b'Geophysics in the surveysNewsFigure 2.Regional AEM survey across the East Resources Corridor, Exploring for the Future Program. At 20 km line spacing, the 32 000 line km survey was completed in less than 3 months by CGG (now XCalibur Multiphysics). Note that the proposed survey gap in South Australia has already been covered with AEM as part of the regional Frome survey (data available from Geoscience Australia). Line plans are schematic only and do notFigure 4.Preliminary inversion results for Mundi Airborne EM survey, 2021. Straddling the NSW/SA reflect the final flight path map. border, the survey complements existing AEM coverage to the west and south. In the image above, blue colours represent resistive terrain and red/yellow colours represent conductive terrain and features. The depth of investigation varies (depending on the resistivity) but is typically around the 300 to 500 m mark.point-by-point basis using so-calledfunction of the detector, and the 3D sensitivity factors to produce estimatestopographic variations in the area. of the elemental concentrations (% K,The method thus replaces gridding, ppm U and ppm Th) on the ground.and incorporates both a topographic The correction assumes flat-earthcorrection and deconvolution of airborne topography. However, abrupt changescount rates to elemental concentrations in elemental concentrations on theon the ground.groundincluding those caused byThe full 3D inversion of gamma-ray change in height of sources stemmingspectrometric data using the method of from topography, produce broadMinty and Brodie (2015) is a significant anomalies at airborne heights, and thisimprovement on the conventional should be corrected for during the dataprocessing procedure. In particular, the processing using deconvolution, or afull inversion shows sharper images, with similar method. better anomaly definition, due to the Minty and Brodie (2015) developeddeconvolution. There are several areas a method for the rigorous inversionwhere the correction is greater than 50 % of airborne line data to a regular grid(Figure 5).of elemental concentrations on the ground. The method accounts for theReferencesdegradation of the gamma signal with distance from the source, the errors inIAEA, 2003. Guidelines for radioelement Figure 3.Approximate area of coverage, Mundithe data, the distribution of radioelementmapping using gamma-ray Airborne EM survey, 2021 sources in the ground, the responsespectrometry data: IAEA-TECDOC-1363, 11 PREVIEW AUGUST 2021'