Coober Pedy - 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 Coober Pedy - TMI RTP 1VD grid (AWAGS) is the first vertical derivative of the TMI RTP grid of the Coober Pedy West Airborne Magnetic Radiometric and DEM Survey, SA, 2017 survey.This grid has a cell size of 0.0004 degrees (approximately 42m) , 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 90697 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 Coober Pedy West 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.

总磁场强度（Total Magnetic Intensity, TMI）数据用于测量地壳中成岩矿物成分差异所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处理，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构造。经处理的数据由GA地球物理学家开展质量核查，以确保GA发布的最终数据符合使用要求。本次发布的库伯佩迪（Coober Pedy）-总磁场强度化极（TMI RTP）一阶垂直导数网格（AWAGS），源自2017年南澳大利亚州（South Australia, SA）库伯佩迪西部航空磁辐射与数字高程模型（Digital Elevation Model, DEM）测量任务的TMI RTP网格。该网格的单元格尺寸为0.0004度（约42米），单位为纳特每米（nT/m）。用于生成TMI网格的原始数据由南澳大利亚州政府于2017年采集，总测线长度达90697线公里，测线间距为200米，地形飞行高度为60米。该数据已应用可变化极处理，使磁异常中心对准磁化体上方。可变化极（Variable Reduction to the Pole, 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，结合测量任务的代表性数据采集日期与地形高程计算得到。通过对2017年南澳大利亚州库伯佩迪西部航空磁辐射与DEM测量任务的TMI RTP网格应用快速傅里叶变换（Fast Fourier Transform, FFT）流程，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。该网格可反映具有不同磁化率的地下地质体的磁响应，还可用于识别岩脉等构造特征。