02179nas a2200205 4500008004100000022001400041245007400055210006900129300001700198490000600215520157700221653002401798653002001822653001601842653001501858100001801873700002001891700001501911856004701926 2013 eng d a2157-690400aLocateMe: Magnetic-fields-based Indoor Localization Using Smartphones0 aLocateMe Magneticfieldsbased Indoor Localization Using Smartphon a73:1–73:270 v43 a

Fine-grained localization is extremely important to accurately locate a user indoors. Although innovative solutions have already been proposed, there is no solution that is universally accepted, easily implemented, user centric, and, most importantly, works in the absence of GSM coverage or WiFi availability. The advent of sensor rich smartphones has paved a way to develop a solution that can cater to these requirements.

By employing a smartphone's built-in magnetic field sensor, magnetic signatures were collected inside buildings. These signatures displayed a uniqueness in their patterns due to the presence of different kinds of pillars, doors, elevators, etc., that consist of ferromagnetic materials like steel or iron. We theoretically analyze the cause of this uniqueness and then present an indoor localization solution by classifying signatures based on their patterns. However, to account for user walking speed variations so as to provide an application usable to a variety of users, we follow a dynamic time-warping-based approach that is known to work on similar signals irrespective of their variations in the time axis.

Our approach resulted in localization distances of approximately 2m--6m with accuracies between 80--100% implying that it is sufficient to walk short distances across hallways to be located by the smartphone. The implementation of the application on different smartphones yielded response times of less than five secs, thereby validating the feasibility of our approach and making it a viable solution.

10aIndoor localization10aMagnetic fields10asmartphones10aubiquitous1 aSubbu, Kalyan1 aGozick, Brandon1 aDantu, Ram uhttp://doi.acm.org/10.1145/2508037.250805402078nas a2200277 4500008004100000245004000041210004000081300001600121490000700137520135000144653001401494653003101508653003201539653002001571653001801591653002001609653001801629653001501647653001201662653001601674100002001690700001801710700001501728700002001743856003701763 2011 eng d00aMagnetic Maps for Indoor Navigation0 aMagnetic Maps for Indoor Navigation a3883 - 38910 v603 a

Magnetic field fluctuations and anomalies inside buildings tend to have a great effect on the compass, which is one of the simplest navigation devices. Alternative navigation requires landmark identification, so those landmarks can be used as guideposts in assisting individuals. By employing a mobile phone with built\_in magnetometer, an extensive data set of 2000 measurements was collected. Using these fields, we identify landmarks and guideposts and create magnetic maps for multiple corridors of a floor in a building. Different phones are used at different sensitivity rates, which effectively portray similar results. Magnetic signatures are used for identifying locations and rooms and are independent of the person, the phone, and the sensitivity of the sensor being used. Magnetic field behavior is demonstrated and compared with theoretical distributions of these fields. The developed magnetic maps can complement existing visual maps for location tracking and navigation of autonomous robots indoors. These maps are particularly useful during limited visual feedback in poor lighting conditions. Moreover, building designers could include this landmark and guidepost information when developing the architecture of a building, which could in turn help people or robots navigate during disasters and emergency evacuations.

10aBuildings10aMagnetic field measurement10aMagnetic field measurements10aMagnetic fields10aMagnetometers10aMobile handsets10amobile phones10aNavigation10asensors10aUncertainty1 aGozick, Brandon1 aSubbu, Kalyan1 aDantu, Ram1 aMaeshiro, Tomyo uhttps://nsl.cse.unt.edu/node/211