Research on mobile augmented reality (AR) so far concentrated on building and deploying prototypes and investigating technical and user interface aspects. To create plausible application scenarios other concerns also need to be addressed. In particular, the size of the physical world made accessible by mobile AR raises new challenges in terms of scalability: the system will among others need a very large 3D world model, display this model efficiently without visual clutter or graphics overload, should operate in networked mode with arbitrary collaborators, provide tracking anywhere etc. In this paper we address some of these scalability issues, namely data management for very large geographic 3D models, and efficient techniques for collaborative outdoor user interfaces. As an application scenario, we use a tourist group guide application operating in the city of Vienna.
submitted to ISMAR'04