Darwin (Urban Development), NT, 1974 (P411), 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 Darwin (Urban Development), NT, 1974 survey were acquired in 1974 by the NT Government, and consisted of 803 line-kilometres of data at 500m line spacing and 150m 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）数据用于量化地壳内造岩矿物成分差异所引发的地球磁场强度变化。磁异常（magnetic anomalies）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）两类，其分类取决于岩石的磁化率。该数据集通过标准流程进行预处理，以确保记录的响应仅源自地下岩石。经处理得到的数据集可通过解译揭示地下地质构造。经处理的数据由GA地球物理学家开展质量校验，确保GA对外发布的最终数据满足使用需求。本次测线数据集源自1974年北领地（Northern Territory, NT）达尔文市（城市发展项目）航磁调查，由NT政府于1974年采集，总数据覆盖长度达803线千米，测线间距为500米，飞行离地高度为150米。为约束数据中的长波长成分，本次调查采用独立数据集——全澳航空地球物理调查（Australia-wide Airborne Geophysical Survey, AWAGS）航磁数据——对测线数据的基准水平进行校正。本次调查数据已基本基于AWAGS数据完成基准平差。