This paper focuses on the processing and study of 3D models obtained from images captured by an unmanned aerial vehicle (UAV). In particular, we wanted to study the accuracy gains achieved in the surveying and the measurement, such as height, area, and volume, of the dimensions of the buildings in the 3D models obtained with both nadir and oblique UAV flights. These latter types of flights are particularly suitable for the 3D modeling of cities or urban agglomerations, where it is important to achieve a complete building reconstruction, including façades and footprints of buildings. For this purpose, several UAV surveys with both nadir and oblique axes were performed. The nadir flight acquired images over an area of about 3.5 hectares containing 30 buildings, while the second flight, performed with both a nadir camera and an oblique camera, was conducted on a single building. The images from the flights were processed with Photoscan software by Agisoft and with Pix4D, studying their different potentialities and functionality. The results were compared with the data from the 1:2000 scale Geotopographic Database (DBGT), with the results of a Global Navigation Satellite System (GNSS) survey and with 3D model from the Terrestrial Laser Scanner (TLS) survey. The obtained results have shown that oblique UAV flights increase the achievable accuracy both in terms of the number of points in a point cloud, and in the in measurements taken on the 3D models, with respect to the limited cost, and at the increase in time for surveying and image processing.

The field of Cultural Heritage has inspired, in the course of last few years, an interest more and more important on behalf of scientific community that deals to survey. The idea that knowledge of a site doesn't apply only to its history but must necessarily include its characteristics of position, shape and geometry, is gathering pace. In Geomatic science the field of cultural heritage benefits to an integrated approach of techniques and different technologies. Every cultural site in fact, is a case in itself, with its own characteristics, problems and specificness. Current techniques offer opportunity to achieve new ways of representation and visualization of cultural site, with the aim of a better metric description. This techniques are powerful tools for analysis of sites and supports to activity of reconstruction and repair. Biggest expectations in this field is laser three-dimensional scanning technique; a system which is able to operate in a methodical way in speed of acquisition and in possibility to access data in real time. Documentation and filing of state of a monument or site is essential in case of reconstruction or conservative project. Possibility to detect very complex geometries with great accuracy allows an in depth study of constructive techniques, making analysis of geometrical details easier which is, with traditional techniques, difficult to achieve. Biggest problems about use of laser scanner survey are graphic outputs for restorers and architects, in fact they often don't know real potential of this techniques, methodologies and functionalities and they expect traditional outputs such as floor plans, cross sections and front elevation of cultural asset. Present study is focused on finding a workflow to support activity of study, restoration and conservative project of cultural heritage, extracting automatically (or with a limited manual operation) graphic outputs from laser scanner survey. Some procedure was tested on two case study the Siviller Castle (XV century), situated in Villasor, a city near Cagliari (Sardinia, Italy) and the tower bell of Mores, near Sassari (Sardinia, Italy). The cultural sites were surveyed with laser scanner Focus 3D by Faro and to process clouds point we were used the JRC 3D Reconstructor software * Corresponding author. This is useful to know for communication with the appropriate person in cases with more than one author.

Dense point clouds acquired from Terrestrial Laser Scanners (TLS) have proved to be effective for structural deformation assessment. In the last decade, many researchers have defined methodology and workflow in order to compare different point clouds, with respect to each other or to a known model, assessing the potentialities and limits of this technique. Currently, dense point clouds can be obtained by Close-Range Photogrammetry (CRP) based on a Structure from Motion (SfM) algorithm. This work reports on a comparison between the TLS technique and the Close-Range Photogrammetry using the Structure from Motion algorithm. The analysis of two Reinforced Concrete (RC) beams tested under four-points bending loading is presented. In order to measure displacement distributions, point clouds at different beam loading states were acquired and compared. A description of the instrumentation used and the experimental environment, along with a comprehensive report on the calculations and results obtained is reported. Two kinds of point clouds comparison were investigated: Mesh to mesh and modeling with geometric primitives. The comparison between the mesh to mesh (m2m) approach and the modeling (m) one showed that the latter leads to significantly better results for both TLS and CRP. The results obtained with the TLS for both m2m and m methodologies present a Root Mean Square (RMS) levels below 1 mm, while the CRP method yields to an RMS level of a few millimeters for m2m, and of 1 mm for m.

ABSTRACT:As is well known, Italy's very consistent buildings stock has become the major field for real estate investments and for the related projects and actions. It is a heritage that is often barely known and extremely complex, whose management has until now been addressed in a rather casual and uninformed manner, with unsatisfactory and sometimes disastrous outcomes. The situation is worse in the case of buildings of particular historical, artistic and architectural value so frequent within the heritage of our country. This paper shows the findings of an ongoing research which is aimed at structuring the cognitive process and assessing enhancement and re-functionalisation scenarios of our historical and architectural heritage through the use and integration of information systems such as BIM and the GIS. The work led to the development of a workflow able to integrate the contribution of the HBIM and GIS methodologies in the structuring and management of a wide range of digital data and information useful for its management. The research, focused on "La Gran Torre di Oristano, is aimed at creating the best conditions for an integrated and multidisciplinary strategy of requalification and refunctionalisation of historical and architectural heritage.

The possibility to have results very quickly after, or even during, the collection of electromagnetic data would be important, not only for quality check purposes, but also for adjusting the location of the proposed flight lines during an airborne time-domain acquisition. This kind of readiness could have a large impact in terms of optimization of the Value of Information of the measurements to be acquired. In addition, the importance of having fast tools for retrieving resistivity models from airborne time-domain data is demonstrated by the fact that Conductivity-Depth Imaging methodologies are still the standard in mineral exploration. In fact, they are extremely computationally efficient, and, at the same time, they preserve a very high lateral resolution. For these reasons, they are often preferred to inversion strategies even if the latter approaches are generally more accurate in terms of proper reconstruction of the depth of the targets and of reliable retrieval of true resistivity values of the subsurface. In this research, we discuss a novel approach, based on neural network techniques, capable of retrieving resistivity models with a quality comparable with the inversion strategy, but in a fraction of the time. We demonstrate the advantages of the proposed novel approach on synthetic and field datasets.

Abstract:The paper presents a spatial information system (SIS) developed in the research project, "Tecniche murarie tradizionali: conoscenza per la conservazione ed il miglioramento prestazionale" (Traditional building techniques: from knowledge to conservation and performance improvement), with the aim of archiving and managing the data derived from the project. The research project has the purpose of studying the building techniques of the 13th-18th centuries in the Sardinia region (Italy) for their knowledge, conservation, and promotion. The research is founded on a multidisciplinary approach involving several specialists integrating their expertise and providing their input to the knowledge of the dimensional, technical constructive, mensiochronological, materials, physical-mechanical, and energy performance features. This multidisciplinary approach is used to define the peculiarities and behavior of the examined structures, including their performance levels, and then direct the interventions toward innovative, mindful, and ethically correct solutions. The management of the huge amount of data produced during the research required the building of a SIS composed of a geodatabase connected to a GIS and a WebGIS through a Web Map Service (WMS). The entire infrastructure is developed and implemented using open source software components, and will make the research data available to the scientific and professional communities, both for further development and for technical uses. As of today, we surveyed and archived more than 500 buildings belonging to the Sardinia region architectural heritage, and classified them into four main macro categories: defensive architectures, religious architectures, residential architectures, and industrial architectures.

<p><strong>Abstract.</strong> In the photogrammetric process of the 3D reconstruction of an object or a building, multi-image orientation is one of the most important tasks that often include simultaneous camera calibration. The accuracy of image orientation and camera calibration significantly affects the quality and accuracy of all subsequent photogrammetric processes, such as determining the spatial coordinates of individual points or 3D modeling. In the context of artificial vision, the full-field analysis procedure is used, which leads to the so-called Strcture from Motion (SfM), which includes the simultaneous determination of the camera's internal and external orientation parameters and the 3D model. The procedures were designed and developed by means of a photogrammetric system, but the greatest development and innovation of these procedures originated from the computer vision from the late 90s, together with the SfM method. The reconstructions on this method have been useful for visualization purposes and not for photogrammetry and mapping. Thanks to advances in computer technology and computer performance, a large number of images can be automatically oriented in a coordinate system arbitrarily defined by different algorithms, often available in open source software (VisualSFM, Bundler, PMVS2, CMVS, etc.) or in the form of Web services (Microsoft Photosynth, Autodesk 123D Catch, My3DScanner, etc.). However, it is important to obtain an assessment of the accuracy and reliability of these automated procedures. This paper presents the results obtained from the dome low close range photogrammetric surveys and processed with some open source software using the Structure from Motion approach: VisualSfM, OpenDroneMap (ODM) and Regard3D. Photogrammetric surveys have also been processed with the Photoscan commercial software by Agisoft.</p><p>For the photogrammetric survey we used the digital camera Canon EOS M3 (24.2 Megapixel, pixel size 3.72&amp;thinsp;mm). We also surveyed the dome with the Faro Focus 3D TLS. Only one scan was carried out, from ground level, at a resolution setting of &amp;frac14; with 3x quality, corresponding to a resolution of 7&amp;thinsp;mm / 10&amp;thinsp;m. Both TLS point cloud and Photoscan point cloud were used as a reference to validate the point clouds coming from VisualSFM, OpenDroneMap and Regards3D. The validation was done using the Cloud Compare open source software.</p>

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