P.R. Hill

Bio: P.R. Hill is an academic researcher. The author has contributed to research in topics: Tripod (photography) & Data logger. The author has an hindex of 1, co-authored 1 publications receiving 5 citations.

A configurable multi-sensor tripod for the study of near-bottom ocean processes

Abstract: A cost effective and highly configurable scientific platform, dubbed Norton, has been developed for the scientific study of near-bottom ocean processes. The basic platform is a collapsible lightweight aluminum tripod that can be transported in the back of a pick-up truck, and is easily accommodated on most vessels. Ballast is supplied in the form of large ship anodes bolted to the base of each leg. The desired sensors are attached to the tripod legs and bracing. A typical deployment might utilize the following sensors: Acoustic Doppler Current Profiler for current profiles and directional wave data. Marsh McBirney electromagnetic flow sensor for measurements close to the bottom, supporting both wave orbital burst sampling and average current measurements. Optical Backscatter Sensors (OBS) for sediment concentration. Sector-scanning sonar to supply bed-form images; an Imagenex variable frequency scanning head has been integrated into a self-contained housing containing a control module, data logger and power supply. Other sensors can be added as desired. Norton is usually deployed by lowering with a line from the ship. An acoustic release is used to let go of the tripod once it is on bottom. A customized 'tilt-pinger' provides confirmation to the crew that the tripod is upright. Recovery can be via a pop-up buoy and/or a ground-line.

Scanners, targets, and methods for surveying

Abstract: Apparatus and methods useful in surveying to provide information rich models. In particular, information not readily or possibly provided by conventional survey techniques can be provided. In some versions targets provide reference for baseline positioning or improving position information otherwise acquired. Scanning may be carried out in multiple locations and merged to form a single image. Machine mounted and hand mounted scanning apparatus is disclosed.

Sediment Transport on Roberts Bank: A Sandy Intertidal Flat on the Fraser River Delta

Abstract: Waves and currents were monitored over a range of incident forcing between March 23 and April 24, 2003, on Roberts Bank, the sandy intertidal portion of the Fraser River Delta. A comparison of the dimensionless, current-induced skin friction with the critical skin friction for the initiation of sediment motion suggests that the currents are only capable of entraining sediment briefly with the ebbing tide or when enhanced by the wind. Since these wind-generated currents are associated with storm waves, which typically exceed the critical skin friction, they have a disproportionately large impact on the direction of the sediment transport. An energetics-based model, driven by locally measured near-bottom currents, is used to characterize the rate and direction of bedload and suspended load transport. The largest transport rates were predicted in response to storm waves and were initially directed onshore with weak oscillatory transport and alongshore by wind-generated currents that turned offshore ...

The capabilities of Doppler current profilers for directional wave measurements in coastal and nearshore waters

Abstract: The adaptation of Doppler current profilers to measure directional wave spectra has provided a new instrumentation approach to coastal and nearshore oceanographic studies Past studies have shown favorable comparisons between Doppler current profiler wave instruments with bottom mounted PUV (pressure-velocity) sensors sampling at wave frequencies and wave buoys In this paper, we examine the capabilities and limitations of two different Doppler current profilers for directional wave measurements in shallow coastal waters of 0-25 m water depth Data collection programs using Doppler current profilers for wave measurements have been conducted for one month long periods in the early spring of 2002, 2003 and 2004 on Roberts Bank in the Fraser River foreslope region of the Strait of Georgia, British Columbia, Canada In 2004, an RD Instrument ADCP along with the newly-released 1000 kHz Nortek AWAC current profiler and wave instrument were co-located in 7 m water depth at a different site on the edge of Roberts Bank Inter-comparisons between these bottom mounted instruments are used to examine the capabilities of the directional wave spectral parameters, in terms of: resolvable frequencies for directional and nondirectional wave spectra; wave directional resolution and reliability, and limitations arising from the use of linear wave theory For a preliminary assessment of the capability of Doppler wave spectra in deeper waters of 20-25 m depths, in particular for very long wave periods, some experiences derived from a long-term measurement program being conducted off the west coast of Africa are presented

3D Hydrodynamic Modeling of Sediment Dynamics on Roberts Bank, Fraser River Foreslope, Strait of Georgia, Canada

Abstract: A fully three-dimensional, nested grid, integrated circulation-wave-sedimentgeomorphology numerical model, COCIRM-SED, was developed to study sediment dynamics on Roberts Bank, Fraser River foreslope, Strait of Georgia, Canada. Roberts Bank is an extensive intertidal zone, located just south of where the main (South Arm) Fraser River channel enters the Strait of Georgia. The substrate of Roberts Bank is primarily silty sand, and a total of four grain size classes were considered in the model. The study area of interest is modeled using a fine grid size of 100 m by 100 m, and is nested within the much larger domain of the Strait of Georgia with a coarser grid size of 500 m by 500 m. These two model domains are solved together at every time step using a fully dynamic and two-way connection scheme. Following initial testing with idealized analytical cases, the COCIRM-SED modeled flows and suspended sediment concentration were calibrated and verified using the data obtained with a configurable multi-sensor tripod system on the Bank and at the edge of the Bank, respectively. These field data, including month-long ADCP current profiles, OBS sediment concentrations, and directional wave measurements, are used to examine the model performance. The preliminary model results provide improved understandings of the sediment dynamics on Roberts Bank.

Wave dynamics over Roberts Bank, British Columbia: processes and modelling

Abstract: Between 1 March and 26 March 2002, a wave and current measurement station was deployed on the upper delta slope of Roberts Bank in approximately 12 m of water. The field data were analyzed and used in a parabolic wave model to determine wave characteristics for fair-weather, moderate, and storm conditions. The model shows that storm waves act nonuniformly along the beach depending on the local morphology and tidal elevation. Waves propagating during high tide are characterized by smooth dissipation and progressive refraction, whereas waves propagating during low tide show intense refraction and breaking in front of or over a low-tide bar. Sediment transport divergence in the nearshore is strongly controlled by the temporal relationship between storm waves and tidal height. Resume : Entre le 1er et le 26 mars 2002, une station instrumentee a ete deployee sur la partie superieure de la pente deltaique du banc Roberts, dans approximativement 12 m d’eau, afin de mesurer la houle et les courants. Les donnees de terrain ont ete ensuite analysees et utilisees dans un modele parabolique de houle afin de determiner les caracteristiques des houles pendant les conditions de beau temps, moderees et de tempete. Le modele montre que les houles de tempete agissent non uniformement le long de la plage selon la morphologie locale et le marnage. La propagation de la houle a maree haute est caracterisee par une legere dissipation et une refraction progressive tandis que les houles se propageant a maree basse montrent une intense refraction et deferlent sur le front ou au-dessus d’une barre de maree basse. La divergence du transport sedimentaire dans la zone littorale est fortement controlee par la relation temporelle entre les houles de tempete et le niveau de la maree. Current Research 2007-A11 1 S. Meule et al.