Laser Data for Virtual Landscape Generation 2 Acquisition of Virtual City Models

Within this article a procedure for the automatic generation of 3D city models is presented. For that purpose existing ground plans provided from a 2D GIS and height data measured by airborne laser scanning are combined. The presented approach can be applied for a fully automatic reconstruction of an urban model, for interactive control and correction of these automatically generated results and for a semi-automatic data capture. The results are 3D CAD models of the buildings. By an optional mapping of terrestrial or aerial images onto the reconstructed facades, virtual city models can be generated. 1 INTRODUCTION One of the main tasks in photogrammetry is the efficient data capture for the generation of realistic representations of the real world. A great impact on the future demands to these geographic data bases can be expected due to the great success of the World Wide Web. Amongst other things, this success also resulted in a wide spread of international standards for the description of 3D worlds like the Virtual Reality Modeling Language (VRML). Additionally supported by the free availability of VRML-browsers, 3D visualization is now feasible for each standard user. Thus, the spread of applications, which are based on the access and visualization of virtual 3D worlds will increase tremendously. Possible scenarios are tourism information systems, which can help the potential visitor to plan trips as a preview afore his actual journey using virtual reality techniques. Hotel reservation systems can be integrated in order to give the user an impression of the hotel's surrounding in a virtual 3D environment. Due to the increasing power of personal digital assistants (PDA) also systems for a personal navigation are imaginable, where the user's route is not only overlaid to a 2D map, but is presented much more realistic in a 3D virtual model. All these applications will result in a great demand for the production of virtual city models and landscapes, presuming the availability of tools for efficient data capture. The development of these tools has been in the focus of a number of research activities and has led to a number of automatic and semi-automatic approaches (Gruen, Baltsavias and Henricson, 1997). Even though fully automatic procedures have been applied successfully for a number of individual data sets, it is generally agreed that their employment in a production environment can not be expected in the predictable future. Consequently, research and development has been concentrated to …