@article{TuGeZhangetal.2013,
  author    = {Tu, Rui and Ge, Maorong and Zhang, Hongping and Huang, Guanwen},
  title     = {The realization and convergence analysis of combined PPP based on raw observation},
  series = {Advances in space research},
  volume    = {52},
  journal   = {Advances in space research},
  number    = {1},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0273-1177},
  doi       = {10.1016/j.asr.2013.03.005},
  pages     = {211 -- 221},
  year      = {2013},
  abstract  = {In order to speed up Precise Point Positioning (PPP)'s convergence, a combined PPP method with GPS and GLONASS which is based on using raw observations is proposed, and the positioning results and convergence time have been compared with that of single system. The ionospheric delays and receiver's Differential Code Bias (DCB) corrections are estimated as unknown parameters in this method. The numerical results show that the combined PPP has not caused significant impacts on the final solutions, but it greatly improved Position Dilution of Precision (PDOP) and convergence speed and enhanced the reliability of the solution. Meanwhile, the convergence speed is greatly influenced by the receiver's DCB, positioning results in horizontal which are better than 10 cm can be realized within 10 min. In addition, the ionosphere and DCB products can be provided with high precision.},
  language  = {en}
}
@article{TuZhangGeetal.2013,
  author    = {Tu, Rui and Zhang, Hongping and Ge, Maorong and Huang, Guanwen},
  title     = {A real-time ionospheric model based on GNSS Precise Point Positioning},
  series = {Advances in space research},
  volume    = {52},
  journal   = {Advances in space research},
  number    = {6},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0273-1177},
  doi       = {10.1016/j.asr.2013.06.015},
  pages     = {1125 -- 1134},
  year      = {2013},
  abstract  = {This paper proposes a method of real-time monitoring and modeling the ionospheric Total Electron Content (TEC) by Precise Point Positioning (PPP). Firstly, the ionospheric TEC and receiver's Differential Code Biases (DCB) are estimated with the undifferenced raw observation in real-time, then the ionospheric TEC model is established based on the Single Layer Model (SLM) assumption and the recovered ionospheric TEC. In this study, phase observations with high precision are directly used instead of phase smoothed code observations. In addition, the DCB estimation is separated from the establishment of the ionospheric model which will limit the impacts of the SLM assumption impacts. The ionospheric model is established at every epoch for real time application. The method is validated with three different GNSS networks on a local, regional, and global basis. The results show that the method is feasible and effective, the real-time ionosphere and DCB results are very consistent with the IGS final products, with a bias of 1-2 TECU and 0.4 ns respectively.},
  language  = {en}
}