Photogrammetric Documentation of Stone Surface Topography Changes as a Tool in Conservation Praxis

Abstract

Traces of stone working are an integral part of natural stone objects and artefacts of historical value. Each preserved trace does not only carry a value in determining the type of tool used, but also provides information about the historic stonemason’s work process and technology. For this reason, it is desirable to assess the restoration method’s influence on the change in surface topography. The effect of restoration interventions was investigated on five stone artefacts, three of ‘opuka’, one of sandstone and one of limestone, four of which showed historic working traces. For this purpose, selected restoration methods—chemical, mechanical and laser—were used. The examined artefacts were accurately photogrammetrically captured before and after the restoration interventions in order to assess and evaluate changes in the degree of preservation of the traces. Fine results using common tools were achieved in terms of geometric quality, level of detail and the documentation’s predictive power. The models’ geometric accuracy is in the single tenths of mm, as well as the matching of the two datasets (before and after).