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Articles 451 - 480 of 586

Full-Text Articles in Oceanography and Atmospheric Sciences and Meteorology

Volumes And Areas Of Early Weichselian Ice Dammed Lakes In Northern Russia, Martin Jakobsson, Jan Mangerud, Valery Astakov, John Inge Svendsen Dec 2001

Volumes And Areas Of Early Weichselian Ice Dammed Lakes In Northern Russia, Martin Jakobsson, Jan Mangerud, Valery Astakov, John Inge Svendsen

Center for Coastal and Ocean Mapping

No abstract provided.

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Field Evaluation Of Sounding Accuracy In Deep Water Multibeam Swath Bathymetry, Christian De Moustier Nov 2001

Field Evaluation Of Sounding Accuracy In Deep Water Multibeam Swath Bathymetry, Christian De Moustier

Center for Coastal and Ocean Mapping

A new Kongsberg-Simrad EM120 multibeam echo-sounder has been installed aboard Scripps Institution of Oceanography's Research Vessel Roger Revelle in January 2001. This system can map reliably a 20 km swath of seafloor in 4000 m water depth with 191 soundings per ping. Such a wide swath width demands highly accurate (<0.05' RMS) roll information from a motion sensor, and makes estimating sounding accuracy across the swath an interesting challenge. It is shown that good accuracy estimates can be obtained by collecting data on station under control of the GPS-aided dynamic positioning system usually available on most modern long-range oceanographic vessels. A number of motion sensors, with RMS roll accuracy specifications ranging from 0.05' to 0.01' ,were tested with the EM120 sonar on station in 3800 m to 4000 m water depths. Unexpectedly, they yielded roughly the same depth uncertainty as a function of receive beam angle. This result might be explained by synchronization errors between the attitude data and the sonar data leading to beam pointing errors, other types of beam pointing errors, a range of roll accuracy narrower than specified for the motion sensors, or a combination of these factors

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Ecdis Development Laboratory And Navigation Technology Demonstration Center, Lee Alexander, Maxim F. Van Norden, Charles M. Fralick Nov 2001

Ecdis Development Laboratory And Navigation Technology Demonstration Center, Lee Alexander, Maxim F. Van Norden, Charles M. Fralick

Center for Coastal and Ocean Mapping

The U.S. Navy is undergoing a major transition from traditional, paper chart navigation to computer-based electronic charting. The Chief of Naval Operations (CNO) has mandated that all Navy ships will navigate strictly through electronic means by FY07. However, due to some recent groundings, the Navy is now striving to accelerate the full implementation of electronic navigation by FY04. The Naval Oceanographic Office (NAVOCEANO) is making a concerted effort to support this transition with upgrades to state-of-the-art survey ships, instrumentation, and data processing equipment. NAVOCEANO is increasing its capability to rapidly collect and process hydrographic survey data, and to quickly produce …

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Geozui3d: Data Fusion For Interpreting Oceanographic Data, Colin Ware, Matthew D. Plumlee, Roland J. Arsenault, Larry A. Mayer, Shep M. Smith Lt, Donald H. House Nov 2001

Geozui3d: Data Fusion For Interpreting Oceanographic Data, Colin Ware, Matthew D. Plumlee, Roland J. Arsenault, Larry A. Mayer, Shep M. Smith Lt, Donald H. House

Center for Coastal and Ocean Mapping

GeoZui3D stands for Geographic Zooming User Interface. It is a new visualization software system designed for interpreting multiple sources of 3D data. The system supports gridded terrain models, triangular meshes, curtain plots, and a number of other display objects. A novel center of workspace interaction method unifies a number of aspects of the interface. It creates a simple viewpoint control method, it helps link multiple views, and is ideal for stereoscopic viewing. GeoZui3D has a number of features to support real-time input. Through a CORBA interface external entities can influence the position and state of objects in the display. Extra …

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Hypsometry And Volume Of The Arctic Ocean And Its Constituent's Seas, Martin Jakobsson Nov 2001

Hypsometry And Volume Of The Arctic Ocean And Its Constituent's Seas, Martin Jakobsson

Center for Coastal and Ocean Mapping

No abstract provided.

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Sensor-Assisted Video Mosaicing For Seafloor Mapping, Yuri Rzhanov, Randy G. Cutter Jr., Lloyd C. Huff Oct 2001

Sensor-Assisted Video Mosaicing For Seafloor Mapping, Yuri Rzhanov, Randy G. Cutter Jr., Lloyd C. Huff

Center for Coastal and Ocean Mapping

This paper discusses a proposed processing technique for combining video imagery with auxiliary sensor information. The latter greatly simplifies image processing by reducing complexity of the transformation model. The mosaics produced by this technique are adequate for many applications, in particular habitat mapping. The algorithm is demonstrated through simulations and hardware configuration is described.

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Derivation Of Del180 From Sediment Core Log Data' Implications For Millennial-Scale Climate Change In The Labrador Sea, M. E. Weber, Larry A. Mayer, C. Hillaire-Marcel, G. Bilodeau, F. Rack, R. N. Hiscott, A. E. Aksu Oct 2001

Derivation Of Del180 From Sediment Core Log Data' Implications For Millennial-Scale Climate Change In The Labrador Sea, M. E. Weber, Larry A. Mayer, C. Hillaire-Marcel, G. Bilodeau, F. Rack, R. N. Hiscott, A. E. Aksu

Center for Coastal and Ocean Mapping

Sediment core logs from six sediment cores in the Labrador Sea show millennial-scale climate variability during the last glacial by recording all Heinrich events and several major Dansgaard-Oeschger cycles. The same millennial-scale climate change is documented for surface water δ18O records of Neogloboquadrina pachyderma (left coiled); hence the surface water δ18O record can be derived from sediment core logging by means of multiple linear regression, providing a paleoclimate proxy record at very high temporal resolution (70 years). For the Labrador Sea, sediment core logs contain important information about deepwater current velocities and also reflect the variable …

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Relationships Between Synoptic-Scale Transport And Interannual Variability Of Inorganic Cations In Surface Snow At Summit, Greenland: 1992-1996, J F. Slater, Jack E. Dibb, Barry D. Keim, D W. Kahl Sep 2001

Relationships Between Synoptic-Scale Transport And Interannual Variability Of Inorganic Cations In Surface Snow At Summit, Greenland: 1992-1996, J F. Slater, Jack E. Dibb, Barry D. Keim, D W. Kahl

Earth Sciences

To fully utilize the long-term chemical records retrieved from central Greenland ice cores, specific relationships between atmospheric circulation and the variability of chemical species in the records need to be better understood. This research examines associations between the variability of surface snow inorganic cation chemistry at Summit, Greenland (collected during 1992–1996 summer field seasons) and changes in air mass transport pathways and source regions, as well as variations in aerosol source strength. Transport patterns and source regions are determined through 10-day isentropic backward air mass trajectories during a 1 month (late May to late June) common season over the 5 …

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Improvement Of Image Alignment Using Camera Attitude Information, Yuri Rzhanov, Lloyd C. Huff, Randy G. Cutter Jr. Aug 2001

Improvement Of Image Alignment Using Camera Attitude Information, Yuri Rzhanov, Lloyd C. Huff, Randy G. Cutter Jr.

Center for Coastal and Ocean Mapping

We discuss a proposed technique for incorporation of information from a variety of sensors in a video imagery processing pipeline. The auxiliary information allows one to simplify computations, effectively reducing the number of independent parameters in the transformation model. The mosaics produced by this technique are adequate for many applications, in particular habitat mapping. The algorithm, demonstrated through simulations and hardware configuration, is described in detail

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Moving Icons, Detection And Distraction, Lyn Bartram, Colin Ware, Tom Calvert Jul 2001

Moving Icons, Detection And Distraction, Lyn Bartram, Colin Ware, Tom Calvert

Center for Coastal and Ocean Mapping

Simple motion has great potential for visually encoding information but there are as yet few experimentally validated guidelines for its use. Two studies were carried out to look at how efficiently simple motion cues were detected and how distracting they were in different task contexts. The results show that motion outperforms static representations and identify certain types of motions which are more distracting and irritating than others.

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Automatic Detection Of Outliers In Multibeam Echo Sounding Data, Tianhang Hou, Lloyd C. Huff, Larry A. Mayer May 2001

Automatic Detection Of Outliers In Multibeam Echo Sounding Data, Tianhang Hou, Lloyd C. Huff, Larry A. Mayer

Center for Coastal and Ocean Mapping

The data volumes produced by new generation multibeam systems are very large, especially for shallow water systems. Results from recent multibeam surveys indicate that the ratio of the field survey time, to the time used in interactive editing through graphical editing tools, is about 1:1. An important reason for the large amount of processing time is that users subjectively decide which soundings are outliers. There is an apparent need for an automated approach for detecting outliers that would reduce the extensive labor and obtain consistent results from the multibeam data cleaning process, independent of the individual that has processed the …

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Error Estimation Of Bathymetric Grid Models Derived From Historic And Contemporary Data Sets, Martin Jakobsson, Brian R. Calder, Larry A. Mayer, Andy Armstrong May 2001

Error Estimation Of Bathymetric Grid Models Derived From Historic And Contemporary Data Sets, Martin Jakobsson, Brian R. Calder, Larry A. Mayer, Andy Armstrong

Center for Coastal and Ocean Mapping

The past century has seen remarkable advances in technologies associated with positioning and the measurement of depth. Lead lines have given way to single beam echo sounders, which in turn are being replaced by multibeam sonars and other means of remotely and rapidly collecting dense bathymetric datasets. Sextants were replaced by radio navigation, then transit satellite, GPS and now differential GPS. With each new advance comes tremendous improvement in the accuracy and resolution of the data we collect. Given these changes and given the vastness of the ocean areas we must map, the charts we produce are mainly compilations of …

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Robust Automatic Multi-Beam Bathymetric Processing, Brian R. Calder, Larry A. Mayer May 2001

Robust Automatic Multi-Beam Bathymetric Processing, Brian R. Calder, Larry A. Mayer

Center for Coastal and Ocean Mapping

No abstract provided.

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Geographic Information Systems Tools For Collecting And Accessing Arctic Bathymetry: International Bathymetric Chart Of The Arctic Ocean, Martin Jakobsson Jan 2001

Geographic Information Systems Tools For Collecting And Accessing Arctic Bathymetry: International Bathymetric Chart Of The Arctic Ocean, Martin Jakobsson

Center for Coastal and Ocean Mapping

No abstract provided.

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The Maximum Extent Of The Saalian And Weichselian Glaciations In Eurasis, John Inge Svendsen, Valery Astakov, H Alexanderson, I Demidov, Julian A. Dowdeswell, V. Gataulin, M Henriksen, C Hjort, H W. Hubberten, Martin Jakobsson, M Houmark-Nielsen, K H. Kajeer, E Larsen, J P. Lunkka, Jan Mangerud, A D. Matiouchkov, Per Moller, M Siegert, C Siegert, M Saarnisto, O Maslenikova Jan 2001

The Maximum Extent Of The Saalian And Weichselian Glaciations In Eurasis, John Inge Svendsen, Valery Astakov, H Alexanderson, I Demidov, Julian A. Dowdeswell, V. Gataulin, M Henriksen, C Hjort, H W. Hubberten, Martin Jakobsson, M Houmark-Nielsen, K H. Kajeer, E Larsen, J P. Lunkka, Jan Mangerud, A D. Matiouchkov, Per Moller, M Siegert, C Siegert, M Saarnisto, O Maslenikova

Center for Coastal and Ocean Mapping

No abstract provided.

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Surficial Backscatter Of The Eel River Margin: It's Just Gas!, Luciano E. Fonseca, Larry A. Mayer, Neal Driscoll, Dan Orange, Janet Yun Jan 2001

Surficial Backscatter Of The Eel River Margin: It's Just Gas!, Luciano E. Fonseca, Larry A. Mayer, Neal Driscoll, Dan Orange, Janet Yun

Center for Coastal and Ocean Mapping

No abstract provided.

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On The Estimation Of Errors In Gridded Bathymetric Compilations, Martin Jakobsson, Brian R. Calder, Larry A. Mayer, Andy Armstrong Jan 2001

On The Estimation Of Errors In Gridded Bathymetric Compilations, Martin Jakobsson, Brian R. Calder, Larry A. Mayer, Andy Armstrong

Center for Coastal and Ocean Mapping

No abstract provided.

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A Preliminary Assessment Of Tidal Flooding Along The New Hampshire Coast: Past, Present And Future, Larry G. Ward, Jamie R. Adams Jan 2001

A Preliminary Assessment Of Tidal Flooding Along The New Hampshire Coast: Past, Present And Future, Larry G. Ward, Jamie R. Adams

Faculty Publications

This report presents the results of a preliminary study that examines several critical coastal issues for New Hampshire including sea level fluctuations (past, present and future), shoreline migrations, and tidal flooding. Included are: 1) an analysis of sea level changes over the Holocene and resulting shoreline migrations, 2) an assessment of low-lying areas with elevations below selected tidal flooding datums in coastal areas, and 3) an assessment of increases in low-lying areas that are potentially at risk to tidal flooding over the next century due to sea level rise.

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Martha's Vineyard Survey: Data Collected By Bill Schwab And Bill Danforth - Usgs, Larry A. Mayer Jan 2001

Martha's Vineyard Survey: Data Collected By Bill Schwab And Bill Danforth - Usgs, Larry A. Mayer

Center for Coastal and Ocean Mapping

No abstract provided.

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Physiography And Late Quaternary-Holocene Processes Of Northeastern Gulf Of Mexico Outer Continental Shelf Off Mississippi And Alabama, James V. Gardner, Peter Dartnell, Kenneth J. Sulak, Brian R. Calder, Laurent Hellequin Jan 2001

Physiography And Late Quaternary-Holocene Processes Of Northeastern Gulf Of Mexico Outer Continental Shelf Off Mississippi And Alabama, James V. Gardner, Peter Dartnell, Kenneth J. Sulak, Brian R. Calder, Laurent Hellequin

Center for Coastal and Ocean Mapping

High-resolution multibeam mapping of the mid- and outer continental shelf and upper slope off Mississippi and Alabama reveals a complex bathymetry that reflects conditions during the last eustatic rise and the present high stand of sea level. The most prominent bathymetric features are pinnacles and hardgrounds that are scattered throughout the area. These features generally stand <10 m above the surrounding seafloor, cover large areas, and display a variety of morphologies. Almost all the reef pinnacles and hardgrounds have zones of high acoustic backscatter on their summits and on the seafloor immediately adjacent to their southwest walls. In addition, they also have erosional moats on the seafloor to the southwest. Large fields of bedforms are scattered throughout the mapped area. The asymmetries and orientations of the bedforms suggest that they were formed by excursions of the northeast-flowing Loop Current. In contrast, the pervasive ponding of sediment on the northeast sides of bathymetric highs indicates that one of the predominant directions of sediment transport has been to the south and southwest. The shelf break is a zone of numerous landslides of various sizes and complexities. The morphology of several landslide scars indicates that some of the failures occurred recently. One large reef-capped salt dome was mapped in the area, surrounded by a large field of pock-marks. Fields of pockmarks are also scattered on the shelf. The growth and demise of the reefs are related to the fluctuating transgression of eustatic sea level during the last deglaciation. Two episodes of reef drowning are correlated with the increased rates of sea-level rise during documented melt-water pulses; the first occurred from 14.8 to 14.2 ka and the second from 11.8 to 11.2 ka. Rates of sea-level rise exceeded the maximum growth rate of hermatypic corals only during these two intervals since the last glacial maximum and thus drowned the coral communities.

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Modeling High-Frequency Seafloor Backscattering Of Gassy Sediments: The Eel River Margin Case, Luciano E. Fonseca, Larry A. Mayer Dec 2000

Modeling High-Frequency Seafloor Backscattering Of Gassy Sediments: The Eel River Margin Case, Luciano E. Fonseca, Larry A. Mayer

Center for Coastal and Ocean Mapping

Models of acoustic backscatter typically take into account two different processes: interface scattering and volume scattering. What happens to these two contributions when the sediment is charged with gas bubbles? For the interface backscatter contribution we adopted the model developed by Jackson et al. (1986), but added modifications to accommodate gas bubbles, which when present, even in very small quantities, can dominate the acoustic characteristics of the sediment. The model parameters that are affected by gas content are the density ratio, the sound speed ratio and the loss parameter. To a first approximation, the model roughness parameters are not influenced …

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Osl Dating Supports "High" Sedimentation Rates In Central Arctic Ocean, Martin Jakobsson, Andrew Murray, Jan Backman, Reidar Lovlie Dec 2000

Osl Dating Supports "High" Sedimentation Rates In Central Arctic Ocean, Martin Jakobsson, Andrew Murray, Jan Backman, Reidar Lovlie

Center for Coastal and Ocean Mapping

No abstract provided.

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Photochemical Production Of Gas Phase No X From Ice Crystal No3 −, R E. Honrath, S Guo, Matthew C. Peterson, M P. Dziobak, Jack E. Dibb, Matthew Arsenault Oct 2000

Photochemical Production Of Gas Phase No X From Ice Crystal No3 −, R E. Honrath, S Guo, Matthew C. Peterson, M P. Dziobak, Jack E. Dibb, Matthew Arsenault

Earth Sciences

Recent measurements have demonstrated that sunlight irradiation of snow results in the release of significant amounts of gas phase NOx (NO+NO2). We report here the results of a series of experiments designed to test the hypothesis that the observed NOx production is the result of nitrate photolysis. Snow produced from deionized water with and without the addition of nitrate was exposed to natural sunlight in an outdoor flow chamber. While NOx release from snow produced without added NO−3 was minimal, the addition of 100 µM NO−3resulted in the release …

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Interactive 3-D Visualization: A Tool For Seafloor Navigation, Exploration, And Engineering, Larry A. Mayer, Mark Paton, Lindsay Gee, James V. Gardner, Colin Ware Sep 2000

Interactive 3-D Visualization: A Tool For Seafloor Navigation, Exploration, And Engineering, Larry A. Mayer, Mark Paton, Lindsay Gee, James V. Gardner, Colin Ware

Center for Coastal and Ocean Mapping

Recent years have seen remarkable advances in sonar technology, positioning capabilities, and computer processing power that have revolutionized the way we image the seafloor. The massive amounts of data produced by these systems present many challenges but also offer tremendous opportunities in terms of visualization and analysis. We have developed a suite of interactive 3-D visualization and exploration tools specifically designed to facilitate the interpretation and analysis of very large (10's to 100's of megabytes), complex, multi-component spatial data sets. If properly georeferenced and treated, these complex data sets can be presented in a natural and intuitive manner that allows …

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Release Of No(X) From Sunlight-Irradiated Midlatitude Snow, R E. Honrath, Matthew C. Peterson, M P. Dziobak, Jack E. Dibb, Matthew Arsenault, S A. Green Aug 2000

Release Of No(X) From Sunlight-Irradiated Midlatitude Snow, R E. Honrath, Matthew C. Peterson, M P. Dziobak, Jack E. Dibb, Matthew Arsenault, S A. Green

Earth Sciences

Photochemical production and release of gas-phase NO(x) (NO + NO2) from the natural snowpack at a remote site in northern Michigan were investigated during the Snow Nitrogen and Oxidants in Winter study in January 1999. Snow was collected in an open 34 L chamber, which was then sealed with a transparent Teflon cover and used as an outdoor flow and reaction chamber. Significant increases in NO(x) mixing ratio were observed in synthetic and ambient air pulled through the sunlit chamber. [NO(x)] enhancements were correlated to ultraviolet sunlight intensity, reaching ~300 pptv under partially overcast midday, mid-winter conditions. These findings are …

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Diagrams Based On Structured Object Perception, Pourang Irani, Colin Ware May 2000

Diagrams Based On Structured Object Perception, Pourang Irani, Colin Ware

Center for Coastal and Ocean Mapping

Most diagrams, particularly those used in software engineering, are line drawings consisting of nodes drawn as rectangles or circles, and edges drawn as lines linking them. In the present paper we review some of the literature on human perception to develop guidelines for effective diagram drawing. Particular attention is paid to structural object recognition theory. According to this theory as objects are perceived they are decomposed into 3D set of primitives called geons, together with the skeleton structure connecting them. We present a set of guidelines for drawing variations on node-link diagrams using geon-like primitives, and provide some examples. Results …

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Tropospheric Reactive Odd Nitrogen Over The South Pacific In Austral Springtime, Jack E. Dibb, R. Talbot, Eric Scheuer, J D. Bradshaw, S T. Sandholm, D R. Blake, N J. Blake, Elliot Atlas, F Flocke Mar 2000

Tropospheric Reactive Odd Nitrogen Over The South Pacific In Austral Springtime, Jack E. Dibb, R. Talbot, Eric Scheuer, J D. Bradshaw, S T. Sandholm, D R. Blake, N J. Blake, Elliot Atlas, F Flocke

Earth Sciences

The distribution of reactive nitrogen species over the South Pacific during austral springtime appears to be dominated by biomass burning emissions and possibly lightning and stratospheric inputs. The absence of robust correlations of reactive nitrogen species with source-specific tracers (e.g., C2H2 [combustion], CH3Cl [biomass burning], C2Cl4 [industrial],210Pb [continental], and 7Be [stratospheric]) suggests significant aging and processing of the sampled air parcels due to losses by surface deposition, OH attack, and dilution processes. Classification of the air parcels based on CO enhancements indicates that the greatest influence was found in …

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Chemical Nox Budget In The Upper Troposphere Over The Tropical South Pacific, Martin G. Schultz, Daniel J. Jacob, J D. Bradshaw, S T. Sandholm, Jack E. Dibb, R. Talbot, Hanwant B. Singh Mar 2000

Chemical Nox Budget In The Upper Troposphere Over The Tropical South Pacific, Martin G. Schultz, Daniel J. Jacob, J D. Bradshaw, S T. Sandholm, Jack E. Dibb, R. Talbot, Hanwant B. Singh

Earth Sciences

The chemical NOx budget in the upper troposphere over the tropical South Pacific is analyzed using aircraft measurements made at 6-12 km altitude in September 1996 during the Global Tropospheric Experiment (GTE) Pacific Exploratory Mission (PEM) Tropics A campaign. Chemical loss and production rates of NOx along the aircraft flight tracks are calculated with a photochemical model constrained by observations. Calculations using a standard chemical mechanism show a large missing source for NOx; chemical loss exceeds chemical production by a factor of 2.4 on average. Similar or greater NOx budget imbalances have been reported in analyses of data from previous …

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Composition And Distribution Of Aerosols Over The North Atlantic During The Subsonic Assessment Ozone And Nitrogen Oxide Experiment (Sonex), Jack E. Dibb, R. Talbot, Eric Scheuer Feb 2000

Composition And Distribution Of Aerosols Over The North Atlantic During The Subsonic Assessment Ozone And Nitrogen Oxide Experiment (Sonex), Jack E. Dibb, R. Talbot, Eric Scheuer

Earth Sciences

We report the mixing ratios of aerosol-associated soluble ions (focusing on SO4= and NO3−) and HNO3 over the North Atlantic during NASA's Subsonic Assessment Ozone and Nitrogen Oxide Experiment (SONEX). The SONEX campaign was designed to quantify the impacts of jet emissions in the North Atlantic Flight Corridor (NAFC) by sampling both directly within and far removed from the organized track system. Beryllium-7 activities were also measured to assess the magnitude of stratospheric influence in the SONEX study region. Mixing ratios of aerosol-associated SO4= and NO3− above 8 km during …

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Reactive Nitrogen Budget During The Nasa Sonex Mission, R. Talbot, Jack E. Dibb, Eric Scheuer, Y Kondo, M Koike, H B. Singh, L Salas, F Fukui, J O. Ballenthin, R F. Meads, T M. Miller, D E. Hunton, A A. Viggiano, D R. Blake, N J. Blake, Elliot Atlas, F Flocke, D J. Jacob, L Jaegle Oct 1999

Reactive Nitrogen Budget During The Nasa Sonex Mission, R. Talbot, Jack E. Dibb, Eric Scheuer, Y Kondo, M Koike, H B. Singh, L Salas, F Fukui, J O. Ballenthin, R F. Meads, T M. Miller, D E. Hunton, A A. Viggiano, D R. Blake, N J. Blake, Elliot Atlas, F Flocke, D J. Jacob, L Jaegle

Earth Sciences

The SASS Ozone and Nitrogen Oxides Experiment (SONEX) over the North Atlantic during October/November 1997 offered an excellent opportunity to examine the budget of reactive nitrogen in the upper troposphere (8–12 km altitude). The median measured total reactive nitrogen (NOy) mixing ratio was 425 parts per trillion by volume (pptv). A data set merged to the HNO3 measurement time resolution was used to calculate NOy (NOy sum) by summing the reactive nitrogen species (a combination of measured plus modeled results) and comparing it to measured NOy (NOy meas.). Comparisons were done for tropospheric …

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