Four-dimensional reconstruction of cultural heritage sites based on photogrammetry and clusteringFour-dimensional reconstruction of cultural heritage sites based on photogrammetry and clustering Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2018-06-132017enA system designed and developed for the three-dimensional (3-D) reconstruction of cultural heritage (CH) assets is presented. Two basic approaches are presented. The first one, resulting in an "approximate" 3-D model, uses images retrieved in online multimedia collections; it employs a clustering-based technique to perform content-based filtering and eliminate outliers that significantly reduce the performance of 3-D reconstruction frameworks. The second one is based on input image data acquired through terrestrial laser scanning, as well as close range and airborne photogrammetry; it follows a sophisticated multistep strategy, which leads to a "precise" 3-D model. Furthermore, the concept of change history maps is proposed to address the computational limitations involved in four-dimensional (4-D) modeling, i.e., capturing 3-D models of a CH landmark or site at different time instances. The system also comprises a presentation viewer, which manages the display of the multifaceted CH content collected and created. The described methods have been successfully applied and evaluated in challenging real-world scenarios, including the 4-D reconstruction of the historic Market Square of the German city of Calw in the context of the 4-D-CH-World EU project. http://creativecommons.org/licenses/by/4.0/Journal of Electronic Imaging261 Voulodimos, Athanasios 1984- Fritsch Dieter Doulamis Nikolaos D. Makantasis Konstantinos Μακαντασης Κωνσταντινος Doulamis, Anastasios Klein Michael Society of Photo-optical Instrumentation Engineers Content-based filtering Density-based spatial clustering of applications with noise Four-dimensional Iterative closest point Outlier elimination Photogrammetry Spectral clustering Terrestrial laser scanning Texture mapping Three-dimensional reconstruction