A bathymetric Digital Elevation Model (DEM) of Newcomb Bay, Windmill Islands

Full description

A Digital Elevation Model (DEM) of Newcomb Bay, Windmill Islands
and terrestrial and bathymetric contours derived from the DEM.
The data is stored in a UTM zone 49(WGS-84) projection.
Heights are referenced to mean sea level.
It was created by interpolation of point data using Kriging. The input point data comprised soundings and terrestrial contour vertices. THE DATA IS NOT FOR NAVIGATION PURPOSES.

Lineage

Progress Code: completed

Statement: The majority of input data for the Newcomb_bay DEM was derived from the casey_approaches(RAN) dataset, digitised from RAN FairSheets. The vertical datum of the RAN soundings is LAT (Lowest Astronomical Tide). The depths were converted to depths below MSL (Mean Sea Level) vertical datum by adding 0.9 m. This adjustment is given in Section 9 of the report 'Approaches to Casey Station, 15 December 1990 to 12 March 1991' by Lieutenant K.D.Slade. The point data described by the metadata record 'Bathymetric surveys of Brown Bay, O'Brien Bay and Newcomb Bay in the Windmill Islands' were also used as input data where appropriate along the coast. The comma delimited data resulted from bathymetric surveys of Brown Bay, O'Brien Bay and Newcomb Bay by Jonny Stark (AAD) in February and March 1997 includes latitude, longitude and depth fields. Latitude and longitude were obtained by differential GPS. When viewing the Newcomb Bay bathymetric survey soundings in conjunction with the Australian Antarctic Data Centre's coastline data and a Landsat 7 satellite image (path 104, row 107, captured 5 February 2000) it was apparent that there was a horizontal shift in the soundings. This may have arisen due to the problems with establishing the location of the GPS base station. Consequently, in consultation with Johnny Stark, a horizontal shift was applied to the soundings. The shifts applied were: easting -37 m, northing 0 m. The point data were thinned out. Data from O'Brien Bay'Tape 1a_utm'and Brown Bay bathymetric survey data were also point-thinned, clipped and used as input data. The soundings were explored using the ArcGIS Geostatistical Analyst extension ESDA tools to identify and remove outliers in the data. Soundings that seemed irregular were deleted. Soundings that were positioned above the current coastline data were deleted although the coastline data were not used as input data for the dem. The contour vertices were extracted from oracle (dataset_id 138, Qinfo 18). All these data were combined in to one shapefile called 'elevationall_utm' and used to derive the DEM.(20m cell size) The DEM (20m cell size) was created using the Geostatistical Analyst extension in ArcGIS 9.2, with the input data projected in UTM zone 49S. Using the Geostatistical Analyst extension: The input data was split into a training and validation (test) dataset. The DEM was interpolated from the training dataset using a Kriging method; the DEM was cross validated using the training dataset; and the DEM was validated using the test dataset. Contours at 10m intervals were generated from the DEM using the Spatial Analyst extension. Contours were smoothed and simplified using a tolerance of 20m . Contours greater than zero were exported to a terrestrial contour dataset called Contour_ln. Contours less than or equal to zero were exported to a bathymetric contour dataset called Bath_contour_ln. The zip file available for download includes the training and test datasets as shapefiles, the DEM in ESRI's ArcInfo interchange and ASCII formats, files documenting the Kriging method and the validation results, and the terrestrial and bathymetric contours derived from the DEM. Must be cited properly. Usually mapped to a Universal Transverse Mercator projection, Zone 49S, Datum WGS-84.