Australian National Gravity Anomaly Grid with Half Vertical Derivative

National Gravity Compilation 2019 is a processed geophysical grid showing half vertical derivative of de-trended global isostatic residual anomalies. The compilation integrates nearly 1.4 million ground stations and over 450,000 line kilometers of airborne gravity and gradiometry data, processed by Geoscience Australia and partners. It synthesizes observations from the 1940s to 2019, with the grid released in 2019.

Use Cases

• Map subsurface density contrasts and geological structures using the half vertical derivative (0.5VD) grid values.
• Interpret crustal architecture and isostatic compensation by analyzing de-trended global isostatic residual (DGIR) anomalies.
• Integrate airborne gravity gradiometry line data with ground station observations to improve resolution in under-sampled regions.
• Model near-field and far-field isostatic corrections by comparing the DGIR grid to the Complete Bouguer Anomaly (CBA) source data.

Strengths

• Integrates approximately 1.8 million gravity observations from nearly 1.4 million ground stations.
• Includes 345,000 line km of airborne gravity and 106,000 line km of airborne gravity gradiometry data for enhanced resolution.
• Grid cell size is 0.00417 degrees (approximately 435 meters), providing continent-scale detail.
• Data quality is checked by Geoscience Australia geophysicists to ensure fitness-for-purpose.

Limitations

• Ground station spacing is irregular, varying from 11 km to less than 1 km, creating variable data density.
• Temporal coverage spans from the 1940s to 2019, introducing potential inconsistencies in older measurement techniques.
• Airborne survey line spacing ranges from 0.5 km to 2.5 km, resulting in non-uniform resolution across the grid.

Provenance

Source

Geoscience Australia, sourced from the Australian National Gravity Database and global grids from Scripps Institution of Oceanography/NOAA/NGA.

Collection Method

Data processed from ground observations, airborne surveys, and offshore global grids, with DGIR calculation and half vertical derivative applied via Fast Fourier Transform.

Time Range

1940s to 2019 (observation period); grid represents 2019 compilation.

Freshness

Grid is based on data as of September 2019; metadata was last updated in April 2026.

Geography

Australia and its continental margins.