Satellite ASTER Geoscience Map of South Australia
The ASTER geoscience map of SA is a set of public, web-accessible digital
geoscience products generated from satellite ASTER data.
ASTER stands for Advanced Spaceborne Thermal Emission and Reflection Radiometer and is a Japanese imaging instrument flying on the US TERRA satellite, launched in December 1999.
The multispectral imaging sensor is the world’s first and only “geoscience tuned” satellite Earth Observing system to date.
The WA Centre of Excellence for 3D Mineral Mapping (C3DMM), led by CSIRO, developed new methods and software that transformed the raw ASTER satellite data into a new suite of 16 mineral group maps (e.g. Figure 1).
The ASTER geoscience products of SA feature the first publically released state scale mineral maps derived from thermal infrared bands and should
help set the standard for global ASTER geoscience mapping.
ASTER has 14 spectral bands spanning wavelengths sensitive to important rock
forming minerals, including:
• Iron oxides
• Quartz, and
• “Hydrothermal” minerals such as
muscovite and chlorite.
Each ASTER image covers a 60 by 60 km area with individual pixel elements ranging from 15 to 90 m, depending on wavelength. This is suitable for geoscience mapping at scales from the continent (1:2,500,000) down to the mineral prospect (1:50,000) scale. The SA mosaic is sourced from 30000 ASTER scenes covering Australia with approximately 600 used in the final mosaic.
Figure 1: Satellite SA ASTER Geoscience map of silica abundance index (blue: low silica content; red: high silica content). Grey-scale underlay of ASTER band 2 for geographic context.
The image pre-processing methodology to generate the 16 SA ASTER geoscience map products involves correcting for complicating instrument, atmosphere and vegetation effects. The resultant ASTER geoscience maps provide new mineral information not available from other current technologies. This new mineral information is valuable for more accurate mapping of the regolith cover that blankets much of Australia and finding those often small islands of bedrock materials.
The final geoscience products represent “mineral group” information only. The reason for this is that the determination of the abundance and chemistry of specific minerals requires even higher resolution systems often termed as hyperspectral, which measures hundreds of spectral bands, such as the Australian airborne HyMap™ system (www.hyvista.com). A suite of hyperspectral satellites will be launched from 2015 (www.isiswg.org) and CSIRO is working with International satellite teams to again capture their benefit for Australia.
CSIRO has been collaborating with Japanese space agencies and NASA for twenty years in order to capture the opportunity of continental-scale mapping of land surface mineralogy over Australia using ASTER. CSIRO has also enjoyed close partnerships with government geosurveys across Australia and in the last 2-3 years been successful in securing funding through schemes such as South Australian Governments PACE 2020 initiative and WA Centres of Excellence funding (for establishing C3DMM).
Accessing the maps
The SA ASTER geoscience maps are digitally available to the
public as GIS-compatible images (e.g. TIF and JPG format) or in image-processing software format (e.g. BSQ with headers).
The TIF and JPG format data can be downloaded online from:
• CSIRO's C3DMM webpage or
• AuScope or
• DMITRE's SARIG
The State ASTER maps have been carved into 1:250,000 mapsheets with individual file sizes reduced to ~50 Mbytes each. The complete data set, including the BSQ data (~500 Gigabytes), is available from the Geological Survey of South Australia within Department of Manufacturing, Innovation, Trade, Resources and Energy (DMITRE) product sales via an external drive.
The satellite ASTER geoscience map of SA is the second instalment of an Australian ASTER geoscience map that is being developed in cooperation with the other State and Territory surveys and Geoscience Australia. A national map (Version 1) is scheduled for release at the 34 International Geological Convention in Brisbane 2012 (http://www.34igc.org). Both
are being generated through the WA Centre of Excellence for 3D Mineral Mapping. Later updates of this map may include improved removal of complicating vegetation effects and products derived from thermal infrared.