Classification of surface geometry behavior of cultural heritage surfaces based on monitoring change

Efficient monitoring of large-scale cultural heritage monuments is of great interest in understanding alteration mechanisms that lead to substantial decision making for safeguarding them. This work presents a methodological approach for monitoring areas of the wall of King Jan III’ palace Wilanów (Poland), where due to weathering the documentation of the surface changes became indispensable. Data from 3D scanning and registered data, representing different time intervals, were analysed to determine surface geometry changes. The goal was to develop a methodology which could detect each surface point based on grouping it with similar behaviour of local geometry changes. Further analyses, to determine the direction of change and the local geometry, were performed with the goal to extract information on the behaviour of changes and quantify them. By assigning a gradual scale, for the calculated displacement information regarding alterations can be visualized and measured. The methodology was based on calculating initially the general direction of change and then analysing the local geometry changes based on considering neighbouring points obtained from the spherical search kernel of each surface point. The neighbouring points were then compared to weathered dataset point cloud, by calculating the Euclidean distance and data segmentation, based on histograms of local distance analysis, was produced. Each histogram was fitted to the kernel distribution curve and bandwidth parameters, with similar points, were identified and segmented for changes corresponding to different time intervals. Initial evaluation on the case study shows the ability of the proposed methodology to detect even minor surface displacements.