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Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Deformation monitoring is an important guarantee for the safe operation of water conservancy projects. With the advantages of high precision, all-day and all-climate observation, global satellite navigation system (GNSS) provides new means for deformation monitoring in hydraulic engineering. At present, the deformation monitoring technologies represented by satellite positioning is approaching intelligent development in all processes, all aspects, and all autonomous. Firstly, we focus on the demand of deformation monitoring of water conservancy projects, and review the development of deformation monitoring technology. Then， the application of GNSS deformation monitoring in hydraulic engineering is introduced. Besides, the difficulties and limitations of GNSS deformation monitoring application are discussed. Finally, the development direction of intelligent GNSS deformation monitoring in hydraulic engineering in the future is prospected. [ABSTRACT FROM AUTHOR]

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The long-term accumulated coordinate time series of Global Navigation Satellite System (GNSS) reference stations provide basic data for geodesy and geodynamic studies. Through improving precise GNSS data processing models and strategies, together with investigating physical mechanism and properly modeling of the non-linear variations, the precise position and velocity of GNSS stations can be estimated. This will not only help interpret the plate tectonics reasonably, establish and maintain the terrestrial reference frame, but also contribute to investigating the geodynamic processes, such as post-glacial rebound, sea level change, as well as snow and ice redistribution inversion, et al. In this paper, the basic theory and methodology of GNSS coordinate time series analysis is reviewed by introducing the model estimation of station coordinates time series and the signal analysis. Then, noise modeling technique for GNSS coordinate time series is outlined. Particularly, a rigorous 3-D noise modeling method is proposed to best describe the stochastic process. After that, the advances in investigating physical mechanism of the non-linear variations in GNSS coordinate time series are summarized. Finally, we outline the scientific and engineering applications of GNSS coordinate time series, and discuss the prospect of future research. [ABSTRACT FROM AUTHOR]

This paper firstly compares and analyzes the effect of maximum like lihood estimation (MLE) and least square variance estimation (LS-VCE) and minimum norm quadratic unbiased estimation (MINQUE) in the variance component estimation of GPS coordinate time series noise. After determining the minimum norm of two unbiased estimation method for the optimal estimation of noise variance, the correlations between the noises in each direction are analyzed by means of unitary linear regression, and the linear regression equations are determined.Experimental results show that, compared with the least squares variance component estimation method and maximum likelihood estimation method, MINQUE has a better estimation effect for the noise variances of GPS coordinate time series. In addition, the influence of noise on the estimation of motion parameters of the station can be reduced by using long span time series. Moreover, the same kind of noise in GPS coordinate time series of each direction has more significant correlation and the correlation between flicker noise in north and other directional flicker noises are better than that of white noises. The 40%-60% of the variance of the vertical noise can be explained by the noise variance in the horizontal direction, and north noise variance can explain the 60%-80% of change of the noise variance in east. The obtained linear regression equation has practical value. [ABSTRACT FROM AUTHOR]

Wavelet spectral analysis is employed in this paper to determine the frequency components and their variations over time in coordinating time series of IGS stations in China. Then least-squares variance component estimation (LS-VCE) is adopted to analyze motion characteristics of stations in China in different periods under the assumed model of white and flicker noise. The results indicate that motion characteristics of IGS station in China are seasonally varied in different periods. The variation of the vertical velocity of URUM station is greater than 4 mm, while velocity changes more than 2 mm for horizontal component of BJFS and CHAN. And the rest are no more than 2 mm. There are also differences in the amplitude of the annual and semi-annual signals. Among them, BJFS has the largest change in vertical component, which is more than 5 mm; In addition, weaker periodic items are discovered in some segment of the time series. Though, due to their little impact on the result of parameter estimation, they are discarded along the process. Moreover, the fact that the estimations of the parameters for one station are not consistent in different segments of the time series may reflect patterns of geophysical effects on certain stations over time such as plate motion. [ABSTRACT FROM AUTHOR]

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geomatics & Information Science of Wuhan University is the property of Geomatics & Information Science of Wuhan University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Using ionosphere TEC data provided by IGS for the years 2000 to 2012, we studied ionosphere TEC asymmetry between the southern and northern hemispheres. By analyzing the Asymmetry Index (AI) of the TEC daily mean between the southern and northern hemispheres, we found that the absolute value of the maximum concentration of AI was about 0.4, the absolute value of the minimum concentration was about 0.3, demonstrating that there is a numerical asymmetry in the ionosphere TEC between the southern and northern hemispheres. With the Fourier analysis method, we found that there is an annual cycle and a 1/3 annual cycle existing in Asymmetry Index; more than 50% when the northern hemisphere ionospheric TEC exceeds the southern hemisphere ionospheric TEC in a year. The mean value was 58%, suggesting a temporal asymmetry of the ionosphere TEC between the southern and northern hemispheres. We analyzed the annua difference of the mean TEC between the southern and northern hemispheres, finding that the annual mean TEC of the northern hemisphere is higher than that of the southern hemisphere, and the Asymmetry Index of the annual mean TEC between the southern and northern hemispheres during 2000-2012 was about 0.036. Taking the asymmetry in the atmospheric distribution and the movement rule and thermosphere into consideration, we discuss the reasons for the asymmetry of the ionosphere TEC between the southern and northern hemispheres. [ABSTRACT FROM AUTHOR]

In this paper, we analysed the seismo-ionospheric anomalies of the vertical total electron content extracted from a global ionosphere map during the Lushan earthquake by adopting a quartile-based method. To confirm whether the ionospheric anomalies associated with the earthquake, VTEC gradients in the eastward and northward directions near the epicenter were further examined, and VTEC data during the same period in 2008-2012 were cross-compared. The results show that the negative anomalies during 18 to 20 April are probably caused by Lushan earthquake. Analysis of equatorial anomaly near epicenter shows that the crests significantly decreased five days before the earthquake, and moved to magnetic equator. Combining ionospheric negative anomalies with the modification of the equatorial anomaly, we find that the anomalous electric field generated in the earthquake preparation might be a main cause of the observed ionospheric anomalies. [ABSTRACT FROM AUTHOR]