This gravity anomaly image has been derived from observations stored in the Australian National Gravity Database (ANGD) as at February 2016 as well as data from the 2013 New South Wales Riverina gravity survey. The data used to produce this image was the Complete Bouguer Gravity Anomaly Grid of Onshore Australia 2016. The complete Bouguer grid has been image enhanced and displayed as a hue-saturation-intensity (HSI) image with sun shading from the northeast. Out of the approximately 1.8 million gravity observations 1,371,998 gravity stations in the ANGD together with 19,558 stations from the Riverina survey were used to generate this image. The image shows complete Bouguer anomalies over onshore continental Australia. The data used in this image has been acquired by the Commonwealth, State and Territory Governments, the mining and exploration industry, universities and research organisations from the 1940's to the present day.

Continental Australia has a base coverage of 11 kilometres, with South Australia, Tasmania and part of New South Wales covered with gravity stations at a spacing of 7 kilometres. Victoria has station coverage of approximately 1.5 kilometres. Federal, State and Territory Government initiatives have systematically infilled at a station spacing of 2 to 4 kilometres to improve coverage in areas of scientific or economic interest. Other areas of detailed coverage have been surveyed by private companies for exploration purposes. Only open file data held in the ANGD at February 2016 were used in the creation of the grid. The 2013 Riverina survey was added to the gridding process as this survey was not in the ANGD at the time.

The 2009 Bathymetry and Topography grid of Australia (Whiteway, 2009) and the 3 second Shuttle Radar Topography Mission (SRTM) Smoothed Digital Elevation Model (DEM-S) (Gallant et al., 2011) were used as the elevation models to calculate the Bullard C terrain corrections. These terrain corrections have been calculated using software from Intrepid Geophysics(1). The Intrepid algorithm utilises concentric rings subdivided into cells (Direen, 2001). The SRTM was used for the onshore terrain correction using five rings with a starting cell size of 90 metres resulting in a final radius of 92.2 kilometres. Four rings were used for the offshore terrain correction with a starting cell size of 250 m and a final radius of 64.0 km. The densities of materials used in the terrain corrections were 2670 kg/m^3 for land, 2200 kg/m^3 for marine sediments and 1027 kg/m^3 for sea water. The offshore and onshore terrain corrections were combined and applied to the spherical cap Bouguer anomalies used in the Bouguer Gravity Anomaly Grid of Onshore Australia 2016 to produce the complete Bouguer anomaly values shown in this image.

The Complete Bouguer Gravity Anomaly Grid of Onshore Australia 2016 has been image enhanced and displayed as a hue-saturation-intensity (HSI) image with sun shading from the northeast to create this product.

References:

1 http://www.intrepid-geophysics.com

Direen, N. G., 2001. Application of terrain corrections in Australia (2001). Geoscience Australia, Canberra. https://pid.geoscience.gov.au/dataset/ga/33808

Gallant, J.C., Wilson, N., Dowling, T.I., Read, A.M., and Inskeep, C., 2011. SRTM-derived 3 Second Digital Elevation Models Version 1.0. Geoscience Australia, Canberra. https://pid.geoscience.gov.au/dataset/ga/72760

Whiteway, T. G., 2009. Australian Bathymetry and Topograhy Grid, June 2009. Geoscience Australia, Canberra. http://dx.doi.org/10.4225/25/53D99B6581B9A