Childara - 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 Childara - TMI RTP 1VD grid (AWAGS) is the first vertical derivative of the TMI RTP grid of the Childara Airborne Magnetic Radiometric and DEM Survey, SA, 2017 survey.This grid has a cell size of 0.0004 degrees (approximately 41m) , and given in units of nT per metre (nT/m). The data used to produce the TMI grid was acquired in 2017 by the SA Government, and consisted of 135047 line-kilometres of data at 200m 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 Childara Airborne Magnetic Radiometric and DEM Survey, SA, 2017 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（磁场强度高于正常背景场）与负异常（磁场强度低于正常背景场），具体取决于岩石的磁化率。该数据通过标准处理流程进行优化，以确保记录的磁场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结构。GA的地球物理学家会对处理后的数据开展质量核查，以确保GA发布的最终数据满足实际应用需求。奇达拉- TMI RTP 1VD格网（AWAGS）是2017年南澳大利亚州（SA）奇达拉航空磁测、放射性测量与数字高程模型（Digital Elevation Model, DEM）测量项目中TMI RTP格网的一阶垂直导数。该格网的单元尺寸为0.0004度（约合41米），单位为纳特每米（nT/m）。生成该TMI格网所用的数据由南澳大利亚州政府于2017年采集，总测线长度达135047千米，测线间距为200米，飞行离地高度为60米。该数据已进行可变化极处理，使磁异常中心精准对准磁化体位置。本次可变化极（VRTP）处理采用了最高至5阶多项式的差分化极计算方法。地磁倾角与偏角由国际地磁参考场11代（International Geomagnetic Reference Field-11, IGRF-11）模型推导得出，所用参数匹配测量项目的代表性采集日期与区域海拔。通过对2017年南澳大利亚州奇达拉航空磁测、放射性测量与DEM测量项目的TMI RTP格网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，即本格网。本格网采用INTREPID地球物理软件包中的算法计算生成。该格网可反映具有不同磁化率的地下地质体的磁响应特征，还可用于识别岩脉等构造特征。