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Cobar P5009 EXT 5 reduced to pole fft 1st vertical derivative grid

Created 17/10/2025

Updated 17/10/2025

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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 Cobar P5009 EXT 5 reduced to pole fft 1st vertical derivative grid is the first vertical derivative of the TMI RTP grid of the Cobar Magnetic and Radiometric Survey, 2021 survey. This grid has a cell size of 0.00039074 degrees (approximately 40m) , and given in units of nT per metre (nT/m). The data used to produce the TMI grid was acquired in 2021 by the NSW Government, and consisted of 53617 line-kilometres of data at 200m line spacing and 60m terrain clearance. The data has had a variable reduction to the pole applied to centre the magnetic anomaly over the magnetised body. The VRTP processing followed a differential reduction to pole calculation up to 5th order polynomial. Magnetic inclination and declination were derived from the IGRF-11 geomagnetic reference model using a data representative date and elevation representative of the survey. A first vertical derivative was calculated by applying a fast Fourier transform (FFT) process to the TMI RTP grid of the Cobar Magnetic and Radiometric Survey, 2021 survey to produce this grid. This grid was calculated using an algorithm from the INTREPID Geophysics software package. This grid shows the magnetic response of subsurface features with contrasting magnetic susceptibilities. The grid can also be used to locate structural features such as dykes.

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Additional Info

Field Value
Title Cobar P5009 EXT 5 reduced to pole fft 1st vertical derivative grid
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/0fccb99c-4b9e-4c27-ad6b-8cac49d73d89
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 08/06/2021 - 10/08/2021
Geospatial Coverage
Map data © OpenStreetMap contributors
{
  "coordinates": [
    [
      [
        145.1,
        -33.1
      ],
      [
        147.1,
        -33.1
      ],
      [
        147.1,
        -31.1
      ],
      [
        145.1,
        -31.1
      ],
      [
        145.1,
        -33.1
      ]
    ]
  ],
  "type": "Polygon"
}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Cobar P5009 EXT 5 reduced to pole fft 1st vertical derivative grid". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/cobar-p5009-ext-5-reduced-to-pole-fft-1st-vertical-derivative-grid