Façade Modelling for Historical Architecture

The paper presents an approach to efficiently increase the geometric detail of complex building facades by terrestrial laser scanning (TLS). Such applications are frequently required for documentation and presentation of architectural heritage. The modeling of the building geometry is based on a coarse to fine approach. Thus, an approximate 3D building model like it is typically available from airborne data collection provides a-priori information to support the subsequent processing of the terrestrial data. Since the generation of a true CAD description of facade primitives such as windows, doors and balconies is supported by a close integration of such existing building models, the data collection from the scratch can be avoided and the modelling process is facilitated. Thus, after the alignment of the collected LIDAR point clouds to the given 3D model, window structures are extracted and integrated to a refined CAD model. These structures can be further refined by edges extracted from additional façade images. Alternatively to such an explicit 3D representation of façade structures, which is realized by an approach based on cell decomposition, a planar mapping of the LIDAR point clouds to generate a 2.5D representation can be used. By these means a refined visualization of the façade geometry is feasible based on standard computer graphic techniques like bump or displacement mapping.