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G. Retscher:
"Research Activities on Pedestrian Navigation at TU Wien";
Talk: Guest Lecture at the Department of Civil Engineering of the University of Nottingham Ningbo, Ningbo, China (invited); 2016-12-22.

The development of pedestrian navigation systems has become a growing field of research interest in recent years as many applications nowadays require ubiquitous positioning in combined out-/indoor environments for mobile users. There are still many unresolved challenges especially for indoor navigation applications as satellite-based GNSS and GNSS-aided inertial navigation systems (INS) are capable methods for mainly outdoor navigation only. Indoor positioning can be defined as any system which attempts to provide an accurate positioning inside of a covered structure using radio waves, acoustic signals, or other sensory information collected by mobile devices. It is primarily used for real-time location of people or objects in large buildings and in closed areas/spaces. Several types of location-sensing systems exist which each have its own strengths as well as limitations. In general, localization technologies can be classified into three categories, i.e., designated technologies based on pre-deployed signal transmission infrastructure, technologies based on `signals-of-opportunity´ and technologies not based on signals. In the first categories fall systems using infrared or ultrasonic signals, magnetic fields, Ultra Wide Band (UWB), Radio Frequency Identification (RFID) or other RF-based systems. Signals-of-opportunity include RF signals originally not intended for positioning, for instance, Wi-Fi, digital television, mobile telephony, FM radio and others. Dead reckoning (DR) using inertial sensors (accelerometers and gyroscopes) as well as vision/camera systems belong to the third category. This talk aims to provide an insight into the use of the most prominent signal of opportunity, i.e., Wi-Fi. A novel approach termed Differential Wi-Fi (DWi-Fi) is presented which is based on the well-known DGPS principle. In this concept reference stations are deployed in the area of interest. From measurements to reference stations correction parameters are derived and applied for positioning determination of a mobile user. This approach has been extensively tested in a multi-storey office building of TU Wien. The main findings are highlighted in this presentation. It is shown that the approach is capable to locate a user carrying a smartphone or other mobile device in complex building environments with a high accuracy and reliability. Furthermore, the combination and integration with RFID and ambient magnetic fields for positioning is briefly elaborated and a cooperative solution for positioning of a whole smartphone App user group. As an example the guidance of people in large multi-modal public transit interchanges is presented.