Showing papers in "Marine Geodesy in 2008"
TL;DR: In this paper, a non-linear regression model is used to invert multi-spectral images into bathymetric data, which is based on the Levenberg-Marquardt optimization algorithm.
Abstract: Most previous studies utilized a log-linear regression model to invert multi-spectral images into bathymetric data. Based on the Levenberg-Marquardt optimization algorithm, we developed an automated method for calibrating the parameters for a non-linear inversion model. Our method has been successfully applied to an IKONOS multispectral image. We compared depth data derived from our model to those estimated using a conventional log-linear inversion model. Bathymetric data derived from the non-linear inversion model are slightly more accurate and stable, particularly for deeper benthic habitats, than those derived from a conventional log-linear model although their overall performances are very similar.
131 citations
TL;DR: The sixth special issue on Marine and Coastal Geographic Information Systems (M&CGIS) is the first to be based on an organized series of presentations at a conference, the 2008 Association of Amer... as discussed by the authors.
Abstract: This sixth special issue on Marine and Coastal Geographic Information Systems (M&CGIS) is the first to be based on an organized series of presentations at a conference, the 2008 Association of Amer...
77 citations
TL;DR: In this paper, an ArcGIS classification toolset was developed using supervised image classification tools to characterize potential shallow marine benthic habitats using bathymetry data sets collected north of San Francisco Bay (CA).
Abstract: Using data sets collected north of San Francisco Bay (CA) an ArcGIS classification toolset was developed using supervised image classification tools to characterize potential shallow marine benthic habitats. First-derivative images and a topographic algorithm, called Bathymetric Position Index were created from the bathymetry data set using ArcGIS Spatial Analyst tools. Backscatter intensity was also analyzed by creating training samples based on the collected sediment samples and then applying multivariate statistical tools to delinate textural classes. The data collected revealed a rugged and complex seafloor and imaged in detail basement and bedrock outcrops, sand and gravel bedforms, and flat sediment covered seabed.
62 citations
TL;DR: In this paper, a model of Tutuila Island, American Samoa, is created using depths derived from IKONOS satellite imagery to provide data in the near-shore gap between sea level and the beginning of sonar data at 10-15 m depth.
Abstract: Satellite and acoustic remote sensing enable the collection of high-resolution seafloor bathymetry data for integration with terrestrial elevations into coastal terrain models. A model of Tutuila Island, American Samoa, is created using depths derived from IKONOS satellite imagery to provide data in the near-shore gap between sea level and the beginning of sonar data at 10–15 m depth. A derivation method gauging the relative attenuation of blue and green spectral radiation is proven the most effective of several proposed in recent literature. The resulting coastal terrain model is shown to be accurate through statistical analyses and topographic profiles.
59 citations
TL;DR: In this paper, the utility of several LIDAR-derived seascape metrics (e.g., depth, rugosity, slope, variance in depth) was assessed to determine which measures of the seascapes demonstrated important relationships with fish assemblage structure and would ultimately serve as the best ecological criteria to advance predictive modeling of fishes using remote sensing and GIS analysis.
Abstract: We assessed the utility of several LIDAR-derived seascape metrics (e.g. depth, rugosity, slope, variance in depth) to determine which measures of the seascape demonstrated important relationships with fish assemblage structure and would ultimately serve as the best ecological criteria to advance predictive modeling of fish assemblages using remote sensing and GIS analysis. Variance in depth (within a 75 m radius) was the seascape metric that had the strongest relationships with most fish assemblage metrics, followed by depth and slope. Our results demonstrate the potential for using remotely sensed measures of the seascape to support predictive mapping and modeling of fish assemblages.
54 citations
TL;DR: In this paper, the authors used the depth-attenuated wave exposure instead of the continuous simplified wave model (SWM) model as a predictor in substrate modeling in the Stockholm archipelago.
Abstract: Several studies have documented relationships between wave exposure and distribution, density, and size of marine species. Hence, this factor is at a high level in the hierarchical habitat classification system EUNIS and is one of the Water Framework Directive water typology criteria of coastal waters. Isaeus (2004) has developed a continuous simplified wave model (SWM) that has been applied to several Nordic countries. Here we refine this model by introducing depth-attenuation, giving us the advantage of a model for wave exposure as it will actually work at the seabed. The values of the depth-attenuated model SWM(d) are approximately similar to the SWM model in shallow areas but noticeably lower in deep areas. The two models were compared in an analysis of the distribution of seabed substrate in the Stockholm archipelago. Using the depth-attenuated wave exposure instead of the SWM model as predictor in substrate modeling improved these models considerably.
49 citations
TL;DR: In this paper, four maps of a reef ecosystem were created using two levels of both spatial and thematic resolution commonly used in science and management applications, and differences among maps were quantified using ecologically meaningful landscape indices.
Abstract: Four maps of a reef ecosystem were created using two levels of both spatial and thematic resolution commonly used in science and management applications. Differences among maps were quantified using ecologically meaningful landscape indices. The objective was to inform research and management activities that are based on maps of reef ecosystems. Results indicate that inferences regarding the structure and organization of reef ecosystems are sensitive to changes in resolution of the maps characterizing them. Hard bottom, sand, and patchy features were the most sensitive to change in map resolution whereas continuous seagrass beds and linear reef features were not.
42 citations
TL;DR: In this article, the authors explored the use of habitat-based assessment for increasing our understanding of fish distribution patterns and potentially generating stock assessment data over large areas, and they attempted to test these hypotheses using predictive models.
Abstract: Due to the decline of fisheries throughout the world, there is an ever-increasing demand among fisheries managers for more and better data regarding the distribution and abundance of commercially important fishes. Along the Pacific coast of North America, there are insufficient stock data for most rockfish species, which compose one of the most valuable commercial and recreational fisheries in California. One approach being explored for increasing our understanding of fish distribution patterns and potentially generating stock assessment data over large areas is the use of habitat-based assessment. The general hypothesis is that because rockfish are not randomly distributed across habitats, it should be possible to model and predict their distribution and abundance based on habitat maps and biological data. Furthermore, to the extent that these models are robust and portable, they should be applicable across a variety of locations and physical settings. We attempt to test these hypotheses using predictive...
35 citations
TL;DR: In this paper, the authors evaluated the geospatial aspects of known Nassau grouper spawning aggregation sites in the Cayman Islands and found that the five known Nassua grouper aggregation sites are located at convex-shaped reefs within 1 km of reef promontory tips.
Abstract: Reef fish spawning aggregation sites are essential life habitats vulnerable to exploitation by fishermen, yet no quantitative comparisons of sites exist to understand their geomorphologic patterns. The objective of this study was to evaluate the geospatial aspects of known Nassau grouper spawning aggregation sites in the Cayman Islands. The results illustrate that the five known Nassau grouper spawning aggregation sites are located at convex-shaped reefs within 1 km of reef promontory tips. Further, all sites are found in 25–45 m depth, less than 50 m from shelf edges. Finally, they have been documented as multi-species spawning aggregation sites.
31 citations
TL;DR: In this article, the seasonal circulation and mixed layer depths in Bay of Bengal is modeled using the three-dimensional Princeton Ocean Model (POM) along the coastal boundaries a higher resolution is accomplished using the curvilinear orthogonal grid.
Abstract: The seasonal circulation and mixed layer depths in Bay of Bengal is modeled using the three-dimensional Princeton Ocean Model (POM). Along the coastal boundaries a higher resolution is accomplished using the curvilinear orthogonal grid. Model uses a free-surface and terrain following sigma coordinates. The initial climatological salinity and temperature fields for the model are derived from the World Ocean Atlas-2001(WOA01). The Model is forced with wind stress derived from COADS wind climatology. Bilinear interpolation is used to obtain the initial fields and wind stress to the required model specification. Using the seasonal fields and wind stress the model is integrated for simulating Bay of Bengal circulation. The numerical simulations on climatological scale for monsoon months were conducted to study the evolution of dynamics. The simulations bring out not only the typical characteristic features of fresh water plume along the coast but also intensification of the flow over the monsoon period. The in...
27 citations
TL;DR: In this article, the authors investigated the accuracy of IKONOS and QuickBird satellite stereo image pairs with aerial images acquired over a region at Tampa Bay, Florida and showed that the accuracy is related to a few factors of imaging geometry.
Abstract: This paper investigates the geopositioning accuracy achievable from integrating IKONOS and QuickBird satellite stereo image pairs with aerial images acquired over a region at Tampa Bay, Florida. The results showed that the accuracy is related to a few factors of imaging geometry. For example, the geopositioning accuracy of a stereo pair of IKONOS or QuickBird images can be improved by integrating a set of aerial images, even just a single aerial image or a stereo pair of aerial images. Shorelines derived from the IKONOS and QuickBird stereo images, particularly the vertical positions, are compared with the corresponding observations of water-penetrating LiDAR and water gauge stations and proved that differences are within the limit of the geopositioning uncertainty of the satellite images.
TL;DR: In this paper, the authors used Hydroacoustic fisheries surveys to estimate fish biomass in the context of underlying features and bottom types by applying spatial techniques and regression analysis, and found that distance to rock ledges was the best predictor of fish biomass.
Abstract: A recent focus of the National Oceanic and Atmospheric Administration (NOAA) National Marine Sanctuaries Program is the characterization and assessment of marine resources associated with coral reef and live bottom habitats in protected areas. Detailed bottom maps have been produced making it possible to quantify bottom features within Gray's Reef National Marine Sanctuary, Georgia, USA. Hydroacoustic fisheries surveys were used to estimate fish biomass in the context of underlying features and bottom types by applying spatial techniques and regression analysis. Variables relating bottom features to estimated fish biomass differed based upon depth in the water column. Distance to rock ledges was the best predictor of fish biomass in the bottom 2 m of the water column, whereas the area of two bottom habitat types combined was a reliable predictor of estimated fish biomass in the mid water column.
TL;DR: In this article, the use of high resolution (0.1m) side-scan sonar for generating detailed benthic maps (4 m2 mapping unit) in coral reef environments was investigated by collecting imagery over 60 km2 of the Puerto Rico insular shelf, from shoreline to shelfedge.
Abstract: Use of high resolution (0.1m) side-scan sonar for generating detailed benthic maps (4 m2 mapping unit) in coral reef environments was investigated by collecting imagery over 60 km2 of the Puerto Rico insular shelf, from shoreline to shelfedge. Visual interpretation of acoustic imagery resulted in 21 different habitat types classified within broad categories of unconsolidated sediment (7), consolidated bottom (6), and vegetated areas (8). Detailed maps showed the amount, size, and spatial distribution of habitats across the shelf. Qualitative and quantitative benthic characterizations showed habitats to be biologically distinct and ecologically relevant at multiple scales. Image collection was cost effective and amenable to small-boat use.
TL;DR: In this article, the mixed layer depths over the Arabian Sea were computed for the three successive years 2004-2006 using ARGO floats data, and the results were compared with World Ocean Atlas 1994 MLD Climatology.
Abstract: The mixed layer depths over the Arabian Sea were computed for the three successive years 2004–2006 using ARGO floats data. The large availability of ARGO floats for the above period resulted in better estimation of mixed layer depth (MLD) over the Arabian Sea. The results were compared with World Ocean Atlas 1994 MLD Climatology. Marked variability in MLD on a monthly time scale is observed and it was in accordance with the wind stress and/or net heat gain variability, which are the principal factors influencing mixed layer over Arabian Sea. With the availability of large number of ARGO profile data, an attempt is made to study the monthly variability of Mixed Layer.
TL;DR: In this article, a review of the work done in association with the modeling, detection, and application of the barotropic, basin-wide normal modes of the global oceans is presented.
Abstract: This paper deals with the normal modes of the global oceans. More specifically, it reviews some of the work done in association with the modeling, detection, and application of the barotropic, basin-wide normal modes. The paper presents some results obtained by means of the Proudman-Rao method. The fields of tidal synthesis from a set of normal modes, and paleotides, in the context of normal modes and the evolution of the Earth-Moon system, are surveyed as well. Works associated with the detection of normal modes are discussed also. The paper closes with an analysis of possible future developments.
TL;DR: In this article, the authors studied the role of different driving forces for erosion/accretion in a placer mining beach on the southwest Indian coast and concluded that even though sand mining will cause erosion in the innershelf, the time taken for a measurable impact can be long if the mining volumes are much less than the annual volume changes.
Abstract: The erosion/accretion pattern in a placer mining beach on the southwest Indian coast was monitored for five years to study the role of different driving forces. The beach has maximum width during the fair weather months and least in the rough monsoon months. Apart from hydrodynamic processes, sand mining and presence of sea wall are found to be the driving forces for erosion/accretion. Impact of sand mining is not felt on the beach when the mining is within an optimum level, equivalent to the natural replenishment. It is concluded that, though sand mining will cause erosion in the innershelf, the time taken for a measurable impact can be long if the mining volumes are much less than the annual volume changes.
TL;DR: The French Transportable Laser Ranging System (FTLRS) was deployed in the calibration site of satellite radar altimeters in Corsica over the 2002 and 2005 campaigns as mentioned in this paper.
Abstract: The French Transportable Laser Ranging System (FTLRS) was deployed in the calibration site of satellite radar altimeters in Corsica over the 2002 and 2005 campaigns. The paper describes the different steps of SLR data processing. The average arcs RMS obtained are about 1–2 cm for Lageos-1&-2, Starlette and Stella satellites; it is shown that the best results of satellite orbits determination and geocentric positioning are obtained with Eigen-Grace03s gravity model. The difference of FTLRS absolute 3D positioning, between 2002 and 2005, of about 7.7 mm (i.e., 2.6 mm/yr) is less than residual errors of ITRF2005 velocities (of about 4.3 mm/yr).
TL;DR: In this article, the authors studied the minimal time ship routing between Mumbai port (India) to Mombasa port (Kenya) using model hindcast wave climate over the Arabian Sea.
Abstract: Minimal time ship routing is studied between Mumbai port (India) to Mombasa port (Kenya) using model hindcast wave climate over the Arabian Sea. With the launch of IRS-P4 (OCEANSAT-I), it became possible now to carry out routine wave hindcasting over the Indian Ocean. The MSMR channel of the satellite gives scalar wind, which is analyzed at NCMRWF, India, for converting to vector winds. The same is used as input to third-generation spectral wave model WAM for regional grid system for simulating the rough weather period of July 2000. This simulated wave climate formed the basis for computing effective ship velocity in the irregular seaway. This study gives a quantitative estimation of change in ship velocity in the open Indian Ocean for a bulk carrier. The minimal time path is charted using Dijkstra's algorithm for optimum route voyage. The optimum track information has broad scope for obtaining a safer route, least time route by avoiding delay in schedule with minimum fuel consumption.
TL;DR: In this article, a sigma coordinate model is used to study the heat transport variability and the influence of Indonesian Throughflow (ITF) heat transport on the Indian Ocean, and it is found that the overall effect of the ITF heat transport is dominant on the south of $10.
Abstract: A sigma coordinate model is used to study the heat transport variability and the influence of Indonesian Throughflow (ITF) heat transport on the Indian Ocean. The vertical mixing coefficients were provided by the turbulence scheme. The horizontal mixing coefficients for momentum (viscosity) and tracers (diffusivity) were calculated by a Smagorinsky-type formulation. The model is initialized with the Levitus94 climatological data set for annual mean temperature and salinity fields and is forced by seasonal and yearly varying da Silva SMD 1994 and Hellerman and Rosenstein (1983) wind data set. The spin-up of the model has been carried out separately for open and closed. The ITF transport is found around 10 Sv (Svedrup) $(1 Sv = 10_6 m^{3}/s)$, and the heat transport across the equator is found at its maximum amplitude 1.3 PW (Peta Watt) $(1 PW = 10^{15} Watts)$ in March and -1.6 PW in July. It is found that the overall effect of the ITF heat transport on the Indian Ocean is dominant on the south of $10^oS$, and this has a small effect between equator and $10^oS$.
TL;DR: In this article, the feasibility of coupled pattern reconstruction technique (CPR) developed by Nardelli and Santoleri (2004) in detecting the internal waves at three locations in the north Indian Ocean was studied.
Abstract: The main focus of this paper is to study the feasibility of coupled pattern reconstruction technique (CPR) developed by Nardelli and Santoleri (2004) in detecting the internal waves at three locations in the north Indian Ocean. In all the cases, the first two modes, viz. Mode 0 and Mode 1, explained most of the co-variability between these two parameters at all the three locations (91% in the northern Bay of Bengal and 97% in the coastal waters). Moreover, the coefficients that relate the amplitudes of temperature and steric height for the first two modes follow a linear relationship, satisfying the conditions of the CPR. The temporal variations of these two modes are found to be within the bands of tidal periodicity. The CPR technique was able to reconstruct the synoptic scale variation in the temperature at different depths with a reasonable degree of accuracy. This technique was able to capture the variability within the bands of tidal periodicity (6–24 hrs) as evident from the oscillations in the ther...
TL;DR: In this article, a method is described for mapping time-uncorrelated large-scale errors in satellite altimeter sea surface heights, and the functional dependence of these deviations on absolute time difference is used to estimate the errors of individual measurements.
Abstract: A method is described for mapping time-uncorrelated large-scale errors in satellite altimeter sea surface heights. Standard deviations of differences between pairs of successive measurements at track crossovers are computed, and the functional dependence of these deviations on absolute time difference is used to estimate the errors of individual measurements. This is first applied to all of ERS-1,2 altimeter data in the Pacific Ocean, yielding average errors of 3.2 cm in the deep ocean (>1 km) and 4.7 cm in the shallow seas (<1 km). The procedure is repeated for variable latitude bands, each with a full range of possible time differences, yielding a meridional profile of computed errors, ranging from 2.6 cm near the Antarctic continent (67–60S) and South Subtropical regions (25–5S) to 3.5 cm in the Antarctic Circumpolar Current (60–45S) and the Northern Hemisphere Subtropical and Subpolar Gyres. Finally, coarse-resolution maps of these errors are produced by subdividing the Pacific Ocean into latitude-lon...