Tanami EW 5ZA - 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 5ZA - TMI RTP 1VD grid (AWAGS) is the first vertical derivative of the TMI RTP grid of the NTGS Tanami EW 5ZA 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 1547 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 5ZA 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。该数据通过标准化流程进行处理，以确保所记录的响应仅源于地下岩石。处理后得到的数据集可通过解译揭示地下地质构造。经处理的数据由GA的地球物理学家开展质量核验，以确保GA发布的最终数据满足使用需求。本次的塔纳米EW 5ZA-TMI RTP 1VD网格（AWAGS）是2018年北领地塔纳米EW 5ZA区域详细航空磁测、放射性测量与数字高程测量（NTGS Tanami EW 5ZA Region Detailed Airborne Magnetic Radiometric and Digital Elevation Survey, NT, 2018）中TMI RTP网格的一阶垂直导数。该网格的单元格尺寸为0.00018度（约20米），单位为纳特每米（nT/m）。生成该TMI网格所用的数据由北领地政府于2018年采集，总测线长度为1547公里，测线间距100米，飞行离地高度60米。该数据已完成变参化极归算（Variable Reduction to the Pole, VRTP），使磁异常中心与磁化体位置对齐。本次VRTP处理采用最高至5阶多项式的差分化极计算方法。磁倾角与磁偏角由IGRF-11地磁参考模型导出，所用数据的采集日期与飞行高度均代表本次测量的实际工况。通过对2018年北领地塔纳米EW 5ZA区域详细航空磁测、放射性测量与数字高程测量的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，即本网格数据。本网格通过INTREPID地球物理软件包中的算法计算生成。该网格可反映具有不同磁化率的地下地质体的磁响应特征，还可用于定位岩脉等构造特征。