1,720,959 research outputs found
The engineering and assembly of a low cost UAV
No full textThe rising interest that has developed in the last period around the UAV (Unmanned Aerial Veichle) systems, commonly known as drones, makes interesting the following discussion that, starting from theoretical considerations, comes to the design and construction of a small low-cost UAV system. In particular, in order to realized a low cost nano UAV system, has been analyzed the technological components necessary for an appropriate design
Smartphone and low-cost sensors systems for geospatial data acquisition in terrestrial and water scenarios and processing methods
Full text linkIl documento finale “The future we want” e l’Agenda 2030 per lo Sviluppo Sostenibile riconoscono l’importanza dei dati geospaziali in quanto elementi di supporto per il raggiungimento dello sviluppo sostenibile. I dati geospaziali supportano la definizione di politiche, programmi e progetti dedicati allo sviluppo sostenibile fornendo informazioni per la pianificazione, la valutazione, il monitoraggio e la previsione. Purtroppo, la raccolta di dati geospaziali su scala locale in situ è un’operazione spesso costosa a causa della strumentazione da utilizzare, del personale specializzato impiegato nelle operazioni di rilievo e della logistica coinvolta. L’aspetto economico può rappresentare un problema per i Paesi più vulnerabili che da una parte hanno necessità di dati su scala locale per sostenere i propri progetti di sviluppo sostenibile ma dall’altra hanno un problema di scarsità di dati e di “digitale divide” rispetto ai paesi più sviluppati. Inoltre, il fattore economico può rappresentare un ostacolo anche alla creazione di progetti di citizen science utili per il raggiungimento dello sviluppo sostenibile secondo i principi dell’inclusività, della trasparenza e della partecipazione.
Sulla base di queste osservazioni, per il lavoro di tesi, è stato realizzato un progetto di ricerca dedicato allo studio di smartphone, tablet e sensori low-cost esterni (interfacciabili con dispositivi mobili) per l’acquisizione di dati geospaziali a basso costo in ambienti terrestri e acquatici. Il progetto di ricerca si è composto di quattro parti i cui obbiettivi principali sono stati: valutazione del posizionamento tramite Global Navigation Satellite System (GNSS) con smartphones; valutazione dei sensori di profondità integrati sui dispositivi mobili; implementazione di un sistema sonar low-cost basato sugli smartphones per la raccolta di dati batimetrici e sviluppo di un metodo di modellazione per la successiva ricostruzione 3D dei dati raccolti; infine studio della GNSS-aided photogrammetry implementata attraverso smartphones e sensori low-cost.
In particolare, nella prima parte del progetto di ricerca, attraverso un metodo di analisi statistica potenzialmente applicabile a tutti i dispositivi Android dotati di un ricevitore GNSS integrato, è stata valutata la qualità del posizionamento GNSS in post-processing con sole misure di pseudorange degli smartphone Android.
Nella seconda parte del progetto di ricerca, sono state valutate le performance dei sensori di profondità dei dispositivi mobili Android e Apple attraverso l’analisi delle nuvole di punti da essi prodotte usando sia metodi visivi (analisi delle sezioni della nuvola di punti) che descrittori matematici (eigenfeatures: planarity, omnivariance e surface variation).
Nella terza parte del progetto di ricerca, è stato implementato un sistema sonar formato da sensori low-cost chiamato GNSS > Sonar > Phone System (G > S > P Sys) capace di raccogliere dati batimetrici in acque poco profonde ed è stato sviluppato un metodo per la modellazione 3D dei dati batimetrici raccolti basato sulla mappatura attraverso un metodo di machine learning.
Nella quarta parte del progetto di ricerca, è stata studiata la GNSS-aided photogrammetry attraverso video per la produzione di nuvole di punti e modelli 3D mesh automaticamente scalati e georeferenziati. La GNSS-aided photogrammetry è stata implementata utilizzando lo smartphone e alcuni sensori low-cost considerando due sistemi e tre approcci diversi.
Infine, osservando i risultati ottenuti si può dedurre che l’uso di smartphone e tablet per l’acquisizione di dati geospaziali di buona e alta qualità è possibile solo individuando il metodo più idoneo per il posizionamento dei dispositivi. In base alle applicazioni sperimentate nel progetto di ricerca, il problema del posizionamento dei dispositivi mobili è stato risolto tramite un ricevitore GNSS esterno low-cost per smartphone. Ciò non esclude la possibilità di altri metodi di posizionamento da esplorare in ricerche future.The outcome document “The future we want” and the 2030 Agenda for Sustainable Development recognise the importance of geospatial data as an supporting elements for achieving the sustainable development. Geospatial data support the definition of policies, programmes and projects dedicated to sustainable development by providing information for planning, assessment, monitoring and forecasting. Sadly, the collection of geospatial data on a local scale in situ is often an expensive operation due to the instruments to be used, the specialised staff employed in the survey operations and the logistics involved. The economic side can be a problem for the most vulnerable nations, that on the one hand need data on a local scale to support their sustainable development projects, but on the other hand have problems of data scarcity and a “digital divide” compared to more developed nations. Furthermore, the economic side can be an obstacle for the creation of citizen science projects useful for the achievement of sustainable development according to the principles of inclusiveness, transparency and participation.
Based on these observations, a research project dedicated to the study of smartphones, tablets and low-cost external sensors (which can be interfaced with mobile devices) for cost-effective geospatial data acquisition in terrestrial and water environments was realised for the thesis work. The research project consisted of four parts, the principal aims of which were: evaluation of smartphones Global Navigation Satellite System (GNSS) positioning; evaluation of depth sensors integrated on mobile devices; implementation of a low-cost sonar system based on smartphones for collecting bathymetric data and development of a modelling method for the subsequent 3D reconstruction of the collected data; and finally, study of GNSS-aided photogrammetry via smartphones and low-cost sensors.
In particular, in the first part of the research project, through a statistical analysis method potentially applicable to all Android devices with an integrated GNSS receiver, the quality of GNSS positioning in post-processing with only pseudorange measurements of Android smartphones was evaluated.
In the second part of the research project, the performances of the depth sensors of Android and Apple mobile devices were evaluated by analysing the point clouds produced by them using both visual methods (analysis of point cloud sections) and mathematical descriptors (eigenfeatures: planarity, omnivariance and surface variation).
In the third part of the research project, a sonar system consisting of low-cost sensors called GNSS > Sonar > Phone System (G > S > P Sys) able to collect bathymetric data in shallow water was implemented, and a method for 3D modelling of the collected data based on mapping via a machine learning approach was developed.
In the fourth part of the research project, GNSS-aided photogrammetry via video was studied for the production of automatically scaled and georeferenced point clouds and 3D mesh models. GNSS-aided photogrammetry was implemented using the smartphone and various low-cost sensors considering two systems and three different approaches.
Finally, observing the results obtained, it can be deduced that the use of smartphones and tablets for the acquisition of good and high quality geospatial data is possible only by finding the most appropriate method for the positioning the devices. Based on the applications experimented in the research project, the problem of mobile device positioning was solved using a low-cost external GNSS receiver for smartphones. However, this does not exclude the possibility of exploring other positioning methods in future research
Comparison of two approaches to gnss positioning using code pseudoranges generated by smartphone device
Full text linkSmartphone LiDAR Technologies for Surveying and Reality Modelling in Urban Scenarios: Evaluation Methods, Performance and Challenges
Full text linkThe aim of the research was to evaluate the performance of smartphone depth sensors (Time of Flight Camera(ToF) and Light Detection and Ranging (LiDAR)) from Android (Huawei P30 Pro) and iOS (iPhone 12 Pro and iPAD 2021 Pro) devices in order to build a 3D point cloud. In particular, the smartphones were tested in several case studies involving the scanning of several objects: 10 building material samples, a statue, an interior room environment and the remains of a Doric column in a major archaeological site. The quality of the point clouds was evaluated through visual analysis and using three eigenfeatures: surface variation, planarity and omnivariance. Based on this approach, some issues with the point clouds generated by smartphones were highlighted, such as surface splitting, loss of planarity and inertial navigation system drift problems. In addition, it can finally be deduced that, in the absence of scanning problems, the accuracies achievable from this type of scanning are ~1–3 cm. Therefore, this research intends to describe a method of quantifying anomalies occurring in smartphone scans and, more generally, to verify the quality of the point cloud obtained with these devices
Building 3D City model from painting: the case study of Old Town of Taranto, Italy
No full textThe aim of the work concerns the building of a three-dimensional model of the old town of Taranto (Italy) from a 1761 painting by English historian and geographer Thomas Salmon and published by Venetian printer Giambattista Albrizzi. To achieve this aim, a suitable and original methodology was developed. In addition, 3D modelling based on the use of Rhinoceros enabled the construction of a 3D city model. This model makes it possible to highlight the transformations and evolutions of the old town over time
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A Novel Method Based on Deep Learning, GIS and Geomatics Software for Building a 3D City Model from VHR Satellite Stereo Imagery
Full text linkThe aim of the paper is to identify a suitable method for the construction of a 3D city model from stereo satellite imagery. In order to reach this goal, it is necessary to build a workflow consisting of three main steps: (1) Increasing the geometric resolution of the color images through the use of pan-sharpening techniques, (2) identification of the buildings’ footprint through deep-learning techniques and, finally, (3) building an algorithm in GIS (Geographic Information System) for the extraction of the elevation of buildings. The developed method was applied to stereo imagery acquired by WorldView-2 (WV-2), a commercial Earth-observation satellite. The comparison of the different pan-sharpening techniques showed that the Gram–Schmidt method provided better-quality color images than the other techniques examined; this result was deduced from both the visual analysis of the orthophotos and the analysis of quality indices (RMSE, RASE and ERGAS). Subsequently, a deep-learning technique was applied for pan sharpening an image in order to extract the footprint of buildings. Performance indices (precision, recall, overall accuracy and the F1measure) showed an elevated accuracy in automatic recognition of the buildings. Finally, starting from the Digital Surface Model (DSM) generated by satellite imagery, an algorithm built in the GIS environment allowed the extraction of the building height from the elevation model. In this way, it was possible to build a 3D city model where the buildings are represented as prismatic solids with flat roofs, in a fast and precise way
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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