Radiometrics Th/K Ratio Image - 2015

Ratio of Th over K derived from the filtered Th and K grids. The Radiometric Map of Australia dataset comprises gridsof potassium (K), uranium (U) and thorium (Th) element concentrations, and derivatives of these grids. This third edition was derived by seamlessly merging 45 new survey grids with the Second Edition Radiometric Map of Australia (Minty et al., 2010). Details of the specifications of individual airborne surveys can be found in the 2014 Edition of the Index of Airborne Geophysical Surveys (Percival, 2014). Matching of the grids in the database was achieved using a program called Gridmerge, originally developed within Geoscience Australia and has now been commercialised. This program was used to merge 45 new surveys to the Second Edition Radiometric Map of Australia. The second edition merged over 550 individual grids to create the compilation (Minty et al., 2009), and the Australia-wide Airborne Geophysical Survey (AWAGS) airborne radiometric data was used to control the base levels of those survey grids which overlapped the AWAGS data (Milligan et al., 2009). As the second edition was used as a base grid for the Gridmerge operation the new Third Edition is essentially levelled to AWAGS. Filtering: Potassium, uranium, thorium and dose rate grids are available in both filtered and unfiltered versions. The low-pass filtering was achieved by applying a 7-point, degree-3 Savitzky-Golay filter (Savitzky and Golay, 1964) to each of the original survey grids prior to grid merging.

基于滤波后的钍（Thorium, Th）与钾（Potassium, K）网格数据计算得到的钍钾浓度比值。澳大利亚放射测量地图数据集包含钾（Potassium, K）、铀（Uranium, U）、钍（Thorium, Th）元素浓度网格数据及其衍生网格数据。本第三版数据集通过将45份新的测量网格与2010年版《澳大利亚放射测量地图（第二版）》（Minty等，2010）进行无缝融合得到。各单项航空测量的技术规格细节可查阅《航空地球物理测量索引（2014版）》（Percival，2014）。数据库内网格的匹配工作借助名为Gridmerge的程序完成，该程序最初由澳大利亚地质调查局（Geoscience Australia）开发，目前已实现商业化。该程序被用于将45份新的测量数据融合至第二版澳大利亚放射测量地图中。第二版数据集通过融合超过550份独立网格数据编绘而成（Minty等，2009）；针对与全澳航空地球物理测量（Australia-wide Airborne Geophysical Survey, AWAGS）数据重叠的测量网格，采用全澳航空放射测量数据对其基准水平进行校准（Milligan等，2009）。由于第二版数据集被用作Gridmerge融合操作的基准网格，因此新版第三版数据集的基准水平本质上与AWAGS保持一致。滤波处理说明：钾、铀、钍及剂量率网格数据均提供滤波与非滤波两种版本。低通滤波处理通过在网格融合前，对每份原始测量网格应用7点3阶萨维茨基-戈莱滤波器（Savitzky and Golay，1964）完成。