I. Introduction
Recently a number of location sensing technologies have been presented for allowing mobile devices to pinpoint their physical position and heading (i.e., the pose) with respect to a predefined coordinate system. The location awareness is a fundamental requirement for many applications, i.e., the personal indoor navigation systems: by assuming the availability of a suitable map of the surrounding, the mobile device can easily compute the path between the current location and the desired destination, driving the user towards the intermediate stages along the path. Furthermore, the tracking of mobile users in indoor environments could enable a wide range of services similar to those enabled by GPS in outdoor. The accurate, relative as well as absolute, personal positioning in GPS-denied environments can be considered a primary factor for service differentiation and personalization.