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Cara Wilson - One of the best experts on this subject based on the ideXlab platform.
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a comparison of the pac x trans pacific wave glider data and satellite data modis aquarius trmm and viirs
PLOS ONE, 2014Co-Authors: Tracy A Villareal, Cara WilsonAbstract:Four wave-propelled autonomous vehicles (Wave Gliders) instrumented with a variety of oceanographic and meteorological sensors were launched from San Francisco, CA in November 2011 for a trans-Pacific (Pac-X) voyage to test platform endurance. Two arrived in Australia, one in Dec 2012 and one in February 2013, while the two destined for Japan both ran into technical difficulties and did not arrive at their destination. The Gliders were all equipped with sensors to measure temperature, salinity, turbidity, oxygen, and both chlorophyll and oil fluorescence. Here we conduct an initial assessment of the data set, noting necessary quality control steps and instrument utility. We conduct a validation of the Pac-X dataset by comparing the glider data to equivalent, or near-equivalent, satellite measurements. Sea surface temperature and salinity compared well to satellite measurements. Chl fluorescence from the Gliders was more poorly correlated, with substantial between glider variability. Both turbidity and oil CDOM sensors were compromised to some degree by interfering processes. The well-known diel cycle in chlorophyll fluorescence was observed suggesting that mapping physiological data over large scales is possible. The Gliders captured the Pacific Ocean’s major oceanographic features including the increased chlorophyll biomass of the California Current and equatorial upwelling. A comparison of satellite sea surface salinity (Aquarius) and glider-measured salinity revealed thin low salinity lenses in the southwestern Pacific Ocean. One glider survived a direct passage through a tropical cyclone. Two Gliders traversed an open ocean phytoplankton bloom; extensive spiking in the chlorophyll fluorescence data is consistent with aggregation and highlights another potential future use for the Gliders. On long missions, redundant instrumentation would aid in interpreting unusual data streams, as well as a means to periodically image the sensor heads. Instrument placement is critical to minimize bubble-related problems in the data.
Tracy A Villareal - One of the best experts on this subject based on the ideXlab platform.
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a comparison of the pac x trans pacific wave glider data and satellite data modis aquarius trmm and viirs
PLOS ONE, 2014Co-Authors: Tracy A Villareal, Cara WilsonAbstract:Four wave-propelled autonomous vehicles (Wave Gliders) instrumented with a variety of oceanographic and meteorological sensors were launched from San Francisco, CA in November 2011 for a trans-Pacific (Pac-X) voyage to test platform endurance. Two arrived in Australia, one in Dec 2012 and one in February 2013, while the two destined for Japan both ran into technical difficulties and did not arrive at their destination. The Gliders were all equipped with sensors to measure temperature, salinity, turbidity, oxygen, and both chlorophyll and oil fluorescence. Here we conduct an initial assessment of the data set, noting necessary quality control steps and instrument utility. We conduct a validation of the Pac-X dataset by comparing the glider data to equivalent, or near-equivalent, satellite measurements. Sea surface temperature and salinity compared well to satellite measurements. Chl fluorescence from the Gliders was more poorly correlated, with substantial between glider variability. Both turbidity and oil CDOM sensors were compromised to some degree by interfering processes. The well-known diel cycle in chlorophyll fluorescence was observed suggesting that mapping physiological data over large scales is possible. The Gliders captured the Pacific Ocean’s major oceanographic features including the increased chlorophyll biomass of the California Current and equatorial upwelling. A comparison of satellite sea surface salinity (Aquarius) and glider-measured salinity revealed thin low salinity lenses in the southwestern Pacific Ocean. One glider survived a direct passage through a tropical cyclone. Two Gliders traversed an open ocean phytoplankton bloom; extensive spiking in the chlorophyll fluorescence data is consistent with aggregation and highlights another potential future use for the Gliders. On long missions, redundant instrumentation would aid in interpreting unusual data streams, as well as a means to periodically image the sensor heads. Instrument placement is critical to minimize bubble-related problems in the data.
G Griffiths - One of the best experts on this subject based on the ideXlab platform.
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underwater glider reliability and implications for survey design
Journal of Atmospheric and Oceanic Technology, 2014Co-Authors: Mario P Brito, D A Smeed, G GriffithsAbstract:It has been 20 years since the concept of Autonomous Oceanographic Sampling Network (AOSN) was first introduced. This vision has been brought closer to reality with the introduction of undersea Gliders. Whilst in terms of functionality the undersea glider has shown to be capable of meeting the AOSN vision, in terms of reliability there is no community-wide hard evidence on whether persistent presence is currently being achieved. This paper studies the reliability of undersea Gliders in order to assess the feasibility of using these platforms for future AOSN. The data used is taken from 205 deployments of Gliders by 12 European laboratories between 2008 and 2012. Risk profiles were calculated for two makes of deep underwater glider; there is no statistically significant difference between them. Regardless of make the probability of a deep undersea glider surviving a 90 day mission without pre-mature mission end is approximately 0.5. The probability of a shallow undersea glider surviving 30 day mission without premature mission end is 0.59. This implies that to date factors other than the energy available are preventing undersea Gliders achieving their maximum capability. This reliability information was used to quantify the likelihood of two reported undersea glider surveys meeting the observation needs for a period of 6 months and to quantify the level of redundancy needed to in order to increase the likelihood of meeting the observation needs.
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an assessment of the use of ocean Gliders to undertake acoustic measurements of zooplankton the distribution and density of antarctic krill euphausia superba in the weddell sea
Limnology and Oceanography-methods, 2014Co-Authors: Damien Guihen, Sophie Fielding, Eugene J Murphy, Karen J Heywood, G GriffithsAbstract:A calibrated 120 kHz single-beam echo-sounder was integrated into an ocean glider and deployed in the Weddell Sea, Southern Ocean. The glider was deployed for two short periods in January 2012, in separate survey boxes on the continental shelf to the east of the Antarctic Peninsula, to assess the distribution of Antarctic krill (Euphausia superba). During the glider missions, a research vessel undertook acoustic transects using a calibrated, hull-mounted, multi-frequency echo-sounder. Net hauls were taken to validate acoustic targets and parameterize acoustic models. Krill targets were identified using a thresholded schools analysis technique (SHAPES), and acoustic data were converted to krill density using the stochastic distorted-wave Born approximation (SDWBA) target strength model. A sensitivity analysis of glider pitch and roll indicated that, if not taken into account, glider orientation can impact density estimates by up to 8-fold. Glider-based, echo-sounder–derived krill density profiles for the two survey boxes showed features coherent with ship-borne measurements, with peak densities in both boxes around a depth of 60 m. Monte Carlo simulation of glider subsampling of ship-borne data showed no significant difference from observed profiles. Simulated glider dives required at least an order of magnitude more time than the ship to similarly estimate the abundance of krill within the sample regions. These analyses highlight the need for suitable sampling strategies for glider-based observations and are our first steps toward using autonomous underwater vehicles for ecosystem assessment and long-term monitoring. With appropriate survey design, Gliders can be used for estimating krill distribution and abundance.
Fumin Zhang - One of the best experts on this subject based on the ideXlab platform.
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spiraling motion of underwater Gliders modeling analysis and experimental results
Ocean Engineering, 2013Co-Authors: Shaowei Zhang, Aiqun Zhang, Fumin ZhangAbstract:This paper presents a thorough approach characterizing the spiraling motion of underwater Gliders. The dynamic model for underwater Gliders, steered by a single internal movable and rotatable mass, is established. Spiraling motions are equilibria of the dynamics, for which equations are derived and then solved by a recursive algorithm with fast convergence. This theoretical method is applied to the Seawing underwater glider whose hydrodynamic coefficients are computed using computational fluid dynamics (CFD) software packages. In a recent experiment in the South China Sea, the Seawing glider produced a spiraling motion against strong ocean current, agreeing with theoretical predictions. Hence the recursive algorithm may be used to compute control input to achieve desired spiraling motion for underwater Gliders in practice.
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motion parameter optimization and sensor scheduling for the sea wing underwater glider
IEEE Journal of Oceanic Engineering, 2013Co-Authors: Fumin Zhang, Aiqun Zhang, Wenming Jin, Yu TianAbstract:Underwater Gliders adjust buoyancy to generate gliding motion through water columns using a pair of wings. Various types of underwater Gliders have been developed and have been tested as efficient long-distance, long-duration ocean sampling platforms. We introduce the Chinese Sea-Wing underwater glider and develop methods to increase its gliding range by optimizing the steady motion parameters to save energy. The methods are based on a model that relates gliding range to steady gliding motion parameters as well as energy consumption. A sensor scheduling strategy accounts for the distributed features of vertical profiles so that the sampling resolution is adjusted to reduce energy consumption of sensing. The effect of the proposed methods to increase gliding range is evaluated on the Sea-Wing glider. The proposed methods may be applicable to other types of underwater Gliders.
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peer reviewed technical communication motion parameter optimization and sensor scheduling for the sea wing underwater glider
2013Co-Authors: Fumin Zhang, Aiqun Zhang, Wenming Jin, Yu TianAbstract:Underwater Gliders adjust buoyancy to generate gliding motion through water columns using a pair of wings. Various types of underwater Gliders have been developed and have been tested as efficient long-distance, long-duration ocean sampling platforms. We introduce the Chinese Sea-Wing under- water glider and develop methods to increase its gliding range by optimizing the steady motion parameters to save energy. The methods are based on a model that relates gliding range to steady gliding motion parameters as well as energy consumption. A sensor scheduling strategy accounts for the distributed features of vertical profiles so that the sampling resolution is adjusted to reduce energy consumption of sensing. The effect of the proposed methods to increase gliding range is evaluated on the Sea-Wing glider. The proposed methods may be applicable to other types of underwater Gliders.
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real time modelling of tidal current for navigating underwater glider sensing networks
Procedia Computer Science, 2012Co-Authors: Xiaolin Liang, Dongsik Chang, Fumin ZhangAbstract:Ocean models that are able to provide accurate and real-time prediction of ocean currents will improve the performance of glider navigation. In this paper, we propose a novel approach to compute a model for ocean currents at higher resolution than existing approaches. By focusing on a small area and incorporating measurements from multiple Gliders, we are able to perform real-time computation of the model, which can be used to improve performance of underwater glider navigation in the ocean. Our model uses a lower resolution, larger scale dataset generated from existing models to initialize the computation. We have also demonstrated incorporating data streams from high frequency (HF) radar measurements of surface currents. Glider navigation performance using the proposed ocean currents model is demonstrated in a simulated flow field based on data collected off the coast of Georgia, USA.
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cooperative control for ocean sampling the glider coordinated control system
IEEE Transactions on Control Systems and Technology, 2008Co-Authors: Derek A Paley, Fumin Zhang, Naomi Ehrich LeonardAbstract:The glider coordinated control system (GCCS) uses a detailed glider model for prediction and a simple particle model for planning to steer a fleet of underwater Gliders to a set of coordinated trajectories. The GCCS also serves as a simulation testbed for the design and evaluation of multivehicle control laws. In this brief, we describe the GCCS and present experimental results for a virtual deployment in Monterey Bay, CA and a real deployment in Buzzards Bay, MA.
Damien Guihen - One of the best experts on this subject based on the ideXlab platform.
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an assessment of the use of ocean Gliders to undertake acoustic measurements of zooplankton the distribution and density of antarctic krill euphausia superba in the weddell sea
Limnology and Oceanography-methods, 2014Co-Authors: Damien Guihen, Sophie Fielding, Eugene J Murphy, Karen J Heywood, G GriffithsAbstract:A calibrated 120 kHz single-beam echo-sounder was integrated into an ocean glider and deployed in the Weddell Sea, Southern Ocean. The glider was deployed for two short periods in January 2012, in separate survey boxes on the continental shelf to the east of the Antarctic Peninsula, to assess the distribution of Antarctic krill (Euphausia superba). During the glider missions, a research vessel undertook acoustic transects using a calibrated, hull-mounted, multi-frequency echo-sounder. Net hauls were taken to validate acoustic targets and parameterize acoustic models. Krill targets were identified using a thresholded schools analysis technique (SHAPES), and acoustic data were converted to krill density using the stochastic distorted-wave Born approximation (SDWBA) target strength model. A sensitivity analysis of glider pitch and roll indicated that, if not taken into account, glider orientation can impact density estimates by up to 8-fold. Glider-based, echo-sounder–derived krill density profiles for the two survey boxes showed features coherent with ship-borne measurements, with peak densities in both boxes around a depth of 60 m. Monte Carlo simulation of glider subsampling of ship-borne data showed no significant difference from observed profiles. Simulated glider dives required at least an order of magnitude more time than the ship to similarly estimate the abundance of krill within the sample regions. These analyses highlight the need for suitable sampling strategies for glider-based observations and are our first steps toward using autonomous underwater vehicles for ecosystem assessment and long-term monitoring. With appropriate survey design, Gliders can be used for estimating krill distribution and abundance.
