%0 Conference Paper %1 SRH06 %A Steinicke, Frank %A Ropinski, Timo %A Hinrichs, Klaus H. %B Proceedings of Virtual Reality International Conference (VRIC) %C Laval %D 2006 %I IEEE Press %K city collaborative concepts interaction planning %P 113--122 %T Collaborative Interaction Concepts for City Planning Tasks in Projection-Based Virtual Reality Systems %U http://www.mcm.uni-wuerzburg.de/fileadmin/06110000/user_upload/Paper/IMG/2006/SRH06.pdf %X In this paper we propose solutions that allow several co-located city planners to perform domain-specific interaction tasks together in one semi-immersive pro jection-based VR system. After a registration process, e.g., by posing gestures or by using speech commands, this group activity can be performed either in a cooperative mode, i.e., tasks are accomplished consecutively, or in a col laborative interaction mode, i.e., users collaborate simultaneously. Both modes as well as multimodal concepts for the registration process are discussed and evaluated. Further VR-based interaction strategies for the city planning domain are presented, which are adapted to the demands of city planners working together in a shared virtual environment.