This paper presents an overview on the performance of hybrid data fusion and tracking algorithms evaluated in the WHERE consortium. The focus is on three scenarios. For the small scale indoor scenario with ultra wideband (UWB) complementing cellular communication systems, the accuracy can vary in time as a connectivity-dependent random process distributed over 3 orders of magnitude, from 100m in the worst situation down to 0.1m in the most favourable one. In the mid scale scenario, time difference of arrival (TDOA) measurements from a cellular network can give wide-area coverage with limited accuracy, whereas the received signal strength measurements of Wi-Fi hotspots give more accurate results if coverage is available. Finally, for large scale outdoor scenarios, cellular TDOA measurements can support global navigation satellite systems (GNSSs) especially in critical scenarios, where only a few satellites are visible. This is even the case when the overall accuracy of stand-alone cellular positioning is lower than that for GNSS positioning under optimum conditions.
