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  • Two-component model of topside ionosphere electron density profiles retrieved from GNSS radio occultations

     Gonzalez Casado, Guillermo; Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel; Sanz Subirana, Jaime
    Journal of geophysical research
    Date of publication: 2013
    Journal article

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    A simple model for the topside ionosphere region is introduced and applied to fit radio-occultation retrieved electron density profiles for altitudes above the F2-peak. The model considers two isothermal components representing the population of the O+ (ionosphere component) and the H+ (protonosphere component) ions. The purpose of the model is to achieve an accurate fit of the observed profiles in the topside ionosphere region while, at the same time, allowing a direct and simple derivation of two important ionospheric parameters, namely, the O+ vertical scale height and the upper transition height. Covering a time period of one year, the fits with the two-component model function are compared with those achieved with one-component functions commonly used in the literature and it is shown that the former provides significantly better fits than the later, with more than a factor of two improvement. The model predictions concerning: the correlation between the O+ vertical scale height and the upper transition height, the altitude dependence of the vertical scale height of the electron density, and the quantitative contribution of the protonosphere to the total electron content are examined and shown to be consistent with the observations and with previous studies. It is concluded that the model provides a realistic description of the vertical distribution of the two main ion constituents of the topside ionosphere.

  • Definition of an SBAS ionospheric activity indicator and its assessment over Europe and Africa During the last solar cycle

     Sanz Subirana, Jaime; Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel; Prieto Cerdeira, Roberto; Schlueter, Stefan
    International Beacon Satellite Symposium
    Presentation's date: 2013-07
    Presentation of work at congresses

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    In this work, an ionospheric activity indicator is defined based in the ¿weighted¿ Along Arc TEC rate (AATR). It is shown that this indicator, which can be easily computed from the GPS carrier phases, is well correlated with the ionospheric activity and, unlike other global indicators linked to the geomagnetic activity, can be sensitive to regional behaviours of ionospheric activity

  • Solar EUV flux rate estimation during mid and strong flares from the ionospheric electron content response signature in GNSS observations

     Hernandez Pajares, Manuel; Garcia Rigo, Alberto; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Monte Moreno, Enrique; Aragon Angel, Maria Angeles
    European Conference on Antennas and Propagation
    Presentation's date: 2013-04-08
    Presentation of work at congresses

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    A simple and precise technique to measure the sudden Extreme Ultraviolet (EUV) radiation increase of the Sun, during mid and strong flares, has been formulated and demonstrated for the most active part of the last Solar Cycle. On the one hand, it is based on the short time scale of these events, which allows the validity of a simple global overionization model. And on the other hand on the prompt ionospheric response to the EUV ionization, which signature (in terms of the Global Navigation Satellite Systems -GNSSSolar Flare Activity Indicator, GSFLAI) is accurately measured in real-time from the existing global networks of dual-frequency GNSS receivers, and with a time resolution higher that those of dedicated space probes. Moreover the sensitivity of this approach enables the detection of not only extreme X-class flares, but also the detection of variations of one order of magnitude lower or even smaller (such as for M-class flares): 100% successful detection for all the X-class solar flares during 2000-2006 with registered location outside of the solar limb (i.e. detection of 94% of all of X-class solar-flares) and about 65% for M-class ones, obtained with the associated SISTED detector. In summary, its full availability, continuity, high precision and integrity for mid and high solar flare effects on Ionosphere, can make GSFLAI an useful indicator of potential Space Weather activity for many users in radio propagation. These results, which have been recently published by the authors, are extended in this work up to one complete solar cycle, and using a lower sampling rate (30 seconds), demonstrating the better behaviour of this indirect solar EUV variability proxy (GSFLAI30), when comparisons are made with direct measurements from space probes, providing readings which can be affected by the late enhancement of particles.

  • Characterization and modelling of the ionosphere for EGNOS development and qualification

     Schlüter, S.; Prieto Cerdeira, Roberto; Orús Pérez, Raul; Lam, J.P.; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Hernandez Pajares, Manuel
    The European Navigation Conference
    Presentation's date: 2013-04-23
    Presentation of work at congresses

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    The availability of representative data samples, models and statistical information derived from the analysis of parameters that adequately describe the state of the ionosphere are key elements for the design, verification and qualification of EGNOS algorithms. As part of the on-going evolutions of EGNOS V2 releases, and also in support to the development of a future multi-constellation and dual-frequency SBAS (EGNOS V3), ESA has started a refinement process of the tools, data and precise definition of the ionospheric operational conditions. A particular driver for this process is the improvement of the availability performance of the current and future system especially under solar max and severe ionospheric conditions, without degradation of integrity and accuracy performances. The paper provides an overview about the concept and the data and models used for EGNOS development and qualification. It outlines the approaches to generate reference models and describes the parameter used for the characterization of nominal and perturbed ionospheric conditions from an SBAS perspective.

  • Ionospheric activity in the South East Asian region

     Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Prieto Cerdeira, Roberto; Schlueter, Stefan
    International Conference on Space, Aeronautical and Navigational Electronics
    Presentation's date: 2013-12-03
    Presentation of work at congresses

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    A SBAS Ionospheric Activity indicator, based in the RMS of Along Arc TEC Rate (AATR) computations has been defined by the gAGE/UPC authors in the context of previous studies on EGNOS Ionosphere. This indicator can be easily computed from GNSS data and, unlike other global indices which are related with the geomagnetic activity, it is sensible to the regional behaviour of the ionosphere. After a deep assessment done over Europe and Africa during the last Solar Cycle, this AATR indicator has been chosen as the metric to characterise the ionospheric operational conditions in the frame of ESA EGNOS activities (EGNOS V3 Mission Requirements). In this work we summarise the results of the application of the AATR indicator to the analysis of the ionospheric activity during an entire Solar Cycle in the South of Asia (SEA) Region. This region has special interest from the ionospheric point of view, because the larger Slant Total Electron Content (STEC) values and gradients experienced due to its proximity to the ionospheric equatorial anomaly.

  • New indicator for definition of ionospheric operational conditions

     Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Hernandez Pajares, Manuel; Prieto Cerdeira, Roberto; Schlueter, Stefan
    SBAS-IONO
    Presentation's date: 2013-07-12
    Presentation of work at congresses

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  • GNSS Data Processing, Vol 2: Laboratory exercises , (ESA TM-23/2, May 2013)

     Sanz Subirana, Jaime; Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel
    Date of publication: 2013-05-01
    Book

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    This two-volume book contains a self-learning course and software tools aimed at providing the necessary background to start work in an operative way in GNSS navigation. The books are focused on the instrumental use of concepts and techniques involved in GNSS navigation and include all the elements needed to understand how the system works and how to work with it. After working through the two volumes, students should be able to develop their own tools for high-accuracy navigation, implementing the algorithms and expanding the skills learned. The first volume is devoted to theory, providing a summary of GNSS fundamentals and algorithms. The second volume is devoted to laboratory exercises, with a wide range of selected practical examples going further into the theoretical concepts and their practical implementation. The exercises have been developed with a specialised software package (the ESA/U PC gLAB educational SW, on an attached CD) and selected data files are provided for the laboratory sessions.

  • GNSS Data Processing, Vol1: Fundamentals and Algorithms, (ESA TM-23/1, May 2013)

     Sanz Subirana, Jaime; Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel
    Date of publication: 2013-05-01
    Book

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    This two-volume book contains a self-learning course and software tools aimed at providing the necessary background to start work in an operative way in GNSS navigation. The books are focused on the instrumental use of concepts and techniques involved in GNSS navigation and include all the elements needed to understand how the system works and how to work with it. After working through the two volumes, students should be able to develop their own tools for high-accuracy navigation, implementing the algorithms and expanding the skills learned. The first volume is devoted to theory, providing a summary of GNSS fundamentals and algorithms. The second volume is devoted to laboratory exercises, with a wide range of selected practical examples going further into the theoretical concepts and their practical implementation. The exercises have been developed with a specialised software package (the ESA/U PC gLAB educational SW, on an attached CD) and selected data files are provided for the laboratory sessions. This is an end-to-end GNSS course addressed to all professionals and students who wish to undertake a deeper study of satellite navigation, targeting the GNSS data processing and analysis issues.

  • Impact of higher order ionospheric delay on precise GNSS computation

     Hernandez Pajares, Manuel; Aragon Angel, Maria Angeles; Defraigne, Pascale; Bergeot, Nicolas; Prieto Cerdeira, Roberto; Sanz Subirana, Jaime
    International Colloquium Scientific and Fundamental Aspects of the Galileo Programme
    Presentation's date: 2013-12
    Presentation of work at congresses

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  • Enhanced precise point positioning for GNSS users

     Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel; Sanz Subirana, Jaime; Ramos Bosch, Pedro; Aragon Angel, Maria Angeles; Orús Pérez, Raul; Ochieng, Washington; Feng, Shaojun; Jofre, Martí; Coutinho, Pedro; Samson, Jaron; Tossaint, Michel Mathias Maria
    IEEE transactions on geoscience and remote sensing
    Date of publication: 2012-09-21
    Journal article

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    This paper summarizes the main results obtained during the development of an Enhanced Precise Point Positioning (EPPP) Global Navigation Satellite Systems multifrequency user algorithm. The main innovations include the application of precise ionospheric corrections to facilitate the resolution of undifferenced carrier phase ambiguities, ambiguity validation, and integrity monitoring. The performance of the EPPP algorithm in terms of accuracy, convergence time, and integrity is demonstrated with actual GPS and simulated Galileo data. This can be achieved with very limited bandwidth requirements for EPPP users (less than 300 b/s for dual-frequency GPS data).

    This paper summarizes the main results obtained during the development of an Enhanced Precise Point Positioning (EPPP) Global Navigation Satellite Systems multifrequency user algorithm. The main innovations include the application of precise ionospheric corrections to facilitate the resolution of undifferenced carrier phase ambiguities, ambiguity validation, and integrity monitoring. The performance of the EPPP algorithm in terms of accuracy, convergence time, and integrity is demonstrated with actual GPS and simulated Galileo data. This can be achieved with very limited bandwidth requirements for EPPP users (less than 300 b/s for dual-frequency GPS data).

  • Fast Precise Point Positioning for decimeter-error-level navigation for multi and single-frequency users of Global Navigation Satellite Systems

     Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel; Sanz Subirana, Jaime; Samson, J.; Tossaint, M.
    European Calibration and Orientation Workshop
    Presentation's date: 2012-02
    Presentation of work at congresses

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    This manuscript summarizes the new algorithm of Fast Precise Point Positioning (FPPP) the developed during the projects "Enhanced PPP GNSS multifrequency user algorithm" and ¿Precise Real Time Orbit Determination and Time synchronisation¿, both funded by the European Space Agency (ESA). The main innovations achieved during the overall project comprise the application of precise ionospheric corrections to facilitate the fast resolution of undifferenced carrier phase ambiguities, ambiguity validation and integrity monitoring for both multi- and single-frequency users. Among the integrity, detailed in previous works, the performance of the FPPP algorithm in terms of improved accuracy and convergence time is demonstrated with actual GPS and simulated Galileo data. The 10-centimeters error level real-time kinematic positioning can be achieved in few minutes for dual-and single-frequency users, almost instantaneous for three-frequency users (or once the tropospheric delay is well estimated in few minutes in cold start), and with very limited bandwidth requirements for the FPPP users (less than 300 bps for dual-frequency GPS)

  • Fast precise point positioning performance based on international GNSS real-time service data

     Rovira Garcia, Adrià; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Hernandez Pajares, Manuel
    ESA Workshop on Satellite Navigation Technologies
    Presentation's date: 2012-12-05
    Presentation of work at congresses

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  • Plasmaspheric Electron Content contribution inferred from ground and radio occultation derived Total Electron Content

     Aragon Angel, Maria Angeles; Sanz Subirana, Jaime; Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel; Altadill, D.
    IEEE International Conference on Communications
    Presentation's date: 2012
    Presentation of work at congresses

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  • Propagation of medium scale traveling ionospheric disturbances at different latitudes and solar cycle conditions

     Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Aragon Angel, Maria Angeles
    Radio science
    Date of publication: 2012
    Journal article

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    Wide Area RTK: a satellite navigation system based on precise real-time ionospheric modelling  Open access

     Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Hernandez Pajares, Manuel; Samson, Jaron; Tossaint, Michel Mathias Maria; Aragon Angel, Maria Angeles; Salazar Hernández, Dagoberto José
    Radio science
    Date of publication: 2012-04-19
    Journal article

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    The Wide Area Real Time Kinematic (WARTK) is an augmentation system concept for multi-frequency users based on precise real-time ionospheric modeling. It is able to provide a high accuracy and integrity GNSS positioning service over continental areas using the infrastructure of a network of permanent ground monitor stations, such as the European Geostationary Navigation Overlay Service (EGNOS) network of Ranging and Integrity Monitoring Stations (RIMS) in Europe. In this way, it allows an additional benefit to be obtained from these reference stations, that is, the network has the potential to support two independent systems: a satellite-based augmentation system, such as EGNOS, and a high-precision positioning service, based on WARTK. Indeed, thanks to the accuracy of the ionospheric corrections provided, WARTK users have available in real-time an extra constraint per satellite between the carrier phase ambiguities, which helps solve them quickly. Once such ambiguities have been solved, the GNSS user obtains navigation accurate to within 20 cm at the 95th percentile (about 10 cm RMS). Moreover, this precise positioning is achieved in a few minutes (with two frequency signals) or in a single epoch, after initial convergence of the tropospheric delay (with three frequency signals), even up to hundreds of kilometers away from the nearest reference station. While previous WARTK research has been devoted to implementing the concept and assessing its feasibility, considering in particular the accuracy achievable, the work reported in this paper focused on consolidating the results by analyzing a large and representative data set, and on deeper analysis of the integrity issue. It was carried out in the context of the Multi-constellation Regional System (MRS) project, within the European Space Agency GNSS Evolution Programme, with the aim of designing a high accuracy service for GPS and/or Galileo. Three months of actual data, from more than 25 permanent GPS stations in Europe, have been processed (some of them as a roving user), for high-, mid- and low-solar cycle conditions (in 2002, 2004 and 2006 respectively). In addition, several ionospheric storms occurred during the selected periods, with Dst values reaching up to −150 nT. Results based on these data show that user domain integrity was maintained for baselines of up to 400 km. At the 95th percentile, the daily horizontal and vertical position errors were 20 and 30 cm, respectively, and the corresponding protection levels were about 1 and 2 m. The convergence time was around 5 minutes with actual GPS constellation data. The benefits of using a multi-constellation system were also studied, with simulated GPS and three-frequency Galileo data, showing that it is possible to reduce the convergence time to a few seconds.

  • GNSS measurement of EUV photons flux rate during strong and mid solar flares

     Hernandez Pajares, Manuel; Garcia Rigo, Alberto; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Monte Moreno, Enrique; Aragon Angel, Maria Angeles
    Space weather: the international journal of research and applications
    Date of publication: 2012-12-12
    Journal article

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  • Contributions to ionospheric determination with Global Positioning System: solar flare detection and prediction of global maps of Total Electron Content.  Open access

     Garcia Rigo, Alberto
    Defense's date: 2012-12-17
    Universitat Politècnica de Catalunya
    Theses

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    Two research studies have been addressed in this thesis. Both of them are of actual scientific interest and are based on processing GNSS data. The first part of this thesis is devoted to GNSS detection and monitoring of solar flares. The second one is devoted to GNSS prediction of ionospheric Total Electron Content. Regarding the first study, a new solar flare detector called SISTED has been designed and implemented. Its goal is to provide a simple and efficient way of detecting the most number of powerful X-class solar flares in real time operation. In addition, it can send early warning messages to prevent the harmful consequences of the increase of ejected particles from the Sun that may reach the Earth after a solar flare, especially in case of a Coronal Mass Ejection. The main benefit of SISTED regarding other detection techniques is that it does not require data from external providers out of the GNSS community. In addition, it can run in real-time operation and could provide value added data to GNSS users. The results show that SISTED was able to detect up to the 95% of the X-class flares reported by GOES for more than a half solar cycle. Regarding the second study, a new approach to predict Global Ionospheric vertical TEC Maps has been designed and implemented in the context of the IGS Ionosphere Working Group. The motivation to develop a UPC Predicted product was the interest of ESA's SMOS mission. A recent application using UPC Predicted products is the generation of real-time global VTEC maps as background model. In addition, the predicted VTEC maps are used to generate the combined IGS Predicted products. The results obtained in this thesis show that the model performs well when the results are compared with those obtained by the other IGS analysis centers. In addition, applying the prediction model leads to better results than the use of time-invariant ionosphere for two days ahead. In relation with this research, 4 publications in international journals indexed in JCR/ISI have been generated (and another one is under review process), and 7 presentations have been authored in international meetings, among the new UPC predicted product contributing to IGS, and the contribution to two competitive projects funded by the European Space Agency (AGIM and MONITOR).

  • GNSS Education Network for Industry and UniversitieS

     Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime
    Participation in a competitive project

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    Integrity monitoring for carrier phase ambiguities  Open access

     Feng, Shaojun; Ochieng, Washington; Samson, Jaron; Tossaint, Michel Mathias Maria; Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Aragon Angel, Maria Angeles; Ramos Bosch, Pedro; Jofre, Martí
    Journal of navigation
    Date of publication: 2012-01
    Journal article

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    The determination of the correct integer number of carrier cycles (integer ambiguity) is the key to high accuracy positioning with carrier phase measurements from Global Navigation Satellite Systems (GNSS). There are a number of current methods for resolving ambiguities including the Least-squares AMBiguity Decorrelation Adjustment (LAMBDA) method, which is a combination of least-squares and a transformation to reduce the search space. The current techniques to determine the level of confidence (integrity) of the resolved ambiguities (i.e. ambiguity validation), usually involve the construction of test statistics, characterisation of their distribution and definition of thresholds. Example tests applied include ratio, F-distribution, t-distribution and Chi-square distribution. However, the assumptions that underpin these tests have weaknesses. These include the application of a fixed threshold for all scenarios, and therefore, not always able to provide an acceptable integrity level in the computed ambiguities. A relatively recent technique referred to as Integer Aperture (IA) based on the ratio test with a large number of simulated samples of float ambiguities requires significant computational resources. This precludes the application of IA in real time. This paper proposes and demonstrates the power of an integrity monitoring technique that is applied at the ambiguity resolution and positioning stages. The technique has the important benefit of facilitating early detection of any potential threat to the position solution, originating in the ambiguity space, while at the same time giving overall protection in the position domain based on the required navigation performance. The proposed method uses the conventional test statistic for ratio testing together with a doubly non-central F distribution to compute the level of confidence (integrity) of the ambiguities. Specifically, this is determined as a function of geometry and the ambiguity residuals from least squares based ambiguity resolution algorithms including LAMBDA. A numerical method is implemented to compute the level of confidence in real time. The results for Precise Point Positioning (PPP) with simulated and real data demonstrate the power and efficiency of the proposed method in monitoring both the integrity of the ambiguity computation and position solution processes. Furthermore, due to the fact that the method only requires information from least squares based ambiguity resolution algorithms, it is easily transferable to conventional Real Time Kinematic (RTK) positioning.

  • Method, apparatus and system for determining a position of an object having a Global Navigation Satellite System receiver by processing undifferenced data like carrier phase measuurements and external products like ionosphere data

     Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Samson, Jaron; Tossaint, Michel Mathias Maria
    Date of request: 2012-10-04
    Invention patent

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    Real time Ionospheric determination at global scale  Open access

     Hernandez Pajares, Manuel; Sanz Subirana, Jaime; Garcia Rigo, Alberto
    International Geomatic Week
    Presentation's date: 2011-03-15
    Presentation of work at congresses

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    The global ionospheric determination has been possible in the last 15 years thanks to the availability of a new type of ionospheric sensor with a very high spatial and temporal sampling: the dual-frequency GPS receivers. Indeed, several hundreds of them, worldwide distributed, are freely available, tracking typically 6+ GPS satellites in view, providing at every epoch several thousands of line-of-sight integrated free electron densities (Slant Total Electron Content, STEC). This has allowed in particular to compute and freely distribute global Vertical Total Electron Content (VTEC) maps, in the context of the open- product organization called International GNSS Service (IGS), which applications run from single frequency receivers (accurate mitigation of ionospheric delay), calibration of new altimeters (such as the SMOS mission) up to the potential use for increasing the performance of positioning based on carrier phase measurements. One of the next challenges, in particular in IGS, is computing the global VTEC maps, in real-time, which involves much less permanent receivers, increasing much more the di cult task of interpolating in a realistic way the electron content over large regions with few receivers (south hemisphere, oceans...). In this paper the actual status of the problem will be presented, from the perspective of gAGE/UPC, one of the four IGS Ionospheric Analysis Centers, participating in the Real-Time IGS Pilot Project.

  • The ionosphere: effects, GPS modeling and the benefits for space geodetic techniques

     Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Aragon Angel, Maria Angeles; Salazar Hernández, Dagoberto José; Escudero Royo, Miguel
    Journal of geodesy
    Date of publication: 2011-09-10
    Journal article

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  • Global prediction of the vertical total electron content of the ionosphere based on GPS data

     Garcia Rigo, Alberto; Monte Moreno, Enrique; Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Aragon Angel, Maria Angeles; Salazar Hernández, Dagoberto José
    Radio science
    Date of publication: 2011-12-29
    Journal article

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  • MONITORIZADO Y ANALISIS DE LAS CARACTERISTICAS GEOMAGNETICAS Y IONOSFERICAS EN ASJI. MODELADO IONOSFERICO

     Aragon Angel, Maria Angeles; Juan Zornoza, Jose Miguel; Hernandez Pajares, Manuel; Escudero Royo, Miguel; Gonzalez Casado, Guillermo; Rovira Garcia, Adrià; Garcia Rigo, Alberto; Sanz Subirana, Jaime
    Participation in a competitive project

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  • Enhanced Precise Point Positioning (EPPP) for single frequency users

     Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime
    Date: 2011-09-01
    Report

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  • PRODTS TN FR: Final Report

     Juan Zornoza, Jose Miguel; Ramos Bosch, Pedro; Sanz Subirana, Jaime; Aragon Angel, Maria Angeles
    Date: 2011-02-28
    Report

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  • Report on the State of Art of GBAS

     Juan Zornoza, Jose Miguel; Aragon Angel, Maria Angeles; Garcia Rigo, Alberto; Gonzalez Casado, Guillermo; Salazar Hernández, Dagoberto José; Sanz Subirana, Jaime
    Date: 2011-01-21
    Report

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  • IONO-DECO monthly progress report no 3

     Hernandez Pajares, Manuel; Sanz Subirana, Jaime; Defraigne, P; Bergeot, N; Baire, Q; Aragon Angel, Maria Angeles; Garcia Rigo, Alberto
    Date: 2011-09-30
    Report

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  • Development of a GBAS ground station prototype, algorithms, PROMETEO/1/2011

     Sanz Subirana, Jaime; Gonzalez Casado, Guillermo; Juan Zornoza, Jose Miguel
    Date: 2011-06-06
    Report

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  • Precise real time GPS and GALILEO orbit determination & clock synchronization (PRTODTS)

     Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime
    Date: 2011-02-16
    Report

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  • Development of a GBAS ground station prototype: simulated data generation and test results of the GRS in Fortran

     Sanz Subirana, Jaime; Juan Zornoza, Jose Miguel; Garcia Rigo, Alberto; Rovira-Garcia, A.
    Date: 2011-09-16
    Report

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  • Development of a GBAS ground station prototype: algorithms

     Sanz Subirana, Jaime; Gonzalez Casado, Guillermo; Juan Zornoza, Jose Miguel
    Date: 2011-05-06
    Report

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  • Development of a GBAS ground station prototype test results of the GBAS station in MATLAB

     Rovira-Garcia, A.; Sanz Subirana, Jaime; Juan Zornoza, Jose Miguel
    Date: 2011-09-15
    Report

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  • Improvement of retrieved FORMOSAT-3/COSMIC electron densities validated by ionospheric sounder measurements at Jicamarca

     Aragon Angel, Maria Angeles; Liou, Y.-A.; Lee, C.-C.; Reinisch, B. W.; Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime
    Radio science
    Date of publication: 2011-09-01
    Journal article

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  • Ground- and space-based GPS data ingestion into the NeQuick model

     Brunini, Claudio; Azpilicueta, F.; Gende, M.; Camilon, E; Aragon Angel, Maria Angeles; Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime
    Journal of geodesy
    Date of publication: 2011-03-01
    Journal article

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  • Precisió per al sistema Galileo - Informacions UPC

     Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime
    Others' publications about work

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  • Integrity monitoring for carrier phase ambiguities

     Feng, Shaojun; Ochieng, Washington; Samson, Jaron; Tossaint, Michel Mathias Maria; Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Aragon Angel, Maria Angeles; Ramos Bosch, Pedro; Jofre, Martí
    The Institute of Navigation International Technical Meeting
    Presentation's date: 2010-09-23
    Presentation of work at congresses

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  • Wide area real time kinematic: a new augmentation concept towards the definition of a high accuracy and integrity service

     Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Samson, Jaron; Tossaint, Michel Mathias Maria
    International Beacon Satellite Symposium
    Presentation's date: 2010-07-07
    Presentation of work at congresses

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    A High Precision Positioning Service based in the Wide Area RTK is presented in this work. The integrity and the benefits of the multiconstellation system are also discussed.

  • Network-based High Accuracy Positioning with the GPSTk

     Salazar Hernández, Dagoberto José; Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime
    ESA Workshop on Satellite Navigation Technologies
    Presentation's date: 2010-12-09
    Presentation of work at congresses

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    Improvement and validation of retrieved FORMOSAT-3/COSMIC electron densities using Jicamarca DPS  Open access

     Aragon Angel, Maria Angeles; Liou, Y.-A.; C., C Lee; Hernandez Pajares, Manuel; Sanz Subirana, Jaime; Juan Zornoza, Jose Miguel; B.W, Reinisch
    International Beacon Satellite Symposium
    Presentation's date: 2010-06-09
    Presentation of work at congresses

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    UPC VTEC forecast model based on IGS GIMS  Open access

     Garcia Rigo, Alberto; Monte Moreno, Enrique; Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Orus Pérez, Raul
    International Beacon Satellite Symposium
    Presentation's date: 2010-07-08
    Presentation of work at congresses

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  • The ESA/UPC GNSS-Lab tool (gLAB): an advanced multipurpose package to process and analyse GNSS data

     Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Ramos Bosch, Pedro; Rovira-Garcia, A.; Salazar Hernández, Dagoberto José; Ventura-Traveset, J.; Lopez-Echazarreta, C.; Hein, G.
    ESA Workshop on Satellite Navigation Technologies
    Presentation's date: 2010-12-09
    Presentation of work at congresses

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    Real time application of TOMION model  Open access

     Orus Pérez, Raul; Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Aragon Angel, Maria Angeles; Garcia Rigo, Alberto
    International Beacon Satellite Symposium
    Presentation's date: 2010-07-09
    Presentation of work at congresses

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    Since the first development of the TOMION(TOmographic Model of the IONosphere),in1995,gAGE/UPC has been improving the performance and reliability of this technique. The TOMION kernel relies on the computation of the ionospheric electrondensity by means of using a 4D model of the ionosphere. At the beginning the technique was mainly focused on ionospheric determination from a single or few stations using a 2-layer tomographic approach. Further developments lead to the use of TOMION as a global ionospheric scanner,allowing the use of TOMION to produce Global Ionospheric Maps(GIMs)for the International GNSS Service(IGS) jointly with CODE(University of Bern),EMR (Energymines and Resources,NRCAN),ESA (European Space Agency) and JPL(Jet Propulsion Laboratory) since 1st June 1998. Inparallel to this activity, the TOMION capabilities were increased, and the use of more than 2-layers was a natural extension of the model. However, other approaches were introduced, and as a result of that effort the Improved Abel technique, for electrondensity profile retrieving, was developed. This technique was based on the separability hypothesis, which overtook the limitations of the spherical hypothesis for electrondensity retrieval.

  • Using the GPSTk for quick development and validation of GNSS applications

     Salazar, D.; Sanz Subirana, Jaime; Hernandez Pajares, Manuel; Juan, J. M.
    SEAGAL Workshop on GNSS
    Presentation's date: 2010-03-16
    Presentation of work at congresses

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  • GNSS data management and processing with the GPSTk

     Salazar Hernández, Dagoberto José; Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime
    Gps solutions
    Date of publication: 2010
    Journal article

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    We organize complex problems in simple ways using a GNSS data management strategy based on ‘‘GNSS Data Structures’’ (GDS), coupled with the open source ‘‘GPS Toolkit’’ (GPSTk) suite. The code resulting from using the GDS and their associated ‘‘processing paradigm’’ is remarkably compact and easy to follow, yielding better code maintainability. Furthermore, the data abstraction allows flexible handling of concepts beyond mere data encapsulation, including programmable general solvers. An existing GPSTk class can be modified to achieve the goal. We briefly describe the ‘‘GDS paradigm’’ and show how the different GNSS data processing ‘‘objects’’ may be combined in a flexible way to develop data processing strategies such as Precise Point Positioning (PPP) and network-based PPP that computes satellite clock offsets on-the-fly.

  • Wide-Area RTK: high precision positioning on a continental scale

     Hernandez Pajares, Manuel; Juan Zornoza, Jose Miguel; Sanz Subirana, Jaime; Aragon Angel, Maria Angeles; Ramos Bosch, Pedro; Samson, Jaron; Tossaint, Michel Mathias Maria; Albertazzi, Michelangelo; Odijk, Dennis; Teunissen, Peter J. G.; De Bakker, Peter; Verhagen, Sandra; Van Der Marel, Hans
    Inside GNSS
    Date of publication: 2010-03-31
    Journal article

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  • Precise GPS-based position, velocity and acceleration determination: Algorithms and tools  Open access

     Salazar Hernández, Dagoberto José
    Defense's date: 2010-04-29
    Universitat Politècnica de Catalunya
    Theses

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    Esta tesis doctoral llevó a cabo el estudio, desarrollo e implementación de algoritmos para la navegación con sistemas globales de navegación por satélite (GNSS), enfocándose en la determinación precisa de la posición, velocidad y aceleración usando GPS, en modo post-procesado y lejos de estaciones de referencia. Uno de los objetivos era desarrollar herramientas en esta área y hacerlas disponibles a la comunidad GNSS. Por ello el desarrollo se hizo dentro del marco del proyecto preexistente de software libre llamado GPS Toolkit (GPSTk). Una de las primeras tareas realizadas fue la validación de las capacidades de la GPSTk para el procesado del pseudorango, realizando comparaciones con una herramienta de procesamiento de datos probada (BRUS). La gestión de datos GNSS demostró ser un asunto importante cuando se intentó extender las capacidades de la GPSTk al procesamiento de datos obtenidos de las fases de la señal GPS. Por ello se desarrollaron las Estructuras de Datos GNSS (GDS), que combinadas con su paradigma de procesamiento aceleran el proceso de desarrollo de software y reducen errores. La extensión de la GPSTk a los algoritmos de procesado en fase se hizo mediante la ayuda de las GDS, proporcionándose importantes clases accesorias que facilitan el trabajo. Se implementó el procesado de datos Precise Point Positioning (PPP) con ejemplos relativamente simples basados en las GDS, y al comparar sus resultados con otras aplicaciones de reputación ya establecida, se encontró que destacan entre los mejores. También se estudió cómo obtener la posición precisa, en post-proceso, de un receptor GPS a cientos de kilómetros de la estación de referencia más cercana y usando tasas de datos arbitrarias (una limitación del método PPP). Las ventajas aportadas por las GDS permitieron la implementación de un procesado semejante a un PPP cinemático basado en una red de estaciones de referencia, estrategia bautizada como Precise Orbits Positioning (POP) porque sólo necesita órbitas precisas para trabajar y es independiente de la información de los relojes de los satélites GPS. Los resultados de este enfoque fueron muy similares a los del método PPP cinemático estándar, pero proporcionando soluciones de posición con una tasa mayor y de manera más robusta. La última parte se enfocó en la implementación y mejora de algoritmos para determinar con precisión la velocidad y aceleración de un receptor GPS. Se hizo énfasis en el método de las fases de Kennedy debido a su buen rendimiento, desarrollando una implementación de referencia y demostrando la existencia de una falla en el procedimiento propuesto originalmente para el cálculo de las velocidades de los satélites. Se propuso entonces una modificación relativamente sencilla que redujo en un factor mayor que 35 el RMS de los errores 3D en velocidad. Tomando ideas de los métodos Kennedy y POP se desarrolló e implementó un nuevo procedimiento de determinación de velocidad y aceleración que extiende el alcance. Este método fue llamado Extended Velocity and Acceleration determination (EVA). Un experimento usando una aeronave ligera volando sobre los Pirineos mostró que tanto el método de Kennedy (modificado) como el método EVA son capaces de responder ante la dinámica de este tipo de vuelos. Finalmente, tanto el método de Kennedy modificado como el método EVA fueron aplicados a una red en la zona ecuatorial de Sur América con líneas de base mayores a 1770 km. En este escenario el método EVA mostró una clara ventaja tanto en los promedios como en las desviaciones estándar para todas las componentes de la velocidad y la aceleración.

    This Ph.D. Thesis focuses on the development of algorithms and tools for precise GPS-based position, velocity and acceleration determination very far from reference stations in post-process mode. One of the goals of this thesis was to develop a set of state-of-the-art GNSS data processing tools, and make them available for the research community. Therefore, the software development effort was done within the frame of a preexistent open source project called the GPSTk. Therefore, validation of the GPSTk pseudorange-based processing capabilities with a trusted GPS data processing tool was one of the initial task carried out in this work. GNSS data management proved to be an important issue when trying to extend GPSTk capabilities to carrier phasebased data processing algorithms. In order to tackle this problem the GNSS Data Structures (GDS) and their associated processing paradigm were developed. With this approach the GNSS data processing becomes like an assembly line, providing an easy and straightforward way to write clean, simple to read and use software that speeds up development and reduces errors. The extension of GPSTk capabilities to carrier phase-based data processing algorithms was carried out with the help of the GDS, adding important accessory classes necessary for this kind of data processing and providing reference implementations. The performance comparison of these relatively simple GDS-based source code examples with other state-of-the art Precise Point Positioning (PPP) suites demonstrated that their results are among the best. Furthermore, given that the GDS design is based on data abstraction, it allows a very flexible handling of concepts beyond mere data encapsulation, including programmable general solvers, among others. The problem of post-process precise positioning of GPS receivers hundreds of kilometers away from nearest reference station at arbitrary data rates was dealt with, overcoming an important limitation of classical post-processing strategies like PPP. The advantages of GDS data abstraction regarding solvers were used to implement a kinematic PPP-like processing based on a network of stations. This procedure was named Precise Orbits Positioning (POP) because it is independent of precise clock information and it only needs precise orbits to work. The results from this approach were very similar (as expected) to the standard kinematic PPP processing strategy, but yielding a higher positioning rate. Also, the network-based processing of POP seems to provide additional robustness to the results, even for receivers outside the network area. The last part of this thesis focused on implementing, improving and testing algorithms for the precise determination of velocity and acceleration hundreds of kilometers away from nearest reference station. Special emphasis was done on the Kennedy method because of its good performance. A reference implementation of Kennedy method was developed, and several experiments were carried out. Experiments done with very short baselines showed a flaw in the way satellite velocities were computed, introducing biases in the velocity solution. A relatively simple modification was proposed, and it reduced the RMS of 5-min average velocity 3D errors by a factor of over 35. Then, borrowing ideas from Kennedy method and the POP method, a new velocity and acceleration determination procedure named EVA was developed and implemented that greatly extends the effective range. An experiment using a light aircraft flying over the Pyrenees showed that both the modified-Kennedy and EVA methods were able to cope with the dynamics of this type of flight. Finally, both modified-Kennedy and EVA method were applied to a challenging scenario in equatorial South America, with baselines over 1770 km, where EVA method showed a clear advantage in both averages and standard deviations for all components of velocity and acceleration. Lloc i

  • Contributions to ionospheric electron density retrieval  Open access

     Aragon Angel, Maria Angeles
    Defense's date: 2010-02-22
    Universitat Politècnica de Catalunya
    Theses

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    La transformada de Abel es una técnica de inversión usada frecuentemente en radio ocultaciones (RO) que, en el contexto ionosférico, permite deducir densidades electrónicas a partir de datos de STEC (Slant Total Electron Content) derivados a partir de observaciones de la fase portadora. Esta técnica está basada en medidas precisas en doble frecuencia de fase portadora ( banda L) de un receptor GPS a bordo de un satélite de órbita baja (Low Earth Orbit -LEO-) rastreando un satélite GPS detrás del limbo de la tierra. Al combinar tales medidas con la información de posiciones y velocidades de los satélites GPS y LEO, es posible deducir el cambio en el camino de la señal debido a la presencia de la atmósfera y, consecuentemene, convertirlo en ángulos de curvatura (bending angles). A partir de ellos, información sobre el índice de refracción vertical puede ser obtenida a través de técnicas de inversión, y transformarlo en perfiles verticales de densidad electrónica y/o perfiles de atmósfera neutra. Una de las hipótesis básicas de la inversión clásica es suponer que el campo de densidades electrónicas tiene simetría esférica en la vecindad de una ocultación. Sin embargo, a la práctica, la huella de una ocultación generalmente cubre regiones de miles de km que puede presentar variabilidad ionosférica importante; por lo cuál, la hipótesis de simetría esférica no puede ser garantizada. De hecho, las inhomogeneidades de la densidad electrónica en la dirección veritcal para una ocultación dada son una de las principales causas de error cuando se usa la inversión de Abel inversion. Para corregir el error debido a la hipótesis de simetría esférica, se introduce el concepto de separabilidad. Ello implica que la densidad electrónica puede ser expresada como una combinación de datos de Vertical Total Electron Content (VTEC) derivados externamente, los cuales asumen la dependencia horizontal de la densidad, y una función de forma, que a su vez asume la dependencia en altura que es común a todas las observaciones para una ocultación dada. Nótese que el espesor de capa permanece constante cerca de la región de la ocultación debido a la hipótesis de separabilidad en vez de la densidad, como ocurriría en el caso de usar simetría esférica. Esta técnica fue aplicada exitosamente a la combinación lineal de fases de GPS L1 y L2, , LI= L1-2, la cuál proporcionar un observable libre de geometría que depende sólo del retraso ionosférico, la ambigüedad de fase, biases instrumentales y wind-up. Los resultados presentaban una mejora del 40% en RMS al comparar frecuencias del pico de la capa F2 con datos de ionosonda respecto la inversión clásica de Abel. Sin embargo, la potencial influencia de la diferencia de caminos ópticos entre L1 y L2 fue despreciada. Esta tesis doctoral muestra que ello no es un problema para la inversión a alturas ionosféricas. Una alternativa para la inversión de perfiles que evita esta desventaja es usar la curvatura de la señal como dato principal. La implementación de la separabilidad para ángulos de curvatura no es inmediata y ha sido uno de los objetivos de esta tesis. En este sentido, el principio de la separabilidad ha sido aplicado a los ángulos de curvatura de L1 en vez de la la combinación LI como en trabajos anteriores. Además, trabajando con ángulos de curvatura, la separabilidad puede ser también trasladada a la obtención de perfiles troposféricos. Varias aproximaciones para obtener la contribución de las partes altas de la ionosfera han sido también estudiadas, aparte del hecho de simplemente prescindir de esta contribución. Se ha usado un modelo climatológico, una extrapolación exponencial y el hecho de considerar las implicaciones de usar separabilidad. También se ha propuesto una manera para obtener funciones de mapeo (mapping functions) deducidas a partir de perfiles RO. Sin embargo, trabajando sólo con datos derivados únicamente de RO, se está sistematicamente despreciando la contribución de la protonosfera al TEC. Con la propuesta inicial de función de mapeo sólo la contribución ionosférica es tenida en cuenta. La solución ideal para aplicaciones de datos de tierra GNSS sería usar un modelo de dos capas, una para modelar la ionosfera y otra para la protonosfera, o alternativamente, si se quisiera alta resolución tomográfica, combinar observaciones RO y con elevación positiva de LEOs con datos de tierra. Se ha probado que modelando con dos capas, los resultados que se habían obtenido con el análisis de datos RO han podido ser validados. La conclusión más importante es que la proporción entre la contribución ionosférica y protonosférica es el parámetro que explica la localización de las alturas efectivas.

     La transformada d’Abel és una tècnica emprada freqüentment en radio ocultacions (RO) que, en el context ionosfèric, permet deduir densitats electròniques a partir de dades de STEC (Slant Total Electron Content) derivats a partir d’observacions de la fase portadora. Aquesta tècnica està basada en mesures precises en doble freqüència de fase portadora (banda L) d’un receptor GPS a bord d’un satèl·lit d’òrbita baixa (Low Earth Orbit-LEO-) rastrejant un satèl·lit GPS darrere del limb de la terra. En combinar les dites mesures amb la informació de posicions i velocitats dels satèl·lits GPS i LEO, és possible deduir el canvi en el camí del senyal degut a la presència de l’atmosfera i, conseqüentment, convertir-lo en angles de curvatura (bending angles). A partir d’ells, informació sobre l’índex de refracció vertical pot ser obtinguda mitjançant tècniques d’inversió i transformar-lo en perfils verticals de densitat electrònica i/o perfils d’atmosfera neutra. Una de les hipòtesis bàsiques de la inversió clàssica és suposar que el camp de densitats electròniques té simetria esfèrica en el veïnatge d’una ocultació. Tanmateix, a la pràctica, la petjada d’una ocultació generalment cobreix regions de milers de quilòmetres que pot presentar variabilitat ionosfèrica important; per la qual cosa, la hipòtesi de simetria esfèrica no pot ser garantida. De fet, les inhomogeneitats de la densitat electrònica en la direcció vertical per a una ocultació donada són una de les principals causes d’error quan es fa servir la inversió d’Abel. Per a corregir l’error a causa de la hipòtesi de simetria esfèrica, s’introdueix el concepte de separabilitat. Això implica que la densitat electrònica pot ser expressada com una combinació de dades de Vertical Total Electron Content (VTEC) derivats externament, els quals assumeixen la dependència horitzontal de la densitat, i una funció de forma, la qual alhora assumeix la dependència en altura que és comuna a totes les observacions per a una ocultació donada. Cal notar que l’espessor de capa roman constant a prop de la regió de l’ocultació a causa de la hipòtesi de separabilitat en comptes de la densitat, tal i com succeiria en el cas de fer servir simetria esfèrica. Aquesta tècnica fou aplicada amb èxit a la combinació lineal de fases de GPS L1 i L2, LI=L1-2, la qual proporciona un observable lliure de geometria que depèn només del retard ionosfèric, l’ambigüitat de fase, biases instrumentals i wind-up. Els resultats presenten una millora del 40% en RMS en comparar freqüències del pic de la capa F2 amb dades de ionosonda respecte la inversió clàssica d’Abel. No obstant, la potencial influència de la diferència de camins òptics entre L1 i L2 fou menyspreada. Aquesta tesi doctoral mostra que això no és pas un problema per a la inversió a altures ionosfèriques. Una alternativa per a la inversió de perfils que evita aquesta desavantatge és emprar la curvatura del senyal com a dada principal. La implementació de la separabilitat per a angles de curvatura no és immediata i ha estat un dels objectius d’aquesta tesi. En aquest sentit, el principi de la separabilitat ha esta aplicat als angles de curvatura de L1 en comptes de la combinació LI com en treballs anterior. A més, treballant amb angles de curvatura, la separabilitat pot ser també traslladada a l’obtenció de perfils troposfèrics. Varies aproximacions per a obtenir la contribució de les parts altes de la ionosfera han estat també estudiades, apart del fet de prescindir simplement d’aquesta contribució. S’ha fet servir un model climatològic, una extrapolació exponencial i el fet de considera les implicacions d’usar separabilitat. També s’ha proposat una manera pera obtenir funcions de mapeo (mapping functions) deduïdes a partir de perfils RO. Tanmateix, treballant només amb dades derivades únicament de RO, s’està menyspreant sistemàticament la contribució de la protonosfera al TEC. Amb la proposta inicial de funció de mapeo només tenim en compte la contribució ionosfèrica. La solució ideal per a aplicacions de dades de terra GNSS seria fer servir un model de dues capes, una per a modelar la ionosfera i una altra per la protonosfera, o alternativament, si es volgués alta resolució tomogràfica, combinar observacions RO i amb elevació positiva de LEOs amb dades de terra. S’ha provat que modelant amb dues capes, els resultats obtinguts amb l’anàlisi de dades RO han pogut estar validats. La conclusió més important és que la proporció entre la contribució ionosfèrica i protonosfèrica és el paràmetre que explica la localització de les altures efectives.

    The Abel transform is a frequently used radio occultation (RO) inversion technique which, in the ionospheric context, allows retrieving electron densities as a function of height from STEC (Slant Total Electron Content) measurements derived from carrier phase observations. The GPS RO technique is based on precise carrier dual-frequency phase measurements (L-band) of a GPS receiver onboard a Low Earth Orbit satellite (LEO) tracking a rising or setting GPS satellite behind the limb of the earth. When combining such measurements with the information from the positions and velocities of GPS and LEO satellites, it is possible to derive the phase path change due to the atmosphere during an occultation event which subsequently can be converted into bending angles. From these, information about the vertical refraction index can be obtained by means of inversion techniques, which can then be converted into ionospheric vertical electron density profiles and/or neutral atmospheric profiles. One of the basic assumptions in the classical approach is to assume the spherical symmetry of the electron density field in the vicinity of an occultation. However, in practice, the footprint of an occultation generally covers wide regions of thousands of kilometres in length that may show significant ionospheric variability; therefore this hypothesis cannot be guaranteed. Indeed, inhomogeneous electron density in the horizontal direction for a given occultation is believed to be one of the main sources of error when using the Abel inversion. In order to correct the error due to the spherical symmetry assumption, the separability concept is introduced and applied. This implies that the electron density can be expressed by a combination of externally derived Vertical Total Electron Content (VTEC) data, which assumes the horizontal dependency, and a shape function, which in turn assumes the height dependency that is common to all the observations for a given occultation. Note that the slab thickness remains constant near the occultation due to the separability hypothesis instead of the density as is the case of the spherical symmetry. This technique was successfully applied to the linear combination of the GPS carrier phases L1 and L2, , LI= L1-2 which is a geometric free observable that depends only on the ionospheric delay, phase ambiguity, instrumental bias and wind-up. The result was an improvement of about 40% in RMS when comparing frequencies of the F2 layer peak with ionosonde data and the classical Abel inversion. The main advantage of such developed technique is its simple computation. Nevertheless, the potential influence of the different signal paths between L1 and L2 was neglected. Regarding this aspect, this Ph.D. dissertation shows that is not a problem for inversion at ionospheric heights. An alternative to inverting the profile, which overcomes this disadvantage, is to use the bending angle of the signal as the main input data. The implementation of separability when using the bending angle is not immediate and was, actually, one of the goals of this thesis. In this sense, the separability approach has been applied to measured L1 bending angle, instead of LI combination as reported in previous work. Additionally, this approach could also be translated to tropospheric profile retrievals. Several approaches to account for the upper ionospheric contribution have been also tackled, apart from the fact of neglecting such contribution: a climatological model, an exponential extrapolation and condisering the nature of the separability concept. it has been proposed a way to obtain mapping functions derived from RO profiles. Such mapping functions can be easily derived from usual ionospheric parameters. For the contribution of this part of the ionosphere, it has been shown that it is capable to account for the total electron content (TEC). However, by working solely with RO derived data, we are systematically neglecting the contribution of the protonosphere to the total electron content. With the initial proposed mapping function based on the analysis of effective heights derived from RO, only the ionospheric contribution is accounted for. The ideal solution for ground-based GNSS data applications would be to use a two-layer model, one to model the ionosphere and another one for the protonosphere, or alternatively, if we are looking for high tomographic resolution, to combine RO and topside LEO observations with ground data. It has been shown that by modelling in such way, the results that were obtained with RO data analysis can be validated. The most important conclusion is that the ratio between ionospheric and protonospheric contribution is the driver for the location of the effective heights.

  • Cenit 2010: prometeo. Tecnologías para el combate integral de incendios forestales

     Sanz Subirana, Jaime; Juan Zornoza, Jose Miguel; Gonzalez Casado, Guillermo; Garcia Rigo, Alberto; Rovira Garcia, Adrià; Aragon Angel, Maria Angeles; Salazar Hernández, Dagoberto José; Hernandez Pajares, Manuel
    Participation in a competitive project

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