ACCURATE ACOUSTIC RANGING SYSTEM USING ANDROID SMARTPHONES By Mohammadbagher Fotouhi, Master of Science A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science at Virginia Commonwealth University Virginia Commonwealth University 2017 Major Director: Dr. Ruixin Niu, Associate Professor of Department of Electrical and Computer Engineering In this thesis, we present the design, implementation, and evaluation of an android ranging system, a high-accuracy acoustic-based ranging system which allows two android mobile phones to learn their physical distance from each other. In this system we propose a practical solution for accurate ranging based on acoustic communication between speakers and microphones on two smartphones. Using the audible-band acoustic signal with the Wi-Fi assistance without the sound disturbance is promising for large deployment. Our method is a pure software-based solution and uses only the most basic set of commodity hardware: a speaker, a microphone, and Wi-Fi communication. So it is readily applicable to many commercial-off-the-shelf mobile devices like cell phones. Our system is the result of several design goals, including user privacy, decentralized administration, and low cost. Rather than relying on any centralized management which tracks the user’s location to help them find their distance, our system helps devices learn their distance from each other without advertising their location information with any centralized management. Compared to alternatives that require special-purpose hardware or pre-existence of precision location infrastructure , our system is applicable on most of off-the-shelf components so it is a commodity-based solution will obviously have wider applications and is cost effective. Currently, two smartphones are used to estimate the distance between them through Wi-Fi and audio communications. The basic idea is estimating the distance between two phones by estimating the traveling time of audio signal from one phone to the other as the speed of sound is known. The preliminary results of ranging demonstrate that our algorithm could achieve high accuracy, and stable and reliable results for real time smartphone-based indoor ranging.

Plus de 70 % de la surface terrestre est recouverte par les mers et océans. Nombre de phénomènes tectoniques parmi les plus dévastateurs ont par ailleurs lieu en environnement océanique. On peut citer en exemple les zones de subduction, pouvant générer des mégaséismes associés à des tsunamis dévastateurs (Sumatra en 2004, Tohokuen 2011), mais aussi les failles décrochantes sous-marines. Dans de nombreux cas, les méthodes de géodésie spatiale ne permettent pas de discriminer entre un comportement bloqué ou asismique, les instruments étant situés trop loin de la zone potentiellement déformée par le processus tectonique. Il faut alors mettre au point de nouvelles techniques qui permettent de prolonger les réseaux d’observation classiques au large afin de cartographier la déformation sur l’intégralité de la zone. Cette thèse s’intéresse à deux méthodes de géodésie fond de mer permettant d’aider à l’évaluation du risque sismique. La première est la distancemétrie relative acoustique, avec comme zone d’application effective la mer de Marmara. Nos premiers résultats laissent supposer un comportement bloqué au niveau du segment de la faille nord-anatolienne immergé devant İstanbul. La seconde zone d’étude considérée est la subduction antillaise. L’échelle de travail nécessite une localisation des points observés dans un référentiel global. Nous étudions les phénomènes océaniques à considérer et détaillons une méthodologie dite GNSS/A (pour Acoustique), consistant en des interrogations acoustiques depuis une plateforme de surface précisément positionnée par GNSS, pour une future expérience de positionnement absolu au large de la Guadeloupe. / More than 70 % of the Earth surface is covered by seas and oceans. Several tectonic phenomena, among the most devastating, take place in ocean environment. For example, the subduction zones, which can generate mega-earthquakes associated with devastating tsunamis (Sumatra in 2004, Tōhoku in 2011), but also the underwater strike-slip faults. In many cases, methods of space geodesy cannot discriminate between a blocked or aseismic behavior, because the instruments are located too far from the area potentially deformed by the tectonic process. Thus, it is necessary to develop new techniques to extend conventional observation networks off-shore to map the deformation in the entire area. This thesis focuses on two seafloor geodesy methods, in order to assess the seismic risk evaluation. The first is the relative acoustic ranging, with an efective deployment of the Marmara Sea area. Our early results suggest a locked state at the segment of the North Anatolian fault of İstanbul. The second area considered is the Caribbean subduction. The working scale requires localization of the observed points in a global reference frame. We study ocean processes to consider, and detail a GNSS/A (Acoustic) methodology, consisting of acoustic interrogations from a precisely GNSS positioned surface platform, for a future absolute positioning experience of Guadeloupe.