Archaeological site monitoring: UAV photogrammetry can be an answer

During archaeological excavations it is important to monitor the new excavated areas and findings day by day in order to be able to plan future excavation activities. At present, this daily activity is usually performed by using total stations, which survey the changes of the archaeological site: the surveyors are asked to produce day by day draft plans and sections which allow archaeologists to plan their future activities. The survey is realized during the excavations or just at the end of every working day and drawings have to be produced as soon as possible in order to allow the comprehension of the work done and to plan the activities for the following day. By using this technique, all the measurements, even those not necessary for the day after, have to be acquired in order to avoid a ‘loss of memory'. A possible alternative to this traditional approach is aerial photogrammetry, if the images can be acquired quickly and at a taken distance able to guarantee the necessary accuracy of a few centimeters. Today the use of UAVs (Unmanned Aerial Vehicles) can be considered a proven technology able to acquire images at distances ranging from 4 m up to 20 m: and therefore as a possible monitoring system to provide the necessary information to the archaeologists day by day. The control network, usually present at each archaeological site, can give the stable control points useful for orienting a photogrammetric block acquired by using an UAV equipped with a calibrated digital camera and a navigation control system able to drive the aircraft following a pre-planned flight scheme. Modern digital photogrammetric software can solve for the block orientation and generate a DSM automatically, allowing rapid orthophoto generation and the possibility of producing sections and plans. The present paper describes a low cost UAV system realized by the research group of the Politecnico di Torino and tested on a Roman villa archaeological site located in Aquileia (Italy), a well-known UNESCO WHL site. The results of automatic orientation and orthophoto production are described in terms of their accuracy and the completeness of information guaranteed for archaeological site excavation managemen

New instruments and technologies for Cultural Heritage survey: full integration between point clouds and digital photogrammetry

In the last years the Geomatic Research Group of the Politecnico di Torino faced some new research topics about new instruments for point cloud generation (e.g. Time of Flight cameras) and strong integration between multi-image matching techniques and 3D Point Cloud information in order to solve the ambiguities of the already known matching algorithms. ToF cameras can be a good low cost alternative to LiDAR instruments for the generation of precise and accurate point clouds: up to now the application range is still limited but in a near future they will be able to satisfy the most part of the Cultural Heritage metric survey requirements. On the other hand multi-image matching techniques with a correct and deep integration of the point cloud information can give the correct solution for an "intelligent" survey of the geometric object break-lines, which are the correct starting point for a complete survey. These two research topics are strictly connected to a modern Cultural Heritage 3D survey approach. In this paper after a short analysis of the achieved results, an alternative possible scenario for the development of the metric survey approach inside the wider topic of Cultural Heritage Documentation is reporte

UAV multi-image matching approach for architectural survey in complex environments

Photogrammetric survey using UAV shows nowadays some aspects, especially related to the optimization of the operative workflows and best practices, that still need to be investigated. This work concerns the use of a small UAV for the documentation of an historical architectural complex, in which space constraints arises. The adoption of a rapid mapping workflow using frames extracted from videos is discussed, together with the exploitation of an automatic procedure for the acquisition of 360° shots, used for ensuring the minimum required overlap for a reliable and accurate image orientation

SfM for Orthophoto Generation: A Winning Approach for Cultural Heritage Knowledge

3D detailed models derived from digital survey techniques have increasingly developed and focused in many field of application. The high detailed content and accuracy of such models make them so attractive and usable for large sets of purposes in Cultural Heritage. The present paper focuses on one of the main techniques used nowadays for Cultural Heritage survey and documentation: the image matching approach or Structure from Motion (SfM) technique. According to the low cost nature and the rich content of derivable information, these techniques are extremely strategic in poor available resources sectors such as Cultural Heritage documentation. <br><br> After an overview of the employed algorithms and used approaches of SfM computer vision based techniques, the paper is focused in a critical analysis of the strategy used by two common employed software: the commercial suite Agisoft Photoscan and the open source tool MicMac realized by IGN France. The experimental section is focused on the description of applied tests (from RPAS data to terrestrial acquisitions), purposed to compare different solutions in various featured study cases. Finally, the accuracy assessment of the achieved products is compared and analyzed according to the strategy employed by the studied software

TLS data for architectural 2D representation and 3D modeling. Different approaches tested in the case of San Giovanni in Saluzzo (Cn) Italy

TLS (Terrestrial Laser Scanners) data today represents one of the most attractive ways to face the metric survey of an architectural object. When a restoration project is needed not many restorers are used to managing 3D models and traditional graphic results such as plans and sections are usually required. The paper defines a correct balance between the use of traditional (manual and total station) and TLS techniques in order to satisfy the usual requirements for the metric survey of an architectural object in order to obtain a complete 2D documentation of the San Giovanni Church in Saluzzo (Cn) - Italy that would be used for the restoration both of the decorative apparatus and of the structure of the church. Furthermore using the acquired 3D data some tests on commercial and open-source software for 3D modeling purpose are realised. The paper deals first of all with the followed methodology for the 2D documentation starting from 3D data. Moreover an analysis and a comparison between different software packages for the 3D modeling phase is reporte

WebGIS tools to disseminate archaeological landscape memory

This research works is providing digital tools for knowledge, fruition, communication and promotion of built heritage, in a framework of landscape heritage valorisation. The application could be placed in a framework of established methods within a field of study, increased in the recent years, aimed at promoting the integration of processing digital methods and information dissemination. The central aim of this work is to obtain and manage spatial information that can be helpful to represent and promote the peculiar features of the Archaeological Mine Park of San Silvestro, using proper acquiring techniques derived from Geomatics, regional data retrieved from the spatial data infrastructures and archaeological data. The use of innovative rapid mapping methods, the generation of orthophotos and DTMs-DEMs (Digital Terrain Model-Digital Elevation Model), the harmonization of different sources, scales and reference system data, the integration of datasets that synthesizes the studies and the excavation activities of the parks over the years, have provided a large spatially referenced archive that testifies the historical richness of the site. Those information, if communicated via WebGIS, can help to highlight the memory values of a territory. In addition to the opportunity to integrate multi-content and multi-source spatial data into a single platform, the Web-GIS project uses applications and solutions in order to promote the preservation of the memory of the territory and the historical identity of the place. It is widely known that reaching the valorisation of a cultural heritage is possible only establishing and organizing stable structure, resources and networks

3D MODELING OF THE MICHIGAN TECH HUSKY STATUE USING A CLOSE-RANGE PHOTOGRAMMETRIC APPROACH

In fall of 2014 a three meter tall statue of a Husky was erected on the campus of Michigan Technological University. The Husky is Michigan Tech’s mascot and a symbol of the snowy frozen north woods in which the campus is located. The statue was conceived and funded by the universities alumni association and by donors who paid to have bricks engraved around the statue. A team of graduate students in the Integrated Geospatial Technology program came up with the idea of using photogrammetry to model the statue in order to perform accurate measurements of area and volume. This initial idea was taken another step by the need for a course project in close-range photogrammetry and a desire by the alumni association to publish a 3D model of the statue online. This study tests two software packages that can be used to create a photogrammetric model of the statue. A final data set has yet to be collected; however initial attempts have been successful in creating a highly detailed digital model. With the weather clearing and the snow melting work will continue on this project

Impiego di aerei ultraleggeri e camere di medio formato per la fotogrammetria aerea a grande scala

Nella fotogrammetria a grande e grandissima scala l'acquisizione dei dati primari, immagini metriche e parametri di orientamento, può essere convenientemente effettuata anche con mezzi di basso o medio costo alla portata di piccole aziende. Tale possibilità è dovuta particolarmente all'attuale disponibilità di piattaforme aeree a basso costo, con o senza pilota, largamente sperimentate in questi ultimi anni nel campo del rilievo dell'archeologia e del monitoraggio delle emergenze ambientali. Qui si è voluto valutare l'impiego sperimentale di aerei ultraleggeri, piuttosto diffuso all'estero, in unione con camere digitali di buona risoluzione, ma di costo relativamente contenuto. In particolare si è valutata la possibilità di realizzare la cartografia a grande scala di piccoli centri abitati in zona collinare, realizzando una carta dei tetti in scala 1:1000 di una borgata piemontese. Al costo molto contenuto dell'aereo ultraleggero e della camera digitale fa purtroppo contrasto la normativa vigente che ne impedisce l'impiego a fini produttiv

UAS photogrammetry and SLAM for the HBIM model of the Montanaro Belltower

Uncrewed Aerial Systems (UAS) are nowadays a consolidated technique for the 3D metric documentation of Built Heritage. Nevertheless, a complete survey of complex heritage assets still requires the integration of different techniques, using a multisensor and multiscale approach. The research presented in this contribution relates a documentation experience achieved on a complex heritage asset, from multisensor data acquisition, through data processing and validation to the phase of 3D modeling and HBIM creation

A COMPARISON AMONG DIFFERENT OPTIMIZATION LEVELS IN 3D MULTI-SENSOR MODELS. A TEST CASE IN EMERGENCY CONTEXT: 2016 ITALIAN EARTHQUAKE

In sudden emergency contexts that affect urban centres and built heritage, the latest Geomatics technique solutions must enable the demands of damage documentation, risk assessment, management and data sharing as efficiently as possible, in relation to the danger condition, to the accessibility constraints of areas and to the tight deadlines needs. In recent times, Unmanned Vehicle System (UAV) equipped with cameras are more and more involved in aerial survey and reconnaissance missions, and they are behaving in a very cost-effective way in the direction of 3D documentation and preliminary damage assessment. More and more UAV equipment with low-cost sensors must become, in the future, suitable in every situation of documentation, but above all in damages and uncertainty frameworks. Rapidity in acquisition times and low-cost sensors are challenging marks, and they could be taken into consideration maybe with time spending processing. The paper will analyze and try to classify the information content in 3D aerial and terrestrial models and the importance of metric and non-metric withdrawable information that should be suitable for further uses, as the structural analysis one. The test area is an experience of Team Direct from Politecnico di Torino in centre Italy, where a strong earthquake occurred in August 2016. This study is carried out on a stand-alone damaged building in Pescara del Tronto (AP), with a multi-sensor 3D survey. The aim is to evaluate the contribution of terrestrial and aerial quick documentation by a SLAM based LiDAR and a camera equipped multirotor UAV, for a first reconnaissance inspection and modelling in terms of level of details, metric and non-metric information