# Wearables for Industrial Work Safety: A Survey
## 3 State-of-the-Art Techniques in the Field of Industrial Wearables
### Localization Techniques
However, it is more desirable, especially during evacuations from the rubble or other emergency cases. In outdoor cases, random existing static anchor stations are usually used to determine the location, whereas in indoor cases, anchors' deployment could require complex preliminary calculations. We further consider the techniques from both indoor and outdoor cases, see Table 6. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Technology** & **Localization** & **Typical env-t.** & **Accuracy** & **Additional Details** \\ \hline GNSS [147] & Time-based & Outdoor & cm-level & Global, not applicable indoors, still considered as high consuming for industrial wearabes, however, some companies already started to present ultra-low power GNSS [148] \\ \hline Wi-Fi & Time-based, Angle-based, Power-based & Indoor & m-level & Nowadays, Wi-Fi fingerprinting (FP) is one of the most promising localization approaches for industrial wearables due to good accuracy and relatively low cost. The disadvantage of this approach is high consumption in terms of power and efforts spending on the training step \\ \hline BLE [151] & Time-based, Power-based & Indoor & m-level & Another perspective technology for indoor localization in IIoT [152] with such advantages as easy deployment, low cost, and low power consumption. However, the accuracy of the method is not very high, and supplementary algorithms are required to improve it [153]. \\ \hline UWB & Time-based, Angle-based & Indoor & cm-level & This method provides the highest accuracy of the localization, requires not much power, has immunity to fading, applicable even in the case of underground worksites. However, it is hard to deploy [155; 156]. \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparison of localization solutions. Usually, we want to identify the worker's position in a relatively limited area, referring mainly to indoor localization. It is worth noticing that in such manufactures as construction or logistics, for example, just indoor localization is not sufficient. Thus, the perfect variant for some industries would require seamless connectivity, which continuously monitors the location of people/equipment/assets. However, seamless localization is still a problem: there is no localization solution for both outdoors and indoor cases and cellular-based solutions have lousy accuracy. This situation is expected to be changed with the coming 5G that, as was announced, will ensure sub-meter accuracy. However, the question is still open. As mentioned before, localization accuracy is still a big issue, especially in the indoor environment. To improve it, engineers explore and apply different combinations of technologies as it was done in QUUPPA Intelligent Locating System where RSSI was combined with AoA Direction Finding signal processing methodology [164]. However, the declared high accuracy of less than 10 cm is offset by high cost, small coverage, and relative deployment complexity [165]. Another big issue in this area is providing an accurate localization in underground work sites. For these purposes, ground-based pseudolites (pseudo-satellite transmitters) can provide localization in industrial environments where the GPS has poor or no coverage, such as deep, open-pit mining, high water dams; urban canyons; large indoor industrial halls. Two well-known positioning solutions are LocataNet, developed by Locata Corporation/Leica, and Terralite XPS, developed by Trimble. Both use a network consisting of fixed pseudolites installed on the ground, around the perimeter of the objective; mobile receivers installed on moving equipment such as heavy engineering vehicles and aircraft [166; 167; 168]. These pseudolite systems operate in industrial environments such as Boddington Gold Mine (Australia), Morenci Copper Mine (Arizona, USA), White Sands Missile Range (New Mexico, USA). The main advantages are centimeter-level accuracy, coverage radius of several tens of km, obtained with just 10 pseudolites [168].