Mapping the upper South Alligator River valley using integrated datasets
Internal Report 444
Pfitzner K & Martin P
Supervising Scientist Division
Department of the Environment, Water, Heritage and the Arts
About the report
High resolution airborne gamma and MASTER imagery were collected over the upper South Alligator River valley, Kakadu National Park, in order to assess the state of abandoned uranium mine and mill sites and to detail the wider landscape of the valley. The area is a complex landscape in terms of differences in physiography: elevation; outcropping lithology; structure; water bodies and vegetation type. The investigation utilised high resolution 50m line spaced airborne gamma survey (AGS) data and VIS-SWIR-TIR regions of 10m MASTER coverage. The eU, eTh, and K airborne gamma channels were described as single bands and ratios, and enhanced by a high resolution DEM captured during the survey. MASTER data was calibrated to apparent reflectance, and endmembers selected from field spectra, image data and through spectral and spatial compressing using the Minimum Noise Fraction, Pixel Purity Index and n-Dimensional Visualiser in ENVI® software. DEM integration was used to enhance the MASTER information. Data fusion of the AGS data with MASTER imagery increased the usefulness of the AGS data, which highlighted the abandoned mine sites and, combined with ground-based spectrometry, was used to define the areas of potential radiological risk within the valley. Collection and analysis of tight line spaced AGS data is recommended for identifying radiologically contaminated areas on and near abandoned mine sites, and for targeting ground-based investigations. Integrating a higher spatial and spectral dataset such as MASTER enhances the usefulness of the AGS for mine site assessment. In the present case the derived images, combined with available geological data and ground truthing, detailed the wider landform features and provided a cost-effective method for assessing the state of abandoned mine sites.