This paper examines the survey of tall buildings in an emergency context like in the case of post-seismic events. The after-earthquake survey has to guarantee time-savings, high precision and security during the operational stages. The main goal is to optimize the application of methodologies based on acquisition and automatic elaborations of photogrammetric data even with the use of Unmanned Aerial Vehicle (UAV) systems in order to provide fast and low cost operations. The suggested methods integrate new technologies with commonly used technologies like TLS and topographic acquisition. The value of the photogrammetric application is demonstrated by a test case, based on the comparison of acquisition, calibration and 3D modeling results in case of use of a laser scanner, metric camera and amateur reflex camera. The test would help us to demonstrate the efficiency of image based methods in the acquisition of complex architecture. The case study is Santa Barbara Bell tower in Mantua. The applied survey solution allows a complete 3D database of the complex architectural structure to be obtained for the extraction of all the information needed for significant intervention. This demonstrates the applicability of the photogrammetry using UAV for the survey of vertical structures, complex buildings and difficult accessible architectural parts, providing high precision results.

Starting from our experience in this domain, we discuss some fundamental concepts about the potentialities of the virtual reconstructions of cultural sites inside museums, with a specific focus on the communication needs, the design, the combination of media, the interaction interfaces, and the embodiment. We conceive a virtual reconstruction as a digital ecosystem, whose main peculiarities are (1) 3D reconstruction, (2) inclusivity, and (3) interactivity. A virtual reconstruction, in a wide sense, should integrate different levels of visualization, both realistic and symbolic; 3D models; metadata; storytelling; behaviors; and tools of visualization and interaction, in order to “reconstruct” and communicate a cultural context, an ecosystem where all the information is integrated. Despite the great advancements of the last years in the digitization process, computer graphics techniques, and archiving strategies, a basic limit of most of virtual museums is that they do not fire up the attention and the involvement of the public: they lack stimulating activities for visitors, narratives metaphors, and emotional impact. The interaction interfaces are not always simple to understand and to control in a few minutes, and they can generate a sense of frustration that causes users to abandon the application after a short and superficial approach. No gap should exist between knowledge and communication. But how can we translate the complexity of the knowledge in appealing to users and into simple applications that fit with the public's need? This article focuses on some communication rules and criteria that are often considered of minor importance by the researchers working in the field of digital cultural heritage but that are really essential to cultural transmission, especially inside museums. We believe that a stronger collaboration between research institutions and museums and among different disciplines would be recommended. Given this premise, we present the Etruscanning EU project, developed in 2011--2013, focused on the virtual reconstruction of two important Etruscan tombs of the Orientalizing period: the Regolini-Galassi tomb in Cerveteri and the tomb n.5 of Monte Michele in Veii.

Modeling of Cultural Heritage in a BIM environment, and in general of existing buildings, requires special attention because there are two diametrically opposed possibilities. On the one hand the attempt is to realize a very complex and accurate model, in order to provide the most comprehensive representation of the architecture as possible. The opposite position leads to build a very schematic and symbolic model of as-built architecture. It is not easy to determine which is the right balance between these two attitudes because each architecture requires a personalized approach and not standards. It's, however, necessary to find rules to figure out which items are represented, what is the minimum level of detail to consider adequate and how to deal with alterations from simple and linear geometries. These two facing possibilities deal with different goals and tools. In the field of restoration or planned conservation, that is the most common approach for existing buildings, the attention focuses on the exceptions and particularities of each architecture: the important aspect is to understand and describe exactly each part as a singularity (as it is). In this context it is very difficult to find a standard or a common solution. The first possibility of modelling seems to be very close to this approach, but it clashes with two important aspects. A first problem concerns the modelling software. Usually commercial BIM modelling software doesn’t allow to realize very complex and high detailed solutions. They prefer working with predefined families and try to categorize each element in standard solution. The possibility to build new families is expected, but it often requires a lot of time. The second difficulty is the real efficiency of such an accurate model. In fact, it could be very difficult to link external elements to the model or use it in many traditional BIM applications. In this paper, we suggest another possible approach that represents the first result of a research about the modelling of Cultural Heritage for BIM application. The proposed solution aims to give as much information as possible about the architecture, and, at the same time, to guarantee a higher efficiency. In this case we considered commercial BIM software like Revit or Archicad. They are the most widespread and well-known software BIM oriented and they also allow the use of their embedded database structure. The core of our solution is to describe the architecture not only by a 3D model but also by the representation of the reliability of the accuracy of the model itself. In this way we try to combine the necessity of working with commercial software, in which it is difficult to be very accurate, and the information about the real object. In historical complex architecture, for example, it is very difficult to find a straight and planar wall. It is quite difficult, or at least time consuming, to model that kind of wall with high accuracy. But it is possible to represent the real wall by a schematic wall with a false color map which describes where the 3D model is well fitting and where there are some differences. In this way we don’t lose any information but, at the same time, we have a very usable BIM model.

Keywords: HBIM, modelling, Cultural Heritage, complex architecture The Basilica of San Marco is a singular case in the field of Cultural heritage, as it constitutes a construction site always active for the maintenance and preservation of the basilica itself. The continuous intervention of conservation, due to the particular environmental conditions of Venice and the opening to the public, together with the complexity of the building itself, imposes the need to identify an optimized management system. For this reason, in 2013 the Procurator of St. Marco Basilica commissioned the construction of a 3D model of the Basilica to be used for the creation of a BIM. The model must meet the required precision of the scale of 1:50, and should also include, in addition to the geometric description, a description of the mosaic and marble surfaces of the basilica through high resolution orthophoto which are essential for the restoration of the mosaics. The complexity of the church and the large and continuous flow of public led to work in non-optimal conditions especially for the acquisition stage. The basilica has certain peculiarities that led to some important choices, for example the use of photogrammetry instead of laser scanning technique. The same technique was preferred also by the need to realize, in addition to the geometric model, high-resolution orthophotos of marbles and mosaic surfaces. The modelling of the basilica has highlighted a number of problems related to the building features. The basilica, indeed, is the result of the juxtaposition of elements (capitals, columns) with different origin, which therefore cannot be standardized in special libraries. Moreover, especially in the extensive mosaic areas, there are not edges that characterize the architecture, but only beveled surfaces. This has resulted in a change also in the modeling paradigm with the need to identify alternative systems even for the construction of simple elements. Therefore, we decided to model using NURBS since it is the method that allows greater adherence to reality and, at the same time, a model with acceptable dimensions in terms of navigation and usability. Only the most sculptural pieces such as capitals and statues have been replaced by mesh models. As we were interested in different elaborations, the results of this work are a geometric NURBS model for the subsequent insertion into BIM environment, with the possibility of extracting two-dimensional drawings such as plans and sections, a mesh model with low resolution textures for online navigation and high resolution orthophotos. The survey work and modeling has been almost completed for the interior of the basilica whereas only the external remains to be acquired and modeled. For the management of the entire work it was decided to use the data organization system already used by the Politecnico di Milano for the Duomo di Milano. The BIM3DSURVEY system will be essential not only to manage the finished model, but it has been very useful also during the construction phase because it allows us to divide the entire work into more work units. However, this system required some changes to meet the peculiarity of this BIM, in particular the need to append and link the orthophotos to real surfaces, in order to use the model also as a spatial index for the images.

To manage the historic built heritage, it is of fundamental importance to fully understand the urban area under study, so that all its characteristics and critical issues related to historical conformation, stratification, and transformations can be better understood and described. Geometric surveying allows a deeper investigation of these characteristics through analytical investigation in support of urban planning theories as well. To date, geomatics provides various tools and techniques to meet the above-mentioned needs, and mobile mapping system (MMS) is a technology that can survey large areas in a short time, with good results in terms of density, accuracy, and coverage of the data. In this context, the article aims to verify whether this approach can also be useful in the complex and stratified reality of the historic urban context. The case analyzed—the historical center of Sabbioneta—presents some criticalities found in many urban centers of historical layout. Examples are narrow streets inserted in an urban context with multi-story buildings and consequent difficulty in receiving the GNSS signal and difficulty in following general MMS survey guidelines (trajectories with closed loops, wide radius curves). The analysis presented, relating to a survey carried out with Leica Pegasus:Two instrumentation, in addition to describing the strategies used to properly develop the survey, aims to analyze the resulting datum by discussing its possibilities for use in urban modeling, for cartographic or three-dimensional information modeling purposes. Particular attention is paid to assessing whether the quality of the data (accuracy, density) is suitable for the urban scale. Finally, an analysis of the data obtained from MMS was made with the geographic-topographic database (DBGT), in a GIS (Geographic Information System) environment, to check the possibilities of use and integration between the two models.

The Italian legislation on Remote Pilot Aircraft Systems (SAPR: Sistema Areomobile a Pilotaggio Remoto), as in 2012, regulates the use of drones in controlled and uncontrolled airspace. In 2016, the regulation introduced simplified procedures for the use of ultra-light drones. These instruments are particularly widespread in the field of Cultural Heritage survey. In fact, according to the Italian regulations currently in force it is possible to pilot a drone of less than 300 grams without the need of a flight license and without a specific training course and medical examination and it is not required a special permit to fly in populates areas (although without flying over groups of people). Another possible explanation is the limited cost of these aircrafts and their easy availability on the market, both on the shelves of all electronic shops and in online stores.Following the boom of drones under 300 g, and considering the new European regulations also pay particular attention to a similar segment of Unmanned Aerial Vehicle (UAV) (in the future for aircraft under 250 g), it is important to evaluate the results that can be obtained through these small instruments and above all to evaluate which are the fields of application compatible with the technical limitations imposed by the need to lighten the components onboard (think in particular of the sensors of digital cameras).The purpose of the study is linked to the documentation of Cultural Heritage, in particular, we want to investigate the quality and metric reliability of photogrammetric surveys carried out through ultra-light drone images. Some application of UAV photogrammetry by ultra-light drones are showed in this paper and they deal with archaeological and architectural survey.