Improved Tropospheric Delay Modeling Using an Integrated Approach of Numerical Weather Models and GPS

Torben Schueler, Guenter W. Hein and Bernd Eissfeller

Abstract:	The error budget of modeling tropospheric delays comprises the uncertainty of the hydrostatic and the wet component as well as the inaccuracies of the mapping functions. The idea presented in this paper is to apply numerical weather models for the needs of determining tropospheric propagation delays. A special approach is discussed that reduces the 3-D weather fields to a 2-D data representation. The surface-referenced global gridded tropospheric correction data of these "TROPEX" files (TROPospheric EXchange format) contain the hydrostatic component that is represented by surface pressure and the wet component that is retrieved by integration of the vertical wet refractivity profile for each grid point. The problem of height reduction is addressed by least-squares vertical profile fits to special reduction models. Finally, permanent tracking networks like the IGS net are providing zenith neutral delays. These data are not regularly gridded and the spatial resolution is often not sufficient to allow precise interpolation for arbitrary sites. This paper also presents a relatively simple and time- efficient approach to combine the results obtained from numerical weather models with those of GPS in order to make use of the high accuracy potential of GPS-derived estimates and thereby to improve the gridded data sets. This is done by a nearest-neighbor approach and optimized stochastic modeling applying variance components.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	600 - 615
Cite this article:	Schueler, Torben, Hein, Guenter W., Eissfeller, Bernd, "Improved Tropospheric Delay Modeling Using an Integrated Approach of Numerical Weather Models and GPS," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 600-615.
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