National Gravity Compilation 2019 includes airborne DGIR 0.5VD grid

Gravity data measure small changes in gravity due to changes in the density of rocks beneath the Earth's surface. The data collected 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 National Gravity Compilation 2019 includes airborne DGIR 0.5VD grid is produced from the 2019 Australian National Gravity Grids B series. These gravity data were acquired under the project No. 202008. The grid has a cell size of 0.00417 degrees (approximately 435m). The data are derived from ground observations stored in the Australian National Gravity Database (ANGD) as at September 2019, supplemented by offshore data sourced from v28.1 of the Global Gravity grid developed using data from the Scripps Institution of Oceanography, the National Oceanic and Atmospheric Administration (NOAA), and National Geospatial-Intelligence Agency (NGA) at Scripps Institution of Oceanography, University of California San Diego. Airborne gravity and gravity gradiometry data were also included to provide better resolution to areas where ground gravity data was not of a suitable quality. Out of the approximately 1.8 million gravity observations, nearly 1.4 million gravity stations in the ANGD together with Airborne Gravity surveys totaling 345,000 line km and 106,000 line km of Airborne Gravity Gradiometry were used to generate this grid. The ground and airborne gravity data used in this grid has been acquired by the Commonwealth, State and Territory Governments, the mining and exploration industry, universities and research organisations from the 1940's to the present day. Station spacing for ground observations varies from approximately 11 km down to less than 1 km, with major parts of the continent having station spacing between 2.5 and 7 km. Airborne surveys have a line spacing ranging from 0.5 km to 2.5 km. The grid shows the half vertical derivative of the de-trended global isostatic residual (DGIR) anomalies over Australia and its continental margins. The DGIR grid was obtained by subtracting 3 quantities (i.e., the near-field isostatic correction, the far-field isostatic correction, and a first order trend correction) from Complete Bouguer Anomaly data (CBA) of the 2019 Australian National Gravity Grids B series. A half vertical derivative was calculated by applying a fast Fourier transform (FFT) process to the DGIR grid of the 2019 Australian National Gravity Grids to produce this grid.

重力数据用于测量地球表面下岩石密度变化引起的重力微小变化。采集的数据通过标准方法处理，以确保记录的响应仅源于地下岩石。处理结果生成的数据集可通过解释揭示地下地质结构。处理后的数据由GA地球物理学家进行质量检查，以确保GA发布的最终数据符合预期用途。2019年国家重力汇编包含航空去趋势全球均衡残差（de-trended global isostatic residual, DGIR）0.5VD网格，该网格由2019年澳大利亚国家重力网格B系列生成。这些重力数据是在项目编号202008下采集的。该网格的单元格大小为0.00417度（约435米）。数据来源于截至2019年9月存储在澳大利亚国家重力数据库（Australian National Gravity Database, ANGD）中的地面观测数据，并补充了来自全球重力网格v28.1的近海数据——该全球重力网格利用加州大学圣地亚哥分校斯克里普斯海洋研究所、美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）以及国家地理空间情报局（National Geospatial-Intelligence Agency, NGA）的数据开发而成。航空重力和重力梯度测量数据也被纳入，以提高地面重力数据质量不佳区域的分辨率。在约180万次重力观测中，ANGD中的近140万个重力站点、总计34.5万公里的航空重力测量以及10.6万公里的航空重力梯度测量被用于生成该网格。该网格使用的地面和航空重力数据由联邦、州和地区政府、采矿与勘探行业、高校及研究机构自20世纪40年代至今采集。地面观测的站点间距从约11公里到不足1公里不等，大陆大部分地区的站点间距在2.5至7公里之间。航空测量的线间距范围为0.5公里至2.5公里。该网格显示了澳大利亚及其大陆边缘的去趋势全球均衡残差（DGIR）异常的半垂直导数。DGIR网格是通过从2019年澳大利亚国家重力网格B系列的完全布格异常数据（Complete Bouguer Anomaly, CBA）中减去三个量（即近场均衡校正、远场均衡校正和一阶趋势校正）得到的。半垂直导数是通过对2019年澳大利亚国家重力网格的DGIR网格应用快速傅里叶变换（fast Fourier transform, FFT）过程计算得到的，从而生成该网格。