Authors / CoAuthors
Abstract
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 3 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.
Product Type
dataset
eCat Id
146870
Contact for the resource
Point of contact
Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
ACT
2601
Australia
Point of contact
Resource provider
Keywords
- theme.ANZRC Fields of Research.rdf
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- EARTH SCIENCES
- ( Data centre )
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- NCI
- ( Discipline )
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- Earth sciences
- ( Discipline )
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- geophysics
- ( Feature type )
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- grid
- ( Place )
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- Australia
- ( Place )
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- NSW
- ( Project )
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- survey 5009
- ( Theme )
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- GADDS2.0
- ( Theme )
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- TMI
- ( Theme )
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- magnetics
- ( Theme )
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- magnetism
- ( Theme )
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- palaeomagnetism
- ( Theme )
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- airborne digital data
- ( Theme )
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- geophysical survey
- ( Theme )
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- mag
- ( Theme )
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- total magnetic intensity
- ( Theme )
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- reduced to the pole
- ( Theme )
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- RTP
- ( Theme )
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- first vertical derivative
- ( Theme )
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- 1VD
- ( Theme )
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- grid
- ( Theme )
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- greyscale
- ( Theme )
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- image
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- Published_External
Publication Date
2022-07-12T01:17:29
Creation Date
2022-06-21T00:00:00
Security Constraints
Legal Constraints
Status
completed
Purpose
This data set forms part of the NSW and national airborne magnetic and radiometric mosaic that is continually updated with higher resolution datasets. When integrated with other geological, geochemical, geophysical or technical datasets, it provides pre-competitive insight into the mineral, groundwater, energy, soil and other resource potential of the continental land mass. Subject to the quality control, equipment tolerances and inherent limitations on the measurements themselves, it may also be employed for other geophysical and scientific investigations into the earth.
Maintenance Information
notPlanned
Topic Category
geoscientificInformation
Series Information
Lineage
This Cobar P5009 EXT 3 reduced to pole fft 1st vertical derivative grid is the first vertical derivative grid of an airborne-derived Total Magnetic Intensity (TMI) Reduced to the Pole (RTP) grid for the Cobar Magnetic and Radiometric Survey, 2021 survey. The survey was acquired under the project No. 5009 for the geological survey of NSW. A total of 53617 line-kilometres of data at a line spacing of 200m were acquired to produce the TMI grid. 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. The image shows the magnetic response of subsurface features with contrasting magnetic susceptibilities. The image can also be used to locate structural features such as dykes. 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. References Percival, P.J., 2014. Index of airborne geophysical surveys (Fourteenth Edition). Intrepid Geophysics http://intrepid-geophysics.com
Parent Information
Geophysical Data Collection - Airborne Geophysics
UUID - ddeb0fc4-32e3-4913-80f2-f4249b17a925,
eCat ID - 111301
Extents
[-33.1, -31.1, 145.1, 147.1]
Reference System
GDA94 (EPSG:4283)
Spatial Resolution
Service Information
Associations
Association Type - operatedOnBy
Cobar P5009 EXT 3 reduced to pole fft 1st vertical derivative grid NCSS
Association Type - operatedOnBy
Cobar P5009 EXT 3 reduced to pole fft 1st vertical derivative grid OPeNDAP
Association Type - operatedOnBy
Cobar P5009 EXT 3 reduced to pole fft 1st vertical derivative grid WMS
Association Type - operatedOnBy
Cobar P5009 EXT 3 reduced to pole fft 1st vertical derivative grid WCS
Downloads and Links
File available for download in various formats from the GADDS2 portal
Cobar P5009 EXT 3 reduced to pole fft 1st vertical derivative grid file download
Cobar P5009 EXT 3 reduced to pole fft 1st vertical derivative grid NCSS
Cobar P5009 EXT 3 reduced to pole fft 1st vertical derivative grid OPeNDAP
Cobar P5009 EXT 3 reduced to pole fft 1st vertical derivative grid WMS
Cobar P5009 EXT 3 reduced to pole fft 1st vertical derivative grid WCS
Source Information
This Cobar P5009 EXT 3 reduced to pole fft 1st vertical derivative grid is the first vertical derivative grid of an airborne-derived TMI RTP data for the Cobar Magnetic and Radiometric Survey, 2021 survey acquired for the geological survey of NSW