Maintenance and Enhancement of the World Geodetic System 1984

Stephen Malys and James Slater

Abstract:	The advent of Earth orbiting satellites more than 35 years ago allowed the development of practical global geodetic reference frames. One of the first of these global reference frames was the Department of Defense (DOD) World Geodetic System 1960. This was succeeded by improved systems in 1966 and 1972 and culminated in development of the World Geodetic System 1984 (WGS 84) ten years ago. This Conventional Terrestrial Reference System provides a coherent set of global models and definitions which form the basis for all current DOD mapping, charting, navigation and geodesy. The WGS 84 terrestrial reference frame was realized through Doppler observations from the TRANSIT satellite system using a globally distributed set of tracking stations. These TRANSIT satellite techniques provided a global reference frame with an estimated accuracy of 1 to 2 meters. Parallel efforts by the worldwide scientific community have resulted in the development of other highly-accurate (sub-decimeter) terrestrial reference frames. The most recent development in this area has been an annual series of International Earth Rotation Service (IERS) Terrestrial Reference Frames (ITRF). These frames are based on observations from satellite and lunar laser ranging, very long baseline interferometry and the Global Positioning System (GPS). These efforts are driven by scientific applications which require millimeter-level accuIibcy* While mapping, charting and navigation applications can still be satisfied by the meter-level positioning accuracy achievable with the original implementation of WGS 84, the DOD’S geodetic positioning requirements now demand an accuracy level on the order of a few decimeters. For these reasons, DMA is undertaking a review of WGS 84 and has initiated a maintenance and enhancement effort to satisfy the more demanding DOD requirements for accuracy and precision. This paper presents pertinent background on the development of WGS 84, the status of current maintenance and enhancement efforts, and future plans. These efforts include improved DOD GPS tracking station coordinates, refinements to the Earth gravity model, establishment of the improved WGS 84 geoid as the preferred world vertical reference, and an examination of the other models and parameters embodied in the definition of WGS 84.
Published in:	Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994) September 20 - 23, 1994 Salt Palace Convention Center Salt Lake City, UT
Pages:	17 - 24
Cite this article:	Malys, Stephen, Slater, James, "Maintenance and Enhancement of the World Geodetic System 1984," Proceedings of the 7th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1994), Salt Lake City, UT, September 1994, pp. 17-24.
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