I. Introduction
Positioning systems are common in software applications that manage geographic information. Indeed, using computing devices while on the move is currently very common. PDAs, mobile phones, car navigation systems, and mobile entertainment devices are some examples. The basic idea of location and context-awareness is to provide services that fit the user's current situation. An interesting challenge is how to locate a mobile device inside a building as in the case of administrative buildings, hospitals or art museums. The idea is creating systems that continuously adapt to the user's needs and surroundings.