From 1 - 10 / 1929
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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. These line dataset from the Murrindal, Vic, 1996 VIMP Survey (GSV3060) survey were acquired in 1995 by the VIC Government, and consisted of 15589 line-kilometres of data at 200m line spacing and 80m terrain clearance. To constrain long wavelengths in the data, an independent data set, the Australia-wide Airborne Geophysical Survey (AWAGS) airborne magnetic data, was used to control the base levels of the survey data. This survey data is essentially levelled to AWAGS.

  • These data represent the January 2002 edition of the Magnetic Anomaly Grid of the Australian Region. This version is the first integrated onshore/offshore magnetic anomaly grid for the complete Australian margin extending across 8S - 52S, 106E - 172E. The grid cell size is 0.01 degree (approx. 1 km). Earlier releases were restricted to portions of NW and SW Australia. - Magnetic anomaly unit is nanoTesla (nT). Appropriate IGRFs have been removed. Horizontal datum is GDA94 (which is equivalent to WGS84). - The marine data were levelled independently of the onshore data in three sectors (see below). The NNW and SSW sectors were released as grids previously. The eastern sector was levelled in 2000 in collaboration with Intrepid Geophysics (Melbourne, Australia). The three levelled sectors, together with the unlevelled sectors were combined with the onshore grid to give the present grid. Altogether, 3,022,656 data points are in the database from which the marine grid was created. - Unlevelled sectors: (-8 -25 160 172), (-39 -52 156 172), (-46 -52 106 140) - Levelled sectors: (-37 -52 140 156), (-25 -39 143 172), (-8 -25 143 160), (-24 -46 106 140), (-8 -24 106 143) - There are several places at the join between onshore and offshore grids where the two grids do not match. The problem exists because the onshore grid was developed earlier, and there was poor control on the grid merging process at the margins. Future work will attempt to address this issue and improve the continuity between the onshore and offshore grids.

  • Legacy product - no abstract available

  • Airborne magnetic coverage of the Australian continent is one of the best in the world after more than 60 years of data acquisition by Commonwealth, State and Territory Geological Surveys, complemented by publicly available company data. State and Territory exploration initiatives are mainly responsible for acquisition of high-quality data over the last decade. Nearly eight hundred grids of individual surveys, each optimal for the original acquisition specifications, have been combined in an inverse process to produce a composite grid of the continent with a cell resolution of 3 seconds of arc (approximately 80 m). This grid forms the basis of the recently-released 5th Edition of the Magnetic Anomaly Map of Australia. To constrain long wavelengths, the independent Australia-wide Airborne Geophysical Survey (AWAGS) magnetic data were used to control overlapping survey grids. These AWAGS data were acquired in 2007 by Geoscience Australia as part of the Australian Government's Energy Security Program, and gamma-ray spectrometric data from this survey have been used in production of the first Radiometric Map of Australia. North-south lines were flown with a spacing of approximately 75 km and east-west lines with a spacing of approximately 400 km. Average acquisition height was 80 m above ground level. Very long magnetic wavelengths greater than 1000 km have been constrained using MF6 data derived from the CHAMP satellite. A range of filtered and enhanced products, such as differential reduction to the pole and various derivatives and continuations, are being developed to aid users of the data.

  • Legacy product - no abstract available