Landmarks: yes; but which?: five methods to select optimal landmarks for a landmark- and speech-based guiding system

Navigation aids based on landmarks have been successfully investigated over the last years. There seems to be little doubt that navigation systems using landmarks clearly outperform those systems, relying only on distance specifications. Little, however, is known about the optimal selection of landmarks that are used to lead the user through an environment. This paper presents five methods to select landmarks that are visually and semantically distinguishable and which are suited to lead the user to his/her goal. The paper also discusses the lessons learned from the application of these methods. It shows the results that can be expected and it highlights also their possible traps and drawbacks.