Carrying-mode Free Indoor Positioning Using Smartphone and Smartwatch and Its Evaluations

As smartphones are much used over a wide area, the pedestrian navigation systems are greatly utilized in our daily lives. In general, navigation systems use GPS (Global Positioning System) for the user’s positioning but its accuracy tends to decrease in indoor environments. A pedestrian dead reckoning method, or PDR method in short, is one of the positioning methods in indoor environments, which estimates the user’s positions by using sensors such as acceleration and angular velocity sensors. These PDR methods do not always use external infrastructures and hence they can be implemented with a lower cost. When we consider using a smartphone as a PDR sensor device, attention must be paid to the fact that there are various carrying modes such as holding it directly and carrying it inside a pocket. How to deal with these various carrying modes is of great concern in PDR when using a smartphone. In this paper, we propose a PDR method based on a combination of a smartphone and a smartwatch. By synchronizing the smartphone and smartwatch sensors effectively, the proposed method can successfully reduce drift errors and thus estimate accurately the user’s positions, compared to just using a smartphone. Furthermore, even when the user carries his/her smartphone in various carrying modes, the proposed method still realizes accurate PDR. The experimental results demonstrate that the positioning errors are reduced by approximately 82.1% on average compared to the existing method.