Surveying cultural heritage

The structured light scanner was uses to acquire highly detailed 3D models of rocks and chisel marks were acquired with a structured light scanner. The 3D models of the rocks shall be used to determine the original position from where they might have fallen down and the models of the chisel marks to obtain information about how many stone masons might have worked on a tomb. Furthermore, the structured light scanner was used to acquire 3D information of mummy parts, ceramics, and other objects. Their 3D models allow measuring distances at the computer without having the need of direct access to the object at a later stage. By changing the illumination of the models, also small features emerge and may deliver new information.

The project in Rome was carried out in cooperation with the German Archeological Institute between 2007 and 2010. The main tasks included the realization of reference frames at various locations, the generation of a DTM of Colle Opio as well as the creation of 3D models of different objects of interest. These included the Patheon, the Colosseo, Forum Romanum and the Domus Aurea.

From the geodetic viewpoint GNSS Signal availability, multipath effects and the multitude of different and inconsistent reference frames posed a challenge.

As part of the joint research project "Anden Transekt" coordinated by the German Archeological Institute two different archeological sites in the Peruvian Andes had to be surveyed. This task was tackled using both UAV-photogrammetry as well as long range laserscanning leading to material allowing for the direct comparison of both methods in terms of suitability for the task at hand, operability and precision of the derived DTMs. The two sites "Santa Maria" and "Cutamalla" featured different challenges: the altitude of the location, vegetation, segmentation of the landscape by terraces and differing atmospheric conditions were just some of them. The image below shows some impressions of the measurement setups.

Terrestrial Long Range Laser Scanners use a LiDAR based method and as such is able to generate 3D models of objects by measuring spherical coordinates, i.e. two angles and one radius which is derived via the time of flight between the static instrument and the object of interest. A single acquisition leads to a point cloud representing the surfaces facing the scanner. The resolution decreases quadratically with the distance. A Riegl VZ- 100 was augmented with a digital camera for later colouring of the point clouds used during this project leading to a precision of around 8 mm at 100 m and maximal radii of 1400m.

Unmanned Aerial Vehicles operate differently; by taking images of the objects of interest while hovering up to 150 m above the ground level a data set is generated that can be used to derive a DTM in later processing steps. These typically include Image orientation and camera calibration as well as dense matching. The DTMs generated by both methods can be seen in the image below.