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SONAR
2 record(s)
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draft
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This dataset contains the Underway (UWY) data collected on Linnaeus voyage LI2014_V23. Voyage Title: Transit Hillarys Boat Harbour to Fremantle. The voyage took place on the 3rd December 2014 from Hillarys boat harbour returning to Hillarys boat harbour. The Underway (=continuously recorded) dataset from this research voyage includes Navigation (NAV), Sounder, and se-surface temperature data. NAV data includes GPS (Global Positioning System) measurements of latitude, longitude, ship's direction and speed. Data are stored at 5 second intervals (NetCDF) and both 10 second 5 minute intervals (.csv format), including a 10 second PDR (Precision depth recorder) file in .csv format. Additional information regarding this dataset is contained in the data processing report for this voyage.
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These data are the result of Geoscience Australia survey 266 to the central Torres Strait region, with the survey being the first of two by Geoscience Australia carried out in 2004. They form part of a larger field-based program managed by the Torres Strait CRC aimed at identifying and quantifying the principal physical and biological processes operating in Torres Strait. The impetus for the program is the threat of widespread seagrass dieback and its effects on local dugong and turtle populations and the implications for indigenous islander communities. The principal aim of the survey was to investigate the seabed geomorphology and sedimentary processes in the vicinity of Turnagain Island and to infer the possible effects (if any) on the distribution, abundance and survival of seagrasses. The Turnagain Island region was chosen because it is a known site of recent widespread seagrass dieback. The survey consisted of a detailed geophysical survey using swath (multi-beam) sonar and shallow seismic equipment that was supplemented with a detailed sampling program consisting of 301 near-bed water samples, 54 seabed grabs, 5 vibrocores and 69 camera stations. Four oceanographic moorings were also deployed for the duration of the survey to measure the local tide, wave and wind-driven currents. A regional survey was initially undertaken, followed by a detailed study of two areas: Area A - located approximately 2.5 km SW of Turnagain Island which contained sand ridges and seagrass beds, and Area B - located approximately 2.0 km SE of Turnagain Island which contained sandwaves and no seagrass beds. In a new application of the swath (multi-beam) data, the total volume of sediment transported during the survey was estimated from changes in the high-resolution seabed bathymetry collected during the repeat surveys. Preliminary results of the study found that seagrasses in the region are subject to frequent and significant changes in environmental conditions, with implications for limited dispersal and survival. A follow-up survey was undertaken in October 2004.