REAL-TIME BRIDGE DEFLECTION AND VIBRATION MONITORING USING AN INTEGRATED GPS/ACCELEROMETER/PSEUDOLITE SYSTEM

GPS is used for various structural deformation monitoring, both for long-term deformations as well as instantaneous deflections. Due to the inherent deficiency in the GPS satellite geometry, multipath, residual tropospheric delay and cycle slips, GPS alone cannot provide the required positioning precision all the time to meet the requirements for such a system to detect subtle deformations of structures. The Integration of a triaxial accelerometer with the GPS could significantly increase the measurement production and improve the overall system reliability and performance. However, measurements from an accelerometer can only bridge short period positioning gaps caused by the GPS signal outrage. Also, a triaxial accelerometer cannot help the vertical precision improvement, which is normally two to three times worse than the plane precision as claimed. In this paper, the authors explore the feasibility of introducing pseudolites or Galileo satellites into a previously developed hybrid bridge deformation system consisting of dual frequency GPS receivers and triaxial accelerometers. Data processing is conducted with the real deformation data gathered from two bridge trials to investigate the GPS satellite geometry and its impact on the precise engineering applications. Results from GPS satellite augmented system by pseudolites/Galileo are compared using the simulated data and real GPS/pseudolite based deformation monitoring data. It demonstrates that with such a system, millimeter 3D positioning precision can be maintained for the continuous deformation monitoring.