National Gravity and Magnetic Derivatives Customised for Data Analysis and Machine Learning

<div><strong>Purpose</strong></div><div>This package comprises a set of 86 thematic grids (rasters) derived from national coverages of gravity and magnetic survey data. These datasets provide valuable information about the distribution of geological features, physical property variations, and the composition of the Earth's crust. All grids have been resampled to the same cell size, map extent, and projection to allow them to be integrated into predictive mapping and modelling workflows using machine learning. Users can download individual grids or the whole grid package. </div><div> </div><div><strong>Input Data</strong></div><div>The following Australian national datasets were used:</div><div>1.     2019 Australian National Gravity Grids: Free Air Anomaly, Complete Bouguer Anomaly, De-trended Global Isostatic Residual, 400 m cell size (Lane <em>et al</em>., 2020).</div><div>2.     Total Magnetic Intensity (TMI) Grid of Australia 2019 - seventh edition Enhanced Products Package (Morse, 2020).</div><div><br></div><div><strong>Processing</strong></div><div>All processing of the national grids were undertaken using Intrepid software. The following was performed on the input data:</div><div>1.     The grids were reprojected from GDA94 geodetic to Australian Albers (EPSG 3577). </div><div>2.     The grids were aligned to the same grid cell registration point and interpolated to fit within an 80 m cell size using a cubic spline method to ensure that the cell locations for all images are common.</div><div>3.     Various Fast Fourier Transforms (FFT) were applied to each grid (see ‘Grids_for_Machine_Learning_dataset_notes.pdf’). </div><div> </div><div><strong>Metadata (all grids)</strong></div><div>·       Datum: GDA94</div><div>·       Projection: Australian Albers (EPSG 3577)</div><div>·       Cell size: 80 m</div><div>·       File format: GeoTiff (.tif)</div> <b>Data is available on request from clientservices@ga.gov.au - Quote eCat# 149130</b>

Total Magnetic Intensity (TMI) greyscale Image of Australia 2019 with Variable Reduction to Pole (VRTP)

This image is a greyscale image of the Total Magnetic Intensity (TMI) Anomaly Image of Australia with Variable Reduction to Pole (VRTP). Total magnetic intensity (TMI) data measures variations in the intensity of the Earth magnetic filed 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. A variable reduction to Pole is aimed at locating magnetic anomalies exactly above their source bodies and without any distortion. The image is created from the 2019 variable reduction to Pole of the TMI grid with a grid cell size of ~3 seconds of arc (approximately 80 m). This image only includes airborne-derived TMI data for onshore and near-offshore continental areas. The image provides a better interpretation of the magnetic data by giving an accurate location of magnetic source bodies.

Airborne Magnetic and Radiometric Technical Standards - Data Acquisition, Processing and Supply

<div>This document defines the technical standards set by Geoscience Australia for the acquisition, processing and supply of airborne magnetic, horizontal magnetic gradient and radiometric (gamma-ray spectrometric) data. The technical standards cover the requirements for equipment, calibrations, quality control checks, reporting and data formats for airborne surveys.</div><div><br></div><div><br></div><div><strong>Table of Contents</strong></div><div><br></div><div>Attachment 1A – Data Acquisition and Processing</div><div><br></div><div>1 Aircraft</div><div>2 Flight and Tie Lines</div><div>3 Global Navigation Satellite System (GNSS)</div><div>4 Parallax Correction</div><div>5 Altimeter</div><div>6 Barometer</div><div>7 Digital Elevation Model</div><div>8 Magnetic System Equipment</div><div>9 Magnetic Gradient System Equipment</div><div>10 Magnetic / Gradient Calibration and Quality Tolerances</div><div>11 Magnetic Base Station (Diurnal Monitoring)</div><div>12 Magnetic Data Reduction</div><div>13 Magnetic Gradient Data Reduction</div><div>14 Radiometric System Equipment</div><div>15 Radiometric Calibration and Quality Tolerances</div><div>16 Radiometric Data Reduction</div><div><br></div><div>Attachment 1B – Reporting and Data Supply</div><div><br></div><div>1 General</div><div>2 Calibration Report</div><div>3 Daily Acquisition Report</div><div>4 Weekly Acquisition Report</div><div>5 Operations and Processing Summary Report</div><div>6 Supply Schedule</div><div><br></div><div>Attachment 1C – Data Formats</div><div><br></div><div>1 General</div><div>2 Point-Located Data Files</div><div>3 Definition Files</div><div>4 Description Files</div><div>5 Raw-Edited Magnetic Data File</div><div>6 Reduced Magnetic Data File</div><div>7 Diurnal Magnetic Data File</div><div>8 Raw-Edited Magnetic Gradient Data File</div><div>9 Reduced Magnetic Gradiometry Data File</div><div>10 Raw-Edited Radiometric Data File</div><div>11 Reduced Radiometric Data File</div><div>12 Gridded Data Files</div><div>13 Image Enhanced GeoTIFF Files

Total Magnetic Intensity (TMI) Grid of Australia 2019 - seventh edition Enhanced Products Package

Several products were produced from the Total Magnetic Intensity (TMI) Grid of Australia 2019, seventh edition (eCat ID 131505). The grid was found to include 3 extreme, high-amplitude cultural data spikes from current and historical aluminium smelters in Victoria and Tasmania. Also, 3 data spikes of unknown origin were located in the Hunter region of NSW. These 6 data spikes were removed from the gridded data. The following products were produced from the grid with the data spikes removed: 1. Total Magnetic Intensity (TMI) edited grid (.ers) 2. Variable Reduction to Pole (VRTP) grid (.ers) 3. First Vertical Derivative (1VD) grid (.ers) 4. Half Vertical Derivative (05VD) grid (.ers) 5. Pseudo-Gravity (PGrav) grid (.ers) 6. Pseudo-Gravity, Total Horizontal Derivative (THD) grid (.ers) 7. Susceptibility (Sus) grid (.ers) 8. Variable Vertical Gradient (VBzz) grid (.ers) 9. Analytic Signal (AS; Total Gradient) grid (.ers) 10. Tilt Angle (Tilt; Phase Map) grid (.ers) 11. Tilt Angle (Tilt; Phase Map), Total Horizontal Derivative (THD) grid (.ers) 12. Upward Continuation (UC) Residual (Res) Filters (0 to 100 km; 12 grids) 13. Mutliscale Edge Detection Polygons (for each MGA zone; .shp) 14. Analytic Signal Phase Polygons (.shp) 15. GeoTiff Images (of all grids; .tif)