50 research outputs found
New tecnologies for mobile mapping
No full textThis paper deals with the development of a low cost UAV (Unmanned Aerial Vehicle) devoted to early impact phase in case of environmental disasters, based on geomatics techniques. "Pelican" is a low-cost UAV prototype equipped with a photogrammetric payload that will allows reconnaissance operations in remote areas and rapid mapping production. Different digital sensors installed in the payload allow to acquire high resolution frame images. Furthermore a GPS/INS unit will enable an automated navigation (except take-off and landing). The project is supported by ITHACA (Information Technology for Humanitarian Assistance, Cooperation and Action), an association founded by Politecnico di Torino and SiTI (Istituto Superiore sui Sistemi Territoriali per l'Innovazione) in cooperation with WFP (World Food Programme) and some private and public organisms, with the main goal to carry on operational and research activities in the field of geomatics for analysis, evaluation and mitigation of natural and manmade hazards. The main technical features of the UAV and the on-board payload are detailed described in the first part of the paper. Furthermore first results of stereopairs orientation, case studies and further developments are presented
Fast and Simple Qubit-Based Synchronization for Quantum Key Distribution
No full textWe propose Qubit4Sync, a synchronization method for quantum-key-distribution (QKD) setups, based on the same qubits exchanged during the protocol and without requiring additional hardware other than that necessary to prepare and measure the quantum states, in a similar fashion to the clock recovery used in classical communications. Our approach introduces a cross-correlation algorithm with low computational complexity for high channel losses. We test the robustness of our scheme in a real QKD implementation, and we believe it may find application in other quantum communication protocols
100 kHz satellite laser ranging demonstration at Matera Laser Ranging Observatory
No full textThe new challenges related to the monitoring of Earth’s shape and motion have led the global geodetic observing system to set more stringent requirements on the precision and stability of the terrestrial reference frame (TRF). The achievement of this ambitious goal depends on the improvement of space geodesy techniques, satellite laser ranging (SLR) in particular, being the main instrument for TRF realization. In this work, we study the potential of very high repetition rate SLR by performing a data acquisition campaign with an Ekspla “Atlantic 60” 100 kHz repetition rate laser at the Matera Laser Ranging Observatory (MLRO). This system constitutes an increase of two orders of magnitude in repetition rate with respect to the current SLR stations, while maintaining a good single-shot timing performance. The system has been active for 4 consecutive nights, consistently tracking several low Earth orbit satellites as well as LAGEOS 1 and 2. The results have shown a single-shot time jitter close to other stations, but with unprecedented statistics for ≈ 10 ps single-shot precision. The analysis of the residuals of LAGEOS satellites allowed us to identify multiple peaks, due to the retroflection from different corner cubes. This opens up the possibility of attitude determination of retroreflector arrays, as well as a new method for spin rate measurement
Low cost UAV for post-disaster assessment
No full textThe main objective of early impact analysis after a disaster is to produce georeferenced data about the affected areas, in support of humanitarian action. Crucial information are the identification of the hitten areas and the estimation of the number of people involved. Satellite imageries are mainly used as input data for early impact analysis at small and medium map scale (i.e. floods events). Analyses aimed at defining the damages to infrastructures and/or to facilities (i.e. earthquakes) require suitable data for large scale analyses, as far as high resolution satellite images. Unfortunately, such images are not always available in a few days after the event, therefore in situ surveys are preferred. ITHACA (Information Technology for Humanitarian Assistance, Cooperation and Action) - a non profit association with the main goal to carry on operational and research activities in the field of geomatics for analysis, evaluation and mitigation of natural and manmade hazards - is developing a low cost mini UAV (Unmanned Aerial Vehicle) devoted to the early impact analyses. The aim of the UAV project is to develop a low cost aerial platform capable of autonomous flight and equipped with a photogrammetric payload for rapid mapping purposes. The main requirements for this type of UAV are to be easily transportable and usable on the field, autonomously, by a couple of operators. Therefore, it was decided to customise the MH2000 platform designed and patented by the Department of Aerospace Engineering (DIASP) of the Politecnico di Torino. The current configuration of the UAV allows to carry onboard digital sensors for video and imagery acquisition. The sensors are mounted in a pod placed on the belly of the fuselage, that can be remotely controlled through a direct link to the autopilot board that allows to schedule automatic acquisitions at defined time intervals or planned positions. A real-time video downlink of the over-passed areas is provided. Several test flights were performed in order to set up the control parameters of UAV and to analyse the capability of performing autonomous flights according to the defined flight-path. Two photogrammetric surveys aimed at calculating the achievable 3-D accuracy have been peformed over a flight centre and an archaeological site (both located in Italy). Results of both tests will be shown in detail
Versatile and concurrent FPGA-based architecture for practical quantum communication systems
No full textThis work presents a hardware and software architecture which can be used in those systems that implement practical Quantum Key Distribution (QKD) and Quantum Random Number Generation (QRNG) schemes. This architecture fully exploits the capability of a System-on-a-Chip (SoC) which comprehends both a Field Programmable Gate Array (FPGA) and a dual core CPU unit. By assigning the time-related tasks to the FPGA and the management to the CPU, we built a flexible system with optimized resource sharing on a commercial off-the-shelf (COTS) evaluation board which includes a SoC. Furthermore, by changing the dataflow direction, the versatile system architecture can be exploited as a QKD transmitter, QKD receiver and QRNG control-acquiring unit. Finally, we exploited the dual core functionality and realized a concurrent stream device to implement a practical QKD transmitter where one core continuously receives fresh data at a sustained rate from an external QRNG source while the other operates with the FPGA to drive the qubits transmission to the QKD receiver. The system was successfully tested on a long-term run proving its stability and security. This demonstration paves the way towards a more secure QKD implementation, with fully unconditional security as the QKD states are entirely generated by a true random process and not by deterministic expansion algorithms. Eventually, this enables the realization of a standalone quantum transmitter, including both the random numbers and the qubits generation
Towards Automatic Registration of 3-D Views
No full textRecent advances in the field of laser scanning technology along with the availability of more powerful computing resources have favoured the increasing interest of surveyors, architects, archaeologists towards laser scanners technology as a very promising alternative for cultural heritage surveying. Thousands of points can be acquired in short time with an accuracy that is adequate to build 3D models for single objects so as for whole environments. At the present, resulting 3D digital models offer an invaluable mean for documentation, archiving, structural analysis and restoration of the large amount of objects spanning from Civil Engineering to Cultural Heritage assets. Usually, the end products of the whole workflow (survey and modeling) are VR representations (Vrml, Flash), movies (AVI, DVx, Mpeg), Dense Digital Surface Models (DDSM) and orthophotos as well. The creation of a 3D model requires a lot of data about the object surface or volume, which have then to be somehow aggregated, regardless the data structure and the acquisition device used. In most cases, the data registration step is based on ICP, that iterativelly finds the mutual orientation between two range maps, starting from an initial estimate provided by an operator. This approach is often time-consuming, increases the final cost of the 3D model and represents one of the major limits to the wide spreading of real object models.
In this paper an overview of an automatic range data registration system is presented, whose theoretical basis rely on the previous works of A. E. Johnson and L. Lucchese. The former proposed an innovative solution for the recognition of similarities between 3D surfaces, introducing the spin-image concept, while the latter developed an alternative procedure (Frequency Domain technique) for 3-D motion estimation of free-form surfaces, based on the Fourier transform of the 3-D intensity function, implicitly described by the registered time-sequences of range data
Testing the speed of “spooky action at a distance” in a tabletop experiment
No full textNonlocality, probably the principal friction between Quantum Physics and Relativity, disturbed the physicists even more than realism since it looks to originate superluminal signalling, the Einsteinian “Spooky action at a distance”. From 2000 on, several tests to set lower bounds of the Spooky action at a distance velocity (cβt,max) have been performed. They are usually based on a Bell Test performed in km long and carefully balanced experimental setups to fix a more and more improved bound making some assumptions dictated by the experimental conditions. By exploiting advances in quantum technologies, we performed a Bell’s test with an improved bound in a tabletop experiment of the order of few minutes, thus being able to control parameters otherwise uncontrollable in an extended setup or in long lasting experiments.Full Tex
Quantum-secured time transfer between precise timing facilities: a field trial with simulated satellite links
No full textGlobal Navigation Satellite Systems (GNSSs), such as GPS and Galileo, provide precise time and space coordinates globally and constitute part of the critical infrastructure of modern society. To reliably operate GNSS, a highly accurate and stable system time is required, such as the one provided by several independent clocks hosted in Precise Timing Facilities (PTFs) around the world. The relative clock offset between PTFs is periodically measured to have a fallback system to synchronize the GNSS satellite clocks. The security and integrity of the communication between PTFs is of paramount importance: if compromised, it could lead to disruptions to the GNSS service. Therefore, securing the communication between PTFs is a compelling use-case for protection via Quantum Key Distribution (QKD), since this technology provides information-theoretic security. We have performed a field trial demonstration of such a use-case by sharing encrypted time synchronization information between two PTFs, one located in Oberpfaffenhofen (Germany) and one in Matera (Italy)—more than 900 km apart. To bridge this large distance, a satellite-QKD system is required, plus a “last-mile” terrestrial link to connect the optical ground station (OGS) to the actual location of the PTF. In our demonstration, we have deployed two full QKD systems to protect the last-mile connection at both locations and have shown via simulation that upcoming QKD satellites will be able to distribute keys between Oberpfaffenhofen and Matera, exploiting already existing OGSs
Tecniche di registrazione
No full textSono illustrate le tecniche e gli algoritmi comunemente impiegati per registrare (allineare) i modelli 3-D parziali ottenuti dalle diverse scansioni, al fine di ricomporli in un modello numerico generale, trasformando le coordinate dei punti costituenti im un sistema di riferimento univoco
Archaeological site monitoring: UAV photogrammetry can be an answer
No full textDuring archaeological excavations it is important to monitor the new excavated areas and findings day by day in order to be able to plan future excavation activities. At present, this daily activity is usually performed by using total stations, which survey the changes of the archaeological site: the surveyors are asked to produce day by day draft plans and sections which allow archaeologists to plan their future activities. The survey is realized during the excavations or just at the end of every working day and drawings have to be produced as soon as possible in order to allow the comprehension of the work done and to plan the activities for the following day. By using this technique, all the measurements, even those not necessary for the day after, have to be acquired in order to avoid a ‘loss of memory'. A possible alternative to this traditional approach is aerial photogrammetry, if the images can be acquired quickly and at a taken distance able to guarantee the necessary accuracy of a few centimeters. Today the use of UAVs (Unmanned Aerial Vehicles) can be considered a proven technology able to acquire images at distances ranging from 4 m up to 20 m: and therefore as a possible monitoring system to provide the necessary information to the archaeologists day by day. The control network, usually present at each archaeological site, can give the stable control points useful for orienting a photogrammetric block acquired by using an UAV equipped with a calibrated digital camera and a navigation control system able to drive the aircraft following a pre-planned flight scheme. Modern digital photogrammetric software can solve for the block orientation and generate a DSM automatically, allowing rapid orthophoto generation and the possibility of producing sections and plans. The present paper describes a low cost UAV system realized by the research group of the Politecnico di Torino and tested on a Roman villa archaeological site located in Aquileia (Italy), a well-known UNESCO WHL site. The results of automatic orientation and orthophoto production are described in terms of their accuracy and the completeness of information guaranteed for archaeological site excavation managemen
