Geodesy Considerations for Precise Wide Area Differential Global Positioning Systems

Malcolm A. B. Jones

Abstract:	With the development of High Accuracy WADS (wide area differential GPS services) it has become obvious that we need to examine at a greater level of magnitude what the Provider's of these systems supply to users. The establishment of ITRF (International Terrestrial Reference Frame) and its operations has brought the ideals of absolute coordinates to the humble field surveyor to a whole new level. The ability to very accurately measure and monitor the movements of tectonic plates. This paper looks at those areas of geodesy that might be a problem when using High Accuracy WADS with respect to globally, and locally managed coordinate systems. When a sparse series of measurements are used to produce realtime positioning that is in the order of a decimetre across tectonic plate boundaries, issues arise about the coordinates provided to the end user. Discontinuities exist at the boundaries, and slow, time dependent degradation of positioning accuracy occurs, at different rates. Geodesy factors are looked at everyone's point of view. The factors include ones the supplier has no influence over, ones they may have an influence over, and ones their clients might have an influence over. There is often going to be a trade off between geodetic accuracy and integrity, and user requirements. Height (and therefore scale - even though mentioned here) was considered during the research for this paper, but has been left out of the final deliberation. This was due to time constraints and the consideration that it would develop into a sizeable research project on its own.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	1380 - 1387
Cite this article:	Jones, Malcolm A. B., "Geodesy Considerations for Precise Wide Area Differential Global Positioning Systems," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 1380-1387.
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