Detection of geometric changes for an historic theatre by comparing surveying data of different chronological periods

This paper presents results from a study where identification and documentation of geometric changes are examined from a weathered ancient theatre using map regression methods. Specifically, a comparison is made between a topographic map created in the 1960s by the German Archaeological Institute and a new map of the same area using state-of-the-art geodetic and terrestrial laser scanning (TLS) techniques. The work scale of the maps is 1:100 and can reveal changes and deformations of relevant size to the scale of the map (over 1.5 cm). The process, described in detail, entails georeferencing, planimetric and vertical comparison and assessment of the changes. The study demonstrates the importance of detecting topographic changes in cultural heritage sites and can be applicable to similar analyses over a range of time periods.