# A Hybrid Marker-Based Indoor Positioning System for Pedestrian Tracking in Subway Stations
## 5 Discussion  
The main purpose of the system proposed in this paper is to serve an AR-based navigation service to the public by providing a marker- and error-corrected PDR-based localization system. This aim was accomplished by developing a real-time navigation service and error correction model. In addition, we have shown through experimentation that the proposed system can operate more accurately using various techniques. In contrast, other methods using marker-based positioning have left doubts because they simply introduced the concept of a system or reviewed a questionnaire, rather than sharing their full experimental results. The proposed system enables the entire process of marker-based positioning, from specifying a marker installation location, to printing a marker, from the map registration stage. In other words, the system developed in this study enables a navigation service to be used more accurately in various subway stations.  
In experiments, it was confirmed that the HMIPS had improved tracking accuracy over existing methods. In a subway station, the tracking accuracy was improved by 20% in the 3-D space during tracking. Compared to the method using radio signals, our method shows approximately 37.5% better positioning results. However, this result cannot be of great significance because the approaching techniques were quite different. Nevertheless, for places with many environmental variables, such as subway stations, it may be better to provide services using markers rather than using radio signals. In other words, these results imply that an indoor navigation service is possible through the HMIPS, even in places where there are factors that can affect sensor data, such as numerous electrical wiring installations such as those found in subway stations, and frequent entry and exit of trains. Since the system we propose is based on markers, navigation services are not limited to subway stations only. That is, the system can be applied without any limitations to any other classical indoor scenario, such as a supermarket or an underground parking lot, if a marker is installed.  
Although our proposed system works well in subway stations, there are still problems to be solved. We manufactured high-quality materials to minimize marker contamination but could not completely block it (contamination). Furthermore, because high-quality materials were used, it was inevitable that the production cost of the marker proved to be expensive. We provided an image for printing markers on the HMIPS, but the print quality was up to the user. Moreover, if we want to provide practical service for an extended period of time, we will not be able to use ordinary paper. Although these limitations exist, we have confirmed that large-scale services for the public are possible if supported by government departments or companies. We plan to research the possibility of more accurate positioning along with measures to minimize marker contamination and reduce manufacturing costs in future studies.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Figure 11c** & **Mean (m)** & **Standard Deviation (m)** \\ \hline MP & 0.4760 & 1.7094 \\ MPE & 0.3186 & 1.0727 \\ Wi-Fi only & 5.0017 & 0.3042 \\ Wi-Fi + PDR & 4.1982 & 0.3361 \\ \hline
**Figure 11d** & **Mean (m)** & **Standard Deviation (m)** \\ \hline MP & 0.3761 & 1.4003 \\ MPE & 0.2643 & 0.9476 \\ Wi-Fi only & 4.4889 & 0.2829 \\ Wi-Fi + PDR & 3.6557 & 0.3119 \\ \hline \hline \end{tabular}
\end{table}
Table 2: _Cont._