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 grid has a cell size of 0.0006 degrees (approximately 60m). The data used to produce this grid was acquired in 1993 by the WA Government, and consisted of 119231 line-kilometres of data at 300m line spacing and 80m terrain clearance.
This mWA1112E.nc grid is an airborne-derived Total Magnetic Intensity (TMI) grid for the Hamersley Basin, WA, 1993 survey. The survey was acquired under the project No. 1112 for the geological survey of WA. The grid has a cell size of 0.0006 degrees (approximately 60m). A total of 119231 line-kilometres of data at a line spacing of 300m were acquired to produce this grid. To constrain long wavelengths in the grid, an independent data set, the Australia-wide Airborne Geophysical Survey (AWAGS) airborne magnetic data, was used to control the base levels of the survey grid (Milligan et al., 2009). This survey grid is essentially levelled to AWAGS. Details of the specifications of individual airborne surveys can be found in the Fourteenth Edition of the Index of Airborne Geophysical Surveys (Percival, 2014). This Index is also available online at http://pid.geoscience.gov.au/dataset/79134. Further up to date information about individual surveys can also be obtained online from the Airborne Surveys Database at http://www.ga.gov.au/oracle/argus/.
The original grid was converted from ERMapper (.ers) format to netCDF4_classic format using GDAL1.11.1. The main purpose of this conversion is to enable access to the data by relevant open source tools and software. The netCDF grid was created on 2016-08-29T10:51:42, 2013-05-03T00:00:00 and has its y-axis indexed Southward-positive.
Milligan, P.R., Minty, B.R.S., Richardson, M. & Franklin, R., 2009. The Australia-wide Airborne Geophysical Survey accurate continental magnetic coverage. Preview, No. 138, p. 1-128.
Percival, P.J., 2014. Index of airborne geophysical surveys (Fourteenth Edition).