Updated: 28 June 2005

AUSGeoid98 Data Files

Download Data Files

Files information

AUSGeoid98 data files contain a 2 minute grid of AUSGeoid98 data covering the Australian region, which you can use to interpolate geoid-ellipsoid separations for the positions required. You can use your own interpolation software, or you can use Geoscience Australia's Windows Interpolation software (Winter).

The data files are text files in a standard format that cover the same area as standard topographic map areas. Files covering both 1:250,000 (approximately 100 x 150 km) and 1:1,000,000 (approximately 400 x 600 km) map areas are available. There is a 4 minute overlap on all sides of each area.

A 2 minute grid of geoid-ellipsoid separations and deflections of the vertical, derived using the EGM96 coefficients and the National Imagery and Mapping Agency's (NIMA) software, is available in AUSGeoid format, for Australian External Territories not covered by AUSGeoid98:

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Download Data Files

These 1:250,000, 1:1,000,000, and External Territories map area files are available as free downloads, in zip format (Windows compatible), either from the Geoscience Australia free data downloads system (www.ga.gov.au/products/), where you can also download additional products in various formats, or from the forms below. Helpful hints for using the free data downloads page:

Click the "geodesy" checkbox before searching for the map sheet name or number.
The format of the zip files are "catalogue number_map sheet number.zip" (eg 61935_sb48-16.zip for the 1:250,000 areas; 63340_sb48.zip for the 1:1,000,000 areas; and 63488_macquarie.zip for the External Territories areas). Once unzipped the data file's format is "mapsheet number(or name).dat" (eg sb48-16.dat for the 1:250,000 areas; SB48.dat for the 1:1,000,000 areas; and macqnima.dat for the External Territories areas).

The Product Search Index page is available, where you can search by map or text, to determine your required files.

1:250,000 areas:
sb-sl: 48-57: 01-16:

Note: The NIMA algorithm used to generate the above five files applies additional corrections to the EGM96 N values: an offset of -0.53 m to align it to the WGS84 ellipsoid and a terrain correction. This means that these files will differ from the "pure" EGM96 N values provided from this site before August 2002. The difference is about half a metre in an absolute sense, but will generally have little effect in a relative sense (differences in N value). Care must be used if you are using data derived with the different types of files. The linked AUSGeoid98 data files above are unchanged.

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For more information contact: geodesy@ga.gov.au

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