Near Infrared Spectra and Hyperspectral Imaging of Medieval Fortress Walls in Carcassonne: A Comprehensive Interdisciplinary Field Study

Studying archaeological materials we often have to deal with sensitive artefacts or protected ancient monument sites that may be large in size or located in remote places. The bottom line is that the things we want to study often cannot be moved into or sampled in laboratory analytical conditions. For this reason the only possible means of study is by using field or portable instruments. In a previous article in NIR news, Geladi and Linderholm presented a tentative approach to simplified near infrared (NIR) imaging using modified standard digital RGB cameras to acquire chemical information. A more comprehensive study has now been launched in the medieval fortress of Carcassonne involving a cooperation between the universities of Umeå and Rennes, and the research institute of IRSTEA of Montpellier. This study aims to combine several spectroscopic techniques in order to resolve archaeological problems related to which raw materials were used during the city wall construction, and also to improve our understanding of the different phases of construction and use of the city walls. This study was also used for elucidating the different qualities and weak points of the applied field methods.