Magnetic Anomaly Map of Australia, Seventh Edition, 2020 - Enhanced Products Package - upward continued grid UC2km4kmRes (UC2km4kmRes)

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.

总磁场强度（Total Magnetic Intensity，TMI）数据用于测量由地壳内造岩矿物成分差异引发的地球磁场强度变化。磁异常可分为正异常（磁场强度高于正常值）与负异常（磁场强度低于正常值）两类，具体取决于岩石的磁化率。数据通过标准处理流程开展预处理，确保记录的响应仅源自地下岩石；处理后得到的数据集可用于解译并揭示地下地质结构。经处理的数据需由澳大利亚地质调查局（Geoscience Australia，GA）地球物理学家开展质量核查，以确保GA发布的最终数据符合使用要求。该地磁格网的格单元尺寸为0.00083度（约88米），数据单位为纳特（nanoTesla，nT）。据估算，为生成2019年国家地磁格网，澳大利亚州及领地地质调查机构与澳大利亚地质调查局（Geoscience Australia，GA）共采集了3350万测线公里的调查数据。该数据已应用变极化（Variable Reduction to the Pole，VRTP）处理，使磁异常中心对准磁化体；该变极化处理基于五阶多项式的差分极化计算实现。磁倾角与磁偏角源自国际地磁参考场15（IGRF-15），计算时采用了与调查匹配的代表日期与高程数据。向上延拓操作可对磁数据进行处理，以增强深部大型源磁异常并削弱浅部异常。为约束格网中的长波长分量，研究采用独立数据集——全澳航空地球物理调查（Airborne Geophysical Survey，AWAGS）航空磁数据——来控制调查格网的基准面，该调查格网基本已与AWAGS数据完成平差校准。