-Clipperton-Zone of the equatorial North East Pacific. From the minimum and maximum values, box cores and the spatial correlation quantified through variogram, a conditional expectation and associated uncertainty were obtained through the Gibbs sampler. The conditional expectation and the uncertainty were used with the assumed certain abundance data from the box cores in a kriging exercise to obtain better informed estimates of the block by block abundance. The quality assessment of the estimations was done based on distance criterion and on kriging quality indicators like the slope of regression and the weight of the mean. From the original image locations, alternative image configurations were tested, and it was shown that such alternatives produce better estimates, without extra costs. Future improvements will focus on improving the estimation of the minimum and the maximum values at image locations.


2004 ◽  
Vol 89 (516) ◽  
pp. 437-440 ◽  
Author(s):  
Maurice N. Brearley

A tsunami usually starts on deep ocean water as a result of a submarine earthquake. A tsunami wave is very long, even as much as tens of kilometres, but of only very small amplitude, typically less than half a metre (Bascom [1]). In mid-ocean, the passage of a tsunami is imperceptible, but on reaching a shore it can achieve great heights and can deliver massive surges of water. Before the arrival of the first surge, and between subsequent surges, the water at a shore line usually retracts for a long distance, leaving bare large areas of ocean floor that are normally under water. This paper analyses the behaviour of a tsunami, and explains how its mid-ocean character is transformed to produce such massive surges of water at a shore line.


1971 ◽  
Vol 11 (1) ◽  
pp. 27
Author(s):  
J. B. R. Livermore

For countless centuries the activities of man were bounded, in the main, by the limits of the dry land on which he lived. Some of the more intrepid ventured out upon the seas and oceans — to fish, to explore, to trade, or to fight. In the twentieth century man has conquered the air and circled the globe in space.Now the world looks to another new frontier — the field of exploration of the seabed beneath the oceans. In recent decades there has been an awakening to the existence of natural resources in the seabed and ocean floor.Tliis prospect of discoiering, and more importantly producing, minerals from the deep ocean floor, appears to offer the potential of expanding the resource base of modern civilisation at a time when a growing world population, coupled with rising standards of living, are throwing increased demands on the world's known stock of natural resources.For three years the United Nations, following an initiative by the island state of Malta, has been discussing the reservation, exclusively for peaceful purposes, of the seabed and ocean floor beyond the limits of national jurisdiction, and the use of the resources of this area, in the interests of mankind as a whole.During these discussions diverse points of view have emerged: some would restrict the jurisdiction of a coastal state severely; others argue for extensive coastal state jurisdiction. Some want elaborate and comprehensive international machinery to control all activities on the seabed in accordance with a regime agreed internationally; others support more modest arrangements arguing that elaborate machinery would swallow up the financial benefits and leave little or nothing for the world community; still others contend that the regime and machinery should, initially at least, be resource oriented.The Australian delegation has put the view that any international arrangements for the deep seabed must be effective, credible and impartial. Such arrangements must not only command the support of the nations of the world regardless of geographical location or political system, they must also instil confidence in the minds of operators that rights granted can, and will, be upheld.Moves are developing for a further comprehensive law of the sea conference — perhaps within two or three years - which will tackle several outstanding matters including, importantly, that of a suitable regime and administrative machinery for the seabed and ocean floor beyond national jurisdiction. Inevitably this will involve consideration of the imprecision of the limits of the continental shelf as presently defined by the Geneva Convention of 1958. Other subjects requiring attention are the breadth of the territorial sea, rights of passage through straits and fisheries matters.Australia, an island continent with a long coastline and an extensive continental shelf, has a vital interest in the course of these deliberations.


2013 ◽  
Vol 391 ◽  
pp. 580-583 ◽  
Author(s):  
Tian Yi Gu ◽  
Zhao Zhao ◽  
Ya Qi Wu ◽  
Zhi Yong Xu ◽  
Jing Yi Wang

A real-time disambiguous localization method for multiple acoustic sources using widely spaced microphone array is proposed in this paper. The observation signals in each frame are firstly discriminated utilizing conventional energy-based sound detection measurement. Using inter-microphone phase differences (IPD), as well as an iterative cluster process, the DOAs of sources can be estimated while the phase wrapping ambiguity in conventional DUET is avoided.


Geophysics ◽  
1991 ◽  
Vol 56 (8) ◽  
pp. 1153-1157 ◽  
Author(s):  
Andrew R. Ochadlick

Magnetic data sets over deep ocean areas may contain clues to the existence of craters formed by the impact of an extraterrestrial body with the Earth’s ocean crust. To aid in the magnetic exploration of the ocean crust for oceanic impact craters, basic but effective computations from an impact model are studied from an aeromagnetic point of view. The main assumption of the analysis is that a sufficiently large impact can excavate large volumes of magnetized basalt, vaporize basalt, and raise basalt to temperatures above the Curie temperature (approximately 500°C) to alter the preimpact magnetization of the ocean floor and result in a magnetic anomaly being associated with an oceanic impact crater. In the absence of an existing theory on the influence of impacts on ocean crustal magnetization, the representation of a crater on the ocean floor by a simple potential provides, apparently for the first time, quantitative estimates of the crater’s magnetic anomaly along a horizontal surface. Numerical results from the model suggest that the detection of the anomaly of a Cretaceous‐Tertiary (K-T) type of impact is well within the capabilities of aeromagnetic technology.


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