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Sub-cm subsidence measurements with the Wide-angle Airborne Laser ranging system / Olivier Bock in Surveys in Geophysics, vol 22 n° 5-6 (September 2001)
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Titre : Sub-cm subsidence measurements with the Wide-angle Airborne Laser ranging system Type de document : Article/Communication Auteurs : Olivier Bock , Auteur ; Christian Thom
, Auteur
Année de publication : 2001 Article en page(s) : pp 537 - 548 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Lasergrammétrie
[Termes IGN] coin réflecteur
[Termes IGN] effondrement de terrain
[Termes IGN] GPS-INS
[Termes IGN] lasergrammétrie
[Termes IGN] photodiode
[Termes IGN] précision centimétrique
[Termes IGN] précision millimétrique
[Termes IGN] rapport signal sur bruit
[Termes IGN] simulation numérique
[Termes IGN] subsidence
[Termes IGN] télémétrie laser aéroportéRésumé : (Auteur) The Wide-Angle Airborne Laser Ranging System (WA-ALRS) is an instrument developed at IGN with the aim of measuring land subsidence with sub-cm accuracy. The instrument provides range measurements that are used to estimate the co-ordinates of a ground-based network of cube-corner retroreflectors (CCRs). Millimeter accuracy on relative radial co-ordinates has been demonstrated in a ground-based experiment and centimeter accuracy has been obtained in a recent airborne experiment. The main limitation in the latter experiment came from the low link budget at longer distances. In this paper, we analyze the performance expected with two different detector modules (avalanche photodiodes with amplifiers). Laboratory measurements are used to characterize detector parameters and estimate ranging accuracy. Numerical simulations predict a 2-3 mm accuracy in the vertical co-ordinate with these detectors combined to a 2-km aircraft altitude, a 20 laser beam divergence, a 250-m CCR separation and ~ 103 measurements per CCR. Numéro de notice : A2001-180 Affiliation des auteurs : LOEMI+Ext (1985-2011) Thématique : IMAGERIE Nature : Article DOI : 10.1023/A:1015632604527 Date de publication en ligne : 30/03/2001 En ligne : http://doi.org/10.1023/A:1015632604527 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=34464
in Surveys in Geophysics > vol 22 n° 5-6 (September 2001) . - pp 537 - 548[article]Analyse en séries temporelles de variables relatives au mouvement du pôle et à la rotation de la Terre / A.C. Chapsal (2001)
Titre : Analyse en séries temporelles de variables relatives au mouvement du pôle et à la rotation de la Terre Type de document : Mémoire Auteurs : A.C. Chapsal, Auteur Editeur : Paris : Institut Géographique National - IGN (1940-2007) Année de publication : 2001 Collection : Publications du LAREG Sous-collection : Mémoire de stage Importance : 81 p. Format : 21 x 30 cm Note générale : Bibliographie
Mémoire de DEA de statistiques de l'Université de Rennes et ENSAILangues : Français (fre) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] bruit blanc
[Termes IGN] densité spectrale de puissance
[Termes IGN] mouvement du pôle
[Termes IGN] rotation de la Terre
[Termes IGN] série temporelle
[Termes IGN] traitement du signalIndex. décimale : DEA Divers DEA et quelques masters actuels de recherche Résumé : (Auteur) Analyse des résidus obtenue par moindres carrés sur les variables relatives à la rotation de la terre et à la partie du pôle par une approche temporelle d'identification de processus ARMA et une approche fréquentielle. Numéro de notice : 68951 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Mémoire DEA divers Organisme de stage : Lareg (IGN) Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=53738 Réservation
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Code-barres Cote Support Localisation Section Disponibilité 68951-01 DEA Livre Centre de documentation En réserve Mezzanine Disponible Analysis of refraction influences in geodesy using image processing and turbulence models / Philipp Flach (2001)
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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
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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)
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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
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Code-barres Cote Support Localisation Section Disponibilité 14740-01 30.03 Livre Centre de documentation En réserve M-103 Disponible Evaluation of "Mitch" hurricane damages in central America using satellite imagery / P. Romeijn (2001)
Titre : Evaluation of "Mitch" hurricane damages in central America using satellite imagery Type de document : Article/Communication Auteurs : P. Romeijn, Auteur ; F. Yakam Simen, Auteur ; E. Nezry, Auteur ; I. Supit, Auteur Editeur : Lisse et Amsterdam : Balkema (August Aimé) Année de publication : 2001 Conférence : EARSeL 2001, 21st international symposium, Observing our environment from space : news solutions for a new millennium 14/05/2001 16/05/2001 Paris France Importance : pp 125 - 131 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de télédétection
[Termes IGN] chatoiement
[Termes IGN] dommage matériel
[Termes IGN] filtre de déchatoiement
[Termes IGN] Honduras
[Termes IGN] image panchromatique
[Termes IGN] image radar
[Termes IGN] image SPOT
[Termes IGN] Nicaragua
[Termes IGN] radar à antenne synthétique
[Termes IGN] risque naturel
[Termes IGN] Salvador
[Termes IGN] tempêteRésumé : (Auteur) The states of Honduras, Nicaragua, and EI Salvador have been toughly hit by the "Mitch" hurricane in the first days of November 1998. The extent of damages due to this hurricane, as well as their impact upon local economy were exceptional. In this framework, a remote sensing project was immediately initiated to provide a large scale evaluation of the damages suffered by the three countries. To reach this objective, new remote sensing products called TmDYNAMICRADAR and TmIDYNAMICOPTICAL products have been designed. These products are, based on using, either radar satellite images, or optical/radar satellite data fusion. The most efficient techniques have been applied to produce these products, thus enabling change detection at a very fine spatial scale (from 20 meters x 20 meters to 10 meters x 10 meters). Project schedule and operations, as well as the validation of its products are reported in this article. Numéro de notice : C2001-028 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Communication DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=64936 Evaluation d'un système de positionnement d'un véhicule sur route basé sur la fusion de données / E. Helou Helo (2001)
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