On Multi-image Reconstruction from Historic Photographs

The ultimate purpose of this work is to reconstruct photogrammetrically a distinguished building in the centre of Athens, which has been torn down years ago. Five old photographs were available taken apparently with the same camera, the nominal calibration parameters of which could be somehow ‘guessed’. As a first step, it was decided to employ our own bundle-adjustment software, which works within a commercial CAD environment. Besides, unlike most commercially available 3D reconstruction software, it allows full control over the whole adjustment process (by presenting individual image point residuals, producing RMS errors for check points, accommodating additional calibration parameters etc.). A second task was to compare these results with PhotoModeler, in order to evaluate this widely used (but in certain aspects ‘obscure’) tool against a rigorous photogrammetric approach. Besides solutions with no control information, a few full and partial control points were established from existing architectural drawings, allowing self-calibration procedures. The two software tools produced essentially equivalent results, thus validating the precision of the PhotoModeler approach. However, certain additional features of a proper bundle adjustment program (e.g. recovery of radial lens distortion, self-calibration with minimal or unconventional control), discussed here, may allow a fuller exploitation of the powerful reconstruction and visualisation tools of the PhotoModeler type. It was confirmed that, using suitable software, rigorous approaches can be applied to historic images, and results of reasonable precision may be expected, limited only by possible inaccuracies in scale.