Assessment of dynamic measurement accuracy of GPS in three directions

Global positioning system (GPS) technology is an emerging tool for measuring and monitoring both static and dynamic displacement responses of large civil engineering structures to gust winds. The accuracy of dynamic displacement measurement using GPS at a subcentimeter to millimeter level, however, depends on many factors such as data sampling rate, satellite coverage, atmospheric effect, multipath effect, and GPS data processing methods. This paper aims to assess the dynamic displacement measurement accuracy of GPS in three orthogonal directions for applications in civil engineering. For this purpose, a motion simulation table was first developed as a test station, simulating various types of 2D motions of either tall buildings in a horizontal plane or long-span bridges in a vertical plane. The antenna of a GPS receiver was then installed on the motion simulation table and was used to measure the table motion in an open area. A band-pass filtering scheme was finally designed and applied to the table motion data recorded by the GPs. The comparison of the table motion recorded by the GPS with the original motion generated by the table shows that the GPS can measure horizontal and vertical dynamic displacements accurately within a certain amplitude and frequency range. The test results also demonstrate that the GPS can trace wind-induced dynamic displacement responses measured from a tall building in the horizontal plane and a long-span bridge deck in the vertical plane satisfactorily.