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Dai W.,Central South University | Dai W.,Key Laboratory of Precise Engineering Surveying and Deformation Disaster Monitoring of Hunan Province | Chen Z.,Central South University | Chen Z.,Key Laboratory of Precise Engineering Surveying and Deformation Disaster Monitoring of Hunan Province | And 4 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2011

In this paper, the effects of height difference and the horizontal change of troposphere on the accuracy of GPS surveying is discussed at first. And then GPS observation data collected in several years from Hong Kong Continuously Reference Station Network is used to model the precise tropospheric delay. This model is based on estimated zenith tropospheric delay of all the stations using the Bernese GPS software. The input parameters of the model are day of year and location of the station. The testing results show that the tropspheric delay error can be reduce about 2 to 3 times compared to Saastamoinen model with standard meteorological parameters, and the effect is more remarkable when the height difference of two stations is large.


Chen B.,Central South University | Chen B.,Key Laboratory of Precise Engineering Surveying and Deformation Disaster Monitoring of Hunan Province | Dai W.,Central South University | Dai W.,Key Laboratory of Precise Engineering Surveying and Deformation Disaster Monitoring of Hunan Province | And 4 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2012

The electron density values of one day in Hong Kong obtained by ionospheric tomographic are divided into 6 groups. Then, the 6 groups data are fitted modeling and forecasting by neural network method. The results show that the accuracy of electron density value forecasted by the tomographic and neural network model is significantly higher than the electron density value provided by IRI2007 model. The precision of the electron density forecast value within 30 minutes and 60 minutes can respectively arrive at 0.45 TECU and 1.34 TECU.


Luo F.,Central South University | Luo F.,Key Laboratory of Precise Engineering Surveying and Deformation Disaster Monitoring of Hunan Province | Dai W.,Central South University | Dai W.,Key Laboratory of Precise Engineering Surveying and Deformation Disaster Monitoring of Hunan Province | And 6 more authors.
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2012

Multipath error is a main influence on high-precision GPS dynamic deformation monitoring results as it is difficult to be mitigated by difference observation in most of applications. A method called EMD-ICA with reference signal is proposed. It combines empirical mode decomposition (EMD) with independent component analysis (ICA). The test shows the effectiveness of this method.


Luo F.,Central South University | Luo F.,Key Laboratory of Precise Engineering Surveying and Deformation Disaster Monitoring of Hunan Province | Dai W.,Central South University | Dai W.,Key Laboratory of Precise Engineering Surveying and Deformation Disaster Monitoring of Hunan Province | And 2 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2012

The EMD filtering method based on the cross-validation is developed and applied to the study on GPS multipath effects. Experiments with both simulated data and real GPS observations show that the method can select the signals in the IMFs, reduce random error and separate noise from signals adaptively. Using this method to extract and model the correction of Multipath error can weaken the effects of Multipath, and then improve the accuracy of GPS surveying in dynamic deformation monitoring.


Dai W.,Central South University | Dai W.,Key Laboratory of Precise Engineering Surveying and Deformation Disaster Monitoring of Hunan Province | Wu X.,Central South University | Wu X.,Key Laboratory of Precise Engineering Surveying and Deformation Disaster Monitoring of Hunan Province | And 2 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2012

In the high-precision positioning with GPS, when the environment of the surveying point keep little changed, the multipath effect has strong repeatability. With this characteristic establishing the error correction model is an effective method to weaken the multipath effect influence. But as the time interval goes on, its repeatability decreases, and the corresponding effectiveness of this method drastically reduces. Therefore, based on augmented parameters Kalman filtering this paper proposes a multipath effect system error estimation method with state matrix augmentation, taking the systematic errors as state parameters and establishing AR model of first class, meanwhile using multipath repeatability characteristics to update multipath error correction model. With this method, the problem of that as the time goes on the repeatability decrease and the corresponding effectiveness of fix multipath error correction model reduces has been resolved to a certain extent. Finally, an example with 16 days GPS observation data has proved that this method has a certain feasibility and effectiveness.

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