national geophysical compilation
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Total magnetic intensity (TMI) data measures variations in the intensity of the Earth magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The 2019 Total magnetic Intensity (TMI) grid of Australia has a grid cell size of ~3 seconds of arc (approximately 80 m). This grid only includes airborne-derived TMI data for onshore and near-offshore continental areas. Since the sixth edition was released in 2015, data from 234 new surveys have been added to the database, acquired mainly by the State and Territory Geological Surveys. The new grid was derived from a re-levelling of the national magnetic grid database. The survey grids were levelled to each other, and to the Australia Wide Airborne Geophysical Survey (AWAGS), which serves as a baseline to constrain long wavelengths in the final grid. It is estimated that 33 500 000 line-kilometres of survey data were acquired to produce the 2019 grid data, about 2 000 000 line-kilometres more than for the previous edition.
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This gravity anomaly grid is 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. Out of the almost 1.8 million records in the ANGD approximately 1.4 million stations together with 19,558 stations from the Riverina survey were used to generate this grid. This product shows spherical cap Bouguer anomalies over onshore continental Australia. The data used in this grid 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. The spherical cap Bouguer anomalies in this grid are the combination of Bullard A and B corrections to the Free Air anomaly values using a density of 2670 kg/m^3.
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The uranium over thorium grid is a derivative of the 2019 radiometric or gamma-ray grid of Australia which is a merge of over 600 individual gamma-ray spectrometric surveys. 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 uranium over thorium grid has a cell size of about 100 m (0.001 degrees) and is derived from the filtered uranium and thorium grids.
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The filtered 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, uranium and thorium. The data are collected on airborne geophysical surveys conducted by Commonwealth, State and Northern Territory Governments and the private sector. The 2019 filtered potassium grid has a cell size of about 100m (0.001 degrees) and shows potassium element concentrations of the Australia region. It was obtained by applying a low-pass filter to the original potassium grid. Potassium is the seventh most abundant element in the Earth's crust. This potassium concentration grid can be used to locate minerals and compounds containing potassium.
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This gravity anomaly grid is 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. 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 grid. The grid shows complete Bouguer anomalies over onshore continental Australia. The data used in this grid 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. Terrain corrections to gravity were calculated using both offshore bathymetry and onshore topography data. These terrain corrections were 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 grid.
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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.
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The uranium over potassium grid is a derivative of the 2019 radiometric or gamma-ray grid of Australia comprising over 600 airborne gamma-ray spectrometric surveys. 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 uranium over potassium grid has a cell size of about 100 m (0.001 degrees) and is derived from the filtered uranium and potassium grids.
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The uranium squared over thorium 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 uranium squared over thorium 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 uranium and thorium grids.
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The unfiltered uranium grid is a derivative of the 2019 radiometric or gamma-ray grid of Australia which is a merge of over 600 individual gamma-ray spectrometric surveys. 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, uranium and thorium. The data are collected on airborne geophysical surveys conducted by Commonwealth, State and Northern Territory Governments and the private sector. The 2019 unfiltered uranium grid has a cell size of about 100m (0.001 degrees) and shows uranium element concentrations of the Australia region.
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Total magnetic intensity (TMI) data measures variations in the intensity of the Earth magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The first vertical derivative (1VD) grid is derived from the 2019 Total magnetic Intensity (TMI) grid of Australia which has a grid cell size of ~3 seconds of arc (approximately 80 m). As the vertical derivative filter is essentially a high-pass filter, longer wavelengths are suppressed, and shorter wavelengths emphasized. The magnetic units of the data are in nT per metre.