Abstract
The Single-frequency Single-epoch double-differenced baseline resolution technique of Global Positioning System (GPS) provides a good opportunity for monitoring the displacement or deflection behavior of bridges under different loading conditions in real-time. However, for single GPS, a high success rate baseline solution is difficult to achieve due to the lack of sufficient visible satellites and the low accuracy of float solutions. Galileo Satellite Navigation System (Galileo) has 14 medium earth orbit satellites (as of May 2018) that can be used to supplement GPS. The frequency bands of Galileo overlap with that of GPS on E1/L1 and E5a/L5, which is conducive to the combination of observations in integration positioning. Accordingly, Galileo augmenting GPS is an effective and necessary approach to improve the positioning availability and reliability. Moreover, using the baseline length constraint can improve the accuracy of float solutions, narrow the search space, and finally increase the success rate of ambiguity resolution and positioning. The single-frequency single-epoch double-differenced GPS/Galileo mathematical model with baseline length constraint is deduced in this paper. Two sets of GNSS real bridge data were used for further analysis on the improvement of GPS/Galileo with baseline length constraint when compared to single GPS. Finally, a Fast Fourier Transformation (FFT) algorithm was adopted for precisely detecting the local dominant frequencies of XB, YB, and ZB direction of the two stations.
Highlights
The global positioning system (GPS) technology exhibits several advantages, such as easy to obtain absolute position solution, weather independence, autonomous operation, and not requiring a line-of-sight between target points [1]
Psimoulis et al found that GPS is suitable in the identification of dynamic characteristics of even relatively rigid civil engineering structures that are excited by various loads if the displacements are less than the uncertainty level of the method [5]
Efforts have been made in recent years in the use of an integrated monitoring system that consists of dual frequency GPS or Global Navigation Satellite System (GNSS) receivers and triaxial accelerometers for the detection of the dynamics of long span road bridges [6,7]
Summary
The global positioning system (GPS) technology exhibits several advantages, such as easy to obtain absolute position solution, weather independence, autonomous operation, and not requiring a line-of-sight between target points [1]. The performance of several precise point positioning (PPP) models, combining dual-frequency GPS/Galileo observations in the un-differenced and between-satellite single-difference (BSSD) modes, was compared. This section mainly discusses the SFSE double-differenced mathematical models for integrated GPS/Galileo relative positioning, including the non-differenced and double-differenced code and phase observation equations for single system and DD equations for integrated systems with different combination strategies with/without DISBs. the baseline length constraint model and the corresponding stochastic model are deduced. Λj · ∇∆φb1rG,j,e = ∇∆ρ1brG,e + λj · ∇∆Nb1rG,j,e + ∇∆δb1rG,j,e + ∇∆ ∈1brG,j,e where ∇∆d1brG,j,e and ∇∆δb1rG,j,e denote the code and phase DISBs between the overlapping frequency observations of GPS and Galileo, respectively. This means that one additional Galileo observation will be preserved as valuable measurement information if the combination of GPS/Galileo TCL was used
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