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Gravity Anomaly Image of the Australian Region - 2008

Note: This metadata describes the dataset in accordance with the ANZLIC (Australia New Zealand Land Information Council) Core Metadata Guidelines Version 2.


Dataset citation

ANZLIC unique identifier: ANZCW0703012115

Title: Gravity Anomaly Image of the Australian Region - 2008


Custodian

Custodian: Geoscience Australia

Jurisdiction: Australia


Description

Abstract:

These images are derived from the "Gravity Anomaly Grid of the Australian Region" (GEOMET record:12115 ). The grid combines accurate onshore gravity measurements with satellite data used in offshore areas. The cell values represent simple Bouguer anomalies at a density of 2.67 tonnes per cubic metre onshore and free-air anomalies offshore. The grid cell size is 0.5 minutes of arc, which is equivalent to about 800 metres.

ANZLIC search words:

  • GEOSCIENCES Geophysics Maps

Spatial domain:

locality map

Geographic extent name: AUSTRALIA EXCLUDING EXTERNAL TERRITORIES - AUS - Australia - Australia

Geographic extent polygon: 100 -8, 170 -8, 170 -52, 100 -52, 100 -8,

Note: The format for each Geographic extent name is: Name - Identifier - Category - Jurisdiction (as appropriate) See GEN Register

Geographic bounding box:
North bounding latitude: -8 °
South bounding latitude: -52 °
East bounding longitude: 170 °
West bounding longitude: 100 °

Data currency

Beginning date: 1950-01-01

Ending date: 2008-05-01


Dataset status

Progress: Complete

Maintenance and update frequency: Not Known


Access

Stored data format:
DIGITAL - RDBMS ORACLE database ORACLE Lambert Conformal Conic GDA94
Available format type:
DIGITAL - bil Band interleaved by line (BIL) image GDA94
DIGITAL - ers ER Mapper raster dataset ER Mapper GDA94

Access constraints:

Please Note: These grids and images may be used internally in Geoscience Australia for research/interpretation purposes, but should not be distributed outside the Organisation.

External clients can access the grid using the GADDS online facility.

Free Data Download

Data quality

Lineage:

The gravity grid was derived from the complete onshore database as at May 2008 and marine gravity derived from satellite altimetry. A two-pass process was used to generate the grid from a composite file containing 1.4 Million land observations, 10.5 Million satellite values. For the satellite values refer to Sandwell, D.T. and W.H.F.Smith, Marine Gravity Anomaly from Geosat and ERS-1 Altimetry, J. Geophys. Research, 1997. The 0.5 minute grid is the finest mesh that is currently meaningful over the whole continent given that much of the data coverage is spaced at 4 or 11 km.

The parameters of the grid are:

Grid spacing: 0.5 minute = 0.0083333 degree (approx. 800 m)

Projection: Rectangular in latitude and longitude

Grid size: 8401 points longitude x 5276 points latitude

Grid origin: 7 degrees 58.55 min south, 99 deg 57.35 min east (1,1)

Scaling: Nil. Values are in decimal units (µms-² (micro metres per second squared))

Null value: -99999.0

Data accuracy: 5 units, maximum error 100 units onshore

Data precision: 1 unit

Gravity Datum:

The gravity data as supplied are based on the AAGD07 datum. The gravity unit used is micrometres per second squared which is equivalent to 0.1 milligals.

A filtered image was also created using a high-pass filter with a cutoff wavelength of 500 km.

Images have a sunangle with illumination from the north east.

Positional accuracy:

Pixel size : 0.0083333 degrees (approx 800m)

Highly variable depending on the age of the individual surveys that comprise this data set. Prior to 1995 (approximately), data were collected using various techniques such as manually scaling from base maps (100's m error), digitising from base maps derived from air photo station plots (100's m error), and using optical surveying methods (metre accuracy). More recent surveys were acquired using differential GPS with sub metre accuracy.

Vertical accuracy is highly variable too, depending on the age of the survey. Prior to the use of differential GPS

station heights were determined by picking off from a topographic map (10's metre error), using barometric techniques (metre errors) and optical surveying techniques (sub metre accuracy). Differential GPS gives centimetre accuracy.

Attribute accuracy:

Highly variable depending on the age of the individual surveys that comprise this dataset. Modern surveys using LaCoste and Romberg or Scintrex gravity meters have an accuracy of 0.01 micro metres per second squared. Earlier surveys using older style quartz spring meters have a lower accuracy ~ 1.0 micro metres per second squared.

Logical Consistency:

A geoscientist visually inspected the finished dataset to make sure the data were accurate and consistent with current scientific information.

Completeness:

Complete for the coverage of continental Australia and Australia's continental margins.


Contact information

Contact organisation: Commonwealth of Australia (Geoscience Australia) (GA)
Contact position: Manager Client Services
Mail address: Cnr Jerrabomberra Ave and Hindmarsh Dr
Mail address: GPO Box 378
Locality: Canberra
State: ACT
Country: Australia
Postcode: 2601
Telephone: 02 6249 9966
Facsimile: 02 6249 9960
Electronic mail address: sales@ga.gov.au

Metadata information

Metadata date: 2013-03-08


Additional metadata

Metadata reference XHTML: http://www.ga.gov.au/meta/ANZCW0703012115.html

Metadata reference XML: http://www.ga.gov.au/meta/ANZCW0703012115.xml

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Authors:Bacchin, M.
SPATIAL INFORMATION FOR THE NATION