# A Comprehensive Review of Indoor Localization Techniques and Applications in Various Sectors
## 1 Introduction
This type of adaptability is crucial for military missions and emergency response operations, where conditions can change rapidly and infrastructure for localization is often lacking [36]. In parallel, research on adaptive sensor fusion frameworks, as seen in military projects like Project Sentinel, highlights the importance of combining multiple data sources to achieve robustness and flexibility. These frameworks employ hard, soft, and predetermined fusion techniques to maximize accuracy and reliability [37]. Hard fusion integrates raw data from different sensors, soft fusion combines processed data, and predetermined fusion applies predefined rules based on environmental context. This multi-faceted approach allows localization systems to dynamically adjust to real-world conditions, ensuring reliable performance in diverse scenarios, such as urban combat zones or collapsed buildings during rescue operations [36]. The importance of accurate indoor localization becomes even more evident in high-stakes scenarios like military urban operations or emergency rescue missions. In these situations, precise positioning systems enable faster response times, better resource allocation, and enhanced safety for personnel [38]. For example, systems employing cooperative localization--where multiple agents share their positioning data--provide commanders with a comprehensive, real-time overview of troop or responder locations. This real-time situational awareness allows for better decision-making and minimizes the risks associated with poor coordination, such as delayed responses or operational failures [7; 38]. Beyond basic positioning, advanced indoor localization systems offer additional functionalities that further enhance mission effectiveness [39]. These include health monitoring, where soldiers' or first responders' vital signs are tracked in real time to detect potential injuries or fatigue. Another critical feature is weapon orientation tracking, which helps ensure that troops' actions are well-coordinated and aligned with mission goals [38]. After missions are complete, data collected from localization systems can be used for AARs, providing detailed insights into what went well and what could be improved. These reviews are invaluable for refining strategies, improving training programs, and enhancing overall mission preparedness [30]. Moreover, these localization systems reduce the risks associated with fratricide (friendly fire) and miscommunication in high-pressure environments [40]. By offering precise data on the location and orientation of each team member, commanders can issue clearer instructions, and soldiers can act with greater confidence. This not only improves operational efficiency but also increases the overall safety of personnel engaged in complex missions. Looking forward, the continued development of hybrid localization systems will likely focus on integrating AI-driven analytics, machine learning algorithms, and advanced encryption protocols to ensure data security and reliability [41]. As these technologies evolve, they will play an increasingly critical role in enhancing situational awareness, decision-making, and mission success across military, rescue, and other high-stakes domains. By addressing the challenges of GNSS-denied environments and incorporating advanced features, these systems promise to revolutionize how operations are conducted, making them safer, more efficient, and more responsive to the demands of modern challenges [42]. Table 1 summarizes indoor localization systems across sectors, highlighting key applications and technologies. In the medical sector, BLE, IoT-based RTLS, and Wi-Fi support patient tracking, asset management, and HAR. The industrial sector utilizes UWB, RFID, BLE, and Wi-Fi for asset tracking, worker safety, and process optimization, ensuring real-time monitoring and efficiency. Meanwhile, the military sector employs UWB, ZigBee, Wi-Fi, and Bluetooth for personnel tracking, mission planning, and asset management, aiding secure communication and logistics.