Analyzing the deformations of a bridge using GPS and levelling data

The aim of this study is analysing 1D (in vertical) and 3D movements of a highway viaduct, which crosses over a lake, using GPS and levelling measurement data separately and their combination as well. The data are acquired from the measurement campaigns which include GPS sessions and precise levelling measurements, performed with six-month intervals for two years. In 1D analysis of the (vertical) deformations, the height differences derived from GPS and levelling data were evaluated. While combining the height-difference sets (GPS derived and levelling derived) in the third stage of 1D analysis, Variance Component Estimation (VCE) techniques according to Helmert's approach and Rao's Minimum Norm Quadratic Unbiased Estimation (MINQUE) approach have been used. In 3D analysis of the deformations with only GPS data classical S-transformation method was employed. The theoretical aspects of each method that was used in the data analyses of this study are summarized. The analysis results of the deformation inspections of the highway viaduct are discussed and from the results, an optimal way of combining GPS data and levelling data to provide reliable inputs to deformation investigations is investigated in this study.