Tanami EW 5N - TMI RTP 1VD 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 Tanami EW 5N - TMI RTP 1VD grid (AWAGS) is the first vertical derivative of the TMI RTP grid of the NTGS Tanami EW 5N Region Detailed Airborne Magnetic Radiometric and Digital Elevation Survey, NT, 2018 survey.This grid has a cell size of 0.00018 degrees (approximately 20m) , and given in units of nT per metre (nT/m). The data used to produce the TMI grid was acquired in 2018 by the NT Government, and consisted of 11735 line-kilometres of data at 100m line spacing and 60m terrain clearance. 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. A first vertical derivative was calculated by applying a fast Fourier transform (FFT) process to the TMI RTP grid of the NTGS Tanami EW 5N Region Detailed Airborne Magnetic Radiometric and Digital Elevation Survey, NT, 2018 survey to produce this grid. This grid was calculated using an algorithm from the INTREPID Geophysics software package. This grid shows the magnetic response of subsurface features with contrasting magnetic susceptibilities. The grid can also be used to locate structural features such as dykes.

总磁场强度（Total Magnetic Intensity, TMI）数据用于测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。该数据通过标准流程进行处理，以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，以揭示地下地质结构。经处理的数据由GA地球物理学家进行质量检查，以确保GA发布的最终数据符合使用要求。
本次的塔纳米EW 5N - TMI RTP 1VD网格（AWAGS），是2018年北领地地质调查局（Northern Territory Geological Survey, NTGS）塔纳米EW 5N区域详细航空磁测、放射性测量与数字高程测量项目的TMI RTP网格的一阶垂直导数。该网格的单元格大小为0.00018度（约20米），单位为纳特每米（nT/m）。
用于生成该TMI网格的数据由北领地政府于2018年采集，总测线长度达11735线千米，测线间距为100米，地形离地高度为60米。该数据已应用可变极化归算处理，使磁异常中心对准磁化体上方。该可变极化归算（VRTP）处理采用差分极化归算方法，最高可至五阶多项式。磁场倾角与偏角源自IGRF-11地磁参考模型，所用数据代表年份与高程均匹配本次测量。
通过对2018年北领地NTGS塔纳米EW 5N区域详细航空磁测、放射性测量与数字高程测量项目的TMI RTP网格应用快速傅里叶变换（fast Fourier transform, FFT）算法，计算得到其一阶垂直导数，即本网格。本网格的计算采用了INTREPID地球物理软件包中的算法。该网格可展现具有不同磁化率的地下地质体的磁响应特征。此外，该网格还可用于识别岩脉等构造特征。