Quantifying tall structure tilting trend through TLS-based 3D parametric modelling

Geodetic monitoring of a tall structure means employing various methods of measurement and data processing for assessing its verticality. Terrestrial laser scanning (TLS) is a method of collecting lots of quality spatial data in a short time period. It enables detailed surface 3D parametric modelling. Advantages over the traditional cross-sectioning approach include direct obtaining of the structure axis inclination, analysing structure deformations relative to the modelled surface, and so forth. The subject of research was 52-metretall cylinder-shaped bell tower of St. Anthony of Padua Church in Belgrade, Serbia, which has been inclined since its completion in 1962. An original algorithm was developed for estimating parameters of a cylinder approximating the tower surface and their precision. The horizontal displacement of the cylinder top base centre ranging from 1.174 m to 1.196 m over the five-year period of geodetic monitoring of the tower indicates the clear existence of the structure tilting trend.