Analysis of the geometry of the cultural heritage object from the terrestrial laser scanning data

摘要

On the selected case (the belfry in village Črni kal, Slovenia) the analysis of data about terrestial laserudscanning with a view to graphically and numerically determined nonverticality and other possible deformationsudof the belfry is carried out. Data acquired with a terrestrial laser scanner has been providedudby 3D ATA Ltd. Data analysis was conducted with a program Geomagic, and a program AutoCADudhas been used to draw horizontal planes. The point cloud was imported into the program GeomagicudStudio which was used for further analyzes. We carried out four methods of determination the geometryudof the belfry: we determined the parameters of planes outer walls of the belfry; we determined theudangle of inclination from the vertical (according to the line between the center of the apple and theudcenter of the lower plane and the angle of inclination from the vertical line to elevation levels); weuddetermined the horizontal planes at elevation levels (together 14 levels) and compare plan views of theudcorner points; we searched the fit of the belfry to different geometric shapes. In the first analysis weudhave found that the belfry inclines differently in different directions. In second analysis we have foundudthat the angle of inclination from the vertical line of the belfry is 2°52'51'' (according to the line betweenudthe center of the apple and the center of the lower plane) and overall angle of inclination fromudthe vertical line is 2°52'51'' (according to elevation levels). In the third analysis we have found that theudcorner points of the belfry of the selected horizontal planes according to plan view do not show displacement,udthe reason is in different lengths of the sides of the belfry. In fourth analysis we haveudsearched the fit of the points of the belfry to cylinder and cone/truncated cone. We compared the orientationudof shapes and normal of the planes with computed 2D distances. We have found that the deviationsudare great on the total height of the belfry on each shape.