Simulating GNSS Position Accuracy using Non-line of Sight Reflected Signals
23 Apr 2013-
TL;DR: In this paper, the authors describe the development and use of a simulation tool, called QualiSIM, to simulate GNSS-based position accuracy under various operational and environmental conditions, in particular in environments with large amounts of signal reflections.
Abstract: This paper describes the development and use of a simulation tool, called QualiSIM. This tool simulates GNSS-based position accuracy under various operational and environmental conditions, in particular in environments with large amounts of signal reflections. The signal reflections are implemented using the geometric path length the signal travels when it gets reflected from the surrounding buildings. Environmental influences on GNSS-based positioning are obstacles, such as buildings along streets which can lead to blocking and reflection of satellite signals. Examples of operational conditions are atmospheric effects and changes in the satellite geometry. The tool has been developed to work either with Galileo or GPS or with both satellite constellations. Since Galileo is only preoperational, the simulator is based on the nominal 27 satellite Galileo constellation. Further, the simulator uses: atmospheric models to simulate the effect on satellite signals through Earth?s atmosphere, designs of representative environments e.g. urban and rural scenarios, and a method to simulate reflection of satellite signals within the close environment of the GNSS (Global Navigation Satellite System) antenna. The simulator thus models: the signal path from satellite to receiver, satellite availability, the extended pseudoranges caused by signal reflection, and the position accuracy based on a least squares adjustment of the extended pseudoranges. In order to handle temporal and spatial variations of the different errors sources in GNSSbased positioning, the simulator has been developed for observing variations in position accuracy over time, along a given test trajectory, at different latitudes, and with different azimuths of the environment around the receiver. The environments used by the simulator could be typical representative scenarios such as, a narrow city street, a t-cross or mountain landscape. The choice of not using specific streets or cities has been made in order to keep the simulator open for every kind of environment. In this paper a simulation example is illustrated and shows the possibilities for visualisation of a narrow street with buildings on each side over a simulation time period of 24 hours. The impact of using reflected satellites in the position domain is significant. The DOP values are in general lower, but the error ellipses can be up to 8 times larger and furthermore deviate in shape.
Citations
More filters
Dissertation•
24 Nov 2017
TL;DR: In this paper, the authors propose a method to estimate dynamique des retards de propagation, which can be used to reduce the imprecision of the estimation of the position.
Abstract: Les applications des systemes de positionnement par satellites (ou GNSS - Global Navigation Satellite System) ont progressivement envahi les systemes de transport et les applications mobiles. Les applications deployees sont peu exigeantes en termes de performance : elles tolerent une certaine imprecision et ne requierent pas necessairement une grande confiance dans l'information delivree. Avec l'arrivee des vehicules autonomes ou les evolutions des systemes de signalisation ferroviaire, de nouveaux besoins sont exprimes : une plus grande precision assortie d'un indicateur de confiance dans l'information fournie, en particulier pour des applications qui mettent en jeu la securite des biens et des personnes. Un recepteur GNSS utilise la mesure simultanee de 4 (au moins) temps de propagation des signaux issus de 4 satellites differents pour estimer sa position. Dans les environnements traverses par les systemes de transports, la reception de ces signaux est frequemment sujette a des conditions de reception difficiles liees a la presence d'obstacles proches de l'antenne de reception (blocage, reflexion, diffraction) qui engendrent indisponibilite, retards de propagation et donc, erreurs sur le calcul de la position. Pour comprendre les causes et les consequences des erreurs introduites par le canal de propagation radio sur les performances de localisation, les travaux presentes dans ce memoire de HDR rassemblent les travaux menes selon 3 axes principaux. Dans ces travaux, nous avons ainsi analyse les effets du canal de propagation radio sur le signal recu par l'antenne du recepteur GNSS, caracterise et quantifie la qualite du signal recu en sortie du recepteur, propose des methodes originales permettant de modeliser et pallier les erreurs de localisation et enfin nous avons contribue au developpement d'une methodologie d'analyse de la surete de fonctionnement du systeme de localisation dans le domaine ferroviaire. L'erreur que nous cherchons a reduire en particulier est l'erreur engendree par les phenomenes de propagation locaux et en particulier par l'utilisation des signaux recus apres reflexions et en l'absence de signal direct, encore appeles NLOS (Non-Line-Of-Sight). Parmi les resultats, nous avons mis en oeuvre des techniques de traitement d'images pour une detection deterministe associee a des techniques d'exclusion et de ponderation des signaux recus. Avec des techniques de traitement du signal, nous avons propose des methodes d'estimation dynamique des retards de propagation qui ont montre leur efficacite dans la reduction des imprecisions sur les calculs de la position en milieux urbains. Enfin, nous abordons le concept d'integrite de la position. Les processus de surveillance de l'integrite sont aujourd'hui issus de l'aeronautique et s'adaptent mal aux conditions de reception en milieu urbain. Notre connaissance des conditions de propagation des signaux nous a conduits a etudier et a proposer de nouveaux processus pour borner les erreurs de position introduites par l'environnement urbain. Enfin, nous presentons les axes de recherche mis en oeuvre afin de contribuer a l'introduction des solutions GNSS pour des applications de signalisation ferroviaire : nos travaux portent sur l'adaptation des methodologies classiques ferroviaires au systeme GNSS et a ses sources de degradation.
13 citations
22 Nov 2013
TL;DR: In this article, a formale Axiomatisierung des Begriffs Messqualitat durchgefuhrt is presented, e.g., in the form of a Prufung.
Abstract: Zukunftige Anwendungen fur die satellitenbasierte Ortung im Verkehr werden immer hohere Anforderungen an die Messqualitat der Fahrzeugposition stellen. Wichtigstes Anwendungsbeispiel hierfur ist das automatisierte Fahren im Strasenverkehr. Hierzu muss die hinreichende metrologische Qualitat der Positionswerte nach einem systematischen und allgemein akzeptierten Verfahren nachgewiesen werden. Erst eine solche Prufung schafft die Rechtssicherheit fur den Einsatz von Ortungssystemen bei sicherheitsrelevanten und okonomisch bedeutsamen Anwendungen.
In dieser Arbeit wird eine formale Axiomatisierung des Begriffs Messqualitat durchgefuhrt. Darauf aufbauend werden Qualitatsmase zur Quantifizierung der Messqualitat definiert. Im Zuge dessen wird das international akzeptierte GUM-Verfahren zur Quantifizierung der Eigenschaft Messunsicherheit auf Zustandsraummodelle erweitert, um so auch zeitvariante Messgrosen, gemessen mit dynamischen Messsystemen, berucksichtigen zu konnen.
Fur die Validierung des Messqualitatsmodells und seiner Qualitatsmase werden allgemeingultige Anforderungen an Referenzsysteme fur die Fahrzeugortung spezifiziert. Anschliesend wird ein ortsgebundenes, satellitenunabhangiges Referenzsystem vorgestellt, das als Masstab fur das ebenfalls in dieser Arbeit entwickelte mobile Referenzsystem dient. Die Erprobung des exemplarisch implementierten mobilen Referenzsystems zeigt, dass die Generierung einer Referenzposition in hinreichender Qualitat moglich ist.
Es wird deutlich, dass sich das universelle Verstandnis des Begriffs Messqualitat in jeder Beurteilung von Werten zeitvarianter Messgrosen widerspiegelt. Sowohl das ortsfeste Referenzsystem, die mobile Referenz als auch satellitenbasierte Ortungssysteme lassen sich hinsichtlich ihrer Messqualitat stets nach demselben Schema beurteilen. Die vorgestellte Axiomatisierung der Messqualitat ermoglicht somit einen standardisierten Vergleich von Fahrzeugortungssystemen.
7 citations
Cites background from "Simulating GNSS Position Accuracy u..."
...Den Weg hierhin zeigen der vorgestellte exemplarische Parameterraum sowie dessen programmtechnische Realisierung in Form eines Szenariensimulators, wie er in [65] beschrieben ist....
[...]
...Zur Spezifizierung von Prüfszenarien wurden für den in [65] vorgestellten Szenariensimulator generische Szenarienparameter sowie realitätsnahe Wertebereiche identifiziert....
[...]
References
More filters
Book•
01 Dec 2010TL;DR: This advanced tutorial will describe the GPS signals, the various measurements made by the GPS receivers, and estimate the achievable accuracies, and focus on topics which are more unique to radio navigation or GPS.
Abstract: The Global Positioning System (GPS) is a satellite-based navigation and time transfer system developed by the U.S. Department of Defense. It serves marine, airborne, and terrestrial users, both military and civilian. Specifically, GPS includes the Standard Positioning Service (SPS) which provides civilian users with 100 meter accuracy, and it serves military users with the Precise Positioning Service (PPS) which provides 20-m accuracy. Both of these services are available worldwide with no requirement for a local reference station. In contrast, differential operation of GPS provides 2- to 10-m accuracy to users within 1000 km of a fixed GPS reference receiver. Finally, carrier phase comparisons can be used to provide centimeter accuracy to users within 10 km and potentially within 100 km of a reference receiver. This advanced tutorial will describe the GPS signals, the various measurements made by the GPS receivers, and estimate the achievable accuracies. It will not dwell on those aspects of GPS which are well known to those skilled in the radio communications art, such as spread-spectrum or code division multiple access. Rather, it will focus on topics which are more unique to radio navigation or GPS. These include code-carrier divergence, codeless tracking, carrier aiding, and narrow correlator spacing.
2,203 citations
"Simulating GNSS Position Accuracy u..." refers background in this paper
...GPS is fully operational since 1995 [2]....
[...]
...For a description of the various coordinate systems see [2]....
[...]
Book•
01 Jan 1966
TL;DR: The theory of satellite geodesy writer by Why as discussed by the authors is a best seller book on the planet with excellent value and content is integrated with fascinating words and can be read online or download this book by right here.
Abstract: Have leisure times? Read theory of satellite geodesy writer by Why? A best seller book on the planet with excellent value and content is integrated with fascinating words. Where? Just below, in this website you could check out online. Want download? Obviously available, download them also here. Offered documents are as word, ppt, txt, kindle, pdf, rar, and zip. Whatever our proffesion, theory of satellite geodesy can be excellent resource for reading. Locate the existing documents of word, txt, kindle, ppt, zip, pdf, and rar in this site. You could absolutely read online or download this book by right here. Currently, never miss it. Our goal is always to offer you an assortment of cost-free ebooks too as aid resolve your troubles. We have got a considerable collection of totally free of expense Book for people from every single stroll of life. We have got tried our finest to gather a sizable library of preferred cost-free as well as paid files. GO TO THE TECHNICAL WRITING FOR AN EXPANDED TYPE OF THIS THEORY OF SATELLITE GEODESY, ALONG WITH A CORRECTLY FORMATTED VERSION OF THE INSTANCE MANUAL PAGE ABOVE.
1,355 citations
TL;DR: In this paper, a model for the height profile of tropospheric refractivity N and expressions derived from it for computing corrections for satellite Doppler or range data were presented.
Abstract: This paper presents a new model for the height profile of tropospheric refractivity N and expressions derived from it for computing corrections for satellite Doppler or range data. (N ≡ 106 (n - 1), where n is the index of refraction.) The model is theoretically based on an atmosphere with constant lapse rate of temperature, as will be shown. It treats the ‘dry’ and ‘wet’ components of N separately and represents each as a fourth-degree function of height above the geoid; each component profile starts with its locally observed surface value and decreases to zero at an effective height that is different for the two components. The height parameters were obtained by a least-squares fit to observed data. A latitude dependence has been found for the ‘dry’ height. The model has been found capable of closely matching any local average N profile observed in a world-wide sample of locations throughout the height range of meteorological balloon data (up to 24 km); samples are shown. The corrections based on it are readily evaluated and are finite and usable at all elevation angles. Their effectiveness is evidenced by figures showing two different kinds of observed data: first, Doppler residuals for several satellite passes without and with the use of the correction; and the ‘navigation’ error in station-to-orbit slant range from Doppler data, again without and with the correction. The use of the correction removed obvious systematic errors. The fact that satellite Doppler data display identifiable tropospheric effects is of interest with regard to future study of the troposphere.
524 citations
"Simulating GNSS Position Accuracy u..." refers methods in this paper
...In QualiSIM, the effect of the troposphere is modelled using the Hopfield troposphere model [4]....
[...]
01 Jan 2007
TL;DR: This note primarily describes the mathematics of least squares regression analysis as it is often used in geodesy including land surveying and satellite based positioning applications.
Abstract: This note primarily describes the mathematics of least squares regression analysis as it is often used in geodesy including land surveying and satellite based positioning applications. In these fields regression is often termed adjustment1. The note also contains a couple of typical land surveying and satellite positioning application examples. In these application areas we are typically interested in the parameters of the model (often 2or 3-D positions) and their uncertainties and not in predictive modelling which is often the main concern in other regression analysis applications.
23 citations
"Simulating GNSS Position Accuracy u..." refers methods in this paper
...The least squares adjustment is implemented in QualiSIM as described in detail in [5]....
[...]