VERY HIGH-RESOLUTION 3D SURVEYING AND MODELLING EXPERIENCES IN CIVIL ENGINEERING APPLICATIONS

Abstract. In this paper some experiences in 3D modelling of objects with very high-resolution are described, carried out by the DICAM Geomatics group of the University of Bologna in multi-disciplinary contexts within the field of the Civil Engineering. In all the addressed case studies the main aim is the generation of a 3D model of the surface at a sub-millimetric scale, allowing a very accurate characterization of the surface geometry, useful for different purposes. 3D scanning and Structure from Motion photogrammetry have been used to generate the 3D models. In the paper the encountered problems and the adopted solutions in data surveying and processing are underlined, also discussing the added value of very high-resolution 3D modelling in multi-disciplinary activities

VERY HIGH-RESOLUTION 3D SURVEYING AND MODELLING EXPERIENCES IN CIVIL ENGINEERING APPLICATIONS

In this paper some experiences in 3D modelling of objects with very high-resolution are described, carried out by the DICAM Geomatics group of the University of Bologna in multi-disciplinary contexts within the field of the Civil Engineering. In all the addressed case studies the main aim is the generation of a 3D model of the surface at a sub-millimetric scale, allowing a very accurate characterization of the surface geometry, useful for different purposes. 3D scanning and Structure from Motion photogrammetry have been used to generate the 3D models. In the paper the encountered problems and the adopted solutions in data surveying and processing are underlined, also discussing the added value of very high-resolution 3D modelling in multi-disciplinary activities

Historical Photogrammetry and Terrestrial Laser Scanning for the 3d Virtual Reconstruction of Destroyed Structures: a Case Study in Italy

The current dramatic episodes of destruction of archaeological sites have again highlighted the problem of the safeguarding the threatened heritage and, if possible, recovering those damaged by all the armed conflicts of the past. The historical photogrammetry offers the possibility to recover a posteriori the geometrical and material properties of destroyed structures, reconstructing their 3D model to document, study and maintain their memory, until to support their real anastylosis. The presented work is about the 3D reconstruction of the civic tower of the little town of Sant'Alberto, near the city of Ravenna, Italy. The tower, as a symbol of resistance and pride of the town's population, was destroyed in December 1944 by German troops in retaliation, when they were forced to leave the area. A city committee has subsequently collected all the historical evidence concerning the tower, including a series of photographic images that can be used for the photogrammetric reconstruction; the images calibration and orientation have been solved using the geometric information derived by a terrestrial laser scanner survey realized in the area where the tower was originally located. Despite the scarcity and very poor quality of the available images, the conducted photogrammetric procedure has allowed a complete and qualitatively satisfying object reconstruction, also thanks to the use of geometric constraint tools offered by the chosen software. The integration between the obtained model of the old tower and the 3D TLS survey of the square made it possible to reconstruct the ancient situation of the area

Seeing into the past: integrating 3D documentation and non-invasive prospecting methods for the analysis, understanding and reconstruction of the ancient Pompeii. The case of the House of Obellio Firmo (IX, 14)

In 2015 the Department of History and Cultures of the Bologna University took part in the Grande Progetto Pompei - Piano della Conoscenza, with the task of providing a modern and complete documentation of the so-called Lotto 3 in Pompeii. The new survey was carried out by means of integrated innovative diagnostic survey techniques in order to provide a total documentary research of the whole sector. In 2016 a new project was started in agreement with the competent Superintendency, and focused on the study and preservation of the House of Obellio Firmo, included in the Lotto 3 of the Roman city. The new research contemplates an in-depth analysis of the building, employing systematic laser scanning and photogrammetry methods to generate an accurate 3D model of the house. This model is going to constitute the starting point for the further analysis of the wall stratigraphies and for the mapping and monitoring of the structures’ state of decay. The full-scale analytical documentation of the building also includes a detailed geophysical mapping of all the accessible domestic spaces, by using the ground penetrating radar technique. The preliminary results achieved by the non-invasive prospecting survey, integrated with the analysis of the surviving walls and building techniques, supply valid information for the archaeological interpretation of the house’s history. In order to allow the management and sharing of the information collected, the data are going to be organised within a building information model (BIM) with a triple objective: the reconstruction of a fragment of the ancient urban landscape in Pompeii during the oldest phase, with particular attention directed to the Samnitic period; the outlining of a precise strategy of intervention for the restoration and preservation of the House of Obellio Firmo; the re-opening of the building to sightseeing tours and its restitution to public use

3D DIGITISATION IN CULTURAL HERITAGE KNOWLEDGE AND PRESERVATION: THE CASE OF THE NEPTUNE STATUE IN BOLOGNA AND ITS ARCHETYPE

Abstract. In the field of Cultural Heritage, the availability of a complete, detailed and photo-realistic 3D model of the objects of interest permits to describe all the aspects related to geometry, colours and materials, as well as the work techniques and the decay state. Besides, it offers multiple possibilities for the documentation, the analysis and the study.This paper describes the experience, carried out by the DICAM Geomatics group of the University of Bologna, about the 3D digitisation of two important statues of Neptune, by means of the integration of 3D image-based and range-based techniques. The two artworks, both realized by the sculptor Giambologna, are the big bronze statue of the god adorning the homonymous fountain, one of the most symbolic monuments of the city of Bologna, and its archetype, exhibited in one of the civic museums.The obtained 3D models, beyond the important function of documentation, knowledge and preservation of the two objects, also permit a comparison between the small archetype, conveniently scaled, and the big final statue. In the manuscript all the surveying and data processing operations concerning the objects digitisation are described. Particular attention is paid to the problems related to the scale of the archetype and the comparison between the two obtained 3D models, with the aim to evaluate and represent the occurred changes

Qualitative and quantitative photogrammetric techniques for multi-temporal landslide analysis

The results of two survey methods, geological photointerpretation and historical photogrammetry, are compared in order to evaluate the temporal evolution of a unstable slope located in the Tuscan-Emilian Apennines (Italy). Historical aerial photos of the area, derived from photogrammetric surveys conducted in 1954 (scale 1:60000), in 1971 (scale 1:20000), and in 1976 (scale 1:17000) were available. A photogrammetric flight was further conducted in 2000, at a scale of 1:4400, with a traditional GPS ground survey support. First, the results of photographic analysis with the photointerpretation method are presented: the landslides are described from a geological point of view, showing its temporal evolution. To quantitatively assess the landslide movements, Digital Terrain Models were generated by means of an analytical plotter and a digital photogrammetric workstation, with semi-automatic and automatic procedures. To generate these products, it was necessary to solve problems related to a lack of data concerning the aerial cameras used for the historical flights (internal orientation) and the difficulty identifying control points on the photos in order to define the external orientation. An unconventional photogrammetric methodology, based on identification of homologous points in zones considered outside the landslide area, has been there developed and tested to insert the various surveys into a single reference system

Metric documentation of cultural heritage: Research directions from the Italian gamher project

GAMHer is a collaborative project that aims at exploiting and validating Geomatics algorithms, methodologies and procedures in the framework of new European regulations, which require a more extensive and productive use of digital information, as requested by the Digital Agenda for Europe as one of the seven pillars of the Europe 2020 Strategy. To this aim, GAMHer focuses on the need of a certified accuracy for surveying and monitoring projects with photogrammetry and laser scanning technologies, especially when used in a multiscale approach for landscape and built heritage documentation, conservation, and management. The approach used follows a multi-LoD (level of detail) transition that exploits GIS systems at the landscape scale, BIM technology and "point cloud based" 3d modelling for the scale of the building, and an innovative BIM/GIS integrated approach to foster innovation, promote users' collaboration and encourage communication between users. The outcomes of GAMHer are not intended to be used only by a community of Geomatics specialists, but also by a heterogeneous user community that exploit images and laser scans in their professional activities

Back analysis of the 2014 San Leo Landslide using combined terrestrial laser scanning and 3D distinct element modelling

This is the author accepted manuscript. The final version is available from Springer Verlag via http://dx.doi.org/10.1007/s00603-015-0763-5© 2015 Springer-Verlag Wien Landslides of the lateral spreading type, involving brittle geological units overlying ductile terrains, are a common occurrence in the sandstone and limestone plateaux of the northern Apennines of Italy. The edges of these plateaux are often the location of rapid landslide phenomena, such as rock slides, rock falls and topples. In this paper, we present a back analysis of a recent landslide (February 2014), involving the north-eastern sector of the San Leo rock slab (northern Apennines, Emilia-Romagna Region) which is a representative example of this type of phenomena. The aquifer hosted in the fractured slab, due to its relatively higher secondary permeability in comparison to the lower clayey units leads to the development of perennial and ephemeral springs at the contact between the two units. The related piping erosion phenomena, together with slope processes in the clay-shales have led to the progressive undermining of the slab, eventually predisposing large-scale landslides. Stability analyses were conducted coupling terrestrial laser scanning (TLS) and distinct element methods (DEMs). TLS point clouds were analysed to determine the pre- and post-failure geometry, the extension of the detachment area and the joint network characteristics. The block dimensions in the landslide deposit were mapped and used to infer the spacing of the discontinuities for insertion into the numerical model. Three-dimensional distinct element simulations were conducted, with and without undermining of the rock slab. The analyses allowed an assessment of the role of the undermining, together with the presence of an almost vertical joint set, striking sub-parallel to the cliff orientation, on the development of the slope instability processes. Based on the TLS and on the numerical simulation results, an interpretation of the landslide mechanism is proposed

HIGH RESOLUTION 3D ACQUISITION AND MODELLING IN CULTURAL HERITAGE KNOWLEDGE AND RESTORATION PROJECTS: THE SURVEY OF THE FOUNTAIN OF NEPTUNE IN BOLOGNA

In 2016, the Municipality of Bologna (Italy) has undertaken the restoration of one of the symbols of the entire city, the Fountain of Neptune, in evident state of degradation. The works have touched upon all the aspects of this complex object and the project has seen involved the Municipality and the University of Bologna, the Istituto Superiore per la Conservazione e il Restauro (ISCR) (Rome) and the Visual Computing Lab of the CNR – ISTI (Pisa), in a modern and highly multi-disciplinary approach.One of the key elements of the project was made up by the creation of an information system ad hoc developed to permit, in an innovative, efficient and user-friendly way, the collection, sharing, management and analysis of all the information and data related to diagnostics and restoration actions. The base of the information system is a very detailed 3D model of the monument, realized by means of the most modern techniques for objects 3D modelling (laser scanning, digital photogrammetry and 3D scanning) integrated together with the aim to obtain a photo-textured 3D model characterized by a sub-millimetre precision level in the geometric description and a high perceptive fidelity of colour reproduction.The surveying activities and data processing, performed by the DICAM Geomatics group of the University of Bologna (with the collaboration of the MCM Company of Rome), are described in the paper, with considerations on the problems encountered and the procedures and solutions adopted. The information system has been developed by CNR-ISTI.</p