SLAM-based survey supporting vulnerability assessments of built heritage at risk

The documentation of historical churches for structural and seismic vulnerability assessment requires survey techniques that balance metric reliability and operational efficiency. Recent developments in mobile mapping systems based on Simultaneous Localization and Mapping (SLAM) offer new opportunities for rapid and flexible data acquisition. This paper investigates the potential of SLAM-based surveys as a fast and cost-effective solution for supporting multi-level structural analyses of built heritage, adopting six historical parish churches located in the Lunigiana region (Italy) as a case study. Indoor and outdoor surveys were performed using the X70GO (Stonex), a handheld SLAM system equipped with GNSS-RTK, following acquisition strategies designed to limit drift and improve geometric consistency. The resulting 3D models are analysed primarily in relation to their usability for structural interpretation. The contribution of SLAM-derived models is discussed with reference to multiple levels of analysis, ranging from preliminary seismic vulnerability assessments based on collapse mechanisms and simplified indices to more detailed readings of structural configurations, global deformations, and damage patterns. Particular attention is also given to the practical characterization of measurement noise under typical survey conditions, in order to frame the reliability limits of geometric observations relevant to structural diagnostics. The results show that SLAM-based surveys can significantly enhance the efficiency of data acquisition and support reliable qualitative and quantitative interpretations at the building scale, especially in the early and intermediate phases of vulnerability assessment. Limitations remain in the detection and measurement of fine-scale crack patterns, which are constrained by the intrinsic noise level and spatial resolution of the system.