Descripteur
Documents disponibles dans cette catégorie (193)
Ajouter le résultat dans votre panier
Visionner les documents numériques
Affiner la recherche Interroger des sources externes
Etendre la recherche sur niveau(x) vers le bas
Fast precise GPS positioning in the presence of ionospheric delays / Dennis Odijk (2002)
Titre : Fast precise GPS positioning in the presence of ionospheric delays Type de document : Monographie Auteurs : Dennis Odijk, Auteur Editeur : Delft : Netherlands Geodetic Commission NGC Année de publication : 2002 Collection : Netherlands Geodetic Commission Publications on Geodesy, ISSN 0165-1706 num. 52 Importance : 242 p. Format : 16 x 24 cm ISBN/ISSN/EAN : 978-90-6132-278-8 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] ambiguïté entière
[Termes IGN] correction ionosphérique
[Termes IGN] correction troposphérique
[Termes IGN] données GPS
[Termes IGN] interpolation
[Termes IGN] krigeage
[Termes IGN] mesurage de phase
[Termes IGN] méthode des moindres carrés
[Termes IGN] modèle de Gauss-Markov
[Termes IGN] modèle ionosphérique
[Termes IGN] modèle stochastique
[Termes IGN] propagation ionosphérique
[Termes IGN] propagation troposphérique
[Termes IGN] réfraction atmosphérique
[Termes IGN] résolution d'ambiguïté
[Termes IGN] signal GPS
[Termes IGN] station virtuelle
[Termes IGN] traitement de données GNSS
[Termes IGN] traitement du signalIndex. décimale : 30.61 Systèmes de Positionnement par Satellites du GNSS Résumé : (Auteur) This thesis deals about geodetic applications of the Global Positioning System (GPS), in which the position of the GPS receiver must be determined with cm precision. This requires a relative measurement setup, together with an advanced processing strategy based on observations of the carrierphase of the signal. To keep it economically interesting, this CPS technique should be based on relatively short time spans in which the satellite observations are collected. The key to precise positioning using short time spans is to take advantage of the integer property of the ambiguities of the phase observations in the processing.
The above procedure has been applied in a successful way for the last decade to applications in which the distance between the receivers is restricted to about 10 km (the socalled rapidstatic and realtime kinematic GPS techniques over short distances). Above this distance, it is known that certain errors in the GPS observations start to significantly bias the computed receiver position when they are not taken care of. The aim of this research therefore is to develop a processing procedure, taking into account the errors in GPS observations due to propagation of the signals through the ionosphere, the atmospheric layer above about 80 kill. Although other errors (due to troposphere and satellite orbit) are of relevance as well, the research is restricted to an improved modelling of the ionospheric error. since it is by far the largest error. For the other errors standard modelling techniques are applied in this research. Using the procedure, it should be possible to determine the desired receiver positions with cmprecision using a short tinle span. The research is restricted to GPS receivers with a mutual distance of a few hundred km (mediumdistance baselines), located in midlatitude regions.
To facilitate a modelling of the ionospheric error, using the theor ' y of atmospheric refraction it is possible to decompose this error into a firstorder effect, which contains the gross of the error, plus some higherorder effects and a term due to bending of the signal path. Under worstcase conditions. the firstorder term may range up to about 80 m (on the GPS L2 frequency), whereas the accumulated effect of higherorder and bending terms can be tip to 4 cm (for L2). For the future L5 frequency (from 2008) these effects are even larger. Fortunately, because of the relative setup and the assumed medium distances, it is proved for this research it is allowed to neglect the higherorder and bending errors.
In the procedure a stochastic modelling of the firstorder ionospheric errors (referred to as ionospheric delays) is chosen. This means that the ionospheric delays are not modelled as completely unknown parameters, but that stochastic prior information is incorporated by means of ionospheric pseudoobservations. This model is referred to as the ionosphereweighted model: The weight of the ionospheric information can be tuned by the a priori standard deviation of the pseudoobservations. When this standard deviation is chosen zero, the ionosphereweighted model reduces to the ionospherefixed model, which is the usual processing model for shortdistance baselines (for which the ionospheric delays may be neglected). On the other hand, with an infinitely large ionospheric standard deviation, the model will be equivalent to the ionospherefloat model, in which the ionospheric delays are assumed as completely unknown parameters. This latter model is closely related to the ionospherefree combination, for which it is known that it cannot be used to achieve fast positioning results. It is shown that the ionosphereweighted model is only suitable for fast ambiguity resolution (and consequently positioning), when the ionospheric standard deviation is small. This requires very precise a priori ionospheric information.
The developed procedure consists of three steps. It is required that a user collects CPS observations in the vicinity of a network of permanent GPS stations. In the first step, the observations at the network stations are processed simultaneously using the ionosphereweighted model. Since in this research the goal is precise positioning within the shortest time span possible, i.e. instantaneous or singleepoch positioning, it is required that the network data is also processed instantaneously. To make instantaneous resolution of the network ambiguities possible, the sample values of the ionospheric pseudoobservations are temporal predictions based on estimates of previous epochs. Test computations using a network with a station spacing of more than 100 km demonstrated that in this way high network ambiguity success rates (close to 100%) can be obtained. In the second step, precise ambiguityfixed network ionospheric delays are spatially interpolated at the approximate location of the user's receiver. In the procedure for this purpose the concept of virtual reference station (VRS) observations is used. In this concept the network estimates (ionospheric delays and other parameters) are transformed to VRS observations. which should correspond to the data a real receiver would have collected at the user's location. The processing of the user's observations relative to this VRS is the third step of the procedure. Because of the presence of possible residual ionospheric delays also in this step the ionosphereweighted model is applied. The difference with the application in the network processing is that the sample values of the pseudoobservations are now taken zero. and the ionospheric standard deviation is computed as a function of the distance to the closest real network station. Using this, test computations demonstrated that instantaneous ambiguity success rates of 90% are feasible. When the ionospherefixed model would be applied, the success rates would not be higher than about 60%.Numéro de notice : 13101 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54884 Réservation
Réserver ce documentExemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 13101-01 30.61 Livre Centre de documentation Géodésie Disponible Analysis of refraction influences in geodesy using image processing and turbulence models / Philipp Flach (2001)
Titre : Analysis of refraction influences in geodesy using image processing and turbulence models Type de document : Thèse/HDR Auteurs : Philipp Flach, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2001 Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 63 Importance : 175 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-05-5 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie
[Termes IGN] analyse spectrale
[Termes IGN] détecteur à transfert de charge
[Termes IGN] filtre de Wiener
[Termes IGN] instrument de géodésie
[Termes IGN] instrumentation Leica
[Termes IGN] méthode des moindres carrés
[Termes IGN] modèle atmosphérique
[Termes IGN] réfraction atmosphérique
[Termes IGN] spectre électromagnétique
[Termes IGN] traitement d'image
[Termes IGN] turbulence
[Termes IGN] variance
[Termes IGN] vidéothéodoliteIndex. décimale : 30.03 Instruments de géodésie Résumé : (Auteur) The propagation path of light in the atmosphere is influenced by inhomogeneities of the refractive index. These refraction effects deteriorate the accuracy of the direction and distance measurements in geodetic applications. As illustrated by two examples in this report, the refraction effects cannot be accurately corrected up to now and, therefore, solutions must be provided which can be implemented into geodetic instruments. The presented approach is based on the determination of the temperature gradient being the decisive influential parameter for angular refraction effects.
In the atmosphere, temperature gradients are related to turbulent thermal exchange processes such as the turbulent sensible heat flux. In order to describe atmospheric turbulence, the applied statistical approach uses the method of spectral analysis which states that the atmospheric turbulent velocity field can be thought to consist of many eddies of different densities. This energy spectrum of turbulence can be modelled using the structure constant of refractive index CJ and the inner scale 10 of turbulence. If these two structure parameters are measured, the temperature gradient is derived from dimensionless profile functions using the so-called Monin-Obukhov similarity description. Hereby, the fact should be kept in mind, that the Monin-Obukhov similarity description and the energy spectrum of turbulence are only valid for vertical temperature gradient profiles in the atmospheric boundary layer.
This research work investigates the determination of the required structure parameter Cn and lo by means of image sensors which can be built into geodetic instruments. To derive the structure parameters CJ and 10 from the acquired image data, the application of appropriate image processing techniques is examined. The evaluation concept is based on angle-of-arrival fluctuations and intensity fluctuations. Angle-of-arrival fluctuations are perceived as high-frequency motions of image patterns grabbed by the sensor, and intensity fluctuations are related to the temporal variation of the gray values of the pixels. As presented in this report, these two effects of optical turbulence can be used to determine the structure parameter Cn and lo. For this purpose, image processing techniques must parameterize both angle-of-arrival fluctuations and intensity fluctuations. Within this research work, the angle-of-arrival fluctuations are modelled by the variance óx characterizing the shifting of image patterns which are located using edge detection algorithms. The intensity fluctuations are modelled by the variance óx characterizing the temporal intensity spectrum of the incoming light beam. In the scope of this research work, the variance óx is provided using digital filter techniques such as the Wiener filter or least-squares template matching.
In order to validate this concept, the video theodolite Leica TM3000V and a digital line scan camera Basler L120 are used as two different imaging systems to acquire image data during various practical field experiments. These field experiments revealed a partial good agreement between the structure parameter CJ and lo obtained by the image sensors and the ones obtained by a reference system (scintillometer). Basically, the method presented here is appropriate to reduce the refraction influence. A decisive advantage of this method is based on the fact that additional sensors are not necessary (except for the image sensors which are built into the instrument). However, as the exemplary comparison of temperature gradients shows at the end of the report, further research work in the scope of the atmospheric boundary layer is still necessary.Numéro de notice : 13062 Affiliation des auteurs : non IGN Autre URL associée : http://dx.doi.org/10.3929/ethz-a-004045114 Thématique : POSITIONNEMENT Nature : Thèse étrangère DOI : 10.3929/ethz-a-004045114 En ligne : https://www.sgc.ethz.ch/sgc-volumes/sgk-63.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54863 Réservation
Réserver ce documentExemplaires(2)
Code-barres Cote Support Localisation Section Disponibilité 13062-01 30.03 Livre Centre de documentation En réserve M-103 Disponible 13062-02 30.03 Livre Centre de documentation En réserve M-103 Disponible Development of a dispersometer for the implementation into geodetic high-accuracy direction measurement systems / Burkhard Böckem (2001)
Titre : Development of a dispersometer for the implementation into geodetic high-accuracy direction measurement systems Type de document : Thèse/HDR Auteurs : Burkhard Böckem, Auteur Editeur : Zurich : Institut für Geodäsie und Photogrammetrie IGP - ETH Année de publication : 2001 Collection : IGP Mitteilungen, ISSN 0252-9335 num. 73 Importance : 140 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-906467-33-7 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie
[Termes IGN] effet atmosphérique
[Termes IGN] émetteur
[Termes IGN] impulsion laser
[Termes IGN] mesurage électronique d'angles
[Termes IGN] mesurage électronique de distances
[Termes IGN] propagation du signal
[Termes IGN] rayonnement électromagnétique
[Termes IGN] récepteur bifréquence
[Termes IGN] réfraction atmosphérique
[Termes IGN] téléscopeIndex. décimale : 30.03 Instruments de géodésie Résumé : (Auteur) In the course of the progressive developments of sophisticated geodetic systems which offer a very high accuracy potential strategies for correcting atmosphere-related effects will become increasingly important. These atmosphere-related effects arise in a large span of time scales: systematic deviations caused by a quasi-stationary refractive index gradient environment, generally referred to as refraction in geodetic context, slowly transfer to stochastic deviations resulting from optical turbulence. Refraction corrected optical direction and angle measurements are required in numerous high-accuracy measurement applications. These applications include surveying tasks in connection with civil engineering projects, the alignment of particle accelerator facilities, surveying tasks in context within assembling processes in industrial environments, e.g. aircraft industry, tasks wherein surveying instruments provide the spatial guidance of large machines, etc. A dispersometer, based on the dual-wavelength method by utilizing atmospheric dispersion, constitutes a metrological solution to atmosphere-related effects. Another decisive advantage of a dispersometer is that the envisaged correction of atmosphere-related effects works integrally and is available in real time. The aim of this thesis was to develop this dispersometer to overcome atmospherically induced limitations in very high-accuracy direction and angle measurements. The dispersometer consists of two modules: the dual-wavelength transmitter and the detection system being composed of the dispersion telescope and a position sensitive detector. By applying the dual-wavelength method, the major .challenges in instrumental realization are the generation of coaxial single-mode emission at two spectrally optimized wavelengths and the achievement of optical position sensing accuracy in the order of a few nanometers. The development of the dispersometer is principally made possible by focussing on three key technologies: dual-wavelength generation by frequency conversion, optical fiber technology, and gap- technology. Within this work detailed studies of these three key technologies are performed. In this work it is demonstrated that a dual-wavelength laser by frequency conversion is clearly suited for the implementation in the dual-wavelength transmitter. Furthermore, a novel technique for achieving coaxial single-mode propagation at two spectrally wide-separated wavelengths by one single-mode fiber is established within this thesis. Due to the application of optical fiber technology it is now possible to couple both beams into one optical channel of a modem geodetic total station. In order to achieve optical position sensing with the accuracy of a few nanometers by using a short-focal-length receiving telescope, gap-technology by utilizing special segmented position sensitive detectors is applied. This thesis contains a complete treatment addressed to this technology. Within the course of dispersometer performance tests, difference position sensing accuracy of ó = 7.3 nm was achieved. Additionally, the existence of the position sensitive detector inherent dispersion was demonstrated. In combination with the dispersion of the receiving optics, the position sensitive detector inherent dispersion has to be considered for the measurement of the atmospheric dispersion induced displacement between both beams of different wavelengths. As a solution a self-calibration procedure which corrects the dispersion of the complete detection system is described. This self-calibration procedure which utilizes the impact of optical turbulence possesses the decisive advantages that it obviates the need of additional measurements and the dispersion correction can be computed and applied in real time. A substantial part of this thesis is devoted to dispersometer measurements. Two basic atmospheric conditions which are typical for industrial measurement tasks indoors were simulated. Additionally, a detailed study of the influence of the aperture diameter on the dispersometer measurements was performed. The optimal aperture diameter for the present instrumental layout and for the prevailing ambient conditions was 30 mm. For theodolite-like and smaller apertures it is confirmed that the accuracy of the refraction angle improves with the square root of the integration time. Due to dispersometer performance by using theodolite-like and possibly smaller apertures in combination with the self-calibration procedure, the implementation of a standard theodolite-telescope is proposed. In a moderately turbulent atmosphere the accuracy of the refraction angle for single- face telescope observation was found to be 0.2 µrad (0.01 mgon) after an integration time of 12 sand a sight length of 17 m. Summarizing the theoretical investigations, the key technologies involved in the instrumental development, and the experimental results, presented in this dissertation, it can be concluded that the realized dispersometer in combination with a theodolite is capable of the refraction corrected angular measurements, the influences of optical turbulence notwithstanding. The application of optical fiber technology and the envisaged implementation of a standard theodolite-telescope confirm the presumption that the realized dispersometer can be implemented into modem geodetic total stations. Improvements with respect to field-operativeness are expected by an industrial realization of the dispersometer and by implementing the dispersometer into modem geodetic total stations. The integration of blue laser diodes, when meeting the standards of nowadays infrared laser diodes, would significantly enhance efficiency and reduce overall costs. Due to the technologies presented within this thesis such an integration is clearly feasible. Numéro de notice : 14740 Affiliation des auteurs : non IGN Autre URL associée : http://dx.doi.org/10.3929/ethz-a-004176211 Thématique : POSITIONNEMENT Nature : Thèse étrangère DOI : 10.3929/ethz-a-004176211 En ligne : http://e-collection.library.ethz.ch/eserv/eth:24109/eth-24109-02.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62684 Réservation
Réserver ce documentExemplaires(1)
Code-barres Cote Support Localisation Section Disponibilité 14740-01 30.03 Livre Centre de documentation En réserve M-103 Disponible Entwicklung eines Meßsystems zur automatischen Erfassung differentieller Punktverschiebungen im Objektraum / J.J. Prenting (2000)
Titre : Entwicklung eines Meßsystems zur automatischen Erfassung differentieller Punktverschiebungen im Objektraum Titre original : On the development of a measuring system for automatic monitoring of differential object displacement Type de document : Thèse/HDR Auteurs : J.J. Prenting, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 2000 Collection : DGK - C Sous-collection : Dissertationen num. 514 Importance : 114 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-9552-6 Note générale : Bibliographie Langues : Allemand (ger) Descripteur : [Vedettes matières IGN] Photogrammétrie terrestre
[Termes IGN] alignement
[Termes IGN] chambre DTC
[Termes IGN] déformation d'édifice
[Termes IGN] orientation du capteur
[Termes IGN] photogrammétrie métrologique
[Termes IGN] réfraction
[Termes IGN] surveillance d'ouvrageIndex. décimale : 33.70 Photogrammétrie terrestre Numéro de notice : 53558 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Thèse étrangère Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=59504 Réservation
Réserver ce documentExemplaires(2)
Code-barres Cote Support Localisation Section Disponibilité 53558-02 33.70 Livre Centre de documentation Photogrammétrie - Lasergrammétrie Disponible 53558-01 33.70 Livre Centre de documentation Photogrammétrie - Lasergrammétrie Disponible Modeling and validating orbits and clocks using the Global Positioning System / Tim A. Springer (2000)
Titre : Modeling and validating orbits and clocks using the Global Positioning System Type de document : Monographie Auteurs : Tim A. Springer, Auteur Editeur : Zurich : Schweizerischen Geodatischen Kommission / Commission Géodésique Suisse Année de publication : 2000 Collection : Geodätisch-Geophysikalische Arbeiten in der Schweiz, ISSN 0257-1722 num. 60 Importance : 154 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-908440-02-4 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] analyse comparative
[Termes IGN] élément orbital
[Termes IGN] étalonnage des données
[Termes IGN] orbitographie
[Termes IGN] réfraction atmosphérique
[Termes IGN] satellite GPS
[Termes IGN] télémétrie laser sur satellite
[Termes IGN] traitement de données GNSSIndex. décimale : 30.61 Systèmes de Positionnement par Satellites du GNSS Résumé : (Editeur) [préface] Cet ouvrage traite des applications globales du GPS. Les thèmes présentés sont : 1) l'analyse d'observations GPS "zéro différences"; 2) la combinaison d'observations au laser (SLR) et par le GPS ; 3) le développement de meilleurs modèles d'orbites. Les signaux du GPS sont retardés par l'ionosphère et la troposphère. La plupart de la réfraction ionosphérique peut être éliminée aisément en se servant d'une combinaison linéaire spéciale des signaux L1 et L2, tandis que la réfraction troposphérique impose l'emploi de modèles raffinés avec de nombreux paramètres libres, ce qui introduit des incertitudes. En outre, une observation de phase indique la distance entre satellite et récepteur seulement à un nombre entier de longueurs d'onde près. Par contre, les mesures de distance par laser (SLR) n'ont pas d'ambiguités et sont corrigées beaucoup plus facilement pour les effets de l'atmosphère. Pour cette raison, des observations SLR sont très importantes pour calibrer le système micro-ondes GPS. Numéro de notice : 13060 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie En ligne : https://www.sgc.ethz.ch/sgc-volumes/sgk-60.pdf Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=54861 Réservation
Réserver ce documentExemplaires(2)
Code-barres Cote Support Localisation Section Disponibilité 13060-02 30.61 Livre Centre de documentation Géodésie Disponible 13060-01 30.61 Livre Centre de documentation Géodésie Disponible Reflecting telescope optics, 1. Vol 1 / R.N. Wilson (2000)PermalinkReflecting telescope optics, 2. Vol 2 / R.N. Wilson (2000)PermalinkAstronomie / A. Acker (1999)PermalinkMesure de déplacement en ouvrage d'art / P. Slisse (1999)PermalinkModeling the neutral-atmospheric propagation delay in radiometric space techniques / Virgilio de Brito Mendes (1999)PermalinkLa thermographie infrarouge / G. Gaussorgues (1999)PermalinkLasermessungen nach Erdsatelliten auf zwei Wellenlängen unter Verwendung einer Streak-Kamera / S. Riepl (1998)PermalinkMehrdimensionale Interpolation von Meteorologischen Feldern zur Berechnung der Brechungsbedingungen in der Geodäsie / Hans Arnold Hirter (1998)PermalinkZum Einfluss inhomogener Brechungsindexfelder auf die Verschwenkung offener Polygonzüge am Beispiel des Tunnelvortriebs / Maria Hennes (1998)PermalinkAstrophysique / Pierre Léna (1996)PermalinkEtude du comportement du contenu électronique total et de ses irrégularités dans une région de latitude moyenne / René Warnant (1996)PermalinkUntersuchungen zu hochpräzisen kinematischen DGPS-Echtzeitverfahren mit besonderer Berücksichtigung atmosphärischer Fehlereinflüsse / H. Blomenhofer (1996)PermalinkAmbiguity resolution techniques in geodetic and geodynamic applications of the Global Positioning System / L. Mervart (1995)PermalinkEntwicklung eines Meßsystems zur Ermittlung von Turbulenzparametern der Atmosphäre für Anwendungen in der Geodäsie / Maria Hennes (1995)PermalinkLa réfraction au Piton de la fournaise / P. Charnotet (1995)PermalinkPermalinkCours de physique générale à l'usage de l'enseignement supérieur scientifique et technique / Georges Bruhat (1992)PermalinkPermalinkProceedings of the symposium refraction of transatmospheric signals in geodesy / J.C. DE Munck (1992)PermalinkEphemeridenrechnung und Bahnbestimmung geostationärer Satelliten mit Hilfe der Taylorreihenintegration / Oliver Montenbruck (1991)Permalink