Monitoring Heritage 2018 - International Summer School
There are many constraints in analyzing historic masonry buildings today, particularly regarding invasive techniques that could severely affect the heritage structure or surface. However, there are a number of non-destructive techniques to get a better understanding of their structure, surface or interior.
Groundpenetrating Radar (GPR)
GPR is probably the most versatile geophysical instrument applied in archaeological prospection. In the process, transmitted electromagnetic waves are reflected by layer boundaries which, as a sum, provide a profile of the background. This enables a 3-dimensional mapping of foundations and other archaeological traces, as well as a detailed structural analysis of buildings.
Micro Seismic Analysis
On the basis of traditional seismic equipment small local tremors from passing traffic or construction sites can provide information on the interior structure of masonry buildings. Developed in structural engineering, the technique measures shear and compressional wave velocities to model the elastic properties of a building.
Terrestrial 3D Laser Scanning/3D Scanning
Through a vertically spinning mirror and simultaneously horizontally rotating scan head 3D measurements around the terrestrial laser scanner (TLS) position are collected. As well as highly accurate 3D data the laser scanner captures a scene with colour information with an onboard camera. This makes the TLS ideal for capturing large objects, interiors, whole buildings and cityscapes.
Structure from Motion
Structure from Motion (SfM) uses the principle that movement through a scene allows an understanding of the shape of the scene in three dimensions. Images can be captured from the ground or by using drones or UAVs (Unmanned Aerial Vehicles). SfM requires at least 3 images of each part of the object. Specialised software automatically selects distinctive points in the photographs, and thousands of these points are matched together. The result is a detailed metric and coloured dataset that is similar to the 3D point clouds produced by laser scanning.
Structured Light Scanning
Structured Light scanning is used for objects up to ca 3 metres. The sensor used for the summer school enables the operator to freely walk around the object. It is a high-resolution 3D scanner based on blue light technology, structured light projection, and real-time alignment during scanning. It captures surface detail with a resolution of about a tenth of a millimetre.