A new era for the Australian National Gravity Grids - adding airborne data to the mix
- 1. Geoscience Australia, GPO Box 378 Canberra ACT 2601
- 2. Geoscience Australia, GPO Box 378 Canberra ACT 2601, yvette.poudjomdjomani@ga.gov.au
- 3. Geoscience Australia, GPO Box 378 Canberra ACT 2601, phillip.wynne@ga.gov.au
Description
Since 1976, Geoscience Australia has produced grids of gravity anomalies to support geological mapping and exploration applications across Australia. The five editions of the national grids up to 2016 have been based on ground gravity observations, supplemented by marine gravity derived from satellite altimetry and once with marine ship track gravity data. In the planning for the sixth edition of the national grids in 2019, and for the first time, the ground gravity observations were supplemented with airborne survey data and marine gravity derived from satellite altimetry. The addition of airborne data required a completely different processing sequence to be devised. An important part of this processing was to vertically continue all observations to a single smooth drape surface defined across the entire extent of the grids. The results show clear benefits over previous editions stemming from the inclusion of the airborne data. Three grids were produced: the Free Air Anomaly (FAA), the Complete Bouguer Anomaly (CBA) and the De-trended Global Isostatic Residual (DGIR) grid. The DGIR grid, which was produced for the first time, is a better product to use for the interpretation of mid and upper crustal features since most long wavelength anomalies have been removed. This outcome points to further airborne data being acquired and included in future national grids. Data from airborne surveys acquired by non-government organisations that meet size and quality criteria will also be considered for inclusion.
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