Yathong Magnetic Gradient and Radiometric Survey, NSW, 2023, (P5023), gradient enhanced total magnetic intensity, reduced to pole, first vertical derivative grid

TOTAL MAGNETIC INTENSITY Total Magnetic Intensity (TMI) data measures variations in the intensity of the Earth's magnetic field, which includes the fields associated with the Earth's core and the magnetism of rocks in the Earth's crust. The data are 'reduced' to highlight those variations caused by the geology in the Earth's crust. TMI data can be used to interpret sub-surface geological structure and has applications in mineral, energy and groundwater studies. GRADIENT ENHANCED GRID The data for this grid were acquired as part of a horizontal magnetic gradient survey, which uses three alkali-vapour magnetometers to measure longitudinal and transverse gradients. These gradients allow for a 'gradient enhanced' grid of the TMI data to be produced with improved near-surface information and reduced noise (such as that arising from diurnal changes in the magnetic field). REDUCTION TO POLEA Reduction to Pole (RTP) is applied to this grid to locate anomalies above the causative bodies, removing asymmetry caused by the inclination of the Earth's magnetic field. An RTP assumes that the anomalies are caused by induced magnetism (and remanent magnetism is not significant). FIRST VERTICAL DERIVATIVEA First Vertical Derivative (1VD) is applied to this grid which enhances the short-wavelength component of the field.GRID METADATA Units: Nanotesla per metre (nT/m); Cell size: 40 m ( degrees); Datum: EPSG:7844 Processing: Gradient enhanced + RTP + 1VD. LINE METADATA Line spacing: 200 m; Line direction: 90 degrees; Total line-kilometres: 65504 km; Nominal flying height (above ground level): 80 m; Acquisition Start Date: 2023-05-21; Acquisition End Date: 2023-09-14;

总磁场强度数据
总磁场强度（Total Magnetic Intensity, TMI）数据用于表征地球磁场强度的变化，涵盖地球核部磁场与地壳岩石磁性产生的磁场。该数据经归约处理以凸显地壳地质作用引发的磁场变化。TMI数据可用于解译地下地质构造，在矿产、能源与地下水研究中均有应用。

梯度增强网格
本网格的数据通过水平磁梯度测量获取，采用三台碱蒸气磁力仪测量纵向与横向磁梯度。基于上述梯度数据可生成TMI数据的“梯度增强”网格，该网格能够提供更精细的近地表信息，并抑制各类噪声（如磁场日变化产生的噪声）。

化极归约
本网格已应用化极归约（Reduction to Pole, RTP）处理，用于定位致磁体上方的磁异常，消除由地球磁场倾角引发的异常不对称性。化极归约假设磁异常由感应磁化产生，剩余磁化的影响可忽略不计。

一阶垂直导数
本网格已应用一阶垂直导数（First Vertical Derivative, 1VD）处理，用于增强磁场的短波分量。

网格元数据
单位：纳特斯拉每米（Nanotesla per metre, nT/m）；单元尺寸：40米（度）；基准面：EPSG:7844；处理流程：梯度增强+化极归约+一阶垂直导数。

测线元数据
测线间距：200米；测线方向：90度；总测线里程：65504千米；标称飞行高度（相对于地面）：80米；采集起始日期：2023-05-21；采集结束日期：2023-09-14。