Digital photogrammetry and TLS data fusion applied to Cultural Heritage 3D modeling.

A great number of papers have been so far published about the comparison and the integration between terrestrial laser scanning and digital photogrammetry, as surveying and 3D modeling techniques. Though most of the works report about their application to Cultural Heritage, achieved results have shown that these two technologies can supplement each other in creating high-quality 3D recordings and presentations: laser scanning can produce the dense 3D point-cloud data that is required to create high-resolution geometric models, while digital photogrammetry is more suited to produce high-resolution textured 3D models representing just the main object structure. It should be noted however that in many cases, fusion or integration of both surveying techniques is regarded only as the application of digital images onto the laser scanning-based 3D model and/or the production of orthophotos. It is well known that for complex architectures, no modeling technique by itself can efficiently and quickly provide a complete and detailed 3D model: a hibryd approach is required. In the view of an insight investigation on this topic, this paper reports on the study of merging digital photogrammetry and laser scanning to produce a unique detailed 3D model of a complex historical building. The basic shapes (e.g. walls and other main structures) were determined by image-based methods using a 7Mpixel digital camera while fine details or more complex shapes were surveyed with a TOF laser scanner. Adopted data collection procedures and modeling issues, related to the integration of the different datasets, will be discussed. A final textured 3D model and virtual flights over the historical building will be also presented.