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    Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's 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 data are 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. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This Magnetic Anomaly Map of Australia, Seventh Edition, 2019 TMI Greyscale image is a greyscale image of the TMI grid of the Magnetic Anomaly Map of Australia, Seventh Edition, 2019. 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. The grid used to produce this greyscale image has a cell size of 0.00083 degrees (approximately 80m). This greyscale image shows the magnetic response of subsurface features with contrasting magnetic susceptibilities. The image can also be used to locate structural features such as dykes.

  • Legacy product - no abstract available

  • This index provides details of the specifications of 1085 airborne geophysical surveys conducted by or for the Australian, State and Territory governments. The data for these surveys are available to the public either through Geoscience Australia or through the relevant State and Territory Geological Surveys. They comprise more than 34 milllion line kilometres of mainly total magnetic intensity and gamma-ray spectrometric data. Land elevation data derived from GPS recordings made during airborne magnetic and gamma-ray spectrometric surveys, and electromagnetic data are also available for some areas. The index is 13th in a series of Geoscience Australia Records which contain regularly updated information as the specifications of surveys already completed are incorporated and as new surveys are added to the National Database.

  • Measurements of the magnetic declination at a proposed compasss-winging site for the R.A.A.F. at Darwin Airport N.T. show that the area nominated is suitable for the purpose.

  • This Record describes the comparison between magnetic field instruments, which had been compared with the standard absolute instruments at Toolangi, and the proton precession magnetograph of Weapons Research Establishment. The observations were made on 27th and 28th June 1960 at Woomera.

  • Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's 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 data are 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. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. These line dataset from the GA302 Capel and Faust Basins MSS survey were acquired in 2006 for Geoscience Australia. This survey acquired a range of pre-competitive geological and geophysical data that included seismic reflection, gravity, magnetic and swath bathymetry measurements, as well as seafloor dredge samples.