Globale Navigationssatellitensysteme (global navigation satellite systems, GNSS) ermöglichen die Positionsbestimmung, Navigation und Zeitübertragung überall auf der Erde und zu jeder Zeit. Dabei können durch spezielle Auswerteverfahren und die Berücksichtigung von Messabweichungen, denen die Beobachtungen der Satelliten unterliegen, deutlich höhere Genauigkeiten erreicht werden als ursprünglich vorgesehen. Ursachen für Messabweichungen sind neben Phänomenen, die den Signalweg beeinflussen, auch elektronische und elektromagnetische Effekte an den Satelliten und Empfangssystemen. Richtungsabhängige Verzögerungen der Codebeobachtungen (group delay variations, GDV) stellen eine solche Art der Messabweichung dar. Sie entstehen durch richtungsabhängige Sende- und Empfangseigenschaften der Satelliten- bzw. Empfangsantennen und sind frequenzabhängig. Aufgrund steigender Genauigkeitsanforderungen hat sich die Bestimmung und Korrektion von Messabweichungen zu einem wichtigen Forschungsfeld etabliert. Hier leistet die vorliegende Arbeit einen Beitrag. Sie beschäftigt sich mit der Bestimmung von GDV auf der Grundlage von Beobachtungen terrestrischer Referenzstationen, wobei die GDV der GNSS-Satellitenantennen im Vordergrund stehen. Da eine Codebeobachtung sowohl die GDV der Satellitenantenne als auch die der Empfangsantenne enthält, stellt die exakte Trennung beider Anteile eine besondere Herausforderung dar. Sie kann nur gelingen, wenn für eine der Antennen absolute Werte bekannt sind. Absolute GDV von Satelliten- und Empfangsantennen haben den Vorteil, dass sie unabhängig voneinander nutzbar sind. Im Gegensatz dazu beziehen sich relative Satellitenantennen-GDV auf die verwendeten Empfangsantennen und sind nicht unabhängig von ihnen. Die kumulative Dissertation basiert auf drei wissenschaftlichen Publikationen zur Bestimmung relativer und absoluter GDV. Am Beispiel relativer GDV der GPS-Satellitenantennen wird zunächst deren zeitliche Stabilität untersucht. Die Ergebnisse zeigen, dass von zeitlicher Stabilität über die Dauer von mindestens zwei Jahren ausgegangen werden kann. Daraufhin erfolgt mit Beobachtungen jeweils nur einer Orbitperiode die Bestimmung relativer GDV für die Satellitenantennen von GLONASS und Galileo. Es stellt sich heraus, dass Orbitperioden von mehreren Tagen die Datenakquise deutlich erleichtern. Zudem ermöglichen die Kriterien hinsichtlich des Equipments der ausgewählten Referenzstationen typspezifische Betrachtungen der Empfangsantennen. Schließlich können auf der Grundlage absoluter GDV-Korrektionen für GNSS-Empfangsantennen auch absolute GDV für die Satellitenantennen von GPS, GLONASS, Galileo, BeiDou und QZSS bestimmt werden. Mit diesem Ergebnis steht erstmals ein umfangreiches Set absoluter Multi-GNSS- und Multifrequenz-GDV für einen Großteil der GNSS-Satellitenantennen zur Verfügung. Es gewährt einen systemübergreifenden Überblick und kann zur Korrektion von Codebeobachtungen verwendet werden. Auch wenn sich die Genauigkeit der GDV-Schätzungen noch nicht abschließend beurteilen lässt, birgt die angewendete Methode das Potenzial, GDV mit einer Präzision von wenigen Zentimetern zu bestimmen.:Kurzfassung Abstract Inhaltsverzeichnis Abbildungsverzeichnis Tabellenverzeichnis Abkürzungsverzeichnis 1 Einleitung 1.1 Beschreibung richtungsabhängiger Codeverzögerungen 1.2 Stand der Forschung 1.3 Motivation 2 Bestimmung richtungsabhängiger Codeverzögerungen 2.1 Richtungen an Satelliten- und Empfangsantennen 2.2 Methoden 2.3 Code-Minus-Carrier-Methode 2.3.1 Code-Minus-Carrier-Linearkombination 2.3.2 Schätzung richtungsabhängiger Codeverzögerungen 2.3.3 Aspekte der untersuchten GNSS 2.4 Ergebnisse 3 Publikationen P1 Die zeitliche Stabilität der Code-Verzögerungen von GPS-Sendeantennen P2 Die Code-Verzögerungen von Galileo und GLONASS P3 Bestimmung absoluter Code-Verzögerungen für GNSS-Satellitenantennen auf der Grundlage absoluter Code-Verzögerungen von Empfangsantennen 4 Schlussfolgerungen und Ausblick Literaturverzeichnis Anhang / Global navigation satellite systems (GNSS) provide positioning, navigation, and timing services anywhere on Earth and at any time. Sophisticated processing methods and the consideration of measurement deviations make it possible to achieve much higher accuracies than originally intended. Measurement deviations originate, aside from phenomena affecting the signal path, from electronic and electromagnetic effects on the satellites and receiving systems. Direction-dependent delays of the code observations, so-called group delay variations (GDV), represent such a type of measurement deviations. They are caused by direction-dependent transmission and reception properties of the satellite and receiver antennas, respectively, and are frequency-dependent. Due to increasing accuracy requirements, the investigation and correction of GNSS measurement deviations has become an important field of research. This thesis makes a contribution to this field. It deals with the estimation of GDV based on GNSS observations of terrestrial reference stations, with a focus on the GDV occurring at the satellite antennas. Since GNSS code observations contain both the GDV of the satellite and that of the receiver antenna, the exact separation of both parts is a special challenge. It becomes possible only if absolute GDV are available for one of the antennas. Absolute GDV of satellite and receiver antennas have the advantage that they can be used independently of each other. On the contrary, relative satellite antenna GDV refer to the receiver antennas and are not independent from them. The cumulative dissertation is based on three scientific publications on the determination of relative and absolute GDV. First, the temporal stability of the satellite antenna GDV is investigated using the example of relative GDV for GPS satellite antennas. The results indicate that temporal stability can be assumed over a period of at least two years. Second, with observations of only one orbit period each, the determination of relative GDV for GLONASS and Galileo satellite antennas is carried out. It turns out that orbit periods of several days significantly facilitate data acquisition. In addition, the criteria regarding the equipment of the selected reference stations reveal type-specific properties of the receiver antennas. Finally, based on absolute GDV corrections for GNSS receiver antennas, absolute GDV can also be estimated for the satellite antennas of GPS, GLONASS, Galileo, BeiDou, and QZSS. With this result, a comprehensive set of absolute multi-GNSS and multi-frequency GDV is available for the majority of present GNSS satellite antennas for the first time. It provides a cross-system overview and can be used to correct code observations. Even if the accuracy of the GDV estimates cannot yet be conclusively assessed, the applied method has the potential to estimate GDV with a precision of a few centimeters.:Kurzfassung Abstract Inhaltsverzeichnis Abbildungsverzeichnis Tabellenverzeichnis Abkürzungsverzeichnis 1 Einleitung 1.1 Beschreibung richtungsabhängiger Codeverzögerungen 1.2 Stand der Forschung 1.3 Motivation 2 Bestimmung richtungsabhängiger Codeverzögerungen 2.1 Richtungen an Satelliten- und Empfangsantennen 2.2 Methoden 2.3 Code-Minus-Carrier-Methode 2.3.1 Code-Minus-Carrier-Linearkombination 2.3.2 Schätzung richtungsabhängiger Codeverzögerungen 2.3.3 Aspekte der untersuchten GNSS 2.4 Ergebnisse 3 Publikationen P1 Die zeitliche Stabilität der Code-Verzögerungen von GPS-Sendeantennen P2 Die Code-Verzögerungen von Galileo und GLONASS P3 Bestimmung absoluter Code-Verzögerungen für GNSS-Satellitenantennen auf der Grundlage absoluter Code-Verzögerungen von Empfangsantennen 4 Schlussfolgerungen und Ausblick Literaturverzeichnis Anhang

The purpose of this diploma thesis is testing motion of the device for GNSS antenna calibration according to added weight to the device’s transom. First part of this thesis is devoted to introduction into GNSS antenna calibration problematics. The thesis deals further with development of the software used to process photogrammetric images that have been taken during testing measurement. The rest of the thesis is focused to process and evaluate the measurement. The result will be implemented into observation model used during calibration measurement. The period, during the device is still, will be corrected according to the result that has been obtained from the measurement.

This thesis is concerned with determining the orientation of small Unmanned Aerial Vehicles(UAVs). To make commercial use of these aircraft in aerial surveying markets their attitude needs to be determined accurately and precisely throughout a survey flight. Traditionally inertial sensors have been used on larger aircraft to estimate both position and orientation in combination with Global Navigation Satellite Systems (GNSS). High quality inertial sensors have many downsides when used on the small UAV. They are expensive, power hungry and often heavy. Inertial sensors are vulnerable to vibration, high acceleration, high rotation rate and jerk. All of these are present on the small UAV. This thesis identifies GNSS attitude determination as a potentially suitable alternative to inertial techniques. Carrier phase GNSS attitude determination uses three or more GNSS receivers with antennas separated by a short baseline to estimate the orientation of the UAV. This technique offers low cost, high accuracy and drift-free attitude estimates. To be successfully used it requires removal of the biases present in the received GNSS signals and estimation of the integer cycle ambiguity present in the carrier phase measurement. This thesis presents and examines the state of the art techniques for removing these biases and estimating an integer cycle ambiguity using a priori measurement of the interantenna distance. In this work a novel method is developed which uses this a priori baseline measurement to validate estimates of the carrier phase ambiguities. In order to test these methods data has been gathered using low cost, commercially available GNSS receivers and antennas. This is the first work in which modern, low cost, GNSS equipment has been tested for use in attitude determination. It is found that the state of the art carrier phase GNSS attitude determination methods can provide an accurate attitude estimate for every set of measurements from the GNSS receivers. However, a real UAV flight indicates that the low cost GNSS equipment does not track the GNSS signals throughout the flight. Signal outages, cycle slips and half cycle ambiguous carrier phase measurements occur due to rapid UAV manoeuvres. Having identified this problem this work goes on to replicate and quantify it through the use of a GNSS hardware simulator. Algorithms are then devised to increase the availability of the GNSS attitude solution throughout the tracking difficulties. Complete GNSS signal tracking failures are overcome through the innovative use of kinematic and dynamic attitude models. Both types of model give an attitude solution throughout GNSS signal tracking problems without adding significant cost or weight to the system. When tracking of the GNSS carrier phase signal is possible, novel use of the carrier phase triple difference observable allows the attitude rate to be estimated even when the carrier phase measurements are half cycle ambiguous. It is shown that integer and half integer cycle slips can be removed from the measurement through the combination of the modelling and triple difference techniques. The attitude output of both modelling and triple difference methods is used to resolve half cycle ambiguities and make full use of half cycle ambiguous data where previously it could not have been used. Success rates of up to 99.6% have been achieved for half cycle ambiguity resolution. As a result precise and accurate GNSS attitude solutions are available at nearly every epoch for which a carrier phase measurement is output by the GNSS receivers. When no measurement is available the attitude solution gracefully degrades over time. This work makes reliable, accurate, low cost attitude determination possible on mini-UAVs.

A navigation filter simulation and analysis environment was developed through the integration of DRAGON, a high fidelity real-time PNT sensor measurement source, and Scorpion, a modular navigation filter implementation framework. The envi- ronment allows navigation filters to be prototyped and tested in varying complex scenarios with a configurable set of navigation sensors including GNSS and IMU. An analysis of an EKF using the environment showed the utility and functionality of the system.

A navigation filter simulation and analysis environment was developed through the integration of DRAGON, a high fidelity real-time PNT sensor measurement source, and Scorpion, a modular navigation filter implementation framework. The envi- ronment allows navigation filters to be prototyped and tested in varying complex scenarios with a configurable set of navigation sensors including GNSS and IMU. An analysis of an EKF using the environment showed the utility and functionality of the system.

Radio signals propagating through the ionised upper atmosphere (the ionosphere) in low latitude regions of the world can experience amplitude scintillation. This could threaten safety-critical applications of satellite navigation such as aviation. The research presented here studied the effects of amplitude scintillation on a Septentrio PolaRxS geodetic receiver and a Garmin 480 aviation receiver by means of a Spirent GNSS constellation simulator. Different types of fade profiles showed that an abrupt drop in signal strength caused a loss of lock on the signal more often than a profile with a slow, gradual fade. A performance comparison of the two receivers demonstrated that the aviation receiver was more vulnerable than the geodetic receiver. An unexpected loss of lock at a specific fade duration and depth was seen with the Garmin receiver and was not explained. A single fade with a long fade duration was more likely to cause a loss of signal lock compared to rapid multiple fades. Scintillation on signals from low elevation satellites can significantly degrade the precision and integrity of the navigation solution in an aviation receiver; especially if the satellites are within the best geometrical set. RAIM was observed to be no longer available during the critical landing approach phase of the scenario, in the case when all satellites in view were affected by the scintillation-induced signal perturbations. A technique was also developed to simulate L5 scintillation based on real scintillation events of L1, in the absence of real captured data for L5. This was done to enable future investigations on aviation receiver performance when both L1 and L5 frequencies experience scintillation. Analysis indicated that L5 signal can be more vulnerable to the scintillation compared to the L1 signal, which may have important implications for aviation safety.

A new, open-access Global Positioning System (GPS) signal, known as L1C, is the most recent of several modernized Global Positioning System (GPS) signals. The first launch of a GPS satellite with this signal is expected to occur within a few years. One of the interesting features of modern Global Navigation Satellite System (GNSS) signals, including GPS L1C, is the presence of data and pilot components. The pilot component is a carrier with a deterministic overlay code but no data symbols; whereas, the data component carries the navigation data symbols used in the receiver processing. A unique aspect of GPS L1C is the asymmetrical power split between the two components, 75% of the power is used for the pilot and the remaining power, or 25%, for the data. In addition, the pilot and the data components are transmitted in phase with orthogonal spreading codes. Unassisted acquisition of GNSS spread spectrum signals requires a two-dimensional search for the spreading code delay and Doppler frequency. For modern two-component GNSS signals, conventional GNSS acquisition schemes may be used on either component, correlating the received signal with either the pilot or the data spreading code. One obvious disadvantage of this approach is the wasting of power; hence, new techniques for combining, or joint acquisition of the pilot and the data components, have been proposed. In this dissertation, acquisition of GPS L1C is analyzed and receiver techniques are proposed for improving acquisition sensitivity. Optimal detectors for GPS L1C acquisition in additive white Gaussian noise are derived, based on various scenarios for a GPS receiver. Monte Carlo simulations are used to determine the performance of these optimal detectors, based on detection and false alarm probabilities. After investigating the optimal detectors for GPS L1C acquisition, various sub-optimal detectors that are more efficient to implement are thoroughly investigated and compared. Finally, schemes for joint acquisition of L1C and the legacy GPS C/A code signal are proposed and analyzed.

L’évolution des technologies électroniques (miniaturisation, diminution des coûts) a permis aux GNSS (systèmes de navigation par satellites) d’être de plus en plus accessibles et doncutilisés au quotidien, par exemple par le biais d’un smartphone, ou de récepteurs disponibles dans le commerce à des prix raisonnables (récepteurs bas-coûts). Ces récepteurs fournissent à l’utilisateur plusieurs informations, comme par exemple sa position et sa vitesse, ainsi que des mesures des temps de propagation entre le récepteur et les satellites visibles entre autres. Ces récepteurs sont donc devenus très répandus pour les utilisateurs souhaitant évaluer des techniques de positionnement sans développer tout le hardware nécessaire. Les signaux issus des satellites GNSS sont perturbés par de nombreuses sources d’erreurs entre le moment où ils sont traités par le récepteurs pour estimer la mesure correspondante. Il est donc nécessaire decompenser chacune des ces erreurs afin de fournir à l’utilisateur la meilleure position possible. Une des sources d’erreurs recevant beaucoup d’intérêt, est le phénomène de réflexion des différents signaux sur les éventuels obstacles de la scène dans laquelle se trouve l’utilisateur, appelé multitrajets. L’objectif de cette thèse est de proposer des algorithmes permettant de limiter l’effet des multitrajets sur les mesures GNSS. La première idée développée dans cette thèse est de supposer que ces signaux multitrajets donnent naissance à des biais additifs parcimonieux. Cette hypothèse de parcimonie permet d’estimer ces biais à l’aide de méthodes efficaces comme le problème LASSO. Plusieurs variantes ont été développés autour de cette hypothèse visant à contraindre le nombre de satellites ne souffrant pas de multitrajet comme non nul. La deuxième idée explorée dans cette thèse est une technique d’estimation des erreurs de mesure GNSS à partir d’une solution de référence, qui suppose que les erreurs dues aux multitrajets peuvent se modéliser à l’aide de mélanges de Gaussiennes ou de modèles de Markov cachés. Deux méthodes de positionnement adaptées à ces modèles sont étudiées pour la navigation GNSS.

This dissertation presents a novel satellite timekeeping system which does not require on-board atomic clocks as used by existing navigation satellite systems such as GPS, GLONASS or the planned GALILEO system. This concept is differentiated by the employment of a synchronization framework combined with lightweight steerable on-board clocks which act as transponders re-broadcasting the precise time remotely provided by the time synchronization network located on the ground. This allows the system to operate optimally when satellites are in direct contact with the ground station, making it suitable for a system like the Japanese Quasi-Zenith Satellite System, QZSS. Low satellite mass and low satellite manufacturing and launch cost are significant advantages of this novel system. Two possible implementations of the time synchronization network for QZSS are presented. Additionally, the problem of satellite communication interruption is analyzed and a solution is presented. Finally a positioning and timing quality analysis, aimed to provide understanding of the actual timing quality requirements for QZSS, is presented.

<p>När ett bygglov beviljas, d v s när en byggnad förändras, rivs alternativt nybyggs, kan det i sin tur innebära att kommunens kartmaterial inte längre stämmer överens med verkligheten. Syftet med detta examensarbete är därför att framställa en beskrivning för hur Gävle kommun arbetar med uppdateringen av sin kartdatabas. Det är när ett bygglov beviljas som Gävle kommun får vetskap om att en byggnad eventuellt kommer att förändras och därför kontrolleras de beviljade byggloven ute i fält en gång per år. Då kontrolleras om byggarbetet är påbörjat, klart eller inte alls påbörjat. Då en förändring av en byggnad har skett och beroende på vad det är för någonting som skall mätas in sker mätningsarbetet normalt på tre olika sätt, alternativt någon kombination av dessa. Då det endast är enklare tillbyggnationer på redan befintliga byggnader utförs mätningen med hjälp av ett digitalt längdmätningsinstrument. Vid nybyggnationer används ibland metoden inbindning vilket innebär att positionen för t ex ett byggnadshörn bestäms med hjälp av endast längder från två punkter med känd position. För att direkt bestämma positionen för en punkt används GNSS. Dessa punkter används sedan för att rita in byggnaden i ArcMap. För att mäta in en enklare byggnad med hjälp av GNSS räcker det i regel att mäta in ett hörn och en riktning på en vägg, övriga mått kan då mätas med längdmätningsinstrumentet för att sedan ritas in med det GNSS-inmätta hörnet som utgångspunkt. Jag har under mitt examensarbete märkt att den kunskap jag har med mig från skolan ger en riktigt bra grund att stå på och sedan bygga vidare på ute i arbetslivet. Vidare kan jag konstatera att jag under detta examensarbete har lärt mig enormt mycket. Jag har fått erfarenheter och kunskap om vad som krävs för att en kommun skall kunna tillhandahålla aktuell och pålitlig kartinformation.</p>