@article{TuWangWalteretal.2014,
  author    = {Tu, Rui and Wang, Rongjiang and Walter, Thomas R. and Diao, FaQi},
  title     = {Adaptive recognition and correction of baseline shifts from collocated GPS and accelerometer using two phases Kalman filter},
  series = {Advances in space research},
  volume    = {54},
  journal   = {Advances in space research},
  number    = {9},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0273-1177},
  doi       = {10.1016/j.asr.2014.07.008},
  pages     = {1924 -- 1932},
  year      = {2014},
  abstract  = {The real-time recognition and precise correction of baseline shifts in strong-motion records is a critical issue for GPS and accelerometer combined processing. This paper proposes a method to adaptively recognize and correct baseline shifts in strong-motion records by utilizing GPS measurements using two phases Kalman filter. By defining four kinds of learning statistics and criteria, the time series of estimated baseline shifts can be divided into four time intervals: initialization, static, transient and permanent. During the time interval in which the transient baseline shift is recognized, the dynamic noise of the Kalman filter system and the length of the baseline shifts estimation window are adaptively adjusted to yield a robust integration solution. The validations from an experimental and real datasets show that acceleration baseline shifts can be precisely recognized and corrected, thus, the combined system adaptively adjusted the estimation strategy to get a more robust solution. (C) 2014 COSPAR. Published by Elsevier Ltd. All rights reserved.},
  language  = {en}
}
@article{Tu2014,
  author    = {Tu, Rui},
  title     = {Fast determination of displacement by PPP velocity estimation},
  series = {Geophysical journal international},
  volume    = {196},
  journal   = {Geophysical journal international},
  number    = {3},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0956-540X},
  doi       = {10.1093/gji/ggt480},
  pages     = {1397 -- 1401},
  year      = {2014},
  abstract  = {Global Positioning System (GPS) has been proven to be an effective tool to retrieve high-precision displacement for the natural hazard monitoring. The network positioning and Precise Point Positioning (PPP) are the two basic approaches for its data solution, but the former one can only get a relative displacement within the local reference frame and requires a complex and continuously linked infrastructure, and the latter one with a long convergence time to obtain the absolute displacements within the global reference frame. To overcome these drawbacks, this paper proposed a method of fast determining the displacement by PPP velocity estimation (PPPVE). The key of the approach is that the velocity vector parameters are not correlated with other unknown parameters, such as ambiguities and atmosphere, so they can be fast and accurately estimated and integrated into displacements. The validation shows that the displacement can be provided with a precision of 1-2 cm in 1 min by PPPVE. In additional, the Kalman smoothing estimation can be used to improve the PPP solution.},
  language  = {en}
}
@article{TuChen2014,
  author    = {Tu, Rui and Chen, Kejie},
  title     = {Tightly integrated processing of high-rate GPS and accelerometer observations by real-time estimation of transient baseline shifts},
  series = {The journal of navigation},
  volume    = {67},
  journal   = {The journal of navigation},
  number    = {5},
  publisher = {Cambridge Univ. Press},
  address   = {New York},
  issn      = {0373-4633},
  doi       = {10.1017/S0373463314000150},
  pages     = {869 -- 880},
  year      = {2014},
  abstract  = {The complementary advantages of high-rate Global Positioning System (GPS) and accelerometer observations for measuring seismic ground motion have been recognised in previous research. Here we propose an approach of tight integration of GPS and accelerometer measurements. The baseline shifts of the accelerometer are introduced as unknown parameters and estimated by a random walk process in the Precise Point Positioning (PPP) solution. To demonstrate the performance of the new strategy, we carried out several experiments using collocated GPS and accelerometer. The experimental results show that the baseline shifts of the accelerometer are automatically corrected, and high precision coseismic information of strong ground motion can be obtained in real-time. Additionally, the convergence and precision of the PPP is improved by the combined solution.},
  language  = {en}
}
@article{TuGeWangetal.2014,
  author    = {Tu, Rui and Ge, Maorong and Wang, Rongjiang and Walter, Thomas R.},
  title     = {A new algorithm for tight integration of real-time GPS and strong-motion records, demonstrated on simulated, experimental, and real seismic data},
  series = {Journal of seismology},
  volume    = {18},
  journal   = {Journal of seismology},
  number    = {1},
  publisher = {Springer},
  address   = {Dordrecht},
  issn      = {1383-4649},
  doi       = {10.1007/s10950-013-9408-x},
  pages     = {151 -- 161},
  year      = {2014},
  abstract  = {The complementary advantages of GPS and seismic measurements are well recognized in seismotectonic monitoring studies. Therefore, integrated processing of the two data streams has been proposed recently in an attempt to obtain accurate and reliable information of surface displacements associated with earthquakes. A hitherto still critical issue in the integrated processing is real-time detection and precise estimation of the transient baseline error in the seismic records. Here, we report on a new approach by introducing the seismic acceleration corrected by baseline errors into the state equation system. The correction is performed and regularly updated in short epochs (with increments which may be as short as seconds), so that station position, velocity, and acceleration can be constrained very tightly and baseline error can be estimated as a random-walk process. With the adapted state equation system, our study highlights the use of a new approach developed for integrated processing of GPS and seismic data by means of sequential least-squares adjustment. The efficiency of our approach is demonstrated and validated using simulated, experimental, and real datasets. The latter were collected at collocated GPS and seismic stations around the 4 April 2010, E1 Mayor-Cucapah earthquake (Mw, 7.2). The results have shown that baseline errors of the strong-motion sensors are corrected precisely and high-precision seismic displacements are real-timely obtained by the new approach.},
  language  = {en}
}
@article{TuWang2014,
  author    = {Tu, Rui and Wang, Li},
  title     = {Real-time coseismic wave retrieving by integrated Kalman filter with observations of GPS, Glonass and strong-motion sensor},
  series = {Advances in space research},
  volume    = {53},
  journal   = {Advances in space research},
  number    = {1},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0273-1177},
  doi       = {10.1016/j.asr.2013.10.011},
  pages     = {130 -- 137},
  year      = {2014},
  abstract  = {A method of real-time coseismic wave retrieving was proposed based on the tight integration of GPS, Glonass and strong-motion sensor observations, the validation and precision analysis have been made by an experimental data. The series of results have been shown that: by the integrated Kalman filter and multi-sensors, the coseismic waves can be optimally recovered by complement the advantages of each other, especially when the observation conditions are very bad. In additional, the results are not significantly effected by different receiver clock error processes for the integration solution.},
  language  = {en}
}
@misc{TuChen2014,
  author    = {Tu, Rui and Chen, Kejie},
  title     = {Tightly integrated processing of high-rate GPS and accelerometer observations by real-time estimation of transient baseline shifts},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe},
  number    = {598},
  doi       = {10.25932/publishup-41518},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-415182},
  pages     = {869 -- 881},
  year      = {2014},
  abstract  = {The complementary advantages of high-rate Global Positioning System (GPS) and accelerometer observations for measuring seismic ground motion have been recognised in previous research. Here we propose an approach of tight integration of GPS and accelerometer measurements. The baseline shifts of the accelerometer are introduced as unknown parameters and estimated by a random walk process in the Precise Point Positioning (PPP) solution. To demonstrate the performance of the new strategy, we carried out several experiments using collocated GPS and accelerometer. The experimental results show that the baseline shifts of the accelerometer are automatically corrected, and high precision coseismic information of strong ground motion can be obtained in real-time. Additionally, the convergence and precision of the PPP is improved by the combined solution.},
  language  = {en}
}