Tanami NS 1D - 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 NS 1D - TMI RTP 1VD grid (AWAGS) is the first vertical derivative of the TMI RTP grid of the NTGS Tanami NS 1D 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 2188 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 NS 1D 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）数据可用于表征由地壳中成岩矿物成分差异所引起的地球磁场强度变化。磁异常可分为正异常（磁场强度高于正常背景）与负异常（磁场强度低于正常背景），其分类依据为岩石的磁化率。该数据通过标准流程进行处理，以确保所记录的响应仅源自地下岩石。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查，以确保GA发布的最终数据满足实际应用需求。
本次发布的Tanami NS 1D - TMI RTP 1VD网格（AWAGS），为2018年北领地（NT）NTGS Tanami NS 1D区域详细航空磁测、放射性测量与数字高程测量中TMI RTP网格的一阶垂直导数。该网格的单元尺寸为0.00018度（约20米），单位为纳特每米（nT/m）。
用于生成该TMI网格的原始数据由北领地政府于2018年采集，数据覆盖总长度达2188测线公里，测线间距为100米，飞行离地高度为60米。该数据已施加可变化极（Variable Reduction to the Pole, VRTP）处理，使磁异常中心位于磁化体的正上方。可变化极（VRTP）处理采用了最高至5阶多项式的差分化极计算方法。磁倾角与磁偏角源自IGRF-11地磁参考模型，计算时采用了与本次测量代表性日期及高程相匹配的参数。
通过对2018年北领地NTGS Tanami NS 1D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，即可计算得到该一阶垂直导数网格。本次网格的计算采用了INTREPID地球物理软件包中的算法。该网格可表征具有不同磁化率的地下地质体的磁响应特征，此外还可用于识别岩脉等构造特征。