National Gravity Compilation 2019 - CSCBA 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 - CSCBA 0.5VD grid is derived 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). This gravity anomaly grid is 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 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 gravity data used in the national 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 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. Terrain corrections to gravity were calculated using both offshore bathymetry and onshore topography data. The grid shows half derivative of the complete Bouguer anomalies over Australia and its continental margins. A half vertical derivative was calculated by applying a fast Fourier transform (FFT) process to the complete spherical cap Bouguer anomaly grid of the 2019 Australian National Gravity Grids A series to produce this grid.

重力数据用于监测因地球表面下方岩石密度变化引发的微小重力场变化。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用于解译，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验，以确保GA发布的最终数据符合使用要求。

本2019年国家重力编目——CSCBA 0.5VD网格数据集，源自2019年澳大利亚国家重力网格A系列。该重力数据的采集工作依托项目编号202008完成。该网格的单元尺寸为0.00417度（约435米）。

本次重力异常网格数据集以2019年9月时点收录于澳大利亚国家重力数据库（Australian National Gravity Database, ANGD）的地面观测数据为基础构建，并补充使用了全球重力网格v28.1的海洋数据；全球重力网格v28.1的开发依托加州大学圣迭戈分校斯克里普斯海洋研究所（Scripps Institution of Oceanography, University of California San Diego）、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）的观测数据完成。

本次网格构建共使用了约180万条重力观测数据，其中包括ANGD中近140万个重力测站数据，以及总长度达34.5万千米的航空重力测量数据和10.6万千米的航空重力梯度测量数据。

本国家网格所使用的地面重力数据，采集时间跨度自20世纪40年代至今，数据来源包括澳大利亚联邦、州及领地政府、矿业与勘探行业、高校及科研机构。测站间距介于约11千米至不足1千米之间，澳大利亚大陆大部分区域的测站间距处于2.5千米至7千米范围内。重力地形校正计算同时使用了海洋水深数据与陆地地形数据完成。

该网格展示了澳大利亚及其大陆边缘区域完整布格异常的半导数结果。本网格的生成流程为：对2019年澳大利亚国家重力网格A系列的完整球冠布格异常网格应用快速傅里叶变换（Fast Fourier Transform, FFT）算法，计算得到垂直半导数结果，进而构建本次网格。