# Multi-Information Fusion Indoor Localization Using Smartphones
###### Abstract  
Accurate indoor localization estimation has important social and commercial values, such as indoor location services and pedestrian retention times. Acoustic-based methods can achieve high localization accuracies in specific scenarios with special equipment; however, it is a challenge to obtain accurate localization with general equipment in indoor environments. To solve this problem, we propose a novel fusion CHAN and the improved pedestrian dead reckoning (PDR) indoor localization system (CHAN-IPDR-ILS). In this system, we propose a step length estimation method that adds the previous two steps for extracting more accurate information to estimate the current step length. The maximum influence factor is set for the previous two steps to ensure the importance of the current step length. We also propose a heading direction correction method to mitigate the errors in sensor data. Finally, pedestrian localization is achieved using a motion model with acoustic estimation and dynamic improved PDR estimation. In the fusion localization, the threshold and confidence level of the distance between estimation base-acoustic and improved PDR estimation are set to mitigate accidental and cumulative errors. The experiments were performed at trial sites with different users, devices, and scenarios, and experimental results demonstrate that the proposed method can achieve a higher accuracy compared with the state-of-the-art methods. The proposed fusion localization system manages equipment heterogeneity and provides generality and flexibility with different devices and scenarios at a low cost. indoor localization; pedestrian dead reckoning; step length estimation; heading direction estimation; equipment heterogeneity +
Footnote †: journal: Medical  
(RFID) positioning [8; 9; 10; 11; 12], Bluetooth positioning [13; 14], geomagnetic positioning [15; 16], visual positioning [17], and ultrasonic positioning [18; 19]. The indoor positioning method based on ultrawideband can achieve high positioning accuracy and good stability. The literature [20] proposed a new collaborative pedestrian synchronous localization and mapping algorithm but requires special infrastructure. The approach, based on infrared technology, requires a lot of power and is blocked by indoor walls or obstacles; therefore, it is used only in some special scenarios [21]. The approaches based on Wi-Fi and Bluetooth are low-cost and easy to promote; however, data acquisition typically requires a long time [18]. The indoor localization method based on RFID achieves high accuracies but has additional infrastructure costs [10; 11; 12; 22]. Geomagnetic sequences are strongly affected by surrounding ferromagnetic materials, making it difficult to establish a fingerprint database with huge human power and update it occasionally [23]. Vision-based positioning has good visibility [24]; however, localization performance is limited by light conditions and cannot be permitted in numerous situations because of privacy and security issues. Of all localization signals, the ultrasonic signal is compatible with mobile equipment, and the data transmission and reception can be obtained using only mobile equipment. Ultrasonic-based localization has good adaptability for scenes without additional infrastructure and high adaptability, and sufficient accuracy for low propagation speed. Localization is achieved by time correlations with low computational complexities, making the localization approach based on ultrasound one of the most competitive indoor localization technologies [1; 10; 11; 12]. However, due to reflection, refraction, obstruction, and the interference of other frequency signals when the acoustic signal propagates indoors, accidental errors will occur in the localization process and result in the deterioration of the localization accuracy in some cases [25]. Pedestrian dead reckoning (PDR) is a localization method that estimates a user's location according to the user's walking characteristics.