Magnetic Anomaly Map of Australia, Seventh Edition, 2020 - Enhanced Products Package - upward continued grid UC24km30kmRes (UC24km30kmRes)

Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's 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. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose.This magnetic grid has a cell size of 0.00083 degrees (approximately 88m).The data are in nanoTesla (or nT). It is estimated that 33 500 000 line-kilometres of survey data collected by State and Territory geological surveys and Geoscience Australia were acquired to produce the 2019 national magnetic grid. The data has had a variable reduction to the pole applied to centre the magnetic anomaly over the magnetised body. The VRTP processing followed a differential reduction to pole calculation up to 5th order polynomial. Magnetic inclination and declination were derived from the IGRF-15 geomagnetic reference model using a data representative date and elevation representative of the survey. The upward continuation manipulates the magnetic data to enhance the large deep source anomalies and minimises shallow anomalies. To constrain long wavelengths in the grid, an independent data set, the Australia-wide Airborne Geophysical Survey (AWAGS) airborne magnetic data, was used to control the base levels of the survey grid. This survey grid is essentially levelled to AWAGS.

总磁强度（Total Magnetic Intensity, TMI）数据用于衡量由地壳中成岩矿物成分差异所引发的地球磁场强度变化。根据岩石的磁化率差异，磁异常（magnetic anomalies）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）两类。该数据集通过标准流程进行预处理，以确保所记录的磁场响应仅源自地下岩石。经处理后得到的数据集可用于解译，以揭示地下地质构造。经处理的数据会由澳大利亚地质调查局（Geoscience Australia, GA）的地球物理学家开展质量核查，以确保GA发布的最终数据集符合使用要求。该磁网格的单元尺寸为0.00083度（约88米），数据单位为纳特斯拉（nanoTesla, nT）。据统计，为制作2019年全国磁网格，澳大利亚各州及领地地质调查机构与澳大利亚地质调查局（Geoscience Australia）共收集了3350万测线公里的勘探数据。该数据集已施加变极化归算（Variable Reduction to the Pole, VRTP），使磁异常中心与磁化体的空间位置对齐；此次VRTP处理采用了最高至5阶多项式的差分极化归算算法。磁倾角与磁偏角源自IGRF-15国际地磁参考场模型（International Geomagnetic Reference Field-15, IGRF-15），所用数据的代表日期与高程均匹配该次勘探的实际情况。向上延拓处理可对磁数据进行校正，以增强深部大型源磁异常并压制浅部异常。为约束网格中的长波长分量，项目采用了独立数据集——全澳航空地球物理勘探（Australia-wide Airborne Geophysical Survey, AWAGS）航空磁数据——来校准勘探网格的基准面。该勘探网格最终基本匹配AWAGS基准。