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Sensors 2014, 14(1), 731-769; doi:10.3390/s140100731
Article

Improving Inertial Pedestrian Dead-Reckoning by Detecting Unmodified Switched-on Lamps in Buildings

* ,
 and
Centre for Automation and Robotics (CAR), Consejo Superior de Investigaciones Cientificas (CSIC)-UPM, Ctra. Campo Real km 0.2, La Poveda, Arganda del Rey, Madrid 28500, Spain
* Author to whom correspondence should be addressed.
Received: 18 November 2013 / Revised: 8 December 2013 / Accepted: 16 December 2013 / Published: 3 January 2014
(This article belongs to the Section Sensor Networks)
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Abstract

This paper explores how inertial Pedestrian Dead-Reckoning (PDR) location systems can be improved with the use of a light sensor to measure the illumination gradients created when a person walks under ceiling-mounted unmodified indoor lights. The process of updating the inertial PDR estimates with the information provided by light detections is a new concept that we have named Light-matching (LM). The displacement and orientation change of a person obtained by inertial PDR is used by the LM method to accurately propagate the location hypothesis, and vice versa; the LM approach benefits the PDR approach by obtaining an absolute localization and reducing the PDR-alone drift. Even from an initially unknown location and orientation, whenever the person passes below a switched-on light spot, the location likelihood is iteratively updated until it potentially converges to a unimodal probability density function. The time to converge to a unimodal position hypothesis depends on the number of lights detected and the asymmetries/irregularities of the spatial distribution of lights. The proposed LM method does not require any intensity illumination calibration, just the pre-storage of the position and size of all lights in a building, irrespective of their current on/off state. This paper presents a detailed description of the light-matching concept, the implementation details of the LM-assisted PDR fusion scheme using a particle filter, and several simulated and experimental tests, using a light sensor-equipped Galaxy S3 smartphone and an external foot-mounted inertial sensor. The evaluation includes the LM-assisted PDR approach as well as the fusion with other signals of opportunity (WiFi, RFID, Magnetometers or Map-matching) in order to compare their contribution in obtaining high accuracy indoor localization. The integrated solution achieves a localization error lower than 1 m in most of the cases.
Keywords: indoor localization; signals of opportunity; light/illumination; pedestrian dead-reckoning; smartphone indoor localization; signals of opportunity; light/illumination; pedestrian dead-reckoning; smartphone
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Jiménez, A.R.; Zampella, F.; Seco, F. Improving Inertial Pedestrian Dead-Reckoning by Detecting Unmodified Switched-on Lamps in Buildings. Sensors 2014, 14, 731-769.

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