Rilievo fotogrammetrico da drone per la generazione di modelli termici di porzioni di territorio

In questo elaborato viene sperimentato un iter processuale che consenta di utilizzare i sensori termici affiancati a fotocamere digitale in ambito fotogrammetrico al fine di ottenere prodotto dal quale sono estrapolabili informazioni geometriche e termiche dell’oggetto di studio. Il rilievo fotogrammetrico è stato svolto mediante l’utilizzo di un drone con equipaggiamento multisensoriale, termico e digitale, su una porzione di territorio soggetto ad anomalie termiche nei pressi di Medolla (MO). Per l’analisi termica e geometrica sono stati posizionati sul campo 5 target termici di cui ne sono state misurate le coordinate per la georeferenziazione delle nuvole dense di punti e la temperatura. In particolare sono state eseguite due riprese aeree dalle quali sono stati estratti i frame necessari per i processi di restituzione fotogrammetrica. Le immagini sono state sottoposte ad una fase di trattamento che ha prodotto immagini rettificate prive di delle distorsioni impresse dall’obbiettivo. Per la creazione degli elaborati vettoriali e raster a colori e termici sono stati impiegati inizialmente software di fotogrammetria digitale in grado di fornire scene tridimensionali georeferenziate dell’oggetto. Sono state sviluppate sia in un ambiente open-source, sia sfruttando programmi commerciali. Le nuvole dense sono state successivamente trattate su una piattaforma gratuita ad interfaccia grafica. In questo modo è stato possibile effettuare dei confronti tra i diversi prodotti e valutare le potenzialità dei software stessi. Viene mostrato come creare un modello tridimensionale, contenente sia informazioni geometriche che informazioni termiche, partendo dalla nuvola termica e da quella a colori. Entrambe georeferenziate utilizzando gli stessi punti fotogrammetrici d’appoggio. Infine i prodotti ottenuti sono stati analizzati in un ambiente GIS realizzando sovrapposizioni grafiche, confronti numerici, interpolazioni, sezioni e profili.

Photographs of the Mount Meager, southwestern British Columbia

On August 6, 2010, a large (~50 Mm**3) debris avalanche occurred on the flank of Mount Meager in the southern Coast Mountains of British Columbia, Canada. We studied the deposits to infer the morphodynamics of the landslide from initiation to emplacement. Structure from motion (SfM) photogrammetry, based on oblique photos taken with a standard SLR camera during a low helicopter traverse, was used to create high-resolution orthophotos and base maps. Interpretation of the images and maps allowed us to recognize two main rheological phases in the debris avalanche. Just below the source area, in the valley of Capricorn Creek, the landslide separated into two phases, one water-rich and more mobile, and the other water-poor and less mobile. The water-rich phase spread quickly, achieved high superelevation on the valley sides, and left distal scattered deposits. The main water-poor phase moved more slowly, did not superelevate, and formed a thick continuous deposit (up to ~30 m) on the valley floor. The water-poor flow deposit has structural features such as hummocks, brittle-ductile faults, and shear zones. Our study, based on a freshly emplaced deposit, advances understanding of large mass movements by showing that a single landslide can develop multiple rheology phases with different behaviours. Rheological evolution and separation of phases should always be taken into account to provide better risk assessment scenarios.

La generazione di modelli tridimensionali densi in ambito architettonico mediante la fotogrammetria digitale

The Italian territory offers a wide range of treasures in the field of Cultural Assets. This is a highly relevant property, which needs an accurate management and preservation performed by appropriate tools, also giving attention to the maintenance and safeguard from risk factors. Nowadays the increasing development of new digital technologies, added by remarkable steps forward got by the subject of Geomatic makes possible an efficient integration among different techniques, helped also by spread of solutions to improve the data import-export and transmission between different devices. The main objective of this thesis is to experience the photogrammetric restitution implemented in a commercial software of digital photogrammetry, in order to generate a dense 3D model of the facade of the Basilica Sant'Apollinare Nuovo in Ravenna. The 1st Chapter, after a general introduction regarding the 3D survey of Cultural Heritage and some considerations linked to the use of digital photogrammetry in this field, is focused to analyze the case of stereoscopic and the monoscopic approach. In particular, it develops the theme of close-range photogrammetry. The 2nd Chapter, exposes the theme of digital images, from color theory until their appearing on the monitor. The 3rd Chapter, develops the case study of the Basilica di Sant'Apollinare Nuovo, the historical, architectural and religious of the same. Also, it is examined the issue of photogrammetry and laser scanning of the case study. The final part of the same chapter, treats the processing of data processing the software Agisoft PhotoScan, in order to generate, by means of Structure from Motion technique, a digital geometric 3D model of the Basilica Facade. The digital model has been scaled on the basis of measurements made on the field. With the software it was possible to accomplish the three phases of the photogrammetric data processing: internal orientation, exterior orientation and restitution.

Il Vestibolo di Piazza d'Oro - Rilievi per la modellazione 3D ed il texturing

Il caso studio del vestibolo ottagonale di Villa Adriana ha dato la possibilità di applicare ad un edificio di notevole valore storico e artistico tecniche di restituzione digitale e di modellazione tridimensionale basate su applicativi di modellazione geometrica, con lo scopo di generarne il modello 3D digitale fotorealistico e polifunzionale. Nel caso specifico del vestibolo, un modello tridimensionale di questo tipo risulta utile a fini documentativi, a sostegno di ipotesi costruttive e come strumento per la valutazione di interventi di restauro. Il percorso intrapreso ha permesso di valutare le criticità nelle tecniche di acquisizione, modellazione e foto-modellazione tridimensionale applicate in ambito archeologico, tecniche usate abitualmente anche in settori quali l’architettura, il design industriale ma anche nel cinema (effetti speciali e film d’animazione) e in ambito videoludico, con obiettivi differenti: nel settore del design e della progettazione industriale il Reverse Modeling viene impiegato per eseguire controlli di qualità e rispetto delle tolleranze sul prodotto finale, mentre in ambito cinematografico e videoludico (in combinazione con altri software) permette la creazione di modelli realistici da inserire all’interno di film o videogiochi, (modelli non solo di oggetti ma anche di persone). La generazione di un modello tridimensionale ottenuto tramite Reverse Modeling è frutto di un processo opposto alla progettazione e può avvenire secondo diverse strategie, ognuna delle quali presenta vantaggi e svantaggi specifici che la rendono più indicata in alcuni casi piuttosto che in altri. In questo studio sono state analizzate acquisizioni tridimensionali effettuate tramite Laser Scan e tramite applicazioni Structure from Motion/Dense Stereo View.

The Accuracy and Reliability of Traditional Surface Flow Type Mapping: Is It Time for A New Method of Characterising Physical River Habitat?

Surface flow types (SFT) are advocated as ecologically relevant hydraulic units, often mapped visually from the bankside to characterise rapidly the physical habitat of rivers. SFT mapping is simple, non-invasive and cost-efficient. However, it is also qualitative, subjective and plagued by difficulties in recording accurately the spatial extent of SFT units. Quantitative validation of the underlying physical habitat parameters is often lacking, and does not consistently differentiate between SFTs. Here, we investigate explicitly the accuracy, reliability and statistical separability of traditionally mapped SFTs as indicators of physical habitat, using independent, hydraulic and topographic data collected during three surveys of a c. 50m reach of the River Arrow, Warwickshire, England. We also explore the potential of a novel remote sensing approach, comprising a small unmanned aerial system (sUAS) and Structure-from-Motion photogrammetry (SfM), as an alternative method of physical habitat characterisation. Our key findings indicate that SFT mapping accuracy is highly variable, with overall mapping accuracy not exceeding 74%. Results from analysis of similarity (ANOSIM) tests found that strong differences did not exist between all SFT pairs. This leads us to question the suitability of SFTs for characterising physical habitat for river science and management applications. In contrast, the sUAS-SfM approach provided high resolution, spatially continuous, spatially explicit, quantitative measurements of water depth and point cloud roughness at the microscale (spatial scales ≤1m). Such data are acquired rapidly, inexpensively, and provide new opportunities for examining the heterogeneity of physical habitat over a range of spatial and temporal scales. Whilst continued refinement of the sUAS-SfM approach is required, we propose that this method offers an opportunity to move away from broad, mesoscale classifications of physical habitat (spatial scales 10-100m), and towards continuous, quantitative measurements of the continuum of hydraulic and geomorphic conditions which actually exists at the microscale.

Exploring the World's Visual History

Thesis (Ph.D.)--University of Washington, 2016-08

Improving the Accuracy of 3-D Reconstruction in Robotic Vision Applications

Thesis (Ph.D.)--University of Washington, 2016-08

POSE ESTIMATION AND 3D RECONSTRUCTION USING SENSOR FUSION

A camera maps 3-dimensional (3D) world space to a 2-dimensional (2D) image space. In the process it loses the depth information, i.e., the distance from the camera focal point to the imaged objects. It is impossible to recover this information from a single image. However, by using two or more images from different viewing angles this information can be recovered, which in turn can be used to obtain the pose (position and orientation) of the camera. Using this pose, a 3D reconstruction of imaged objects in the world can be computed. Numerous algorithms have been proposed and implemented to solve the above problem; these algorithms are commonly called Structure from Motion (SfM). State-of-the-art SfM techniques have been shown to give promising results. However, unlike a Global Positioning System (GPS) or an Inertial Measurement Unit (IMU) which directly give the position and orientation respectively, the camera system estimates it after implementing SfM as mentioned above. This makes the pose obtained from a camera highly sensitive to the images captured and other effects, such as low lighting conditions, poor focus or improper viewing angles. In some applications, for example, an Unmanned Aerial Vehicle (UAV) inspecting a bridge or a robot mapping an environment using Simultaneous Localization and Mapping (SLAM), it is often difficult to capture images with ideal conditions. This report examines the use of SfM methods in such applications and the role of combining multiple sensors, viz., sensor fusion, to achieve more accurate and usable position and reconstruction information. This project investigates the role of sensor fusion in accurately estimating the pose of a camera for the application of 3D reconstruction of a scene. The first set of experiments is conducted in a motion capture room. These results are assumed as ground truth in order to evaluate the strengths and weaknesses of each sensor and to map their coordinate systems. Then a number of scenarios are targeted where SfM fails. The pose estimates obtained from SfM are replaced by those obtained from other sensors and the 3D reconstruction is completed. Quantitative and qualitative comparisons are made between the 3D reconstruction obtained by using only a camera versus that obtained by using the camera along with a LIDAR and/or an IMU. Additionally, the project also works towards the performance issue faced while handling large data sets of high-resolution images by implementing the system on the Superior high performance computing cluster at Michigan Technological University.

Tecniche geomatiche di reverse engineering nel campo dei Beni Culturali

La salvaguardia e conservazione del Patrimonio Artistico ed Architettonico rappresentano un aspetto imprescindibile di ogni cultura, e trovano le loro fondamenta nella coscienza e conoscenza dei Beni. Il rilievo è l’operazione basilare per acquisire una conoscenza rigorosa di un oggetto nella sua geometria e in altre sue caratteristiche. Le finalità delle operazioni di rilevamento sono molteplici, dall’archiviazione a scopo di documentazione fino all’indagine conservativa volta alla diagnostica e alla progettazione di interventi. I modelli digitali, introdotti dallo sviluppo tecnologico degli ultimi decenni, permettono una perfetta conoscenza del bene, non necessitano di contatto diretto durante la fase di rilevamento e possono essere elaborati secondo le esigenze del caso. Le tecniche adottate nel Reverse Engineering si differenziano per il tipo di sensore utilizzato: quelle fotogrammetriche utilizzano sensori di tipo “passivo” e trovano oggi largo impiego nel settore dei Beni Culturali grazie agli strumenti di Structure from Motion, mentre strumenti basati su sensori di tipo “attivo” utilizzano Laser o proiezione di luce strutturata e sono in grado di rilevare con grande precisione geometrie anche molto complesse. La costruzione del modello della fontana del Nettuno e della torre Garisenda di Bologna costituiscono un valido esempio di applicazione delle tecniche di rilievo digitale, e dimostrano la validità delle stesse su oggetti di diversa dimensione in due diversi ambiti applicativi: il restauro e il monitoraggio. Gli sviluppi futuri del Reverse Engineering in questo ambito sono molteplici, e la Geomatica rappresenta senza dubbio una disciplina fondamentale per poterli realizzare.

Assessing the relationship between bee/flower diversity and vegetation structural heterogeneity through UAV photogrammetry

The ecosystem services provided by bees are very important. Factors as habitat fragmentation, intensive agriculture and climate change are contributing to the decline of bee populations. The use of remote sensing could be a useful tool for the recognition of sites with a high diversity, before performing a more expensive survey in the field. In this study the ability of Unmanned Aerial Vehicles (UAV) images to estimate biodiversity at local scale has been analysed testing the concept of the Height Variation Hypothesis (HVH). This approach states that, the higher the vegetation height heterogeneity (HH) measured by remote sensing information, the higher the vertical complexity and the higher vegetation species diversity. In this thesis the concept has been brought to a higher level, in order to understand if the vegetation HH can be considered a proxy also of bee species diversity and abundance. We tested this approach collecting field data on bees/flowers and RGB images through an UAV campaign in 30 grasslands in the South of the Netherlands. The Canopy Height Model (CHM) were derived through the photogrammetry technique "Structure from Motion" (SfM) with resolutions of 10cm, 25cm, 50cm. Successively, the HH assessed on the CHM using the Rao's Q heterogeneity index was correlated to the field data (bee abundance, diversity and bee/flower species richness). The correlations were all positive and significant. The highest R2 values were found when the HH was calculated at 10cm and correlated to bee species richness (R2 = 0.41) and Shannon’s H index (R2 = 0.38). Using a lower spatial resolution the goodness of fit slightly decreases. For flower species richness the R2 ranged between 0.36 to 0.39. Our results suggest that methods based on the concept behind the HVH, in this case deriving information of HH from UAV data, can be developed into valuable tools for large-scale, standardized and cost-effective monitoring of flower diversity and of the habitat quality for bees.

Il ruolo delle tecniche geomatiche nella realizzazione di Digital Twin City: una sperimentazione sulla città di Bologna

L’incessante urbanizzazione e il continuo aumento della popolazione urbana stanno generando nuove sfide per le pubbliche amministrazioni, le quali necessitano soluzioni per la gestione sostenibile di risorse primarie (cibo, acqua, suolo, fonti energetiche) e la corretta pianificazione delle città, allo scopo di salvaguardare le condizioni ambientali, la salute dei cittadini e il progresso economico: in questo complesso panorama si afferma il concetto di Digital Twin City (DTC) o gemello digitale della città, la controparte virtuale di oggetti e processi in ambiente urbano in grado di comunicare con essi e di simularne, replicarne e predirne i possibili scenari. In questo contesto, un elemento essenziale è costituito dal modello geometrico 3D ad alta fedeltà dell'ambiente urbano, e la Geomatica fornisce gli strumenti più idonei alla sua realizzazione. La presente elaborazione si sviluppa in tre parti: nella prima è stata condotta un’analisi della letteratura sui DTC, in cui sono state evidenziate le sue caratteristiche principali come l’architettura, le tecnologie abilitanti, alcune possibili modellazioni, ostacoli, scenari futuri ed esempi di applicazioni reali, giungendo alla conclusione che un accurato modello 3D della città deve essere alla base dei DTC; nella seconda parte è stata illustrata nel dettaglio la teoria delle principali tecniche geomatiche per la realizzazione di modelli 3D ad alta fedeltà, tra cui le tecniche fotogrammetriche di aerotriangolazione e l’algoritmo Structure from Motion (SfM); nella terza e ultima parte è stata condotta una sperimentazione su tre zone campione del comune di Bologna di cui, grazie ad un dataset di fotogrammi nadirali e obliqui ottenuto da un volo fotogrammetrico realizzato nel 2022, sono state ottenute Reality Meshes e ortofoto/DSM. I prodotti della terza zona sono stati confrontati con i medesimi ottenuti da un dataset del 2017. Infine, sono state illustrati alcuni strumenti di misura e di ritocco dei prodotti 3D e 2D.

From genotype to phenotype : diversity and population structure of Flavobacterium psychrophilum

Flavobacterium psychrophilum is the etiological agent of bacterial cold-water disease (BCWD) causing high fish mortalities and significant economic losses to the freshwater salmonid aquaculture industry around the world. Today BCWD outbreaks are mainly treated with environmentally hazardous antimicrobial agents and alternative preventative measures are urgently needed in order to ensure the well-being of animals and the sustainability of aquaculture. The diversity of pathogenic bacteria challenges the development of universal control strategies and in many cases the pathogen population structure, i.e. the total genetic diversity of the species must be taken into account. This work integrates the tools of modern molecular biology and conventional phenotypic microbiology to gain knowledge about the diversity and population structure of F. psychrophilum. The present work includes genetic characterization of a large collection of isolates collected from diverse origins and years, from aquaculture in a whole region including different countries, and provides the first international validation of a universal multilocus sequence typing (MLST) approach for unambiguous genetic typing of F. psychrophilum. Population structure analyses showed that the global F. psychrophilum population is subdivided into pathogenic species-specific clones, of which one particular genetic lineage, clonal complex CC-ST2, has been responsible for the majority of BCWD outbreaks in rainbow trout (Oncorhynchus mykiss) in European aquaculture facilities over several decades. Genotypic and phenotypic population heterogeneity affecting antimicrobial resistance in F. psychrophilum within BCWD outbreaks was discovered. Specific genotypes were associated with severe infections in farmed rainbow trout and Atlantic salmon (Salmo salar), and in addition to high adherence, antimicrobial resistance was strongly associated with outbreak strains. The study brought additional support for the hypothesis of an epidemic F. psychrophilum population structure, where recombination is an important force for the generation and maintenance of genetic diversity, and a significant contribution towards mapping the genetic diversity of this important fish pathogen. Evidence indicating dissemination of virulent strains with commercial movement of fish and fish products was strengthened.

Three-Dimensional Motion Estimation Using Shading Information in Multiple Frames

A new formulation for recovering the structure and motion parameters of a moving patch using both motion and shading information is presented. It is based on a new differential constraint equation (FICE) that links the spatiotemporal gradients of irradiance to the motion and structure parameters and the temporal variations of the surface shading. The FICE separates the contribution to the irradiance spatiotemporal gradients of the gradients due to texture from those due to shading and allows the FICE to be used for textured and textureless surface. The new approach, combining motion and shading information, leads directly to two different contributions: it can compensate for the effects of shading variations in recovering the shape and motion; and it can exploit the shading/illumination effects to recover motion and shape when they cannot be recovered without it. The FICE formulation is also extended to multiple frames.

Geometric and Algebraic Aspects of 3D Affine and Projective Structures from Perspective 2D Views

We investigate the differences --- conceptually and algorithmically --- between affine and projective frameworks for the tasks of visual recognition and reconstruction from perspective views. It is shown that an affine invariant exists between any view and a fixed view chosen as a reference view. This implies that for tasks for which a reference view can be chosen, such as in alignment schemes for visual recognition, projective invariants are not really necessary. We then use the affine invariant to derive new algebraic connections between perspective views. It is shown that three perspective views of an object are connected by certain algebraic functions of image coordinates alone (no structure or camera geometry needs to be involved).

Can we constrain the interior structure of rocky exoplanets from mass and radius measurements?

Aims. We present an inversion method based on Bayesian analysis to constrain the interior structure of terrestrial exoplanets, in the form of chemical composition of the mantle and core size. Specifically, we identify what parts of the interior structure of terrestrial exoplanets can be determined from observations of mass, radius, and stellar elemental abundances. Methods. We perform a full probabilistic inverse analysis to formally account for observational and model uncertainties and obtain confidence regions of interior structure models. This enables us to characterize how model variability depends on data and associated uncertainties. Results. We test our method on terrestrial solar system planets and find that our model predictions are consistent with independent estimates. Furthermore, we apply our method to synthetic exoplanets up to 10 Earth masses and up to 1.7 Earth radii, and to exoplanet Kepler-36b. Importantly, the inversion strategy proposed here provides a framework for understanding the level of precision required to characterize the interior of exoplanets. Conclusions. Our main conclusions are (1) observations of mass and radius are sufficient to constrain core size; (2) stellar elemental abundances (Fe, Si, Mg) are principal constraints to reduce degeneracy in interior structure models and to constrain mantle composition; (3) the inherent degeneracy in determining interior structure from mass and radius observations does not only depend on measurement accuracies, but also on the actual size and density of the exoplanet. We argue that precise observations of stellar elemental abundances are central in order to place constraints on planetary bulk composition and to reduce model degeneracy. We provide a general methodology of analyzing interior structures of exoplanets that may help to understand how interior models are distributed among star systems. The methodology we propose is sufficiently general to allow its future extension to more complex internal structures including hydrogen- and water-rich exoplanets.