86,537 research outputs found
Joint detection and localization of vessels at sea with a GNSS-Based multistatic radar
No full textThis paper addresses the exploitation of global navigation satellite systems as opportunistic sources for the joint detection and localization of vessels at sea in a passive multistatic radar system. A single receiver mounted on a proper platform (e.g., a moored buoy) can collect the signals emitted by multiple navigation satellites and reflected from ship targets of interest. This paper puts forward a single-stage approach to jointly detect and localize the ship targets by making use of long integration times (tens of seconds) and properly exploiting the spatial diversity offered by such a configuration. A proper strategy is defined to form a long-time and multistatic range and Doppler (RD) map, where the total target power can be reinforced with respect to, in turn, the case in which the RD map is obtained over a short dwell and the case in which a single transmitter is employed. The exploitation of both the long integration time and the multiple transmitters can greatly enhance the performance of the system, allowing counteracting the low-power budget provided by the considered sources representing the main bottleneck of this technology. Moreover, the proposed single-stage approach can reach superior detection performance than a conventional two-stage process where peripheral decisions are taken at each bistatic link and subsequently the localization is achieved by multilateration methods. Theoretical and simulated performance analysis is proposed and also validated by means of experimental results considering Galileo transmitters and different types of targets of opportunity in different scenarios. Obtained results prove the effectiveness of the proposed method to provide detection and localization of ship targets of interest
Multi-transmitter ship target detection technique with GNSS-based passive radar
No full textThe exploitation of the Global Navigation Satellite Systems (GNSS) as transmitters of opportunity in passive radar systems for maritime surveillance is particularly attractive because of the main advantages consisting in a global coverage (even in open sea) and in the availability of multiple sources (different satellites and constellations). The main drawback stays in the restricted power budget provided by navigation satellites. This characteristic makes necessary to conceive, define and develop detection techniques able to overcome such limitation. To this aim this work proposes a range-Doppler domain processing technique able to integrate over long time intervals the returns from a moving target illuminated by multiple GNSS transmitters. Several examples are shown to demonstrate the effectiveness of the proposed approach
Top-down and Bottom-up. Testing a mixed approach to the generation of priorities for sustainable urban mobility
No full textThis paper contributes to the debate on how to make operational the concept of sustainable urban
mobility and advocates the use of a mixed – top-down and bottom-up – approach to the generation of
priorities for sustainable urban mobility.
In particular, we tested whether a common list of priorities remain valid after a participated scrutiny
performed in seven urban areas of southern Italy. The test was based on a 3-steps procedure. In step
1, we used a common conceptual framework (based on Mameli and Marletto, 2014) to generate seven
area-specific lists of priorities. In step 2, local stakeholders participated to deliberative meetings aimed
at amending or deleting each of the proposed priorities, as well as adding new ones. In step 3, citizens'
opinion was gathered through seven sample polls and used to rank the list of priorities resulting from
stakeholders' deliberation.
The test generated three main results: 1) Deliberation between local stakeholders was useful for
adapting common priorities to the characteristics of each area. But, with the exception of Reggio
Calabria – an urban area with very specific features –, the structure of the starting common conceptual
framework was not altered. 2) Surveys on citizens' opinion were useful, not only for ranking priorities,
but also for taking into account the relevant differences between car users and the rest of the
population. 3) With great caution, reference may be made to a common set of six top priorities
referring to: (accessibility by and economic sustainability of) public transport, air pollution, accidents,
greenhouse gasses and transport waste. These top priorities cover all three dimension of sustainability
(environmental, social and economic)
Passive radar imagery of ship targets by using navigation satellites transmitters of opportunity
No full textThis paper considers the possibility to extract features of vessels at sea with a GNSS-based passive radar system. To this purpose, a passive imaging mode has been defined to form bistatic ISAR images of the detected ship. Then, proper range and cross-range scaling factors have been derived, so that relevant features of the target such as its length can be obtained, potentially enabling target recognition procedures. Experimental results obtained with Galileo satellites demonstrate the effective possibility of the proposed approach to extract relevant features of ship targets of interest, thus providing advanced capabilities to the GNSS-based radar for maritime surveillance applications
Maritime moving target indication using passive GNSS-based bistatic radar
No full textThis paper is a first introduction to the concept of using global navigation satellite systems (GNSS) as illuminators of opportunity in a passive bistatic real-time radar system for maritime target indication applications. An overview of the system concept and the signal processing algorithms for moving target indication is provided. To verify the feasibility of the system implementation as well as test the developed signal processing algorithms, an experimental test bed was developed and the appropriate experimental campaign with the new Galileo satellites and a ferry as the target was carried out. The results confirm the system concept and its potential for multistatic operation, with the ferry being detected simultaneously by two satellites
Fast terrain modelling for hydrogeological risk mapping and emergency management: the contribution of high-resolution satellite SAR imagery
No full textGeomatic tools fast terrain modelling play a relevant role in hydrogeological risk mapping and emergency management. Given their complete independence from logistic constraints on the ground (as for airborne data collection), illumination (daylight), and weather (clouds) conditions, synthetic aperture radar (SAR) satellite systems may provide important contributions in terms of digital surface models (DSMs) and digital elevation models (DEMs). For this work we focused on the potential of high-resolution SAR satellite imagery for DSM generation using an interferometric (InSAR) technique and using a revitalized radargrammetric stereomapping approach. The goal of this work was just methodological. Our goal was to illustrate both the fundamental advantages and drawbacks of the radargrammetric approach with respect to the InSAR technique for DSM generation, and to outline their possible joint role in hydrogeological risk mapping and emergency management. Here, it is worth mentioning that radargrammetry procedures are independent of image coherence (unlike the interferometric approach) and phase unwrapping, as well as of parsimony (only a few images are necessary). Therefore, a short time is required for image collection (from tens of minutes to a few hours), thanks to the independence from illumination and weather. The most relevant obstacles of the technique are speckle and the lack of texture impact on image matching, as well as the well-known deformations of SAR imagery (layover and foreshortening), which may produce remarkable difficulties with complex morphologies and that must be accounted for during acquisition planning. Here, we discuss results obtained with InSAR and radargrammetry applied to a COSMO-SkyMed SpotLight triplet (two stereopairs suited for radargrammetry and InSAR, sharing one common image) acquired over suburbs of San Francisco (United States), which are characterized by mixed morphology and land cover. We mainly focused on urban areas and zones covered by bare soil and rocks. Image processing was performed using the well-known commercial software SARscape® for InSAR, and the radargrammetric suite implemented in SISAR, software developed at the Geodesy and Geomatic Division of the University of Rome “La Sapienza”. Global accuracies were approximately 5 m using both approaches. However, several differences in terrain morphology reconstruction were determined and are underlined and evaluated here, as well as a possible way to further enhance the results using the integration of InSAR and radargrammetry
Evaluation and comparison of different radargrammetric approaches for Digital Surface Models generation from COSMO-SkyMed, TerraSAR-X, RADARSAT-2 imagery: Analysis of Beauport (Canada) test site
No full textIn this manuscript we analyze the potentialities of the radargrammetric DSMs generation using high resolution SAR imagery acquired by three different platforms (COSMO-SkyMed, TerraSAR-X and RADARSAT-2), with particular attention to geometric orientation models. Two orientation models are considered and compared: Toutin's model (Canada Center for Remote Sensing), implemented in the commercial software package PCI-Geomatica and based on Ground Control Points (GCPs), and the radargrammetric model implemented in the scientific software SISAR (University of Rome La Sapienza), based on images metadata orbital information only. Moreover, a comparison between the DSMs following the image matching approaches implemented in PCI-Geomatica and SISAR has been performed. The analysis has been carried out over Beauport test site (Quebec, Canada), where three overlapping stereopairs, one for each of the mentioned platform, were acquired and a LiDAR ground truth and a dense set of GNSS Check points (CPs) are available. The presented results appear promising: DSMs accuracy are within 4 and 5. m for all sensors, independently from orientation model (with or without GCP) and image matching approach, provided good relative orientation is guaranteed, what mainly attains to the quality of metadata orbital information
Alpha-rhythm stimulation using brain entrainment enhances heart rate variability in subjects with reduced HRV
No full textIn the present research, we have used the brain en- trainment (BWE) treatment simultaneously record- ing time series data of R-R intervals of the ECG dur- ing rest condition. In detail, we have used alpha brain stimulation and we have found that it induces an en- hancement of HRV, particularly in Total Variability and Vagal Modulation activities. The experiment has been performed by us on ten subjects with age rang- ing from 20 to 70 years old. The risk induced from low HRV is by this time well known in literature. Therefore, the obtained result promises to be of valu- able interest not only in terms of the basic neurologi- cal investigation but also because it delineates new possibilities in terms of clinical application
DSM generation from optical and SAR high resolution satellite imagery: methodology, problems and potentialities
No full textNowadays high resolution optical and Synthetic Aperture Radar (SAR) satellite sensors offer interesting potentialities for Digital Surface Models (DSMs) generation. Both optical and SAR imagery are characterized by proper deformations and noise due to the different acquisition geometries and processes, which have to be duly taken into account during the DSM generation procedure in order to fully exploit the aforementioned potentialities. This work aims at evaluating the performances of high resolution optical and SAR imagery for DSMs generation over the same testfield area, where a dense network of GCPs and a LiDAR DSM are available as ground truth data. The image processing and DSMs generation are carried out with the packages SISAR (Software Immagini Satellitari ad Alta Risoluzione) and SAT-PP (SATellite image Precision Processing) while an additional comparison is performed using PCI Geomatica 2012
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