The National Geospatial-Intelligence Agency (NGA) develops, maintains, and enhances the World Geodetic System 1984 (WGS 84), the reference frame upon which all geospatial intelligence is based.
World Geodetic System 1984 (WGS 84)
The World Geodetic System defines a reference frame for the earth, for use in geodesy and navigation. The latest revision is WGS 84 dating from 1984 (last revised in 2004), which will be valid up to about 2010.
A unified World Geodetic System became essential in the 1950s for several reasons:
- International space science and the beginning of astronautics.
- The lack of inter-continental geodetic information.
- The inability of the large geodetic systems, such as European Datum (ED50), North American Datum (NAD), and Tokyo Datum (TD), to provide a worldwide geo-data basis.
- Need for global maps for navigation, aviation, and geography.
NGA has served as a depository for geodetic and geophysical data for over 40 years and maintains several automated global digital databases within NGA. From these databases, we can retrieve Point Gravity Anomaly (PGA) data, Reference Base Stations (RBS) descriptions, and Global Positioning System (GPS) control data. We utilize these databases to maintain, enhance and update our products such as the WGS 84, Mean Gravity Anomalies, Deflections of the Vertical, Gravity Disturbances, Geoid Heights, Terrain Corrections, Geodetic Datum Transformations, and to satisfy other Department of Defense and Intelligence Community requirements. We currently maintain records on more than 50 million analyzed gravity points. The Geosciences Division continues to serve this function by actively collecting geodetic and geophysical data through various methods of acquisition including:
- Informal data exchange such as Quid Pro Quo exchanges
- Participating in international research ventures, such as the Arctic Gravity Project, with the academic/scientific community
- A Meter Loan Program that involves loaning geophysical measurement equipment in exchange for copies of the collected data