## 4 Data Management
### IoT-SHM Systems  
The combination of SHM systems with smart sensors architecture, cloud computing, and the IoT has enabled rapid, accurate, and low-cost services, as well as powerful transmission, storage, and processing of data beyond the capability of the existing SHM systems [188; 189]. In addition to smart sensors, the IoT-SHM systems comprise the gateway, the remote control, and the service room (RCSR), as well as an open platform communications (OPC) server (Figure 12). The gateway of the system is a network node that can manage and optimize data acquired by sensors to check node connectivity and perform system integrity tests. The RCSR hosts a database to store all collected data to be used for big data analysis and connectors to an OPC server. Moreover, from the RCRS, it is possible to perform queries of specific sensor nodes, to acquire the status or other useful management parameters. Furthermore, IoT systems can potentially be used to monitor many monuments concurrently and transmit the acquired information to a remote server, aiming to facilitate maintenance operations and prompt interventions in an emergency [190]. The challenges in adopting IoT-based technologies for SHM, including data privacy issues, the limited battery life of sensors, and the lack of standardization, have recently been analysed by [PERSON] et al. [191].  
[PERSON] et al. [188] recently presented an overview of the basic concepts of IoT-SHM systems for masonry structures and two interesting applications on historical masonry structures. The first case was a panel reproducing a typical masonry typology used in Calabria (southern Italy), subjected to diagonal compression in the lab environment. The second was an existing masonry castle in Calabria (prone to high seismic hazards), subjected to dynamic identification. In both examples, the data recorded by the monitoring systems (composed of LVDTs and strain gauges in the first case and piezoelectric accelerometers in the second) were utilized to properly calibrate the FE model in a way that could be representative of the actual behaviour of the structure. These operations can be carried out in quasi real-time, by constantly interfacing with the information provided by the implemented IoT-SHM system that exchanges information continuously and remotely with the numerical model via the Internet.  
[PERSON] et al. [156] implemented a remote monitoring system which integrates a network of fixed sensors and a UAV, testing the system on three ancient structures. The data acquired from the sensor nodes are delivered to a remote server through an IoT protocol for reliable data exchanges, namely MQTT. The images collected through the UAV were used to build a 3D reconstruction of the structures, allowing an operator to interact dynamically with the real-time readings collected by the IoT network.  
[PERSON] et al. [192] developed a low-cost distributed sensing system for measuring relevant vibrations caused by human activities and earthquakes, which was specifically designed for application to a cultural heritage underground site. The system was based on IoT communication techniques, low-power microcontrollers, event-driven strategy, and self-contained battery-powered electronics, aiming to reduce the costs, impact, and risks associated with the need for periodic maintenance and supervision. First, its operation was assessed uncover laboratory conditions by comparing it with a commercial accelerometer. Later, it was tested in the field. The results showed that the proposed system could successfully monitor acceleration at several locations within the site, detecting the most relevant stresses and allowing for the identification of risks.