Total Magnetic Intensity greyscale image - 2015

The Total Magnetic Intensity (greyscale) image is created from a composite TMI grid of the Australian region with a grid cell spacing of ~3 seconds of arc (approximately 80 m). This image only includes airborne-derived TMI data for onshore and near-offshore continental areas. Since the fifth edition was released in 2010 data from 41 new surveys have been added to the database, acquired mainly by the State and Territory Geological Surveys. It is estimated that 31 500 000 line-kilometres of survey data were acquired to produce the grid data, 4 500 000 line-kilometres more than for the previous edition. Details of the specifications of individual airborne surveys can be found in the Fourteenth Edition of the Index of Airborne Geophysical Surveys (Percival, 2014). Matching of the grids in the database was achieved using a program called Gridmerge, which was originally developed within Geoscience Australia and has now been commercialised. This program was used to merge 41 new surveys to the 5th Edition Total Magnetic Intensity Anomaly Grid of Australia (Milligan et al., 2010). The 5th Edition merged 795 individual grids to create the compilation and to constrain long wavelengths, an independent data set, the Australia-wide Airborne Geophysical Survey (AWAGS) airborne magnetic data, was used to control the base levels of those survey grids which overlapped the AWAGS data (Milligan et al., 2009). As the 5th Edition was used as a base grid for the Gridmerge operation the new 6th Edition is essentially levelled to AWAGS. Individual and merged grids may be downloaded from the Geophysical Archive Data Delivery System (GADDS) on the Australian Government's Geoscience Portal at http://www.geoscience.gov.au/gadds. References: Milligan, P.R., Minty, B.R.S., Richardson, M. and Franklin, R., 2009. The Australia-wide Airborne Geophysical Survey - accurate continental magnetic coverage. Preview, 138, 70. Milligan, P.R., Franklin, R., Minty, B.R.S., Richardson, L.M. and Percival, P.J., 2010. Magnetic Anomaly Map of Australia (Fifth Edition), 1:5 000 000 scale, Geoscience Australia, Canberra. Percival, P.J., 2014. Index of airborne geophysical surveys (Fourteenth Edition). Geoscience Australia Record 2014/014.

总磁场强度（Total Magnetic Intensity, TMI）灰度图像由澳大利亚区域的合成TMI网格生成，网格单元间距约3角秒（约80米）。该图像仅包含陆域及近岸大陆区域的航空探测TMI数据。

自2010年第五版发布以来，数据库新增了41项新勘测数据，这些数据主要由各州及领地地质调查局采集。据估算，本次网格数据的生成共采集了3150万测线公里的勘测数据，较前一版本增加了450万测线公里。

各项航空勘测的技术规格细节可查阅《航空地球物理勘测索引（第十四版）》（Percival, 2014）。数据库内的网格匹配工作通过一款名为Gridmerge的程序完成，该程序最初由澳大利亚地球科学局（Geoscience Australia）开发，现已实现商业化。该程序将41项新勘测数据整合至第五版澳大利亚总磁场强度异常网格（Total Magnetic Intensity Anomaly Grid）（Milligan等，2010）。

第五版整合了795个独立网格以完成数据集编制；为约束长波长分量，研究人员采用了独立数据集——全澳航空地球物理勘测（Australia-wide Airborne Geophysical Survey, AWAGS）航空磁数据，对与AWAGS数据重叠的勘测网格的基准水平进行校正（Milligan等，2009）。由于第五版被用作Gridmerge操作的基础网格，新版第六版实质上已针对AWAGS完成了水平基准校正。

用户可从澳大利亚政府地球科学门户网站的地球物理存档数据交付系统（Geophysical Archive Data Delivery System, GADDS）下载独立网格及整合网格，访问地址为http://www.geoscience.gov.au/gadds。

参考文献：
1. Milligan P.R., Minty B.R.S., Richardson M., Franklin R. 2009. 全澳航空地球物理勘测——精准的大陆磁覆盖范围. 《Preview》, 138: 70.
2. Milligan P.R., Franklin R., Minty B.R.S., Richardson L.M., Percival P.J. 2010. 《澳大利亚磁场异常地图（第五版）》（比例尺1:5000000），堪培拉：澳大利亚地球科学局。
3. Percival P.J. 2014. 《航空地球物理勘测索引（第十四版）》，澳大利亚地球科学局报告2014/014。