For the sake of timely appraising the working con di tion of the bridge, measuring the dynamic characteristics of the bridge structur e is very important and necessary. A GPS dynamic monitoring test was carried out in...For the sake of timely appraising the working con di tion of the bridge, measuring the dynamic characteristics of the bridge structur e is very important and necessary. A GPS dynamic monitoring test was carried out in the Wuhan Baishazhou Bridge, which is one of the longest span cable-stayed bridges having been built in China. This paper introduces the experimental imple menting scheme and data processing method. The vibration characteristics of the middle span of cable-stayed bridge are availably obtained by use of the spectra l analytic approach. The measuring results are very identical to the theoretical designed values. The research demonstrates that, with GPS receiver of the high sampling rate and suitable data processing method, the vibration characteristics of the bridge structure can be determined with high accuracy.展开更多
The span of coordinate time series affects the determination of an optimal noise model. We analyzed position data recorded for 10 continuous Global Positioning System （GPS） sites from 1998.0 to mid-2009 on the Austr...The span of coordinate time series affects the determination of an optimal noise model. We analyzed position data recorded for 10 continuous Global Positioning System （GPS） sites from 1998.0 to mid-2009 on the Australian Plate to estimate the best noise model and thereafter obtain the true uncertainties of the velocity, employing the maximum likelihood estimation （MLE） method. MLE was employed to analyze the data in four ways. In the first two analyses, the noise was assumed to be a combination of flicker noise and white noise for the raw time series and spatially filtered time series. In the final two analyses, the spectral indices and amplitudes were simultaneously estimated for a power law noise plus white noise model for the raw time series and spatially filtered time series. We conclude that the noise model of GPS time series in Australia can be best described as the combination of flicker noise and white noise. Velocity uncertainties fall below -0.2 mm/yr when the time span exceeds -9.5 years. A comparison of noise amplitudes and maximum likelihood estimation values between the raw and spatially filtered time series suggests that traditional spatial filtering to remove common-mode errors might not be applicable to the raw time series of this region.展开更多
The global navigation satellite system(GNSS) has become an important space infrastructure. Following GPS and GLONASS, Europe and China have been building their own global navigation satellite system, respectively, GAL...The global navigation satellite system(GNSS) has become an important space infrastructure. Following GPS and GLONASS, Europe and China have been building their own global navigation satellite system, respectively, GALILEO and Compass. In order to consolidate the leadership of GPS in the globe, United States is gradually upgrading the traditional GPS. Simultaneously, Russia is also intensively restoring full performance of GLONASS. With the advancement of international satellite navigation system, satellite navigation frequency resources are already in short supply, and the design and use of the navigation signals are more sophisticated and complex due to commercial, disaster relief and other reasons. Since there may be many navigation signals in the same basic bandwidth, the coexistence of multiple systems and the combined application make intersystem mutual interference become the focus research. Under this background, the satellite navigation system mutual interference evaluation system needs to be established urgently to meet and support the compatibility and interoperability of the GNSS system. In the paper, through the performance analysis of the GNSS signal acquisition, carrier tracking, data demodulation and code tracking, the equivalent carrier to noise ratio model based on spectrum isolation coefficient is established, and the theoretical system of the GNSS signal mutual interference is proposed according to the mechanism, and the mutual interference of GPS, GALILEO and Compass system is analyzed and assessed.展开更多
文摘For the sake of timely appraising the working con di tion of the bridge, measuring the dynamic characteristics of the bridge structur e is very important and necessary. A GPS dynamic monitoring test was carried out in the Wuhan Baishazhou Bridge, which is one of the longest span cable-stayed bridges having been built in China. This paper introduces the experimental imple menting scheme and data processing method. The vibration characteristics of the middle span of cable-stayed bridge are availably obtained by use of the spectra l analytic approach. The measuring results are very identical to the theoretical designed values. The research demonstrates that, with GPS receiver of the high sampling rate and suitable data processing method, the vibration characteristics of the bridge structure can be determined with high accuracy.
基金supported by the National Natural Science Foundation of China(Grant Nos.41304007,41074022)the Chinese Universities Scientific Fund(Grant No.121103)+1 种基金the Surveying and Mapping Basic Research Program of the National Administration of Surveying,Mapping and Geoinformation(Grant No.11-02-02)the China Scholarship Council and College of Science of the University of Nevada,Reno
文摘The span of coordinate time series affects the determination of an optimal noise model. We analyzed position data recorded for 10 continuous Global Positioning System （GPS） sites from 1998.0 to mid-2009 on the Australian Plate to estimate the best noise model and thereafter obtain the true uncertainties of the velocity, employing the maximum likelihood estimation （MLE） method. MLE was employed to analyze the data in four ways. In the first two analyses, the noise was assumed to be a combination of flicker noise and white noise for the raw time series and spatially filtered time series. In the final two analyses, the spectral indices and amplitudes were simultaneously estimated for a power law noise plus white noise model for the raw time series and spatially filtered time series. We conclude that the noise model of GPS time series in Australia can be best described as the combination of flicker noise and white noise. Velocity uncertainties fall below -0.2 mm/yr when the time span exceeds -9.5 years. A comparison of noise amplitudes and maximum likelihood estimation values between the raw and spatially filtered time series suggests that traditional spatial filtering to remove common-mode errors might not be applicable to the raw time series of this region.
基金supported by the National Natural Science Foundation of China(Grant No.61203226)
文摘The global navigation satellite system(GNSS) has become an important space infrastructure. Following GPS and GLONASS, Europe and China have been building their own global navigation satellite system, respectively, GALILEO and Compass. In order to consolidate the leadership of GPS in the globe, United States is gradually upgrading the traditional GPS. Simultaneously, Russia is also intensively restoring full performance of GLONASS. With the advancement of international satellite navigation system, satellite navigation frequency resources are already in short supply, and the design and use of the navigation signals are more sophisticated and complex due to commercial, disaster relief and other reasons. Since there may be many navigation signals in the same basic bandwidth, the coexistence of multiple systems and the combined application make intersystem mutual interference become the focus research. Under this background, the satellite navigation system mutual interference evaluation system needs to be established urgently to meet and support the compatibility and interoperability of the GNSS system. In the paper, through the performance analysis of the GNSS signal acquisition, carrier tracking, data demodulation and code tracking, the equivalent carrier to noise ratio model based on spectrum isolation coefficient is established, and the theoretical system of the GNSS signal mutual interference is proposed according to the mechanism, and the mutual interference of GPS, GALILEO and Compass system is analyzed and assessed.
