This year’s introductions to techniques include:
- ground-penetrating radar (GPR) to investigate and visualise subsurface and interior structures.
- structure from motion (SfM) & structured light scanning to visualise objects
- 3D terrestrial laser scanning (TLS) & drone photogrammetry (SfM) for recording architecture
- Visualizing and interpreting LiDAR imagery of the surrounding landscape
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.
The smallest disturbances of the earth's magnetic field can be detected by magnetometers. The applied probes measure these variations, e.g. be caused by scrap iron, material burned under great heat, or by magnetotactic bacteria in order to create a 2-dimensional map of the magnetic disturbances, to draw conclusions about the cultural use of a landscape.
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/ drone photogrammetry
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.
LiDAR (Light Detection and Ranging)
In order to analyze the collected data sets in terms of the castles cultural history and geographic environment, LiDAR (Light Detection and Ranging) data will serve to generate and visualize a digital terrain model, to compare and interpret it with visible structures in the field.