1,584 research outputs found
PORTABLE MULTI-CAMERA SYSTEM: FROM FAST TUNNEL MAPPING TO SEMI-AUTOMATIC SPACE DECOMPOSITION AND CROSS-SECTION EXTRACTION
The paper outlines the first steps of a research project focused on the digitalization of underground tunnels for the mining industry. The aim is to solve the problem of rapidly, semi-automatically, efficiently, and reliably digitizing complex and meandering tunnels. A handheld multi-camera photogrammetric tool is used for the survey phase, which allows for the rapid acquisition of the image dataset needed to produce the 3D data. Moreover, since often, automatic, and fast acquisitions are not supported by easy-to-use tools to access and use the data at an operational level, a second aim of the research is to define a method able to arrange and organise the gathered data so that it would be easily accessible. The proposed approach is to compute the 3D skeleton of the surveyed environment by employing tools developed for the analysis of vascular networks in medical imagery. From the computed skeletonization of the underground tunnels, a method is proposed to automatically extrapolate valuable information such as cross-sections, decomposed portions of the tunnel, and the referenced images from the photogrammetric survey. The long-term research goal is to create an effective workflow, both at the hardware and software level, that can reduce computation times, process large amounts of data, and reduce dependency on high levels of experience
Monitoraggio della diga “Castello” di Bivona (AG) con tecniche GNSS
Le dighe di grandi dimensioni, di terra o di cemento, sono infrastrutture che rivestono un ruolo
critico nella fornitura idrica e nella produzione energetica. Come è noto in letteratura, il carico e lo
scarico delle forze sottopone la diga a elevate sollecitazioni strutturali che devono essere
monitorate. Queste possono essere dovute alle fluttuazioni del livello dell'acqua, all'assestamento
della struttura, all'attività di frane situate nelle vicinanze o all'attività sismica. Rilevare
preventivamente i potenziali problemi consente di adottare le misure necessarie per evitare che si
verifichi una catastrofe, o mitigarne gli effetti. Il lavoro proposto è in corso di svolgimento presso il
Dipartimento di Ingegneria Civile, Ambientale Aerospaziale, dei Materiali (DICAM)
dell'Università degli Studi di Palermo e ha come scopo il monitoraggio della Diga “Castello”,
sbarramento di materiali sciolti situato tra i comuni di Bivona e Alessandria della Rocca in
provincia di Agrigento, mediante il posizionamento sul coronamento di tre ricevitori GNSS. Le
antenne sono state monumentate su appositi pilastrini in acciaio fissati al suolo mediante piccola
fondazione in cls; il rate impostato ai ricevitori è stato di 30 sec., l'angolo di cut-off di 10°. La
campagna di rilevamento è in corso e ad oggi sono stati archiviati 12 mesi di dati con cadenza
settimanale. Verificata la buona qualità dei dati a disposizione si è proceduto con l'elaborazione
degli stessi mediante i software NDA Professional e Bernese GPS 5.0
SURVEY OF HISTORICAL GARDENS: MULTI-CAMERA PHOTOGRAMMETRY VS MOBILE LASER SCANNING
This paper presents an investigation into the characterization of historical gardens by comparing two 3D survey methodologies. In this context, approaches employing terrestrial laser scanning are considered the most accurate, while Mobile Mapping Systems (MMSs) are considered promising due to their extreme productivity. Less common is the use of close-range photogrammetry. This paper compares two approaches based on the use of a wearable MMS and the use of an in-house built photogrammetric multi-camera prototype. The comparison aims to assess the applicability of the two techniques in this field, evaluating their advantages and disadvantages in surveying a historical garden and extracting information for tree inventory, such as the DBH (Diameter at Breast Height) and canopy footprint. We compared the practicality of surveying and processing operations; and the quality and characteristics of the point clouds obtained. Both systems produced a dense representation of the terrain. The multi-camera survey resulted to be more defined due to the lower noise of the point cloud but incomplete in the definition of tree canopies. DBH of tree trunks can be extracted with both systems, except for thinner and finer diameter trunks detected by the MMS approach but not always by the multi-camera. The MMS approach proved more effective thanks to a shorter survey time required to cover an equal area and the fact that the MMS survey alone is sufficient for the geometric description of trees. In contrast, the multi-camera approach cannot avoid integration with an aerial survey for canopy reconstructio
Preliminary survey of historic buildings with wearable mobile mapping systems and uav photogrammetry
In cultural heritage, three-dimensional documentation of historic buildings is fundamental for conservation and valorisation projects. In recent years, the consolidated tools and methods: Terrestrial Laser Scanning (TLS) and close-range photogrammetry, have been joined by portable Mobile Mapping Systems (MMSs), which can offer significant advantages in terms of speed of survey operations at the price of reduced accuracy. The reduction of survey times and, therefore, costs makes the application of MMS techniques ideal for the preliminary stages of analysis of historical artifacts, when a rapid survey is indispensable for estimating the costs of conservation interventions. In this paper, we present a methodology for the expeditious survey of historic buildings and the surrounding urban fabric that is based on the use of an MMS and an Unmanned Aerial Vehicle (UAV). The MMS is the Gexcel Heron MS Twin color. It was used to survey two architecture of interest and the urban context surrounding them from the ground level. The UAV is the DJI Mini 2, used to integrate the terrestrial survey by acquiring the buildings' roofs. The case study presented in the paper is the survey of San Clemente and San
Zeno al Foro churches, two historic churches in the city centre of Brescia (Italy). The result are a complete point cloud of the two buildings and a metric virtual tour of all spaces. These results were made available to the architects through the Cintoo web platform to plan future activities
Quasiparticles dynamics in high-temperature superconductors far from equilibrium: an indication of pairing amplitude without phase coherence
We perform time resolved photoelectron spectroscopy measurements of optimally
doped \tn{Bi}_2\tn{Sr}_2\tn{CaCu}_2\tn{O}_{8+\delta} (Bi-2212) and
\tn{Bi}_2\tn{Sr}_{2-x}\tn{La}_{x}\tn{Cu}\tn{O}_{6+\delta} (Bi-2201). The
electrons dynamics show that inelastic scattering by nodal quasiparticles
decreases when the temperature is lowered below the critical value of the
superconducting phase transition. This drop of electronic dissipation is
astonishingly robust and survives to photoexcitation densities much larger than
the value sustained by long-range superconductivity. The unconventional
behaviour of quasiparticle scattering is ascribed to superconducting
correlations extending on a length scale comparable to the inelastic path. Our
measurements indicate that strongly driven superconductors enter in a regime
without phase coherence but finite pairing amplitude. The latter vanishes near
to the critical temperature and has no evident link with the pseudogap observed
by Angle Resolved Photoelectron Spectroscopy (ARPES).Comment: 7 pages, 5 Figure
Theoretical description of high-order harmonic generation in solids
We consider several aspects of high-order harmonic generation in solids: the
effects of elastic and inelastic scattering; varying pulse characteristics; and
inclusion of material-specific parameters through a realistic band structure.
We reproduce many observed characteristics of high harmonic generation
experiments in solids including the formation of only odd harmonics in
inversion-symmetric materials, and the nonlinear formation of high harmonics
with increasing field. We find that the harmonic spectra are fairly robust
against elastic and inelastic scattering. Furthermore, we find that the pulse
characteristics play an important role in determining the harmonic spectra.Comment: Accepted for publication in the New Journal of Physic
SURVEY OF HISTORICAL GARDENS: MULTI-CAMERA PHOTOGRAMMETRY VS MOBILE LASER SCANNING
This paper presents an investigation into the characterization of historical gardens by comparing two 3D survey methodologies. In
this context, approaches employing terrestrial laser scanning are considered the most accurate, while Mobile Mapping Systems
(MMSs) are considered promising due to their extreme productivity. Less common is the use of close-range photogrammetry. This
paper compares two approaches based on the use of a wearable MMS and the use of an in-house built photogrammetric multi-camera
prototype. The comparison aims to assess the applicability of the two techniques in this field, evaluating their advantages and
disadvantages in surveying a historical garden and extracting information for tree inventory, such as the DBH (Diameter at Breast
Height) and canopy footprint. We compared the practicality of surveying and processing operations; and the quality and
characteristics of the point clouds obtained. Both systems produced a dense representation of the terrain. The multi-camera survey
resulted to be more defined due to the lower noise of the point cloud but incomplete in the definition of tree canopies. DBH of tree
trunks can be extracted with both systems, except for thinner and finer diameter trunks detected by the MMS approach but not
always by the multi-camera. The MMS approach proved more effective thanks to a shorter survey time required to cover an equal
area and the fact that the MMS survey alone is sufficient for the geometric description of trees. In contrast, the multi-camera
approach cannot avoid integration with an aerial survey for canopy reconstruction
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