Abstract:
A Digital Elevation Model (DEM) of Heard island, with a 50 metre grid interval, and held in UTM Zone 43(WGS-84) coordinates. Heights are referenced to mean sea level. 50 metre contours (including a coastline) were derived. Elevation range 0 - less than 2800m.
Quality
The Australian Antarctic Division (AAD) DEM is based on a DEM produced by Intermap Technologies from Stereoscopic RADARSAT images acquired in March and April of 1997. Heights in the AAD DEM were referenced to the WGS-84 ellipsoid. The AAD DEM was produced by subtracting 40 metres from all vertices in the Intermap DEM. 40 metres is the average geoid-ellipsoid separation, modelled from EGM-96, in ... the area of Heard Island. The AAD DEM was then combined with a coastline and any vertices within the coastline having negative heights were corrected to 2 metres. Any vertices outside the coastline having positive values were corrected to 0 metres. The coastline was digitised off the 1:50,000 image map published in 1991 by the Australian Antarctic Division. The AUSLIG (now Geoscience Australia) AMBIS program revised this coastline with reference to available photography. DEM are referenced to mean sea level. The Intermap DEM was positioned horizontally to ground control (corner cube reflectors) which was coordinated using dual frequency baselines. These points where all referenced to the Pageos Mark at Atlas Cove (coordinate obtained from the National Geodetic database, held by Geoscience Australia). Also available is a Virtual Reality Markup Language (VRML) scene of Heard Island. This scene has been generated from a highly decimated version of the DEM data. The scene has been exaggerated, vertically 1.5X. The DEM is for Heard Island only. It does not include the McDonald Islands. DEM parameters ncols 865 nrows 525 x coordinate of lower left corner 382275 metres y coordinate of lower left corner 4104775 metres cellsize 50 metres NODATA_value -9999 50 metre contours where interpolated from the corrected DEM. Thus these contours and DEM are referenced to mean sea level. Derived contours have been edited to ensure that they do not cross the coastline and do not overlap. The contour dataset is for Heard Island only. It does not include the McDonald Islands. An earlier contour dataset was digisted from the 1:50,000 Heard Island map, edition 3, published in 1985. This dataset is now redundant.
Access Constraints
Coastline and 50 metre contours are stored in DXF format and Arc/Info export format. The DEM is stored as a dem.asc - Arc/Info GridASCII format (Grid) and demgrid.e00 - Arc/Info export format (Grid). A dem.prj projection parameter file is also included.
Must be cited properly. Usually mapped to a Universal Transverse Mercator projection, Zone 43.(Central meridian E75), UNITS METRES, SPHEROID GRS80, DATUM WGS-84
This
"Heard Island RADARSAT (1997) DEM" is licensed under a Creative Commons Attribution 3.0 Unported License.
