Journal of Cultural Heritage 13 (2012) 215–220 Available online at www.sciencedirect.com Case study Laser scanning and digital imaging for the investigation of an ancient building: Palazzo d’Accursio study case (Bologna, Italy) Arianna Pesci a,∗ , Elena Bonali b , Claudio Galli b , Enzo Boschi c,d a Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna, v. Creti 12, 40128 Bologna, Italy b Università degli Studi di Bologna, DAPT, v. Risorgimento 2, 40136 Bologna, Italy c Università degli Studi di Bologna, Dipartimento di Fisica, v. le Berti Pichat 8, 40127 Bologna, Italy d Istituto Nazionale di Geofisica e Vulcanologia, v. Vigna Murata 605, 00147 Roma, Italy a r t i c l e i n f o Article history: Received 4 May 2011 Accepted 13 September 2011 Available online 12 October 2011 Keywords: Terrestrial Laser Scanning Visual Imaging Cultural Heritage Restoration Historical information a b s t r a c t This paper describes a scientific approach aimed at studying the ancient part of Palazzo d’Accursio (Bologna, Italy), a masonry building which is part of the Italian cultural heritage. Laser scanning and the inspection of digital images are used to detect traces of restoration works and other interesting fea- tures related to both architectural marks and natural or anthropic events. One of the main elements of the method is the analysis of residual maps, obtained by computing the differences between the point coordinates of the fac ¸ ade and reference fit planes. The obtained results, based on both radiometric and geometrical analysis, are used to provide a reasonable hypothesis as to the original configuration of the studied building, while taking into account the available historical information about the constructive phases of the building. © 2011 Elsevier Masson SAS. All rights reserved. 1. Research aim The restoration of an ancient building, which provides both historical and architectural information, connects humanistic and scientific research. An exhaustive characterization of the manu- facture and an effective conservation plan require the acquisition of all the available historic documentation, architectural and metrological studies, as well as laboratory and in situ analyses of the materials. A contactless, non-invasive surveying tech- nique like terrestrial laser scanning (TLS) allows the acquisition of dense and accurate geometric and radiometric information about the observed surface of the building, which can be easily integrated with data provided by high resolution digital imag- ing. A thematic investigation is possible, leading to the analysis and the interpretation of building stratigraphy and achieving the goal of understanding the historical and constructive complex- ity of the monument, in agreement with the restoration rules as described in the “The Venice Charter” (UNESCO, available at: http://www.international.icomos.org). In order to integrate the historical and scientific information to better understand the history of the Palazzo d’Accursio in Bologna (Italy), which is a very important component of the Italian cultural heritage, TLS and digital imaging were used. The aim of this study ∗ Corresponding author. E-mail addresses: pesci@bo.ingv.it (A. Pesci), elenabonali@libero.it (E. Bonali), cgalli@unibo.it (C. Galli), boschi@ingv.it (E. Boschi). is to confirm or deny the little existing historical documentation about the constructive phases of the studied building, leading to a reasonable assumption as to its original configuration. 2. Introduction A very important issue in the study of ancient historical masonry buildings is the ability to accurately measure the geometrical shapes, the characteristic features, the wall configurations, even- tual microcracks and other details. The present state of an historical monument generally results from a sequence of interventions and alterations due to layout changing, restorations or damages induced, for example, by natural events like earthquakes or lighting, or man-made events like wars, burning, and so on. In the frame of the contactless and non-invasive techniques, buildings can be observed by means of direct visual inspection, infrared thermography (IRT) [1], image-based observation [2], TLS [3,4], digital photogrammetry [5,6] and so forth [7,8]. The TLS allows a time- and cost-effective acquisition of dense and accu- rate information of the studied monument, leading to an accurate digital model. One of the main products of TLS standard analysis is the accurate reconstruction of 3D models leading to a realistic representation of buildings [9,10], but further information can be extracted by means of morphological analysis, providing deforma- tion maps and other specific features. For example, it is possible to map the differences of a prospect with respect to a vertical plane, to measure its inclination or to highlight anomalous deviations from a 1296-2074/$ – see front matter © 2011 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.culher.2011.09.004