AUSGeoid98

AUSGeoid98 is the current model in a series of national geoid models for Australia produced by Geoscience Australia. It replaced AUSGeoid93 and uses the latest available data and techniques.

AUSGeoid98 consists of a 2' by 2' grid (approximately 3.6km) of geoid-ellipsoid separations (N Values) relative to the GRS80 ellipsoid, which is also used for the new Geocentric Datum of Australia (GDA94). These values are suitable for use with Global Positioning System (GPS) and will improve the achievable accuracy of Australian Height Datum (AHD) height transfer using GPS.

The format of the AUSGeoid98 data files is nearly identical to the superseded AUSGeoid93 data files.

Because AUSGeoid98 is provided on a 2 minute by 2 minute grid by virtue of the use of the fast fourier transform, a value interpolated from the AUSGeoid98 data is the best value you can obtain.

[back to top]

Data Processing

You may use your own software to interpolate an N value from the AUSGeoid98 data files, or you may use Geoscience Australia's Windows Interpolation software (WINTER). WINTER requires Windows95/98/NT and will interpolate interactively (one point at a time) or in batch mode (a file of positions) using a bilinear or bicubic interpolation. The program can be "taught" to read almost any text file of positions, provided there is one position per record. The positions used to interpolate the data should be on the GDA94/WGS84.

AUSGeoid98 data files and the WINTER interpolation software are freely available, and you are encouraged to use them for your projects. However, you may not charge others for this data and software.

Those who wish to include this interpolation process in their own systems can use the explanation in the attached file [PDF_321k]. A 46k spreadsheet implementation of the algorithm is also included to allow testing and diagnosing of any implementation.

[back to top]

AUSGeoid98 contour map

[back to top]