National Gravity Compilation 2019 DGIR 1VD 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 DGIR 1VD grid is produced from the 2019 Australian National Gravity Grids A 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. Out of the approximately 1.8 million gravity observations, nearly 1.4 million gravity stations in the ANGD together with marine data were used to generate this grid. The ground 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. The grid shows the first vertical derivative of the de-trended global isostatic residual anomalies (A series) over Australia and its continental margins. The original DGIR 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 A series. A first 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（Gravity data）用于测量因地球浅表岩石密度变化所引发的微小重力扰动。所采集的数据将通过标准流程进行处理，以确保记录的响应仅源于地下岩石的影响。经处理后得到的数据集可通过解译，用以揭示地下地质构造。经处理的数据将由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。本《2019年国家重力编录》DGIR 1VD网格数据集基于2019年澳大利亚国家重力网格A系列（2019 Australian National Gravity Grids A series）生成，该批重力数据采自编号为202008的项目，该网格的单元格尺寸为0.00417度（约合435米）。本数据集的数据源自截至2019年9月存储于澳大利亚国家重力数据库（Australian National Gravity Database, ANGD）的地面观测数据，并补充了由全球重力网格v28.1版获取的近海数据；该全球重力网格依托加利福尼亚大学圣迭戈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）以及美国国家地理空间情报局（National Geospatial-Intelligence Agency, NGA）的相关数据研发而成。在总计约180万条重力观测数据中，ANGD内近140万个重力测点与海洋观测数据被用于生成本网格。本网格所使用的地面重力数据采集时段为1940年代至今，采集方包括澳大利亚联邦政府、各州及领地政府、矿业与勘探行业、高校及科研机构。地面观测的测点间距范围约为11千米至不足1千米，澳大利亚大陆大部分区域的测点间距介于2.5千米至7千米之间。本网格展示了澳大利亚及其大陆边缘区域去趋势后的全球均衡剩余异常（A系列）的一阶垂直导数。原始DGIR数据集通过从2019年澳大利亚国家重力网格A系列的完整布格异常（Complete Bouguer Anomaly, CBA）数据中减去三项校正量，即近场均衡校正、远场均衡校正及一阶趋势校正，得到。本网格通过对2019年澳大利亚国家重力网格的DGIR数据集应用快速傅里叶变换（Fast Fourier Transform, FFT）算法，计算得到其一阶垂直导数而生成。