GSQ Drummond Galilee Qld magnetic 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 GSQ Drummond Galilee Qld magnetic vd1 grid geodetic is a first vertical derivative of the Total Magnetic Intensity grid for the Drummond & Galilee Qld, (Geomap 2005) GDI 1997/1998.This grid has a cell size of 0.00096 degrees (approximately 103m). The grid has units of nanoTesla per km (or nT/km). The data used to produce the TMI grid was acquired in 1997 by the QLD Government, and consisted of 198262 line-kilometres of data at 400m 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场）与负异常（磁场强度低于正常背景场），其类型取决于岩石的磁化率。该数据需通过标准流程开展处理，以确保所记录的磁场响应仅源自地下岩石。处理所得数据集可通过地质解译揭示地下地质结构。经处理的数据将由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使用需求。本GSQ昆士兰州德拉蒙德-加里利磁vd1大地测量网格，是针对昆士兰州德拉蒙德与加里利区域（Geomap 2005）GDI 1997/1998的总磁场强度网格计算得到的一阶垂直导数数据。该网格的单元尺寸为0.00096度（约103米），量纲为纳特斯拉每千米（即nT/km）。用于生成该总磁场强度网格的数据由昆士兰州政府于1997年采集，数据总测线长度为198262线千米，测线间距为400米，航空观测离地高度为80米。研究人员采用快速傅里叶变换（Fast Fourier Transform, FFT）算法对原始总磁场强度网格进行处理，以计算得到该一阶垂直导数网格。