## 4 Discussion  
### Comparing Different Technologies  
Positioning system technologies are divided into external and internal types. GPS is the most commonly used external system, while internal technologies include Wi-Fi, RFID, laser, infrared, and ultrasound. GPS operates autonomously, without the need for additional technology to provide location services, while RFID enables connections between tagged objects and information systems, providing lightweight communication. However, the low positioning accuracy of RFID can be a challenge when used for rescuing trapped workers in the event of a tunnel accident [75].  
Wi-Fi-based real-time location systems (RTLS) are reliable and are managed by dedicated software. Compared to other location technologies such as GPS, smartphone location, RFID, and ZigBee, Wi-Fi offers the following advantages: (1) it works indoors and outdoors, enabling widespread positioning; (2) it uses the existing Wi-Fi network, requiring no modifications, making it cost-effective; (3) its signal is less affected by obstacles, even in non-line-of-sight situations [75].  
Research into indoor positioning technologies has resulted in several categories, including conventional radio frequency (RF) technologies, such as Wi-Fi, BLE, Zigbee, RFID, UWB, and indoor GNSS, as well as non-electromagnetic (non-EM) methods, such as ultrasound and geomagnetic waves. Vision-based technologies using full-spectrum light, such as image processing and range imaging, are also part of this development [76].  
Despite extensive research, there is no ideal internal positioning system. Each internal positioning technology, principle, and algorithm has its strengths and limitations. As a result, researchers suggest combining different internal and external positioning technologies to address each of their weaknesses and achieve more accurate positioning. This approach, known as hybrid positioning, can be divided into three types: (1) hybridisation of internal and external positioning technologies, (2) hybridisation of internal positioning technologies, and (3) hybridisation of internal positioning principles. In particular, hybrid indoor/outdoor positioning often involves combining GPS with indoor Wi-Fi systems, which is particularly useful in semi-indoor environments, such as construction sites [76].  
[PERSON] et al. [76] outline the main indoor positioning technologies as follows:  
* Wi-Fi: the most widely used wireless communication technology, making it the most common choice for indoor positioning systems.
* BLE: a wireless technology with low power and short-range capabilities that operates in the same 2.4 GHz band as Wi-Fi and is widely available on most smartphones.
* RFID: a well-established short-range communication technology used in various applications such as asset tracking, inventory monitoring, and toll collection. It consists of tags, antennas, and a computer that estimates the target's position.
* UWB: a high-data-rate communication technology that has become popular for indoor positioning due to its accuracy and performance advantages.
* GNSS: external positioning systems such as GPS, GLONASS, GALILEO, and Bei-Dou are global but cannot be used indoors due to building obstructions. Indoor GNSS systems, often using radio or laser-based signals, solve this problem, allowing smartphones to track positions indoors and outdoors.
* Vision: an emerging technology used to develop vision-based indoor positioning systems with broad applications.  
UWB systems provide high accuracy with low power consumption, while RFID and RF-based indoor GNSS systems provide medium to high accuracy. Dedicated indoor GNSS and RFID systems are faster, while smartphone-based GNSS systems are slower. High accuracy indoor GNSS systems are more expensive than RFID systems, while laser-based