Total Magnetic Intensity (TMI) Grid of Australia 2019 - seventh edition - 40 m cell size

Total magnetic intensity (TMI) data measures variations in the intensity of the Earth magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock.This grid only includes airborne-derived TMI data for onshore and near-offshore continental areas. The grid has a cell size of approximately 40 m. This spatial resolution will enable 200 m line spacing surveys incorporated into the grid to be viewed at their optimum grid resolution.Since the sixth edition was released in 2015, data from 234 new surveys have been added to the database, acquired mainly by the State and Territory Geological Surveys. The new grid was derived from a re-levelling of the national magnetic grid database. The survey grids were levelled to each other, and to the Australia Wide Airborne Geophysical Survey (AWAGS), which serves as a baseline to constrain long wavelengths in the final grid. It is estimated that 33 500 000 line-kilometres of survey data were acquired to produce the 2019 grid, about 2 000 000 line-kilometres more than for the previous edition.

总磁强度（Total Magnetic Intensity, TMI）数据用于衡量由地壳中成岩矿物含量差异引发的地球磁场强度变化。磁异常可分为正异常（磁场强度高于正常水平）与负异常（磁场强度低于正常水平），具体取决于岩石的磁化率。本网格仅涵盖陆上及近岸大陆区域的航空探测总磁强度数据。该网格的单元格尺寸约为40米，此空间分辨率可使纳入网格的200米线距探测数据以最优网格分辨率呈现。自2015年第六版发布以来，数据库新增了234项新探测任务的数据，这些数据主要由各州及领地地质调查局采集。新版网格基于国家磁网格数据库的重新平差处理生成。各探测网格之间以及与全澳航空地球物理探测（Australia Wide Airborne Geophysical Survey, AWAGS）均进行了平差处理，后者作为基线用于约束最终网格中的长波长信号。据估算，为生成2019版网格共采集了3350万线公里的探测数据，较上一版本多出约200万线公里。