Tanami NS 4NE - TMI RTP grid (AWAGS)

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 0.00018 degrees (approximately 20m).The data are in nanoTesla (or nT). The data used to produce this grid was acquired in 2018 by the NT Government, and consisted of 10063 line-kilometres of data at 100m line spacing and 60m terrain clearance. 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.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-11 geomagnetic reference model using a data representative date and elevation representative of the survey.

总磁场强度（Total Magnetic Intensity, TMI）数据用于测量地壳内成岩矿物成分差异引起的地球磁场强度变化。磁异常可分为正异常（磁场强于正常场）与负异常（磁场弱于正常场），其类型取决于岩石的磁化率。该数据通过标准处理流程进行处理，以确保记录的响应仅来源于地下岩石。经处理得到的数据集可用于解译地下地质构造。经处理的数据已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，确保GA发布的最终数据符合使用要求。
本磁网格的单元尺寸为0.00018度（约20米），数据单位为纳特斯拉（nanoTesla, nT）。用于生成该网格的数据由北领地政府（NT Government）于2018年采集，包含10063线公里的实测数据，测线间距为100米，地形离地高度为60米。为约束网格中的长波长分量，研究人员采用独立数据集——澳大利亚全域航空地球物理调查（Australia-wide Airborne Geophysical Survey, AWAGS）航空磁数据，对本次调查网格的基准面进行控制，本网格已基本匹配AWAGS的基准。
本数据已施加可变化极（Variable Reduction to the Pole, VRTP）处理，使磁异常中心与磁化体位置重合。VRTP处理采用最高至5阶多项式的差分化极计算方法。磁倾角与磁偏角基于IGRF-11地磁参考模型，采用与本次调查代表性日期和高程匹配的数据计算得到。