Terrestrial Laser Scanning and Digital Photogrammetry for Heritage Conservation: Case Study of the Historical Walls of Lagos, Portugal

Abstract. Conservation planning is a complex process involving a wide range of agents such as architects, engineers, conservators and archaeologists. Their integrated inputs contribute to the definition of criteria for the conservation project and the conservation strategy. In this process, graphical documentation is a common denominator to all involved areas-of-expertise. It provides the basis for the dialog between agents coming from different fields of knowledge that often don’t speak the same technical language nor share the same codes. The way this dialog can be improved through documentation is the main motivation of our study.In this paper we analyze the requirements of digital documentation in Cultural Heritage (CH) conservation strategies, and we tackle the fundamental role of photogrammetry and terrestrial laser scanning (TLS), and integrated implementation throughout the several steps, from the fieldwork to the conservation planning for CH sites. The described process is demonstrated through the case study of ‘the conservation project of the historic walls of Lagos’, in south Portugal.After introduction and related work, the study is structured in four main sections. In the second section, we present the case study and conduct an analysis of existing data and preliminary synthesis of heritage values related to the historic walls of Lagos. Second section corresponds to an overview of the project workflow. This spans from recording and documentation, considering geometry, colour, light, materials and degradation forms; to their analysis and diagnosis, resulting in criteria and guidelines for the intervention actions. Third section emphasises on how the simultaneous use of photogrammetry and TLS in the documentation process, and its relationship with other methods and techniques, introduces a distinctive character in the conservation project. Fourth section is about the documentation process with photogrammetry and TLS. Finally, fifth section focus in the analysis and architectural project.