Authors / CoAuthors
Poudjom Djomani, Y. | Minty, B.R.S.
Abstract
Total magnetic intensity (TMI) data measures variations in the intensity of the Earth 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 first vertical derivative (1VD) grid is derived from the 2019 Total magnetic Intensity (TMI) grid of Australia which has a grid cell size of ~3 seconds of arc (approximately 80 m). As the vertical derivative filter is essentially a high-pass filter, longer wavelengths are suppressed, and shorter wavelengths emphasized. The magnetic units of the data are in nT per metre.
Product Type
dataset
eCat Id
132275
Contact for the resource
Custodian
Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
ACT
2601
Australia
Point of contact
Resource provider
Digital Object Identifier
Keywords
- ( Theme )
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- Vertical Derivative
- ( Theme )
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- magnetics
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- magnetism and palaeomagnetism
- ( Theme )
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- airborne digital data
- ( Theme )
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- national geophysical compilation
- ( Discipline )
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- Earth sciences
- ( Discipline )
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- geophysics
- ( Data centre )
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- NCI
- ( Place )
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- Australia
- ( Feature type )
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- grid
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- Published_External
- ( Feature type )
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- raster
- ( Service )
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- GADDS2.0
- ( Theme )
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- first vertical derivative
Publication Date
2019-11-04T00:00:00
Creation Date
Security Constraints
Legal Constraints
Status
Purpose
Maintenance Information
notPlanned
Topic Category
geoscientificInformation
Series Information
Lineage
The first vertical derivative (1VD) is derived from the 2019 Total Magnetic Intensity (TMI) grid of the Australian region. The TMI grid is the seventh edition with a cell size of ~3 seconds of arc (approximately 80 m). This grid only includes airborne-derived TMI data for onshore and near-offshore continental areas. Since the sixth edition was released in 2015, data from 234 new surveys have been added to the database, acquired mainly by the State and Territory Geological Surveys. It is estimated that 33 500 000 line-kilometres of survey data were acquired to produce the 2019 grid, about 2 000 000 line-kilometres more than for the previous edition. The 2019 magnetic grid was derived from a complete re-levelling of the national magnetic grid database. The survey grids were levelled to each other, and to the Australia Wide Airborne Geophysical Survey (AWAGS) (Milligan et al., 2009), which serves as a baseline to constrain long wavelengths in the final grid. The levelling and grid-merging procedure was described in detail in Minty et al. (2003). The first vertical derivartive (1VD) grid was produced in two steps. The TMI grid was first transformed to a Lambert Conic Conformal projection before applying a standard implementation of the vertical derivative process in the frequency domain, and then conversion back to a geodetic coordinate system. As the vertical derivative filter is essentially a high-pass filter, longer wavelengths are suppressed, and shorter wavelengths emphasized. The magnetic units of the data are in nT per metre. References Milligan, P.R., Minty, B.R.S., Richardson, M. and Franklin, R., 2009. The Australia-wide Airborne Geophysical Survey accurate continental magnetic coverage. Preview, No. 138, p. 1-128. Minty, B.R.S., Milligan, P.R., Luyendyk, A.P.J. and Mackey, T., 2003. Merging airborne magnetic surveys into continental-scale compilations. Geophysics, 68 (3), 988-995.
Parent Information
Geophysical Data Collection - magnetics
UUID - c6b58f54-102e-19e9-e044-00144fdd4fa6,
eCat ID - 74514
Extents
[-43.928981, -9.025662, 112.502532, 154.662516]
Reference System
GDA94 (EPSG:4283)
Spatial Resolution
Service Information
Associations
Source Information
The 2015 Total Magnetic Intensity (TMI) grid of the Australia region is made of a compilation of 31,500,000 line-kilometres of survey data acquired by the Commonwealth, State and Territory Governments, the mining and exploration industry, universities and research organisations.