Atmospheric modelling in GPS analysis and its effect on the estimated geodetic parameters |
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| Authors: | T R Emardson P O J Jarlemark |
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| Institution: | (1) Onsala Space Observatory, Chalmers University of Technology, Onsala, Sweden, e-mail: tre@oso.chalmers.se; Tel.: +46 31 772 5575; Fax: +46 31 772 5590 Now at Jet Propulsion Laboratory, California Institute of Technology, MS 238-600, 4800 Oak Grove Drive, Pasadena, CA 91109, USA, e-mail: emardson@cobra.jpl.nasa.gov; Tel.: +1 818 354 4399; Fax: +1 818 393 4965, SE;(2) Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA, US |
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| Abstract: | Permanently operating Global Positioning System (GPS) receivers are used today, for example, in precise positioning and determination
of atmospheric water vapour content. The GPS signals are delayed by various gases when traversing the atmosphere. The delay
due to water vapour, the wet delay, is difficult to model using ground surface data and is thus often estimated from the GPS
data. In order to obtain the most accurate results from the GPS processing, a modelling of the horizontal distribution of
the wet delay may be necessary. Through simulations, three such models are evaluated, one of which is developed in this paper.
In the first model the water vapour is assumed to be horizontally stratified, thus the wet delay can be described by only
one zenith parameter. The second model gives the wet delay with one zenith and two horizontal gradient parameters. The third
model uses the correlation between the wet-delay values in different directions. It is found that for large gradients and
strong turbulence the two latter models yield lower errors in the estimated vertical coordinate and wet-delay parameters.
For large gradients this improvement is up to 7 mm in the zenith wet-delay parameter, from 9 mm down to 2 and 4 mm for the
second and third models, respectively.
Received: 7 May 1998 / Accepted: 1 March 1999 |
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| Keywords: | , Space Geodesy,Global Positioning System,Kalman Filtering,Atmospheric modelling |
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