| Summary: | Progress Code: completed Statement: Lineage: The grid is derived from data in Geoscience Australia databases and recent sources which will eventually be entered into those databases. Eight swath datasets acquired between 1994 and 2003 were used. Two of the surveys supply extensive areal coverage, whilst the others are basically multibeam transits of the area. Detailed hydrographic data (including a 1999 LADS dataset near the northern tip of Macquarie Island) exists around the island. A high quality coastline of Macquarie Island from the National Mapping Division of G.A. (1994) and a coastline of the New Zealand islands obtained from the NOAA website were used . High quality bathymetric data (post 1997) from Austral Fisheries Pty Ltd were made available via the AAD. Twenty-five surveys from the G.A. MARDAT database. These data range in vintage from 1965 to 1998 and were edited to remove suspect datapoints, but were left uncorrected with regards speed of sound issues. All available data in the area from the AAD voyages in the region. Extensive editing and a weighting scheme were employed to discriminate between closely spaced data of varying vintages. Other trackline data on NGDC and CSIRO websites that were not in MARDAT were also utilised. Satellite derived bathymetry from the SIO website was used to infill areas that had no higher quality observations within a nominal 10 kilometres. Positional accuracy: The grid incorporates data from surveys acquired since 1965. Modern surveys which used GPS have a positional accuracy of 5 - 30 m depending on several factors, while earlier surveys which used dead reckoning and Transit satellite fixes had positions accurate to 50-2000 m depending upon the water depth and strength of currents. These surveys overlap in an irregular distribution and the more extensive, higher quality swath datasets were used to mask data of lower quality and extent. Effectively there are two regions in the grid. One covered by multibeam data of high positional and bathymetric accuracy and the ...
|
|---|