Assessment of GPT2 Empirical Troposphere Model and Application Analysis in Precise Point Positioning
Precise Point Positioning (PPP) has been demonstrated to be a powerful tool in geodetic applications, such as deformation monitoring. Troposphere delay is an important error source which directly affects positioning accuracy in height direction. At the en
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Assessment of GPT2 Empirical Troposphere Model and Application Analysis in Precise Point Positioning Weirong Chen, Chengfa Gao and Shuguo Pan
Abstract Precise Point Positioning (PPP) has been demonstrated to be a powerful tool in geodetic applications, such as deformation monitoring. Troposphere delay is an important error source which directly affects positioning accuracy in height direction. At the end of 2012, an improved model named Global Pressure and Temperature 2 (GPT2) was proposed. Compared with early empirical models, this new model mainly eliminates the weakness of limited spatial and temporal variability. In this study, we assess the precision of GPT2 model and apply it in PPP analysis. The analysis data of VMF1, which is produced using European Centre for Medium-Range Weather Forecasts (ECMWF), provides the nearly true value of zenith delays and mapping function for International GNSS Service (IGS) stations. Therefore a globally distributed set of 11 IGS stations is chosen to validate GPT2 model. In the case of using GPT2 as a priori model while the residual zenith delay still estimated with other unknown parameters, it would improve the zenith troposphere delay adjustments to nearly zero-mean. Therefore GPT2 is helpful to improve the efficiency in PPP data processing. However, GPT2 model is only resting upon a global 5 grid and sufficient global troposphere models are not yet available. Due to the complexity of wet zenith delay, PPP height solutions would be unsatisfactory when residual troposphere delay is not parameterized. We conclude that GPT2 is capable of predicting troposphere delay worldwide with an acceptable uncertainty. And GPT2-based PPP solution performs well only in the case of regarding residual model error as an additional unknown parameter.
Keywords Global pressure and temperature 2 Zenith troposphere delay Mapping function Precise point positioning Global navigation satellite system
W. Chen (&) C. Gao School of Transportation, Southeast University, No. 2 Sipailou, Nanjing, China e-mail: [email protected] S. Pan School of Instrument Science and Engineering, Southeast University, No. 2 Sipailou, Nanjing, China
J. Sun et al. (eds.), China Satellite Navigation Conference (CSNC) 2014 Proceedings: Volume II, Lecture Notes in Electrical Engineering 304, DOI: 10.1007/978-3-642-54743-0_37, Springer-Verlag Berlin Heidelberg 2014
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37.1 Introduction With the help of precise satellite orbit and clock available from International GNSS service (IGS), Precise Point Positioning (PPP) [1, 2] becomes a very pragmatic tool in geodetic application, such as deformation monitoring. In satellite positioning, the Earth’s neutral atmosphere causes propagation delay of electromagnetic signal. The propagation path delay, which is often called troposphere delay, could be about 2.3 m at the zenith direction and 20 m at lower receiver-tosatellite direction such as elevation angles below 10 [3]. Therefore it is an important error source for precise geodetic positioning.
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