Measuring the Water Level Datum Relative to the Ellipsoid During Hydrographic Survey

Hydrographic surveys are referenced vertically to a local water level “chart” datum. Conducting a survey relative to the ellipsoid dictates a datum transformation take place before the survey is used for current navigational products. Models that combine estimates for the tide, sea surface topography, the geoid, and the ellipsoid are often used to transform an ellipsoid referenced survey to a local water level datum. Regions covered by these vertical datum transformation models are limited and so would appear to constrain the areas where ellipsoid referenced surveys can be conducted. Because areas not covered by a vertical datum transformation model still must have a tide model to conduct a hydrographic survey, survey‐ time measurements of the ellipsoid to water level datum can be conducted through the vessel reference point. This measured separation is largely a function of the vessel ellipsoid height and the standard survey tide model and thus introduces limited additional uncertainty than is typical in a water level referenced survey. This approach is useful for reducing ellipsoid reference surveys to the water level datum, examining a tide model, or for evaluating a vertical datum transformation model. Prototype tools and a comparison to typical vertical datum transformation models are discussed

Design and Implementation of an Extensible Variable Resolution Bathymetric Estimator

For grid-based bathymetric estimation techniques, determining the right resolution at which to work is essential. Appropriate grid resolution can be related, roughly, to data density and thence to sonar characteristics, survey methodology, and depth. It is therefore variable in almost all survey scenarios, and methods of addressing this problem can have enormous impact on the correctness and efficiency of computational schemes of this kind. This paper describes the design and implementation of a bathymetric depth estimation algorithm that attempts to address this problem by combining the computational efficiency of locally regular grids with piecewise-variable estimation resolution to provide a single logical data structure and associated algorithms that can adjust to local data conditions, change resolution where required to best support the data, and operate over essentially arbitrarily large areas as a single unit. The algorithm, which is in part a development of CUBE, is modular and extensible, and is structured as a client-server application to support different implementation modalities. The algorithm is called “CUBE with Hierarchical Resolution Techniques”, or CHRT

Investigation of a submerged four-bay mooring system for aquaculture

The August 2003 deployment of a second generation mooring system for fish cages at the University of New Hampshire (UNH) open ocean aquaculture site, south of the Isles of Shoals, NH, is described and evaluated. The new system, a submerged four bay grid similar to those used in inshore aquaculture, uses submerged flotation to maintain its depth and tension. The system\u27s depth and line tensions are sensitive to the deployed anchor locations. Anchors that are not positioned correctly can have reduced holding power or result in problem snap loads. The mooring system deployment process and its resulting geometry was examined through numerical modeling and field measurements using custom instrumentation, revealing the deployed tension and how it is distributed throughout the grid system. Though discrepancies between measured and designed tensions exist, the differences do not compromise the functionality or safety of the system. Suggestions for improved deployment methods result from these findings

Estimating oil concentration and flow rate with calibrated vessel-mounted acoustic echo sounders

As part of a larger program aimed at evaluating acoustic techniques for mapping the distribution of subsurface oil and gas associated with the Deepwater Horizon-Macondo oil spill, observations were made on June 24 and 25, 2010 using vessel-mounted calibrated single-beam echo sounders on the National Oceanic and Atmospheric Administration ship Thomas Jefferson. Coincident with visual observations of oil at the sea surface, the 200-kHz echo sounder showed anomalously high-volume scattering strength in the upper 200 m on the western side of the wellhead, more than 100 times higher than the surrounding waters at 1,800-m distance from the wellhead, and weakening with increasing distance out to 5,000 m. Similar high-volume scattering anomalies were not observed at 12 or 38 kHz, although observations of anomalously low-volume scattering strength were made in the deep scattering layer at these frequencies at approximately the same locations. Together with observations of ocean currents, the acoustic observations are consistent with a rising plume of small (\u3c 1-mm radius) oil droplets. Using simplistic but reasonable assumptions about the properties of the oil droplets, an estimate of the flow rate was made that is remarkably consistent with those made at the wellhead by other means. The uncertainty in this acoustically derived estimate is high due to lack of knowledge of the size distribution and rise speed of the oil droplets. If properly constrained, these types of acoustic measurements can be used to rapidly estimate the flow rate of oil reaching the surface over large temporal and spatial scales

A 15-week vitamin D supplementation and indoor cycling intervention reduces exercising heart rate, with no effect on glycaemic control in healthy adults: A pilot investigation

Significant positive correlations are often observed between vitamin D concentrations and physical activity levels. Whilst this may be due to individuals who are physically active spending time outdoors (i.e. increased opportunity for vitamin D synthesis), there is growing evidence to suggest a more complex relationship between vitamin D status, physical fitness and health outcomes. To explore this further thirty-nine healthy adults were randomly allocated to 15 weeks of exercise training (Ex), no training (NoEx), 2000 IU/day vitamin D (VitD) and/or placebo (Pla) supplementation (giving four possible allocations: NoEx+VitD; NoEx+Pla; Ex+VitD; Ex+Pla). Vitamin D status, glycaemic control and exercise responses were measured pre- and post-intervention. A series of 2 x 2 ANOVAs failed to find any effect of supplementation or exercise on any of the measures except heart rate during low intensity exercise, and vitamin D status. Heart rate was significantly reduced (6%, p < 0.05) in the Ex+VitD group. Vitamin D status was significantly raised (28%, p < 0,05) in the supplementation groups (NoEx+VitD and Ex+VitD) at a time of year (August-November) when a seasonal decline was observed in the placebo groups (33%, p < 0.05). These findings indicate that vitamin D supplementation (2000 IU/day) may have an enhancing role alongside exercise in inducing cardiorespiratory adaptations to exercise training. Further investigations are required to confirm these findings and identify the mechanisms involved

Methods for Collecting and Using Backscatter Field Calibration Information for the Reson 7000 Series Multibeams

In support of Integrated Ocean and Coastal Mapping, the National Oceanic and Atmospheric Administration’s (NOAA) Office of Coast Survey collects meaningful acoustic backscatter as a ancillary product of its navigational charting mission. Many of NOAA’s field units have Reson 7000 series multibeam echosounders which have been shown to have decidedly non-linear response characteristics under certain high signal conditions. This non-linear behavior significantly increases the complexity of the radiometric corrections required to make use of backscatter under a variety of processing paradigms. Avoiding operating these systems in the non-linear operational domain is a simpler approach. However, the onset of non-linear behavior is not a simple function of the output signal level but instead depends on a number of tunable settings. Here we present a method for both determining the onset of non-linear behavior in any installed Reson 7000 series sonar and monitoring the system during real-time acquisition to ensure the system is operating in a linear fashion. In general this information improves the operator’s understanding of the system status and can lead to additional post processing advantages

Digital Holography Experiments with Degraded Temporal Coherence

To simulate the effects of multiple-longitudinal modes and rapid fluctuations in center frequency, we use sinusoidal phase modulation and linewidth broadening, respectively. These effects allow us to degrade the temporal coherence of our master-oscillator laser, which we then use to conduct digital holography experiments. In turn, our results show that the coherence efficiency decreases quadratically with fringe visibility and that our measurements agree with our models to within 1.8% for sinusoidal phase modulation and 6.9% for linewidth broadening

Instrumentation for open ocean aquaculture monitoring

The Woods Hole Oceanographic Institution is assisting the University of New Hampshire by instrumenting a fish cage and mooring as part of their Open Ocean Aquaculture demonstration program in the Gulf of Maine. To understand these systems, the wave and current forcing and the response of the mooring and fish cage needs to be measured. A UNH mooring with an ADCP measured the current forcing. Tension in the mooring lines was measured by load cells deployed with the mooring during servicing in August 2000. Load cells were placed in each anchor line, and, in the NE corner, also in the two grid lines and the riser line to the fish cage. Low power recording systems were deployed on the load cell mounting bars by divers on 22 October 2000, recorded good data through January 2001, when they were turned around and redeployed. Three single load cell recorders were recovered in July 2001 and recorded though 23 June when their data storage filled. The four load cell system was recovered in March after a large winter storm, and had failed in early March. The wave forcing was measured with a wave rider buoy with a 3-axis accelerometer measuring its motion. The acceleration was integrated twice to obtain wave displacement. The system mooring contained a compliant elastic. The wave rider was deployed on 4 January 2001 and recovered on 17 March 2001 after a major Northeast storm. It recorded data throughout its deployment. The motion of the moored fish cage was measured by a motion package constructed around a 6-axis Motion-Pak and a PC-104 data system. The motion package was deployed on the fish cage from Jan into March 2001 and recorded motions thoughout without difficuly. It observed a major storm in early March where the counter weight was lost from the fish cage, and its increase in motion thereafter.Fudning was provided by National Oceanic and Atmospheric Adminstration for the Open Ocean Aquaculture Project under Contract No. NA86RG0016 to the University of New Hampshire and under Subcontracts 00-394 and 01-442 to the Woods Hole Oceanographic Institution