Honeysuckle Creek tmi 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 0.00021 degrees (approximately 21m).The data are in nanoTesla (or nT). The data used to produce this grid was acquired in 2001 by the VIC Government, and consisted of 14795 line-kilometres of data at 100m 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引发的地球磁场强度变化。磁异常可依据岩石磁化率的差异表现为正异常（磁场强度高于正常值）或负异常（磁场强度低于正常值）。该数据已通过标准化流程处理，以确保所记录的磁场响应仅源于地下岩石。经处理得到的数据集可通过解译，揭示地下地质构造。经处理的数据已由GA地球物理学家开展质量核验，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0.00021度（约合21米），数据单位为纳特斯拉（nanoTesla，nT）。该网格所用数据由维多利亚州（VIC）政府于2001年采集，总测线长度达14795线公里，测线间距为100米，航测地形离地高度为60米。已对该数据施加变极化归算（variable reduction to the pole，VRTP）处理，使磁异常中心与磁化体位置重合。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。磁倾角与磁偏角基于国际地磁参考场11代（International Geomagnetic Reference Field-11，IGRF-11）地磁参考场模型计算得到，计算所用的代表日期与高程均匹配该次勘测的实际情况。