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Journal of Sensors
Volume 2016, Article ID 1945695, 16 pages
Research Article

Location Fingerprint Extraction for Magnetic Field Magnitude Based Indoor Positioning

1School of Software Engineering, Beijing University of Posts and Telecommunications, Beijing, China
2Institute of Computing Technology, Chinese Academy of Sciences, Beijing, China

Received 28 May 2016; Accepted 30 October 2016

Academic Editor: Yan Lu

Copyright © 2016 Wenhua Shao et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Smartphone based indoor positioning has greatly helped people in finding their positions in complex and unfamiliar buildings. One popular positioning method is by utilizing indoor magnetic field, because this feature is stable and infrastructure-free. In this method, the magnetometer embedded on the smartphone measures indoor magnetic field and queries its position. However, the environments of the magnetometer are rather harsh. This harshness mainly consists of coarse-grained hard/soft-iron calibrations and sensor electronic noise. The two kinds of interferences decrease the position distinguishability of the magnetic field. Therefore, it is important to extract location features from magnetic fields to reduce these interferences. This paper analyzes the main interference sources of the magnetometer embedded on the smartphone. In addition, we present a feature distinguishability measurement technique to evaluate the performance of different feature extraction methods. Experiments revealed that selected fingerprints will improve position distinguishability.