Total Magnetic Intensity Grid of Australia with Variable Reduction to Pole (VRTP) 2019 - seventh edition

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. A variable reduction to Pole is aimed at locating magnetic anomalies exactly above their source bodies and without any distortion. The 2019 Total magnetic Intensity (TMI) grid of Australia with variable reduction to pole (VRTP) has a grid cell size of ~3 seconds of arc (approximately 80 m). This grid only includes airborne-derived TMI data for onshore and near-offshore continental areas. The VRTP processing followed a differential reduction to pole calculation up to 5th order polynomial. Magnetic inclination and declination were derived from the IGRF-11 geomagnetic reference model using a data representative date of January 2005 and elevation 300 m.总磁场强度（Total magnetic intensity, TMI）数据用于测量地壳内造岩矿物成分差异所引发的地球磁场强度变化。磁异常可分为正异常（磁场强度高于正常值）与负异常（磁场强度低于正常值），具体取决于岩石的磁化率。变参化极（Variable Reduction to Pole, VRTP）旨在将磁异常精准定位在其源体正上方且无任何畸变。2019年澳大利亚变参化极总磁场强度网格的网格单元尺寸约为3角秒（近似80米）。该网格仅涵盖陆域及近岸大陆区域的航空探测总磁场强度数据。变参化极处理采用了最高至五阶多项式的差分化极计算方法。磁场倾角与偏角取自国际地磁参考场11（International Geomagnetic Reference Field-11, IGRF-11）模型，所用数据的代表日期为2005年1月，参考高程为300米。