Optimization of Three-Dimensional (3D) Multi-Sensor Models For Damage Assessment in Emergency Context: Rapid Mapping Experiences in the 2016 Italian Earthquake

Geomatics techniques offer the chance to manage very cost-effective solutions for three-dimensional (3D) modelling, from both the aerial and terrestrial point of view, with the help of range and image-based sensors. 3D spatial data that is based on integrated documentation techniques, featured by a very high-scale and an accurate metric and radiometric information nowadays are proposed here as metric databases that are applicable for assisting the operative fieldwork in the case of rapid mapping strategies. In sudden emergency contexts for damage and risk assessment, the structural consolidation and the security measures operations meet the problem of the danger and accessibility constraints of areas, for the operators, as well as to the tight deadlines needs in first aid. The use of Unmanned Aerial Vehicles (UAVs) equipped with cameras are more and more involved in aerial survey and reconnaissance missions; at the same time, the ZEB1 portable Light Detection and Ranging (LiDAR) mapping solution implemented in handle tools helped by Simultaneous Localization And Mapping (SLAM) algorithms can help for a quick preliminary survey. Both of these approaches that are presented here in the critical context of a post-seismic event, which is Pescara del Tronto (AP), deeply affected by the 2016-2017 earthquake in Central Italy. The Geomatics research group and the Disaster Recovery team (DIRECT—http://areeweb.polito.it/direct/) is working in collaboration with the Remotely Piloted Aircraft Systems (RPAS) group of the Italian Firefighter

Point clouds by SLAM-based mobile mapping systems: accuracy and geometric content validation in multisensor survey and stand-alone acquisition

The paper provides some operative replies to evaluate the effectiveness and the critical issues of the simultaneous localisation and mapping (SLAM)-based mobile mapping system (MMS) called ZEB by GeoSLAM™ https://geoslam.com/technology/. In these last years, this type of handheld 3D mapping technology has increasingly developed the framework of portable solutions for close-range mapping systems that have mainly been devoted to mapping the indoor building spaces of enclosed or underground environments, such as forestry applications and tunnels or mines. The research introduces a set of test datasets related to the documentation of landscape contexts or the 3D modelling of architectural complexes. These datasets are used to validate the accuracy and informative content richness about ZEB point clouds in stand-alone solutions and in cases of combined applications of this technology with multisensor survey approaches. In detail, the proposed validation method follows the fulfilment of the endorsed approach by use of root mean square error (RMSE) evaluation and deviation analysis assessment of point clouds between SLAM-based data and 3D point cloud surfaces computed by more precise measurement methods to evaluate the accuracy of the proposed approach. Furthermore, this study specifies the suitable scale for possible handlings about these peculiar point clouds and uses the profile extraction method in addition to feature analyses such as corner and plane deviation analysis of architectural elements. Finally, because of the experiences reported in the literature and performed in this work, a possible reversal is suggested. If in the 2000s, most studies focused on intelligently reducing the light detection and ranging (LiDAR) point clouds where they presented redundant and not useful information, contrariwise, in this sense, the use of MMS methods is proposed to be firstly considered and then to increase the information only wherever needed with more accurate high-scale methods

Mapping speditivo da sensori mobili per il controllo della conservazione dei valori paesaggistici del territorio. Quick mapping by mobile sensors for landscape values monitoring and conservation

Geomatics researches, applied to architecture and landscape, are becoming increasingly focused on development of innovation in survey techniques and digital data management. Quick techniques are sought, with a high level of automation and versatility, to support knowledge management and protection of cultural heritage, be it referred to artistic and architectural heritage or, overall, to whole varied landscape assets, in so such highest density in the country as to consider Heritage itself. The investigation and conservation initiatives in the field of landscape heritage must constantly deal with many conditions of risk exposure, and that is not always possible to make up with preventive protection, whether if it is a constant risk like that intrinsic to the status of the property, or sudden and unforeseen risks, or if it is only partially predictable, determined by an environmental emergency. In these test-sites, which have a typical vulnerability resulting from their intrinsic conditions of exposure to risk, is interesting to experiment and combine technological research with the public interest for the protection and preservation of the value of the asset. This paper is intended for the testing of systems for the expeditious acquisition of spatial data in a outstanding test site, an area of the Cinque Terre, devastated by the flood of autumn 2011 Le ricerche della Geomatica applicata all’Architettura e al paesaggio, sono mirati sempre più allo sviluppo dell’innovazione nel campo delle tecniche di acquisizione dei dati e della loro gestione digitale; si ricercano metodi speditivi, con elevati gradi di automazione e versatili, per il supporto alla gestione della conoscenza e della tutela del patrimonio culturale, che sia esso riferito ai beni artistico-architettonici o in senso più ampio all’insieme variegato dei beni paesaggistici, ad elevatissima densità nel territorio nazionale tanto da considerarlo Patrimonio esso stesso. Le indagini e le iniziative di conservazione in materia di patrimonio paesaggistico devono costantemente fronteggiare le innumerevoli condizioni di rischio cui esso è esposto, e cui non sempre si riesce a sopperire con una tutela preventiva. sia esso un rischio costante come quello intrinseco allo status del bene, oppure rischi improvvisi e imprevedibili, o solo parzialmente prevedibili, determinati da una emergenza ambientale. E’ in questi test-site, che possiedono una tipica vulnerabilità derivante dalle loro intrinseche condizioni di esposizione al rischio, che risulta interessante sperimentare e combinare la ricerca tecnologica con l’interesse collettivo di tutela e conservazione del valore del bene stesso. Il presente contributo ha per obiettivo la sperimentazione di sistemi speditivi di acquisizione dei dati spaziali in un test site d’eccezione, un’area delle Cinque Terre devastata dall’alluvione dell’autunno 2011

High scale 3D modelling and orthophoto of curved masonries for a multipurpose representation, analysis and assessment

It is important nowadays to underline some relevant topics concerning the effective contribution of 3D high detailed products derived from innovation and integration of Geomatics technologies, allowing a remarkable development in descriptive metric capabilities, supporting and improving the material recording, representation, analysis and characterization about alteration of the constructive systems. Considering the relevance of the complex interdisciplinary research of these issues that move around the Cultural Heritage safeguard and due to its extreme vulnerability, these models must give a response to different problems. Primarily they has to provide complete models on which to pursue accurate morpho-dimensional documentation, and to base structural assessment, decay investigations, and consequently to underpin restoration practices and support operational workflow in CH assets monitoring. Some peculiarities of new methods for semi-automatic processing algorithms are thus evidenced, advantaging their proficiency to behave as tools for a more sustainable approach in the general process of preservation and protection. Specifically about the ancient masonries documentation, the chance of using digital products derived from very high scale models, as the detailed orthoimages projection and surfaces development offers many opportunities. Here, a late-medieval stratified dovecote tower in Verolengo (TO) with a particular trunk-conical shape had been analysed in order to reconstruct an identity and a historical and architectural framework, de facto not recognized yet. A 3D reconstruction by dense matching techniques will be presented, in the complex context that are the vertical high buildings, presenting one of the highest level of vulnerability. The importance of the 3D model availability, closely connected to dense radiometric information, has been particularly expressed in two main direction for the diagnosis both of volumetric structure assessment and the material characterization of the mixed masonries walls

Rilievi integrati UAV e terrestri, basati su tecnologia SLAM, a Pescara del Tronto

L’integrazione di dati fotogrammetrici e laser scanning, nel contesto dei si-stemi rapidi, e l’ottimizzazione di modelli 3D da essi derivati è stata oggetto della tesi di dottorato dell’autrice1. Il presente contributo è una sintesi estre-mamente schematica di un caso applicativo scelto e affrontato nella tesi perché emblematico dell’integrazione e la validazione di modelli derivati dalla foto-grammetria UAV e dai sistemi mobili di scansione, in particolare gli scanner portatili basati sulla tecnologia SLAM. Il punto di vista aereo infatti è quello proposto e ampiamente validato in caso di criticità che interessano il contesto al suolo, o nel caso l’accesso agli spazi per via terrestre non sia consentito, nel qual caso l’approccio range-based (scansioni laser) viene proposto e validato congiuntamente

OBLIQUE IMAGES AND DIRECT PHOTOGRAMMETRY WITH A FIXED WING PLATFORM: FIRST TEST AND RESULTS IN HIERAPOLIS OF PHRYGIA (TK)

Abstract. The complex archaeological site documentation benefits for a long time now from the aerial point of view and remote sensing methods. Moreover, the recent research on UAV photogrammetry platform equipment and flight planning actively contribute in this sense for a scaling improvement and cost-benefits balance. Frequently, the experiences on articulated topographic profiles in archaeological excavations require not only a multi-sensor approach but also and above all a multiscale one. According to this line, in a general time-cost ration framework, the geometric content of the generated DSMs should be complete of nadir and oblique point of view for the accurate 3D reconstruction of both upstanding buildings and excavations. In the same way, also the radiometric content closely depends on sensor payload quality and is strictly affected by excavation site condition, related to the site material and light. In this research, carried out in the impressive archaeological site of the ancient city of Hierapolis in Phrygia (Turkey) in the autumn 2019 campaign, the main goal was to evaluate and validate the overall performance of a novel UAV fix-wing ultralight platform with onboard GNSS receiver for RTK/PPK processing of cameras positioning and with the possibility of oblique images capturing. The expected contribute in terms of the acquisition, processing time, radiometric enhancement and geometry 3D reconstruction will be explored with preliminary test and outcomes, and with the results of the high-scale DSM and orthoimage generation of the complete Hierapolis site

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

GIS-based detection of terraced landscape heritage: comparative tests using regional DEMs and UAV data

The analysis of terraced heritage has implications in many different fields of study, as it is shaped itself by natural, socioeconomic, and cultural dynamics. Given that their abandonment impoverishes territories and communities and raises natural, especially hydrogeological hazards, and that their deactivation leads to a loss of cultural identity, this paper aims to study rapid mapping systems for their detection. Since a deep relation between high land division and the use of terraces for the exploitation of territories has been recognized, a first detection method is based on cadastral maps. The joint use of regional-scale digital elevation models (DEMs) and cadastral dataset polygons, based on a model that typically uses GIS analyses, identifies areas with a high probability of terracing. A second method is based on the use of new technologies for very high-scale data collection. The DEM models derived from UAV (unmanned aerial vehicle) photogrammetry, given their ability to determine the micro-topographical characterization of the terrain as well as the most expensive on-site techniques, can be considered an excellent low-cost means by which to locate terraced heritage. The proposed work includes comparative testing between methods implying GIS-based analysis of slope models. It aims to highlight the effectiveness of using both methods: regional-scale DEMs and cadastral maps to detect a high probability of terrace localization, and DEMs derived from the use of low-altitude aerial data and structure from motion (SfM) algorithms, which have greatly and effectively increased the use of aerial drone photogrammetry

MULTI-TEMPORAL IMAGES AND 3D DENSE MODELS FOR ARCHAEOLOGICAL SITE MONITORING IN HIERAPOLIS OF PHRYGIA (TR)

The archaeological areas are one of the fields in which the contribution of image-base and range-based Geomatics techniques were employed since long time and are now getting popular (Hadjimitsis et al. 2009; Campana 2017). In recent times, Remotely Piloted Aircraft Systems (RPAS), together with Terrestrial Laser Scanning (TLS) survey systems become more and more interesting to be studied in excavations sites for monitoring purposes and solving high detail data and large scale and comprehensive mapping matters both from terrestrial and aerial point of view. 3D information derived from different acquisition campaign and different sensors too, belonging to the same spatial system, can be integrated and create a multi-temporal and multi-scale database (Remondino, Rizzi 2010; Kersten, Lindstaedt 2012; Moussa, Abdel-Wahab, Fritsch 2012; Chiabrando et al. 2016; Farella et al. 2016). The contribution of multi-sensor acquisitions, as it is known from increasing scientific experiences, offers by now to archaeological studies the possibility to obtain a multi-temporal view of the site with restricted time windows, but it is interesting considering also the possibility of a valuable integration and contribution of older image-based documentation, already stored in archives. In a complex archaeological area as the one of Hierapolis of Phrygia in Pamukkale (TR), a very interesting site investigated since several tens of years by the MAIER – Italian Archaeological Mission of Hierapolis, the impressive excavations have required extensive and accurate large-scale survey and documentation projects. This paper will also show the evolution over time of 3D survey methods. In particular, the presented experiences regarding the documentation campaigns by Politecnico di Torino and Geomatics group concern many multi-temporal datasets that have been acquired by different subsequent campaigns in 1997, 1998, 2007, 2012, 2015, by employing various sensors following the evolution of the acquisition techniques offers by geomatics in the archaeological field surveys

Integrated HBIM-GIS Models for Multi-Scale Seismic Vulnerability Assessment of Historical Buildings

The complexity of historical urban centres progressively needs a strategic improvement in methods and the scale of knowledge concerning the vulnerability aspect of seismic risk. A geographical multi-scale point of view is increasingly preferred in the scientific literature and in Italian regulation policies, that considers systemic behaviors of damage and vulnerability assessment from an urban perspective according to the scale of the data, rather than single building damage analysis. In this sense, a geospatial data sciences approach can contribute towards generating, integrating, and making virtuous relations between urban databases and emergency-related data, in order to constitute a multi-scale 3D database supporting strategies for conservation and risk assessment scenarios. The proposed approach developed a vulnerability-oriented GIS/HBIM integration in an urban 3D geodatabase, based on multi-scale data derived from urban cartography and emergency mapping 3D data. Integrated geometric and semantic information related to historical masonry buildings (specifically the churches) and structural data about architectural elements and damage were integrated in the approach. This contribution aimed to answer the research question supporting levels of knowledge required by directives and vulnerability assessment studies, both about the generative workflow phase, the role of HBIM models in GIS environments and toward user-oriented webGIS solutions for sharing and public use fruition, exploiting the database for expert operators involved in heritage preservation