1,720,994 research outputs found
Realizzazione di un sistema di geolocalizzazione web-based in ambiente open source mediante l’impiego dell’infrastruttura tecnologica della rete gsm-sms
No full textOggetto di questa tesi è stato la realizzazione di un sistema integrato che consente la localizzazione in tempo reale degli utenti ad un
pubblico vasto come quello di internet, senza la necessità di utilizzare alcun software se non un semplice browser, ad un costo molto
ridotto.
Il principio di funzionamento è il seguente: un utente munito di un ricevitore GPS integrato con un modem GSM invia la propria
posizione ad un server WEB attraverso la rete GSM mediante l’invio di un messaggio di testo (SMS) nel formato NMEA0183.
Questa informazione viene inserita in un geodatabase consentendo al software di rendering cartografico l’interpretazione del dato ed
il posizionamento corretto su di una cartografia di sfondo.
Tutti coloro che sono abilitati (mediante una procedura di autenicazione) possono localizzare l’utente del sistema che ha inviato
l’SMS collegandosi semplicemente ad un sito internet. Da questa breve descrizione si evince come l’architettura con la quale è stato
progettato il sistema di geolocalizzazione riduca drasticamente i costi di gestione in quanto è sufficiente inviare un solo SMS per
poter localizzare la posizione di un utente. Va sottolineato che tra gli obbiettivi che ci si è posti durante la realizzazione del sistema
integrato non è presente sicuramente un elevata accuratezza posizionale. Infatti questo sistema è orientato ad un utilizzazione in real
time, da parte di un numero elevato utenti, quindi una accuratezza posizionale 10 m è stata giudicata più che sufficiente
Dal rilievo dei dati territoriali al webgis basato su geodatabase open source. L'esperienza del comune di San Giuseppe Vesuviano
No full textSimulazione di un test di integrità mediante tecnologia RAIM
No full textIntegrity relates to the trust that can be placed in the correctness of information supplied
by a navigation system. Receiver Autonomous Integrity Monitoring (RAIM) refers to Integrity
monitoring of GNSS navigation signals performed by a receiver independent of external reference
system, except for the navigation signals themselves. In this paper the mathematical models for
RAIM and its measure of reliability and are described. Detailed simulations have been carried to
evaluate the reliability and of two different types of RAIM algorithms
Galileo Signal Design: State of Art
No full textThe Global Positioning System (G.P.S.) has been a revolutionary system that opened new opportunities and enabled innovative services for both governmental and civilian applications. Rapidly, an efficient and reliable positioning system has become mandatory for public protection and security applications. As consequence Europe has realized the need to develop an independent positioning system (Galileo) with enhanced capabilities, performance and an unconditioned reliability. Galileo has pursued from the very first moment the goal of having wide band signals in all its assigned frequency bands but it was a particularly difficult task because the band E1 and L1 had already congested. It will be at the same time compatible and inter operable with American G.P.S. Compatibility refers to the ability of space based positioning, navigation and timing (P.N.T.) services to be used separately or together without interfering with each individual service or signal, and without adversely affecting navigation warfare. Interoperability refers to the ability of civil space base P.N.T. services to be used together to provide better capabilities at the user level than would be achieved by relying solely on one service or signal. To achieve this it was necessary planning special signal with particular waveform. An important aspect in designing the modulation scheme is obtain good spectral properties and suitable spectral shaping, low interference with existing G.P.S. signals, good root mean square (R.M.S.) bandwidth, good time resolution (in order to allow the separation between channel paths and to decrease the synchronization errors). The family of modulations that allowed this was the B.O.C. (Binary Offset Carrier). This paper is concerned with this modulation: it will be described their performance both the transmitter that the receiver point of view. Moreover after a brief description of Galileo signal in which will highlight the differences between the various services to be provided by Galileo itself, will be introduced the AltBOC modulation used on E5. Attention will focused on the signal processing techniques required to process the AltBOC modulation because they are much more challenging than those for traditional BPSK or even for the usual B.O.C. modulation. This stems from the extremely large bandwidth and from the complex interaction of 4 components of spreading code
A new method for specular and diffuse pseudorange multipath error extraction using wavelet analysis
No full textMultipath remains one of the major challenges in Global Navigation Satellite System (GNSS) positioning because it is considered the dominant source of ranging errors, which can be classified into specular and diffuse types. We present a new method using wavelets to extract the pseudorange multipath in the time domain and breaking it down into the two components. The main idea is an analysis-reconstruction approach based on application of both continuous wavelet transform (CWT) and discrete wavelet transform (DWT). The proposed procedure involves the use of L1 code-minus-carrier (CMC) observable where higher-frequency terms are isolated as residuals. CMC residuals are analyzed by applying the CWT, and we propose the scalogram as a technique for discerning time–frequency variations of the multipath signal. Unlike Fourier transform, the potential of the CWT scalogram for examining the non-stationary and multifrequency nature of the multipath is confirmed as it simultaneously allows fine detection and time localization of the most representative frequencies of the signal. This interpretation of the CWT scalogram is relevant when choosing the levels of reconstruction with DWT, allowing accurate time domain extraction of both the specular and diffuse multipath. The performance and robustness of the method and its boundary applicability are assessed. The experiment was carried out using a receiver of Campania GNSS Network. The results are given in which specular multipath error is achieved using DWT level 7 approximation component and diffuse multipath error is achieved using DWT level 6 denoised detail component
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