Helen Spring - Evadowns, NT, 1993 (P611), magnetic line data, AWAGS levelled

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. These line dataset from the Helen Springs/Beetaloo, NT, 1993 survey were acquired in 1993 by the NT Government, and consisted of 117753 line-kilometres of data at a line spacing between 300m and 300m, and 100m terrain clearance. To constrain long wavelengths in the data, an independent data set, the Australia-wide Airborne Geophysical Survey (AWAGS) airborne magnetic data, was used to control the base levels of the survey data. This survey data is essentially levelled to AWAGS.

总磁场强度（Total Magnetic Intensity, TMI）数据用于衡量由地壳中成岩矿物成分差异所引起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。该数据通过标准流程进行处理，以确保记录的响应仅源自地下岩石。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。1993年北领地海伦斯普林斯/比塔卢测线项目的数据集由北领地政府于1993年采集，总测线长度达117753线千米，线间距为300米，飞行地形高度为100米。为约束数据中的长波长分量，本次测线数据采用独立数据集——全澳航空地球物理调查（Airborne Geophysical Survey, AWAGS）航空磁测数据——来校正测线数据的基准水平。本次测线数据实质上已参照AWAGS数据进行了平差处理。