Keywords: Range based survey, Image based survey, 3D modelling, Archaeology, Virtual Anastylosis This paper is the first report about the development of a methodology for the virtual Anastylosis of elements belonging to an archaeological site, based on the 3d modeling of fragments. This research is the result of the cooperation between Università Roma Tre, Dipartimento di Architettura and Sovrintendenza Capitolina ai Beni Culturali; several 3D survey, modeling, information systems and archaeology experts were involved. The purpose of the research was to study the complex and stratified site of the Arch of Titus at the Circus Maximus aiming, first of all, at completing the existing traditional graphic documentation using cataloguing and survey innovative methodologies, and, secondly, at supporting new proposals for the reconstruction and Anastylosis of the Arch itself. This tested methodology whose fundamental element is the three-dimensional textured model of each fragment, can also be used in other sites and contexts.

The use of terrestrial laser scanners in architectural survey applications has become more and more common. Row data complexity, as given by scanner restitution, leads to several problems about design and 3D-modelling starting from Point Clouds. In this context we present a study on architectural sections and mathematical algorithms for their shape reconstruction, according to known or definite geometrical rules, focusing on shapes of different complexity. Each step of the semi-automatic algorithm has been developed using Mathematica software and CAD, integrating both programs in order to reconstruct a geometrical CAD model of the object. Our study is motivated by the fact that, for architectural survey, most of three dimensional modelling procedures concerning point clouds produce superabundant, but often unnecessary, information and are also very expensive in terms of cpu time using more and more sophisticated hardware and software. On the contrary, it's important to simplify/decimate the point cloud in order to recognize a particular form out of some definite geometric/architectonic shapes. Such a process consists of several steps: first the definition of plane sections and characterization of their architecture; secondly the construction of a continuous plane curve depending on some parameters. In the third step we allow the selection on the curve of some nodal points with given specific characteristics (symmetry, tangency conditions, shadowing exclusion, corners, … ). The fourth and last step is the construction of a best shape defined by the comparison with an abacus of known geometrical elements, such as moulding profiles, leading to a precise architectonical section. The algorithms have been developed and tested in very different situations and are presented in a case study of complex geometries such as some mouldings profiles in the Church of San Carlo alle Quattro Fontane.

Nowadays, the research in the fields of conservation and restoration is focusing on recording large amounts of data and information in order to obtain highly accurate surveys that include most details of constructions. Documenting and surveying are fundamental activities in achieving the successful preservation of cultural heritage, but also in implementing efficient strengthening interventions of structures. The applications of methods and techniques that link the disciplines of geometrical surveys and structural analyses are still fragmented, and further research is necessary to fully transfer site information into structural models. In this article, the authors propose a methodology with which to link different restoration fields, with the aim of highlighting the strengths and weaknesses of the interoperability between surveys (carried out through detailed restitution from point clouds), heritage building information modeling (HBIM), and structural analyses to connect three different disciplines. The goal is to find a synthesis model that brings together historical and geometric characteristics, but also physical–mechanical properties, for a structural evaluation through a finite element model (FEM). The case study of the Escuela José Mariano Méndez is analyzed, an extremely damaged historical adobe building in Santa Ana, the second largest city of El Salvador; it is considered fundamental to the national economy, particularly after the “coffee boom” in the late 1800s. The site, located near the historic center, is also known as “Antigua Escuela de Artes y Oficios” and embodies the architectural traditions of the region, being built in adobe and stone. Roma Tre University and the Secretaría de Cultura de la Presidencia (SECULTURA) are partners in this research project to document and restore the historical and cultural value of this site.

The project involves architecture, archaeology, restoration, graphic documentation and computer imaging. The objective is development of a method for documentation of an architectural feature, based on a three-dimensional model obtained through laser scanning technologies, linked to a database developed in GIS environment. The case study concerns a short section of Rome's Aurelian walls, including the Porta Latina. The city walls are Rome's largest single architectural monument, subject to continuous deterioration, modification and maintenance since their original construction beginning in 271 AD. The documentation system provides a flexible, precise and easily-applied instrument for recording the full appearance, materials, stratification palimpsest and conservation status, in order to identify restoration criteria and intervention priorities, and to monitor and control the use and conservation of the walls over time. The project began with an analysis and documentation campaign integrating direct, traditional recording methods with indirect, topographic instrument and 3D laser scanning recording. These recording systems permitted development of a geographic information system based on three-dimensional modelling of separate, individual elements, linked to a database and related to the various stratigraphic horizons, the construction techniques, the component materials and their state of degradation. The investigations of the extant wall fabric were further compared to historic documentation, from both graphic and descriptive sources. The resulting model constitutes the core of the GIS system for this specific monument. The methodology is notable for its low cost, precision, practicality and thoroughness, and can be applied to the entire Aurelian wall and to other monuments.

This work proposes an integrated survey and a study of the intrados of the dome of the Pantheon in Rome. An actualized architectural survey of the interior of the dome can generate useful material for future studies. The survey has been realized by using in a first stage the digital photogrammetry and in a second stage the three-dimensional laser scan technology. The compared analysis between different methods applied in the same object is useful towards a closer approximation to real dimension. Among several aspects that arise in dealing with the Pantheon this work focuses mainly on the study of the geometry of the inner surface of the dome. The specific goal of the research is to verify the spherical form of the surface and the coffers' distribution. In this sense it takes an important place the extracting data system. In order to realize the analysis it was applied a critical treatment of selected information contained in the point cloud. The use of plan and section drawings connects to the study of three dimensional models. The research is based on the construction of an ideal geometrical model that derives from the theoretical model described in the historical documents. The survey points model, which keeps the irregularities of the actual form, determines the creation of an average sphere, that is a regular model defined by clarifying geometrical laws. The direct comparison between the survey model and the ideal model contributes to the building understanding. It detects irregularities or deformities where they exist, and provides objective and quantifiable data.

The research illustrated below describes the integrated survey method as applied to the Church of St. Thomas of Villanova in Castel Gandolfo, the work of G. L. Bernini. In particular, integration of the various survey methods with 3D modelling to reconstruct all the elements with complex and/or hard to measure geometries has made it possible to obtain an accurate survey model. Comparison of this model with Bernini's original project, based on the analysis of several drawings, has given a clearer view of certain aspects of the design and of Bernini's planning methods.