Excavation-parallel laser scanning of a medieval cesspit in the archaeological zone cologne, germany

Abstract

During the construction of an underground museum in the historic city center of Cologne, Germany, large parts of the Roman and medieval city are being excavated. The newly excavated remains as well as remains of the Roman city, which had already been excavated in 1954, exhibit structural damages. While at first deficiencies in the construction were assumed to be the cause of the damages, in 2003 a seismogenic origin was suggested. To further test this hypothesis of seismically induced slope movements and other possible causes, a multidisciplinary project was started. One step in this project is the documentation of the damages using a 3D laser scanner, followed by a quantitative damage analysis. This article presents the 3D documentation and the quantitative damage analysis of a recently excavated medieval cesspit. The 8.3m-deep cesspit was mapped during 11 campaigns using a phase-based 3D laser scanner. Due to the static conditions of the cesspit, the structure could not be excavated in its entirety. After the excavation of every 1-2m-section, restoration work had to be done to avoid a collapse of the construction. The laser scanning technique offered the possibility of working parallel to the excavation so the original conditions of each section could be documented before the restoration. The resulting models were used to identify, classify, and quantify the structural damages of the cesspit.

A high resolution laser scanning model of the Roman theater in Pinara, Turkey – comparison to previous measurements and search for the causes of damage

“…This setting gave the audience a breathtaking view rising to the 80 m high cliff and the upper castle. The structure is typical for Roman theaters of that period in Asia Minor and largely follows the common rules given later in the first century BC by Marcus Vitruvius Pollio [15]. The auditorium, cavea, covers more than a half circle so that the side walls, analemma, form an obtuse angle (Figs.…”

“…In order to obtain a clear view of the seating rows, the cavea was cleared of most of the vegetation growing between the seating rows, particularly in the southern section. Previous scanning campaigns [15] showed that the use of targets or spheres did not significantly improve the overall registration error when combining point clouds compared to the target-less registration technique and application of least square algorithm. Based on this experience, no targets were used in the survey of the theatre.…”

Archeoseismic study of damage in Roman and Medieval structures in the center of Cologne, Germany

“…We used the laser scanning technique to create a comprehensive virtual model (CVM) of the remains of the whole excavation complex (Schreiber et al 2009(Schreiber et al , 2012Schreiber and Hinzen 2011). In full resolution, the CVM contains 2.3 billion georeferenced 3D points.…”

“…In full resolution, the CVM contains 2.3 billion georeferenced 3D points. Special challenges included the repeated scanning of the 8.3 m deep cesspit during its excavation (Schreiber et al 2012) and the 13 m deep Roman well (Fleischer et al 2010). The CVM enhances visualization and quantification of the damage found in the study area, which were previously described (i.e., Doppelfeld 1956;Precht 1973;Hinzen and Schütte 2003), as well as damage described here for the first time in their archeoseismological context.…”

“…The 8.3 m deep cesspit built from 60 to 70 layers of small to medium tuff blocks was statically unstable and the walls had to be stabilized and reconstructed successively when the fill was removed. Schreiber et al (2012) describe in detail the scanning procedure and implementation of the cesspit in the CVM. At a depth between 49 and 47 masl, the walls of the cesspit are heavily deformed and damaged.…”