The Use Of Ground-Based GPS For Water Vapour Estimation

H. C. Baker, A. H. Dodson, T. Moore

Abstract:	A major error source in GPS measurements for precise height applications is the wet path delay due to tropospheric water vapour. It has recently been demonstrated that the tropospheric Zenith Wet Delay (ZWD) can be estimated using the GPS data itself and converted to equivalent Integrated Water Vapour (IWV) content with little additional uncertainty (where 1 kg/m 2 IWV is equal to 1 mm Integrated Precipitable Water Vapour, and equates approximately to 6.5 mm ZWD) . One of the major factors in achieving accurate estimates on a near real time basis (less than a few hours) is the availability of reliable, accurate orbits. Tests have therefore been performed investigating the accuracy of GPS water vapour estimates using a number of current, freely available, rapid and predicted orbits in comparison to the IGS precise ephemeris. Initial results indicate that rapid orbit water vapour estimates compare to better than 1 kg/m 2 , and predicted orbit water vapour estimates at 1-4 kg/m 2 level, with significant improvement in estimates when they are differenced.
Published in:	Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997) September 16 - 19, 1997 Kansas City, MO
Pages:	179 - 186
Cite this article:	Baker, H. C., Dodson, A. H., Moore, T., "The Use Of Ground-Based GPS For Water Vapour Estimation," Proceedings of the 10th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1997), Kansas City, MO, September 1997, pp. 179-186.
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