Application of the Fluoresecence Lidar Techniques in the Architectural Heritage

Abstract: The primary aim of the research project is to analyse the potential for the application of lidar and fluorescence techniques in building investigation, and also to establish a scientific remote-sensing method for surveying and analysing the historical facade that is non-destructive and can be used in-situ. The fluorescence lidar method uses point-monitoring and scanning of areas that can provide multispectral images in order to identify materials, biodeteriogens and other substances not visible to the human eye. A specific aim of the project is to develop the method to improve the understanding of our building heritage, conservation and its effects, and to provide a basis for new interventions and maintenance. The main focus of this study has been the built environment with an emphasis on masonry with stone and bricks. Fluorescence techniques are known to be capable of revealing aspects that are not evident to the naked eye or to photography. The lidar technique makes it possible to extend the application of fluorescence spectroscopy to the outdoor environment, remote sensing, with sometimes large distances and uncontrollable background light. This project is an international cooperation involving researchers from different disciplines in Sweden and Italy. Six different case studies are central for this analysis of the application of the technique. The work described in the thesis involves both historical-archival studies and in-situ investigations in Sweden and Italy, as well as laboratory studies on stone material. The fluorescence lidar measurements were made both in-situ on the facades of Övedskloster castle in Sweden, on the amphitheatre Coliseum and on the Lateran Baptistery in Rome, Italy and in laboratory studies on stone and brick samples. The six case studies have been diverse not only in their context and historical background but also with regard to the aims and methods of investigation, measurement and analysis. This has given a differentiated material to work with, although the evaluation of the potential of fluorescence´ lidar has been the main objective. In this first phase, the main work has been to collect and organize data. The data has been obtained through historical and archival studies that have provided a basis and background material for ocular investigations on site, laboratory experiments and the fluorescence lidar measurements. The condition of the stone material in the case studies has varied depending on its history, environment and conservation, but it all showed signs of weathering, exfoliation, chromatic alteration, biodeteriogens etc as well as different restoration and conservation histories. The preliminary analysis from measurement data have used to try to identify phenomena which are not visible to the human eye but which may have an impact in the future, e.g. biodeteriogens on the surface, as well as phenomena that can indicate and support the identification of materials and how to distinguish between them. The ultimate purpose is to evaluate the material from the case studies in order to develop the method as a useful tool for the ongoing maintenance, safeguarding and future conservation of our architectural heritage.