Reliable Dynamic Monitoring of Bridges with Integrated GPS and BeiDou

: GPS (Global Positioning System) in recent years has been widely used for the measurement of deflections of bridges. However, due to multipath and satellite signal obstructions, caused by towers, cables and passing vehicles, the reliability of deformation monitoring with GPS is still a problem. Recent research with respect to multi-GNSS (Global Navigation Satellite System) technology, though, have proved to enhance satellite visibility and availability for positioning, navigation and timing (PNT) for users. Its benefits involving application in bridge monitoring are still rarely studied. In this paper, we propose a composite strategy where integrated GPS and BDS (BeiDou Navigation Satellite System) dual-frequency carrier phase data processing is carried out to improve the reliability of bridge monitoring with GNSS measurements. In addition, SNR (signal-to-noise ratio) based stochastic model and post-fit residual editing strategies are utilized to enhance the reliability further. In a group of fixed point experiments, improvements of 20% to 30% in precision were achieved with the integrated GPS and BDS compared to GPS-only results. Based on the real GPS and BDS measurements collected on the Baishazhou Yangtze River Bridge in China, we assessed the performance of the proposed method. In the vibration experiment, no apparent effects on natural frequencies identification were found by introducing BDS into the solution at ideal observation environment. However, the combined GPS and BDS results seem to be much more promising, with lower background noise. Meanwhile, the integrated GPS and BDS data processing with post-fit residual editing and SNR-based stochastic model strategies can effectively deal with satellite signal obstruction and the influence of multipath effect to attain reliable dynamic deformation monitoring information for bridges.