S. Schlüter

University of Leipzig , Leipzig, Saxony, Germany

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Publications (80)11.68 Total impact

  • ENC-GNSS 2010; 10/2010
  • David Minkwitz, Stefan Schlüter, Jamila Beckheinrich
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    ABSTRACT: The beacon system of the International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) has been the standard maritime GNSS (Global Navigation Satellite System) augmentation system for many maritime applications since the 90th. The stations provide differential corrections to GNSS receivers in order to improve navigation accuracy and monitor the quality of GNSS satellite transmissions. Depending on the rover-to-reference station separation and the age of the corrections being applied, the horizontal accuracy of the system is below 10 metres at more than 95% of the time. To ensure integrity, the integrity monitoring station (IM) of the IALA beacon system monitors the GNSS signals, verifies the availability of the reference station (RS) and immediately notifies users to disregard the signal or, in the worth case, to use another station. According to IALA Recommendation R-135 [3] there are potential alternatives to the IALA beacon system for the distribution of safety related differential services. One considered option designed to achieve position accuracies below one decimetre (e.g. for port and inland waterways) is carrier phase based GNSS positioning, so called Real Time Kinematic (RTK). As in Differential GNSS (DGNSS) the basic concept of a single base RTK system involves a reference station with a well known position, but instead of pseudorange corrections, raw measurements are transmitted to a rover receiver via a communication link (here we do not consider network RTK). The data processing at the rover site includes ambiguity resolution of the differenced carrier phase data and finally the estimation of the rover position. Single base RTK is also limited by the distance between reference receiver and the rover receiver due to the spatial decorrelation of distance-dependent biases such as orbit error, and ionospheric and tropospheric signal refraction. But one significant drawback of RTK, in comparison to the DGNSS approach, is that the maximum service area of the RTK reference station is restricted to 10 to 20 kilometres. Nevertheless for high precise port operations [4] and locking of ships, single base RTK can be an option, provided that also integrity is assured. The intention of the work presented here was, to study integrity aspects that would appear, if one enhances the DGNSS service of an IALA beacon system by an additional RTK service. The major concern has been to assess if shore based integrity monitoring stations, performing a number of tests on the GNSS signals, may be sufficient to assure the required integrity for high precise, safety critical maritime applications using RTK.
    ION GNSS 2010; 09/2010
  • Stefan Schlüter, Evelin Engler
    Baltic Future; 05/2010
  • David Minkwitz, Evelin Engler, Stefan Schlüter
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    ABSTRACT: Ground Based Augmentation Systems (GBAS) supporting phase-based DGNSS or pseudolite-augmented positioning are sufficient approaches to fulfil IMO requirements (International Maritime Organisation) on future GNSS for vessel navigation in port areas. With respect to the “safety of life” character of maritime traffic and transport processes, the GBAS must be enriched with a self-monitoring system assessing the augmentation service provided in real time in relation to specific user requirements. The build-up of the experimental GBAS in the vicinity of the Research Port Rostock and the development of monitoring algorithm were realised in the frame of the projects ALEGRO (FKZ V230-630-08-TIFA-560) and ASMS (FKZ 50NA0735). At begin of this paper the architecture of the experimental GBAS and the developed integrity monitoring concept will be described. At both stations – at reference and integrity monitoring station – different independent, but hierarchical composed tests are executed to evaluate the quality of signals and the performance of the provided GBAS services. The assessment results were logical linked in a central software module generating the final integrity message RTCM 4083 for the users. A critical point is the optimal choice of performance key identifiers used during the hierarchical composed tests. Based on outlier detection it should be ensured, that only high-quality satellite signals are used to provide GBAS augmentation signals and to support P-DGNSS based positioning. The selection of high-quality satellite signals reduces the number of available signals for positioning and increases the dilution of precision (DOP). Scope of this paper is to investigate the influence of the satellite selecting procedures on the reachable positioning accuracy. The derived results are used to optimise the control and configuration of the techniques realising the selection of satellite signals used for augmentation and positioning.
    CERGAL 2010; 04/2010
  • Evelin Engler, Stefan Schlüter
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    ABSTRACT: Future accurate navigational systems in port areas: - IMO Requirements - IALA Beacon DGNSS and demand on modernisation - Ground Based Augmentation Systems - Experimental GBAS in Research Port Rostock - Integrity Monitoring - Call for backup, redundancy and contingency
    Internationaler Workshop der Maritime Universitiy Szczecin; 02/2010
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    Stefan Schlüter, David Minkwitz, Angelika Hirrle
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    ABSTRACT: Differential Global Navigation Satellite Systems (DGNSS) are a commonly applied technique for safety critical (Safety-of-Life) navigational operations. Since the nineties an augmentation system following the IALA Beacon DGNSS standard has been employed in the maritime sector. As main components the system comprises a reference station and an integrity monitoring station. With the help of the reference station code based corrections are calculated. Simultaneously the reference station and integrity monitoring station run tests regarding the performance of the system to inform the user within a specified time when the system should not be used for navigation. The gained corrections and integrity information are transmitted in the RTCM format via a medium frequency antenna and can be received by users in the surroundings of almost 300 kilometres. The provided corrections represent one of the two key functions of the DGNSS and allow the user to mitigate errors falsifying the own received pseudoranges. The calculated corrections are generated at the reference station site at a certain time. Due to this fact the longer the distance between the reference station and the user is and the more delayed the corrections are the less they are valid. The IALA has specified the accuracy degradation with 0.4 to 1m for each 100nm. Based on measurement activities in the Baltic Sea the paper discusses the performance of the current maritime DGNSS regarding the spatial and temporal decorrelation effects.
    NAVITEC 2010; 01/2010
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    ABSTRACT: The development of new monitoring algorithms needs to have access to a platform that offers flexibility, operational evaluation facilities, test and validation capacities. DLR’s GBAS test bed offers all these features with additional simulation capability. This paper illustrates these properties by showing an application of the recently developed absolute ionosphere gradient monitor by taking advantage of a network of three reference receivers located in the DLR’s research airport at Braunschweig. This paper presents a first draft of an absolute ionosphere gradient monitor capable of detecting gradients from 300 mm/km to 2000 mm/km in order to fulfill the GAST-D requirements in terms of ionospheric gradient monitoring for the ground subsystem. The three receivers give the possibility to build two independent Absolute Slant Ionosphere Gradient Monitors (ASIGM). The performances achieved depend on the performances of the receivers, their relative location and the orientation of their baselines with respect to the runway direction. ASIGM with baseline in the direction of the runway provide the best observability of an ionsphere gradient that a GBAS user can experience during the approach phase (for straight-in approaches). The smaller the angle between the runway and the considered monitor baseline is, the lower the uncertainty of the gradient in the direction of the runway. Distribution of receivers parallel to the runway provides the best observability conditions. This paper gives the optimal relative location of receivers in order to achieve 100% detectability in the 300 to 2000 mm/km range of the absolute slant ionosphere gradient. Two configurations were investigated: one with 3 and another one with 4 receivers linearly distributed. The results obtained are extremely promising for the GAST-D requirements fulfillment and the corresponding architectures can easily be implemented.
    ENC GNSS 2010; 01/2010
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    ABSTRACT: The project ALEGRO is one of the initial projects of the “Forschungshafen Rostock” initiative (Research Port Rostock) geared towards the development and setup of maritime Ground Based Augmentation Systems (GBAS). The development of differential positioning methods was accelerated by the civilian community of GPS users at the beginning of the 1990s in order to effectively reduce accuracy problems with single-frequency GPS positioning. At the same time, IALA DGNSS networks were set up for maritime applications in order to reliably ensure accuracy to within 10 m in coastal areas, in compliance with the International Maritime Organization’s (IMO) requirements for GPS-based positioning systems. Meanwhile, the performance requirements set by the IMO for GNSS-based localizations have risen. To ensure accuracy in the decimetre range while simultaneously monitoring integrity in port areas, augmentation systems are still required, though with more modern techniques. According to initial studies by IALA (International Association of Marine Aids to Navigation and Lighthouse Authorities), augmentation systems suitable for this are those which use pseudolites or phase-based differential methods. To fulfil the safety requirements, users of GNSS/GBAS-based localization systems must be informed within a few seconds in case of the occurrence of system errors and signal interference that result in losses of accuracy greater than the tolerable positioning error. The challenge here is to develop integrated systems allowing high-precision localizations combined with integrity monitoring under all conditions. This technology is the prerequisite on the road to automated berthing manoeuvres. The primary goal of this project was the development of hardware and software for a phase-based GBAS (Ground Based Augmentation System) experimentation system at the Port of Rostock. The key element in the GBAS processing system is the "GNSS Performance Assessment Facility". It derives pseudorange domain and position domain alarms from the incoming receiver data streams to provide a first real-time integrity monitoring of the used GNSS. The decision process for the selection of measured values, to be broadcast from the reference station to the users is based on specific test algorithms. To obtain quality estimations these algorithms infer from the relationship between reference values measured in real time, station-specific reference values, and positioning with the DIA process (Detection, Identification and Adaptation) at the established location.
    Marine Traffic Engineering MTE09; 10/2009
  • Dietmar Klähn, Stefan Schlüter, Carsten Becker
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    ABSTRACT: Beschreibung der Implementierung, der IO-Schnittstellen, der Konfiguration und der Verifikationsergebnisse des ALEGRO DOP-Processors (DOP=Dilution of Precision). Der Prozessor dient der Darstellung verschiedener DOPs (PDOP, GDOP, HDOP und VDOP) am Ort einer ALEGRO.Referenzstation zur Abschätzung der erreichbaren stand-alone Positionierungsperformanz sowohl bei eingeschränkter als auch maximaler Satellitenverfügbarkeit.
    12/2008;
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    ABSTRACT: Das Projekt ALEGRO wurde durch das Wirtschaftsministerium des Landes Mecklenburg-Vorpommern (FKZ: V230-360-08-TIFA-560) gefördert und durch das Institut für Kommunikation und Navigation des Deutschen Zentrums für Luft- und Raumfahrt e.V. im Zeitraum 1.11.2006 bis 30.09.2008 durchgeführt. Ziel des Projekts ALEGRO war der Aufbau eines lokalen Ergänzungssystems (GBAS-Ground Based Augmentation System), das die Entwicklung von hochpräzisen und sicherheitskritischen GNSS- und GALILEO-Anwendungen im maritimen Sektor und insbesondere im Hafen Rostock unterstützt. ALEGRO, wie auch das bei EADS Rostock Systemtechnik (RST) durchgeführte Vorhaben SEA GATE, waren dabei auf den prototypischen Aufbau von Ground Based Augmentation Systemen (GBAS) ausgerichtet, wobei der wesentliche Unterschied zwischen beiden Projekten in den verfolgten technologischen Lösungsansätzen besteht. Thematischer Schwerpunkt von SEA GATE ist der Einsatz und die Nutzung von Pseudolites als ergänzende Signalquellen für eine GNSS-basierte Ortung. Thematischer Schwerpunkt von ALEGRO ist die Weiterentwicklung von auf differentiellen, phasenbasierten Echtzeitkorrekturverfahren basierenden GBAS (auch RTK-Verfahren (Real Time Kinematic) genannt) insbesondere in Hinblick auf die für sicherheitskritische Anwendungen notwendige Integritätserfassung und –bewertung. Wesentliche Arbeitsinhalte des Projekts waren der HW- und SW-technische Aufbau eines GBAS-Experimentalsystems Hafen Rostock, die Entwicklung und Implementierung einer „GNSS Performance Assessment Facility“ als Grundelement für das Integritätsmonitoring von GNSS selbst und weiterführend des GBAS sowie die Planung, Durchführung und Auswertung experimentell gestützter Validierungsmaßnahmen in Form von Messkampagnen, Experimenten und Probebetrieb zum Leistungsnachweis einzelner Komponenten sowie des ALEGRO GBAS-Gesamtsystems.
    12/2008;
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    ABSTRACT: Future Global Navigation Satellite Systems (GNSS) like GALILEO or the modernised GPS will support “Safety of Life” (SoL) applications by the self-monitoring of the GNSS performance and by the provision of integrity information in dedicated services. The International Maritime Organisation (IMO A.915(22)) requires horizontal positioning accuracies better than 10 m in oceanic and coastal areas. If the positioning error induced by the used GNSS itself exceeds the tolerable positioning error of 25 m, the GNSS provider must detect this malfunction and inform the GNSS users within 10 s to fulfil the integrity requirement for “Safety of Life” applications. In critical traffic areas like sea channels and ports the desired position accuracy must be higher than 1 m. In case of GNSS based automatic docking manoeuvres the allowed positioning error must be lower than 0.1 m. Due to the fact that increased performance requirements are assigned to bounded areas the use of Ground Based Augmentation System (GBAS) is considered as a suitable technical solution to enable high-precision and reliable navigation in the port area. The project ALEGRO, funded by Mecklenburg-Vorpommern’s Ministry of Economics, Labour and Tourism and realised as one of the initial projects within the Research Port Rostock, is focussed on the development of a maritime GBAS. On the one hand corresponding research activities will be depicted by the description of the developed and deployed experimental GBAS in Rostock port and on the other hand preliminary results will be presented.
    POSITIONs 2008; 10/2008
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    ABSTRACT: As a result of the high quality of positioning and timing service, satellite navigation becomes the primary means of navigation for most of civil applications, worldwide. The trend of integrating satellite navigation with other technologies to obtain very precise and reliable position and time information is highly promoted by the development of the future European satellite navigation system Galileo and the modernization of GPS. In the future a large variety of safety-critical maritime applications will depend on this infrastructure. This paper presents the DLR activities for the development of a maritime ground based augmentation system (GBAS). GBAS in general are focused on users who need assurance of high precise positioning service performance (decimetre) in real-time. In the maritime sector, due to IMO requirements, these are applications as: automated docking, dredging, hydrographical surveying, cargo handling, etc… The paper starts with a brief overview of the ALEGRO project, the frame of this research and development activity. The project has been initiated in 2006 by DLR under the support of the Government of the German Federal State Mecklenburg Western Pomerania and aims for the further development of state-of-the-art real-time kinematic (RTK) technologies towards a maritime GBAS, taking into account the services of the future Galileo. Subsequently, the paper describes the hard- and software architecture of the ALEGRO environment in Rostock, currently consisting of a single Monitoring and Control Station embedded in a data and processing network named EVnet. The description includes details about the service that can be provided to the user of the Test Environment within the vicinity of the port of Rostock. The final section of this paper shows the recent results of the validation activities carried out at the port of Rostock and the results of the algorithm development. The validation activities performed within the project were followed by extensive analysis of the data to identify and evaluate signal disturbances in the port surrounding. These activities have been the base for the design and validation of algorithms for the detection of environmental and atmospheric propagation effects. As discussed in the paper, such effects - decreasing the signal quality and availability - with a strong impact on position and integrity can be a critical issue for the operation and the use of a continuous reliable GBAS service.
    ISIS 2008; 10/2008
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    ABSTRACT: Eine notwendige Grundvoraussetzung für die Überwachung und Steuerung von Verkehrsprozessen jeglicher Art ist die präzise und verlässliche Kenntnis der Position der Verkehrsteilnehmer. Zum Schutz des Lebens im Sinne der Gefahrenvermeidung ist es erforderlich, Positionsgenauigkeiten mit einer definierten Zuverlässigkeit zu gewährleisten. Die Konsequenz ist, dass bei der Entwicklung von neuen Satellitennavigationssystemen wie Galileo aber auch bei der Weiterentwicklung existierender wie GPS ein besonderes Augenmerk auf die Eigenüberwachung der Systemintegrität gelegt wird. Leistungsanforderungen an GNSS-basierte Ortung wurden im maritimen Bereich durch die Internationale Maritime Organisation (IMO) situations- und anwendungsbezogen spezifiziert. So wird es als ausreichend angesehen, dass die Positionsbestimmung auf hoher See und im Küstenbereich mit einer horizontalen Genauigkeit von unter 10 m zu erfolgen hat. Steigt der Positionsfehler systembedingt über 25 m, so ist gefordert, dass der GNSS-Systembetreiber den Nutzer innerhalb von 10 s darüber informiert. Das Integritätsrisiko, das effektiv die maximal erlaubte Wahrscheinlichkeit beschreibt, mit der systembedingte Fehlfunktionen nicht erkannt werden, darf 10-5 innerhalb von 3 Stunden nicht überschreiten. Dieser Bedarf wird durch den Galileo „Safety of Life“-Service (SoL) direkt abgedeckt. In verkehrstechnisch kritischen Bereichen wie Häfen steigt die Genauigkeitsanforderung auf 1 m und bei speziellen Anwendungen wie assistierten Anlegemanövern, Ausbaggerung und Güterumschlag auf 1 dm. Um diese Leistungsanforderungen zukünftig erreichen zu können, sind die Entwicklung ergänzender Verfahren und ihrer technologischen Integration bord- als auch landseitig notwendig. Das Projekt ALEGRO, das vom Wirtschaftsministerium des Landes Mecklenburg-Vorpommern gefördert wird und eines der Initialprojekte des Forschungshafens Rostock ist, zielt auf die Entwicklung und den Aufbau eines maritimen GBAS-Experimentalsystems (Ground Based Augmentation System). In Bezug auf die im Hafengebiet zu erreichenden Genauigkeiten wird die RTK-Technologie (Real Time Kinematic) als der geeignete Lösungsansatz gesehen. Diese Verfahren sind in Bezug auf die zu gewährleistende Integrität und auf die zukünftige Nutzung von Galileo weiterzuentwickeln. Eine dafür grundlegende Komponente dieses Systems ist die Eigenüberwachung der GNSS-Signale. Ihre Aufgabe ist neben der Bewertung der GNSS-Signalqualität insbesondere die Detektion und Klassifikation lokaler Störungen in Folge von Signalausbreitungseffekten und Interferenzen. Durch die Integration dieser in Echtzeit abgeleiteten Qualitätskenngrößen wird eine situationsangepasste Datenprozessierung bei der Bereitstellung von Ergänzungs- und Korrekturinformationen für lokale Nutzer und bei der zugeordneten Positionsbestimmung verfolgt. Im Rahmen des Vortrages werden die Entwicklungsstrategie des laufenden Projektes und bereits erreichte Ergebnisse vorgestellt.
    GeoForum MV; 04/2008
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    Stefan Schlüter, Angelika Hirrle
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    ABSTRACT: Das Projekt ALEGRO ist eines der Initialprojekte des Forschungshafens Rostock und ist auf die Entwicklung und Demonstration von Ground Based Augmentation Systems (GBAS) für maritime „Safety of Life“-Anwendungen ausgerichtet. Im Zeitraum vom 29.01.2007 bis zum 02.02.2007 wurde durch das DLR und im Rahmen des Projek-tes ALEGRO im Hafengebiet der Stadt Rostock eine GNSS-Messkampagne durchgeführt. Zielstellung der Aktivität war die Gewinnung von GNSS-Daten in einem maritimen Umfeld. In diesem Bericht werden die Ergebnisse der Analyse von Positionsverfügbarkeit und -Qualität (Ge-nauigkeit) der oben aufgeführten Empfänger bzw. Positionierungsverfahren zusammengefasst.
    01/2008;
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    ABSTRACT: In the framework of the establishment of the Rostock Research Harbour, the project ALEGRO, aiming at the “Installation of a local maritime augmentation system to support high precision application and service of GALILEO within the Rostock Research Harbour” was initiated by DLR under the support of the Government of German Federal State Mecklenburg-Vorpommern. According to the baseline of the project, aiming at the Deployment of a maritime Test Bed for the Application and Validation of Galileo Core Technologies in the maritime Environment, it was decided to perform the projects in three stages. Within the first step the flexible EVnet (Experimentation and Verification Network of the IKN) based infrastructure was developed as a basis for the GNSS algorithms to be developed and implemented in the second step. Finally, in the last step experimentations will be performed to verify and demonstrate the application potential of the maritime GBAS system, namely to Galileo. In the paper the outcomes of the first step will be presented and discussed. To this purpose, the ALEGRO infrastructure components will be introduced and the methodologies for the investigation of the performance and the quality of real time positioning will be detailed. The basic intention was to identify and evaluate signal disturbances in the harbour surrounding and to validate algorithms that have been developed by the authors for the detection of environmental and propagation effects decreasing the signal quality and availability. Therefore an EVnet compatible reference station was operated to provide the opportunity to detect various signal disturbances such as multipath and shadowing effects, aiming to place the reference station at an optimal position. For the first experiments and evaluations, a reference station tracking current GPS and GLONASS systems was equipped with a RTK option. At rover site, three different positioning methods (GPS GLONASS stand-alone, GPS/EGNOS, and real time RTK using GPS and GLONASS) have been implemented. Since all receivers make use of the same antenna, equal receiving conditions could be assumed, and therefore the derived quality and reliability parameters are comparable. Professional geodetic GPS processing software was used to compute high precision reference trajectories for the evaluation of the accuracy of the various rover positioning results. The experiments have been realized on four consecutive days in almost the same scenario. As a result of the data analysis we have gained first experience and knowledge concerning infrastructure and algorithms needed to achieve reliable real-time positioning performance in the maritime environment. On water, in the air and ashore the future European Satellite Navigation System GALILEO will offer an alltime high precision and integrity. Because of its modular set up and expansibility ALEGRO can beconsidered a basis for the development of future Galileo GBAS systems for safe and efficient maritime transport and traffic processes like collision avoidance, docking manoeuvre and cargo handling.
    Toulouse Space Show'08; 01/2008
  • Conference Paper: Research Port Rostock
    Evelin Engler, Stefan Schlüter
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    ABSTRACT: Vorstellung des Netzwerks Forschuungshafen Rostock; Aufgaben, Inhalte und Zeitplan der Initialprojekte SEA GATE (EADS RST) und ALEGRO (DLR);
    Galileo in FP 7, International Information Day; 11/2007
  • Stefan Schlüter, Evelin Engler, Jamila Bouaicha
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    ABSTRACT: Vortragsinhalt: Kurze Einführung in die Themengebiete GNSS und GBAS. Vorstellung des Projektes ALEGRO, dass sich mit dem Thema hochpräzise Satellitennavigation in Häfen auseinandersetzt und die Darstellung der ersten im Projekt gewonnen Ergebnisse (Auswertung von GPS/GLONASS-Daten, aufgenommen in der Messkampagne vom 30.01.2007-02.02.2007 im Seehafen Rostock).
    Seminar des Instituts für physikalische Ozeanographie; 10/2007
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    ABSTRACT: Anwendung GNSS (GPS, Glonass, Galileo) im maritimen Sektor, Überblick Projekt ALEGRO im Forschungshafen Rostock, Durchführung Initialmesskamapgane: - Beschreibung Versuchsaufbau und -Ziele - Erreichte Genauigkeit und Verfügbarkeit - Identifizierte Probleme, abgeleiteter Entwicklungsbedarf
    DGOB Schifffahrtstage 1/2007; 03/2007
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    ABSTRACT: The paper presents a technique realising cycle slip detection and correction using only the data stream of one carrier phase. A needed condition is the provision of phase measurements with an update rate higher than 1 Hz.
    3rd ESA workshop on Satellite Navigation User Equipment Technology; 09/2006
  • ETC 2006; 05/2006

Publication Stats

253 Citations
11.68 Total Impact Points

Institutions

  • 2003–2006
    • University of Leipzig
      • Institute for Meteorology
      Leipzig, Saxony, Germany
  • 2004–2005
    • German Aerospace Center (DLR)
      • Institute of Communications and Navigation
      Köln, North Rhine-Westphalia, Germany