GEOMETRIC ANALYSIS OF A SPACE GRID STRUCTURE BY AN INTEGRATED 3D SURVEY APPROACH

Abstract. The survey and modeling of spatial grid structures is often a challenging task to solve, due to the many bottlenecks present in the reverse modelling process. Geometrical and material complexity, scale variation, shadows effects, low accessibility, mismatch between similar elements, metrical validation, data management are all critical passages. They must be solved to obtain a reliable data able to solve the system maintenance and intervention requirements. In these cases, in particular, when the structure is difficult to be accessed, it is essential to plan an integrated survey approach. This paper shows how the survey and modelling of an impressive structure was carried out using both TLS and RPAS photogrammetry. After being validated, the data is integrated into a single point cloud that completely describes the structure, eliminating shadow areas and hidden parts. In the modeling process, particular attention was paid to verifying the correspondence between as-built and project. Finally, an element of particular interest is represented by the attempt to recognize the individual construction components belonging to specified geometric and dimensional classes, with the advantage of obtaining a complete model that is as faithful as possible to the real situation of the structure.