GSNSW Exploration NSW Area A3 Bancannia Trough magnetic rtp 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 magnetic grid has a cell size of 0.00063 degrees (approximately 65m).The data are in nanoTesla (or nT). The data used to produce this grid was acquired in 1995 by the NSW Government, and consisted of 21000 line-kilometres of data at 400m line spacing and 80m 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.

总磁强度（Total Magnetic Intensity, TMI）数据用于表征由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。本数据集通过标准化流程开展处理，以确保所记录的响应仅源于地下岩石的影响。经处理得到的数据集可用于解译，以揭示地下地质结构。经处理的数据会由GA地球物理学家进行质量核验，确保GA发布的最终数据符合使用要求。该磁网格的单元尺寸为0.00063度（约合65米），数据单位为纳特斯拉（nanoTesla, nT）。该网格所用数据由新南威尔士州（New South Wales, NSW）政府于1995年采集，涵盖21000线公里的测线数据，测线间距为400米，地形离地高度为80米。数据已施加可变极化归算（Variable Reduction to the Pole, VRTP），使磁异常中心位于磁化体正上方。该VRTP处理采用差分极化归算方法，最高可至5阶多项式展开。磁倾角与磁偏角基于IGRF-11地磁参考模型（International Geomagnetic Reference Field-11, IGRF-11）计算得到，所用数据的代表日期与高程均匹配该次勘测的实际情况。