Analysis of the displacements of pipeline overpasses based on geodetic monitoring results

There are many approaches to address geospatial monitoring of pipeline overpasses, among which the most widespread methods are terrestrial laser scanning and total station measurements. However, there is a problem in comparing the geospatial monitoring data collected by different methods in different epochs. The main task of this work is to find the correspondence between points in different epochs. The total station measurements are carried out in specific discrete points of the pipeline overpass. In contrast, terrestrial laser scanning allows the collection of the whole data set without fixing specific point coordinates. In order to compare different data in different epochs, it is necessary to select a relevant presentation of the monitoring results (reference model) and specify appropriate criteria for quality inspection. In general, a pipeline can be presented as a spatial curve. In this study, two types of reference models are considered: cubic splines and Bezier curves. These models are examined for the monitoring of two gas pipeline overpasses. The first measurement epoch is accomplished by the terrestrial laser scanning, and the second measurement epoch is completed by the total station. The reference models are simulated by Matlab coding. The preliminary accuracy of ground laser scanning and total station measurement is selected as the criterion of quality inspection. The simulation and comparison results provide the evidence that the correct selection of reference model is a crucial component of successful geospatial monitoring. The results show that the Hermite splines are effective in the comparison of different data sets. These splines present the interpolation accuracy compatible with measurement accuracy, i.e., 15–20 mm for spatial displacement determination.