USE OF ASSISTED PHOTOGRAMMETRY FOR INDOOR AND OUTDOOR NAVIGATION PURPOSES

Nowadays, devices and applications that require navigation solutions are continuously growing. For instance, consider the increasing demand of mapping information or the development of applications based on users’ location. In some case it could be sufficient an approximate solution (e.g. at room level), but in the large amount of cases a better solution is required. The navigation problem has been solved from a long time using Global Navigation Satellite System (GNSS). However, it can be unless in obstructed areas, such as in urban areas or inside buildings. An interesting low cost solution is photogrammetry, assisted using additional information to scale the photogrammetric problem and recovering a solution also in critical situation for image-based methods (e.g. poor textured surfaces). In this paper, the use of assisted photogrammetry has been tested for both outdoor and indoor scenarios. Outdoor navigation problem has been faced developing a positioning system with Ground Control Points extracted from urban maps as constrain and tie points automatically extracted from the images acquired during the survey. The proposed approach has been tested under different scenarios, recovering the followed trajectory with an accuracy of 0.20 m. For indoor navigation a solution has been thought to integrate the data delivered by Microsoft Kinect, by identifying interesting features on the RGB images and re-projecting them on the point clouds generated from the delivered depth maps. Then, these points have been used to estimate the rotation matrix between subsequent point clouds and, consequently, to recover the trajectory with few centimeters of error

Riconoscimento di specie arboree mediante classificazione di immagini multispettrali e multitemporali ad altissima risoluzione

Da tempo impiegati nell'agricoltura di precisione, i rilievi di prossimità con UAS cominciano a esser eseguiti anche per applicazioni forestali e ambientali. Il rilievo da UAV con sensori ottici, infatti, consente di acquisire immagini ad altissima risoluzione (GSD dell'ordine di cm), che possono essere opportunamente usate per la classificazione e la distinzione di specie vegetali. Nell'ambito di un progetto di ricerca di Dottorato in Geomatica, è stato effettuato un esperimento di classificazione mediante algoritmi ampiamente utilizzati in telerilevamento, a partire da immagini aeree di prossimità acquisite su un vivaio di piante. Tale area è stata scelta come "poligono test" per la presenza di molte varietà di alberi, raggruppati per specie. Un rilievo multispettrale è stato effettuato durante il periodo di maggior copertura fogliare con esacottero Mikrokopter del Politecnico di Milano (Dip.di Ing. Civile e Ambientale) e camere Nikon 1 J1 e Tetracam ADCLite. I due blocchi di immagini, a colori e a falso colore, sono stati orientati simultaneamente; dal blocco RGB è stato poi ottenuto il modello di superficie e, su questo, sono state generate le due ortofoto (RGB e NIR-RG). Dai canali NIR e Red di quest'ultima, è stato infine calcolato l'indice di vegetazione NDVI. Il rilievo è stato ripetuto anche in autunno per rilevare nuove informazioni spettrali, molto variabili da una specie all'altra. L'ortofoto RGB autunnale è stata creata usando il medesimo DSM estivo. Sulla base della verità al suolo raccolta in campo, è stata effettuata una classificazione supervisionata con algoritmo Max Likelihood su un layer stack di sette bande. Sebbene la copertura fogliare autunnale fosse ridotta, tale classificazione è caratterizzata da un incremento dell'accuratezza totale del 13% rispetto a quella della classificazione effettuata sulle sole bande estive (RGB e NDVI). Il medesimo algoritmo è stato infine impiegato su differenti combinazioni di canali originali e derivati, tra cui un indice di variazione temporale e la trasformazione allo spazio IHS

Low-Cost Uas Photogrammetry for Road Infrastructures' Inspection

Abstract. All over the world, road infrastructures are getting closer to their life cycle and need to be constantly inspected: a consistent number of bridges are structurally deficient, and the risk of collapse can no longer be excluded. In contrast with the past, the interest in structure durability has recently grown rapidly. In order to make bridges durable, it is necessary to carry out ordinary maintenance, preceded by inspection activities, which can be traditionally divided in two categories: destructive and non-destructive (NDT). All the NDT inspections (visual, IR thermography, GPR) can be conducted by using UAS (Unmanned Aerial Systems), a technology that makes bridges inspections quicker, cheaper, objective and repeatable. This study presents the visual inspection and survey of two bridges by using a UAS DJI Mavic 2 Pro, equipped with a 20Mpixel Hasselblad camera that records 60fps 4K video and a 10bit radiometric resolution. Starting from the acquired data, a 3D model of each structure was built by using Structure from Motion (SfM) principles and software. To validate the two models, each of them characterized by a centimetric accuracy, the UAS camera generated cloud of points and was co-registered with the point cloud of a terrestrial laser-scanner using Ground Control Points (GCPs). To make this, CloudCompare comparison software was used; the plugin M3C2 automatically calculates the distance between the points of two compared clouds. Finally, some general rules concerning the UAS main characteristics for inspection of bridges and software for data processing are proposed

GNSS methods in dam monitoring: case studies and future perspectives

GNSS receivers are nowadays commonly used in monitoring applications, e.g. in estimating crustal and infrastructure deformations. This is basically due to the recent improvements in GNSS instruments and methodologies that allow high precision positioning, 24h availability, semiautomatic data processing. In this paper, we use GNSS technique to monitor dam deformation behaviour comparing results with outcomes from pendulum observations that thanks to their reliability and high accuracy can be considered as reference. The study has been carried out for two dams in Sardinia: the Genna Is Abis on Rio Cixerri, and the Eleonora D’Arborea called also Cantoniera dam. Appropriate analytical models of dam deformation depending on time, reservoir water level, air and water temperature have been estimated using pendulum data (for Genna Is Abis dam) and GNSS data (for Cantoniera dam). Both reference models were able to properly fit respectively pendulum data and GNSS data, with standard deviation of residuals lower than one millimeter. Furthermore the Genna Is Abis reference deformation model deduced by pendulum was compared with estimated displacement from GNSS observations and standard deviation of the residuals was still lower than one millimeter. For the send model estimated at Cantoniera dam the comparison with pendulum data gave residual with mean around zero and standard deviation of lower than two millimiter. These encouraging outcomes open new perspectives in the study of deformations of structures that foresee the GNSS technique as complementary monitoring instrumentation especially for medium-long time intervals

Vision-Based Georeferencing of GPR in Urban Areas

Ground Penetrating Radar (GPR) surveying is widely used to gather accurate knowledge about the geometry and position of underground utilities. The sensor arrays need to be coupled to an accurate positioning system, like a geodetic-grade Global Navigation Satellite System (GNSS) device. However, in urban areas this approach is not always feasible because GNSS accuracy can be substantially degraded due to the presence of buildings, trees, tunnels, etc. In this work, a photogrammetric (vision-based) method for GPR georeferencing is presented. The method can be summarized in three main steps: tie point extraction from the images acquired during the survey, computation of approximate camera extrinsic parameters and finally a refinement of the parameter estimation using a rigorous implementation of the collinearity equations. A test under operational conditions is described, where accuracy of a few centimeters has been achieved. The results demonstrate that the solution was robust enough for recovering vehicle trajectories even in critical situations, such as poorly textured framed surfaces, short baselines, and low intersection angles

Kinect Fusion improvement using depth camera calibration

Scene's 3D modelling, gesture recognition and motion tracking are fields in rapid and continuous development which have caused growing demand on interactivity in video-game and e-entertainment market. Starting from the idea of creating a sensor that allows users to play without having to hold any remote controller, the Microsoft Kinect device was created. The Kinect has always attract researchers in different fields, from robotics to Computer Vision (CV) and biomedical engineering as well as third-party communities that have released several Software Development Kit (SDK) versions for Kinect in order to use it not only as a game device but as measurement system. Microsoft Kinect Fusion control libraries (firstly released in March 2013) allow using the device as a 3D scanning and produce meshed polygonal of a static scene just moving the Kinect around. A drawback of this sensor is the geometric quality of the delivered data and the low repeatability. For this reason the authors carried out some investigation in order to evaluate the accuracy and repeatability of the depth measured delivered by the Kinect. The paper will present a throughout calibration analysis of the Kinect imaging sensor, with the aim of establishing the accuracy and precision of the delivered information: a straightforward calibration of the depth sensor in presented and then the 3D data are correct accordingly. Integrating the depth correction algorithm and correcting the IR camera interior and exterior orientation parameters, the Fusion Libraries are corrected and a new reconstruction software is created to produce more accurate models

AERIAL IMAGES FROM AN UAV SYSTEM: 3D MODELING AND TREE SPECIES CLASSIFICATION IN A PARK AREA

The use of aerial imagery acquired by Unmanned Aerial Vehicles (UAVs) is scheduled within the FoGLIE project (Fruition of Goods Landscape in Interactive Environment): it starts from the need to enhance the natural, artistic and cultural heritage, to produce a better usability of it by employing audiovisual movable systems of 3D reconstruction and to improve monitoring procedures, by using new media for integrating the fruition phase with the preservation ones. The pilot project focus on a test area, Parco Adda Nord, which encloses various goods' types (small buildings, agricultural fields and different tree species and bushes). Multispectral high resolution images were taken by two digital compact cameras: a Pentax Optio A40 for RGB photos and a Sigma DP1 modified to acquire the NIR band. Then, some tests were performed in order to analyze the UAV images' quality with both photogrammetric and photo-interpretation purposes, to validate the vector-sensor system, the image block geometry and to study the feasibility of tree species classification. Many pre-signalized Control Points were surveyed through GPS to allow accuracy analysis. Aerial Triangulations (ATs) were carried out with photogrammetric commercial software, Leica Photogrammetry Suite (LPS) and PhotoModeler, with manual or automatic selection of Tie Points, to pick out pros and cons of each package in managing non conventional aerial imagery as well as the differences in the modeling approach. Further analysis were done on the differences between the EO parameters and the corresponding data coming from the on board UAV navigation system

Antiphospholipids syndrome complicated by a systemic capillary leak-like syndrome treated with steroids and intravenous immunoglobulins a case report

This report describes the onset of systemic capillary leak (SCL)-like syndrome in a 30-year-old woman with antiphospholipids syndrome (APS) during puerperium. Twelve hours after a cesarean section, she presented a sudden fever and abdominal pains followed by dyspnea, severe edema of the limbs and pelvis. Computer tomography shows congestion of interstitial pulmonary parenchyma, pericardial and pleural effusion, edema of intestinal wall and of perivisceral adipose tissue, and periportal lymphedema. Laboratory tests showed neutrophilic leukocytosis, hypoalbuminemia, and an increase of erythrocyte sedimentation rate and C-reactive protein. Because fever and raised inflammation parameters are not observed in idiopathic capillary leak syndrome (SCLS; Clarkson disease), a diagnosis of SCL-like syndrome was made. Albumin solution, high-dose methylprednisolone and intravenous immunoglobulins (IVIG) infusion were administered with a rapid improvement of her clinical condition. The prompt treatment with steroids and IVIG likely prevented the life-threatening shock syndrome that can occur in SCLS, with acute hypotensive attacks, and severe limbs edema requiring fasciotomy. All clinical and laboratory findings supported autoinflammation as the underlying pathogenic mechanism of the syndrome. The data indicate that SCL-like syndrome can be considered a novel clinical syndrome, which can complicate APS

Utilizzo di immagini acquisite da UAV per la documentazione e una miglior fruizione di beni culturali e paesaggistici

L'uso di immagini aeree acquisite con velivoli senza pilota, i cosiddetti UAVs (Unmanned Aerial Vehicles), si sta sempre più diffondendo per scopi sia descrittivi sia geometrici. Ne è previsto, ad esempio, l'impiego all'interno del progetto FoGLIE (Fruition of Goods Landscape in Interactive Environment) recentemente finanziato dalla Regione Lombardia. Esso nasce dalla necessità di valorizzare il patrimonio culturale e paesaggistico presente sul territorio lombardo, allo scopo di proporne una maggiore fruibilità, tramite sistemi audio-visuali con i quali rappresentare i beni nel loro contesto cartografico di riferimento. Le finalità principali del progetto sono: - la creazione di un sistema di guida multimediale innovativo per la fruizione di beni culturali e paesaggistici anche di zone ad oggi inaccessibili; - il superamento di strutture ingombranti ed invasive quali totem o postazioni di interfaccia, di grande impatto sull’ambiente architettonico e naturale, sostituite da sistemi mobili; - l'integrazione di fruibilità e monitoraggio attivo del bene e del territorio, grazie a segnalazioni “garantite” che gli utenti potranno inviare dal dispositivo. FoGLIE, che ha avuto inizio nell'Ottobre del 2010 e sarà concluso a fine 2012, vede coinvolte alcune realtà imprenditoriali lombarde e il DIIAR del Politecnico di Milano, in qualità di componente scientifica e di consulenza tecnica in ambito cartografico e fotogrammetrico. Durante lo svolgimento del progetto si è presa in analisi una area test, individuata nel Parco Adda Nord, che racchiude al suo interno diverse categorie di beni paesaggistici e culturali (di valore architettonico e tecnologico) e paesaggistici. L’intento è di mettere a punto una metodologia per il rilievo, la documentazione e la divulgazione dei risultati che possa essere esportata ad altri casi simili. Nel presente lavoro si dà spazio all’organizzazione della ricerca, ai risultati ottenuti e alle raccomandazioni alle quali si è giunti al fine di utilizzare le nuove tecnologie nell’ambito della fruizione dei beni culturali e paesaggistici, con particolare attenzione alle riprese con UAV, alla realizzazione di modelli virtuali delle emergenze culturali del Parco, opportunamente georeferenziati e inseriti in ortofotocarta