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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Precise orbit determination of global navigation satellite system of second generation (GNSS-2) orbit determination of IGSO, GEO and MEO satellites /

Su, Hua. January 2000 (has links)
München, Univ. der Bundeswehr, Diss., 2000. / Computerdatei im Fernzugriff.
2

Precise orbit determination of global navigation satellite system of second generation (GNSS-2) orbit determination of IGSO, GEO and MEO satellites /

Su, Hua. January 2000 (has links)
München, Univ. der Bundeswehr, Diss., 2000. / Computerdatei im Fernzugriff.
3

Precise orbit determination of global navigation satellite system of second generation (GNSS-2) orbit determination of IGSO, GEO and MEO satellites /

Su, Hua. January 2000 (has links) (PDF)
München, University der Bundeswehr, Diss., 2000.
4

Capteurs MEMS : optimisation des méthodes de traitement capteurs, de navigation et d'hybridation / MEMS sensors : preprocessing and GNSS/MEMS navigation optimization

Boer, Jean-Rémi de 12 January 2010 (has links)
Les travaux menés durant cette thèse ont pour objectif d’améliorer les performances des systèmes hybrides GNSS/MEMS. Ils se décomposent en deux parties distinctes : d’une part, le développement d’un ensemble de traitement capteurs cherchant à améliorer la mesure elle-même et d’autre part, l’optimisation des algorithmes d’hybridation pour les capteurs MEMS de Thales. Le traitement capteur consiste en l’estimation de l’accélération vraie (resp. la vitesse angulaire vraie) à partir de la sortie du capteur accélérométrique (resp. gyrométrique). Ce traitement a été réalisé en deux sous-étapes : 1) La calibration qui consiste en l’identification du système non-linéaire connaissant ses entrées et ses sorties. Les relations entrant en jeu dans le modèle étant linéaires vis-à-vis des paramètres, on peut alors résoudre cette partie du problème par l’estimateur des moindres carrés (après extension du vecteur comprenant les entrées afin qu’il comporte les non linéarités). 2) L’inversion du modèle qui a pour but d’estimer les entrées du modèle connaissant ses sorties et l’estimation des paramètres effectuée durant l’étape de calibration. Après formalisation de ce problème sous forme d’un modèle dynamique, la résolution se fera à l’aide d’algorithme type filtre de Kalman ou filtre particulaire. Les algorithmes d’hybridation ont pour but de localiser un mobile dans l’espace connaissant l’information issue des MEMS ainsi que celle apportée par le GPS. Cette partie peut également se décomposer en deux sous-problèmes : 1) Lorsque que les signaux GPS sont disponibles (cas nominal), le but est d’améliorer les méthodes de navigation hybride GPS/INS existantes (EKF, UKF, PF, …). Dans notre cas, la réflexion a portée sur une modélisation à l’ordre 2 des biais des capteurs MEMS et sur la fermeture de la boucle de navigation (correction de la centrale inertielle à l’aide des erreurs issues du filtre d’hybridation). 2) Dans des scénarii défavorables (multitrajet et masquage des signaux GPS), la qualité des capteurs MEMS ne permet pas d’obtenir des résultats de navigation satisfaisants. Un algorithme basé sur un réseau de neurones a donc été développé. Durant les phases où le GPS est disponible, cet algorithme permet d’apprendre l’erreur commise par la centrale inertielle en mode survie par rapport au résultat de navigation hybride. Le réseau de neurones ainsi appris fournira alors cet élément de correction en cas de perte de l’information GPS. Ces différentes méthodes ont permis d’accroître la précision de la navigation GNSS/MEMS aussi bien dans le cas nominal que lors de pertes du signal GPS / The goal of this thesis is to improve accuracy of GNSS/MEMS integrated navigation system. Two main parts can be distinguished in this thesis: first, sensor processing can be achieved to improve measurement accuracy and then, navigation algorithm can be optimized for the specific case of MEMS sensors. Sensor processing is the estimation of real acceleration (resp. real angular rate) from the one measured by accelerometer (resp. gyrometer). This processing have been realized in two steps: 1) Calibration: identification of the non-linear system describing sensors (resolved by Least Square method). 2) Model inversion: estimation of the input of the non-linear system, i.e. acceleration and/or angular rate (resolved by Kalman filtering). Navigation algorithm have then to locate an object in space from both GNSS and MEMS data. This part have been also realized in two steps: 1) If GNSS signals are available, the goal is to improve the existing GNSS/INS navigation schemes (2nd-order bias modeling of MEMS sensors). 2) If GNSS are not available (e.g. multipath or outage), a Neural Network based algorithm have been developped, which learn the error made by the inertial platform during the unavailability of GNSS signals. These different methods have allowed to improve accuracy of GNSS/MEMS inetgrated navigation system both for nominal case and degraded case
5

Inmätning av dold punkt : En jämförelse mellan mätmetoderna RUFRIS, dubbla avstånd och ortogonal inmätning / Measuring of hidden points : A comparison of the measure methods RUFRIS, Two distances and Backwards bearing and distance

Svedåker, Stina, Boström, Therese January 2015 (has links)
Det blir alltmer vanligt att utföra olika typer av geodetiska inmätningar med hjälp av GNSS och grundentill den här studien är att undersöka olika mätmetoder som kan tillämpas på punkter där fixlösning integår att erhålla. Syftet blev således att ta fram ett resultat som visar om och i så fall hur stor skillnad detär mellan tre olika metoder samt vilken noggrannhet respektive metod uppvisar. De två metoderna somtestats i studien är ortogonal inmätning och inmätning med dubbla avstånd. För dessa två metoder krävsutöver den vanliga utrustningen vid inmätning med GNSS endast några stakkäppar och ett mätband. Dentredje metoden är inmätning med totalstation som etablerats med RUFRIS (realtidsuppdaterad fristation)och den baseras på tidigare gjorda undersökningar och jämförs i studien med ortogonal inmätning ochinmätning med dubbla avstånd. Vidare undersöks åtgången av tid och material i jämförelse mednoggrannheten hos respektive mätmetod. Metoderna ortogonal inmätning och inmätning med dubbla avstånd testades 24 gånger vardera genommätning mot sedan tidigare kända punkter med koordinater i SWEREF 99 13 30. Efter att resultatenanalyserats drogs slutsatsen att det i den här studien inte går att skilja dessa två metoder åtkvalitetsmässigt. De uppvisade en medelavvikelse på 32 respektive 33 mm. Den metod som kan vara attföredra sett till material och tidsåtgång är inmätning med dubbla avstånd vilken också är något merflexibel. Jämfört med RUFRIS så erbjuder de andra två metoderna inte lika hög noggrannhet, men ändå tillräckligdär inmätning sker med GNSS. Vid samma antal bakobjekt, vilket är två, går det att anta att en punktkan mätas in via RUFRIS med en noggrannhet på mellan 55,1 och 12,6 mm beroende på geometrin förbakobjekten. Genom ökat antal bakobjekt minskar också osäkerheten i mätningarna vilket gör attRUFRIS ger fler valmöjligheter. Att mäta in den här typen av punkter med RUFRIS ger alltså en bättrenoggrannhet och kontrollerbarhet. Men att använda metoden i dessa situationer kan betraktas somomotiverad då den kräver mer arbete, plats och utrustning samtidigt som de andra två metoderna ger entillräcklig noggrannhet. / GNSS-surveying is common today and it’s interesting to investigate methods that can be applied whenthe ambiguities cannot be fixed to the correct integer on a point that are involved. Three methods arecompared and two of them tested, which are Two distances and backwards bearing and distance. N-RTK(Network- Real Time Kinematic) is used and both methods are measured 24 times each on four knownpoints with coordinates in SWEREF 99 13 30. RUFRIS (Real Time Updated Free Station) is the thirdmethod and earlier studies are the background behind the comparison for this method. The consumptionof time, material and quality are included parts of the comparison. RUFRIS can provide high precision results, but takes more time to establish, more equipment andrequires free sights. An establishment with two back sights can give a precision between 55.1 and 12.6mm depending on the proliferation between the back sights. The result for two distance and backwardsbearing and distance were found equivalent to each other. The mean deviation was 32 and 33 mm.Because of time, material and more flexibility is the method Two distances to prefer.
6

GNSS Aided Inertial Human Body Motion Capture

Alsén, Victoria January 2016 (has links)
Human body motion capture systems based on inertial sensors (gyroscopes andaccelerometers) are able to track the relative motions in the body precisely, oftenwith the aid of supplementary sensors. The sensor measurements are combinedthrough a sensor fusion algorithm to create estimates of, among other parame-ters, position, velocity and orientation for each body segment. As this algorithmrequires integration of noisy measurements, some drift, especially in the positionestimate, is expected. Taking advantage of the knowledge about the tracked sub-ject, a human body, models have been developed that improve the estimates, butposition still displays drift over time.In this thesis, a GNSS receiver is added to the motion capture system to givea drift-free measurement of the position as well as a velocity measurement. Theinertial data and the GNSS data complements each other well, particularly interms of observability of global and relative motions. To enable the models of thehuman body at an early stage of the fusion of sensor data, an optimization basedmaximum a posteriori algorithm was used, which is also better suited for thenonlinear system tracked compared to the conventional method of using Kalmanfilters.One of the models that improves the position estimate greatly, without addingadditional sensing, is the contact detection, with which the velocity of a segmentis set to zero whenever it is considered stationary in comparison to the surround-ing environment, e.g. when a foot touches the ground. This thesis looks at botha scenario when this contact detection can be applied and a scenario where itcannot be applied, to see what possibilities an addition of GNSS sensor couldbring to the human body motion tracking case. The results display a notable im-provement in position, both with and without contact detection. Furthermore,the heading estimate is improved at a full-body scale and the solution makes theestimates depend less on acceleration bias estimation.These results show great potential for more accurate estimates outdoors andcould prove valuable for enabling motion tracking of scenarios where the contactdetection model cannot be used, such as e.g. biking.
7

Maskinstyrning : Maskinstyrning och dess användning ur ett geodetiskt perspektiv / Machine control : Machine control and its use from a geodetic perspective

Carlsson, Caroline, Tidholm, Matilda January 2013 (has links)
No description available.
8

Bestämning av vattenytor med hjälp av Nätverks-RTK och totalstation : Inmätning av Karlbergsån i Grums kommun / Determination of Water Surfaces using Network-RTK and Total Station : Surveying of the stream Karlbergsån in Grums Municipality

Hérou, Mathias, Boll, Ragnar January 2010 (has links)
This report is presenting an approach that can be used to measure water surfaces in difficult conditions caused by dense vegetation and lack of nearby known points. The objective was to make a contribution to necessary measures for adaptation against floods in Grums Municipality along the stream Karlbergsån, which may occur when persistent rain raises the level of the stream. Along the river there are low-lying areas prone to flooding. According to Grums Municipality, the stream may widen where the water level differences are large, to create a better flow path and to counteract flooding. Grums Municipality was also interested in survey stormwater discharges which may affect the water level in the stream. The requirement for measurement accuracy must be reached is less than 0.1 m in height with the maximum of 10 m between the measured points in plane. The question we asked ourselves was: "How can an area be measured when there is a lack of nearby known fixpoints and when the visibility to satellites is poor due to dense vegetation?" To be able to measure the area, we established a net of temporary fixpoints with NRTK , which later was used for the measuring of water surfaces and stormwater discharges by using total station. For measuring, both prism and reflectorless measurement have been used. Coordinates for the net of temporary fixpoints, input water levels and storm water discharges are presented and the report files and coordinates for station establishment. Graphic elevation profiles of water levels are registered. Visualization was created by using aerial photographs and measured data showing the entire surveyed area, including free station establishment with directions to the reference points together with the measured fixpoints and stormwater discharges. We believe we have come below the accuracy requirement of 0.1 m and sought a distance between points at less than 10 m but in some places where the measurements were limited the distance is greater than 10 m.
9

Secure navigation and timing without local storage of secret keys

Wesson, Kyle D. 27 June 2014 (has links)
Civil Global Navigation Satellite System (GNSS) signals are broadcast unencrypted worldwide according to an open-access standard. The virtues of open-access and global availability have made GNSS a huge success. Yet the transparency and predictability of these signals renders them easy to counterfeit, or spoof. During a spoofing attack, a malefactor broadcasts counterfeit GNSS signals that deceive a victim receiver into reporting the spoofer-controlled position or time. Given the extensive integration of civil GNSS into critical national infrastructure and safety-of-life applications, a successful spoofing attack could have serious and significant consequences. Unlike civil GNSS signals, military GNSS signals employ symmetric-key encryption, which serves as a defense against spoofing attacks and as a barrier to unauthorized access. Despite the effectiveness of the symmetric-key approach, it has significant drawbacks and is impractical for civil applications. First, symmetric-key encryption requires tamper-resistant receivers to protect the secret keys from unauthorized discovery and dissemination. Manufacturing a tamper-resistant receiver increases cost and limits manufacturing to trusted foundries. Second, key management is problematic and burdensome despite the recent introduction of over-the-air keying. Third, even symmetric-key encryption remains somewhat vulnerable to specialized spoofing attacks. I propose an entirely new approach to navigation and timing security that avoids the shortcomings of the symmetric-key approach while maintaining a high resistance to spoofing. My first contribution is a probabilistic framework that develops necessary components of signal authentication. Based on the framework, I develop an asymmetric-key cryptographic signal authentication technique and a non-cryptographic spoofing detection technique, both of which operate without a secret key stored locally in a secure receiver. These anti-spoofing techniques constitute the remaining two contributions of this dissertation. They stand as viable spoofing defenses for civil users and could augment---or even replace---current and planned military anti-spoofing measures. Finally, I offer an in-depth case study of the security vulnerabilities and possible cryptographic enhancements of a modern GNSS-based aviation surveillance technology in the context of the technical and regulatory aviation environment. / text
10

THE USE OF CONDUCTIVE INK IN ANTENNA EDUCATION AND DESIGN

Addison, David William 01 May 2017 (has links)
Conductive ink from a printer allows for the fabrication of conductive material with tight tolerances without the cost and time of chemical etching. This paper explores the use of AGIC printable conductive ink on a paper substrate as design tool for antennas as well as classroom use in antenna education. The antenna designs satisfy the requirements of a compact Global Navigation Satellite System (GNSS) antenna while showing a competitive performance within the current market. One best design is shown along with three other structures. These antennas consist of a bowtie cross-dipole over a reflective disc with conductive-ink grounded structures. In addition to the GNSS antennas, a linear elliptical dipole over a reflective disc with conductive grounded structures is presented. This elliptical antenna design attempts to find the maximum impedance bandwidth beyond the GNSS band. The inexpensive nature of conductive ink allows for its use in a classroom to demonstrate antenna behavior as part of antenna education. An inexpensive approach to the patch antenna using conductive ink is described and paired with a system made of off-the-shelf parts. The system is capable of measuring the power of the received signal. The received signal measurement is not as accurate as using a anechoic chamber but pattern details are visible. This is used to demonstrate aspects of the Friis transmission equation such as distance, polarization, radiation pattern shape, and loss.

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