Pub Date : 2014-09-01DOI: 10.1109/OCEANS.2014.7003217
Donal Kennedy, M. Walsh, B. O’flynn
Commercial wave buoys, while accurate and reliable, utilize high specification components which can render the cost of deployment and maintenance prohibitively high for many applications. This paper describes the deployment of Tyndall Wireless Inertial Measurement Units (WIMUs) as applied to measurement of ocean waves. These inertial measurement units are miniature devices which combine a microcontroller, wireless communication capability, and solidstate MEMS sensors (accelerometer, gyroscope and magnetometer) with specialized algorithms for specific analytical tasks. The deployments include testing on a laboratory based rig and in an artificial wave tank. Sea state parameters are extracted from the inertial data using a zero-crossing method, incorporating two different methodologies with the results of each compared. Height measurement accuracy is shown to be significantly improved over previous studies in this field, with average wave height (Hav) error of less than 1% ±7%.
{"title":"Development of a miniature, low-cost wave measurement solution","authors":"Donal Kennedy, M. Walsh, B. O’flynn","doi":"10.1109/OCEANS.2014.7003217","DOIUrl":"https://doi.org/10.1109/OCEANS.2014.7003217","url":null,"abstract":"Commercial wave buoys, while accurate and reliable, utilize high specification components which can render the cost of deployment and maintenance prohibitively high for many applications. This paper describes the deployment of Tyndall Wireless Inertial Measurement Units (WIMUs) as applied to measurement of ocean waves. These inertial measurement units are miniature devices which combine a microcontroller, wireless communication capability, and solidstate MEMS sensors (accelerometer, gyroscope and magnetometer) with specialized algorithms for specific analytical tasks. The deployments include testing on a laboratory based rig and in an artificial wave tank. Sea state parameters are extracted from the inertial data using a zero-crossing method, incorporating two different methodologies with the results of each compared. Height measurement accuracy is shown to be significantly improved over previous studies in this field, with average wave height (Hav) error of less than 1% ±7%.","PeriodicalId":368693,"journal":{"name":"2014 Oceans - St. John's","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130893285","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 : 2014-09-01DOI: 10.1109/OCEANS.2014.7003120
Yuzhi Zhang, Yi Huang, L. Wan, Hao Zhou, Shengli Zhou, Xiaohong Shen, Haiyan Wang
Multiuser communication has been an important research area of underwater acoustic communications and networking. This paper studies the use of adaptive OFDMA in a multiuser downlink scenario, where a central node sends data to multiple distributed nodes simultaneously. The reduction of channel feedback via clustering and quantization is considered, and an interleaved power-bit loading algorithm is presented to jointly assign the data subcarriers to different users and allocate the power and bits on each subcarrier. Simulation results show the performance improvement due to subcarrier allocation with and without additional power and bit loading. An experiment conducted in a swimming pool illustrates potential benefits and challenges of harvesting the multiuser diversity through adaptive subcarrier allocation.
{"title":"Adaptive OFDMA for downlink underwater acoustic communications","authors":"Yuzhi Zhang, Yi Huang, L. Wan, Hao Zhou, Shengli Zhou, Xiaohong Shen, Haiyan Wang","doi":"10.1109/OCEANS.2014.7003120","DOIUrl":"https://doi.org/10.1109/OCEANS.2014.7003120","url":null,"abstract":"Multiuser communication has been an important research area of underwater acoustic communications and networking. This paper studies the use of adaptive OFDMA in a multiuser downlink scenario, where a central node sends data to multiple distributed nodes simultaneously. The reduction of channel feedback via clustering and quantization is considered, and an interleaved power-bit loading algorithm is presented to jointly assign the data subcarriers to different users and allocate the power and bits on each subcarrier. Simulation results show the performance improvement due to subcarrier allocation with and without additional power and bit loading. An experiment conducted in a swimming pool illustrates potential benefits and challenges of harvesting the multiuser diversity through adaptive subcarrier allocation.","PeriodicalId":368693,"journal":{"name":"2014 Oceans - St. John's","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131294577","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 : 2014-09-01DOI: 10.1109/OCEANS.2014.7003242
C. Merz, K. Main
As fishing has become more industrialized and wild fish stocks increasingly depleted, aquaculture production has grown rapidly to address the shortfalls in capture fisheries and limitations to long-term aquaculture success. One such shortfall is the need to produce a suitable, sustainable, substitute for the capture fishery derived fish meal and oil based fish feeds currently in use, while maintaining the human protein requirements and health benefits of Long Chain (LC) omega-3 oils in farmed fish products. Fish derive the LC omega-3 oils from the food they consume, which ultimately comes from lower trophic level primary producers like microalgae. Using Integrated Aquaculture System (IAS) principles and practices, microalgae (diatoms) can be raised and processed directly for their Algal/Single Cell Oils (SCO), protein, and nutrients. Besides the use as an aquaculture feedstock, microalgae have been investigated for biofuel production because of higher photosynthetic efficiency, higher biomass production, and faster growth compared to other terrestrial energy crops. SCO based carbon-neutral renewable liquid biofuel solutions are currently under investigation but suffer from high production costs. Liquid biofuels have been considered to displace non-renewable, petroleum-derived transport fuels of limited availability which contribute to climate change via greenhouse gas (GHG) emissions. The current high cost constraint of SCO production could be alleviated through explored water-energy-food nexus synergies between the aquaculture and biofuels sector with a concentration on innovations in microalgae/SCO production, harvesting, and processing technologies. Interdisciplinary collaborations between engineers, biologists and chemists are essential for their successful development.
{"title":"Microalgae (diatom) production — The aquaculture and biofuel nexus","authors":"C. Merz, K. Main","doi":"10.1109/OCEANS.2014.7003242","DOIUrl":"https://doi.org/10.1109/OCEANS.2014.7003242","url":null,"abstract":"As fishing has become more industrialized and wild fish stocks increasingly depleted, aquaculture production has grown rapidly to address the shortfalls in capture fisheries and limitations to long-term aquaculture success. One such shortfall is the need to produce a suitable, sustainable, substitute for the capture fishery derived fish meal and oil based fish feeds currently in use, while maintaining the human protein requirements and health benefits of Long Chain (LC) omega-3 oils in farmed fish products. Fish derive the LC omega-3 oils from the food they consume, which ultimately comes from lower trophic level primary producers like microalgae. Using Integrated Aquaculture System (IAS) principles and practices, microalgae (diatoms) can be raised and processed directly for their Algal/Single Cell Oils (SCO), protein, and nutrients. Besides the use as an aquaculture feedstock, microalgae have been investigated for biofuel production because of higher photosynthetic efficiency, higher biomass production, and faster growth compared to other terrestrial energy crops. SCO based carbon-neutral renewable liquid biofuel solutions are currently under investigation but suffer from high production costs. Liquid biofuels have been considered to displace non-renewable, petroleum-derived transport fuels of limited availability which contribute to climate change via greenhouse gas (GHG) emissions. The current high cost constraint of SCO production could be alleviated through explored water-energy-food nexus synergies between the aquaculture and biofuels sector with a concentration on innovations in microalgae/SCO production, harvesting, and processing technologies. Interdisciplinary collaborations between engineers, biologists and chemists are essential for their successful development.","PeriodicalId":368693,"journal":{"name":"2014 Oceans - St. John's","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132080456","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 : 2014-09-01DOI: 10.1109/OCEANS.2014.7003288
Xin Cheng, Azizur Rahman
A liquefied natural gas (LNG) carrier is designed to transport LNG over a long distance. During transportation, the leakage of boil-off gas (BOG) along with poor ventilation can pose an explosion risk. The traditional method for dealing with the BOG is to burn the gas to power the ship. As an alternative method, re-liquefaction plants on board re-liquefy the vapours back to the cargo tanks. This project will characterize the technical issues associated with fire protection in a confined space where LNG boil-off re-liquefaction takes place and will demonstrate what the appropriate ventilation rate in an emergency is. In addition, the CFD software (ANSYS CFX) is applied to simulate the ventilation and burning of boil-off gas in the on board re-liquefaction plant to ensure the safety of the cargo tanks for the worst case scenario. The traditional method for dealing with the boil-off gas (BOG) on board an LNG carrier is to burn the gas to power the ship. As an alternative method, re-liquefaction plants on board re-liquefy the vapour back to the cargo tanks [1]. In the last few years, the introduction of LNG re-liquefaction systems has given ship owners a choice of fuels and provides engine redundancy. Nevertheless, flammable natural gas is processed in both methods. Due to the inherent properties of a ship's structure, the re-liquefaction system, gas combustion unit, pipelines, etc. are located in the space enclosed under the deck. Under certain circumstances the leakage of natural gas, along with poor ventilation, can pose an explosion risk. Unfortunately, limited industry codes have been developed for fire protection in the cabin where the innovative LNG re-liquefaction system is located. The purpose of this project is to demonstrate the leaking and burning of boil-off gas in the on board re-liquefaction plant to ensure the safety of the cargo tanks for the worst case scenario by using CFD simulation software.
{"title":"BOG ventilation and combustion in re-liquefaction plants of LNG carriers","authors":"Xin Cheng, Azizur Rahman","doi":"10.1109/OCEANS.2014.7003288","DOIUrl":"https://doi.org/10.1109/OCEANS.2014.7003288","url":null,"abstract":"A liquefied natural gas (LNG) carrier is designed to transport LNG over a long distance. During transportation, the leakage of boil-off gas (BOG) along with poor ventilation can pose an explosion risk. The traditional method for dealing with the BOG is to burn the gas to power the ship. As an alternative method, re-liquefaction plants on board re-liquefy the vapours back to the cargo tanks. This project will characterize the technical issues associated with fire protection in a confined space where LNG boil-off re-liquefaction takes place and will demonstrate what the appropriate ventilation rate in an emergency is. In addition, the CFD software (ANSYS CFX) is applied to simulate the ventilation and burning of boil-off gas in the on board re-liquefaction plant to ensure the safety of the cargo tanks for the worst case scenario. The traditional method for dealing with the boil-off gas (BOG) on board an LNG carrier is to burn the gas to power the ship. As an alternative method, re-liquefaction plants on board re-liquefy the vapour back to the cargo tanks [1]. In the last few years, the introduction of LNG re-liquefaction systems has given ship owners a choice of fuels and provides engine redundancy. Nevertheless, flammable natural gas is processed in both methods. Due to the inherent properties of a ship's structure, the re-liquefaction system, gas combustion unit, pipelines, etc. are located in the space enclosed under the deck. Under certain circumstances the leakage of natural gas, along with poor ventilation, can pose an explosion risk. Unfortunately, limited industry codes have been developed for fire protection in the cabin where the innovative LNG re-liquefaction system is located. The purpose of this project is to demonstrate the leaking and burning of boil-off gas in the on board re-liquefaction plant to ensure the safety of the cargo tanks for the worst case scenario by using CFD simulation software.","PeriodicalId":368693,"journal":{"name":"2014 Oceans - St. John's","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133882805","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 : 2014-09-01DOI: 10.1109/OCEANS.2014.7003023
A. Gunes, M. B. Guldogan, A. Bereketli
Underwater acoustic vector sensors (AVS) are devices which can measure scalar pressure and three dimensional acceleration or particle velocity with only one sensor. Direction of an acoustic target can be estimated by these four measured scalar values. Techniques based on either closed-form expressions or beamforming can be carried out for direction finding by using the axial projections of the gradient vector of the pressure from the target. In this work, the performances of direction of arrival (DOA) estimation techniques for a single underwater AVS are analyzed in detail under the effects of various error sources such as imperfect projections and ambient noise.
{"title":"A comparative study on the performances of the DF techniques using a single acoustic vector sensor","authors":"A. Gunes, M. B. Guldogan, A. Bereketli","doi":"10.1109/OCEANS.2014.7003023","DOIUrl":"https://doi.org/10.1109/OCEANS.2014.7003023","url":null,"abstract":"Underwater acoustic vector sensors (AVS) are devices which can measure scalar pressure and three dimensional acceleration or particle velocity with only one sensor. Direction of an acoustic target can be estimated by these four measured scalar values. Techniques based on either closed-form expressions or beamforming can be carried out for direction finding by using the axial projections of the gradient vector of the pressure from the target. In this work, the performances of direction of arrival (DOA) estimation techniques for a single underwater AVS are analyzed in detail under the effects of various error sources such as imperfect projections and ambient noise.","PeriodicalId":368693,"journal":{"name":"2014 Oceans - St. John's","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122501948","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 : 2014-09-01DOI: 10.1109/OCEANS.2014.7003093
A. Turetta, G. Casalino, E. Simetti, Alessandro Sperindé, Sandro Torelli
The use of Long Baseline (LBL) systems for localizing underwater vehicles is quite consolidated, as they guarantee a good nominal accuracy, not dependent on the operative depth and almost constant at any point inside the area delimited by the transponders. However the real achievable accuracy can be affected by different factors, mainly related with the knowledge of some environmental parameters (like the speed of sound), the quality of the employed instrumentations, and the level of calibration of the system, after its deployment in water. The paper specifically addresses the accuracy of a LBL-based localization procedure and presents the results of an error budget analysis. For each considered error source, a closed form of the induced localization error is derived and discussed with the intent of enabling the characterization of the real obtainable accuracy within a typical application. The overall study is finally supported and validated by a detailed set of simulative results.
{"title":"Analysis of the accuracy of a LBL-based underwater localization procedure","authors":"A. Turetta, G. Casalino, E. Simetti, Alessandro Sperindé, Sandro Torelli","doi":"10.1109/OCEANS.2014.7003093","DOIUrl":"https://doi.org/10.1109/OCEANS.2014.7003093","url":null,"abstract":"The use of Long Baseline (LBL) systems for localizing underwater vehicles is quite consolidated, as they guarantee a good nominal accuracy, not dependent on the operative depth and almost constant at any point inside the area delimited by the transponders. However the real achievable accuracy can be affected by different factors, mainly related with the knowledge of some environmental parameters (like the speed of sound), the quality of the employed instrumentations, and the level of calibration of the system, after its deployment in water. The paper specifically addresses the accuracy of a LBL-based localization procedure and presents the results of an error budget analysis. For each considered error source, a closed form of the induced localization error is derived and discussed with the intent of enabling the characterization of the real obtainable accuracy within a typical application. The overall study is finally supported and validated by a detailed set of simulative results.","PeriodicalId":368693,"journal":{"name":"2014 Oceans - St. John's","volume":"335 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122510730","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 : 2014-09-01DOI: 10.1109/OCEANS.2014.7003030
Laura J. Johnson, R. Green, M. Leeson
Underwater optical wireless has two distinct modes of communication depending on the choice of transmitter technology; short-ranged dispersive LED links (<;20m) and longdistance, narrow laser links. In both cases, existing propagation models use a single-value estimation of attenuation but this is not accurate for the latter. Changes in attenuation are caused by variable composition where the natural Gaussian profile of chlorophyll concentration with depth is the biggest contributing factor. With this in mind, this research looks at how varying the orientation of communication affects the average transmission for longer ranged underwater optical links. This is repeated for areas with low, medium and high levels of surface turbidity at 50m depth increments. Highest attenuation in found in links which have the largest portion transmitted through a chlorophyll peak, this occurs between 15-45° for both high and mid turbidity levels which correspond to the peaks below 0m and 50m respectively. This study also calculates how seawater refractive index gradients with depth alter the beam direction for different optical wireless links at angles to the vertical. It is found that angles closer to the vertical undergo higher displacements from their receivers as the gradient over which they are communicating is greater.
{"title":"The impact of link orientation in underwater optical wireless communication systems","authors":"Laura J. Johnson, R. Green, M. Leeson","doi":"10.1109/OCEANS.2014.7003030","DOIUrl":"https://doi.org/10.1109/OCEANS.2014.7003030","url":null,"abstract":"Underwater optical wireless has two distinct modes of communication depending on the choice of transmitter technology; short-ranged dispersive LED links (<;20m) and longdistance, narrow laser links. In both cases, existing propagation models use a single-value estimation of attenuation but this is not accurate for the latter. Changes in attenuation are caused by variable composition where the natural Gaussian profile of chlorophyll concentration with depth is the biggest contributing factor. With this in mind, this research looks at how varying the orientation of communication affects the average transmission for longer ranged underwater optical links. This is repeated for areas with low, medium and high levels of surface turbidity at 50m depth increments. Highest attenuation in found in links which have the largest portion transmitted through a chlorophyll peak, this occurs between 15-45° for both high and mid turbidity levels which correspond to the peaks below 0m and 50m respectively. This study also calculates how seawater refractive index gradients with depth alter the beam direction for different optical wireless links at angles to the vertical. It is found that angles closer to the vertical undergo higher displacements from their receivers as the gradient over which they are communicating is greater.","PeriodicalId":368693,"journal":{"name":"2014 Oceans - St. John's","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124013649","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 : 2014-09-01DOI: 10.1109/OCEANS.2014.7003058
Anthony H. Sylvester, J. Delmerico, A. Trimble, B. Bingham
Two feedback controllers are presented that utilize data averaging and model-based estimation to offset the effects of sensor noise and achieve precise control of an autonomous underwater vehicle (AUV) variable buoyancy system (VBS). Operation of the bottom skimming AUV requires a constant reaction force between the seabed and the vehicle. While performing a mission, variable seafloor topography and a changing payload weight requires the use of a VBS to maintain the reaction force. Two traits of the VBS system that make this a challenging problem are the presence of sensor noise and fast on/off actuation relative to the sensor update rate. It was discovered that both controllers function under these conditions but the model-based controller provides more precise control of the system. This paper presents a comparison between these two control algorithms based on both simulation results and field experiments in a coastal environment.
{"title":"Variable buoyancy control for a bottom skimming autonomous underwater vehicle","authors":"Anthony H. Sylvester, J. Delmerico, A. Trimble, B. Bingham","doi":"10.1109/OCEANS.2014.7003058","DOIUrl":"https://doi.org/10.1109/OCEANS.2014.7003058","url":null,"abstract":"Two feedback controllers are presented that utilize data averaging and model-based estimation to offset the effects of sensor noise and achieve precise control of an autonomous underwater vehicle (AUV) variable buoyancy system (VBS). Operation of the bottom skimming AUV requires a constant reaction force between the seabed and the vehicle. While performing a mission, variable seafloor topography and a changing payload weight requires the use of a VBS to maintain the reaction force. Two traits of the VBS system that make this a challenging problem are the presence of sensor noise and fast on/off actuation relative to the sensor update rate. It was discovered that both controllers function under these conditions but the model-based controller provides more precise control of the system. This paper presents a comparison between these two control algorithms based on both simulation results and field experiments in a coastal environment.","PeriodicalId":368693,"journal":{"name":"2014 Oceans - St. John's","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127907120","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 : 2014-09-01DOI: 10.1109/OCEANS.2014.7003157
Ying Zhang, Jiamin Huang, Hangfang Zhao, Wen Xu
Acoustic mapping of ocean currents with Distributed Networked Underwater Sensors (DNUS) system is an effective and energy-saving technique for monitoring oceanographic environments. Unlike the common acoustic tomography methods, this new approach can locally reconstruct ocean currents using data between neighboring sensors. Considering that ocean currents are highly correlated during a short time interval, this paper develops a Kalman filter based tracking approach to improve the DNUS-based ocean current estimation. A 2-D ocean model is used to generate synthetic observational data. The simulation results show that, with the information of the previous ocean current estimates introduced, the proposed method can outperform the traditional current mapping method with DNUS-type system.
{"title":"Kalman tracking of ocean current field based on distributed sensor network","authors":"Ying Zhang, Jiamin Huang, Hangfang Zhao, Wen Xu","doi":"10.1109/OCEANS.2014.7003157","DOIUrl":"https://doi.org/10.1109/OCEANS.2014.7003157","url":null,"abstract":"Acoustic mapping of ocean currents with Distributed Networked Underwater Sensors (DNUS) system is an effective and energy-saving technique for monitoring oceanographic environments. Unlike the common acoustic tomography methods, this new approach can locally reconstruct ocean currents using data between neighboring sensors. Considering that ocean currents are highly correlated during a short time interval, this paper develops a Kalman filter based tracking approach to improve the DNUS-based ocean current estimation. A 2-D ocean model is used to generate synthetic observational data. The simulation results show that, with the information of the previous ocean current estimates introduced, the proposed method can outperform the traditional current mapping method with DNUS-type system.","PeriodicalId":368693,"journal":{"name":"2014 Oceans - St. John's","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129150631","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 : 2014-09-01DOI: 10.1109/OCEANS.2014.7003159
Al-Abbass Y. Al-Habashneh, C. Moloney, E. Gill
Scan conversion, as a re-sampling process, is expected to add non-wave components to the wave spectrum. Resampling processes involve applying a low-pass filter to retrieve the original image followed by sampling on the new Cartesian grid. Scan conversion is necessary for ocean wave spectrum estimation using the Cartesian Fourier Transform (CFT). The Polar Fourier Transform (PFT) was originally proposed to avoid this intermediate stage and apply the transformation directly on the radar native form. In this paper, which incorporates field data, the PFT performance in estimating the wave spectrum is tested and compared to results from the CFT. Results show that the PFT outperforms the CFT at lower threshold values. This may imply that part of the noise added to the spectrum is due to the scan conversion process.
{"title":"Performance of the Polar Fourier transform for ocean wave spectrum estimation from marine radar","authors":"Al-Abbass Y. Al-Habashneh, C. Moloney, E. Gill","doi":"10.1109/OCEANS.2014.7003159","DOIUrl":"https://doi.org/10.1109/OCEANS.2014.7003159","url":null,"abstract":"Scan conversion, as a re-sampling process, is expected to add non-wave components to the wave spectrum. Resampling processes involve applying a low-pass filter to retrieve the original image followed by sampling on the new Cartesian grid. Scan conversion is necessary for ocean wave spectrum estimation using the Cartesian Fourier Transform (CFT). The Polar Fourier Transform (PFT) was originally proposed to avoid this intermediate stage and apply the transformation directly on the radar native form. In this paper, which incorporates field data, the PFT performance in estimating the wave spectrum is tested and compared to results from the CFT. Results show that the PFT outperforms the CFT at lower threshold values. This may imply that part of the noise added to the spectrum is due to the scan conversion process.","PeriodicalId":368693,"journal":{"name":"2014 Oceans - St. John's","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128532466","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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