Tropospheric Delay Estimation from a Moving GPS Receiver

Mike Pattinson, Alan Dodson and Terry Moore

Abstract:	During the last decade there has been significant research into the use of GPS as a measurement tool for atmospheric water vapour content. The main limitation of the technique at the moment is that the GPS receivers must be static and so must, in reality, be land based receivers. It would be useful to extend the technique to work from moving GPS receivers as this would allow estimates of tropospheric delay, and hence atmospheric water vapour content, to be obtained from ocean based ships, buoys or aircraft, which would improve the spatial resolution of the current GPS technique. Measurements of water vapour from aircraft would allow a vertical profile of the atmospheric water vapour content to be obtained, rather than just a single zenith value. The main problem with extending the technique to a moving receiver is that the position of the receiver changes every epoch, and so the height and delay variations, which are highly correlated, must be separated correctly. Recent research at the IESSG by Dodson et al (2001) and in the US by Chadwell and Bock (2001) has shown that, for short baselines, it is possible to obtain estimates of total zenith delay at buoy based receivers with an rms difference of less than 5 mm, compared to the known delay at a nearby base receiver. The work described in this paper tries to build on the previous research in two main areas. The first part of the paper describes a trial that was performed in May 2001 to try and extend the baseline length over which the tropospheric delay could be estimated. It was found that the tropospheric delay could be estimated over an 18 km baseline with a bias of 3.8 mm and a rms difference of 6.4 mm, compared to the known delay at a reference receiver less than 1 km from the boat. The second part of the paper attempts to estimate the tropospheric delay at a moving GPS receiver for an aircraft take-off scenario. Using simulated GPS data, it was found that the height and delay variation could be separated successfully, using a modified prediction model for the tropospheric delay in the Kalman filter.
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:	2294 - 2303
Cite this article:	Pattinson, Mike, Dodson, Alan, Moore, Terry, "Tropospheric Delay Estimation from a Moving GPS Receiver," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 2294-2303.
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