Pub Date : 2011-03-20DOI: 10.1109/CWTM.2011.5759549
J. Dugan, C. Piotrowski
Airborne time series imagery is used to measure frequency-wavenumber spectra of gravity waves, accurately locating the dispersion surface to retrieve water depths and currents. In shallow water, the same frequency-wavenumber spectra often exhibit an ‘advective surface’ caused by flow-induced transport of sediment variations indicative of partly mixed water masses having different sediment loads. The orientation of this spectral surface provides the ‘mean’ current associated with this advection and this value agrees, to within a few percent, with the gravity wave Doppler when both wave and advective signatures are present. This paper describes our attempt to use these same image data to measure the turbulent velocities associated with flows in moderately shallow water found in the near-shore ocean and estuaries. We present examples of turbulent eddy features and demonstrate that the image data are consistent with a Kolmogorov inertial range cascade. We have attempted to measure the short wavelength (<30 m), smaller magnitude current variations in these flows by two separate methods, although we have not been successful in unambiguously quantifying them to date. Our experimental data do, however, provide us with a clear idea of the precision that is necessary to accomplish this in our space-time image data.
{"title":"EO observations of currents and turbulence via mixing of sediment load variations","authors":"J. Dugan, C. Piotrowski","doi":"10.1109/CWTM.2011.5759549","DOIUrl":"https://doi.org/10.1109/CWTM.2011.5759549","url":null,"abstract":"Airborne time series imagery is used to measure frequency-wavenumber spectra of gravity waves, accurately locating the dispersion surface to retrieve water depths and currents. In shallow water, the same frequency-wavenumber spectra often exhibit an ‘advective surface’ caused by flow-induced transport of sediment variations indicative of partly mixed water masses having different sediment loads. The orientation of this spectral surface provides the ‘mean’ current associated with this advection and this value agrees, to within a few percent, with the gravity wave Doppler when both wave and advective signatures are present. This paper describes our attempt to use these same image data to measure the turbulent velocities associated with flows in moderately shallow water found in the near-shore ocean and estuaries. We present examples of turbulent eddy features and demonstrate that the image data are consistent with a Kolmogorov inertial range cascade. We have attempted to measure the short wavelength (<30 m), smaller magnitude current variations in these flows by two separate methods, although we have not been successful in unambiguously quantifying them to date. Our experimental data do, however, provide us with a clear idea of the precision that is necessary to accomplish this in our space-time image data.","PeriodicalId":345178,"journal":{"name":"2011 IEEE/OES 10th Current, Waves and Turbulence Measurements (CWTM)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125755992","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 : 2011-03-20DOI: 10.1109/CWTM.2011.5759559
R. Craig, C. Loadman, B. Clement, P. Rusello, E. Siegel
Pulse-to-pulse coherent Doppler sonar systems have been commercially available for almost two decades now. These systems provide non-intrusive, high accuracy, low noise data in difficult environments. Pulse coherent profilers are also capable of measuring very small cell sizes and provide far more details of flow than standard Doppler systems. Multi-beam bi-static profiling systems allow measurements of velocity over a specified range of cells with each beam providing data from closely spaced measurement volumes, thereby removing the need for assumptions of flow homogeneity as required for mono-static systems with diverging beams. While a few bi-static profiling prototype systems have been demonstrated, there have been no commercial platforms available that provide a cost-effective, turn-key solution for providing three component data profiles with accompanying display and processing software tools. This paper will describe one such system, the Nortek Vectrino-II. A description of the instrument hardware and software capabilities will be followed by a discussion of some of the novel features and algorithms used by the instrument. Tow tank data and comparisons with a PIV system will be presented.
{"title":"Characterization and testing of a new bistatic profiling acoustic Doppler velocimeter: The Vectrino-II","authors":"R. Craig, C. Loadman, B. Clement, P. Rusello, E. Siegel","doi":"10.1109/CWTM.2011.5759559","DOIUrl":"https://doi.org/10.1109/CWTM.2011.5759559","url":null,"abstract":"Pulse-to-pulse coherent Doppler sonar systems have been commercially available for almost two decades now. These systems provide non-intrusive, high accuracy, low noise data in difficult environments. Pulse coherent profilers are also capable of measuring very small cell sizes and provide far more details of flow than standard Doppler systems. Multi-beam bi-static profiling systems allow measurements of velocity over a specified range of cells with each beam providing data from closely spaced measurement volumes, thereby removing the need for assumptions of flow homogeneity as required for mono-static systems with diverging beams. While a few bi-static profiling prototype systems have been demonstrated, there have been no commercial platforms available that provide a cost-effective, turn-key solution for providing three component data profiles with accompanying display and processing software tools. This paper will describe one such system, the Nortek Vectrino-II. A description of the instrument hardware and software capabilities will be followed by a discussion of some of the novel features and algorithms used by the instrument. Tow tank data and comparisons with a PIV system will be presented.","PeriodicalId":345178,"journal":{"name":"2011 IEEE/OES 10th Current, Waves and Turbulence Measurements (CWTM)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115205687","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 : 2011-03-20DOI: 10.1109/CWTM.2011.5759548
S. Woods, W. Hou, W. Goode, E. Jarosz, A. Weidemann
It has long been acknowledged that turbulence affects propagation of light in the ocean. Physically, this is because turbulent inhomogeneities of the flow are associated with fluctuations in temperature and salinity. Variations in these passive scalars alter the water density, inducing variations in the refractive index, which result in near-forward scattering from turbulent inhomogeneities. In applications such as underwater imaging, the near-forward scattering from turbulence becomes a limiting factor over longer ranges and under conditions of stronger turbulence. The magnitude of this degrading effect depends upon the underwater environment, and can rapidly degrade the quality of underwater imaging under certain conditions. Overcoming this degradation through enhancement of imaging systems and post processing is important for such applications as diving, navigation, robotics, communication and target and mine detection and identification. To investigate the impact of turbulence upon underwater imaging and to compare with our previously developed model, quantified observation of the image degradation concurrent with characterization of the turbulent flow is necessary, spanning a variety of turbulent strengths. Therefore, we present field measurements of turbulence from the Skaneateles Optical Turbulence Exercise (SOTEX, July 2010), during which images of a target were collected over a 5 m path length at various depths in the water column, concurrent with profiles of the turbulent strength, optical properties, temperature, and conductivity. Turbulence was characterized by the turbulent kinetic energy dissipation (TKED) and thermal dissipation (TD) rates, which were obtained in close proximity using both a Rockland Scientific Vertical Microstructure Profiler (VMP) and a Nortek Vector velocimeter in combination with a PME CT sensor. While the two instrumental setups demonstrate reasonable agreement, some irregularities highlight the difficulties of accurately quantifying the desired parameters, which are likely associated with the spatial and temporal variability of the turbulence field. Supplementary measurements with the Vector/CT in a controlled laboratory convective tank will shed additional light on the quantitative relationship between image degradation and turbulence strength.
{"title":"Measurements of turbulence for quantifying the impact of turbulence on underwater imaging","authors":"S. Woods, W. Hou, W. Goode, E. Jarosz, A. Weidemann","doi":"10.1109/CWTM.2011.5759548","DOIUrl":"https://doi.org/10.1109/CWTM.2011.5759548","url":null,"abstract":"It has long been acknowledged that turbulence affects propagation of light in the ocean. Physically, this is because turbulent inhomogeneities of the flow are associated with fluctuations in temperature and salinity. Variations in these passive scalars alter the water density, inducing variations in the refractive index, which result in near-forward scattering from turbulent inhomogeneities. In applications such as underwater imaging, the near-forward scattering from turbulence becomes a limiting factor over longer ranges and under conditions of stronger turbulence. The magnitude of this degrading effect depends upon the underwater environment, and can rapidly degrade the quality of underwater imaging under certain conditions. Overcoming this degradation through enhancement of imaging systems and post processing is important for such applications as diving, navigation, robotics, communication and target and mine detection and identification. To investigate the impact of turbulence upon underwater imaging and to compare with our previously developed model, quantified observation of the image degradation concurrent with characterization of the turbulent flow is necessary, spanning a variety of turbulent strengths. Therefore, we present field measurements of turbulence from the Skaneateles Optical Turbulence Exercise (SOTEX, July 2010), during which images of a target were collected over a 5 m path length at various depths in the water column, concurrent with profiles of the turbulent strength, optical properties, temperature, and conductivity. Turbulence was characterized by the turbulent kinetic energy dissipation (TKED) and thermal dissipation (TD) rates, which were obtained in close proximity using both a Rockland Scientific Vertical Microstructure Profiler (VMP) and a Nortek Vector velocimeter in combination with a PME CT sensor. While the two instrumental setups demonstrate reasonable agreement, some irregularities highlight the difficulties of accurately quantifying the desired parameters, which are likely associated with the spatial and temporal variability of the turbulence field. Supplementary measurements with the Vector/CT in a controlled laboratory convective tank will shed additional light on the quantitative relationship between image degradation and turbulence strength.","PeriodicalId":345178,"journal":{"name":"2011 IEEE/OES 10th Current, Waves and Turbulence Measurements (CWTM)","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122016507","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 : 2011-03-20DOI: 10.1109/CWTM.2011.5759552
A. Thurnherr
Vertical velocity is important for ocean dynamics on a vast range of scales, from isotropic turbulence to the global overturning circulation, and directly affects transport of biogeochemical tracers. In spite of this importance, vertical-velocity measurements in the ocean are scarce. In an effort to remedy this situation, a new method has been developed to obtain full-depth profiles of vertical velocity from data collected with standard Lowered Acoustic Doppler Current Profiler (LADCP) systems, such as the ones used during the CLIVAR repeat hydrography sections. Data from LADCP systems, which consist of CTDs and ADCPs lowered on hydrographic wires, are typically processed to obtain full-depth profiles of horizontal velocity. The fundamental difficulty underlying LADCP data processing is that the velocity measurements are relative to the moving instrument package. In order to obtain absolute ocean velocities, the instrument motion must be removed from each ADCP velocity profile. One method for achieving this consists in vertically integrating vertical shear of velocity, which can easily be obtained from LADCP velocity records and is independent of instrument motion, and to reference the resulting baroclinic velocity profiles with external constraints, such as package motion derived from bottom tracking. While this method can, in principle, be applied both to horizontal and to vertical velocity data the resulting uncertainties of ≈3–5 cm·s−1 are larger than the typical signal expected for vertical velocity in the ocean.
{"title":"Vertical velocity from LADCP data","authors":"A. Thurnherr","doi":"10.1109/CWTM.2011.5759552","DOIUrl":"https://doi.org/10.1109/CWTM.2011.5759552","url":null,"abstract":"Vertical velocity is important for ocean dynamics on a vast range of scales, from isotropic turbulence to the global overturning circulation, and directly affects transport of biogeochemical tracers. In spite of this importance, vertical-velocity measurements in the ocean are scarce. In an effort to remedy this situation, a new method has been developed to obtain full-depth profiles of vertical velocity from data collected with standard Lowered Acoustic Doppler Current Profiler (LADCP) systems, such as the ones used during the CLIVAR repeat hydrography sections. Data from LADCP systems, which consist of CTDs and ADCPs lowered on hydrographic wires, are typically processed to obtain full-depth profiles of horizontal velocity. The fundamental difficulty underlying LADCP data processing is that the velocity measurements are relative to the moving instrument package. In order to obtain absolute ocean velocities, the instrument motion must be removed from each ADCP velocity profile. One method for achieving this consists in vertically integrating vertical shear of velocity, which can easily be obtained from LADCP velocity records and is independent of instrument motion, and to reference the resulting baroclinic velocity profiles with external constraints, such as package motion derived from bottom tracking. While this method can, in principle, be applied both to horizontal and to vertical velocity data the resulting uncertainties of ≈3–5 cm·s−1 are larger than the typical signal expected for vertical velocity in the ocean.","PeriodicalId":345178,"journal":{"name":"2011 IEEE/OES 10th Current, Waves and Turbulence Measurements (CWTM)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123963759","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 : 2011-03-20DOI: 10.1109/CWTM.2011.5759522
N. Garfield, M. Hubbard, J. Pettigrew
The selection of San Francisco Bay as the venue for the 2013 America's Cup competition provides the opportunity to highlight the technology available for measuring surface currents over the entire proposed racecourse and to deliver current estimates in near real-time. Using an array of CODAR Ocean Sensors SeaSonde 42 MHz systems, the currents in Central San Francisco Bay can be mapped in high spatial resolution with a temporal resolution of 30 minutes.
{"title":"Providing SeaSonde high-resolution surface currents for the America's Cup","authors":"N. Garfield, M. Hubbard, J. Pettigrew","doi":"10.1109/CWTM.2011.5759522","DOIUrl":"https://doi.org/10.1109/CWTM.2011.5759522","url":null,"abstract":"The selection of San Francisco Bay as the venue for the 2013 America's Cup competition provides the opportunity to highlight the technology available for measuring surface currents over the entire proposed racecourse and to deliver current estimates in near real-time. Using an array of CODAR Ocean Sensors SeaSonde 42 MHz systems, the currents in Central San Francisco Bay can be mapped in high spatial resolution with a temporal resolution of 30 minutes.","PeriodicalId":345178,"journal":{"name":"2011 IEEE/OES 10th Current, Waves and Turbulence Measurements (CWTM)","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125514372","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 : 2011-03-20DOI: 10.1109/CWTM.2011.5759525
G. Voulgaris, Nirnimesh Kumar, K. Gurgel, J. Warner, J. List
The majority of High Frequency (HF) radars used worldwide operate at medium to high frequencies (8 to 30 MHz) providing spatial resolutions ranging from 3 to 1.5 km and ranges from 150 to 50 km. This paper presents results from the deployment of a single Very High Frequency (VHF, 48 MHz) WEllen RAdar (WERA) radar with spatial resolution of 150 m and range 10–15 km, used in the nearshore off Cape Hatteras, NC, USA. It consisted of a linear array of 12 antennas operating in beam forming mode. Radial velocities were estimated from radar backscatter for a variety of wind and nearshore wave conditions. A methodology similar to that used for converting acoustically derived beam velocities to an orthogonal system is presented for obtaining 2-D current fields from a single station. The accuracy of the VHF radar-derived radial velocities is examined using a new statistical technique that evaluates the system over the range of measured velocities. The VHF radar velocities showed a bias of 3 to 7 cm/s over the experimental period explainable by the differences in radar penetration and in-situ measurement height. The 2-D current field shows good agreement with the in-situ measurements. Deviations and inaccuracies are well explained by the geometric dilution analysis.
{"title":"2-D inner-shelf current observations from a single VHF WEllen RAdar (WERA) station","authors":"G. Voulgaris, Nirnimesh Kumar, K. Gurgel, J. Warner, J. List","doi":"10.1109/CWTM.2011.5759525","DOIUrl":"https://doi.org/10.1109/CWTM.2011.5759525","url":null,"abstract":"The majority of High Frequency (HF) radars used worldwide operate at medium to high frequencies (8 to 30 MHz) providing spatial resolutions ranging from 3 to 1.5 km and ranges from 150 to 50 km. This paper presents results from the deployment of a single Very High Frequency (VHF, 48 MHz) WEllen RAdar (WERA) radar with spatial resolution of 150 m and range 10–15 km, used in the nearshore off Cape Hatteras, NC, USA. It consisted of a linear array of 12 antennas operating in beam forming mode. Radial velocities were estimated from radar backscatter for a variety of wind and nearshore wave conditions. A methodology similar to that used for converting acoustically derived beam velocities to an orthogonal system is presented for obtaining 2-D current fields from a single station. The accuracy of the VHF radar-derived radial velocities is examined using a new statistical technique that evaluates the system over the range of measured velocities. The VHF radar velocities showed a bias of 3 to 7 cm/s over the experimental period explainable by the differences in radar penetration and in-situ measurement height. The 2-D current field shows good agreement with the in-situ measurements. Deviations and inaccuracies are well explained by the geometric dilution analysis.","PeriodicalId":345178,"journal":{"name":"2011 IEEE/OES 10th Current, Waves and Turbulence Measurements (CWTM)","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131240292","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 : 2011-03-20DOI: 10.1109/CWTM.2011.5759520
D. Savidge, J. Amft, A. Gargett, M. Archer, D. Conley, G. Voulgaris, L. Wyatt, K. Gurgel
Since April 2006, long range (8.3MHz) WERA HF radars have been operated on the Southeastern United States coastline, as part of the U.S. Integrated Ocean Observing System (IOOS) and in particular the national HF Radar network. These radars measure currents operationally, and waves and winds experimentally across the wide continental shelf of Georgia (GA) and South Carolina (SC). Half-hourly data at 3km horizontal resolution are acquired to a range of approximately 200 km, providing measurements across the wide continental shelf and into the adjacent Gulf Stream at the shelf edge. Radar performance in range and quality is discussed. Ease in siting of these space and cable intensive systems along populated coastlines, and the feasibility of their operation by non-radar specialists is also briefly discussed.
{"title":"Assessment of WERA long-range HF-radar performance from the user's perspective","authors":"D. Savidge, J. Amft, A. Gargett, M. Archer, D. Conley, G. Voulgaris, L. Wyatt, K. Gurgel","doi":"10.1109/CWTM.2011.5759520","DOIUrl":"https://doi.org/10.1109/CWTM.2011.5759520","url":null,"abstract":"Since April 2006, long range (8.3MHz) WERA HF radars have been operated on the Southeastern United States coastline, as part of the U.S. Integrated Ocean Observing System (IOOS) and in particular the national HF Radar network. These radars measure currents operationally, and waves and winds experimentally across the wide continental shelf of Georgia (GA) and South Carolina (SC). Half-hourly data at 3km horizontal resolution are acquired to a range of approximately 200 km, providing measurements across the wide continental shelf and into the adjacent Gulf Stream at the shelf edge. Radar performance in range and quality is discussed. Ease in siting of these space and cable intensive systems along populated coastlines, and the feasibility of their operation by non-radar specialists is also briefly discussed.","PeriodicalId":345178,"journal":{"name":"2011 IEEE/OES 10th Current, Waves and Turbulence Measurements (CWTM)","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131518998","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 : 2011-03-20DOI: 10.1109/CWTM.2011.5759557
J. Dillon, L. Zedel, A. Hay
Pulse-to-pulse coherent Doppler sonar is capable of measuring simultaneous profiles of veloctiy and sediment concentration in turbulent suspensions. However, the presence of measurement noise introduces biases when turbulence statistics are calculated from the fluctuating component of velocity. In order to further develop coherent Doppler sonar as a tool for turbulence measurement, a velocity estimator based on Maximum A Posteriori (MAP) estimation has been developed. The estimator optimally combines measurements from multiple acoustic carrier frequencies and multiple transducers. Data fusion is achieved using a probabilistic approach, whereby measurements are combined numerically to derive a velocity likelihood function. The only parameter which must be chosen by the user is a smoothing factor that describes the diffusion of velocity (in a probabilistic sense) from sample to sample in time. A method is presented for automatically determining the smoothing parameter from examination of the spectrum of a representative segment of the measurement time series. Results are presented from a laboratory turbulent jet in which velocity was measured simultaneously with multi-frequency coherent Doppler sonar and particle image velocimetry (PIV). Time series and turbulence spectra from PIV are compared to those obtained with conventional Doppler signal processing and MAP velocity estimation. It is shown that automatic tuning of the estimator results in a velocity time series where measurement noise is suppressed while high frequency turbulent fluctuations are retained.
{"title":"Automatic tuning of a velocity estimator for pulse-to-pulse coherent Doppler sonar","authors":"J. Dillon, L. Zedel, A. Hay","doi":"10.1109/CWTM.2011.5759557","DOIUrl":"https://doi.org/10.1109/CWTM.2011.5759557","url":null,"abstract":"Pulse-to-pulse coherent Doppler sonar is capable of measuring simultaneous profiles of veloctiy and sediment concentration in turbulent suspensions. However, the presence of measurement noise introduces biases when turbulence statistics are calculated from the fluctuating component of velocity. In order to further develop coherent Doppler sonar as a tool for turbulence measurement, a velocity estimator based on Maximum A Posteriori (MAP) estimation has been developed. The estimator optimally combines measurements from multiple acoustic carrier frequencies and multiple transducers. Data fusion is achieved using a probabilistic approach, whereby measurements are combined numerically to derive a velocity likelihood function. The only parameter which must be chosen by the user is a smoothing factor that describes the diffusion of velocity (in a probabilistic sense) from sample to sample in time. A method is presented for automatically determining the smoothing parameter from examination of the spectrum of a representative segment of the measurement time series. Results are presented from a laboratory turbulent jet in which velocity was measured simultaneously with multi-frequency coherent Doppler sonar and particle image velocimetry (PIV). Time series and turbulence spectra from PIV are compared to those obtained with conventional Doppler signal processing and MAP velocity estimation. It is shown that automatic tuning of the estimator results in a velocity time series where measurement noise is suppressed while high frequency turbulent fluctuations are retained.","PeriodicalId":345178,"journal":{"name":"2011 IEEE/OES 10th Current, Waves and Turbulence Measurements (CWTM)","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131744149","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 : 2011-03-20DOI: 10.1109/CWTM.2011.5759544
A. Lohrmann, T. Pedersen, S. Nylund, E. Siegel
Nortek provides a combined wave and current profiling instrument in the form of the AWAC. This variant of the traditional ADCP has managed to circumvent the classic limitations of measuring short waves in deep waters by introducing a vertical beam that directly measures the height of the water-air interface (waves) above the instrument. This same vertical beam has also demonstrated that it is capable of measuring the distance to the water-ice interface, and as a result can be used as means to estimate ice draft or ice thickness.
{"title":"Waves in the summer ice in the winter","authors":"A. Lohrmann, T. Pedersen, S. Nylund, E. Siegel","doi":"10.1109/CWTM.2011.5759544","DOIUrl":"https://doi.org/10.1109/CWTM.2011.5759544","url":null,"abstract":"Nortek provides a combined wave and current profiling instrument in the form of the AWAC. This variant of the traditional ADCP has managed to circumvent the classic limitations of measuring short waves in deep waters by introducing a vertical beam that directly measures the height of the water-air interface (waves) above the instrument. This same vertical beam has also demonstrated that it is capable of measuring the distance to the water-ice interface, and as a result can be used as means to estimate ice draft or ice thickness.","PeriodicalId":345178,"journal":{"name":"2011 IEEE/OES 10th Current, Waves and Turbulence Measurements (CWTM)","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130371180","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 : 2011-03-20DOI: 10.1109/CWTM.2011.5759521
K. Laws, J. Vesecky, J. Paduan
Maritime domain awareness is important for coastal nations in terms of applications to coastal conservancy, security, fishery and stewardship of their exclusive economic zones (EEZs). Maritime situational awareness involves knowing the location, speed and bearing of ships and boats in the EEZ. HF radar is a useful tool in providing ship information in real time. It is especially effective when combined with information from ship-borne AIS beacons. Our previously developed HF radar and AIS ship detection models estimate signal to noise ratio (SNR) as a function of range, including ducted propagation for the AIS radio signals. However, ship detection is hampered by false targets related to wave echoes, interference and the high variability of HF echoes from ships. This is due in part to the aspect and frequency dependence of ship radar cross-section and to the presence of clutter bands at known Doppler shifts from both the ground and ocean surfaces. Distinguishing ship echoes from false alarm echoes is significantly aided by identifying radar targets with ship-like behavior. Thus, tracking ships using their HF radar echoes becomes an important means for effectively monitoring the presence of ships in the coastal ocean. We demonstrate the application of Kalman filtering to the ship-tracking problem with examples using data from the COCMP HF radar network along the California coast. As with other radar tracking problems, the Kalman approach proves effective in this application as well.
{"title":"Monitoring coastal vessels for environmental applications: Application of Kalman filtering","authors":"K. Laws, J. Vesecky, J. Paduan","doi":"10.1109/CWTM.2011.5759521","DOIUrl":"https://doi.org/10.1109/CWTM.2011.5759521","url":null,"abstract":"Maritime domain awareness is important for coastal nations in terms of applications to coastal conservancy, security, fishery and stewardship of their exclusive economic zones (EEZs). Maritime situational awareness involves knowing the location, speed and bearing of ships and boats in the EEZ. HF radar is a useful tool in providing ship information in real time. It is especially effective when combined with information from ship-borne AIS beacons. Our previously developed HF radar and AIS ship detection models estimate signal to noise ratio (SNR) as a function of range, including ducted propagation for the AIS radio signals. However, ship detection is hampered by false targets related to wave echoes, interference and the high variability of HF echoes from ships. This is due in part to the aspect and frequency dependence of ship radar cross-section and to the presence of clutter bands at known Doppler shifts from both the ground and ocean surfaces. Distinguishing ship echoes from false alarm echoes is significantly aided by identifying radar targets with ship-like behavior. Thus, tracking ships using their HF radar echoes becomes an important means for effectively monitoring the presence of ships in the coastal ocean. We demonstrate the application of Kalman filtering to the ship-tracking problem with examples using data from the COCMP HF radar network along the California coast. As with other radar tracking problems, the Kalman approach proves effective in this application as well.","PeriodicalId":345178,"journal":{"name":"2011 IEEE/OES 10th Current, Waves and Turbulence Measurements (CWTM)","volume":"123 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2011-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122482182","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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