MRTAS Western Tasmania tmi vd1 grid geodetic

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 MRTAS Western Tasmania tmi vd1 grid geodetic is a first vertical derivative of the Total Magnetic Intensity grid for the Western Tasmania, Tas, 2001 (WTRMP Area C).This grid has a cell size of 0.00042 degrees (approximately 41m). The grid has units of nanoTesla per km (or nT/km). The data used to produce the TMI grid was acquired in 2001 by the TAS Government, and consisted of 44149 line-kilometres of data at 200m line spacing and 80m terrain clearance. A Fast Fourier Transform (FFT) process was applied to the original grid to calculate the first vertical derivative grid.

总磁场强度（Total Magnetic Intensity，TMI）数据用于表征地壳中成岩矿物含量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），其类型取决于岩石的磁化率。该数据通过标准化流程进行处理，以确保记录的磁场响应仅源自地下岩石。经处理得到的数据集可通过地质解译揭示地下地质结构。经处理的数据由GA地球物理学家开展质量核查，以确保GA发布的最终数据满足实际应用需求。本MRTAS西塔斯马尼亚TMI VD1大地测量格网，为2001年塔斯马尼亚州西塔斯马尼亚地区（WTRMP C区）总磁场强度格网的一阶垂向导数格网。该格网的单元尺寸为0.00042度（约合41米），量纲为纳特斯拉每千米（nT/km）。用于生成该TMI格网的野外数据由塔斯马尼亚州政府于2001年采集，总测线长度达44149千米，测线间距为200米，观测时的地形离地高度为80米。采用快速傅里叶变换（Fast Fourier Transform，FFT）算法对原始格网进行处理，可计算得到一阶垂向导数格网。