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Seabed gravel content across the Australian continental EEZ 2011

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: ANZCW0703014835

Title: Seabed gravel content across the Australian continental EEZ 2011


Custodian: Geoscience Australia

Jurisdiction: Australia



The dataset provides the spatially continuous data of the seabed gravel content (sediment fraction >2000 ?m) expressed as a weight percentage ranging from 0 to 100%, presented in 0.01 decimal degree resolution raster format.

The dataset covers the Australian continental EEZ, including seabed surrounding Tasmania. It does not include areas surrounding Macquarie Island, and the Australian Territories of Norfolk Island, Christmas Island, and Cocos (Keeling) Islands or Australia's marine jurisdiction off of the Territory of Heard and McDonald Islands and the Australian Antarctic Territory.

This dataset supersedes previous predictions of sediment gravel content for the Australian Margin with demonstrated improvements in accuracy. Accuracy of predictions varies based on density of underlying data and level of seabed complexity. Artefacts occur in this dataset as a result of insufficient samples in relevant regions. This dataset is intended for use at national and regional scales. The dataset may not be appropriate for use at local scales in areas where sample density is insufficient to detect local variation in sediment properties. To obtain the most accurate interpretation of sediment distribution in these areas, it is recommended that additional samples be collected and interpolations updated.

ANZLIC search words:

  • MARINE Geology and Geophysics

Spatial domain:

locality map

Geographic extent name: AUSTRALIAN EEZ - AUSTRALIAN EEZ - Ocean and Sea Regions - Australia

Geographic extent polygon: 109.2334 -8.8882, 163.1934 -8.8882, 163.1934 -47.1982, 109.2334 -47.1982, 109.2334 -8.8882,

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

Geographic bounding box:
North bounding latitude: -8.8882 °
South bounding latitude: -47.1982 °
East bounding longitude: 163.1934 °
West bounding longitude: 109.2334 °

Data currency

Beginning date: Not Known

Ending date: 2011-05-20

Dataset status

Progress: Not Known

Maintenance and update frequency: Not Known


Stored data format:
DIGITAL - ArcGIS-grid ArcInfo grid WGS84
DIGITAL - ESRI ascii ESRI ascii grid ArcGIS WGS84
Available format type:
DIGITAL - ESRI ascii ESRI ascii grid ArcGIS WGS84
DIGITAL - ArcGIS-grid ArcInfo grid WGS84

Access constraints:

No restrictions

Free Data Download

Data quality


Sediment samples were exported from Geoscience Australia?s Marine Sediments database (MARS), an Oracle database developed by Geoscience Australia in line with ANZLIC data standards. A subset of this data was selected for use in predicting spatial distribution of gravel content based on a set of criteria (similar to those reported by Li et al. 2010 and detailed GA record will be available in 2012). Predicting the spatial distribution of gravel content at a 0.01 decimal degree resolution was undertaken by averaging the predictions of random forest, of a combined method of random forest and ordinary kriging and of a combined method of random forest and inverse distance squared (the methods used is similar to that reported by Li et al. 2011 and detailed GA record will be available in 2012). The spatial interpolation method used was experimentally selected from over 40 methods/sub-methods based on assessment of predictive errors. The predictions were then imported to ArcGIS, and ArcGRID and ascii raster files were generated. Final raster files are in Geographic WGS 84 coordinate system with a 0.01 dd spatial resolution. File sizes are approximately is 79 MB (ArcGRID) and 135 MB (ascii) with dimension of 5396 x 3831 cells.

Positional accuracy:

Sediment samples used in the interpolation incorporate data from various surveys since 1899 by a range of organizations. Modern surveys which used GPS have a positional accuracy of 5-30 m, while earlier surveys which had positions probably accurate to 50-2000 m depending upon the water depth and strength of currents. Only samples with positional information recorded to 0.01 dd accuracy were used in the spatial interpolation.

Attribute accuracy:


Logical Consistency:

Point data at each grid cell was checked to ensure that the sum of gravel, mud and sand content was 100%. Interpolated grids were further checked by visual comparison with maps initially produced in R to ensure no errors introduced during the process of producing the grid file.


This dataset is complete

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:

Metadata information

Metadata date: 2013-03-08

Additional metadata

Metadata reference XHTML:

Metadata reference XML:


Authors:Li, J. Heap, A.D. Potter, A. Huang, Z.