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Initial development of an amphibious ROV for use in big surf
Abstract
A remotely operated vehicle is being developed as a general workhorse for performing a variety of scientific and engineering tasks in shallow coastal waters. The vehicle, called the Surf Rover, is essentially a low-slung tripod, nominally 7-m long, 5-m wide and 1.5-m tall, that rides on two hydraulically driven tracks and a free-spinning caster wheel. At present the vehicle is powered by an umbilically supplied electric motor and controlled by radio. Initial field testing indicates that the Surf Rover is both rugged and stable in breaking waves almost 2 m in height. Because the vehicle can be folded into a narrow configuration, it is easily transported by truck or trailer and requires only a footpath to gain access to the beach. Operations can be conducted with a crew of two people. Conversion to a snorkel-aspirated engine is planned, which will complete proof-of-concept. -Authors
... This 8.2-ton technology carries a prism for an ETS located inland. Dally et al. [14] reported other ROV for the breaker zone, called Surf Rover, which solves the problem of mobility in different types of soil and access to them. The Surf Rover consists of a structural frame with two front arms and caterpillar wheels, an airtight container protecting energy, hydraulics, and control equipment, and a wheel in the tail. ...
An underwater caterpillar vehicle has been designed and developed to profile along the beach and shoreface. This prototype is employed for zones that are unsuitable to study through bathymetry or manual measurements. The system consists of a metallic structure propelled by two caterpillar tracks. An electronic accelerometer and a GPS receiver measure the profile data. These components provide the seabed slope and the traveled distance along a path. The data are recorded locally and transmitted to a host computer with a radio modem, conforming a wireless duplex link, which is also used for controlling the vehicle and reporting the status. The profiler system has been tested in several zones in the Pacific Coast of the Baja California Peninsula, Mexico and the results were compared with an Electronic Total Station. Based on the obtained results, the underwater caterpillar system evinces to be a reliable profiler option.
Accurate documentation of beach and nearshore morphology is an essential component of coastal research and management. The Beach Erosion Research and Monitoring (BERM) program has been addressing this need through field intensive surveys for over a decade. Throughout this period BERM survey methods have evolved from conventional rod-level and sled-based profilers to our current acquisition method that couples Real-Time Kinematic GPS with shallow-water sonar. The introduction of these instruments has not only allowed for rapid and accurate collection of cross-shore profiles, but enabled acquisition of detailed alongshore data in a spatial context that was previously unachievable. Although the availability of this technology provides a more efficient means to measure the beach and nearshore, it remains vital to use the most appropriate survey design, one which will provide the most reliable and useful data for analysis. To determine the amount of data required to accurately represent beach and nearshore morphology in three dimensions, we designed an experiment within a 1400 m by 600 m survey area where we collected both shore-normal and shore-parallel data from the dune to a water depth of 8 m. Data specific interpolation algorithms, with strong anisotropy and optimal gridding parameters were applied to the data and the topographic output was systematically analyzed. Preliminary results indicate that utilizing only shore-normal data leads to interpolation artifacts, volume inaccuracies and only partially represents the true morphology. Analyses that make use of both shore-parallel and shore-normal data significantly reduce artifacts and provide more accurate representations of morphology and volume change. INTRODUCTION Scientists, engineers, and managers have long sought to quantify beach and nearshore morphology in order to understand the processes that influence a wide range of scientific and socioeconomic issues. The importance of monitoring coastal morphology has become critical in recent years as populations within the US coastal zone expand; this growth creates additional demand for state and federal funding to protect coastal development, shoreline habitats, recreational beaches, and economies. In order to
Coastal scientists recognize that while it is critical to quantify volumetric and repeatable spatio-temporal change near tidal inlets, various physical and morphological factors make these areas perhaps the most challenging regions to map. It has been well established that traditionally spaced transects perpendicular to the morphology do not accurately represent complex terrain when interpolated into a digital elevation model (DEM), regardless of gridding algorithm. Purpose-built acquisition platforms paired with modern singlebeam, multibeam and topographic instrumentation are necessary for accurate surveys of this environment. Equally important to the accuracy of the final DEM is survey planning such that potential sources of survey uncertainty are minimized. Remote sensing techniques and observational data (e.g., aerial photography, nautical charts and existing data) are used to develop predictions of the anticipated terrain. Customized survey designs increase survey efficiency and allow users more flexibility in gridding methods and contribute to the overall accuracy of the modeled surface geometry. The selection of gridding parameters depends largely on the spatial distribution of the input data, resolution of the output grid and the characteristics of the modeled terrain. Survey design, instrumentation and interpolation methods are of principal importance when constructing accurate and seamless topo/bathy elevation models of these challenging environments.
This paper presents an overview of field methods, data collection, and analysis procedures applied to four key coastal data sets used in monitoring and baseline studies: aerial photography, satellite imagery, profile surveys, and bathymetric (hydrographic) records. Often, aerial photographs and satellite images, after rectifying and georeferencing, serve as base maps to interpret landform changes and quantify shoreline movement. Large-scale topographic and hydrographic maps are the primary sources for shoreline position and volumetric change computations. Profile surveys, available from many Federal and local agencies and universities, can also be used to evaluate shoreline changes and compute beach volume changes along and across the shore. Frequently, post-processing steps are required to normalize these data to the same coordinate system and vertical datum prior to quantifying changes for a coastal area. For example, project-specific bathymetric data in the United States is often potted using State Plane coordinates, while hydrographic data from NOAA is supplied with latitude/longitude coordinates. Maps, surveys, and aerial photographs are available from Federal agencies such as the USGS, NOAA, and the Corps of Engineers. These long-term data records can be used to evaluate natural and man-made changes to a coastal system. The resultant statistics and volumetric calculations should be presented in terms of the regional and local conditions, i.e., storm history, seasonality, wave climate, man-made environmental and engineering changes, and large- and small-scale landforms.
The development of coastal sediment budgets and models for sediment transport and shoreline change require bathymetric surveys with vertical resolution and accuracy of 5 cm or better. Horizontal resolution and accuracy need to be at least 10 cm to quantify bedforms and bars. Sleds are probably the most accurate, widely used system for nearshore surveys, but their contact with the bottom limits their speed, spatial resolution, and ability to operate in many situations. Boat-based echo sounder surveys can achieve a higher spatial resolution and can operate where sleds cannot, but waves, tides, and other water-level fluctuations as well as boat dynamics and variations in the speed of sound in water can greatly limit their accuracy. Problems related to a survey sleds contact with the bottom cannot be overcome; therefore, echo sounder surveys must be improved. The newly developed high-accuracy, high-resolution bathymetric surveying system (HARBSS) is designed to overcome the confounding effects of changing vessel draft, waves, and tides on depth soundings and to eliminate the need for measuring and modeling water level for a particular survey. The system combines Global Positioning System (GPS) receivers, an electronic motion sensor, a digital-gyro compass, a digital-analog echo sounder, a conductivitytemperature-depth probe (CTD), a computer, and custom software. The GPS antenna, compass, and motion sensor are aligned with the echo sounder's transducer. Using a bias-free phase solution from the GPS data (X,Y,Z accuracy of better than I cm), attitude information from the motion sensor, and heading information from the compass, the position and aim of the transducer is determined for each sounding. The CTD provides data to calculate the speed of sound. Using the above data, the sounding depths and horizontal locations of sounding points are corrected in X,Y, and Z with respect to an Earth-centered ellipsoid. In constant and uniform speed-of-sound conditions, HARBSS can provide soundings that are within 5.2 cm (mean error of 3.7 cm) of their true elevations. Horizontal accuracy is estimated to be within 10 cm. This accuracy can be achieved from a small, open boat that is rolling, pitching, heaving, or listing. Error analysis indicates that we may be able to decrease the error by one half with better synchronization and interpolation of the various data streams.
Rapid, comprehensive measurements of coastal ocean processes are often difficult to acquire, particularly in shallow water. A novel personal watercraft-based system for rapidly measuring coastal hydrography in shallow waters has been developed, and field-tested, to overcome traditional limitations of hydrographic data collection. The three-person personal watercraft, capable of safely acquiring measurements in water depths < 0.8 m, provides a stable, robust, agile, and inexpensive platform for measuring bathymetry, currents, and comprehensive nearsurface water chemistry. The personal watercraft is outfitted with a bottom tracking acoustic Doppler current profiler; a real-time kinematic differential global positioning system; a handheld temperature and salinity profiling device; a suite of sensors for underway sampling of near-surface water chemistry; and a small five-parameter meteorological station. Typical horizontal resolution of bathymetry and water velocity is O[1 m]. Continuous underway sampling of near-surface water chemistry parameters occurs via a custom designed ram intake and diaphragm pump. Sampling of near-surface water chemistry can be conducted at speeds as high as 20 m/s, allowing for rapid surveys with large spatial coverage. Measurements of near-surface hydrography yield horizontal resolutions of O[1 m]-O[100 m] depending on vessel speed and sampling frequency. Surveys have been conducted in Mobile Bay, Alabama, a nearby river, and a local reservoir; pertinent results from field deployments of this system are discussed and demonstrate the utility and capabilities of this unique measurement platform, particularly the ability to perform nearsynoptic measurements of coastal ocean processes with the express purpose of minimizing tidal bias.
Accurate documentation of beach and nearshore morphology is an essential component of coastal research and management. The Beach Erosion Research and Monitoring (BERM) program has been addressing this need through field intensive surveys for over a decade. Throughout this period BERM survey methods have evolved from conventional rod-level and sled-based profilers to our current acquisition method that couples Real-Time Kinematic GPS with shallow-water sonar. The introduction of these instruments has not only allowed for rapid and accurate collection of cross-shore profiles, but enabled acquisition of detailed alongshore data in a spatial context that was previously unachievable. Although the availability of this technology provides a more efficient means to measure the beach and nearshore, it remains vital to use the most appropriate survey design, one which will provide the most reliable and useful data for analysis. To determine the amount of data required to accurately represent beach and nearshore morphology in three dimensions, we designed an experiment within a 1400 m by 600 m survey area where we collected both shore-normal and shore-parallel data from the dune to a water depth of 8 m. Data specific interpolation algorithms, with strong anisotropy and optimal gridding parameters were applied to the data and the topographic output was systematically analyzed. Preliminary results indicate that utilizing only shore- normal data leads to interpolation artifacts, volume inaccuracies and only partially represents the true morphology. Analyses that make use of both shore-parallel and shore- normal data significantly reduce artifacts and provide more accurate representations of morphology and volume change.
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