Abstract

The file magmap_V5_2010 is a composite TMI grid of the Australian region with a grid cell spacing of ~3 seconds of arc (approximately 80 m). This grid only includes airborne-derived TMI data for onshore and near-offshore continental areas. Data used to compile this grid form the basis for the concurrent release of a new fifth edition of the Magnetic Anomaly Map of Australia. This edition is underpinned by the concept of a database of matched TMI grids, from which any map at any resolution can be extracted. Details of the specifications of individual airborne surveys can be found in the Eleventh Edition of the Index of Airborne Geophysical Surveys (Percival, 2010), which is included with the grid as a PDF document called magmap_V5_2010.pdf. This Index is also available online at http://www.ga.gov.au/minerals/research/methodology/geophysics/acquisition.jsp#reports. Further up to date information about individual surveys can also be obtained online from the Airborne Surveys Database at http://www.ga.gov.au/oracle/argus/. The grid results from a completely new compilation of TMI grid data, an updated method of matching the individual survey grids, and use of independent data to constrain long wavelengths. 795 individual grids have been matched and merged into the composite grids supplied here. The resolution of each grid is optimal for the specifications of the source survey line data (Briggs, 1974). Since the fourth edition was released in 2004 data from many new surveys have been added to the database, acquired mainly by the State and Territory Geological Surveys. It is estimated that 27 000 000 line-kilometres of survey data were acquired to produce the grid data, 8 000 000 line-kilometres more than for the previous edition. The index map (Figure 1) shows the distribution of original survey line spacings from which the grids are derived, Figure 2 shows the distribution of all survey line spacings, and Figure 3 shows the survey ownerships. Matching of the grids in the database was achieved using a program called Gridmerge, which was originally developed within Geoscience Australia and has now been commercialised. It uses statistics of the overlap regions between adjacent surveys to globally minimise the differences in the base levels of all surveys (Minty et al., 2003). There is also provision to remove higher-order surfaces from grids. To constrain long wavelengths, an independent data set, the Australia-wide Airborne Geophysical Survey (AWAGS) airborne magnetic data, was used to control the base levels of those survey grids which overlapped the AWAGS data (Milligan et al., 2009). The high-frequency differences between the grids were smoothed using a convolution operator. Very long wavelengths greater than 1000 km have been constrained by using the MF6 data derived from the CHAMP satellite (Maus et al., 2007). Grid downloads: The Magnetic Map of Australia grid can be downloaded using the Geophysical Archive Data Delivery System (GADDS) on the Australian Government's Geoscience Portal at http://www.geoscience.gov.au/bin/mapserv36?map=/public/http/www/geoportal/gadds/gadds.map File size: At full resolution, the Magnetic Map of Australia grid has 41876 rows and 50592 columns and has a file size of approximately 8.3 Gb in ERMapper format. Note that, because of GADDS file size limits, it is not possible for clients to download very large areas of the grid at full resolution. Clients wishing to do so should contact Geoscience Australia to make special arrangements to have the complete grid dataset provided on a user-supplied portable hard drive.
Google map showing geographic bounding box with values North bound -9.0 East bound 155.0 West bound 112.0 South bound -44.0
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Related Links
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For information on acquiring this product,
please contact the Geoscience Australia Sales Centre via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).

Please note that support hours are 9 am to 5 pm weekdays

Product Type/Sub Type

dataset - Geophysical Map - TMI pixel

Constraints

license
Creative Commons Attribution 3.0 Australia Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

2010

Product Type

dataset

Topic Category

geoscientificInformation

Keywords

Geophysical Map
TMI pixel
pixel images
geophysics
TMI
Geophysics

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-9.0
East bound
155.0
West bound
112.0
South bound
-44.0

Lineage

Unknown

Digital Transfer Options

onLine+hardcopy

DISTRIBUTION Format

pdf
misc
ers

Distributor

Role
distributor
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address

Metadata File Identifier

a05f7892-f6ef-7506-e044-00144fdd4fa6

Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

2010-03-31

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

Role
pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Downloads
Related Links
Web Services
For information on acquiring this product,
please contact the Geoscience Australia Sales Centre via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).

Please note that support hours are 9 am to 5 pm weekdays