Cobar P5009 EXT 4 reduced to pole fft 1st vertical derivative grid  


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 4 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

146879

Contact for the resource

  Point of contact

Commonwealth of Australia (Geoscience Australia)  
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
  • EARTH SCIENCES
( Data centre )
  • NCI
( Discipline )
  • Earth sciences
( Discipline )
  • geophysics
( Feature type )
  • grid
( Place )
  • Australia
( Place )
  • NSW
( Project )
  • survey 5009
( Theme )
  • GADDS2.0
( Theme )
  • TMI
( Theme )
  • magnetics
( Theme )
  • magnetism
( Theme )
  • palaeomagnetism
( Theme )
  • airborne digital data
( Theme )
  • geophysical survey
( Theme )
  • mag
( Theme )
  • total magnetic intensity
( Theme )
  • reduced to the pole
( Theme )
  • RTP
( Theme )
  • first vertical derivative
( Theme )
  • 1VD
( Theme )
  • grid
( Theme )
  • greyscale
( Theme )
  • image
  • Published_External

Publication Date

2022-07-12T01:17:32

Creation Date

2022-06-21T00:00:00

Security Constraints

Australian Government Security ClassificationSystem    

Classification - unclassified

Legal Constraints

Creative Commons Attribution 4.0 International Licence    

Access - license

Use - license

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 4 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 4 reduced to pole fft 1st vertical derivative grid NCSS    

Association Type - operatedOnBy

Cobar P5009 EXT 4 reduced to pole fft 1st vertical derivative grid OPeNDAP    

Association Type - operatedOnBy

Cobar P5009 EXT 4 reduced to pole fft 1st vertical derivative grid WMS    

Association Type - operatedOnBy

Cobar P5009 EXT 4 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 4 reduced to pole fft 1st vertical derivative grid file download  

Cobar P5009 EXT 4 reduced to pole fft 1st vertical derivative grid NCSS  

Cobar P5009 EXT 4 reduced to pole fft 1st vertical derivative grid OPeNDAP  

Cobar P5009 EXT 4 reduced to pole fft 1st vertical derivative grid WMS  

Cobar P5009 EXT 4 reduced to pole fft 1st vertical derivative grid WCS  

Source Information

This Cobar P5009 EXT 4 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