Key Laboratory of Modern Engineering Surveying

Shanghai, China

Key Laboratory of Modern Engineering Surveying

Shanghai, China

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Li H.,Tongji University | Chen J.,German Research Center for Geosciences | Wang J.,Tongji University | Wang J.,Key Laboratory of Modern Engineering Surveying | And 4 more authors.
Advances in Space Research | Year: 2010

Network based real-time precise point positioning system includes two stages, i.e. real-time estimation of satellite clocks based on a reference network and real-time precise point positioning thereafter. In this paper, a satellite- and epoch-differenced approach, adopted from what is introduced by Han et al. (2001), is presented for the determination of satellite clocks and for the precise point positioning. One important refinement of our approach is the implementation of the robust clock estimation. A prototype software system is developed, and data from the European Reference Frame Permanent Network on September 19, 2009 is used to evaluate the approach. Results show that our approach is 3 times and 90 times faster than the epoch-difference approach and the zero-difference approach, respectively, which demonstrates a significant improvement in the computation efficiency. The RMS of the estimated clocks is at the level of 0.1 ns (3 cm) compared to the IGS final clocks. The clocks estimates are then applied to the precise point positioning in both kinematic and static mode. In static mode, the 2-h estimated coordinates have a mean accuracy of 3.08, 5.79, 6.32 cm in the North, East and Up directions. In kinematic mode, the mean kinematic coordinates accuracy is of 4.63, 5.82, 9.20 cm. © 2010 Elsevier Ltd. All rights reserved.


Li H.-J.,Tongji University | Wang J.-X.,Tongji University | Wang J.-X.,Key Laboratory of Modern Engineering Surveying | Chen J.-P.,German Research Center for Geosciences | And 3 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2010

Based on the regional GNSS (Global Navigation Satellite System) network, the realtime epoch-differenced values of relative clock are estimated using the algorithm of epochdifferential and satellite-differential derived model. On account of the character of precise realtime clocks, the estimation model of real-time precise point positioning is deduced by a satellitedifferential algorithm. Comparing the epoch-differenced values of relative clock and the IGS final products, the accuracy can be at 0. 08 ns. The hourly data was processed using the real-time precise point positioning algorithm based on the estimated real-time precise clocks. In static mode, the hourly positioning accuracy in the N, E and U directions are 1. 47,3. 62,4. 09 cm respectively. The kinematic positioning accuracy in the N,E and U directions are 2. 63,3. 82,5. 20 cm respectively. The accuracy of real-time solution is better than the precise point positioning using the IGS final orbits and clocks in the N, E and U three directions.


Ge X.,Tongji University | Wu J.,Tongji University | Wu J.,Key Laboratory of Modern Engineering Surveying
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2013

Based on the objective measurement accuracy, we attempt to use the residuals of measurements in both design matrix and observation value to replace the positive constant. A few numerical experiments are carried out to demonstrate the performance and efficiency of the new method.


Ge X.,Tongji University | Wu J.,Tongji University | Wu J.,Key Laboratory of Modern Engineering Surveying
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2012

Total least squares method is a deregularizing procedure, so the ill-posed problems will be more serious. That means errors in the data are more likely to affect the total least squares solution than the least squares solution. It is proposed using generalized regularization to solve ill-posed problems in total least squares, so as to improve stability of the results. Finally, numerical experiments are carried out to demonstrate the performance and efficiency of the generalized regularization method which have significant advantages in solving ill-posed problems.


Wang C.,Tongji University | Wang J.,Tongji University | Wang J.,Key Laboratory of Modern Engineering Surveying | He L.,Tongji University
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2012

A real time cycle slip detection method is proposed based on Jarque-Bera test for testing the normality of slip parameter in epoch window, which constructed by bi-differences of pseudo range and carrier phase observations. Real time cycle slip detection tests are analyzed with GPS static observation data and on-board GPS dynamic data. The results indicate that the algorithm can detect outliers in real time, and provide the base of data quality controlling for real time precision orbit determination and positioning.


Ge X.,Tongji University | Wu J.,Tongji University | Wu J.,Key Laboratory of Modern Engineering Surveying
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2012

According to the traditional approach of three-dimensional datum transformation and classic least-squares (LS) theory, the weight constraint total LS (WCTLS) and mixed LS are introduced. A more reasonable model and the corresponding iterative algorithm are given. The example results show that the new model is more reasonable indeed and the more accurate parameters of datum transformation can be obtained with suitable weight assigned.


Li H.,Tongji University | Wang J.,Tongji University | Wang J.,Key Laboratory of Modern Engineering Surveying | Wang H.,Tongji University | Li B.,Tongji University
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2010

The reference epoch based relative clock was estimated using the method of epoch-difference and satellite-difference. An experiment is carried out using the data of different sampling rates collected from Hong Kong and Shanghai GNSS reference networks, in order to study the influences of region and sampling rates to the accuracy. The results show that the difference between our results and IGS final precise clock error products is less than 0.2 ns, and the accuracy of the reference epoch based relative clock is less than 0.9 ns. The accuracy is at the same level in different regions, and the influence of sampling rate is very small.


Xie Y.,Tongji University | Xie Y.,Chinese Academy of Sciences | Chen J.,Chinese Academy of Sciences | Wu J.,Tongji University | And 2 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2014

Based on different constraints, double-frequency measurement data from 11 GPS stations in the vicinity of China and 230 global GPS stations were used to calculate vertical ionosphere electron content(VTEC), the DCB of GPS satellites, and corresponding receivers based on the spherical harmonic function model. The results show that the VTEC and the combination DCB of GPS satellite and receiver were not affected by constraints. The DCB precision of the combination obtained is less than 2 ns comparing with CODE, and the correction rate of VTEC relative to CODE can reach up to 90 percent. We also predict spherical harmonic coefficients using the AR model; the correction rate of VTEC based on the prediction coefficients can reach to 80 percent; thus fixing the sum of the satellite DCBs is better than fixing a single satellite DCB.


Xie Y.,Tongji University | Xie Y.,Chinese Academy of Sciences | Wu J.,Tongji University | Wu J.,Key Laboratory of Modern Engineering Surveying | And 2 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2014

According to the requirements of high precision satellite navigation and ionosphere activity monitoring, double-frequency measurement data from 238 IGS stations are used to calculate vertical ionosphere electron content (VTEC), DCB of GPS, GLONASS and the corresponding receiver based on the spherical harmonic function model. The results show that this implemented model is reliable. The DCB precision of GPS and GLONASS obtained is less than 0.1 ns when compared with the results of CODE and less than 0.2 ns when compared with that of IGS. The DCB precision of GPS and GLONASS receivers are less than that 2 ns, while the precision of VTEC is better than 3 TECU in comparison with that of CODE and IGS, and better than before combination.


Wang H.,Tongji University | Wang J.-X.,Tongji University | Wang J.-X.,Key Laboratory of Modern Engineering Surveying | Bai G.-X.,Key Laboratory of Modern Engineering Surveying | And 3 more authors.
Chinese Journal of Geophysics (Acta Geophysica Sinica) | Year: 2011

The longest total solar eclipse during the 21st century occurred in the morning of 22 July 2009. The Yangtze River Valley of Central China is located on the central line of the total eclipse belt. It will provide a unique opportunity to investigate the influence of the total solar eclipse on the ionosphere. This paper describes a method of real-time solving TEC and GPS instrumental bias using Kalman filtering, so this can be used to provide absolute amount of ionospheric TEC for real-time monitoring of ionosphere changes during the total solar eclipse. For validation of this method, the data of Shanghai and Zhejiang regional GPS network are used and a real-time regional ionosphere model is created, then real-time VTEC and TEC ratio are also calculated. Meanwhile, with consideration of the solar and geomagnetic parameter, the ionospheric anomalies with phenomenon of TEC changes in the Yangtze River Delta region during the total solar eclipse are analyzed in detail and discussed by adopting the numerical computations.

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