GSNSW Exploration NSW Area S Braidwood 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 0.00049 degrees (approximately 50m).The data are in nanoTesla (or nT). The data used to produce this grid was acquired in 2001 by the NSW Government, and consisted of 25736 line-kilometres of data at 250m 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.

总磁强度（Total Magnetic Intensity, TMI）数据用于测量由地壳中成岩矿物含量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。该数据经标准流程处理，以确保记录的磁场响应仅源于地下岩石。处理所得数据集可通过解译揭示地下地质构造。经处理的数据将由GA地球物理学家进行质量核查，以确保GA发布的最终数据符合使用要求。该磁网格的单元尺寸为0.00049度（约50米），数据单位为纳特斯拉（nanoTesla, nT）。该网格的原始数据由新南威尔士州（NSW）政府于2001年采集，总计25736线公里的测量数据，测线间距为250米，地形离地高度为60米。已对数据施加可变化极（Variable Reduction to the Pole, VRTP）处理，使磁异常中心对准磁化体位置。本次VRTP处理采用差分化极计算，最高阶数可达5次多项式。磁倾角与磁偏角基于国际地磁参考场11（IGRF-11）模型计算得出，所用日期与高程参数均匹配本次测量的代表性数据与地形条件。