Satellite ASTER Geoscience Map of the Northern Territory
The ASTER geoscience map of NT 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 NT feature territory scale mineral maps derived from visible-near, shortwave and 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.
Figure 1: Satellite NT ASTER Geoscience maps. From left to right: 1) False Colour RGB, 2) AlOH Group composition (blue: Al-rich white mica and smectite or well ordered kaolinite; red: Al-poor white mica and smectite), 3) 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 NT ASTER geoscience map products involves correcting for complicating instrument, atmosphere and vegetation effects (please see NT ASTER geoscience product descriptions). 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 measure 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 the WA Centres of Excellence funding (for establishing C3DMM).
Accessing the maps
The NT 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
and viewed online from:
• AuScope or
• NTGS's Geophysical Image Web Server GIWS
The Territory ASTER maps have been carved into 1:1 000 000 mapsheets with individual file sizes reduced to ~200 to 900 Mbytes each. The complete data set, including the BSQ data (~500 Gigabytes), is available from the Northern Territory Geological Survey product sales via an external drive.
The satellite ASTER geoscience map of NT is the third 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.