Analysis and Comparison of Integrated Water Vapor Estimation from GPS

A.G.A. van der Hoeven, B.A.C. Ambrosius, H. van der Marel, H. Derks, H. Klein Baltink, A. van Lammeren, A.J.M. Kösters

Abstract:	In the Netherlands a network of five permanent GPS receivers is operated (AGRS.NL). The Delft University of Technology (DUT), in collaboration with the Royal Netherlands Meteorological Institute (KNMI) and Survey Department of Rijkswaterstaat, processes this data on a daily basis, together with selected stations from the IGS network. Vertically integrated water vapor (IWV) estimates are computed every six minutes, with a delay of 1-2 days. Since 1 July 1997 the IWV timeseries is stored at the KNMI, in addition to radiosonde data and IWV forecasts from the Regional Atmospheric Climate Model (RACMO). In addition, during three experimental campaigns (CLARA) the GPS receiver in Delft was collocated with a microwave radiometer (WVR) and radiosonde launches. During one other period the GPS receiver was collocated only with a microwave radiometer. Using the database of GPS IWV data, IWV derived from radiosonde launches, radiometer measurements and RACMO IWV predictions, the accuracy and reliability of the GPS IWV estimates is assessed. In this paper the GPS IWV estimates are compared to radiosonde, radiometer and RACMO IWV predictions. The comparisons have also been used to optimize the GPS processing and the computation of GPS IWV. The target of this optimization was to develop a processing method which is able to perform IWV estimations in near real-time. This target is met by incorporating an orbit relaxation in the process, generating a result which is independent of the accuracy of a priori orbit data generated by IGS or any other institute. The results of several tests are reported. Finally, it is shown that GPS proves to be a reliable, all weather system, which is capable of estimating IWV with an accuracy of 0,5-1 kg/m 2 .
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	749 - 755
Cite this article:	Hoeven, A.G.A. van der, Ambrosius, B.A.C., Marel, H. van der, Derks, H., Baltink, H. Klein, van Lammeren, A., Kösters, A.J.M., "Analysis and Comparison of Integrated Water Vapor Estimation from GPS," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 749-755.
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