National Gravity Compilation 2019 includes airborne (free air grid)

Gravity data measures 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 (free air grid) is a free air anomaly grid for the 2019 Australian National Gravity Grids B series. This gravity survey was acquired under the project No. 202008. This gravity anomaly grid is derived from ground observations stored in the Australian National Gravity Database (ANGD) as at September 2019, supplemented with 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 grid shows free air gravity anomalies over Australia and its continental margins. 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 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 has a cell size of 0.00417 degrees (approximately 435m). The data are given in units of um/s^2, also known as 'gravity units', or gu.

重力数据用于测量地球表层下方岩石密度变化引发的微小重力变动。所采集的数据将通过标准流程开展处理，以确保记录的响应仅源自地下岩石。经处理后的数据集可通过解译揭示地下地质构造。经处理的数据需由澳大利亚地质调查局（Geoscience Australia，GA）的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年国家重力汇编》包含航空（自由空气格网）数据，属于2019年澳大利亚国家重力格网B系列的自由空气异常格网。本次重力测量由项目编号202008牵头实施。该重力异常格网源自2019年9月前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，并补充了源自全球重力格网v28.1版的近海数据；该全球重力格网由加州大学圣迭戈分校斯克里普斯海洋研究所基于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）的数据研发而成。
为提升地面重力数据质量欠佳区域的分辨率，本数据集还纳入了航空重力及航空重力梯度测量数据。在总计约180万条重力观测数据中，科研团队采用了ANGD内近140万个重力测点，以及总长34.5万千米的航空重力测量数据与10.6万千米的航空重力梯度测量数据，以此生成本格网。
该格网展示了澳大利亚及其大陆边缘的自由空气重力异常。本格网所使用的地面与航空重力数据，由联邦、州及领地政府、矿业勘探行业、高校与科研机构自20世纪40年代至今采集所得。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。航空测量的测线间距为0.5千米至2.5千米。该格网的单元尺寸为0.00417度（约合435米）。数据单位为微米每二次方秒（μm/s²），亦称为“重力单位”（gravity units, gu）。