Pub Date : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603881
Diane D. DiMassa, M. Heron, A. Mantovanelli, S. Heron, C. Steinberg
Coral bleaching is an ecological response to stressful physical conditions observed to occur when strong insolation coupled with stratification of the water column leads to anomalous warming of the surface water. Stratfication requires calm winds, the absence of waves, and an absence of currents: conditions which result in limited mixing of the water column and thus confine heat due to insolation at the ocean surface. There is a strong need to identify which of the physical parameters are more significant at any given time and, more importantly, to monitor the physical parameters in near realtime to serve as a tool for long-term planning and management for marine parks and coastal waters. This paper reviews the contribution that currents make to mixing in the water column through the dissipation of turbulent kinetic energy and takes a further step to evaluate the use of surface current data to provide an index of vertical mixing. In this work, when the surface current speed is greater than a critical value, the water column is found to be vertically mixed even in the absence of wind or waves. A phased array HF Ocean Radar deployed in the southern part of the Great Barrier Reef provides a map of surface currents with high spatial resolution (4km) every 10 minutes over the grid. These surface currents are used to predict vertical stratification and mixing which can then be used as an indication for conditions under which bleaching might occur.
{"title":"Can vertical mixing from turbulent kinetic energy mitigate coral bleaching? An application of high frequency ocean radar","authors":"Diane D. DiMassa, M. Heron, A. Mantovanelli, S. Heron, C. Steinberg","doi":"10.1109/OCEANSSYD.2010.5603881","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603881","url":null,"abstract":"Coral bleaching is an ecological response to stressful physical conditions observed to occur when strong insolation coupled with stratification of the water column leads to anomalous warming of the surface water. Stratfication requires calm winds, the absence of waves, and an absence of currents: conditions which result in limited mixing of the water column and thus confine heat due to insolation at the ocean surface. There is a strong need to identify which of the physical parameters are more significant at any given time and, more importantly, to monitor the physical parameters in near realtime to serve as a tool for long-term planning and management for marine parks and coastal waters. This paper reviews the contribution that currents make to mixing in the water column through the dissipation of turbulent kinetic energy and takes a further step to evaluate the use of surface current data to provide an index of vertical mixing. In this work, when the surface current speed is greater than a critical value, the water column is found to be vertically mixed even in the absence of wind or waves. A phased array HF Ocean Radar deployed in the southern part of the Great Barrier Reef provides a map of surface currents with high spatial resolution (4km) every 10 minutes over the grid. These surface currents are used to predict vertical stratification and mixing which can then be used as an indication for conditions under which bleaching might occur.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124567694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603869
G. Casalino, A. Turetta, E. Simetti, A. Caiti
The paper deals with the problem of distributed acoustic localization of teams of Autonomous Underwater Vehicles (AUVs) and proposes a novel algorithm, Real-Time Ray-Tracing (RT2), for evaluating the distance between any pair of AUVs in the team. The technique, based on a modified formulation of the non-linear sound-ray propagation laws, allows efficiently handling the distorted and reflected acoustic ray paths, induced by the anisotropy of the underwater medium. Further it can be easily implemented on-board of low-cost AUVs. Indeed it just requires the presence, on each vehicle, of a simple acoustic modem and a pair of look-up tables, a-priori constructed via the assumed knowledge of the depth-dependent sound velocity profile. On such a basis, every AUV can easily on-line compute its distance w.r.t. to any other neighbour team member, through time-of-flight measurements and the exchanges of depth information only. Further, since the proposed RT2 algorithm makes available accurate distance evaluations (despite the distorted acoustic rays), the effective filtering techniques normally used by terrestrial mobile robots for distributed localization are expected to be transferable to the underwater field.
{"title":"RT2: A Real-Time Ray-Tracing method for acoustic distance evaluations among cooperating AUVs","authors":"G. Casalino, A. Turetta, E. Simetti, A. Caiti","doi":"10.1109/OCEANSSYD.2010.5603869","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603869","url":null,"abstract":"The paper deals with the problem of distributed acoustic localization of teams of Autonomous Underwater Vehicles (AUVs) and proposes a novel algorithm, Real-Time Ray-Tracing (RT2), for evaluating the distance between any pair of AUVs in the team. The technique, based on a modified formulation of the non-linear sound-ray propagation laws, allows efficiently handling the distorted and reflected acoustic ray paths, induced by the anisotropy of the underwater medium. Further it can be easily implemented on-board of low-cost AUVs. Indeed it just requires the presence, on each vehicle, of a simple acoustic modem and a pair of look-up tables, a-priori constructed via the assumed knowledge of the depth-dependent sound velocity profile. On such a basis, every AUV can easily on-line compute its distance w.r.t. to any other neighbour team member, through time-of-flight measurements and the exchanges of depth information only. Further, since the proposed RT2 algorithm makes available accurate distance evaluations (despite the distorted acoustic rays), the effective filtering techniques normally used by terrestrial mobile robots for distributed localization are expected to be transferable to the underwater field.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129634036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603972
S. Chiba, M. Waki, K. Masuda, T. Ikoma
The type of electroactive polymer known as dielectric elastomers has shown considerable promise for harvesting energy from environmental sources such as ocean waves, wind, water currents, human motion, etc. The high energy density and conversion efficiency of dielectric elastomers can allow for very simple and robust “DIRECT DRIVE” generators. Various types of energy harvesting generators based on dielectric elastomers have been tested. For example, buoy-mounted generators that harvest the energy of ocean waves were tested at sea for two weeks. Each generator uses a proof-mass to provide the mechanical forces that stretch and contract the dielectric elastomer generator. Those generators operated successfully during the sea trials. The buoy-mounted generators will be scaled up to produce larger amounts of power. The use of significantly larger amounts of dielectric elastomer material to produce generator modules with outputs in the MEGAWATT at range is being investigated for application to ocean wave power systems.
{"title":"Current status and future prospects of electric generators using electroactive polymer artificial muscle","authors":"S. Chiba, M. Waki, K. Masuda, T. Ikoma","doi":"10.1109/OCEANSSYD.2010.5603972","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603972","url":null,"abstract":"The type of electroactive polymer known as dielectric elastomers has shown considerable promise for harvesting energy from environmental sources such as ocean waves, wind, water currents, human motion, etc. The high energy density and conversion efficiency of dielectric elastomers can allow for very simple and robust “DIRECT DRIVE” generators. Various types of energy harvesting generators based on dielectric elastomers have been tested. For example, buoy-mounted generators that harvest the energy of ocean waves were tested at sea for two weeks. Each generator uses a proof-mass to provide the mechanical forces that stretch and contract the dielectric elastomer generator. Those generators operated successfully during the sea trials. The buoy-mounted generators will be scaled up to produce larger amounts of power. The use of significantly larger amounts of dielectric elastomer material to produce generator modules with outputs in the MEGAWATT at range is being investigated for application to ocean wave power systems.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130363849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603605
M. Yaacob, M. Arshad, Asrulnizam Abd Manaf
This paper reported modeling and theoretical characterization of circular piezoelectric micromachined ultrasonic transducer (pMUT) for immersion applications. Zinc oxide (ZnO) was employed as piezo active material and nickel aluminum bronze alloy UNS C63000 (CuAl10Ni5Fe4) also known as “sea bronze”, was introduced as electrodes. First, virtual fabrication process was carried out within software environment to form a pMUT model. Then, resonance frequency of the model was finalized and fine tuned by manipulating its structural parameters which are diaphragm diameter and piezo active layer thickness. Next, receiving and transmitting responses were estimated using finite element approach through the combination of piezoelectric analysis and modal analysis. From these analyses, the pMUT model having a resonance frequency of 40.82 kHz was successfully modeled. Transmitting response was estimated at 137 dB (re 1 µPa/V) at 41 kHz on the surface of the transducer while the receiving response was estimated at − 93 dB (re 1 V/µPa) at 38 kHz of frequency. Virtual fabrication process and finite element analysis for model performances estimation have proved to reduce the development time. From the comparison made, the usage of sea bronze and ZnO film replacing conventional gold, platinum and lead zirconate titanate (PZT) were proven to deliver exceptional performances with better durability. However, device fabrication is essential in order to validate the findings and this will be included in our future works. Furthermore, the model needs to be extended so that the value of acoustic impedance within the device can be estimated.
本文报道了浸入式圆形压电微机械超声换能器(pMUT)的建模和理论表征。采用氧化锌(ZnO)作为压电活性材料，采用镍铝青铜合金UNS C63000 (CuAl10Ni5Fe4)(也称“海青铜”)作为电极。首先，在软件环境下进行虚拟制造过程，形成pMUT模型。然后，通过调整振膜直径和压电有源层厚度等结构参数，确定模型的谐振频率并对其进行微调。其次，通过压电分析和模态分析相结合的方法，采用有限元法估计接收和发射响应。通过这些分析，成功地建立了谐振频率为40.82 kHz的pMUT模型。在换能器表面41 kHz时，发射响应估计为137 dB (re 1 μ Pa/V)，而在38 kHz频率下，接收响应估计为- 93 dB (re 1 V/µPa)。虚拟制造过程和模型性能评估的有限元分析已被证明可以缩短开发时间。通过对比发现，使用海青铜和ZnO薄膜代替传统的金、铂和锆钛酸铅(PZT)具有优异的性能和更好的耐久性。然而，为了验证这些发现，设备制造是必不可少的，这将包括在我们未来的工作中。此外，需要对模型进行扩展，以估计设备内的声阻抗值。
{"title":"Modeling and theoretical characterization of circular pMUT for immersion applications","authors":"M. Yaacob, M. Arshad, Asrulnizam Abd Manaf","doi":"10.1109/OCEANSSYD.2010.5603605","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603605","url":null,"abstract":"This paper reported modeling and theoretical characterization of circular piezoelectric micromachined ultrasonic transducer (pMUT) for immersion applications. Zinc oxide (ZnO) was employed as piezo active material and nickel aluminum bronze alloy UNS C63000 (CuAl10Ni5Fe4) also known as “sea bronze”, was introduced as electrodes. First, virtual fabrication process was carried out within software environment to form a pMUT model. Then, resonance frequency of the model was finalized and fine tuned by manipulating its structural parameters which are diaphragm diameter and piezo active layer thickness. Next, receiving and transmitting responses were estimated using finite element approach through the combination of piezoelectric analysis and modal analysis. From these analyses, the pMUT model having a resonance frequency of 40.82 kHz was successfully modeled. Transmitting response was estimated at 137 dB (re 1 µPa/V) at 41 kHz on the surface of the transducer while the receiving response was estimated at − 93 dB (re 1 V/µPa) at 38 kHz of frequency. Virtual fabrication process and finite element analysis for model performances estimation have proved to reduce the development time. From the comparison made, the usage of sea bronze and ZnO film replacing conventional gold, platinum and lead zirconate titanate (PZT) were proven to deliver exceptional performances with better durability. However, device fabrication is essential in order to validate the findings and this will be included in our future works. Furthermore, the model needs to be extended so that the value of acoustic impedance within the device can be estimated.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129184824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603510
N. Farr, A. Bowen, J. Ware, C. Pontbriand, M. Tivey
Communication underwater is severely limited when compared to communications in air because water is essentially opaque to electromagnetic radiation except in the visible band. Even in the visible band, light penetrates only a few hundred meters in the clearest waters and much less in waters made turbid by suspended sediment or high concentrations of marine life. Consequently, acoustic techniques have been developed for underwater communication systems and now represent a relatively mature and robust technology. Acoustic systems are capable of long range communication, but offer limited data rates and significant latency (due to the speed of sound in water). We are developing an optical communication system that complements and integrates with existing acoustic systems resulting in an underwater communications capability offering high data rates and low latency when within optical range combined with long range and robustness of acoustics when outside of optical range. Amongst a wide array of applications, this combination of capabilities will make it possible to operate self-powered ROVs from support vessels or platforms without requiring a physical connection to the ROV. Such a capability will help simplify operations and potentially reduce costs through the use of less capable surface vessels. New deployment strategies may offer game-changing opportunities within all areas of undersea activities. For example, rapid event response will be enhanced and repair and maintenance of the emerging ocean observatory infrastructure will become more cost effective. Such through-water communications will likewise enable exchange of large data files from fixed sensors using AUVs (or ROVs) as data mules, shuttling real-time video from untethered vehicles for inspection, identification, and other related operations. Interconnectivity for dense arrays of underwater sensors without the need for expensive and difficult to install undersea cables is also possible. An unmanned battery operated vehicle, dedicated to a subsea node, that can be wirelessly operated though a combination of acoustic and optical communications, will be an important asset for both scientific exploration and commercial applications.
{"title":"An integrated, underwater optical /acoustic communications system","authors":"N. Farr, A. Bowen, J. Ware, C. Pontbriand, M. Tivey","doi":"10.1109/OCEANSSYD.2010.5603510","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603510","url":null,"abstract":"Communication underwater is severely limited when compared to communications in air because water is essentially opaque to electromagnetic radiation except in the visible band. Even in the visible band, light penetrates only a few hundred meters in the clearest waters and much less in waters made turbid by suspended sediment or high concentrations of marine life. Consequently, acoustic techniques have been developed for underwater communication systems and now represent a relatively mature and robust technology. Acoustic systems are capable of long range communication, but offer limited data rates and significant latency (due to the speed of sound in water). We are developing an optical communication system that complements and integrates with existing acoustic systems resulting in an underwater communications capability offering high data rates and low latency when within optical range combined with long range and robustness of acoustics when outside of optical range. Amongst a wide array of applications, this combination of capabilities will make it possible to operate self-powered ROVs from support vessels or platforms without requiring a physical connection to the ROV. Such a capability will help simplify operations and potentially reduce costs through the use of less capable surface vessels. New deployment strategies may offer game-changing opportunities within all areas of undersea activities. For example, rapid event response will be enhanced and repair and maintenance of the emerging ocean observatory infrastructure will become more cost effective. Such through-water communications will likewise enable exchange of large data files from fixed sensors using AUVs (or ROVs) as data mules, shuttling real-time video from untethered vehicles for inspection, identification, and other related operations. Interconnectivity for dense arrays of underwater sensors without the need for expensive and difficult to install undersea cables is also possible. An unmanned battery operated vehicle, dedicated to a subsea node, that can be wirelessly operated though a combination of acoustic and optical communications, will be an important asset for both scientific exploration and commercial applications.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124110206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603531
S. Bainbridge, D. Eggeling, G. Page
The development and deployment of smart sensors represents a new opportunity for how we measure and monitor maine systems. The linking in of large amounts of real time data into modeling and visualization systems linked in turn to web based knowledge systems will deliver new ways of engaging and interacting with environmental data. One key component of this is allowing the user to decide how they will engage and what products they require and how they want the information to be delivered. The types of environmental futures envisaged by many marine scientists will require new approaches, new ideas and new technologies. The smart sensor systems currently being deployed on the Great Barrier Reef are a start to realizing this new paradigm for the management of marine systems.
{"title":"Smart sensors - a new paradigm for marine management: An example from the Great Barrier Reef","authors":"S. Bainbridge, D. Eggeling, G. Page","doi":"10.1109/OCEANSSYD.2010.5603531","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603531","url":null,"abstract":"The development and deployment of smart sensors represents a new opportunity for how we measure and monitor maine systems. The linking in of large amounts of real time data into modeling and visualization systems linked in turn to web based knowledge systems will deliver new ways of engaging and interacting with environmental data. One key component of this is allowing the user to decide how they will engage and what products they require and how they want the information to be delivered. The types of environmental futures envisaged by many marine scientists will require new approaches, new ideas and new technologies. The smart sensor systems currently being deployed on the Great Barrier Reef are a start to realizing this new paradigm for the management of marine systems.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"394 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123391686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603580
B. Ferguson, D. Carevic
Submarine hydrophone arrays sample the underwater acoustic pressure field in space and time to sense the presence of sources of radiated sound and to extract tactical information from the received sounds. The outputs of the hydrophones are combined by a spatial filter (or beamformer) so that signals from a chosen direction are coherently added while the effects of noise and interference from other directions are reduced by destructive interference. The spatial filter appropriately weights the hydrophone outputs prior to summation so as to enhance the output signal-to-noise ratio, thereby improving the detection, classification, localization and tracking performance of the passive sonar system onboard the submarine. By processing real acoustic data from a submarine hull-mounted array, it is shown that an optimal (adaptive) frequency-domain spatial filter (based on inversion of the observed cross spectral matrix for each frequency bin) enhances the detection of underwater acoustic signals, when compared with conventional spatial filtering (or delay-and-sum beamforming). The degree of improvement, however, depends on the method used to normalize the cross spectral matrix. Superior detection performance for a submarine hull-mounted array occurs when the observed cross spectral matrix for each frequency of interest is normalized using the average of all the single hydrophone output powers at each frequency. It is also shown that the self-noise analysis of a submarine towed array is facilitated by processing the element-level data in the frequency-wave number domain with a constrained optimal spatial filter, which is also referred to as a Minimum Variance Distortionless Response (MVDR) beamformer. This spatiotemporal filtering method is employed to separate signals (surface ship contacts) and tow vessel noise components (direct path and multipath arrivals) according to their directions of propagation. This method is also found to separate spatially-correlated self-noise components that propagate within the towed array structure at a speed that is slower than the speed of sound travel in water. A comparison of the frequency-wave number power spectra estimated using conventional and optimal spatial filtering methods shows that the MVDR spatial filter enables the various sources of acoustic energy that are sensed by the array to be more clearly delineated in frequency-wave number space. The MVDR spatial filter is a data-adaptive spatial filter that is observed to suppress spatial leakage, to enhance the spatial resolution of a towed array through narrower beamwidths, and to provide superdirective array gain at frequencies well below the design frequency of the towed array. Frequency-wave number analysis with optimal spatial filtering is a powerful diagnostic tool for studying the self-noise characteristics of a towed linear array of hydrophones.
{"title":"Optimal spatial filtering of real data from submarine sonar arrays","authors":"B. Ferguson, D. Carevic","doi":"10.1109/OCEANSSYD.2010.5603580","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603580","url":null,"abstract":"Submarine hydrophone arrays sample the underwater acoustic pressure field in space and time to sense the presence of sources of radiated sound and to extract tactical information from the received sounds. The outputs of the hydrophones are combined by a spatial filter (or beamformer) so that signals from a chosen direction are coherently added while the effects of noise and interference from other directions are reduced by destructive interference. The spatial filter appropriately weights the hydrophone outputs prior to summation so as to enhance the output signal-to-noise ratio, thereby improving the detection, classification, localization and tracking performance of the passive sonar system onboard the submarine. By processing real acoustic data from a submarine hull-mounted array, it is shown that an optimal (adaptive) frequency-domain spatial filter (based on inversion of the observed cross spectral matrix for each frequency bin) enhances the detection of underwater acoustic signals, when compared with conventional spatial filtering (or delay-and-sum beamforming). The degree of improvement, however, depends on the method used to normalize the cross spectral matrix. Superior detection performance for a submarine hull-mounted array occurs when the observed cross spectral matrix for each frequency of interest is normalized using the average of all the single hydrophone output powers at each frequency. It is also shown that the self-noise analysis of a submarine towed array is facilitated by processing the element-level data in the frequency-wave number domain with a constrained optimal spatial filter, which is also referred to as a Minimum Variance Distortionless Response (MVDR) beamformer. This spatiotemporal filtering method is employed to separate signals (surface ship contacts) and tow vessel noise components (direct path and multipath arrivals) according to their directions of propagation. This method is also found to separate spatially-correlated self-noise components that propagate within the towed array structure at a speed that is slower than the speed of sound travel in water. A comparison of the frequency-wave number power spectra estimated using conventional and optimal spatial filtering methods shows that the MVDR spatial filter enables the various sources of acoustic energy that are sensed by the array to be more clearly delineated in frequency-wave number space. The MVDR spatial filter is a data-adaptive spatial filter that is observed to suppress spatial leakage, to enhance the spatial resolution of a towed array through narrower beamwidths, and to provide superdirective array gain at frequencies well below the design frequency of the towed array. Frequency-wave number analysis with optimal spatial filtering is a powerful diagnostic tool for studying the self-noise characteristics of a towed linear array of hydrophones.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121292195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5604003
A. Friedman, O. Pizarro, Stefan B. Williams
This paper demonstrates how multi-scale measures of rugosity, slope and aspect can be derived from fine-scale bathymetric reconstructions created using geo-referenced stereo imagery collected by an Autonomous Underwater Vehicle (AUV). We briefly describe the 3D triangular meshes generated from the stereo images and then present a detailed overview of how rugosity can be derived by considering the area of triangles within a window and their projection onto the plane of best fit. By obtaining the plane of best fit, slope and aspect can be calculated with very little extra effort. The results are validated on a simulated surface and the effects of mesh resolution and window size are explored. The technique is demonstrated on real data gathered by an AUV on surveys that cover several linear kilometres and consist of thousands of images. The ability to distinguish habitat types based on rugosity and slope are demonstrated through K-means cluster analysis. A human labelled data set is then used to train a SVM classifier that exhibits promising habitat classification potential based on rugosity and slope.
{"title":"Rugosity, slope and aspect from bathymetric stereo image reconstructions","authors":"A. Friedman, O. Pizarro, Stefan B. Williams","doi":"10.1109/OCEANSSYD.2010.5604003","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5604003","url":null,"abstract":"This paper demonstrates how multi-scale measures of rugosity, slope and aspect can be derived from fine-scale bathymetric reconstructions created using geo-referenced stereo imagery collected by an Autonomous Underwater Vehicle (AUV). We briefly describe the 3D triangular meshes generated from the stereo images and then present a detailed overview of how rugosity can be derived by considering the area of triangles within a window and their projection onto the plane of best fit. By obtaining the plane of best fit, slope and aspect can be calculated with very little extra effort. The results are validated on a simulated surface and the effects of mesh resolution and window size are explored. The technique is demonstrated on real data gathered by an AUV on surveys that cover several linear kilometres and consist of thousands of images. The ability to distinguish habitat types based on rugosity and slope are demonstrated through K-means cluster analysis. A human labelled data set is then used to train a SVM classifier that exhibits promising habitat classification potential based on rugosity and slope.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114100822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603984
Feng Sun, Wen Xu, Liling Jin, Jianlong Li
Dynamic variability in vast ocean environments and limitation in sampling resources have made optimal environmental sampling a hot topic of discussion recently. In this paper we consider the problem of path planning for Autonomous Underwater Vehicles (AUVs) carrying conductivity, temperature and depth (CTD) sensors, aiming to minimizing sound velocity profile prediction uncertainty after assimilating in-situ measurements. The problem is modeled as a non-linear deterministic optimization problem based on maximum a posterior probability (MAP) criterion. An approximated way to calculate the uncertainty reduction for each path group is utilized to save the computation time. Numeric simulation results have confirmed the effectiveness of the approach.
{"title":"Path planning of Autonomous Underwater Vehicles for optimal environmental sampling","authors":"Feng Sun, Wen Xu, Liling Jin, Jianlong Li","doi":"10.1109/OCEANSSYD.2010.5603984","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603984","url":null,"abstract":"Dynamic variability in vast ocean environments and limitation in sampling resources have made optimal environmental sampling a hot topic of discussion recently. In this paper we consider the problem of path planning for Autonomous Underwater Vehicles (AUVs) carrying conductivity, temperature and depth (CTD) sensors, aiming to minimizing sound velocity profile prediction uncertainty after assimilating in-situ measurements. The problem is modeled as a non-linear deterministic optimization problem based on maximum a posterior probability (MAP) criterion. An approximated way to calculate the uncertainty reduction for each path group is utilized to save the computation time. Numeric simulation results have confirmed the effectiveness of the approach.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"90 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124189659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2010-05-24DOI: 10.1109/OCEANSSYD.2010.5603884
Naouraz Brahim, D. Guériot, Sylvie Daniely, B. Solaiman
This paper introduces a system for three-dimensional (3D) reconstruction of underwater environments using multiple images acquired by an acoustical camera from different points of view. The final target of the work is to produce a full 3D representation of the observed environment to improve its exploration and analysis. Indeed, as the DIDSON acoustic camera provides sequences of 2D images (distance and azimuth), the challenge consists in determining the missing elevation information about the observed scene in order to reconstruct (x,y,z) models, together with the geometrical transformation parameters between the acquisition view points, using image information only. Our research work is in its early stage, the work presented in this paper is particularly focused on the first step of the 3D reconstruction system which is feature point extraction as feature points must represent the scene geometrical characteristics. Thus, the proposed methodology is based on corner detection from extracted contours. However, speckle noise introduces local, non-geometrically relevant contours that should be removed. Embedded within a multi-scale edge analysis approach, analyzing extracted contours from several consecutive images allows relevant contours selection. This methodology applied to real and simulated images, shows promising results to complete the full 3D reconstruction process.
{"title":"3D reconstruction of underwater scenes using image sequences from acoustic camera","authors":"Naouraz Brahim, D. Guériot, Sylvie Daniely, B. Solaiman","doi":"10.1109/OCEANSSYD.2010.5603884","DOIUrl":"https://doi.org/10.1109/OCEANSSYD.2010.5603884","url":null,"abstract":"This paper introduces a system for three-dimensional (3D) reconstruction of underwater environments using multiple images acquired by an acoustical camera from different points of view. The final target of the work is to produce a full 3D representation of the observed environment to improve its exploration and analysis. Indeed, as the DIDSON acoustic camera provides sequences of 2D images (distance and azimuth), the challenge consists in determining the missing elevation information about the observed scene in order to reconstruct (x,y,z) models, together with the geometrical transformation parameters between the acquisition view points, using image information only. Our research work is in its early stage, the work presented in this paper is particularly focused on the first step of the 3D reconstruction system which is feature point extraction as feature points must represent the scene geometrical characteristics. Thus, the proposed methodology is based on corner detection from extracted contours. However, speckle noise introduces local, non-geometrically relevant contours that should be removed. Embedded within a multi-scale edge analysis approach, analyzing extracted contours from several consecutive images allows relevant contours selection. This methodology applied to real and simulated images, shows promising results to complete the full 3D reconstruction process.","PeriodicalId":129808,"journal":{"name":"OCEANS'10 IEEE SYDNEY","volume":"117 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128122477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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