Handling of the Tropospheric Delay in Kinematic Precise Point Positioning

N.S. Kjørsvik, J.G.O. Gjevestad, O. Øvstedal

Abstract:	The GPS Standard Positioning Service (SPS) gives a horizontal accuracy of approximately 3–5 m (95%). When operating in differential mode, a number of error sources are mitigated and positional accuracy ranging from a few meters to sub-centimeters can be achieved. In recent years precise satellite ephemerides, satellite clock corrections and earth orientation parameters have become freely available from the International GNSS Service (IGS). For a number of applications the approach of Precise Point Positioning (PPP) has become a viable alternative to differential methods. In PPP dual frequency code and carrier phase observations from a single GPS receiver are used to estimate receiver coordinates and receiver clock errors as well as a few extra nuisance parameters. In undifferenced GPS observations, the presence of remaining hardware biases makes identification of the integer carrier phase ambiguities difficult. Hence, in PPP processing the carrier phase ambiguities are estimated as real numbers. Tropospheric errors are usually handled using (i) corrections from a standard model fed with a priori meteorological parameters, (ii) corrections from a standard model fed with meteorological observations or (iii) by estimating the effect together with other parameters. A priori meteorological parameters may be of inferior quality and reliable meteorological observations may be unavailable. Troposphere parameters will be highly correlated with other parameters when estimated using short observation spans leading to degraded accuracy and a less resistance against outliers and bad observations. The question then raised is how to best handle the tropospheric delay in different PPP applications. This paper presents a discussion on how to handle tropospheric delay in kinematic PPP processing, some results from kinematic processing of real test data using different processing strategies and some preliminary recommendations.
Published in:	Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006) September 26 - 29, 2006 Fort Worth Convention Center Fort Worth, TX
Pages:	2279 - 2281
Cite this article:	Kjørsvik, N.S., Gjevestad, J.G.O., Øvstedal, O., "Handling of the Tropospheric Delay in Kinematic Precise Point Positioning," Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006), Fort Worth, TX, September 2006, pp. 2279-2281.
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