Reconstruction of urban sites from photos

Abstract

This paper reports the results of an experiment that aims at the virtual reconstruction of a urban site that has been partially reshaped during the 20th century; the reconstruction process is based on period photos. The chosen case study is the eldest harbour of Palermo, named ‘Cala’; the site was bombed during World War II and new buildings took the place of the ruined ones. Two period photos, taken from an aircraft, document the buildings that were destroyed by bombs. The 3D restitution process used the ‘inverse’ projection from period photos (2D) to the virtual space (3D) ; the first step was therefore addressed to the calculation of the inner parameters (focal length, principal point coordinates) and of the cameras’ pose, i.e. their position and orientation. The data needed for these calculations were extracted from the 3D laser scanning survey of those buildings that appear in photos and that are still on site. The calculation of inner parameters and poses has been computed with a motion tracking commercial package. The second part of the paper focuses a process for the fruition of virtual reconstructions, based on the alignment of real panoramic images, generated by photos taken on site, and of virtual panoramic images, extracted from the 3D reconstruction model; the proposed method uses SfM photogrammetric tools.