Pub Date : 2008-09-01DOI: 10.1109/OCEANS.2008.5289438
F. Caimi, D. Kocak, F. Dalgleish, J. Watson
Obtaining satisfactory visibility of undersea objects has been historically difficult due to the absorptive and scattering properties of seawater. Mitigating these effects has been a long term research focus, but recent advancements in hardware, software, and algorithmic methods have led to noticeable improvement in system operational range. This paper is intended to provide a summary of recently reported research in the area of Underwater Optics and Vision and briefly covers advances in the following areas: 1) Image formation and image processing methods; 2) Extended range imaging techniques; 3) Imaging using spatial coherency (e.g. holography); and 4) Multipledimensional image acquisition and image processing.
{"title":"Underwater imaging and optics: Recent advances","authors":"F. Caimi, D. Kocak, F. Dalgleish, J. Watson","doi":"10.1109/OCEANS.2008.5289438","DOIUrl":"https://doi.org/10.1109/OCEANS.2008.5289438","url":null,"abstract":"Obtaining satisfactory visibility of undersea objects has been historically difficult due to the absorptive and scattering properties of seawater. Mitigating these effects has been a long term research focus, but recent advancements in hardware, software, and algorithmic methods have led to noticeable improvement in system operational range. This paper is intended to provide a summary of recently reported research in the area of Underwater Optics and Vision and briefly covers advances in the following areas: 1) Image formation and image processing methods; 2) Extended range imaging techniques; 3) Imaging using spatial coherency (e.g. holography); and 4) Multipledimensional image acquisition and image processing.","PeriodicalId":113677,"journal":{"name":"OCEANS 2008","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127133344","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 : 2008-09-01DOI: 10.1109/OCEANS.2008.5151945
J. Han, M. S. Andrews, Jinho Bae, Chong Hyun Lee, H. Jeon
We present a novel switched slide window tracker (SSWT) to track moving targets for Automatic Radar Plotting Aid (ARPA) information in maritime radar. The SSWT is composed of both alpha-beta tracker to find the initial parameters of a slide window and slide window tracker (SWT) to track the moving targets. The proposed algorithm does not require a high computation complexity. In addition, the proposed method can effectively track the nonlinear model by using a piecewise linear model in a target trajectory. The maritime radar simulator with the proposed SSWT algorithm is realized using a commercial DSP board.
{"title":"Maritime radar simulator based on DSP board using switched slide window tracker","authors":"J. Han, M. S. Andrews, Jinho Bae, Chong Hyun Lee, H. Jeon","doi":"10.1109/OCEANS.2008.5151945","DOIUrl":"https://doi.org/10.1109/OCEANS.2008.5151945","url":null,"abstract":"We present a novel switched slide window tracker (SSWT) to track moving targets for Automatic Radar Plotting Aid (ARPA) information in maritime radar. The SSWT is composed of both alpha-beta tracker to find the initial parameters of a slide window and slide window tracker (SWT) to track the moving targets. The proposed algorithm does not require a high computation complexity. In addition, the proposed method can effectively track the nonlinear model by using a piecewise linear model in a target trajectory. The maritime radar simulator with the proposed SSWT algorithm is realized using a commercial DSP board.","PeriodicalId":113677,"journal":{"name":"OCEANS 2008","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129954413","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 : 2008-09-01DOI: 10.1109/OCEANS.2008.5152103
F. Ahmad, S. Rauch, M. Hodor
Oil and gas companies have been focusing their efforts and devoting substantial resources to the Arctic Ocean with the goal of extracting potentially large oil and gas resources. While the Arctic Region may provide significant sources of energy for the United States, industry and Federal regulatory agencies must consider the impact of increased development on the Arctic environment which is currently experiencing deterioration of sea ice due to changing climactic conditions. This paper describes the current legal and regulatory requirements pertaining to oil and gas development in the Arctic Ocean, including the Outer Continental Shelf Lands Act (OCSLA), the Marine Mammal Protection Act (MMPA), the Endangered Species Act (ESA), the National Environmental Policy Act (NEPA), and the Administrative Procedure Act (APA). In addition, the paper highlights key issues that have been arising in this area, including biological effects on marine mammals from seismic surveys and drilling operations and Alaska Native subsistence users and their concern over oil and gas impacts.
{"title":"Oil and gas development in the Arctic Ocean - understanding the legal and regulatory framework","authors":"F. Ahmad, S. Rauch, M. Hodor","doi":"10.1109/OCEANS.2008.5152103","DOIUrl":"https://doi.org/10.1109/OCEANS.2008.5152103","url":null,"abstract":"Oil and gas companies have been focusing their efforts and devoting substantial resources to the Arctic Ocean with the goal of extracting potentially large oil and gas resources. While the Arctic Region may provide significant sources of energy for the United States, industry and Federal regulatory agencies must consider the impact of increased development on the Arctic environment which is currently experiencing deterioration of sea ice due to changing climactic conditions. This paper describes the current legal and regulatory requirements pertaining to oil and gas development in the Arctic Ocean, including the Outer Continental Shelf Lands Act (OCSLA), the Marine Mammal Protection Act (MMPA), the Endangered Species Act (ESA), the National Environmental Policy Act (NEPA), and the Administrative Procedure Act (APA). In addition, the paper highlights key issues that have been arising in this area, including biological effects on marine mammals from seismic surveys and drilling operations and Alaska Native subsistence users and their concern over oil and gas impacts.","PeriodicalId":113677,"journal":{"name":"OCEANS 2008","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129066490","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 : 2008-09-01DOI: 10.1109/OCEANS.2008.5151893
J. Boon, J. Brubaker
Microwave water level sensors offer certain advantages over the acoustic sensor, the present standard for water level measurements obtained in U.S. coastal areas by the National Oceanic and Atmospheric Administration (NOAA). These include high reflectivity of microwave radiation from the target medium (water), low sensitivity to variations in air temperature and humidity, and open-beam transmission eliminating any contact between the device and the water. The latter feature has raised the question of possible interaction between time-of-flight microwave measurements and wind wave motion at the air-water interface. A field comparison between a microwave sensor and the NOAA acoustic water level sensor at Yorktown, Virginia revealed close agreement between sensor measurements in an operational setting and produced no evidence of an dasiaoffsetpsila in the presence of irregular surface gravity waves. However, unlike the acoustic sensor which has a mechanical filter (stilling well) to eliminate wave motion above a fixed dasiacutoffpsila frequency, microwave sensors operate without a stilling well and require numerical filtering to obtain water level measurements in the frequency range of interest; i.e., tidal and sub-tidal frequencies for the classic dasiatide stationpsila. Numerical methods now offer greater choice in deciding where to make the cutoff while reducing measurement error.
{"title":"Acoustic-microwave water level sensor comparisons in an estuarine environment","authors":"J. Boon, J. Brubaker","doi":"10.1109/OCEANS.2008.5151893","DOIUrl":"https://doi.org/10.1109/OCEANS.2008.5151893","url":null,"abstract":"Microwave water level sensors offer certain advantages over the acoustic sensor, the present standard for water level measurements obtained in U.S. coastal areas by the National Oceanic and Atmospheric Administration (NOAA). These include high reflectivity of microwave radiation from the target medium (water), low sensitivity to variations in air temperature and humidity, and open-beam transmission eliminating any contact between the device and the water. The latter feature has raised the question of possible interaction between time-of-flight microwave measurements and wind wave motion at the air-water interface. A field comparison between a microwave sensor and the NOAA acoustic water level sensor at Yorktown, Virginia revealed close agreement between sensor measurements in an operational setting and produced no evidence of an dasiaoffsetpsila in the presence of irregular surface gravity waves. However, unlike the acoustic sensor which has a mechanical filter (stilling well) to eliminate wave motion above a fixed dasiacutoffpsila frequency, microwave sensors operate without a stilling well and require numerical filtering to obtain water level measurements in the frequency range of interest; i.e., tidal and sub-tidal frequencies for the classic dasiatide stationpsila. Numerical methods now offer greater choice in deciding where to make the cutoff while reducing measurement error.","PeriodicalId":113677,"journal":{"name":"OCEANS 2008","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130207161","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 : 2008-09-01DOI: 10.1109/OCEANS.2008.5152081
Jianjun Zhang, Eric W. Gill, J. Walsh
Frequency modulated continuous wave (FMCW) is often employed in practical HF radar ocean surface remote sensing systems. The first- and second-order monostatic cross sections of the ocean surface in the context of high frequency ground wave radar operation are derived for a dipole source with an FMCW waveform. The Fourier coefficients of the rough ocean surface are described as zero-mean Gaussian random variables. The electric field equations for the reception of vertically polarized radiation scattered from ocean surfaces are obtained. Illustrative comparisons of the cross sections between the pulsed and FMCW waveforms are presented and their properties are addressed.
{"title":"High frequency (HF) radar cross sections of the ocean surface incorporating a continuous wave frequency modulated source","authors":"Jianjun Zhang, Eric W. Gill, J. Walsh","doi":"10.1109/OCEANS.2008.5152081","DOIUrl":"https://doi.org/10.1109/OCEANS.2008.5152081","url":null,"abstract":"Frequency modulated continuous wave (FMCW) is often employed in practical HF radar ocean surface remote sensing systems. The first- and second-order monostatic cross sections of the ocean surface in the context of high frequency ground wave radar operation are derived for a dipole source with an FMCW waveform. The Fourier coefficients of the rough ocean surface are described as zero-mean Gaussian random variables. The electric field equations for the reception of vertically polarized radiation scattered from ocean surfaces are obtained. Illustrative comparisons of the cross sections between the pulsed and FMCW waveforms are presented and their properties are addressed.","PeriodicalId":113677,"journal":{"name":"OCEANS 2008","volume":"20 3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130579443","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}
The measurement of ocean bottom geomagnetic vector can provide geomagnetic vector diagram which reveals more detail of orebody distribution for ocean geologists. Former high-precision geomagnetic sensors meet difficulties when measuring geomagnetic vector and applying in ocean bottom. 3 component fluxgate magnetometer should improve its sensitivity and reliability. This paper described a new Ocean Bottom Magnetometer in towed operation to measure geomagnetic vector with high sensitivity and reliability. Anisotropic Magneto Resistive sensor and Strapdown Inertial Navigation System are introduced. Long-distance data transmission system and simplified data visualization algorithm are also designed for practical operation.
{"title":"Towed Ocean Bottom Magnetometer to measure geomagnetic vector based on AMR sensor and SINS","authors":"Xueting Zhang, Jingbiao Liu, Ying Chen, De-nv Huang","doi":"10.1109/OCEANS.2008.5151949","DOIUrl":"https://doi.org/10.1109/OCEANS.2008.5151949","url":null,"abstract":"The measurement of ocean bottom geomagnetic vector can provide geomagnetic vector diagram which reveals more detail of orebody distribution for ocean geologists. Former high-precision geomagnetic sensors meet difficulties when measuring geomagnetic vector and applying in ocean bottom. 3 component fluxgate magnetometer should improve its sensitivity and reliability. This paper described a new Ocean Bottom Magnetometer in towed operation to measure geomagnetic vector with high sensitivity and reliability. Anisotropic Magneto Resistive sensor and Strapdown Inertial Navigation System are introduced. Long-distance data transmission system and simplified data visualization algorithm are also designed for practical operation.","PeriodicalId":113677,"journal":{"name":"OCEANS 2008","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132083503","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 : 2008-09-01DOI: 10.1109/OCEANS.2008.5151870
N. Cater
Ocean Observing systems provide a broad range of users with critical information. This can include information required for problem solving, decision making, prediction and forecasting as well as to support offshore engineering and design. In short, these systems enable us to better understand the oceans around us. Collecting and delivering data in an effective and timely manner is crucial to its viability and consequently its value to the end user. In broadest terms, an ocean observing system is comprised of three primary functional layers. The top layer, from the point of view of the end user, is the application layer, the software tools that enable the user to process, interpret and act upon data. The second layer is the service layer, the hardware and software necessary to move, store and manage data. The third layer is the data collection layer consisting of the sensors and systems that are the physical interface with the ocean environment. The vision of Sensor Web Enablement, sensors that are discoverable, accessible and usable over the World Wide Web, is one that will ultimately have application in all ocean sectors and industries. One area of particular applicability both provincially in Newfoundland and Labrador and regionally in Atlantic Canada is aquaculture. Real time access to site data describing the sometimes rapidly changing oceanographic and meteorological conditions is critical for effective management of a modern aquaculture operation. The School of Ocean Technology at the Fisheries and Marine Institute of Memorial University of Newfoundland is about to embark on a pre-commercial applied research project that will result in a new and innovative approach to ocean observation in support of the aquaculture industry. On a larger scale, the results of the Smart Ocean Sensors Project will create the framework for a new class of observation systems with the capability to be uniquely and independently located, addressed and accessed via the World Wide Web. The School of Ocean Technology will collaborate with the Newfoundland Aquaculture Industry Association to provide the industry with ready access to real time and archival data on marine environmental conditions in support of sustainable aquaculture production. The project is based in the Coast of Bays region, the frontier of the emerging aquaculture industry on the island of Newfoundland and the centre of the rapidly growing commercial salmonid aquaculture industry in the Province. The project will deliver information to the end user through collaboration with the SmartBay initiative. SmartBay is a trial implementation of a user-driven, operations-focused ocean observing system with the vision of integrating and delivering information to a broad base of marine users in a timely and user-friendly manner. Currently based in Placentia Bay, which is geographically adjacent to the Coast of Bays, SmartBay is set to expand its service footprint into the Coast of Bays region under a separate
{"title":"Smart ocean Sensors Web Enabled ocean sensors for aquaculture","authors":"N. Cater","doi":"10.1109/OCEANS.2008.5151870","DOIUrl":"https://doi.org/10.1109/OCEANS.2008.5151870","url":null,"abstract":"Ocean Observing systems provide a broad range of users with critical information. This can include information required for problem solving, decision making, prediction and forecasting as well as to support offshore engineering and design. In short, these systems enable us to better understand the oceans around us. Collecting and delivering data in an effective and timely manner is crucial to its viability and consequently its value to the end user. In broadest terms, an ocean observing system is comprised of three primary functional layers. The top layer, from the point of view of the end user, is the application layer, the software tools that enable the user to process, interpret and act upon data. The second layer is the service layer, the hardware and software necessary to move, store and manage data. The third layer is the data collection layer consisting of the sensors and systems that are the physical interface with the ocean environment. The vision of Sensor Web Enablement, sensors that are discoverable, accessible and usable over the World Wide Web, is one that will ultimately have application in all ocean sectors and industries. One area of particular applicability both provincially in Newfoundland and Labrador and regionally in Atlantic Canada is aquaculture. Real time access to site data describing the sometimes rapidly changing oceanographic and meteorological conditions is critical for effective management of a modern aquaculture operation. The School of Ocean Technology at the Fisheries and Marine Institute of Memorial University of Newfoundland is about to embark on a pre-commercial applied research project that will result in a new and innovative approach to ocean observation in support of the aquaculture industry. On a larger scale, the results of the Smart Ocean Sensors Project will create the framework for a new class of observation systems with the capability to be uniquely and independently located, addressed and accessed via the World Wide Web. The School of Ocean Technology will collaborate with the Newfoundland Aquaculture Industry Association to provide the industry with ready access to real time and archival data on marine environmental conditions in support of sustainable aquaculture production. The project is based in the Coast of Bays region, the frontier of the emerging aquaculture industry on the island of Newfoundland and the centre of the rapidly growing commercial salmonid aquaculture industry in the Province. The project will deliver information to the end user through collaboration with the SmartBay initiative. SmartBay is a trial implementation of a user-driven, operations-focused ocean observing system with the vision of integrating and delivering information to a broad base of marine users in a timely and user-friendly manner. Currently based in Placentia Bay, which is geographically adjacent to the Coast of Bays, SmartBay is set to expand its service footprint into the Coast of Bays region under a separate","PeriodicalId":113677,"journal":{"name":"OCEANS 2008","volume":"31 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130439712","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 : 2008-09-01DOI: 10.1109/OCEANS.2008.5152057
S. Augenstein, S. Rock
This paper describes a method for fusing an inertial position measurement from an Ultra-Short Baseline (USBL) sonar with a water-relative velocity measurement (from DVL, ACM, or other device) to improve knowledge of an underwater vehicle's inertial position. The goal is accuracy sufficient to enable closed-loop position control in the midwater. In this paper we describe the implementation of a kinematic estimator which computes vehicle inertial position and water current velocity. We present the details of this estimator as well as results of field trials which demonstrate the viability of the technique. Field experiments show improvements in accuracy on the order of a factor of 5 above the USBL's raw measurements.
{"title":"Estimating inertial position and current in the midwater","authors":"S. Augenstein, S. Rock","doi":"10.1109/OCEANS.2008.5152057","DOIUrl":"https://doi.org/10.1109/OCEANS.2008.5152057","url":null,"abstract":"This paper describes a method for fusing an inertial position measurement from an Ultra-Short Baseline (USBL) sonar with a water-relative velocity measurement (from DVL, ACM, or other device) to improve knowledge of an underwater vehicle's inertial position. The goal is accuracy sufficient to enable closed-loop position control in the midwater. In this paper we describe the implementation of a kinematic estimator which computes vehicle inertial position and water current velocity. We present the details of this estimator as well as results of field trials which demonstrate the viability of the technique. Field experiments show improvements in accuracy on the order of a factor of 5 above the USBL's raw measurements.","PeriodicalId":113677,"journal":{"name":"OCEANS 2008","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127634279","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 : 2008-09-01DOI: 10.1109/OCEANS.2008.5151811
J. Bird, G. Mullins
Multi-angle swath bathymetry (MASB) sonars are typically used for bathymetry applications but their unique characteristics make them useful for generating clear side-scan images of the bottom, free from artifacts produced by wakes, surface bounce multi-path signals and water column targets. MASB sonars use a small array of long vertically stacked array elements to estimate the angle of arrival for backscatter. Unlike interferometric sonars which can estimate only one angle of arrival, MASB sonars can estimate the arrival angle of multiple same-time targets and therefore the potential exists for separating bottom backscatter from unwanted backscatter. Side-scan sonar is used to obtain high resolution images of the bottom but because of the wide beam it also picks up backscatter from wakes, water column targets, and surface bounce multi-path. This unwanted backscatter obscures the bottom image sometimes making it necessary to resurvey the area if these artifacts are present. Wakes are particularly bothersome in high traffic water ways and busy harbors where it may be necessary to get clear images of the bottom for security or search and recovery applications. This paper shows how MASB processing techniques coupled with beam steering can be used to generate artifact free images of the bottom. The paper begins by briefly outlining MASB sonar principles and then presents the methodology for generating clear bottom images. Element and composite beam patterns are presented for an actual MASB sonar system and these patterns are discussed in the context of target discrimination and artifact removal. Examples are presented of actual side-scan images contaminated by wakes, water column targets, and surface bounce multi-path signals. The data for these images is processed using the techniques described and new side-scan images are presented free of artifacts. A byproduct of the process is that side-scan images of wakes and water column targets can be produced alone without the bottom. This type of image is useful for situations where the water column or wake targets are of primary interest. Finally, conclusions are drawn with regard to the application of these techniques for obtaining unobscured bottom images or images of water column targets or wakes alone for security, and search and survey applications in high traffic areas.
{"title":"Wake removal for clear side-scan images","authors":"J. Bird, G. Mullins","doi":"10.1109/OCEANS.2008.5151811","DOIUrl":"https://doi.org/10.1109/OCEANS.2008.5151811","url":null,"abstract":"Multi-angle swath bathymetry (MASB) sonars are typically used for bathymetry applications but their unique characteristics make them useful for generating clear side-scan images of the bottom, free from artifacts produced by wakes, surface bounce multi-path signals and water column targets. MASB sonars use a small array of long vertically stacked array elements to estimate the angle of arrival for backscatter. Unlike interferometric sonars which can estimate only one angle of arrival, MASB sonars can estimate the arrival angle of multiple same-time targets and therefore the potential exists for separating bottom backscatter from unwanted backscatter. Side-scan sonar is used to obtain high resolution images of the bottom but because of the wide beam it also picks up backscatter from wakes, water column targets, and surface bounce multi-path. This unwanted backscatter obscures the bottom image sometimes making it necessary to resurvey the area if these artifacts are present. Wakes are particularly bothersome in high traffic water ways and busy harbors where it may be necessary to get clear images of the bottom for security or search and recovery applications. This paper shows how MASB processing techniques coupled with beam steering can be used to generate artifact free images of the bottom. The paper begins by briefly outlining MASB sonar principles and then presents the methodology for generating clear bottom images. Element and composite beam patterns are presented for an actual MASB sonar system and these patterns are discussed in the context of target discrimination and artifact removal. Examples are presented of actual side-scan images contaminated by wakes, water column targets, and surface bounce multi-path signals. The data for these images is processed using the techniques described and new side-scan images are presented free of artifacts. A byproduct of the process is that side-scan images of wakes and water column targets can be produced alone without the bottom. This type of image is useful for situations where the water column or wake targets are of primary interest. Finally, conclusions are drawn with regard to the application of these techniques for obtaining unobscured bottom images or images of water column targets or wakes alone for security, and search and survey applications in high traffic areas.","PeriodicalId":113677,"journal":{"name":"OCEANS 2008","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131311477","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 : 2008-09-01DOI: 10.1109/OCEANS.2008.5151824
Hongmei Zhang, Jianhu Zhao, Fengnian Zhou
Now tide- independent bathymetric system is widely used in hydrographic survey and improves effectively single-beam bathymetric accuracy relative to the traditional bathymetric method. While time delay (TD), which exists between GPS RTK and single-beam sounding system, often leads to the positioning and sounding solution non synchronization and decreases the accuracy of final result. TD mainly originates from the lingering output of GPS RTK solution due to its interior algorithm, satellites number, radio signal processing mode and logging data model. Large numbers of experiments have proved that time delay may reach 0.2 second at least and 1.2 second at most. Generally, TD is determined by comparing sounding solutions with positioning solutions measured as vessel going by an anchored buoy in a to-and-fro surveying way with different velocities. However, this method may bring obvious error in the determination due to buoy movement. Therefore the following three methods are studied and presented in the paper. We first study method of characteristic point pairs. Looking for a characteristic inshore seabed, we implemented a to-and-fro measurement along a planning line. The characteristic terrain of the seabed can be found easily in the two profiles. For a characteristic aim on seabed, we can find a pair of characteristic points in the two profiles. According to the two horizontal positions, depths and time of the characteristic point pair, we can calculate the TD. For different characteristic points, we can also determine their time delays. Then the TD of the system is the mean of TDs of all point pairs. Determined TD by the above method needs to choose characteristic point pairs manually. In the following, we will study an automatic determination method, which is method of maximum similarity of profiles. High-sampling rate makes the to-and-fro profiles present seabed topography subtly and continuously. If we think the two profiles are two curves of A and B, we can determine TD in virtue of similarity coefficient R of them. If we fix profile A and move profile B, we can get a series of similarity coefficient R(d). If we move a displacement of d, R reaches maximum or is close to 1, then the d is the displacement resulted from TD. If vA and vB are mean vessel velocity in to-and- fro measurements, then TD can be acquired through the calculating of d divided by the sum of vA and vB. The method can automatically calculate TD, while we must implement a fro-and- to measurement. In the following, we present a more convenient method which is Method of Consistent Vertical Motion of Vessel. Both of heave derived from MRU and GPS height from GPS RTK take the same role in monitoring the vessel vertical motion. If we correct the two signals to the same position, such as reference point(RP) in vessel frame system(VFS), we can get two time series dhheave-RP and hGPS-RP. Taking similar method shown in method of maximum similarity of profiles, we can acquire TD by fix
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