Public seminar – A/Prof Günther Retscher, TU Wien

A/Prof Günther Retscher will give a talk on Novel Technological Developments for Indoor Wi-Fi Positioning.

When: Friday 3 November, 2017, 3:30 – 4:30 pm

Where: 80.05.011, City Campus, RMIT University


The development of indoor navigation systems has become a growing field of research interest in recent years as many applications nowadays require seamless ubiquitous positioning in combined out-/indoor environments. There are still many unresolved challenges in such type of applications. This talk aims to provide an insight into the use of the most prominent signal of opportunity, namely Wireless Fidelity (Wi-Fi). Two new approaches developed at the TU Wien – Vienna University of Technology, Austria based on the measurement of the received signal strength (RSS) of the surrounding access points (APs) are introduced. In the first one, localization fingerprinting is the employed positioning method. A so-called ‘intelligent check-point’ (iCP) concept has been developed to reduce the laborious work in training for the establishment of reference points and radio maps of Wi-Fi signal strength distributions located throughout the area of interest. The second approach is based on the well-known Differential GPS (DGPS) principle of operation. We term it Differential Wi-Fi (DWi-Fi) by analogy whereby from measurements to reference stations deployed in the area of interest area correction parameters are derived and applied for positioning determination of a mobile user. Hence, range or coordinate corrections can be estimated from a network of reference station observations as it is done in common CORS (Continuous Operating Reference Stations) GNSS networks. A low-cost realization with Raspberry Pi units is employed for these reference stations. These units serve at the same time as APs broadcasting Wi-Fi signals as well as reference stations scanning the receivable Wi-Fi signals of the surrounding APs. As the RSS measurements are carried out continuously at the reference stations, dynamically changing radio maps of RSS distributions are derived. Similar as in location fingerprinting this radio maps represent the RSS fingerprints at certain locations. From the areal modelling of the correction parameters in combination with the dynamically updated radio maps the location of the user can be estimated in real-time. With conducted case studies the potential of these novel approaches is investigated. It is shown that an integration of DWi-Fi with the iCP concept and inertial navigation (IN) using the smartphone sensors, such as accelerometers, digital compass and gyroscopes, yields positioning accuracies of better than one meter.


Guenther Retscher is Associate Professor at the Department of Geodesy and Geoinformation of the TU Wien – Vienna University of Technology, Austria. He received his Venia Docendi in the field of Applied Geodesy from the same university in 2009 and his Ph.D.

in 1995. His main research and teaching interests are in the fields of engineering geodesy, satellite positioning and navigation, indoor and pedestrian positioning as well as application of multi-sensor systems in geodesy and navigation.