Characterizing deformation of Istambul wall by geodetic terrestrial laser scanner

Abstract

Historical buildings are an integral element of human civilization and they play a big part in cultural heritages for the descendants. Turkey, as being the cradle of civilizations, hosts very important and valuable structures. These structures are exposed to deformations for various reasons. Classical geodetic monitoring is a key approach for years to detect the deformation behaviors of structures. However, with the advanced technology, modern geodetic instruments replaced the classical geodetic instruments. Terrestrial Laser Scanner is built on the approach of acquiring a high-density point clouds, which represents X, Y, Z coordinates of the reflective surface. The case of Istanbul Land Walls has been chosen for this study due to its ~1600 years of historical value. In particular, two different towers of Land Walls having huge cracks on the front side of both structures is the motivation of this study. During this study, it happened an earthquake in Silivri offshore with the local magnitude (ML) of 5.8. Thus, there are 2 observations before and after the earthquake. In total, three independent measurements are made. Data obtained from scanning were compared in Cyclone 3DR software using Cloud-to-Cloud method of deformation analysis. Geometries of structures are defined with outputs found by point clouds; deformation progresses are scrutinized, and three-dimensional models are constituted. In conclusion, Terrestrial Laser Scanning technology is convenient to detect the deformations of historical structures with high capacity point clouds. The deformation maps obtained from comparing the point cloud data give a good structural information about the object by showing the current deformations and highlighting zones with possible future damage. It is thought that this study may provide a significant contribution to literature about not only protecting cultural heritage but also deformation studies.