93 research outputs found
Innovative Tools For Planning, Analysis, and Management of UAV Photogrammetric Surveys
No full textThe Unmanned Aerial System (UAV) is widely used in the photogrammetric surveys both for structures and small areas. The geomatics approach, for the several applications where the 3D modeling is required, focuses the attention on the metric quality of the final products of the survey. As widely known, the quality of results derives from the quality of images acquisition phase, which needs an accurate planning phase. Actually, the planning phase is typically managed using dedicated tools, adapted from the traditional aerial-photogrammetric flight plan. Unfortunately, UAV flight has features completely different from the traditional one, hence the use of UAV for photogrammetric applications today requires a growth in the planning knowledge.
The basic idea of the present research work is to provide a tool for planning a photogrammetric survey with UAV, called “Unmanned Photogrammetric Office” (U.Ph.O.), that considers the morphology of the object, the effective visibility of its surface, in the respect of the metric precisions. The usual planning tools require the classical parameters of a photogrammetric planning: flight distance from the surface, images overlaps and geometric parameters of the camera. The created “Office suite” U.Ph.O. allows a realistic planning of a photogrammetric survey, requiring additionally an approximate knowledge of the Digital Surface Model (DSM) and the attitude parameters, potentially changing along the route. The planning products will be the realistic overlapping of the images, the Ground Sample Distance (GSD) and the precision on each pixel taking into account the real geometry.
The different tested procedures, the solution proposed to estimates the realistic precisions in the particular case of UAV surveys and the obtained results, are described in this thesis work, with an overview on the recently development of UAV surveys and technologies related to them
Experimental Tests on The Benefits of a more rigorous model in IMU/GPS System Calibration
No full textL'impiego di reti regionali GNSS per la determinazione di traiettorie di veicoli ferroviari in tempo reale
No full text
Fotogrammetria diretta: considerazioni e proposte operative
No full textDopo alcuni anni di lavoro sui sistemi integrati IMU/GPS in fotogrammetria aerea, si riesaminano, anche alla luce degli risultati preliminari della seconda fase del progetto COFIN2002, alcuni dei temi di maggiore interesse: la calibrazione e la sua effettiva importanza per la georeferenziazione, la presenza di parallassi residue nei modelli orientati direttamente, la compensazione integrata IMU/GPS con misure sui fotogrammi, le capacità del sistema in termini di precisione assoluta, l’affidabilità. L’obiettivo è quello di un contributo alla discussione sulle questioni affrontate dal test COFIN2002 "I sistemi inerziali integrati di posizionamento nella Fotogrammetria aerea"
Improving tree species classification using UAS multispectral images and texture measures
No full textThis paper focuses on the use of ultra-high resolution Unmanned Aircraft Systems (UAS) imagery to classify tree species. Multispectral surveys were performed on a plant nursery to produce Digital Surface Models and orthophotos with ground sample distance equal to 0.01 m. Different combinations of multispectral images, multi-temporal data, and texture measures were employed to improve classification. The Grey Level Co-occurrence Matrix was used to generate texture images with different window sizes and procedures for optimal texture features and window size selection were investigated. The study evaluates how methods used in Remote Sensing could be applied on ultra-high resolution UAS images. Combinations of original and derived bands were classified with the Maximum Likelihood algorithm, and Principal Component Analysis was conducted in order to understand the correlation between bands. The study proves that the use of texture features produces a significant increase of the Overall Accuracy, whose values change from 58% to 78% or 87%, depending on components reduction. The improvement given by the introduction of texture measures is highlighted even in terms of User's and Producer's Accuracy. For classification purposes, the inclusion of texture can compensate for difficulties of performing multi-temporal surveys
Un esperimento per la determinazione di traiettorie di veicoli ferroviari con il GPS in modalità NRTK.
No full textAnalisi e sperimentazione di algoritmi per il riconoscimento automatico dei tetti e studio di fattibilità per l'utilizzo dell'energia solare
No full textAn analytical-numerical approach to the hydraulics of floating debris in river channels
No full textA new simplified approach is developed for the channel flow dynamics under woody debris transport. A continuous carpet of debris is considered, covering a uniform stationary current. Due to the floating debris the shear stresses in the fluid domain are affected. As a result, the velocity profile is different from the free surface flow. The simple model proposed here is able to capture the essential features of flow response to woody debris transport. Velocity and stress profiles are analytically derived for
laminar flow and compared with the zero debris condition. More realistic turbulent currents are simulated with the Reynolds equations where turbulent stresses are modeled by the simple mixing length concept. Validation is carried out by comparison with experimental velocity profiles and with direct numerical simulation of the Navier Stokes Equations. Synthetic diagrams are proposed for the calculation of the flow velocity and the bed shear stresses in terms of the relevant non-dimensional parameters
- …
