Radiometric Grid of Australia (Radmap) v4 2019 ratio thorium over potassium

Brief description

This record was harvested by RDA at 2025-03-05T09:51:51.968+11:00 from NCI's Data Catalogue where it was last modified at 2018-04-20T05:51:54.

Full description

The thorium over potassium grid is a derivative of the 2019 radiometric or gamma-ray grid of Australia. The radiometric, or gamma-ray spectrometric method, measures the natural variations in the gamma-rays detected near the Earth's surface as the result of the natural radioactive decay of potassium (K), uranium (U) and thorium (Th). The data are collected on airborne geophysical surveys conducted by Commonwealth, State and Northern Territory Governments and the private sector. The 2019 thorium over potassium was derived by seamlessly merging over 600 airborne gamma-ray spectrometric surveys. The final grid has a cell size of about 100m (0.001 degrees) and is derived from the filtered thorium and potassium grids. -- This record represents data published by NCI. It uses catalogue metadata modified from Geoscience Australia. See our Record Lineage Information for more details.

Lineage

The thorium over potassium ratio grid is a derivative of the 2019 radiometric or gamma-ray grid of Australia. The radiometric grid of Australia is derived by merging over 600 airborne gamma-ray spectrometric surveys by the Commonwealth, State and Territory Governments and held in the national radioelement database of Australia. The cell sizes of the original survey grids range from 50 m through 800 m, but most have a cell size of about 100 m. The original survey grids were re-levelled and then re-sampled to generate the Radiometric Map of Australia grids with a cell size of about 100m (0.001 degrees). The data quality varies depending on the survey. The data were processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. Thorium over potassium ratio grid was calculated after first applying a low value 'clip' to the thorium and potassium grid values - i.e. any values less than 0.1 are set to 0.1 prior to ratioing. This clipping will necessarily introduce some artefacts into the ratio grids in areas of very low radioelement concentrations.The final grid is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose.