Archaeological documentation during a securing and restoration pro-ject: an example of successful approach.

The case of the castle of Larciano (Pistoia – Italy)

Abstract

This paper presents the photogrammetric survey of a medieval castle and the challenges we faced in obtaining a complete and accurate documentation. It focuses on the specific workflows that the different documented structures required. The objectives of the archaeological survey were to document the buildings before restoration work and to give the 3D models to the project designers for the calibration of safety work. The case study is the castle of Larciano, that was in the last years object of securing and restoration interventions. More specifically, the works involved the castle walls and its fortified gates. Public institutions, architects, engineers, and archaeologists were involved in the project. A first phase of the restoration project, in 2019, focused on the three fortified gates to the castle. In 2020 the project moved to the eastern section of the walls, which was threatened by a real risk of collapse. On both occasions, archaeological surveys and analyses had to be matched with the need for restoration. During the two phases of intervention, two different workflows were defined, due to the peculiarities of the structures: this confirms that survey of architectural heritage has specific characteristics that challenge the adaptation of archaeologists. For the three gates, 3D models were realized with a photographic campaign after the removal of vegetation from the buildings and before the scaffolding construction. At the eastern walls, the photogrammetric archaeological survey represented a challenge for the types of construction and the environmental challenges. A preliminary photographic campaign, with vegetation, had to be mixed with a second one without it but with the scaffolding. This meant a collection of more than 2000 photos, taken from less than a metre away. The processing phase was hard but successful, and with few adjustments a complete 3D model of this structure was realized, eliminating the scaffolding.