1,721,016 research outputs found
Monitoraggio delle strutture tramite tecniche topografiche innovative e tradizionali
No full textLa ricerca ha riguardato lo studio e l’applicazione di strumenti topografci digitali di ultima generazione di elevata precisione metrica (stazioni totali, laser scanner terrestri (TLS), livelli digitali automatici, ricevitori satellitari GPS/GNSS), nell’ambito del monitoraggio di edifci/strutture e manufatti in genere. Particolare attenzione è stata dedicata all’integrazione tra le differenti strumentazioni topografche; integrazione analizzata studiando le potenzialità degli strumenti sia in termini di precisione, sia in termini di tipologia e quantità d’informazioni deducibili dai rilievi ripetuti nel tempo
Stazioni mareografiche e stazioni GNSS integrate: l'esempio di Porto Garibaldi e di Ravenna.
No full textUsing dji phantom 4 rtk drone for topographic mapping of coastal areas
No full textImagery acquisition systems by Unmanned Aerial Vehicles (UAVs) have been rapidly evolving within the last few years. In mapping applications, it is the introduction of a considerable amount of Ground Control Points (GCPs) that enables the final reconstruction of a real-scale framed model. Since the survey of GCPs generally requires the use of total stations or GNSS receivers in Real Time Kinematic (RTK), either with or without a Network approach (NRTK), this on-site operation is particularly time consuming. In addition, the lack of clearly image-recognizable points may force the use of artificial markers (signalised GCPs) whenever no features are naturally available in the field. This implies a real waste of time for the deployment of the targets, as well as for their recovery. Recently, aircrafts' manufacturers have integrated the on-board RTK capability on their UAVs. In such a way, the high precision GNSS system allows the 3D position detection of the camera at the time of each capture within few centimetres. In this work, we tested the DJI Phantom 4 RTK for the topographic survey of a coastal section in the Northern Adriatic Sea (Italy). The flights were performed flying at an 80 m altitude to ensure a Ground Sample Distance (GSD) of about 2 centimetres. The site extended up to 2 kilometres longitudinally. The results confirm that the on-board RTK approach really speeds up the precise mapping of coastal regions and that a single GCP may be needed to make a reliable estimation of the focal length
Test statistici in reti GPS
No full textSummary.- We describe some statistical tests for GPS networks with measures of baselines, as known from international references. One-dimensional, two-dimensional and three-dimensional tests are used for blunders identification. We estimate internal and external reliability in a GPS network for the one-dimensional test. The DIA procedure has been used for the statistical analysis. We show the gained results concerning the case of “Rete di Raffittimento primario della Rete IGM95 della provincia di Ferrara”
Medieval cultural heritage, from 3D survey to data management: the castle of Canossa
No full textIn the cultural heritage knowledge path, the survey process assumes a primary role as a tool to analyze and interpret through bibliographic and iconographic analysis and the study of reality. The case study analyzed in the article is the Castle of
Canossa, the epicenter of some critical events in medieval times. The authors describe the first part of the research, mainly focused on the integrated survey
process between active and passive techniques at architectural and territorial scales. Several geometrical validation steps have been introduced to
verify the reliability of the 3D acquisition and historical reconstruction. The paper highlighted the crucial relationship between territorial heritage and
buildings, laying the groundwork for a more articulated analysis of the entire architectural complex. The final aim is to realize a 3D BIM model
that represent the current and the original architectures in the same type of environment
PRIN 2020 NASA4SHA Project: A combined regional velocity field of Northern Italy
No full textThe activity presented in this note is part of the PRIN 2020 NASA4SHA Project (Fault segmentation and seismotectonics of active thrust systems: the Northern Apennines and Southrn Alps laboratorie for new Seismic Hazard Assessments in northern Italy). The project's objective is to define, through a multidisciplinary approach including geological, geophysical, seismological, paleoseismological, and geodetic methods at various scales (regional and local), the geometry and kinematics of the main compressive systems in the central – estern Southern Alps and Northern Apennines. Geodetic methods make it possible to reconstruct the ongoing deformation rate of the Earth's surface at regional and local scales (with high-density networks). This information, combined with the 3D model of tectonic structures present in the investigated region, can indicate areas/volumes where the tectonic activity and the deformation are either more or less intense, enabling a focus on fault zones where the stress is increasingly accumulated. We analyzed data from continuous GNSS (Global Navigation Satellite Systems) stations covering the entire study area, belonging to the RING (Rete Integrata Nazionale GNSS) and FReDNet (Friuli Regional Deformation Network) networks, managed by INGV (Istituto Nazionale di Geofisica e Vulcanologia) and OGS (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS) respectively, together with data from other permanent networks, managed by various institutions. In addition, we have resurveyed some vertices of the IGM95 geodetic network, focusing on local transects orthogonal to the main compressive structures, and we have analyzed the new discontinuous GNSS observations together with the previous ones performed in the past by IGM (Istituto Geografico Militare) on the same vertices
Multispectral UAV monitoring of submerged seaweed in shallow water
No full textThe sudden algal bloom in shallow water may be a serious problem for sea coastal economy based on clams farming because it leads quickly to anoxia conditions with the consequent death of the molluscs. In order to detect the rise of algae, normally satellite remote sensing is used, exploiting the higher response in the near infrared wavelengths. A recent progress in monitoring this phenomenon derives from the availability of unmanned aerial vehicles (UAVs) equipped with lightweight multispectral cameras. Such technique makes it possible to acquire detailed spectral information with narrow bands attaining an assessment of the algal bloom at both high geometric and radiometric resolutions. In this work, we tested the MicaSense RedEdge-M multispectral camera mounted on a DJI Phantom 3 Professional aircraft to map submerged seaweeds and assess their evolution with particular regard to the importance of the radiometric calibration of raw imageries using a Downwelling Light Sensor (DLS) and a known reflectance panel. The case study is the lagoon of Goro (Northern Adriatic Sea, Italy), a crucial environment for the clams farming in the Emilia-Romagna region. Digital images acquired in two subsequent flights were processed with either Agisoft PhotoScan Professional and Pix4D Mapper Pro varying the calibration strategies. After a pre-analysis, we applied two different approaches for the seaweed detection: NDVI and maximum likelihood classification. All the tests performed in this study confirm that the monitoring over time with a multispectral lightweight camera mounted on a UAV is possible, but also that by applying proper radiometric corrections, most accurate and reliable results can be achieved
Quality assessment of photogrammetric models for façade and building reconstruction using dji phantom 4 rtk
No full textAerial photogrammetry by Unmanned Aerial Vehicles (UAVs) is a widespread method to perform mapping tasks with high-resolution to reconstruct three-dimensional (3D) building and façade models. However, the survey of Ground Control Points (GCPs) represents a time-consuming task, while the use of Real-Time Kinematic (RTK) drones allows for one to collect camera locations with an accuracy of a few centimeters. DJI Phantom 4 RTK (DJI-P4RTK) combines this with the possibility to acquire oblique images in stationary conditions and it currently represents a versatile drone widely used from professional users together with commercial Structure-from-Motion software, such as Agisoft Metashape. In this work, we analyze the architectural application of this drone to the photogrammetric modeling of a building with particular regard to metric survey specifications for cultural heritage for 1:20, 1:50, 1:100, and 1:200 scales. In particular, we designed an accuracy assessment test signalizing 109 points, surveying them with total station and adjusting the measurements through a network approach in order to achieve millimeter-level accuracy. Image datasets with a designed Ground Sample Distance (GSD) of 2 mm were acquired in Network RTK (NRTK) and RTK modes in manual piloting and processed both as single façades (S–F) and as an overall block (4–F). Subsequently, we compared the results of photogrammetric models generated in Agisoft Metashape to the Signalized Point (SP) coordinates. The results highlight the importance of processing an overall photogrammetric block, especially whenever part of camera locations exhibited a poorer accuracy due to multipath effects. No significant differences were found between the results of network real-time kinematic (NRTK) and real-time kinematic (RTK) datasets. Horizontal residuals were generally comparable to GNSS accuracy in NRTK/RTK mode, while vertical residuals were found to be affected by an offset of about 5 cm. We introduced an external GCP or used one SP per façade as GCP, assuming a poorer camera location accuracy at the same time, in order to fix this issue and comply with metric survey specifications for the widest architectural scale range. Finally, both S–F and 4–F projects satisfied the metric survey requirements of a scale of 1:50 in at least one of the approaches tested
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