Structural Health Monitoring (SHM) plays a crucial role in the preservation of heritage structures, enabling the early detection of damage and supporting informed conservation strategies. The effectiveness of SHM depends on the quality of sensor placement, which should maximise the information collected while minimizing the number of sensors. Various optimisation strategies have been developed for Optimal Sensor Placement (OSP), relying on different metrics to identify the most informative sensor locations. However, most of these methods have been applied primarily to modern structures, with very limited validation in historical buildings, which present unique challenges due to their complex geometries, material heterogeneity, and structural evolution over time.

This study aims to bridge this gap by implementing and comparing multiple OSP metrics within the context of a real heritage structure. A data-driven approach is adopted, using experimentally identified modal shapes from an Operational Modal Analysis (OMA) campaign, to mitigate the uncertainties associated with numerical models. The Church of Santa Ana in Seville, Spain, serves as a representative case study due to its architectural complexity and historical significance. The findings reveal notable variations in the performance of the metrics, clearly underscoring the need for tailored optimisation criteria to address the unique challenges of heritage buildings.