GSNSW Exploration NSW Area F Brewarrina 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 0.00048 degrees (approximately 50m).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 51199 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（磁场强度高于正常水平）与负异常（磁场强度低于正常水平），具体取决于岩石的磁化率。该数据通过标准流程进行处理，以确保记录的响应仅源于地下岩石的影响。处理后得到的数据集可通过解译揭示地下地质结构。经处理的数据由GA的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。该磁网格的单元尺寸为0.00048度（约合50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政府（NSW Government）于1995年采集，总测线长度达51199测线公里，测线间距为250米，航测离地高度为60米。该数据已应用变极化归算（Variable Reduction to the Pole，VRTP），使磁异常中心位于磁化体的正上方。本次VRTP处理采用了最高至5阶多项式的差分极化归算方法。磁倾角与磁偏角由IGRF-11地磁参考模型推导得出，所用数据代表本次测量的典型采集时间与高程。