The Development of a Global Surface Gravity Data Base to be Used in the Joint DMA/GSFC Geopotential Model

Abstract

The Defense Mapping Agency (DMA) and NASA/Goddard Space Flight Center (GSFC) are currently involved in the development of a global gravity model complete to degree and order 360. This effort requires the compilation of a worldwide set of 30’x30’ surface mean free-air gravity anomalies. The extensive data archive at DMA is the main source of gravity information from which the 30’ mean values are estimated. New sources of terrestrial gravity data used in the model will include the former Soviet Union, Greenland, South America, Africa, Southeast Asia, Antarctica, and the Arctic. Improvements to current terrestrial sources have been made in North America, Europe, and Australia. However, several areas have been identified which are still lacking detailed and accurate gravity information and emphasize the need to intensify data collection efforts. Substantial effort is made to ensure accurate and consistent processing of the point gravity anomaly data used in the estimation of the 30’ mean values. This effort is aimed at producing a global set of mean values with significantly reduced long wavelength systematic errors. The mean values and their accuracies are estimated using least-squares collocation and remove-restore techniques implemented at DMA. For the reduction process, consistent 1’ and 5’ elevation databases were compiled by DMA and GSFC using the best worldwide elevation sources currently available. This paper describes the data being used in the project and the computational procedures being implemented.